Article

Global potential of offshore and shallow waters macroalgal biorefineries to provide for food, chemicals and energy: Feasibility and sustainability

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Abstract

Displacing fossil fuels with renewables and increasing sustainable food and chemicals production are among the major challenges facing the world in the coming decades. Integrating climatological oceanographic data with a metabolism and growth rate model of the green marine macroalga from Ulva genus, we analyze the potential of offshore biorefineries to provide for biomass, ethanol, butanol, acetone, methane and protein, globally and in 13 newly defined offshore provinces. We show that for optimum fresh weight stocking density of 4 kg m− 2 the total potential of offshore cultivated Ulva biomass is of the order of 1011 dry weight (DW) ton year− 1, over a surface area of ~ 108 km2. We found that the distance of the offshore cultivation site to the processing facility is limited to 114–689 km, depending on cargo moisture content. The near-future technologically deployable areas, associated with up to 100 m water installation depth, and 400 km distance from the shore, can provide for 109 DW ton year− 1, which is equivalent to ~ 18 EJ. This has the potential to displace entirely the use of fossil fuels in the transportation sector or provide for 5–24% of predicted plant proteins demand in 2054. In addition, we modeled the potential production of ethanol, butanol, acetone and methane from the offshore produced biomass. Finally, we analyzed the environmental risks and benefits of large-scale offshore macroalgal cultivation. These results are important as they show for the first time the potential of offshore biomass cultivation to reduce the use fossil fuels and arable land to provide for food, chemicals and fuels required for the society.

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May 2016
Lehahn Yoav · Kapilkumar Nivrutti Ingle · Alexander Golberg
... For example, macroalgae cultivation has the potential to mitigate climate change (Duarte et al., 2017) by absorbing CO 2 from water. Its use as a CO 2 removal mechanism for climate mitigation has been proposed (Lehahn et al., 2016;Moreira and Pires, 2016;Krause-Jensen et al., 2018), but largely depends on the fate of the seaweed grown i.e. most of the CO 2 captured is released back into the atmosphere if the seaweed is eaten or ultimately decomposed. Seaweed also improves water quality (e.g., Neori et al., 1993), positively impacts biogeochemical cycling, primary production and food web dynamics (Ramus, 1992;Xie et al., 2017), provides nursery grounds and habitat for fish (e.g., Theuerkauf et al., 2022) and protects coasts and biodiversity (Sugumaran et al., 2022). ...
... Typically, mechanistic or statistical modellingbased predictions of potential yields have only been made in localised areas e.g., embayments or limited areas of open coast e.g (Broch et al., 2019;Aldridge et al., 2021); or in a few cases at the sub-basin scale (Van Der Molen et al., 2018;Kotta et al., 2022). One study does present an analysis of potential yield of macroalgae globally, by application of a mechanistic model to geospatial environmental data (Lehahn et al., 2016). While a predictive, mechanistic modelling approach at this scale has significant uncertainty associated, not least due to the challenges of validation, it is nonetheless a potentially valuable tool in evaluating potential yields and impacts of aquaculture at the continental scale. ...
... U. lactuca was selected for its tolerance to a broad range of temperature and nutrient concentrations. This ubiquitous species is mostly farmed in land-based facilities but lately its potential for near-shore or even deep ocean cultivation is gaining increasing attention (Lehahn et al., 2016;Steinhagen et al., 2021). Parameter values for each species were selected from a synthesis of literature values and are presented in Tables 4-6 of Section 3 of the Supplementary Material. ...
Article
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Large-scale seaweed and shellfish aquaculture are increasingly being considered by policymakers as a source of food, animal feed and bioproducts for Europe. These aquacultures are generally thought to be low impact or even beneficial for marine ecosystems as they are ‘extractive’ – i.e., growing passively on foodstuff already available in seawater, and with potential habitat provision, fisheries, climate mitigation and eutrophication mitigation benefits. At some scale however, over-extraction of nutrients or chlorophyll could potentially have a negative effect on natural systems. Understanding the likely impacts of aquaculture production at scale is important to identify when safe limits are being approached. Taking seaweed aquaculture as the primary focus, this work uses operational oceanographic model outputs to drive prognostic growth models to predict the likely optimal distribution of seaweed farms across European waters to meet different production scenarios. A novel nutrient transport scheme is then used to model the interacting ‘footprints’ of nutrient drawdown from aquaculture facilities to demonstrate the likely spatial impact of large-scale aquaculture. Evaluation of both seaweed and shellfish contributions to CO2 balance under large scale production, and the potential impact on fisheries are also considered. The study finds that the impact of intensive seaweed aquaculture on nutrient availability could be significant where many farms are placed close together; but at the regional/basin scale even the highest level of production considered does not significantly impact total nutrient budgets. Seaweed aquaculture has the potential to extract large amounts of carbon dioxide, but the impact on carbon budgets depends on the end-use of the extracted seaweed. Shellfish aquaculture is a net source of CO2 due to the impact of calcification of shells on the carbonate system (i.e., alkalinity removal). However, gram-for-gram the CO2 impact of shellfish production is likely to be less than the impact of land-based meat production. Whilst operational oceanographic models are useful for taking a ‘broad brush’ approach to likely placement and impacts of aquaculture, reliable yield predictions for individual locations across European waters would require models integrating more physical and biogeochemical factors (wave environment, local currents, riverine inputs) at a finer scale than currently achievable.
... Details of carbon storage scenarios for three shelf carbon management options are presented in Text S3. The utilization of riverine nutrients for macroalgal aquaculture and subsequent long-term sequestration of harvested biomass (e.g., Lehahn et al., 2016) was evaluated as follows. Intensive macroalgal aquaculture in river plumes was assumed to capture 50% of anthropogenic nutrients and convert them into seaweed (C:N ratio 18). ...
... We considered the following mCDR methods, taking literature values of maximum potential sequestration rates: open ocean seaweed cultivation (e.g., Lehahn et al., 2016; Table S4), ocean alkalinization, ocean iron fertilization, macronutrient fertilization, and artificial upwelling (e.g., Keller et al., 2014;Harrison, 2017; Table S5). Full details of scenarios and input data are provided in Text S4. ...
... The former relies on hitherto unproved technology for growing seaweed in the deep ocean and also would require a considerable amount of the global ocean surface (approximately 1%-3% to achieve the range of potential carbon sequestration in Figure 3), with all the associated risks and trade-offs. This area is only one-tenth of the 9%-33% of the global ocean coverage proposed by the source papers (de Ramon N'Yeurt et al., 2012;Lehahn et al., 2016), with carbon sequestration scaled accordingly, but is still, in our opinion, pushing the limits of what might be feasible, environmentally sound, or socially acceptable (noting that publication of a negative emissions "solution" in the peerreviewed literature does not mean that it is safe, feasible, or even worth pursuing; e.g., Johnson et al., 2008). Nonetheless, as with coastal macroalgal aquaculture, this open ocean approach at some scale could potentially provide a relatively safe and low risk, measurable carbon sequestration and is therefore likely to be a subject of increasing study and commercial development in the coming years. ...
Article
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In this Policy Bridge, we present the key issues regarding the safety, efficacy, funding, and governance of coastal and marine systems in support of climate change mitigation. Novel insights into the likely potential of these systems for use in mitigating excess carbon dioxide emissions are presented. There may be potential for coastal blue carbon and marine carbon dioxide removal (mCDR) actions to impact climate change mitigation significantly over the rest of the 21st century, particularly post 2050. However, governance frameworks are needed urgently to ensure that the potential contribution from coastal and ocean systems to climate change mitigation can be evaluated properly and implemented safely. Ongoing research and monitoring efforts are essential to ensure that unforeseen side effects are identified and corrective action is taken. The co-creation of governance frameworks between academia, the private sector, and policymakers will be fundamental to the safe implementation of mCDR in the future. Furthermore, a radical acceleration in the pace of development of mCDR governance is needed immediately if it is to contribute significantly to the removal of excess carbon dioxide emissions by the latter half of this century. To what extent large-scale climate interventions should be pursued is a decision for policymakers and wider society, but adaptive legal, economic, policy, research, and monitoring frameworks are needed urgently to facilitate informed decision-making around any implementation of mCDR in the coming decades. Coastal and ocean systems cannot be relied upon to deliver significant carbon dioxide removal until further knowledge of specific management options is acquired and evaluated.
... Although the MOS concept is still in its infancy, it seems to be gaining more attention due to the effectiveness of macroalgae in absorbing more CO 2 compared to other 'blue carbon' resources and the potential scalability of existing macroalgae farming industry (Krause-Jensen and Duarte, 2016;Lehahn et al., 2016;Froehlich et al., 2019;Coleman et al., 2022;Ross et al., 2022). Several recent studies tried to estimate how much space is necessary for effective CDR through MOS operation. ...
... The proximity of potential MOS/Sink areas to the shore is important not only for nutrient availability but also for optimizing the necessary logistics required for project implementation. Combining information from the economic feasibility studies of (Lehahn et al., 2016;Coleman et al., 2022;DeAngelo et al., 2023) a one-way distance to the nearest port of 1000 km was considered as maximum acceptable. A vessel suitable for such operations with an average speed of 15 knots, containing 100k metric tons of fresh seaweed biomass would need approximately 72 h to cover a 2000 km distance (two-way) which results in a 2-20% reduction in CO 2 efficiency due to emissions from fuel consumption (Lehahn et al., 2016;Bach et al., 2021). ...
