Importance of Blue Carbon in Mitigating Climate Change and Plastic/Microplastic Pollution and Promoting Circular Economy
Blue carbon has made significant contributions to climate change adaptation and mitigation while assisting in achieving co-benefits such as aquaculture development and coastal restoration, winning international recognition. Climate change mitigation and co-benefits from blue carbon ecosystems are highlighted in the recent Intergovernmental Panel on Climate Change Special Report on Ocean and Cryosphere in a Changing Climate. Its diverse nature has resulted in unprecedented collaboration across disciplines, with conservationists, academics, and politicians working together to achieve common goals such as climate change mitigation and adaptation, which need proper policy regulations, funding, and multi-prong and multi-dimensional strategies to deal with. An overview of blue carbon habitats such as seagrass beds, mangrove forests, and salt marshes, the critical role of blue carbon ecosystems in mitigating plastic/micro-plastic pollution, as well as the utilization of the above-mentioned blue carbon resources for biofuel production, are critically presented in this research. It also highlights the concerns about blue carbon habitats. Identifying and addressing these issues might help preserve and enhance the ocean’s ability to store carbon and combat climate change and mitigate plastic/micro-plastic pollution. Checking out their role in carbon sequestration and how they act as the major carbon sinks of the world are integral parts of this study. In light of the global frameworks for blue carbon and the inclusion of microalgae in blue carbon, blue carbon ecosystems must be protected and restored as part of carbon stock conservation efforts and the mitigation of plastic/micro-plastic pollution. When compared to the ecosystem services offered by terrestrial ecosystems, the ecosystem services provided by coastal ecosystems, such as the sequestration of carbon, the production of biofuels, and the remediation of pollution, among other things, are enormous. The primary purpose of this research is to bring awareness to the extensive range of beneficial effects that can be traced back to ecosystems found in coastal environments.
Introduction
Blue carbon was established as a metaphor to highlight that, apart from terrestrial ecosystems, coastal ecosystems also contribute significantly to carbon sequestration [1]. Apart from being recognized as a helpful carbon sink, blue carbon ecosystems provide various other services, including shelter for different migratory birds, fishes, and crabs [2,3]. It is also vital in minimizing net carbon emissions. But various lines of evidence, including remote sensing data and other studies about land use land cover (LULC), depict the drastic reduction of mangrove ecosystems in different coastal areas environments. In 2003, the first carbon storage global budget highlighted the planetary significance of mangroves and salt marshes as carbon sinks. In 2005, it was revealed that fifty percent of all marine carbon sequestered comes from seagrasses, mangroves, and tidal marshes [2]. Threats from natural and human activities are responsible for destroying these productive ecosystems, thereby reducing their capability to absorb and store carbon [4]. A surge in the sea level, natural and human-made disasters, and large-scale coastal development are responsible for the Rapid change in the blue carbon landscapes [5]. The Holocene’s glacial and interglacial eras have caused the mean sea level to fluctuate by up to 120 m [6]. Therefore, urgent research is needed at the international and national levels to preserve and restore the blue carbon ecosystems and tackle climate change [2].
The critical role of “Blue Carbon” in tackling climate change has become increasingly understood in recent years. To date, initiatives have helped achieve co-benefits such as aquaculture and coastal conservation, thus gaining international prominence. Beyond the scientific community, blue carbon has captivated awareness among various stakeholder groups, including government and non-governmental bodies responsible for protecting marine environments and mitigating climate change [7]. Indeed, blue carbon not only plays an important role in mitigating climate change but also could be used as a potential biomass source for biofuel production. As depicted in Figure 1, blue carbon could play a role as a critical intermediate in the circular process of CO2.
The research related to blue carbon received impetus after UNEP’s report ‘Blue Carbon: A Rapid response assessment’ in 2009 which focused on the importance of marine and coastal areas [1]. Soon after the report, the blue carbon initiative was established in 2010. Blue carbon science is evolving fast, accelerated through scalable and reproducible observations, but is yet to achieve its maturity. Therefore, there should be proper policy regulations and funding options to avail the maximum possible benefits from these blue carbon ecosystems, showing that there should be multi-prong and multi-dimensional strategies for the protection and conservation of such ecosystems. In this paper, the role of blue carbon in the ecosystems, in mitigating plastic/micro-plastic pollution, as well as the utilization of blue carbon for biofuel production are scrutinized. Indeed, the blue carbon discussion has a long way to go but needs harmonious collaboration from various stakeholders to build a positive future and help reduce carbon emissions, amongst many other benefits. This review broadens the conversation on the importance of blue carbon in climate change mitigation efforts by underlining the difficulties in measuring, valuing, managing, and governing carbon in the coastal, open ocean, and deep-sea ecosystems. In the section under “Role of Blue Carbon ecosystems in mitigation of microplastic pollution,” we especially report how important coastal ecosystems are in dealing with plastic pollution. We conclude with the potential of coastal ecosystems in biofuel production which is one of the pathways to developing sustainable economies. The importance of coastal ecosystems has increased as a result of the degradation of terrestrial ecosystems brought about by human activities such as land use change, deforestation, fossil fuel consumption, etc. The ecosystem services provided by coastal ecosystems, such as carbon sequestration, biofuel production, pollution remediation, and so on, are immense in comparison to those provided by terrestrial ecosystems. The primary objective of this study was to draw attention to the wide variety of positive outcomes that can be attributed to coastal ecosystems.
Spatiotemporal Distribution of Blue Carbon Ecosystems
Coastal vegetated habitats including salt marshes, seagrasses, and mangroves have long provided humans with advantages. recently, notwithstanding data limitations, their importance as carbon reserves has been recognized in climate change mitigation [1,8]. As illustrated in Figure 2, spatiotemporal distribution and the importance of blue carbon ecosystems in controlling climate change can be seen [9].
Coastal zone environments, including seagrass beds, rocky reefs and corals, intertidal marshes, sandy beaches, kelp forests, and mangrove forests [10], help combat climate change by effectively storing and sequestering CO2, known as “coastal Blue Carbon” [11]. Salt marshes, seagrasses, and mangroves, for example, often form a spatially connected continuum of intertidal ecosystems. Unvegetated mudflats and sandbars are ecosystems that contain and sequester vast quantities of organic carbon [12,13]. Blue carbon soil is anaerobic, mainly in contrast to the terrestrial ground, which causes carbon stored in these soils to decay at a slow rate, and thus the carbon accumulates for hundreds to thousands of years [14,15]. The coastal wetland vegetation acts as a buffer zone between land and oceans, capable of storing surplus water during the rainy season and preventing floods [16]. They also help to protect coastlines and are considered to be more cost-effective than complicated structures such as seawalls and levees, as they are cheaper to manage and will be able to keep up with rising sea levels [17,18]. They also exhibit high burial rates leading to the seafloor’s rise, acting as a barrier against rising sea levels and wave actions linked with climate change [19]. They serve as a motivator for ecosystem-based adaptation to protect humans, infrastructure, and property from the negative impacts of climate change [20].
Mangroves occur in tropical and sub-tropical regions [21]. They are found in 118 countries worldwide, with 15 countries accounting for 75% of their overall coverage. West Africa is home to nearly a quarter of the world’s mangroves, containing almost 0.854 billion metric tons of carbon in below-ground and above-ground biomass [22]. Similarly, Indonesia alone accounts for 23% [23]. But a considerable loss of 0.16–0.39% per year has been recorded in the mangroves since 2000 [24]. Mangroves have an excellent ability to store carbon in the root system and act as carbon-rich forests in the tropics; hence their management and conservation need to be prioritized [25]. Geological evidence indicates the adaptation of mangroves to earlier climate and sea-level change [26,27]. They play a crucial role in promoting sedimentation in sensitive coastal regions, hence withstanding climate-induced impacts such as rising sea levels [28]. Their wide variety of aerial root structures such as pneumatophores, prop roots, plank roots, and knee roots help prevent soil erosion and differ in their efficacy to reserve sediments [29]. over, mangroves speed up land development through a rise in sedimentation, lower wave exposure, and peat formation, consequently mitigating exposure to tropical storm surges and sea-level rise [30].
Seagrasses are another blue carbon ecosystem found mainly in shallow coastal margins across zero latitudes. Seagrasses use photosynthesis to take in carbon dioxide and assimilate it into their biomass. The above-ground/water vegetation traps suspended particulate matter (sedimentation) that later adds to the sedimentary storage component [31]. They have colossal mitigation potential for neutralizing CO2 emissions, which leads to improvements in carbon estimates stored in seagrass sediments and incorporate seagrass ecosystems [32,33]. The total global area under seagrass ranges from 300,000–600,000 km 2 [34]. However, there has been a sharp decrease in recent decades, with a sevenfold decline reported from 1990 to 2009 [35]. Globally, seagrasses are declining by 2–5% each year as 30,000 Km 2 of seagrass have been destroyed in recent decades [36]. Every year, organic carbon oxidation in degraded seagrass meadows potentially releases 0.03–0.33 petagrams of carbon dioxide back into the atmosphere [37]. Seagrasses cover 4.8 million hectares in West Africa, holding an estimated 673 million tons of carbon [22]. In coastal waters, the restoration of seagrasses has led to increased sequestration of blue carbon [38]. However, they have a poor carbon storage capacity compared to mangroves.
Unlike seagrasses and mangroves, salt marshes differ in having low methane emissions [39,40]. Salt marshes cover 1.2 million hectares in West Africa, holding 303 million metric tons of CO2 [22]. In recent studies, an area of 45,000 Km 2 has been reported for salt marshes [41]. Apart from carbon sinks, they are prodigious inorganic carbon sources of coastal oceans [42]. Tidal marshes, mapped only in 43 countries of the world, represent 14% of the global coastal area [43]. The minimum yearly global loss rate of tidal marshes is 1–2% [44]. Although the blue carbon ecosystems have proved their ability as ideal carbon sinks, both natural and artificial threats destroy these ecosystems. Due to the rise in sea level, marshes sink to stress and shrink with time [45]. Further, marine accidents, such as massive oil spills, are also responsible for the damage to these ecosystems [46,47,48]. Hence, to avail the maximum benefits of these ecosystems, proper policymaking and guiding mechanisms should be established to preserve and manage these blue carbon ecosystems.
Other coastal ecosystems such as barrier islands, dunes, and beaches made of sand, play a pivotal role in dispersing wave energy, besides having vital sediment reserves that aid in preserving coastlines, and to a certain extent, in adapting to rising sea levels [49,50]. It is debatable if coral reefs are the sinks or sources of atmospheric CO2 [51]. However, they make remarkable structures, ranging from deep oceans to their surfaces and parallel to coastlines in many places extending up to several kilometres, in such a way that they form a significant part of the coastal defense. The mass flow of energy from overlying waters into the coral systems significantly reduces wave activity—a vital function of reef roughness [52,53]. However, as per Pendleton et al. [37], enormous reserves of carbon sequestered in the past are affected by the transformation of these coastal ecosystems, as blue carbon present in the sediments is released into the atmosphere when these ecosystems are degraded [37]. As a result, the value of blue carbon habitats in sequestering organic carbon has boosted conservation efforts as a means to reduce climate change and offset CO2 emissions [54]. Furthermore, their contribution to strengthening coastal resilience to weather disasters and changing climate has led to their participation in many countries’ nationwide defined commitments (NDCs) for climate change adaptation and mitigation [55,56].
Role of Blue Carbon Ecosystems
3.1. Role of Blue Carbon Ecosystems in Mitigation of Climate Change
In recent years, the use of fossil fuels for industrial and agricultural activities and transportation means have resulted in high pollutant emissions such as CO2, NOx, and PM, causing the serious consequences of environmental pollution and climate change [57,58,59,60,61], proof of which could be seen from the COVID-19 pandemic [62,63,64]. Due to this reason, seeking efficient and useful solutions relating to technology, management, and policy is very important [65,66,67,68,69]. Among these, shifting to renewables is considered one of the most potential approaches in mitigating environmental pollution and climate change since renewables are available, have biodegradation, and have non-toxic properties [70,71,72,73]. Indeed, the popular renewable sources are wind, solar, ocean, hydropower, biomass, and biofuels, which have all been used the most in recent years [74,75,76,77,78,79,80,81,82,83]. Besides, the development of the natural ecosystems is also considered an extremely important solution because the natural ecosystems could keep a large amount of carbon emissions [84].
Being a natural ecosystem, blue carbon has accrued global consideration for its potential role in mitigating carbon dioxide emissions, as shown in Figure 3 [85]. However, its contribution is restricted worldwide because it is limited to coastlines [86]. Coastal environments have been found to store tremendous amounts of carbon in sediments, multiple times more than numerous types of temperate and tropical forests [87]. Carbon sequestration via vegetated coastal ecosystems helps to reduce anthropogenic CO2 emissions. However, their adequacy contrasts with the spatial scale of evaluating the “Blue Carbon” ecosystem provider. It is a powerful management tool for maintaining environmental wellbeing and productivity by offering enhanced assurance, protection, preservation, and services [88]. Because of the high carbon reserves and sequestration rates and the high assessment of their other ecological resources, coastal blue carbon habitats have been positioned as one of the best ocean-based solutions for climate change mitigation. Mangrove trees, seagrass meadows, and salt swamps are examples of coastal vegetated environments that have long benefited human populations and ecosystems. recently, their role in storing large volumes of carbon and therefore contributing to tackling climate change has been well recognized [1,8]. The UN Sustainable Development Goals (SDGs) have been agreed upon as the global priorities through to 2030 by countries worldwide. Amongst the 17 SDGs are goals that are directly relevant to tackling climate change (SDG 13) and protecting and sustaining the use of coasts, oceans, and aquatic resources (SDG 14). Mangrove restoration would contribute to SDG 13 (strengthening resistance and resilient potential of all nations to climate-related threats and catastrophic events). It also contributes towards SDG 14 (sustainably maintaining and ensuring marine and seaside ecosystems to avoid crucial unfavorable effects, including enhancing their intensity and pushing toward their reclamation to accommodate climate change by 2020). [89]. Climate change threatens mangroves, causing an additional 10–15% loss by 2100 [90].
Blue carbon systems help tackle climate change by storing and sequestering carbon; however, these ecosystems are susceptible to global warming, resulting in uncertainty about their long-term effectiveness [56]. Sea-level rise, droughts, intensified hurricanes, changes in temperature regimes, precipitation levels, and coastal heatwaves threaten the blue carbon environment and its carbon reserves. The vulnerability of climatic stressors on the blue carbon ecosystem depends on the exposure of such systems to disturbances, which is a function of the sensitivity and resilience of these ecosystems. over, it also depends on the stressor’s frequency and intensity [91]. The increase in sea level has been a big challenge to coastal habitats. Still, there is regional and temporal variability in its rate [56]. For example, climate-induced storms and rising sea levels can affect mangroves by exposing previously buried organic carbon to oxidation, further increasing CO2 concentrations in the atmosphere [92] and acting as a positive feedback loop contributing to global warming. Mangroves and salt marshes’ ability to sequester carbon can be improved or preserved by sustaining an altitude above sea level in the wake of the sea-level rise [93]. They can, however, be eroded or submerged if there is insufficient sediment or root growth to sustain altitude [3]. Further, sea-level rise can slow the decay rate of organic matter, which may increase the carbon storage potential of intertidal sediments. Mangroves are also found to migrate landward (to adjust to climate change) where the sea-level escalation outpaces sediment deposits [94,95]. During accelerating sea-level rise, salt marsh ecosystems restructure occurs, increasing the resilience and thus carbon storage [96]. Mudd et al. [97] detected that the rate of carbon accumulation in salt marshes in South Carolina rose with a sea-level increase until it reached a critical speed, flooding the swamp vegetation and stopping carbon accumulation [3]. Increased inundation due to rising sea levels changes salt marshes and mangroves [98]. Under certain conditions, some of the salt marshes are proposed to be entirely covered by mangroves by the end of the century [99,100].
3.2. Blue Carbon Ecosystems as Carbon Sequestration and Sinks
Coastal habitats are critical carbon sinks that store almost half of all organic carbon [56,101]. Sediments of blue carbon ecosystems store vast carbon stocks [102,103]. Most of the CO2 from the atmosphere, taken through photosynthesis, is recompensed to the air through the respiration of microbes and plants or stored short-term in plant foliage. In contrast, the rest is stored for a prolonged period in woody biomass and soil. Depending on the vegetation type, 50–90 percent of all coastal wetland carbon is found in the ground [37,104]. The high photosynthetic strength and gradual decomposition of these ecosystems result in higher production and carbon sequestration per unit area [105,106]. Because of their tremendous productivity, they can sequester significantly more carbon than terrestrial ecosystems [3,106]. In vegetated coastal ecosystems, primary development usually is higher than respiration [2,107], enhancing their ability to produce surplus organic carbon and thus function as carbon sinks [19]. A dynamic space-time transition between carbon flows and stocks is required for blue carbon conversion, absorption, and conservation in coastal zones [106]. It includes interactions between land, sea, plants, animals, and microbes, as shown in Figure 4.
Despite their importance as carbon sinks, there is concern that in some situations, they could be source of methane emissions, which could contribute to global warming [108,109]. However, evidence shows that methane emissions from marine wetland habitats are marginal, relative to the amount of carbon sequestered [110,111]. On average, carbon stock in the uppermost meter of the soil of saltmarshes and seagrass meadows is nearly equal to that of the top 1 m soil of terrestrial forests. In comparison, the organic carbon stored by the top 1 m of mangrove forests is thrice as contained in top terrestrial soil [19]. The rate of carbon burial in the sediments of these three ecosystems is relatively large. Coastal vegetated ecosystems contribute significantly to long-term carbon sequestration, a contribution equivalent to terrestrial ecosystem carbon sinks, despite covering a smaller area than inland forests [3].
Mangrove ecosystems make up 30% of all coastal ecosystems’ carbon burial and 5% of the net primary production of carbon, even though they cover just 1.9% of the tropical and subtropical coasts [26,112]. Mangroves sequester 174 gCm −2 yr −1 on average, and the global mean burial amount of mangrove soil carbon is 24 TgCyr −1 (10–15 percent of sediment carbon storage) [113]. According to a study of mangroves in desert inlets off the coast of Baja California, carbon sequestration in mangroves is most likely in the form of organic peat and soil [114,115]. It revealed nearly 2000 years of carbon storage in organic soils and below-ground carbon content of 1130 metric tonnes per hectare [115].
Salt marshes are one of the world’s most active habitats (sequestering up to 3900 gCm −2 yr −1 ). On average, salt marsh soils store around 210 gCm −2 yr −1. converted to 770 g of CO2 m −2 yr −1 due to Rapid burial rates [116,117]. The world’s coastal salt marshes hold an estimated 437 to 1210 million tonnes of carbon in their trees and soil [91,115]. The top 50 cm of sediment in coastal salt marshes sequesters 430 Tg C globally. However, this is an exaggeration since most studies only look at the top meter of soil, even though organic-rich soil profiles extend several meters deep [104].
Although seagrass meadows cover less than 0.2% of the ocean’s surface, annual carbon sequestration of seagrass sediments accounts for 10–15% of total ocean carbon sequestration. It is also estimated that seagrass environments sequester carbon at around 21 times the rate of tropical rainforests (43 gCm 2 yr −1 ) [106,118]. Seagrass meadows are expected to store 27 and 40 TgCyr −1 in the short and long term, respectively [117,119]. Furthermore, global organic carbon accumulation in the sediments of seagrass habitats is up to 19.9 petagrams (Pg) (between 4.2 and 8.4 Pg if a more traditional approach is used) [33,102], with carbon storage lasting centuries or even millennia [33]. However, owing to the interaction of various biotic and abiotic causes, there is a significant variation in the C storage amounts fixed under seagrass beds [19,120]. Recent studies indicate that salt marshes, mangroves, and seagrasses have average carbon sink capabilities of 218 gCm −2 yr −1. 226 gCm −2 yr −1. and 138 gCm −2 yr −1. respectively, while terrestrial forests have just 5 gCm −2 yr −1 or less [3,106]. The lack of understanding about the fate of imported organic matter is to blame for the variance in estimates of coastal ecosystems’ overall susceptibility to climate change [121,122].
Macroalgae (or seaweed) is an extensive and the most productive vegetated coastal ecosystem. They grow on a hard substratum where no carbon accumulation occurs because they do not have a vascular root system and stockpile a huge quantity of carbon in their above-ground living biomass [123]. They are the source of the world’s highest carbon dioxide flux [124] and contribute significantly to the carbon sink of the world [107,125]. As they fail to absorb below-ground carbon relative to saltmarshes, seagrasses, and mangroves, macroalgae have been underestimated in the blue carbon domain. However, it has been stated that they play a significant role as “carbon donors”, that is, they donate carbon to the receiving habitats. They export macroalgal material to the deep sea and sediments as detritus [123], thus indirectly contributing to global carbon sequestration, an assumption recently validated by the study of Ortega et al. [126] which examined the metagenomes of macroalgae. Up to 14TgC yr −1 macroalgal carbon was found in coastal sediments and 152 TgC yr −1 in deep-sea; so, proposed was the inclusion of macroalgae in blue carbon assessments. Another study by Queiros et al. [124] validated the entry or presence of macroalgal detritus in deep coastal sediments using bulk isotope analysis and eDNA sequencing as complementary bio-tracing techniques. They found that the study area sequesters an average of 8.75 g (0.73 mol) of macroalgal carbon per m 2 of deep coastal sediment every year as particulate organic carbon. The study also highlighted the role of macroalgae in helping sea-bed species during the winter months when other food supplies are scarce in contributing to carbon sequestration. Several reports have been published regarding the microalgal carbon sequestration potential being buried in marine sediments or exported to the deep sea [123,127]. Kelp forests (Ecklonia Radiata) absorb 1.3–2.8 TgC per year, according to Dexter et al. [128], accounting for almost 30% of the total blue carbon stored and sequestered over the Great Southern Reef. Studies have also shown the presence of refractive carbon compounds [129], which may be the essential organic carbon reservoir in the oceans [130]. According to some findings, organic carbon extracted from macroalgae is buried alongside organic carbon derived from seagrass [131,132,133]. Although macroalgae (especially kelp organisms) contribute significantly to the carbon cycle along the coast, most species and regions still lack accurate carbon fixation estimates [134,135]. research into the methods and eventual disposal of this waste, as well as the significance of these ecosystems in the carbon cycle and as a potential source of blue carbon, is necessary [135]. Furthermore, detailed assessments of the macroalgal ecosystem’s global surface area are desperately required to extend the reach of carbon sequestration research from a local to a worldwide scale [136].