... Combining information from the economic feasibility studies of (Lehahn et al., 2016;Coleman et al., 2022;DeAngelo et al., 2023) a one-way distance to the nearest port of 1000 km was considered as maximum acceptable. A vessel suitable for such operations with an average speed of 15 knots, containing 100k metric tons of fresh seaweed biomass would need approximately 72 h to cover a 2000 km distance (two-way) which results in a 2-20% reduction in CO 2 efficiency due to emissions from fuel consumption (Lehahn et al., 2016;Bach et al., 2021). Therefore, an empirical Gaussian distribution function was applied to the Distance2port dataset (Table 1; Supplementary Figure 1) in order to assign high scores to areas closest to nearest ports, while introducing rapid score decrease with increasing distance beyond the 1000 km fuzzy boundary. ...
Article
Full-text available
Macroalgae offshore cultivation and sinking is considered a potentially practical approach for ocean-based carbon dioxide removal. However, several considerations need to be resolved to assess the effectiveness and sustainability of this approach. Currently, several studies focus on the area required for climate-relevant carbon sequestration through macroalgae cultivation and sinking without considering realistic, global spatial limitations. This study uses a spatially-explicit suitability assessment model for optimised open-ocean afforestation and sinking site designation. By applying specific maritime, ecological and industrial constraints, two maps are produced: a) suitable areas for macroalgae offshore cultivation and sinking, and b) suitable areas for macroalgae sinking only (for sequestration purposes). These data provide a more realistic approach to quantifying the ocean surface (including the corresponding depths) required for macroalgae offshore cultivation and sinking within a spatially sustainable framework. The resulting maps estimate the respective suitability areas within the EEZs of the world countries. A total area suitable for macroalgae offshore cultivation and sinking is calculated at 10.8M km², whereas sinking-only areas account for 32.8M km² of the offshore ocean. The implications of spatial suitability patterns at global and national levels are discussed. We suggest that the concept of ‘grow nearshore, sink offshore’ should be explored as an alternative to offshore cultivation.
... Although the MOS concept is still in its infancy, it seems to be gaining more attention due to the effectiveness of macroalgae in absorbing more CO2 compared to other 'blue carbon' resources and the potential scalability of existing macroalgae farming industry (Coleman et al., 2022;Froehlich et al., 2019;Krause-Jensen and Duarte, 2016;Lehahn et al., 2016;Ross et al., 2022). Several recent studies tried to estimate how much space is necessary for effective CDR through MOS operation. ...
... The proximity of potential MOS/Sink areas to the shore is important not only for nutrient availability but also for optimizing the necessary logistics required for project implementation. Combining information from the economic feasibility studies of (Coleman et al., 2022;DeAngelo et al., 2023;Lehahn et al., 2016) a one-way distance to the nearest port of 1000 km was considered as maximum acceptable. A vessel suitable for such operations with an average speed of 15 knots, containing 100k metric tons of fresh seaweed biomass would need approximately 72 h to cover a 2000 km distance (twoway) which results in a 2-20% reduction in CO2 efficiency due to emissions from fuel consumption (Bach et al., 2021;Lehahn et al., 2016). ...
... Combining information from the economic feasibility studies of (Coleman et al., 2022;DeAngelo et al., 2023;Lehahn et al., 2016) a one-way distance to the nearest port of 1000 km was considered as maximum acceptable. A vessel suitable for such operations with an average speed of 15 knots, containing 100k metric tons of fresh seaweed biomass would need approximately 72 h to cover a 2000 km distance (twoway) which results in a 2-20% reduction in CO2 efficiency due to emissions from fuel consumption (Bach et al., 2021;Lehahn et al., 2016). Therefore, an empirical Gaussian distribution function was applied to the Distance2port dataset (Table 1; Supplementary material, Fig.S1) in order to assign high scores to areas closest to nearest ports, while introducing rapid score decrease with increasing distance beyond the 1000 km fuzzy boundary. ...
Preprint
Macroalgae offshore cultivation and sinking is considered a potentially practical approach for ocean-based carbon dioxide removal. However, several considerations need to be resolved to assess the effectiveness and sustainability of this approach. Currently, several studies focus on the area required for climate-relevant carbon sequestration through macroalgae cultivation and sinking without considering realistic, global spatial limitations. This study uses a spatially-explicit suitability assessment model for optimised open-ocean afforestation and sinking site designation. By applying specific maritime, ecological and industrial constraints, two maps are produced: a) suitable areas for macroalgae offshore cultivation and sinking, and b) suitable areas for macroalgae sinking only (for sequestration purposes). These data provide a more realistic approach to quantifying the ocean surface (including the corresponding depths) required for macroalgae offshore cultivation and sinking within a spatially sustainable framework. The resulting maps estimate the respective suitability areas within the EEZs of the world countries. A total area suitable for macroalgae offshore cultivation and sinking is calculated at 10.8M km2, whereas sinking-only areas account for 32.8M km2 of the offshore ocean. The implications of spatial suitability patterns at global and national levels are discussed. We suggest that the concept of ‘grow nearshore, sink offshore’ should be explored as an alternative to offshore cultivation.
... In comparison to land-based agriculture, seaweed is partly shielded from this by the water it grows in. Moreover, seaweed is a potential biofuel solution (29,38). Recent research established that seaweed could contribute up to 100 % of the human protein need (39) and that globally around 48 million km² are suitable for seaweed production (40). ...
... Its current growing conditions are similar to those found near the equator in the case of nuclear winter (41) and its environmental constraints for growth are well known (72). It has also been proven to be suitable for offshore cultivation (38). It has growth rates, as well as nutrient, illumination and temperature needs which are in a typical range for seaweeds (46,74). ...
... This accounts for self-shading (72) ( Figure S14) and how much area is available to grow seaweed. The seaweed grows until it has reached a density of 3.6 kg per m² and is then cut back to 1.2 kg per m², the optimal trimming threshold to minimize self-shading (38,43). Once the whole seaweed farm area is saturated with seaweed, all yield thereafter can be used to produce food, feed and biofuel. ...
Preprint
Full-text available
Abrupt sunlight reduction scenarios such as a nuclear winter caused by the burning of cities in a nuclear war, an asteroid/comet impact or an eruption of a large volcano inject large amounts of particles in the atmosphere, which limit sunlight. This could decimate agriculture as it is practiced today. We therefore need resilient food sources for such an event. One promising candidate is seaweed, as it can grow quickly in a wide range of environmental conditions. To explore the feasibility of seaweed after nuclear war, we simulate the growth of seaweed on a global scale using an empirical model based on Gracilaria tikvahiae forced by nuclear winter climate simulations. We assess how quickly global seaweed production could be scaled to provide a significant fraction of global food demand. We find seaweed can be grown in tropical oceans, even after nuclear war. The simulated growth is high enough to allow a scale up to an equivalent of 45 % of the global human food demand (spread among food, animal feed, and biofuels) in around 9 to 14 months, while only using a small fraction of the global ocean area. The main limiting factor being the speed at which new seaweed farms can be built. The results also show that the growth of seaweed increases with the severity of the nuclear war, as more nutrients become available due to increased vertical mixing. This means that seaweed has the potential to be a viable resilient food source for abrupt sunlight reduction scenarios.
... • Seaweed products might replace products with a higher CO 2 footprint, thereby avoiding emissions (rather than directly contributing to sequestration) in fields such as food, feed, fertilisers, nutraceuticals, biofuels, and bioplastics (World Bank 2016; Lehahn et al. 2016;Duarte et al. 2017). The extent of this mitigation pathway is currently not known. ...
... We adopted the scenario of a 14% annual increase in production to provide an upper limit of the sequestration potential by 2030 and 2050, and we further assume that farming could proceed at this rate of increase without meeting constraints before 2050. An even higher production estimate of 10 billion tonnes dry weight/year was recently proposed (Lehahn et al. 2016), indicating that our estimated upper limit of seaweed production is not unrealistic. ...
... Despite large areas of EU marine regions being unsuitable for seaweed cultivation, such as the Mediterranean and Black Seas, the potentially suitable area remains extensive, totalling over 1.5 million km 2 for intermediate species and over 1 million km 2 for cold water species (Fig. 1A), is located mostly in the NWES and SWES domains. Identifying the Atlantic areas as the only suitable marine EU regions for seaweed cultivation aligns with previous global reports (e.g., Halpern et al., 2019;Lehahn et al., 2016;van Oort et al., 2022). Also, the average value of AAGR in those suitable places is 27 tonnes DW ha -1 y -1 for intermediate species and 31 tonnes DW ha -1 y -1 for cold species, which fall within the range of previously published values (e.g., Lehahn et al., 2016;Chynoweth, 2022;Brunh et al., 2011;Gao et al., 2022). ...
... Identifying the Atlantic areas as the only suitable marine EU regions for seaweed cultivation aligns with previous global reports (e.g., Halpern et al., 2019;Lehahn et al., 2016;van Oort et al., 2022). Also, the average value of AAGR in those suitable places is 27 tonnes DW ha -1 y -1 for intermediate species and 31 tonnes DW ha -1 y -1 for cold species, which fall within the range of previously published values (e.g., Lehahn et al., 2016;Chynoweth, 2022;Brunh et al., 2011;Gao et al., 2022). ...