Temperature affects carbon accumulation in salt marshes, seagrass meadows, and mangroves because it impacts the metabolic cycles of carbon gain via photosynthesis and carbon loss via plant and microbial respiration [3]. A slight temperature rise improves efficiency, but higher temperatures induce stress, which decreases productivity and thus carbon storage. Temperature fluctuations affect productivity and, therefore, carbon storage [137]. Increasing sea temperature also impacts seagrass habitats and their ability to retain carbon. As a case in Australia depicts, a large amount of organic carbon storage loss from seagrass has recently been recorded after a period of rising sea temperature. Ocean heatwaves have emerged as a threat to coastal ecosystems and have resulted in seagrass meadows’ mortality. Arias-Ortiz et al. [138] estimated a substantial loss of seagrass carbon stocks (2–9) Tg CO2 over three years, following a heatwave in Shark Bay (Western Australia).
Another climate-induced factor is rainfall [139], increasing carbon stock below-ground in tropical Mangroves, as indicated by Sanders et al. [140]. This is because most of the carbon stored in mangrove forests is contained within soils, and an increase in rainfall leads to a decline in the decomposition of organic matter [141,142]. Climate change is amplified by anthropogenic disruptions, increasing the vulnerability of coastal ecosystems. For example, the coastal squeeze and submergence of the intertidal zone’s seaward edge due to rising sea levels has a big influence on coastal habitats and hence blue carbon stocks [143]. Similarly, the damming of rivers affects the sediment supply to the coastal wetlands, thus increasing the vulnerability of submergence and decreasing the tendency of sediment accretion and soil carbon accumulation [56]. Extreme weather seems to alter blue carbon supplies, but more research is needed to predict future effects. So, there is a considerable need to improve and understand how climate change affects blue carbon storage to scale up the ecological restoration, which further helps mitigate climate change.
3.3. Role of Blue Carbon Ecosystems in Mitigation of Microplastic Pollution
Plastic was widely produced and employed after 1950 owing to its properties such as high water resistance, low expenses, durability, flexibility, as well as lightness [144,145]. Significantly, in 2018, plastic generation reached 359 million tons globally [146,147,148] and Yang et al. [149] showed that its yield is increasing by 300 million tons every year. Plastic would not entirely disappear due to the impacts of typical environmental conditions (such as temperature or salinity), ultraviolet radiation, biological activity (namely aggregation, biofilm formation, and so on), and mechanical stress that was caused by the wave as well as the current action. However, plastic would be separated into smaller pieces, weathered, corroded, etc. [150,151,152]. This was found especially true for coastal wetlands that received plastic waste from not only terrestrial habitats near the rivers but also the ocean via currents [153]. It was noticed that plastic debris was highly retained in low-energy environments that had weak hydrodynamics [154,155,156], and then plastic debris was gradually degraded to form plastic fibers, fragments, or particles with less than 5 mm in size, so-called microplastics. Microplastics were produced in the marine environment through coastal fishing activity, which was driven by currents and winds from beaches [157], and transported by rivers, sewage from industrial zones, and effluents to the coastal areas, where sewage discharges, for instance, were a necessary source of fibers from washing activity [158,159]. The accumulation of microplastics in the ecosystem could cause harm to organisms by reducing individual growth, reproduction, and adaptability [160]. Furthermore, because the size of microplastics was small and their specific surface area was large, they frequently absorbed environmental contaminants such as organic pollutants or heavy metals [161,162], which severely threatened plant and animal growth. As a result, the detrimental effects mentioned above endangered the ecosystem and primary functions of coastal wetlands including flood defense [163,164] as well as carbon sequestration [165,166]. Hence, it was critical to prevent and control microplastic contamination. The blue carbon ecosystem could highly block and intercept microplastics, which provided significant benefits [167,168].
The majority of microplastics were less than 1 mm, which included sizes of less than 0.5 mm (13.7%), in the range of 0.5–1 mm (42.9%) and 1–2 mm (24.2%). In addition, a small portion of 2–3 mm (7.8%), 4–5 mm (6.4%), and 3–4 mm (5.0%) were also observed. Thus, the small size of microplastics could be due to the fact that the smaller size made them easier to be washed to the intertidal area by the tide [169]. Noticeably, compared to in mangroves, the number of microplastics less than 1 mm in saltmarshes was found significantly greater, which was associated with the saltmarsh sediments which had larger particle sizes as plastics could be easily broken into smaller fragments via coarser sediments’ abrasion during transportation [170,171]. Additionally, saltmarshes being closer to the sea in comparison with mangroves and being swept by more tidal kinetic power could also be the reason for smaller microplastics in saltmarshes [171, 172]. Interestingly, coastal sediments were thought to be primary sinks of marine microplastics [155,173,174]. Besides, significant microplastic stocks were frequently observed in vegetated coastal habitats with high rates of sedimentation, including mangroves, tidal marshes, and seagrasses [160,173,175]. In addition, the abundance and features of MPs in the aforementioned habitats frequently changed between places. As reported, the range of plastic abundances in mangroves was 0 to 11,256 items kg1 sediment, in seagrass was 0 to 1466, and in a tidal marsh, sediments were 22.7 to 296. The most frequently observed forms were fragments and fibers, in which polyethene and polypropylene were the most common polymers [173].
significantly, mangrove ecosystems were identified as important sinks for different contaminants from both marine and terrestrial activities because of the mangrove ecosystem’s unique properties (such as abundant organic carbon as well as high primary productivity), [176,177,178]. Indeed, mangroves were important blue carbon ecosystems that were found in the subtidal and intertidal areas, where they were subjected to microplastic contamination [179]. According to previous investigations, blue carbon ecosystems were capable of capturing microplastics and POCs from surface sediments [180,181]. It was obvious that mangroves could not only clean and retain contaminants generally, but they also acted as an ecological interception system for microplastics [160]. It was noted that mangrove plants could alter hydrological conditions as well as have an effect on the microplastic separation and distribution in various tidal areas. In particular, microplastics of varying sinking rates, sizes, and shapes might exhibit distinct distribution patterns in varying mangrove intertidal zones [182,183,184].
It was not hard to see that seagrasses were able to reduce water flow velocity, and at the same time increase particle retention and sedimentation [185,186,187]. Remarkably, seagrass meadows could trap particulate matter indicating that they could also be a considerable trap for microplastics. Notably, some microplastics were integrated into the epiphytic communities that were attached to seagrass blades, so not all reached the sediment [175,188,189]. When microplastics reached the seagrass ecosystem, the seagrass blades’ architectural complication as well as above-ground biomass reduced water currents, which made particulate matter, namely microplastics, get trapped among the blades and then they settled into the sediment underneath [155,190]. Besides epiphytes, known as small sessile plants including macroalgae, cyanobacteria, crustose coralline algae, diatoms that attached to seagrass blades created a rough substrate for microplastics to adhere to and be trapped. Once trapped, microplastics were overgrown with epiphytes, which kept them adhered to the blade surface, which led to an increase in the likelihood of microplastic uptake by herbivores and hence entering the food web [189]. noticeably, with an average of approximately two items per individual, the probability of microplastics recovery in shellfish was 46.3% and in fish was 47.2% in the Mediterranean [191]. Seagrasses were not only a direct source of food for a variety of herbivores, such as sea turtles and dugongs [192], but they were also a main nursery ground for fauna living near shore [193]. Goss et al. [189] and Datu et al. [188] discovered that several microplastics on seagrass blades were included within epiphyte assemblages. over, there also existed evidence showing the significant relation between microplastic abundances and epiphyte density, implying that the presence of more epiphytes on a blade and more microplastics had a direct correlation. On the other hand, several seagrass genera, such as Posidonia, were able to trap microplastics not only within their habitats but also within their exported ball-shaped wrack, implying the role of seagrasses in both trapping microplastics within their ecosystem and removing them from marine environments [194]. Furthermore, in situ research revealed a high level of plastic accumulation in seagrass ecosystems, existing both on seagrass blades and in sediment. Additionally, according to Huang et al. [179], seagrass ecosystem sediments were enriched with microplastics 1.3–17.6 times more than unvegetated sites, whereas an enrichment factor was found of up to 2.9 by Huang et al. [195]. over, Goss et al. [189] discovered 4.0 ± 2.1 microplastics in each tropical seagrass blade. importantly, seagrass meadows, one of the most crucial blue carbon ecosystems and wetlands, were considered important global carbon sinks that contributed to alleviating climate change around the world [196].
Blue Carbon as a Potential Source for Biofuel Production
The sustainability of the first-generation bio-based fuels (1G) was also called into doubt since their utilization threatened the traditional food supply, particularly in developing nations [197,198]. The second-generation biofuels (2G/cellulosic biofuels) which were derived from cellulosic energy crops including municipal solid wastes, lignocellulosic residues, or agro-industrial wastes, provided an alternative option because of their plentiful availability [199,200,201,202,203,204]. However, this type of fuel also coped with a lot of failures due to higher investment expenses and technical problems in down streaming. Furthermore, the generation of 1G/2G biofuels necessitated additional crop cultivation acreage, and hence they could not be viewed as a viable alternative to fossil fuels because the yield gained might not fulfil the global energy demand. In addition, the third-generation biofuels (3G/advanced biofuels) were made from aquatic biomass such as algae [205,206]. Algae gained a lot of interest among third-generation biofuels because of their low lignin concentration and high productivity, which reduced the consumption of energy throughout fuel generation [207,208]. over, blue carbon sources were biomasses that were morphologically and systematically more similar to plants on the ground than seaweeds [209]. Hence, exploiting blue carbon sources appeared to be an appealing solution for renewable energy generation, avoiding the significant drawbacks related to 1G and 2G bio-derived fuels. Indeed, the biofuel production pathway from blue carbon sources could be illustrated in Figure 5.
It could be seen from Figure 5 that transesterification, direct combustion, gasification, or pyrolysis were all methods for producing biofuel from dry blue carbon-based biomass [210,211,212,213]. Meanwhile, energy generation techniques from wet blue carbon-based biomass included enzyme hydrolysis, hydrothermal treatments, anaerobic digestion, and fermentation to biobutanol/bioethanol/biohydrogen [214,215,216,217]. It was noted that utilizing blue carbon-based biomass for biofuel generation was in the early stages of research and development. Besides, a lot of non-glucose-derived sugars such as cell wall polysaccharides and mannitol were accumulated in seaweed, but not so many glucose-originated polysaccharides [218]. As a result, industrial bioethanol synthesis from blue carbon-based biomass necessitated the fermentation of not only non-glucose but also glucose-based sugars [219]. For chemical compositions, the blue carbon sources and terrestrial plants differed substantially in general. For example, seaweeds have high water content (90% fresh wt), protein content (from 7 to 15% dry wt), carbohydrate content (25–50% dry wt), as well as low concentration of lipid (between 1 and 5% dry wt) in comparison with terrestrial biomass [220].
As reported, the lipid content in the blue carbon sources was low; however, their carbohydrate content was high, permitting them to be employed as a feedstock for the generation of different fermentative bio-base fuels [221]. Though fermentation facilities using macroalgae were known as relatively expensive to operate and build, they were dependable and provided large yields [222]. This is partly because of the high content of water (from 70 to 90%), the protein concentration of around 10%, and the presence of various amounts of carbohydrates [223]. Furthermore, because there was a small amount of lignin and hemicellulose in macroalgae cells, the enzymatic and chemical pretreatment stages in the production of biofuel were removed [224]. significantly, the carbohydrate concentration of macroalgae varied greatly depending on strains, species, and cultivars. In addition, because the potential growth speed and carbohydrate concentration of the green macroalgae Ulva lactuca were high, it was thought of as a promising aquatic energy crop [225]. Regarding brown macroalgae Laminaria spp., there could be up to 55% carbohydrates in it with dry weight, principally free sugars, cellulose, hemicellulose as well as the energy storage molecules mannitol and laminarin [226]. Indeed, biohydrogen generation from blue carbon received a lot of interest because of carbohydrate-rich blue carbon. In a study by Yukesh et al. [227], they improved the generation of biohydrogen from seagrass using new ozone-linked rotor-stator homogenization. In particular, rotor-stator homogenization required 510 kJ/kg TS of specific energy to accomplish 10.45% seagrass lysis while ozone-linked rotor-stator homogenization obtained 23.7% seagrass lysis with less energy (only 212.4 kJ/kg TS) input. It was noted that the ozone-coupled rotor-stator homogenization sample’s biohydrogen generation capability was evaluated and compared with using biohydrogenesis.
The generation of biogas was considered a long-time technology. Interestingly, there were multiple operational biogas systems, ranging from large-scale to small-scale and they were supplied by a variety of feedstocks such as animal wastes, agricultural products, certain residential rubbish, and sewage sludge [228,229]. Additionally, because macroalgae contained more water than terrestrial biomass (ranging between 80 and 85%), they were more suited for microbial conversion instead of thermochemical conversion [230,231]. Indeed, producing biogas from macroalgae was more technically feasible than generating biogas from other fuels because all organic components in macroalgae (such as protein, carbohydrates, and so on) could be transformed into biogas via anaerobic digestion [232,233]. Besides, a low lignocellulose concentration of macroalgae facilitated biodegradation more than that of their relative microalgae to create considerable amounts of biogas [234,235]. However, microalgae could be cultivated using pollutant water and CO2 [236,237] and could be used to synthesize many types of biofuels such as bioethanol, biodiesel, and bio-oil [238,239,240,241].
Many works successfully established the practical usefulness of seaweed as a feedstock for the anaerobic digestion process. For example, the generation of biogas from marine wrack might reduce GHG emissions while also bringing economic benefits to local island people. Apart from that, Marquez et al. [242] discovered biogas generation by employing three different microbial seeds including marine sediment, marine wrack-related microflora, and manure of cow. Accordingly, the authors discovered that the average biogas generated was 1223 mL from marine wrack-related microflora, 2172 mL from marine sediment, and 551 mL from the manure of cow. Although the methane potential at 396.9 mL CH4/g volatile solid was calculated using marine wrack proximate values in comparison with other feedstock, this parameter was low when the greatest methane yield of 94.33 mL CH4/g volatile solid was considered. Interestingly, among the microbial seeds tested, sediment in the marine platform was found to be the most effective source of microorganisms in terms of using seawater and marine wrack biomass to produce biogas. Nonetheless, sand deposition in salinity and digesters might cause trouble in the long-term anaerobic digestion process [243,244]. As observed, several factors, including growing method, species type, harvesting time, and seaweed production per hectare all made a great contribution to the anaerobic digestion process. It was noted that the balance of material and energy, harvesting biomass cost, carbon balance, as well as expenses of creating biogas from seaweed were not evaluated [245,246]. As reported, methane yields in biogas produced from the anaerobic digestion process of blue carbon sources could be changed with biochemical composition and they were linked to ash concentration and the degree of sugars stored [234]. Therefore, to increase methane yields, Banu et al. [247] used disperser-tenside (polysorbate 80) disintegration so as to improve the biomethanation ability of seagrass (namely Syringodium isoetifolium). Indeed, dispersion-assisted tenside disintegration had a more significant influence on bio-acidification as well as biomethanation assays in terms of methane production (0.256 g/g COD) and volatile fatty acid content (1100 mg/L) when compared to dispersion disintegration, which was 0.198 g/g COD; 800 mg/L. As a result, S. isoetifolium was seen as a potential substrate for achieving third-generation biofuel targets in the foreseeable future.
Apart from that, marine algae, which contained a high concentration of hydrolyzable carbohydrates, cellulose, glucan, and galactan, might serve as a possible feedstock to produce liquid biofuels [248]. As reported, two popular liquid transportation biofuels are synthetic biodiesel, bioethanol, and biobutanol using marine macroalgae feedstock. In comparison with edible as well as lignocellulosic biomass sources, marine macroalgae biomass was gaining popularity as a renewable feedstock to produce bioethanol [234,249]. As mentioned above, macroalgae possessed a high carbohydrate concentration and low lignin [250], making them appropriate for use as a substrate in the fermentation process to generate bioethanol after hydrolysis. The current techniques for bioethanol synthesis from seaweed were separate hydrolysis and fermentation, and simultaneous saccharification and fermentation, as illustrated in Figure 6 [220,251,252]. As for separate hydrolysis and fermentation, seaweed biomass was hydrolyzed before being fermented in discrete units using yeast or bacteria [218,253]. Regarding simultaneous saccharification and fermentation, however, both fermentation and hydrolysis occurred concurrently in a single stage [254,255].
Even though experiments on bioethanol generation from macroalgae were scarce, it was not hard to determine that using marine macroalgae waste for bio-derived fuel feedstock could lead to less rivalry for biofuels among food [221,256]. According to several investigations, the findings of using seagrass biowaste for bioethanol production appeared to be promising in terms of making this a reality [257,258,259]. In an investigation by Mahmoud et al. [260], they employed seven samples of beach-cast seagrasses (associated with Z. marina. S. filiforme. Z. noltii. P. australis. T. testudinum. and P. oceanic ) gathered from maritime environments worldwide with carbohydrate concentration ranging between 73% and 81% (w/dry weight of biomass). With no pretreatment, enzymatic hydrolysis with a single step was designed to effectively extract the monomeric sugars present in biomass originating from seagrass. In shake flasks, P. oceanica hydrolysate was observed to produce higher lipid yields (at 6.8 g/L) in comparison with the synthetic minimum medium (just 5.1 g /L). Additionally, it was then used as the only fermentation medium for oleaginous yeast T. oleaginous under the technical scale with the use of a fed-batch bioreactor, yielding 224.5 g /L lipids (0.35 g /L.h). Furthermore, the proportion of sugar/lipid conversion ( w / w ) was seen to be 0.41. According to cumulative statistics, roughly 4 million tons of microbial oils might be created by harvesting just half of the beach-cast seagrass in the world. Besides, Ravikumar et al. [257] presented their research on manufacturing bioethanol from seagrass biowastes with the use of Saccharomyces cerevisiae. The greatest bioethanol generation (0.047 mL/g) was observed in fresh seagrass leaves under acid pretreatment. As a result, fresh seagrass leaves might be one of the appropriate substrates for bioethanol synthesis. Furthermore, an investigation by Uchida et al. [261] studied the seagrass seeds (Zostera marina) bioethanol fermentation. On a dry weight basis, there were 83.5% carbs in the seeds, which included 48.1% crude starch. This parameter was equivalent to that of cereals such as corn and wheat flour. As reported, the saccharification of seeds went smoothly with no heating pretreatment, which showed that the starch present in seagrass seeds possessed a molecular form being ready to be digested by glucoamylase. Besides, the authors proposed that it might be possible to develop alcoholic drinks and foods from seagrass seeds, resulting in the creation of a unique marine fermentation sector in the future. The treatment of Laminaria japonica. Gelidium amansii. Ulva fasciata. Ulva lactuca. and Sargassum fulvellum biomass with acid and hydrolytic enzymes resulted in hydrolyzates with distinct proportions of mannose, glucose, mannitol, galactose, and other sugars [262]. As reported, Laminaria japonica hydrolyzate produced 0.4 g bioethanol for each gram of carbohydrate in case hydrolytic enzymes were utilized [263]. In another study, Adams et al. [264] investigated the generation of ethanol through laminarin polysaccharide yeast fermentation from the brown macroalga Saccharina latissimi using a variety of pretreatments. Meanwhile, in an experiment by Wi et al. [248], fermentation pretreatments were researched for a red microalgae species (namely Ceylon moss) with a high carbohydrate concentration (normally 23% galactose and 20% glucose). Accordingly, they proved that pretreatment approaches could be utilized to broaden the range of macroalga species appropriate for bioethanol generation. over, Ge et al. [265] investigated the utilization of floating residual wastes from the industry of alginate from Laminaria japonica (a brown alga) to generate bioethanol after they were pretreated with diluted sulphuric acid as well as experienced enzymatic hydrolysis. Likewise, Horn et al. [266] showed the ability of fermented extracts of Laminaria hyporbea to synthesize ethanol with the employment of Pichia angophorea (yeast), while El-Sayed et al. [267] assessed the utilization of reducing sugars from U. lactuca to produce bioethanol via Saccharomyces cerevisiae.
In the case of biobutanol, there existed just a few studies that researched the manufacture of biobutanol from macroalgae. In other words, macroalgae, especially brown algae, and their potential for biochemical transformation to butanol and other solvents by Clostridium spp. via acetone-butanol fermentation were not studied. However, the brown macroalgae biomass’s acetone butanol fermentation feasibility via C. acetobutylicum was proved, and the results showed that the butanol content in the hydrolysate reached around 0.26 g butanol/g sugar while 0.29 g butanol/g sugar was obtained in the pilot investigation [268,269]. In addition, HMF was regarded as among the chemical platforms that have the most potential for the conversion of industrially important bio-originated chemical compounds. According to several researchers, a greater starch concentration was accumulated in seagrass seeds [270,271]. over, several studies showed that raw biomass sources rich in non-structural carbohydrates, such as sucrose, fructose, starch, and glucose were employed as biomaterials for HMF generation [272,273]. Furthermore, by utilizing beach-cast seagrasses without feedstock expenses, seagrass feedstocks might contribute to sustainably and cost-effectively manufacturing HMF, which showed that seagrass biomasses were considered the most attractive source of bio-based feedstock to produce HMF sustainably.