... Value Ref. Inshore coastal surface area (Scenario A) 5.7 million km 2 [231] Total theoretical ocean surface area for Ulva seaweed farms (Scenario B) 100 million km 2 [235] Ecologically available ocean area for seaweed farms (Scenario C) 48 million km 2 [236] Wild seaweed average net primary productivity 420 g C m −2 year −1 [231] M. pyrifera net primary productivity 1300 g C m −2 year −1 [232] Ulva sp. net primary productivity 838 g C g m −2 year −1 [237] Carbon to biomass dry weight conversion factor 4 [231] Biomass dry weight to fresh weight conversion factor 4 [238] HVC Extraction Biomass (dw) to bioethanol conversion factor 0.213 kg/kg [239] Ethanol density 783 kg/m 3 Bioethanol market price USD 0.4/L [240] Biomass (dw) to phlorotannin conversion factor 0.002005 mg/kg [241] Phlorotannin market price USD 70/kg [89] Biomass (dw) to protein conversion factor 0.6169 mg/kg [242] Carbohydrate ratio of M. pyrifera (dw) 0.648 kg/kg [242] Carbohydrate extraction efficiency 89.67% [242] Alginate fraction of M. pyrifera carbohydrates 62.54% [242] Alginate market price USD 12/kg [77] Mannitol fraction of M. pyrifera carbohydrates 8.05% [242] Mannitol market price USD 7.3/kg [61] Single-cell protein price USD 10.4/kg [243] ...
... For example, despite Scenario C being ecologically possible, biomass transportation from distant offshore seaweed farms to marine biorefineries becomes a major challenge, leading to increased production costs. Indeed, until more advances are made in transportation technologies, seaweed farming will be restricted to areas close to the coast [235]. Another major issue is the environmental consequences of seaweed farming. ...
Article
Full-text available
Seaweeds are among the most important biomass feedstocks for the production of third-generation biofuels. They are also efficient in carbon sequestration during growth and produce a variety of high-value chemicals. Given these characteristics together with the relatively high carbohydrate content, seaweeds have been discussed as an ideal means for CO2 capture and biofuel production. Though third-generation biofuels have emerged as some of the best alternatives to fossil fuels, there is currently no large-scale production or mainstream use of such liquid fuels due to the many technical challenges and high production costs. The present study describes the concept of coastal marine biorefineries as the most cost-effective and sustainable approach for biofuel production from seaweeds, as well as atmospheric carbon capture and storage (CCS). The suggested refinery system makes use of marine resources, namely seawater, seaweed, and marine microorganisms. Firstly, extensive screening of the current literature was performed to determine which technologies would enable the emergence of such a novel biorefinery system and its merits over conventional refineries. Secondly, the study investigates various scenarios assessing the potential of seaweeds as a means of carbon sequestration. We demonstrate that the removal of 100 Gigatons of excess CO 2 using seaweed farms can be achieved in around 4 months to less than 12 years depending on the area under cultivation and the seaweed species. The total bioethanol that could be generated from the harvested biomass is around 8 trillion litres. In addition, high-value chemicals (HVC) that could potentially be recovered from the process represent a considerable opportunity with multi-billion-dollar commercial value. Overall, coastal marine biorefineries have strong potential for a sustainable green economy and represent a rapid approach to climate change mitigation.
... 2100 CO2 removal goal 100 Gt [3] CO2 to Carbon conversion factor 3.67 [3] Inshore Coastal Surface Area (Scenario A) 5.7 million km 2 [233] Total theoretical ocean surface area for Ulva seaweed farms (Scenario B) 100 million km 2 [237] Ecologically available ocean area for seaweed farms ( Scenario C) 48 million km 2 [238] Wild seaweed average net primary productivity 420 g C m -2 year -1 [233] M. pyrifera net primary productivity 1300 g C m -2 year -1 [234] Ulva sp. net primary productivity 838 g C g m -2 year -1 [239] Carbon to biomass dry weight conversion factor 4 [233] Biomass dry weight to fresh weight conversion factor 4 [240] HVC Extraction Biomass (dw) to bioethanol conversion factor 0.213 kg/kg [241] Ethanol density 783 kg/m 3 Bioethanol market price 0.4 USD/L [242] Biomass (dw) to phlorotannin conversion factor 0.002005 mg/kg [243] Phlorotannin market price 70 USD/kg [91] Biomass (dw) to protein conversion factor 0.6169 mg/kg [244] 18 Carbohydrate ratio of M. pyrifera (dw) 0.648 kg/kg [244] Carbohydrate extraction efficiency 89.67 % [244] Alginate fraction of M. pyrifera carbohydrates 62.54 % [244] Alginate market price 12 USD/kg [79] Mannitol fraction of M. pyrifera carbohydrates 8.05 % [244] Mannitol market price 7.3 USD/kg [64] Single cell protein price 10.4 USD/kg [245] ...
... For example, despite scenario C being ecologically possible, biomass transportation from distant offshore seaweed farms to marine biorefineries becomes a major challenge, leading to increased production costs. Indeed, until more advances are made in transportation technologies, seaweed farming will be restricted to areas close to the coast [237]. Another major issue is the environmental consequences of seaweed farming. ...
Preprint
Full-text available
: Seaweeds are among the most important biomass feedstocks for the production of third generation biofuels. They are also efficient in carbon sequestration during growth, and produce a variety of high value chemicals. Given these characteristics together with the relatively high carbohydrate content, seaweeds have been discussed as an ideal means for CO2 capture and biofuel production. Though third generation biofuels have emerged as some of the best alternatives to fossil fuels, there is currently no large-scale production or mainstream use of such liquid fuels due to the many technical challenges and high production costs. The present study describes the concept of coastal marine biorefineries as the most cost-effective and sustainable approach for biofuel production from sea-weeds as well as atmospheric carbon capture and storage (CCS). The suggested refinery system makes use of marine resources, namely seawater, seaweed, and marine microorganisms. Firstly, extensive screening of the current literature was performed to determine which technologies would enable the emergence of such a novel biorefinery system and its merits over conventional refineries. Secondly, the study investigates various scenarios assessing the potential of seaweeds as a means of carbon sequestration. We demonstrate that the removal of 100 Gigatons of excess CO2 using seaweed farms can be achieved in around 4 months to less than 12 years depending on the area under cultivation and the seaweed species. The total bioethanol that could be generated from the harvested biomass is around 8 trillion litres. In addition, high-value chemicals (HVC) that could potentially be recovered from the process represent a considerable op-portunity with multi-billion-dollar commercial value. Overall, coastal marine biorefineries have strong potential for a sustainable green economy and rep-resent a rapid approach for climate change mitigation.
... • Seaweed products might replace products with a higher CO 2 footprint, thereby avoiding emissions (rather than directly contributing to sequestration) in fields such as food, feed, fertilisers, nutraceuticals, biofuels, and bioplastics (World Bank 2016; Lehahn et al. 2016;Duarte et al. 2017). The extent of this mitigation pathway is currently not known. ...
... We adopted the scenario of a 14% annual increase in production to provide an upper limit of the sequestration potential by 2030 and 2050, and we further assume that farming could proceed at this rate of increase without meeting constraints before 2050. An even higher production estimate of 10 billion tonnes dry weight/year was recently proposed (Lehahn et al. 2016), indicating that our estimated upper limit of seaweed production is not unrealistic. ...
Chapter
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The ocean is a dominant feature of our planet, covering 70% of its surface and driving its climate and biosphere. The ocean sustains life on earth and yet is in peril from climate change.
... Our estimate of the globally feasible area for seaweed farming (11,900 Mha) is greater than two previous estimates of 4,800 Mha 11 and 10,000 Mha 10 . These differences may be due to both the greater diversity of seaweed species and uses for seaweed biomass that we have included compared with ref. 10 and our estimation of individual species distributions, rather than estimating for an aggregation of seaweed species 11 . It is important to note that while we have constrained by a depth-contour of 200 m, novel technologies such as free-floating cultivation techniques that do not require access to the benthos 19 may further expand geographic potential. ...
... Australia also shows large potential, in part due to its large EEZ, but also in terms of the high diversity of commercial seaweed species that are present there (Supplementary Table 1.4). Other regions such as parts of Europe, South Korea, China and particularly Malaysia, despite having relatively small EEZs, have a geographically 8,9 , or if global, are limited to a subset of seaweed taxa 10 , or ignore the diversity of seaweed species when mapping the potential spatial extent of seaweed cultivation 11 . Similarly, analyses of the benefits of large-scale seaweed farming (see Supplementary Table 1.1) for global sustainability indicators such as land sparing 12 , greenhouse gas (GHG) emissions reductions and offsetting 11,13,14 and food production 15 have been based on simple projections of future use that ignore the complexities of global markets and current pressure on land use. ...
Article
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Agricultural expansion to meet humanity’s growing needs for food and materials is a leading driver of land-use change, exacerbating climate change and biodiversity loss. Seaweed biomass farmed in the ocean could help reduce demand for terrestrial crops and reduce agricultural greenhouse gas emissions by providing a substitute or supplement for food, animal feed and biofuels. Here we model the global expansion potential of seaweed farming and explore how increased seaweed utilization under five different scenarios that consider dietary, livestock feed and fuel production seaweed usage may affect the environmental footprint of agriculture. For each scenario, we estimate the change in environmental impacts on land from increased seaweed adoption and map plausible marine farming expansion on the basis of 34 commercially important seaweed species. We show that ~650 million hectares of global ocean could support seaweed farms. Cultivating Asparagopsis for ruminant feed provided the highest greenhouse gas mitigation of the scenarios considered (~2.6 Gt CO2e yr−1). Substituting human diets at a rate of 10% globally is predicted to spare up to 110 million hectares of land. We illustrate that global production of seaweed has the potential to reduce the environmental impacts of terrestrial agriculture, but caution is needed to ensure that these challenges are not displaced from the land to the ocean. Seaweed farming could reduce agriculture’s environmental footprint, but its potential is not well-explored yet. This study shows how globally extended aquaculture can reduce terrestrial crops demand and greenhouse gas emissions while providing a substitute or supplement for food, animal feeds and fuel.
... Marine macroalgae, also known as "seaweeds", represent a promising biomass that can address future trends and industry demand, as well as various sustainability issues. Marine macroalgae have been recognized as an alternative for the production of renewable energy, bio-based products and bioactive molecules, owing to their remarkable regeneration properties and high photosynthetic efficiency, as well as the lack of land requirements for growth [1][2][3][4]. Yields in terms of growth potential of seaweeds are around 20 t per hectare per year [5]. ...
... The addition of varying concentrations of E 2 or E 3 in DMSO to a solution of DMSO saturated with commercial oxygen provokes a remarkable decrease in the peak current density ( Figure 13). The substantial diminution in peak current density can be attributed to the decrease in free O 2 ...
Article
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Marine macroalgae biomass is a valuable renewable resource that can be used for the development of bioeconomy through the valorisation of valuable compounds. The aim of the current study is separate macroalgal polysaccharides with bioactive properties from brown macroalgae Fucus spiralis based on a designed biocascading biorefinery approach. Thus, we applied an integrated processing method for the separation of fucoidan and alginate, in addition to characterization through IR spectroscopy and 1H NMR. The bioactivity potential (antioxidant activity using superoxide anion and DPPH radical scavenging analysis) of the two polysaccharides was evaluated, together with DNA binding studies performed though voltametric techniques and electronic spectroscopy titration. In terms of results, functional groups S=O (1226 cm−1), N=S=O (1136 cm−1) and C-O-SO3 (1024 cm−1), which are characteristic of fucoidan, were identified in the first polysaccharidic extract, whereas guluronic units (G) (1017 cm−1) and mannuronic units (M) (872 and 812 cm−1) confirmed the separation of alginate. The DNA binding studies of the isolated polysaccharides revealed an electrostatic and an intercalation interaction of DNA with fucoidan and alginate, respectively. Both antioxidant activity assays revealed improved antioxidant activity for both fucoidan and alginate compared to the standard α-tocopherol.
... However, possible feedstock and process technologies are big challenges and denote the requirements of a sustainable source of biomass. Seaweeds can play an important role as a source of bioenergy and other products (Lehahn et al., 2016), and combat climate change impact (Fig. 8); however, scaling up the large-scale production, industrial input, and sustainability of conversion system still need research trials (Jiang et al., 2016). For example, the widely cultivated seaweed Kappaphycus alvarezii based biorefinery model is developed for the production of various products such as carrageenan, bioethanol, and biogas (Ingle et al., 2018). ...
... Mitigation of such factors needs governmental support in terms of favorable laws, rules, and regulations . Seaweed farming with other types of aquaculture such as integrated multitropic aquaculture or combined aquaculture can be beneficial to tackle the problem of pests in seaweed (Lehahn et al., 2016). ...
Article
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Seaweed cultivation is an emerging sector of food production that can full fill the future food demand of the growing population. Considering the importance, Asia is home to seven of the top ten seaweed-producing nations, and Asian countries contributed 99.1% of all seaweed cultivated for food. Besides, it can reduce the carbon budget of the ocean through seaweed farms and act as a CO 2 sink. In the context of climate change mit-igation, the seaweed culture is the energy crop, and during its entire life cycle can serve as a bio-filter and bio-extractor. The climate change effect can be reduced by farming seaweed on a commercial scale and it will protect the coastal area by decreasing the physical damage through damping wave energy. The seaweed can reduce eutrophication by removing excess nutrients from water bodies and releasing oxygen as a byproduct in return. The cultivation of seaweed plays an important role as the source of bioenergy for full fill the future energy requirement and it will act as clean energy through the establishment of algal biorefinery along with the seaweed cultivation site. Thus, the marine energy industrial sector moves further toward large-scale expansion of this sector by adopting energy devices to offer power for seaweed growth for biofuel operation. The current reviews provides the evidence of seaweed farming methodology adopted by different countries, as well as their production and output. To mitigate climate change by direct measures such as carbon sequestration, eutrophication risk reduction, and bioenergy, as well as through indirect measures like supplying food for cattle and reducing the strain on aquaculture. The US, Japan, and Germany lastly suggest the large-scale offshore commercial farming as a feasible climate change mitigation strategy.
... However, possible feedstock and process technologies are big challenges and denote the requirements of a sustainable source of biomass. Seaweeds can play an important role as a source of bioenergy and other products (Lehahn et al., 2016), and combat climate change impact (Fig. 8); however, scaling up the large-scale production, industrial input, and sustainability of conversion system still need research trials (Jiang et al., 2016). For example, the widely cultivated seaweed Kappaphycus alvarezii based biorefinery model is developed for the production of various products such as carrageenan, bioethanol, and biogas (Ingle et al., 2018). ...
... Mitigation of such factors needs governmental support in terms of favorable laws, rules, and regulations . Seaweed farming with other types of aquaculture such as integrated multitropic aquaculture or combined aquaculture can be beneficial to tackle the problem of pests in seaweed (Lehahn et al., 2016). ...
Article
Seaweed cultivation is an emerging sector of food production that can full fill the future food demand of the growing population. Considering the importance, Asia is home to seven of the top ten seaweed-producing nations, and Asian countries contributed 99.1% of all seaweed cultivated for food. Besides, it can reduce the carbon budget of the ocean through seaweed farms and act as a CO2 sink. In the context of climate change mitigation, the seaweed culture is the energy crop, and during its entire life cycle can serve as a bio-filter and bio-extractor. The climate change effect can be reduced by farming seaweed on a commercial scale and it will protect the coastal area by decreasing the physical damage through damping wave energy. The seaweed can reduce eutrophication by removing excess nutrients from water bodies and releasing oxygen as a byproduct in return. The cultivation of seaweed plays an important role as the source of bioenergy for full fill the future energy requirement and it will act as clean energy through the establishment of algal biorefinery along with the seaweed cultivation site. Thus, the marine energy industrial sector moves further toward large-scale expansion of this sector by adopting energy devices to offer power for seaweed growth for biofuel operation. The current reviews provides the evidence of seaweed farming methodology adopted by different countries, as well as their production and output. To mitigate climate change by direct measures such as carbon sequestration, eutrophication risk reduction, and bioenergy, as well as through indirect measures like supplying food for cattle and reducing the strain on aquaculture. The US, Japan, and Germany lastly suggest the large-scale offshore commercial farming as a feasible climate change mitigation strategy.
... Aquaculture of seaweed has the potential to sequester approximately 1500 tonnes of carbon dioxide per square kilometre, which is equivalent to the annual carbon dioxide emissions of approximately 300 Chinese individuals (Duarte et al. 2017a). Lehahn et al. (2016) demonstrated that the cultivation of seaweeds could completely replace the reliance on fossil fuels for transportation, meet 100% of the future demand for acetone, ethanol, and butanol, provide 5-24% of the demand for proteins and produce biogas that could mitigate 5.1 × 10 7 -5.6 × 10 10 tonnes of carbon dioxide emissions from natural gas use. Jagtap and Meena (2022) reported the carbon sequestration potential of certain seaweeds as follows: Eucheuma spp. ...
... Seaweeds can be converted into high-value products, such as biofuels; consequently, they are considered promising third-generation feedstocks in bioremediation (Wang et al. 2020a). By 2054, biofuels derived from seaweed can replace the demand for fossil fuels in the transportation sector, thereby reducing greenhouse gas emissions (Lehahn et al. 2016). As previously discussed in Sect. ...
Article
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The development and recycling of biomass production can partly solve issues of energy, climate change, population growth, food and feed shortages, and environmental pollution. For instance, the use of seaweeds as feedstocks can reduce our reliance on fossil fuel resources, ensure the synthesis of cost-effective and eco-friendly products and biofuels, and develop sustainable biorefinery processes. Nonetheless, seaweeds use in several biorefineries is still in the infancy stage compared to terrestrial plants-based lignocellulosic biomass. Therefore, here we review seaweed biorefineries with focus on seaweed production, economical benefits, and seaweed use as feedstock for anaerobic digestion, biochar, bioplastics, crop health, food, livestock feed, pharmaceuticals and cosmetics. Globally, seaweeds could sequester between 61 and 268 megatonnes of carbon per year, with an average of 173 megatonnes. Nearly 90% of carbon is sequestered by exporting biomass to deep water, while the remaining 10% is buried in coastal sediments. 500 gigatonnes of seaweeds could replace nearly 40% of the current soy protein production. Seaweeds contain valuable bioactive molecules that could be applied as antimicrobial, antioxidant, antiviral, antifungal, anticancer, contraceptive, anti-inflammatory, anti-coagulants, and in other cosmetics and skincare products.
... Indeed, long-term ecological models that predict macroalgal productivity and seasonal blooms in prone ecosystems Solidoro et al., 1997;Ren et al., 2014;Martins et al., 2007;Port et al., 2015;Brush and Nixon, 2010;Aldridge and Trimmer, 2009;Lavaud et al., 2020;Seip, 1980;Aveytua-Alcázar et al., 2008;Duarte and Ferreira, 1997) or culture models that focus mostly on onshore photobioreactors (Friedlander et al., 1990;Oca Baradad et al., 2019) and offshore cultivation (Broch and Slagstad, 2012;Petrell et al., 1993;Hadley et al., 2015) were developed. These models, which pursue a basic understanding of the thermodynamics of individual algae thalli and photobioreactors (Zollmann et al., 2018;Lehahn et al., 2016;Lee and Ang, 1991;Seip, 1980), provide important tools to predict the productivity and seasonal environmental effects on the seaweed population dynamics. However, such models treat the macroalgae population as a bulk and do not differentiate between ages of individual thalli within the population. ...