Macroalgae were used to produce biogas and bioethanol instead of biodiesel since they lacked triglycerides. Typically, macroalgae were transformed into bio-derived oils such as free fatty acids and lipids, and more importantly, the lipids were separated to generate bio-based diesel. Even though free fatty acids were a precursor to biodiesel, the excessive quantity of free fatty acids in the oil might stymie the intended transformation. In an experiment, Tamilarasan [274] esterified the free fatty acids in Enteromorpha compressa algal oil from 6.3% to 0.34%, and subsequently, two stages for biodiesel synthesis were developed. notably, Xu [275] recently tried to use macroalgae as a carbon source for oleaginous yeast aiming to create bio-based diesel, and the maximal lipid concentration was observed to reach 48.30%. In contrast, the by-product-free fatty acids accompanying mannitol could be utilized to cultivate the oleaginous yeast. Also, several innovative approaches, such as ultrasonic irradiation, were employed to support transesterification through the formation of fine emulsions between alcohol and oil, and the rate of reaction was enhanced due to cavitation [274]. Furthermore, biodiesel output from wet biomass achieved was nearly 10 times lower compared to that obtained from dry biomass, suggesting that water had a detrimental influence on transesterification experiments, and hence the dehydration process was required to attain high efficiency [276]. over, Saengsawang et al. [277] investigated whether Rhizoclonium sp. oil could be employed as a biodiesel alternative to optimize the reaction conditions required for the process of chemical transesterification. The biodiesel weight of 0.174 ± 0.034 g along with 82.2% of the whole FAME was produced during the transesterification procedure from macroalgae oil. Besides, this research indicated that biodiesel produced from Rhizoclonium might be utilized as an alternative fuel, and more research would make it appropriate for large-scale manufacturing.
Thermochemical techniques are also considered potential solutions for converting biomass sources into biofuels [278,279,280]. Indeed, pyrolysis was the most used technique for extracting bio-oil [230, 281]. Pyrolytic cracking could quickly transform dried seaweed biomass into bio-originated oil and solid residue. Furthermore, investigations on the behaviors of pyrolysis and product properties of some macroalgae, such as brown algae, green algae, and red algae [238,282], revealed that the macroalgae’s pyrolysis process to produce biofuels and that of terrestrial plants were alike [283,284], even though the macroalgae had higher activation energy than that of terrestrial biomass [285]. Importantly, pyrolysis of macroalgae operating under 500 °C was shown to be a favorable temperature for maximizing bio-oil output [254,286]. Liquefaction was seen as a process where biomass experienced complex thermochemical reactions in a solvent solution, resulting in mostly liquid products. Remarkably, hydrothermal liquefaction mostly neglected macroalgae in the role of a feedstock for bio-originated oil since microalgae were assumed to have a greater lipid concentration intrinsically [287,288]. Elliott et al. [289] reported on the hydrothermal liquefaction of Macrocystis sp. with the employment of a batch reactor that was fed with 10% kelp dry mass in water. According to the oil product’s solvent separation, an oil yield of 19.2 wt% was observed. Utilizing Na2CO3 as a catalyst, Zhou et al. [290] investigated the hydrothermal liquefaction of the green marine macroalgae named Enteromorpha prolifera and got a maximal bio-oil output of 23.0% dw as well as an energy density of 29.89 MJ/kg. In another study, Neveux et al. [291] used hydrothermal liquefaction in a batch reactor to convert six types of freshwater and marine green macroalgae into bio-crude. The findings showed that the high ash concentration of macroalgae caused poorer bio-oil yields when compared to the results achieved from hydrothermal liquefaction of a variety of microalgae (in the range of 26–57% dw) [292]. Although the gasification of biomass on a wide scale was successfully demonstrated, it was still comparatively costly in contrast to fossil-fuel energy [293,294]. Indeed, gasification was able to generate hydrogen and syngas at a competitive price in the market. Actually, several nations had very few pilot gasification factories, more widespread industrial penetration appeared to be dependent on integration into the chain of biofuel from seaweed [295]. Table 1 compared and showed the benefits and drawbacks of several biofuel generation methods from blue carbon sources.
Global Blue Carbon Framework for Climate Change Mitigation
The blue carbon systems enhance climate mitigation strategies as these ecosystems store carbon for the long term. The same is recognized in global agreements on climate change such as the “United Nations Framework Convention on Climate Change” and “Kyoto Protocol”. It helps countries hit pollution reduction goals and comply with the Paris Agreement’s Nationally Appropriate Contributions [301]. Clean development mechanisms are being established to finance the blue carbon initiative at the local level. It was also included in the 2017 Sixth Climate Change Assessment Report by the IPCC.
The international blue carbon initiative is the world’s first coordinated global program, launched jointly by the Intergovernmental Oceanographic Commission of UNESCO, Conservation International, and the IUCN to combat climate change by protecting and restoring the ocean. The initiative is coordinating two working groups, the International Blue Carbon Scientific Working Group and the International Blue Carbon Policy Working Gropu. International standards for blue carbon monitoring and measurement, data collection and quality control, field survey guides, blue carbon preservation strategies, and management recommendations have been established by the International Blue Carbon Scientific Working Group. The International Blue Carbon Policy Working Group is committed to incorporating blue carbon projects into the UNFCCC and the CBD. It formulates financial support, and other policy programs and guides needed for research, projects, and policy priorities.
Nationally Determined Contributions (NDCs) for climate change mitigation and adaptation have included blue carbon ecosystems because of their role in increasing coastal vulnerability to climate change and weather catastrophes. The benefits of ecosystem flood management are also significant, with mangroves being anticipated to offer yearly flood protection worth US 65bn, saving 15 million people from flood risk. Mangroves, seagrasses, and saltmarsh inside the Coral Triangles are exceptionally delicate to rising sea levels and are likewise being menaced by climate change. For example, changes such as coastal ecosystem pulverization by clearing, infilling, siltation from upland catchment aggravations, and contamination from industry and metropolitan improvement, destabilize these significant ecosystems along the coast. The disruption of diverse processes at multiple geographical and temporal scales occurs as a result of climate change in blue carbon ecosystems and associated sedimentary carbon deposits. Changes in exposure, affectability and adaptation potential make blue carbon vulnerable to changing climate. Sea level rise is affecting carbon-rich silt deposits, as can be seen in the current state and growth of these stocks. Ocean level rise predictions on beachside regions are the most advanced of our insights for assessing the effects of blue carbon on climate change [56]. Changes in the environment have a direct impact on the unique blue carbon ecosystems, which are threatened by plant and soil destruction and reduced enlistment. Recently, the blue carbon initiative provided guidelines for incorporating blue carbon into NDCs. These recommendations offer technical advice for integrating these habitats into the revised NDCs in several ways, thus assisting countries in encouraging and maintaining the climate benefits of blue carbon ecosystems.
A deltaic blue carbon frangibility, such as that seen on sea islands and atolls, may also suffer from rising sea levels and increased wave heights. When carbon in vegetation and sediments is disrupted and mineralized to carbon dioxide, the global depletion of coastal habitats causes significant carbon dioxide discharges. The potential of the surviving ecosystems to mitigate climate change and offer other environmental functions has been weakened due to their degradation. Blue carbon habitats and programs aimed at protecting them, on the other hand, are yet to be included in regulatory instruments aimed at combating climate change [302]. Owing to the dramatic changes in coastal growth and mismanagement of coastal habitats, coastal areas are being destroyed at a critical pace all over the world due to acidification, currents, anoxia, precipitation, rising sea level, storm frequency, and other changes in the environment [87].
Even though blue carbon is being more widely discussed, actual efforts and complete adoption of the actions and proposed policy proposals are still uncommon. Many nations are yet to develop and adopt climate and carbon policies specific to coastal carbon ecosystems [55]. Coastal blue carbon habitats, on the other hand, have been included in several pioneering mitigation initiatives [15,55].
Conclusions
The deterioration of coastal ecosystems can be attributed to the hazards caused by both natural events and human activities. However, it has been found that blue carbon is essential in the fight against climate change and in reducing the pollution caused by plastic and microplastics. Additionally, it helps in achieving co-benefits such as developments in aquaculture and coastal restoration, which has earned it international recognition. In addition, coastal vegetation systems such as sea grass meadows, coastal marshes, and mangroves are among the most important carbon sinks on a worldwide scale. Their ability to store organic carbon is comparable to that of forests found on land, and depending on the type of plant present, between 50 and 90% of all of the carbon in coastal wetland ecosystems is located in the soil. In addition, coastal vegetation systems have the capacity to keep and store substantial amounts of plastic and microplastic, and they also have the potential to be used as feedstock for the generation of bioenergy. According to the findings of this study, it is possible for diverse ocean ecosystems to contribute to the promotion of climate mitigation measures and the conservation of carbon stock, to the contribution of the circular economy through the use of blue carbon in the production of bioenergy, and to the mitigation of plastic and microplastic pollution. In order for conservation initiatives to be a success, local residents need to be involved in the decision-making process. Involvement in these projects provides immediate benefits, such as meaningful work and consistent income. To integrate social protection with action on climate change and economic recovery, global coalitions that result in immediate initiatives are required. This is necessary in order to rebuild and transform economies from an ecological point of view. Based on the various studies conducted on coastal ecosystems, future projects may be more focused on the potential of biofuel production from the biomass that is produced by coastal ecosystems. This will help in fighting against the increasing levels of greenhouse gases and climate change at the global level. Furthermore, there is a need for global collective efforts from various economies for the conservation and protection of coastal ecosystems so that we keep on deriving various benefits from them.
Author Contributions
S.A.B.: conceptualization, methodology, writing—original draft; F.A.M.: writing—reviewing and editing; I.Q.: writing—reviewing and editing; H.M.-U.-D.: writing—reviewing and editing; A.K.B.: writing—reviewing and editing; A.A.: writing—reviewing and editing; S.A.W.: writing—reviewing and editing; R.B.: writing—reviewing and editing; T.H.T.: writing—reviewing and editing; N.D.K.P.: writing—reviewing and editing; D.N.C.: writing—reviewing and editing; S.F.A.: writing-reviewing, supervision. All authors have read and agreed to the published version of the manuscript.
Data Availability Statement
References
Figure 3. Role of blue carbon ecosystems in mitigation of climate change [85] (with permission from Elsevier using license number 5476621301963).
Figure 3. Role of blue carbon ecosystems in mitigation of climate change [85] (with permission from Elsevier using license number 5476621301963).
Table 1. Advantages and disadvantages of various processing techniques for converting blue carbon to biofuels [220,296,297,298,299,300].