... Indeed, long-term ecological models that predict macroalgal productivity and seasonal blooms in prone ecosystems Solidoro et al., 1997;Ren et al., 2014;Martins et al., 2007;Port et al., 2015;Brush and Nixon, 2010;Aldridge and Trimmer, 2009;Lavaud et al., 2020;Seip, 1980;Aveytua-Alcázar et al., 2008;Duarte and Ferreira, 1997) or culture models that focus mostly on onshore photobioreactors (Friedlander et al., 1990;Oca Baradad et al., 2019) and offshore cultivation (Broch and Slagstad, 2012;Petrell et al., 1993;Hadley et al., 2015) were developed. These models, which pursue a basic understanding of the thermodynamics of individual algae thalli and photobioreactors (Zollmann et al., 2018;Lehahn et al., 2016;Lee and Ang, 1991;Seip, 1980), provide important tools to predict the productivity and seasonal environmental effects on the seaweed population dynamics. However, such models treat the macroalgae population as a bulk and do not differentiate between ages of individual thalli within the population. ...
Article
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Ulva is a widespread green algal genus with important ecological roles and promising potential as a seagriculture crop. One of the major challenges when cultivating Ulva is sudden biomass disappearance, likely caused by uncontrolled and unpredicted massive sporulation. However, the dynamics of this process are still poorly understood. In this study, we propose a mathematical model describing the biomass accumulation and degradation of Ulva, considering the potential impact of sporulation inhibitors. We developed a differential equation model describing the time evolution of Ulva biomass. Our model simulates biomass in compartments of different Ulva “age” classes, with varying growth and sporulation rates. Coupled with these classes is a differential equation describing the presence of a sporulation inhibitor, produced and secreted by the algae. Our model mimics observed Ulva dynamics. We present Ulva's biomass accumulation under different initial algae population, age distributions and sporulation rates. Furthermore, we simulate water replacement, effectively depleting the sporulation inhibitor, and examine its effects on Ulva's biomass accumulation. The model developed in this work is the first step towards understanding the dynamics of Ulva growth and degradation. Future work refining and expanding our results should prove beneficial to the ecological research and industrial growth of Ulva.
... This model described the potential for biomass production could be extended 400Km from the shore and classified them into either future deep-or shallow-water provinces. The climatological oceanographic data can be used to analyze the environmental risks which can be controlled to develop futuristic potential offshore biorefineries globally (Lehahn et al. 2016). The problem with the nutrient and light supply can be controlled by establishing huge offshore floating reactors accompanied by external solar energy (sun) which can be used for exploiting photon capture and carbon fixation rates via algal cells to increase biomass yield per unit area. ...
... Since seaweeds possess about 60% of polysaccharides of all bioactive compounds occurring in them (Pereira 2018), most of the value-added products are manufactured using polysaccharides. Seemingly, the enormous application of seaweeds has improved the development of several value-added products of nutraceuticals, functional foods, pharmaceuticals, and cosmeceuticals applications (Lehahn et al. 2016). Moreover, the seaweed-derived biofertilizer approach is a very trending eco-friendly strategy in the field of agriculture (Nabti et al. 2016). ...
Chapter
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Seaweeds or marine macroalgae are emerging as a next-generation sustainable bioresource for food, feed, biochemicals, and several value-added products. Seaweeds are identified as an environmentally friendly feedstock as they have high CO2 sequestration potential and no direct requirement of freshwater, fertilizers, and agricultural land for growth. Earlier the use of seaweeds mainly red and brown was restricted to hydrocolloid production and food applications but in the last decade, significant advancement has been witnessed mainly in the green seaweeds. Currently, the Asian countries are the leaders of seaweed biomass production (more than 99%) followed by some western countries. Researchers across the globe are exploring the potentials of seaweeds for pharmaceuticals, nutraceuticals cosmeceuticals, beverages, fertilizers, and food applications. At present, the growth engineering of seaweeds for land-based or sea cultivation, seaweed biorefinery for extraction of multiple value-added products, and IMTA (Integrated Multitrophic Aquacultural) systems are the thurst area in seaweed biotechnology. This chapter focuses on the recent developments made in the area of seaweed biotechnology.
... Beschikbaarheden in de literatuur die geen recht doen aan de duurzaamheidskaders van het Nederlandse en Europese beleid hebben we in de gepresenteerde tabellen en figuren buiten beschouwing gelaten. Een voorbeeld daarvan is de theoretisch mondiale beschikbaarheid in 2050 aan macro-alg ('zeewier') van ruim 2.000 EJ per jaar die wordt genoemd door Lehahn et al. (2016). 'Technisch-duurzame' beschikbaarheden die laten zien wat er mogelijk is binnen basale duurzaamheidscriteria, zoals het 'food, feed and fibre first principle' en behoud van oerbos, hebben we wel opgenomen. ...
... In vergelijking met microalgen, welke in reactors op het land worden gekweekt, is de teelt van macroalgen minder kapitaal-en energie-intensief, is de potentiële opbrengst hoger en zijn de planten gemakkelijker te oogsten. De productietechnologie van biomassa uit macroalgen zit echter nog in de ontwikkelingsfase, wat inschatting van de potentie bemoeilijkt (Lehahn, et al., 2016). ...
Technical Report
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The Dutch government plans to draw up an integral sustainability framework for assessing all types of biomass and all biomass applications. This CE Delft report feeds into that process and has been used, along with a parallel Joint Fact Finding study (2020), for preparing the Netherlands Environmental Assessment Agency (PBL) report on biomass. This study examines the availability and uses of ‘sustainable biomass’ at two points in the future, 2030 and 2050, and is broad in scope. It covers biomass use as a material (e.g. construction timber), chemical feedstock, energy feedstock/fuel and agricultural input (soil improvement). On the supply side it covers all relevant sources – agricultural, forestry, aquatic – and all types of biomass stream: primary production and various kinds of waste. Data summaries are provided on sectoral demand in the Netherlands in 2030 and 2050 and biomass availability in the Netherlands, the EU28 and global.
... Mathematical models provide a valuable tool for gaining insight into this emerging industry and its potential climate benefits. To date, models of seaweed aquaculture have largely been at the global scale, investigating the extent of suitable area 5,17,50,51 , or its potential as a CO 2 removal strategy 5,17,52,53 . However, global models have significant uncertainties when examined locally, where local and regional environmental and social factors are key to determining the benefits and risks of seaweed aquaculture. ...
Article
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Seaweed farming is widely promoted as an approach to mitigating climate change despite limited data on carbon removal pathways and uncertainty around benefits and risks at operational scales. We explored the feasibility of climate change mitigation from seaweed farming by constructing five scenarios spanning a range of industry development in coastal British Columbia, Canada, a temperate region identified as highly suitable for seaweed farming. Depending on growth rates and the fate of farmed seaweed, our scenarios sequestered or avoided between 0.20 and 8.2 Tg CO2e year⁻¹, equivalent to 0.3% and 13% of annual greenhouse gas emissions in BC, respectively. Realisation of climate benefits required seaweed-based products to replace existing, more emissions-intensive products, as marine sequestration was relatively inefficient. Such products were also key to reducing the monetary cost of climate benefits, with product values exceeding production costs in only one of the scenarios we examined. However, model estimates have large uncertainties dominated by seaweed production and emissions avoided, making these key priorities for future research. Our results show that seaweed farming could make an economically feasible contribute to Canada’s climate goals if markets for value-added seaweed based products are developed. Moreover, our model demonstrates the possibility for farmers, regulators, and researchers to accurately quantify the climate benefits of seaweed farming in their regional contexts.
... As around 70% of the surface of the earth is covered with water, there is a great availability of seaweed that can be used as raw material for the development of bioplastics [72]. The fact that the cultivation of seaweed for its different uses does not compete with other crops or livestock in terms of the need for land or drinking water implies a great advantage for the sector when it comes to taking it into account as a material for the food, cosmetics, pharmaceutical, or biotechnological industry, among others [73], leaving seaweed in an advantageous position compared to other raw materials. However, it is crucial to consider the ecological implications of massive seaweed harvesting. ...
Article
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Seaweed, a diverse and abundant marine resource, holds promise as a renewable feedstock for bioplastics due to its polysaccharide-rich composition. This review explores different methods for extracting and processing seaweed polysaccharides, focusing on the production of alginate plastic materials. Seaweed emerges as a promising solution, due to its abundance, minimal environmental impact, and diverse industrial applications, such as feed and food, plant and soil nutrition, nutraceutical hydrocolloids, personal care, and bioplastics. Various manufacturing techniques, such as solvent casting, injection moulding, and extrusion, are discussed for producing seaweed-based bioplastics. Alginate, obtained mainly from brown seaweed, is particularly known for its gel-forming properties and presents versatile applications in many sectors (food, pharmaceutical, agriculture). This review further examines the current state of the bioplastics market, highlighting the growing demand for sustainable alternatives to conventional plastics. The integration of seaweed-derived bioplastics into mainstream markets presents opportunities for reducing plastic pollution and promoting sustainability in material production.
... Seaweed production in Europe has been steadily increasing in recent years, with countries such as Ireland, Norway, and France at the forefront. A significant potential for the seaweed industry in Europe is predicted because of the large areas suitable for cultivation as well as favorable conditions (Agnesi et al., 2020;Lehahn et al., 2016). Therefore, as part of its efforts towards environmental sustainability and circularity, the European Commission has proposed a significant expansion of seaweed production along the coastline of the continent. ...
... Although not all countries have reported the area under seaweed cultivation, the global areal extent is likely to be under 4000 km 2 , as China, Indonesia and Korea (i.e. 90 % of the world's production) report a cultivated area of 3680 km 2 ( Table 5). Estimates of the total area potentially farmable range from 100,000 to 48,000,000 km 2 globally Froehlich et al., 2019;Lehahn et al., 2016;N'Yeurt et al., 2012;Wu et al., 2023), being mostly offshore or in open ocean waters. These estimates, however, rarely consider growth limitation by micronutrients (e.g., iron, Paine et al., 2023), nor the economic costs or the logistical and technical feasibility of farming in open waters (Coleman et al., 2022;DeAngelo et al., 2022), and should therefore be considered as overestimates of the actual realizable potential. ...
... Seaweeds can be a potential crop to be utilized for the production of various biofuel (Ingle, Polikovsky, 2018;Ingle, Vitkin, 2018;Ingle et al., 2020;Jiang et al., 2016;Lehahn et al., 2016) molecules such as biomethane, bioethanol, syngas, etc. However, the utilization of such seaweed which produced in the wastewater treatment can be controversial. ...
Chapter
Industrial and municipal wastewater contains significant loads of inorganic and organic pollutants that may be hazardous to the environment. Many proposed treatments with bioremediation applications are time not effective although seaweeds may be useful for the elimination of organic pollutants such as nitrates, phosphates, and inorganic pollutants such as heavy metals. The wastewater from industry and domestic areas is generally not saline to grow seaweeds in the long term. Several lab studies carried out by many researchers indicate that the bioremediation by using seaweeds may be efficient and useful in wastewater with specific characteristics. This puts limitations on the use of seaweeds in wastewater treatment. To promote the application of seaweed to wastewater treatment, general growth requirements of seaweed along with possible risk factors must be defined. We suggested a system for the utilization of seaweeds to implement in the wastewater treatment plant located nearby coastal areas to remove all types of pollutants. The worldwide availability of seaweeds can open the door to their bioremediation potential for wastewater treatment efficiently.
... Due to issues around climate change and growing opportunities in renewable energy production, traditional biomass availability has plummeted. For this reason, macroalgae are back on the radar due to their offering as an alternative and sustainable resource in terms of production of bioenergy (Lehahn et al., 2016). ...
Chapter
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This book provides comprehensive insights on existing technologies and up-to-date advances in the field of waste management and treatment using algal-based technologies via different approaches and systems. Coverage includes: Process fundamentals of algae-based wastewater treatment, including metabolic modelling, algal species for resource recovery and algae/bacteria interactions.Critical insights on the status, major challenges and modern engineering solutions in microalgae-related wastewater treatment processes.Case studies for coculturing microalgae with methanotrophs for enhanced nutrient recovery from wastewater.Advanced ways for valorisation of algae-based processes by integrating them with other technologies such as anaerobic digestion, biogas upgradation and bioelectrochemical systems.Up-to-date information on modern biotechnological approaches for deriving value-added bioproducts and biopolymers from microalgae, including biofuels, pigments and nutraceuticals. This is an essential textbook for both undergraduate and graduate students pursuing degrees in environmental sciences, technologies, or engineering. Additionally, the book is equally useful for a broad audience, including researchers, engineers, and policy makers interested in the field of algal systems for waste and wastewater management. The book is also tailored to be used as an advanced manual for practitioners and consultancies working in the field of wastewater treatment and resource recovery. ISBN 9781789063530 (paperback) ISBN 9781789063547 (eBook) ISBN 9781789063554 (ePub)
... They can provide various types of natural pigments, fatty acids, antioxidants, oils, biological components, etc., for industrial purposes. The potential of macroalgae biomass to get converted into valuable feedstock for biorefinery makes it more important in the new era for various products, including biofuels (Ingle et al., 2018;Jiang et al., 2016;Lehahn et al., 2016). ...
... There are vast areas suitable for seaweed and microalgae cultivation (Lehahn, Ingle and Golberg, 2016;Theuerkauf et al., 2019). 15 Reported experiences in Eastern and South-eastern Asia indicate that seaweed and microalgae cultivation can become robust industries that generate benefits and contributions. ...
... The device also collected data during the onshore fertilizing period. In addition, as a backup for cases in which the HOBO devices were damaged or lost in the sea (Table S4), we used two more sources: (1) irradiance data from all experiment periods was extracted from the IMS data base from the Israel Meteorological Services (https:// ims. data. ...
Article
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Offshore macroalgae production could provide an alternative source of biomass for food, materials and energy. However, the offshore environment in general, specifically the Eastern Mediterranean Sea (EMS) offshore, is a high energy and low nutrients environment, thus challenging for macroalgae farming. In this study, we experimentally investigated the impact of season, depth, and pre-cultivation fertilization duration on the growth rates and chemical composition of offshore Ulva biomass, and developed a predictive model tailored to offshore conditions, capable of estimating both biomass growth rate and nitrogen content. Specifically, we measured Ulva biomass growth rate and internal nitrogen in the nitrogen-poor EMS a few kilometers offshore the Israeli coast at various depths and on-shore pre-cultivation fertilization schedules. Based on these data, we constructed a predictive cultivation model of Ulva offshore growth, which allows for the optimization of fertilization requirements for offshore cultivation. This study provides new insights on the effects of seasonality, depth, and pre-cultivation fertilization duration on growth rates and chemical composition of offshore Ulva sp. biomass production.
... Macroalgal biomass production models relate to several main abiotic parameters, including light, temperature, salinity, water flow and nutrients (Harrison & Hurd, 2001;Lehahn et al., 2016;Zollmann, Traugott, Chemodanov, Liberzon, & Golberg, 2019). Among these parameters, nutrients, and specifically nitrogen (N), are the main input stream required for successful macroalgal cultivation, often limiting growth in natural environments (Moore et al., 2013). ...
Article
Macroalgal biomass production models that capture nutrient dynamics, temperature, light and salinity are important for the design and operation of large-scale farms. The goal of this study is to understand how the nitrogen fertilizing regime, relating to dose (μM N week−1), amplitude (μM N) and duration (hours) of fertilization, affects the dynamics of nitrogen content and biomass production of Ulva sp. We hypothesize that the nitrogen fertilizing regime controls the Ulva Nitrogen Use Efficiency (NUE), defined here as the fraction of fertilizer nitrogen that is utilized and allocated to yield N, and, accordingly, also nitrogen assimilation in the biomass and the growth rate. We test this hypothesis by measuring internal nitrogen and biomass weight and by calculat- ing NUE under various fertilization regimes in controlled photobioreactors. Based on these experi- mental data, we developed a biomass productivity model that predicts nitrogen and biomass dynamics temporally over three weeks of cultivation. This study highlights efficient fertilizing regimes and enables the development of a comprehensive understanding of the dynamic relation- ship between external N, internal N and biomass production of Ulva sp. under varying external N levels, which is important for real-world agricultural applications. This study provides a better understanding of the external N-internal N-biomass triangle leading to an improved dynamic cultivation model, enabling better control of nutrient application and biomass production in macroalgal farming for a sustainable marine bioeconomy
... These latter production figures are much higher than net primary production estimates for the natural phytoplankton in the same area, which are around 70 g DW m −2 year −1 (Hansen & Samuelsen, 2009). Lehahn et al. (2016) estimated the global potential of offshore seaweed farming and arrived at a biomass production of 10 11 dry weight tonnes per year over a surface area of about 10 8 km 2 , which is equivalent to 1000 g DW m −2 year −1 . In a recent review on seaweed production, Buschmann et al. (2017) warned that 'great caution should be exercised as some results might be rather unrealistic and what was perceived as high potential may not become a practical reality'. ...
Article
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Abstract The expected increase in global food demand, as a consequence of a rising and wealthier world population, and an awareness of the limits and drawbacks of modern agriculture, has resulted in a growing attention to the potential of the seas and oceans to produce more food. The capture production of presently exploited marine fish stocks and other species has more or less reached its maximum and can only be slightly improved by better management. This leaves four alternative options open to increase marine food production: (1) manipulating the entire food web structure via removal of high trophic level species to allow an increasing exploitation of low trophic level species, (2) harvesting so far unexploited stocks, such as various fish species from the mesopelagic zone of the ocean or the larger zooplankton species from polar regions, (3) low‐trophic mariculture of seaweeds and herbivorous animals, and (4) restoration of impoverished coastal ecosystems or artificially increasing productivity by ecological engineering. In this paper, we discuss these four options and pay attention to missing scientific knowledge needed to assess their sustainability. To assess sustainability, it is a prerequisite to establish robust definitions and assessments of the biological carrying capacity of the systems, but it is also necessary to evaluate broader socio‐economic and governance sustainability.
... These costs may be counteracted by using leftover biomass from food-purposed cultivation. Only 8-12% of cultivated algae is used for food and bioproducts, while the remaining biomass is disposed of as waste (Lehahn et al. 2016). Since sorbent biomass does not need to fulfil the quality requirements expected for algae-based foods, this may represent a window of opportunity to add value to cultivation wastes which are often incinerated or used as fertilizers. ...