Table 1. Advantages and disadvantages of various processing techniques for converting blue carbon to biofuels [220,296,297,298,299,300].
| Anaerobic digestion | Biogas | Finishing technology without drying process | High inhibition and salt |
| Fermentation | Bioethanol/biobutanol | High content of carbohydrate | Low efficiency in forming various mixed sugars |
| Transesterification | Biodiesel | No required the dewatering process | Low yield |
| Pyrolysis/Gasification/Liquefaction | Bio-oil, syngas, hydrogen, bio-char | Fast rate without required chemicals | High energy consumption |
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Bandh, S.A.; Malla, F.A.; Qayoom, I.; Mohi-Ud-Din, H.; Butt, A.K.; Altaf, A.; Wani, S.A.; Betts, R.; Truong, T.H.; Pham, N.D.K.; et al. Importance of Blue Carbon in Mitigating Climate Change and Plastic/Microplastic Pollution and Promoting Circular Economy. Sustainability 2023, 15, 2682. https://doi.org/10.3390/su15032682
Bandh SA, Malla FA, Qayoom I, Mohi-Ud-Din H, Butt AK, Altaf A, Wani SA, Betts R, Truong TH, Pham NDK, et al. Importance of Blue Carbon in Mitigating Climate Change and Plastic/Microplastic Pollution and Promoting Circular Economy. Sustainability. 2023; 15(3):2682. https://doi.org/10.3390/su15032682
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Bandh, Suhaib A., Fayaz A. Malla, Irteza Qayoom, Haika Mohi-Ud-Din, Aqsa Khursheed Butt, Aashia Altaf, Shahid A. Wani, Richard Betts, Thanh Hai Truong, Nguyen Dang Khoa Pham, and et al. 2023. Importance of Blue Carbon in Mitigating Climate Change and Plastic/Microplastic Pollution and Promoting Circular Economy Sustainability 15, no. 3: 2682. https://doi.org/10.3390/su15032682
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Factcheck: Is solar power a ‘threat’ to UK farmland?
The “threat” posed to UK farms by the expansion of solar power has emerged as a campaign issue for the final two candidates in the race to become the nation’s new prime minister.
Both Liz Truss and Rishi Sunak have warned of solar panels “filling” the UK’s highest quality farmland, joining a chorus of their fellow Conservative MPs who have recently described solar projects as hazards for rural communities and food supply.
There has been some pushback to the view being promoted by Truss and Sunak. For example, in the Times, chief reporter Sean O’Neill wrote that the pair are “displaying staggering ignorance” and “pandering to the whingeing nimbys in their tiny electorate”. In the Daily Telegraph, the paper’s chief city commentator Ben Marlow wrote that “Britain’s culture wars have reached such epically absurd proportions that even the sun is now the enemy”.
Despite the claims, ground-mounted solar panels currently cover just 0.1% of all land in the UK.
Even government plans to significantly scale up solar in line with its net-zero target are expected to bring this up to just 0.3% of the UK land area. This is the equivalent to around 0.5% of the land currently used for farming – and roughly half of the space taken up by golf courses.
In this factcheck, Carbon Brief assesses some of the statements made by UK politicians about solar power in recent months, how land is used in the UK and the concept of “agrivoltaics” – systems in which farmland is effectively combined with solar power.
Why are some UK politicians worried about solar power on farms?
Liz Truss, who is currently the firm favourite in the Conservative leadership race, told a husting in Exeter at the start of August:
“Our fields should be filled [with] our fantastic produce…[They] shouldn’t be full of solar panels, and I will change the rules. I will change the rules to make sure…we’re using our high value agricultural land for farming.”
“I think one of the most depressing sights when you’re driving through England is seeing fields that should be full of crops or livestock, full of solar panels,” says Liz Truss. piccom/yhOpD6y9Cw
— Adam Bienkov (@AdamBienkov) August 11, 2022
Two weeks later, Rishi Sunak wrote an article for the Daily Telegraph in which he seemed to be matching his opponent’s rhetoric, declaring:
“On my watch, we will not lose swathes of our best farmland to solar farms. Instead, we should be making sure that solar panels are installed on commercial buildings, on sheds and on properties.”
As Prime Minister, Rishi will fight for the interests of our farmers and protect our agricultural land
This idea, which was welcomed by climate-sceptic lobbyists, has not come out of nowhere. For months, backbench Conservative MPs have been speaking out against the number and size of new ground-mounted solar power projects being proposed, often citing local campaigns against projects in their constituencies.
Among them was Matt Hancock, the former health secretary and energy minister. In a Daily Mail article, he announced plans to stand in a supermarket car park with local campaigners to protest against a 2,500-acre solar farm in his constituency of West Suffolk.
Hancock used a common refrain, stating that “proposals for solar farms are often sited on high-grade agricultural land” and suggesting the FOCUS should be on rooftop solar instead. He also warned of the potential for fires resulting from battery storage units and said a local golf course was at risk.
According to the UK parliamentary record Hansard, a lot of the conversation about this issue in parliament took place at two key debates. In March, MPs discussed the construction of “large solar farms” and Brendan Clarke-Smith, Conservative MP for Bassetlaw, stated that “the threat to agricultural land is the crux of the problem”.
James Gray, Conservative MP for North Wiltshire, who secured the debate in June on “solar farms and battery storage”, told parliament:
“Right now, we have a gigantic number of applications in my constituency for solar farms – I know of at least four…They are turning a rural area into an industrialised centre, which is really unacceptable.”
He later raised the issue of Russia’s invasion of Ukraine and resulting pressure on food supplies, telling parliament that, “at a time like this, using good productive land in the UK for solar farms is disgraceful”.
Gray’s Комментарии и мнения владельцев are a continuation of historical Conservative anxieties around the construction of renewable energy in rural areas, which have previously led to a de-facto ban on the construction of new onshore wind – with considerable costs for the UK economy.
Despite the strength of feeling among some local campaign groups, the evidence suggests that most people in the UK, including 73% of Conservative party members, back these projects.
The government’s energy security strategy, published in April, contained various measures to deal with the UK’s energy crisis and achieve its net-zero targets, including a pledge to ramp up solar power capacity from 14 gigawatts (GW) to 70GW by 2035.
However, it also contained language that seemed to address Conservatives who were sceptical about ground-mounted solar, pledging to “consult on amending planning rules to strengthen policy in favour of development on non-protected land, while ensuring communities continue to have a say and environmental protections remain in place”.
Meanwhile, in Wales, the Labour climate minister Julie James issued a letter in March this year, saying that her department will prioritise the maintenance of high-quality farmland when considering solar projects. She wrote:
“Should solar PV array applications on BMV [best and most versatile] agricultural land come before the Department for Climate Change, the department will object to the loss of BMV agricultural land unless other significant material considerations outweigh the need to protect such land.”
How much land in the UK is used for solar power?
Solar farms in the UK currently have a combined capacity of around 14GW. According to analysis by the trade body Solar Energy UK, using Solar Media data, 9.6GW of this capacity comes from ground-mounted solar panels.
According to Solar Energy UK, for existing projects approximately six acres of land is required for every megawatt (MW) of power, which means that current ground-mounted solar covers an estimated 230 square kilometres (km2).
This makes up just under 0.1% of land in the UK.
In comparison, according to Corine Land Cover data, agricultural land covers 56% of the UK. Around 70,000km2 is pasture used for grazing cows and sheep, and around 67,000km2 is for growing cereals and legumes.
(It is worth noting that the more recent National Food Strategy, which uses the Corine Land Cover data alongside other sources, estimates that agricultural land covers 70% of the UK.)
As the chart below demonstrates, existing solar farms (dark yellow) currently use less land than golf courses (red) and airports (orange), which cover 1,256km2 and 493km2, respectively.
In April, the UK government released a new energy security strategy, which outlined plans to “look to increase” solar capacity “up to five times” by 2035. This would involve increasing ground-mounted solar capacity by an additional 38GW.
As solar technology becomes more efficient, it will require less space. ‘Bifacial’ panels, for example, capture sunlight on both sides of the panel.
The Department for Business, Energy and Industrial Strategy proposes that future solar power will need between two and four acres of land to produce 1MW of power. Assuming an average of three acres per 1MW, if the government meets its target of increasing solar capacity fivefold, ground-mounted solar could cover a total of almost 700km2 by 2035. This equates to nearly 0.3% of the UK’s land surface.
The yellow blocks in the chart below show the land cover of ground-mounted solar in 2022 (dark yellow) and the additional land cover of future solar under government plans to increase capacity five-fold (light yellow). The blue blocks show other types of land use in the UK.
Ground-mounted solar power is built on several types of land. However, even if all future ground-mounted solar was built on farmland, the impact on UK food production as a result of the change in land use would be small.
This can be illustrated with an idealised example where all of the 700km2 to meet the UK’s ground-mounted solar target replaces land used to grow wheat. On average in the UK, one hectare of land produces around eight tonnes of wheat in a year. This means that 700km2 – or 70,000 hectares – could, theoretically, be used to grow 560,000 tonnes of wheat per year. Based on 2021 data, this would account for just 4% of the UK’s annual wheat yield – even in this extreme example.
Are high-quality farmlands under threat?
Despite the very small areas of land involved, Conservative politicians have warned that the nation’s “high-value” and “best” agricultural land is under threat from development.
Rather than criticising renewable power, they have expressed concerns about planning regulations. Sunak has said he will “review planning rules to ensure that high-quality farmland is sufficiently protected…that large-scale solar farms cannot be built on [the] best and most versatile agricultural land”.
MPs have repeatedly mentioned the National Planning Policy Framework, which James Gray MP said should “discourage the use of agricultural land for solar farms rather than encourage it”. An update to the policy was set for July, but has been delayed.
Also up for revision is the National Policy Statement for Renewable Energy Infrastructure (EN-3), which governs the construction of large-scale (more than 50MW in England) solar projects. This document already advises against the use of best and most versatile cropland for solar power “where possible”.
However, it adds that “land type should not be a predominating factor in determining the suitability of the site location”. Roz Bulleid, deputy policy director at thinktank Green Alliance, tells Carbon Brief this kind of language “might be what’s targeted” by politicians.
Despite the rhetoric coming out of Westminster, many farmers – who are unlikely to volunteer their best land for solar power – are positive about this technology. Not least because fields with solar panels can still be used to produce food. (See: How can land be used for both solar and agriculture?)
Carbon Brief spoke to Tom Martin, who has proposed a solar scheme on his mixed farm in Cambridgeshire. The project would see around 65,000 solar panels sited on approximately 100 acres across three fields.
Martin describes the idea of adding solar panels to grassland while still grazing sheep as “win-win”:
“It’s not ‘produce 10 units of energy’ or ‘produce 10 units of food’. It could be six units of both. And then, all of a sudden, your two halves are greater than the whole.”
The selection of which fields to use for solar is down to a mix of factors, explains Martin. This includes, for example, the best way to connect the system to the grid, but also choosing the fields that generally produce lower yields.