Article
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Efficient and sustainable secondary sourcing of Rare-Earth Elements (REE) is essential to counter supply bottlenecks and the impacts associated with primary mining. Recycled electronic waste (E-waste) is considered a promising REE source and hydrometallurgical methods followed by chemical separation techniques (usually solvent extraction) have been successfully applied to these wastes with high REE yields. However, the generation of acidic and organic waste streams is considered unsustainable and has led to the search for “greener” approaches. Sorption-based technologies using biomass such as bacteria, fungi and algae have been developed to sustainably recover REE from e-waste. Algae sorbents in particular have experienced growing research interest in recent years. Despite its high potential, sorption efficiency is strongly influenced by sorbent-specific parameters such as biomass type and state (fresh/dried, pre-treatment, functionalization) as well as solution parameters such as pH, REE concentration, and matrix complexity (ionic strength and competing ions). This review highlights differences in experimental conditions among published algal-based REE sorption studies and their impact on sorption efficiency. Since research into algal sorbents for REE recovery from real wastes is still in its infancy, aspects such as the economic viability of a realistic application are still unexplored. However, it has been proposed to integrate REE recovery into an algal biorefinery concept to increase the economics of the process (by providing a range of additional products), but also in the prospect of achieving carbon neutrality (as large-scale algae cultivation can act as a CO2 sink). Graphical abstract
... • Lack of incentives to increase seaweed quality because in practice, prices paid to producers rarely take quality of the product into account (Mariño et al., 2019). • Seaweed is a promising product to use for biofuels (Lehahn and Alexander, 2016). This can claim areas where seaweed for food production could also have taken place. ...
Article
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Seaweed has been receiving increasing attention as a novel food source worldwide. To optimally develop sea-weed's food provisioning potential, the seaweed value chain requires further understanding. To this end, we used the Food System Approach to review the existing knowledge on seaweed as food source. We identified opportunities , constraints and knowledge needs relevant to fulfilling the potential of seaweed to contribute to food security. Thereby, we especially focus on optimizing and upscaling seaweed production and environmental sustainability. Our review shows that although progress has been made in solving technological issues in seaweed production, major knowledge gaps regarding social and economic factors remain. More attention to these issues can help realize the food potential of seaweed.
... Depth, production in relation to heat, respiration rates, brightness, output exudation, frond breakage, fatality, and a carbon-to-dry-weight conversion factor are considered in the model. The metabolism and growth rate of Ulva sp. were investigated using a mathematical model [78] in which one output file was generated for each month of the year while the model was running on a global 1 • grid. Light intensity (I), temperature (T), salinity (S), dissolved nutrients (nitrate and phosphate), and respiration rate were used to compute the algal growth rate. ...
Article
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In order to meet the growing demand for resources, there is a rising interest in macroalgae cultivation worldwide due to their potential as a source of food, fuel, and bio-products. However, large-scale and sustainable seaweed cultivation has been a persistent challenge. Specific fundamental issues need to be addressed to maximize the benefits of seaweed production. This article reviews a plan for transitioning to an environmentally sustainable aquaculture system incorporating non-toxic nanoparticles. It also provides an overview of genetic enhancement techniques for macroalgae species to realize their potential fully. Additionally, the article discusses the need for advanced tools and concepts to overcome the challenges in seaweed identification and cultivation and emphasizes the importance of a coordinated effort in fundamental and applied research using emerging technologies to ensure long-term practicality.
... Macroalgae growth depends on saturation kinetics by light intensity, ambient dissolved inorganic nutrient concentrations, and temperature (Buschmann et al., 2004). Cultivation uncertainty is exacerbated by stochastic weather and seasonal variability between regions, within years, and between years (Lehahn et al., 2016). This variation in the product might have a major effect on the cost-effectiveness of the technology. ...
Article
The last years have seen the emergence of the bioeconomy. Assessment of these new technologies is a significant challenge. We develop a unique dynamic programming framework to assess the value of the investment in a multi-stage supply chain with the production of bio-feedstock and its processing into multiple outputs. The system allows for adaptive learning in all supply chain stages, which creates a positive learning effect of cooutputs. We apply the framework to macroalgae (seaweed) farming and biorefinery processing into proteins and sugars for the Philippines and Ireland as representatives of developing and developed economies with emerging supply chains. We run Monte Carlo simulations to analyze the uncertainty of learning and prices. The key results indicate that the macroalgae sector that builds on traditional technologies is quite viable. Developing a new algae industry that generates proteins and other high-value products requires significant investment and depends on the dynamics of learning and prices. Even though the production of high-value chemicals is not yet viable, it gains profitability potential from learning of feedstock farming that is currently produced for the lower value application. The learning is much more valuable in feedstock production and processing into proteins than low-value chemicals currently produced (carrageenan). available here: https://www.sciencedirect.com/science/article/pii/S0921800923000447?dgcid=author
... The global potential of offshore biorefineries to provide for biomass for proteins, platform chemicals, and energy was analyzed by 6 , using a metabolism model of the green marine macroalga Ulva, coupled with essential inputs from climatological oceanographic data. Ulva is an interesting biomass for biorefinery as it grows globally and it was already converted to protein, cellulose, starch, ulvan (bioactive polisacharide), fatty acids, minerals, biocrude, biochar, ethanol, biogas 7 , and polyhydroalkanolyes (PHA) 8 , all of which could serve as building blocks for a sustainable bioeconomy 9 . ...
Preprint
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Offshore macroalgae production could provide an alternative source of biomass for food, materials and energy. However, the offshore environment in general, and specifically the Eastern Mediterranean Sea (EMS) offshore, is a high energy and low nutrients environment and thus is challenging for macroalgae farming. This study aims to understand the effects of season, depth, and fertilization duration on growth rates and chemical composition in offshore Ulva biomass production and develop a predictive model suitable to offshore conditions. We hypothesize that offshore Ulva growth rates and chemical composition will follow a seasonal trend and that applying rapid onshore fertilization could refill nutrient storages and enable continuous offshore cultivation. We test this hypothesis by measuring Ulva biomass and internal nitrogen in offshore experiments in the nitrogen-poor EMS a few kilometers offshore the Israeli coast. We construct a predictive cultivation model to estimate N concentrations in the sea during experiments. This study demonstrates the feasibility of growing Ulva sp. offshore the EMS with an onshore nutrient supply and develops a better understanding of seasonal growth dynamics and environmental effects (nitrogen, waves, depth, etc.). Furthermore, the study showcases the applicability of the macroalgae cultivation model in the offshore environment and its potential contribution throughout the whole lifecycle of seaweed cultivation.
... Several biorefinery approaches, particularly for microalgal biomass, have been proposed to create a variety of microalgal-based products sustainably [145]. Macroalgae, sometimes known as seaweeds, are marine microorganisms that are typically grown offshore and prevalent along coastlines [147]. They provide a long-term supply of bio-compounds to produce food, biofuels, biochemical, and numerous other biobased products [148]. ...
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Even though oil, gas, and coal resources might be unavailable after 2040, 2042, and 2112, respectively; 81.7% of the energy is produced from fossil fuels. Experts have established that this level of non-renewable resource use is unsustainable, ecologically unsafe, and critically changing climate patterns. Whereas climate change and biodiversity loss have subjected mankind to significant systemic risks, policymakers have recommended a switch from fossil fuel-based to a biobased economy and reconnecting humans with the biosphere as a way to mitigate these risks. A circular bioeconomy has been suggested as an efficient approach to utilize environmentally safe ecosystem services for socio-ecological development and transformation towards sustainability. The circular bioeconomy provides significant opportunities to achieve 17 SDGs and 134 targets of the Sustainable Development Agenda 2030, and address numerous national and international challenges caused by climate action. In this review, we have highlighted links between circular bioeconomy and internationally agreed SDG targets [particularly SDG 13 (climate action)]; and assessed ecosystem services in a circular biobased economy. A critical synthesis vis-à-vis climate action through circular bioeconomy to assure the sustainability of bioeconomy programmes is herein presented.
... To contribute to such climate goals, seaweed farming must therefore expand tremendously, and in turn contend with large uncertainties in the productivity of different types of seaweed in different places, the net costs of farming, the magnitude of emissions avoided or carbon sequestered, and the potential for undesirable ecological impacts. Recent studies of seaweed farming have examined localized opportunities and dynamics in particular regions 15,16,30 , made rough estimates of the global potential 13,14,31,32 and modelled the Earth system response to gigaton-scale production 19 . Yet the productivity, costs and potential climate benefits of such farming are spatially heterogeneous and scale-dependent, and the key sensitivities and trade-offs important to investors and decision-makers have not been comprehensively evaluated. ...
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Net-zero greenhouse gas (GHG) emissions targets are driving interest in opportunities for biomass-based negative emissions and bioenergy, including from marine sources such as seaweed. Yet the biophysical and economic limits to farming seaweed at scales relevant to the global carbon budget have not been assessed in detail. We use coupled seaweed growth and technoeconomic models to estimate the costs of global seaweed production and related climate benefits, systematically testing the relative importance of model parameters. Under our most optimistic assumptions, sinking farmed seaweed to the deep sea to sequester a gigaton of CO2 per year costs as little as US480pertCO2onaverage,whileusingfarmedseaweedforproductsthatavoidagigatonofCO2equivalentGHGemissionsannuallycouldreturnaprofitof480 per tCO2 on average, while using farmed seaweed for products that avoid a gigaton of CO2-equivalent GHG emissions annually could return a profit of 50 per tCO2-eq. However, these costs depend on low farming costs, high seaweed yields, and assumptions that almost all carbon in seaweed is removed from the atmosphere (that is, competition between phytoplankton and seaweed is negligible) and that seaweed products can displace products with substantial embodied non-CO2 GHG emissions. Moreover, the gigaton-scale climate benefits we model would require farming very large areas (>90,000 km2)—a >30-fold increase in the area currently farmed. Our results therefore suggest that seaweed-based climate benefits may be feasible, but targeted research and demonstrations are needed to further reduce economic and biophysical uncertainties. Potential climate benefits of farming seaweed are large but sensitive to uncertain yields and competition with phytoplankton. Carbon removal by sinking seaweed is much costlier than avoiding emissions by substituting seaweed for land-based crops.