In addition, his farm is always seeing a “fluid” rotation between grassland and arable use, Martin says, noting that “in the last 10 years, we have changed 200 acres from grass into arable”. So even with moving 100 acres back to grass for the solar panels, the farm will still be producing more cereals than it did a decade ago.
A spokesperson from the National Farmers Union (NFU), which represents tens of thousands of farmers in England and Wales, tells Carbon Brief that their “preference” is that solar farms are built on lower quality agricultural land. But they add:
“Renewable energy production is a core part of the NFU’s net-zero plan and solar projects often offer a good diversification option for farmers.”
Kevin McCann, policy manager at trade body Solar Energy UK, tells Carbon Brief:
“Solar is also helping to keep UK farmers in business, by providing them with a stable revenue stream. solar also means less dependence on gas, which is the reason why the UK is in a cost of living crisis.”
At the most recent renewable energy auction, the UK government’s main means of supporting renewable projects, solar projects secured power that were far lower than gas.
Solar is now 88% cheaper than thought a decade ago, UK govt says – half its estimated cost of new gas power
Just running a gas plant in Feb 2022 is costing around FOUR times as much as we’d pay for new solar or wind
Land used for solar power can still be used for farming both livestock and crops, often with little negative impact on yields. (See: What are the impacts of solar panels on farming?)
As planning permission for solar projects is not granted on a permanent basis, the land in question is technically only temporarily out of use and could even improve in quality while not being farmed. Also, solar projects will not necessarily be built on farmland.
The Department for Environment, Food and Rural Affairs (Defra) has made it clear that climate change, not solar power, is the “biggest medium- to long-term risk” to the nation’s domestic food supply.
Government research suggests that climate impacts under a medium-emissions scenario could cut the proportion of best and most versatile arable farmland from a baseline of 38% to 11% by 2050. Farmers are already facing crop failures this year due to extreme heat and drought over the summer.
Analysis by the charity CPRE found that 14,415 hectares (144km2) of best and most versatile land were developed for non-farming purposes between 2010 and 2022, representing an overall loss of just 0.6% of this land type.
Of this land, just 1,400 hectares (14km2) were used for renewable energy developments including solar power – 10% of the total. For comparison, 55% were used for housing.
Finally, analysis by the thinktank Green Alliance found that crops for biofuel production take up 77 times more land than that used for solar panels.
This is significant because, as Carbon Brief analysis shows, a hectare of solar panels delivers between 48 and 112 times more driving distance, when used to charge an electric vehicle, than that land could deliver if used to grow biofuels for cars.
PM Liz Truss complains of fields full of solar panels
Yet a hectare of solar farm delivers 48-112x more driving distance, via an EV, than using the same land for biofuel
Turning UK land currently used for bioethanol over to solar could fuel a quarter of all UK cars
How can land be used for both solar and agriculture?
The debate around using farmland for solar often assumes that the two are incompatible. However, the concept of “agrivoltaics” – also known as agrisolar or agrophotovoltaics – outlines various ways in which land use can be optimised to address the dual needs of energy and food production.
The idea was first described in a 1982 paper, in which the authors “propose a configuration of a solar, e.g., photovoltaic, power plant, which allows for additional agricultural use of the land involved”.
In an agrivoltaic system, crops can be planted below and among raised photovoltaic panels. Dr M Ryyan Khan, an electrical engineer who studies renewable energy systems at East West University in Dhaka, Bangladesh, tells Carbon Brief:
“The idea is that if you put the solar panels on top of the crop fields, you might get benefits from both worlds.”
Because many crops do not need the full amount of light that the sun provides, Khan says, that “extra sunlight” can be harnessed for energy generation.
However, agrivoltaic installations are not just limited to growing crops, says Jordan Macknick, the lead energy-water-land analyst at the National Renewable Energy Laboratory in Golden, Colorado. He tells Carbon Brief:
“Agrivoltaics can mean 1,000 acres of pollinator habitat and native vegetation providing ecosystem services. It can also mean 500 acres of sheep-grazing underneath the panels. It can also mean five acres of someone growing tomatoes and peppers and watermelon underneath the panels.”
Japan is a world leader in agrivoltaics, with the first installations in that country coming online in 2004. According to a 2021 paper, Japan has nearly 2,000 agrivoltaic installations and more than 120 different crops are grown beneath the panels. The country also started the world’s first national funding programme to promote the technology, nearly a decade ago.
Today, examples of agrivoltaic installations can be found around the world, with pilot projects or working agrivoltaic farms on every inhabited continent. In the US, Macknick tells Carbon Brief, the vast majority of agrivoltaic installations are on land that is used either for native pollinator habitat or grazing land.
In 2021, the energy-generating capacity of all agrivoltaic systems worldwide exceeded 14 gigawatts, according to the Fraunhofer Institute for Solar Energy Systems, which notes that this capacity has “increased exponentially” since the early 2010s. The institute also projects that Germany alone has the potential to generate 1.7 terawatts of power from agrivoltaic systems.
The growing interest in agrivoltaics reflects a growing recognition of the vulnerability of agriculture to climate change, says Dr Seeta Sistla, an ecosystem ecologist at the California Polytechnic State University in San Luis Obispo. She tells Carbon Brief:
“What has become abundantly clear across the world is that climate change is absolutely here and it’s affecting every sector of our human lived experience, and it’s especially pertinent in terms of agriculture and land use and land sustainability.”
“Given the sort of reality of climate change that is being felt in real time now versus even five or six years ago, I would say that people are much more willing to consider and think about putting in solar production, both as a climate mitigation strategy, but also as a farm mitigation strategy.”
Photovoltaic cells on a farm can provide an extra, stable source of income for farmers whose yields may become increasingly erratic due to climate change and increasingly frequent weather extremes, Sistla says. She tells Carbon Brief:
“Solar arrays can give footholds for small farms to remain in families, because it provides a constant stream of income versus crops which can fail or the can fluctuate.”
Martin, whose farm is mainly arable, but with some grassland for sheep and cattle, says the solar plans fit into the ethos of regenerative farming that incorporates livestock into an arable rotation. He explains:
“One of the reasons I’m excited about solar is that at the moment we bring in sheep during the winter and they graze on the stubbles [what remains of the crops once harvested] and our winter cover crops.”
The sheep are “tremendous at turning nutrients that we’ve managed to hold in vegetation form over the winter into manure, which is great for our spring crops to access”, says Martin.
However, in the springtime, the sheep go back to their home farm “because we have nowhere to put them”, says Martin:
“Whereas [with the solar park], actually they could stay on our farm and then move through to the wildflower grasses under the solar panels during the summer. That is a really kind of beautiful holistic system.”
And there are other options as well as grazing, says Martin. For example, the rows of solar panels in the proposed scheme will be placed four metres apart. This means that the gaps between them could be cultivated because farm machinery – such as combine harvesters and sowing machines for planting seeds – can be as narrow as three or four metres wide, he says.
The farm also hosts a community garden that “could work very well between the panels”, he adds.
While these options are not as flexible as a bare field, says Martin, having solar panels “complements our broader farming system”.
In addition, planting a “really biodiverse mix of native flora” around the solar panels – which “you could mix with legumes and herbs and grasses” – could also help fix carbon into the soil, says Martin. This would mean restoring soil carbon, producing food and generating energy at the same time, he says:
“Then we’re getting into the territory of win-win-win and that gets even more exciting.”
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What are the impacts of solar panels on farming?
The effects of agrivoltaic arrays on crops is an active area of research, with some crops lending themselves to the system better than others.
For example, tall fruit and nut trees that grow above the elevated solar panels can block the panels and reduce their electricity generation. But other plants, such as leafy greens or berries, can benefit from the extra shade provided by the panels.
In general, Sistla tells Carbon Brief, agrivoltaics do well with low-growing crops that are typically harvested by hand and, therefore, do not require new, specialised equipment that can navigate the solar array.
A wide range of crops, including tomatoes, basil and pasture grass, have been experimentally shown to have comparable yields in agrivoltaic systems as in conventional farming. On grazing lands, solar arrays increase the forage quality, the water and nutrient content of plant matter and reduce water demand, Sistla says.
For example, a 2018 study in Oregon in the US found that grazing grasses grew better in the shade of solar panels, with “dramatic gains in productivity” providing 90% more biomass through the summer thanks to the areas under the panels being 328% more water efficient.
The panels can benefit livestock, too. Earlier this year, a four-year trial in Australia found that wool from merino sheep improved in both quality and quantity on farms that had installed solar panels. This was down to the “panels providing shelter for the sheep and grass”, the Independent reported.
Just as the choice of crop can affect the potential of an agrivoltaic system, so too can the climate and location.
In the western US, where there is an “abundance of sun” and a lack of water, agrivoltaic research has had “very promising” results, Macknick says.
In arid regions, the shade provided by photovoltaic panels can improve water retention and protect delicate plants. The added shade can also be beneficial to farm labourers and grazing livestock during the heat of the day, Sistla says.
By contrast, the research has shown “much more nuanced results” in the northeastern US, Macknick tells Carbon Brief. During a typical summer, agrivoltaics have resulted in depressed yields of some crops. But in unusually hot or dry summers, the results are similar to those seen in arid regions. So agrivoltaics may be able to help mitigate some of the climate extremes, he says.
While much of the agrivoltaic research on crops has focused on vegetables, there is growing evidence that such setups can be profitable in “major crop” systems – those that grow staple crops such as rice, wheat and maize, which are typically less shade-tolerant – Khan says.
A 2019 study found that stilt-mounted photovoltaic panels could be installed on cornfields without reducing maize production. And a recent study that Khan worked on found that agrivoltaics deployed on rice paddies “will always be profitable” due to the relative of crops and electricity. With the right governmental policies and strategies in place, he says, smallholder farmers could lease their land to energy companies in return for a portion of the profits from the panels.
Just as photovoltaics can affect the crops below them, the crops can influence the efficiency of the panels above. One 2019 study found that photovoltaic energy production potential is actually greater over croplands than other types of land because of the cooling effect of the crops’ evapotranspiration.
What that study does not take into account, Khan tells Carbon Brief, is that the increased relative humidity can hasten the panels’ degradation. Instead of the 25-year lifespan of a conventional photovoltaic array, an agrivoltaic array may only last 20 years, he says – which should be taken into account when planning such an array and evaluating its economic potential.
The long duration of an agrivoltaic installation means that careful planning must be involved to ensure long-term success, Macknick says. A recent NREL report (pdf) laid out a number of considerations for successful agrivoltaic deployment. Among other recommendations, getting buy-in from farmers is paramount to success, Macknick says. He tells Carbon Brief:
“The partnerships that are developed right away between the solar developer and the agricultural entity are absolutely instrumental. They need to be working together from the beginning, in order to make sure you do have a successful arrangement where someone would want to farm for the next 20 years, because the solar projects will last 20, 25, 30 years. You’re gonna want someone to be farming all those years as well.”
Geneverse HomePower One solar-powered generator review
Credit: Reviewed / Jean Levasseur
Recommendations are independently chosen by Reviewed’s editors. Purchases made through the links below may earn us and our publishing partners a commission.
Cons
Editor’s Note: Generark is now Geneverse.
Power outages happen everywhere. While usually the consequences are as minor as not being able to check for a few minutes, long-lasting power outages can have costly and potentially deadly results. On site, portable power generation is a great way to keep your home and family safe when the electricity cuts out, whether for a few hours, days, or weeks.
Traditional on-site power generators are loud, heavy machines that run on gasoline and require regular maintenance. They also emit deadly carbon monoxide gas, and so have to be kept outside.
However, advances in battery technology over the past few years have made battery storage a viable alternative. The Geneverse HomePower One (available at Amazon) is a battery backup power station designed to give you reliable, relatively long-lasting power to get you through an emergency.
And, when you pair the battery system with Geneverse’s SolarPower One panels, you get a power bundle that can keep your home running until the lights come back on.
What is the Geneverse HomePower One and SolarPower One system
I was able to use the Geneverse HomePower One and SolarPower One system for several weeks at my house. Fortunately, we never had an emergency situation, but I did put it to the test.
I used it to power my refrigerator for a day, ran my Instant Pot and rice cooker (it can’t power a stove), and even brought it down into my workshop to see how it did with power tools.
Overall, I was impressed. While it won’t power your entire house, it will keep your food cold, give you enough power to cook basic meals, and let you use most medical devices that you need.
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best-right-now
When it’s time to charge, the solar panels do a surprisingly good job, provided that it’s not an overcast day. If it is an overcast day, in a pinch you can charge it through your vehicle’s auxiliary power outlet.
And yes, you can keep using the power while the unit is charging.
In addition to emergency home use, I can also see a use for this product as a job site power source. It was easily able to power my router, sander, drill, and circular saw, though it wasn’t quite up to the task of powering my table saw and miter saw.
All in all, if you’re looking for a non-gasoline emergency backup system, the HomePower One and the accompanying SolarPower One are an excellent choice.
About the Geneverse HomePower One
This multifaceted generator is not only portable, but also adaptable enough to be used indoors or outdoors.
- 1,002 watt-hour (Wh) capacity
- Up to seven days of power, depending on usage
- Multiple power outputs: 2 USB-C outputs with PD 18W, 1 USB-A with 5V/2.4A, 1 USB-A with Qualcomm Quick Charge 3.0, and 1 car outlet with 12V/10A.
- Stores power up to one year
- 5-year warranty
- Easy-to-read display
- Simple setup and use
About the Geneverse SolarPower One
A more sustainable way to power your home–without the danger of a gasoline generator.
- 100W power output per panel
- 50% higher energy conversion than traditional solar cells
- Also supports USB-C and USB-A charging
- Fast setup
- 5-year warranty
What we like
Clean and quiet operation for indoor use
In the event of a storm or a citywide power outage, the Geneverse Solar Generator can provide long-lasting use for your appliances with its 1,002 Wh battery.
Traditional gasoline-powered generators are noisy and stinky, and, for both safety and sanity, need to stay outside. The HomePower One, however, is just a large battery. It’s perfectly safe to use in the same room as you are. Need the toaster? Bring it into the kitchen. Need a light in the basement? Bring it down with you.
It’s lightweight and mobile. You don’t have to run extension cords through open Windows in winter or worry about tripping over them in the living room. Store it inside and use it inside, without any concern.
Multiple power outputs
Geneverse recognizes that our power needs vary throughout the day, and the HomePower One has outputs to fit just about every use case. The 3 AC outlets power normal appliances and lights, while the collection of USB and micro USB outputs allow charging of devices so we can stay in touch, up to date, and informed in an emergency.
And, with so many different outputs, the HomePower One can power multiple devices at a time, provided that they don’t exceed the capacity.
Super easy setup
I was skeptical when the instructions said that the solar powered system could be set up in 30 seconds or less. But it really can.
Simply bring the panels out to the sun, unfold them, plug them into the HomePower One, and they start generating power immediately. If I were to buy these for myself, I would build some sort of stand to keep them up out of the snow, mud, and dirt. For testing purposes, they worked just fine on the hood of my car.
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What we don’t like
Honestly, not much. The drawbacks of the system are mostly innate to the type of power, and not a problem with the unit itself.
The solar panels don’t work great on cloudy days
For optimal charging, stick to bright, sunny days.
I tested the HomePower One in February and March in New England. On sunny days, the panels do pretty well, producing between 100W and 120W, which would fully charge the unit in nine or 10 hours.
However, on cloudy winter days, that output plummeted to around 15W, which wouldn’t charge the unit full before night fell. While a little bit of power is certainly better than no power, you will be at the mercy of the weather for power after you’ve drained the initial charge.
Limited capacity
Geneverse claims that the unit can provide power for up to seven days. And, I’m sure that’s true, if all you’re charging is your phone.
However, most people without power won’t get anywhere near seven days before needing to recharge. And, to be fair to Geneverse, the company does have a list of estimates for how long the unit will power different appliances.
As near as I can tell, these estimates are pretty close. I was able to power my refrigerator for about 11 hours before the battery died. Cooking one meal with my Instant Pot took about 10% of the battery power. A few hours of woodworking took another 30% or so.
I also tried to use more than one kitchen appliance at once (both my Instant Pot and rice cooker) and the Geneverse couldn’t handle both simultaneously.
Shuts off without warning
This is the only true gripe that I have with the design of the system. When it is overloaded, it shuts off. Which is great—no one wants the battery to overheat and start a fire. However, there’s no warning when this happens.
When I overloaded the battery by trying to run multiple appliances, I didn’t know it had shut off 10 or so minutes later when I went to check on dinner. So, you do want to check on it, particularly if it’s charging something frequently out of mind like a refrigerator.
Warranty
Geneverse offers a 5-year limited warranty on the HomePower One and SolarPower One products, on top of a 30-day return policy. If the product is found to be defective within the five-year window, Geneverse will exchange the unit for a replacement.
Should you buy the Geneverse HomePower One and SolarPower One?
While their are a bit steep, we have no doubt that the Geneverse HomePower One and SolarPower One are a handy duo to have on hand.
Yes.
There’s no question that a gasoline-powered generator with the same power capacity would be less expensive than the Geneverse HomePower One. But, it’s also more hassle and more work.
If you’re looking to get away from a gas-powered solution, or if you simply live in a place where a gas generator isn’t feasible like an apartment, then the Geneverse is a fantastic solution for you.
Even if you just buy it for emergencies, there’s no question that you will be able to find far more uses for it. I can see these units being great for camping, for example.
It’s a quality product that does exactly what the company claims it will. Keeping it on hand, fully charged, will be great peace of mind for you and your family
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were accurate at the time this article was published but may change over time.
The 7 Best Solar Generators and Why They Don’t Lower Carbon Emissions Without Offsets
Our planet definitely needs help to lower greenhouse gases, and since one of the biggest polluters is power production, finding alternative methods makes sense. But are solar generators the answer? You may be surprised to learn that while solar generators and panels do help lower emissions by some, they can’t eliminate them without help.
Solar generators have come a long way in the last 10-15 years, but if you’re serious about reducing your carbon footprint, there are some important things to know before purchasing that generator for your next camping trip or attaching solar panels to your roof.
We know that solar panels have been used successfully in many areas of the globe as a reliable, green energy source. So, how does that translate to home use through generators? And can you lower your carbon emissions using them alone? This article explores those questions and offers reviews on the top-performing generators of 2022.
Yeti 1500x Portable Power Station
High wattage in a convenient size.
Jackery Portable Power Station Explorer 1000
Super lightweight with low cost.
MaxOak Portable Power Station BLUETTI EB150
Reasonable watts with a slightly heftier size.
ALLWEI Portable Power Station
Lower watts but much more affordable.
Sunbox Labs Solar Generator
Perfect for campers and super lightweight.
EF EcoFlow Portable Power Station Delta
Mega wattage for powering anything, not too heavy to transport easily.
Nature’s Generator
Heavier, but convenient wheels make this easy to move.
How Do Solar Panels Work?
Without going too deeply into the science, solar panels work on the same general principle as photosynthesis, but unlike plants, they convert sunlight into energy instead of synthesizing carbon dioxide, food, and water. Modern solar panels are about 20 percent efficient under standard conditions, though of course, many factors such as location, weather, and even temperature can affect this.
After the panels produce the energy, things get a bit tricky. Most of us need a reliable, steady source of electricity for gadgets and major appliances, so solar generators store the solar power they create and release it in a way that’s reliable and steady.
Facts About Solar Power
Solar panels provide relatively cheap and inexpensive energy. In fact, unlike fossil fuels that the US Energy Information Agency says provided over 60% of America’s utility-scale electricity generation in 2020, 1 renewable energy production is still in its infancy. But, both the costs and efficiency of solar cells have been improving for years. As a result, the cost of solar power has dropped by a factor of 400 in the last 45 years… and residential solar panels produce about 18 times less carbon dioxide (a greenhouse gas) than coal.
However, home panels and the associated equipment they require can be expensive. As a long-term investment, solar will save you money eventually, and there are a number of federal incentives to support their installation in homes, but the up-front cost is heavy. But, that doesn’t mean that the price isn’t worth it for the environment… it is.
Opponents of solar panels are fond of pointing out that for people who live somewhere that only gets 20 sunny days per year, they won’t work. Also, they argue that the manufacture of the panels generates pollution. This is because some of the components of the panels and their associated batteries contain parts that cause pollution when mined or are difficult to dispose of once they’ve become obsolete.
Although those things are accurate, a good solar panel installation can last up to 40 years, and typical solar residential solar panels have a carbon footprint that’s about 18 times smaller than the carbon footprint of coal and about 10 times smaller than the footprint of natural gas, so they remain a viable option for reducing your ecological footprint.
America alone produced over 5 billion metric tons of CO2 to generate electricity in 2019, 2 and the rest of the world produced another 28 billion metric tons. Alternative forms of energy can start to reduce those massive numbers. To determine the amount of your emissions you can use an ecological footprint calculator.
How Do I Know If My House Is a Good Candidate for Solar Panels?
Knowing whether your home is a good candidate for solar installation is easy to find. Google, one of the first major companies to go completely carbon neutral in 2007, has a program called Project Sunroof, which allows you to enter your address and your average power bill (so they can calculate your savings) and the tool will tell you whether solar is feasible for your home. 3
This is important to know, because most generators require solar panel installation.
What Are the Four Best Solar Generators?
“Best” is a fairly subjective word… but these generators really stand out for 2022.
Keep in mind that there are different types of generators and systems. For example, if you’re looking to get off the grid with your RV, you’ll want a portable system for camping. By comparison, if you want a backup generator in case the grid fails or has an issue, you’ll be looking for a heftier (and more expensive) home system.
Also, most of these generators – require solar panels. Remember to budget for the solar panels on specific models, and to check with your provider on installation best practices.