... Moreover, MSD can be cultivated ef ciently without antibiotics, fertilizers, and pesticides (Golberg et al. 2020a), and the global MSD biomass cultivation potential can sustain the industry's rapid growth. For example, the offshore cultivation potential of seaweeds can provide up to a quarter of predicted plant protein demand by 2054 (Lehahn et al. 2016). Roughly 0.3% of the ocean surface would be enough to produce as much biomass as is produced annually in all of global agriculture (Bjerregaard et al. 2016). ...
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This review examines global microalgae, seaweeds, and duckweed (MSD) production status and trends. It focuses on cultivation, recognizing the sector's existing and potential contributions and benefits, highlighting a variety of constraints and barriers over the sector's sustainable development. It also discusses lessons learned and ways forward to unlock the sector's full potential. In contrast to conventional agriculture crops, MSD can rapidly generate large amounts of biomass and carbon sequestration yet does not compete for arable land and potable water, ensuring minimal environmental impacts. Moreover, MSD's applications are ubiquitous and reach almost every industrial sector, including ones essential to meeting the increasing needs of human society, such as foods, pharmaceuticals, and chemicals. To this end, the growing public awareness regarding climate change, sustainable food, and animal welfare yields a significant shift in consumer preference and propels the demand for MSD. In addition, once governments usher in durable and stable carbon policies, the markets for MSD are likely to increase severalfold. Expected final online publication date for the Annual Review of Resource Economics, Volume 14 is October 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Due to their autotrophic nature, algae capture large quantities of CO2 from the atmosphere and convert it to chemical energy in the form of biomolecules and cell mass for various applications. Such bio-based CO2 capture plays an important role in global carbon neutrality, while making innovative and sustainable food and industrial products for human and animal use. This review broadly illustrates the total CO2 emissions of the Southeast Asian region, named as the Association of Southeast Asian Nations (ASEAN), while estimating CO2 capture by regional commercial algae. Among all these nations, the top CO2 emitter in the ASEAN region is Indonesia (625 Mt yr⁻¹) followed by Vietnam (311 Mt yr⁻¹), Thailand (289 Mt yr⁻¹), Malaysia (249 Mt yr⁻¹), the Philippines (154 Mt yr⁻¹), Singapore (52 Mt yr⁻¹), Myanmar (49 Mt yr⁻¹), Cambodia (16 Mt yr⁻¹), Laos and Brunei (7 Mt yr⁻¹). Indonesia is also ranked first in commercial algae production (9918 400 tons yr⁻¹), followed by the Philippines (1500 326 tons yr⁻¹) and Malaysia (188 110 tons yr⁻¹). Similarly, the highest estimated algal CO2 capture is made by Indonesia (11 327 817 tons yr⁻¹) followed by the Philippines (1705 871 tons yr⁻¹) and Malaysia (214 279 tons yr⁻¹), with other ASEAN countries having negligible algal CO2 capture due to either low algae production or a lack of data. The ASEAN region may play a pivotal role in the bio-capture of CO2 with the help of the phytoplanktonic aquaculture industry for value-added products. The rapid emergence of the algal industry in the ASEAN region was due to increased global demand for carrageenophyte seaweeds (98.63% of global), such as Eucheuma sp., from Indonesia and Kappaphycus alvarezii from Malaysia and the Philippines. Due to its tropical climate, high aquatic biodiversity, sufficient water and nutrient resources, and long coastlines, the ASEAN regional governments took prompt action and implemented policies for increased seaweed industry in the region. Conclusively, it is desirable to further strengthen the algal industry in these regional countries for useful products and efficient CO2 capture.
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This study introduces an ocean-based carbon dioxide removal (CDR) approach: Nearshore Macroalgae Aquaculture for Carbon Sequestration (N-MACS). By cultivating macroalgae in nearshore ocean surface areas, N-MACS aims to sequester CO2 with subsequent carbon storage. Utilizing an Earth System Model with intermediate complexity (EMIC), we explore the CDR potential of N-MACS alongside its impacts on the global carbon cycle, marine biogeochemistry and marine ecosystems. Our investigations unveil that coastal N-MACS could potentially sequester 0.7 to 1.1 GtC yr−1. However, it also significantly suppresses marine phytoplankton net primary productivity because of nutrient removal and canopy shading, counteracting approximately 30% of the N-MACS CDR capacity. This suppression of surface NPP, in turn, reduces carbon export out of the euphotic zone to the ocean interior, leading to elevated dissolved oxygen levels and diminished denitrification in present-day oxygen minimum zones. Effects due to harvesting-induced phosphorus removal continue for centuries even beyond the cessation of N-MACS.
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Abrupt sunlight reduction scenarios such as a nuclear winter caused by the burning of cities in a nuclear war, an asteroid/comet impact or an eruption of a large volcano inject large amounts of particles in the atmosphere, which limit sunlight. This could decimate agriculture as it is practiced today. We therefore need resilient food sources for such an event. One promising candidate is seaweed, as it can grow quickly in a wide range of environmental conditions. To explore the feasibility of seaweed after nuclear war, we simulate the growth of seaweed on a global scale using an empirical model based on Gracilaria tikvahiae forced by nuclear winter climate simulations. We assess how quickly global seaweed production could be scaled to provide a significant fraction of global food demand. We find seaweed can be grown in tropical oceans, even after nuclear war. The simulated growth is high enough to allow a scale up to an equivalent of 45% of the global human food demand (spread among food, animal feed, and biofuels) in around 9–14 months, while only using a small fraction of the global ocean area. The main limiting factor being the speed at which new seaweed farms can be built. The results also show that the growth of seaweed increases with the severity of the nuclear war, as more nutrients become available due to increased vertical mixing. This means that seaweed has the potential to be a viable resilient food source for abrupt sunlight reduction scenarios.
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To address expanding issues related to global climate change and rising conventional fuel prices, bioethanol stands to be a viable green resource as an eco-fuel to fulfil power requirements for transport. The search for third-generation bioethanol feedstock made from marine algae, which is sustainable as a feedstock for bioethanol and has positive effects on both the environment and food security. The current review presents a critical analysis and gives a full description of the sequential method for producing bioethanol from macroalgae and derived rejects, and recent advances in the production of biofuels using genetic engineering. The economic viability of algae-derived biofuel is dependent on production costs, which might be reduced by creating valuable secondary by-products, which is the goal of current algal biofuel research. Clean energy is the primary amenity and making it affordable is one of the goals of sustainable development. Achieving this with local populations through skill development and training to contribute towards Sustainable Development Goals 1 and 7 has been explained. Future technologies will harness the cost-effectiveness of sustainable bioethanol by having the capability for maximal extraction capacity and minimal downstream processing utilizing low-cost feedstock.
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Marine macroalgae are an attractive source of alternative protein. However, protein extraction from macroalgae is challenging. In this work, we investigated a combination of enzymatic cell wall degradation and high voltage Pulsed Electric Fields (PEF), to enhance yields of water-soluble-protein extraction from the green marine macroalga Ulva sp. The combined process showed a considerably higher protein extraction yield (19.6 ± 0.33%) compared to that of PEF alone (10.8 ± 0.37%) and enzyme pretreatment alone (9.7 ± 0.42%). Moreover, the water-soluble-protein extract obtained by PEF, which followed enzymatic cell wall degradation, had significant antioxidant activity. These results indicate that PEF combined with enzymatic pretreatment could contribute to protein extraction yields from Ulva sp., as a part of sustainable seaweed biorefinery. Industrial relevance Although several previous works reported on methods for protein extraction from seaweeds for food application, the commercialization of the seaweed proteins is challenging due to multiple challenges in the extraction process development. In this work we show that a combination of enzymes for cell wall degradation with high voltage pulsed electric fields for membrane permeabilization lead to higher yields of water-soluble proteins. Both enzyme treatment and PEF are scalable processes, which do not modify proteins chemically, potentially leading to higher quality of the extract in comparison to standard alkaline extraction with a need to treat chemical waste.
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Macroalgae (or seaweed) aquaculture can potentially provide many ecosystem services, including climate change mitigation, coastal protection, preservation of biodiversity and improvement of water quality. Nevertheless, there are still many constraints and knowledge gaps that need to be overcome, as well as potential negative impacts or scale-dependent effects that need to be considered, before macroalgae cultivation in Europe can be scaled up successfully and sustainably. To investigate these uncertainties, the Expert Working Group (EWG) on Macroalgae was established. Its role was to determine the state of knowledge regarding the potential of macroalgae culture in providing climate-related and other ecosystem services (ES) and to identify specific knowledge gaps that must be addressed before harvesting this potential. The methodological framework combined a multiple expert consultation with Delphi process and a Quick Scoping Review (QSR). To analyse the outcome of both approaches, the EWG classified the findings under the categories Political, Environmental, Social, Technical, Economic and Legal (PESTEL approach) and categorised the ES based on the CICES 5.1 classification.
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New approaches are needed for land-based cultivation of macrophytic red algae that reduce costly aeration requirements for biomass suspension and enable high-density cultivation. The goal of this study was to demonstrate the high-density cultivation of the carbohydrate-rich macrophytic red alga Gracilaria vermiculophylla on vertical arrays of panels deployed in an open channel raceway configuration similar to those developed for mass cultivation of microalgae. A clonal culture of G. vermiculophylla, consisting of branched, cylindrical thallus tissues of 8–10 cm length, was mechanically blended using a Waring blender into 2–3 cm fragments and then fluidically injected onto a 3 mm polypropylene mesh support. Immobilized G. vermiculophylla mesh panels were spaced 6.5 cm apart and aligned parallel to flowing seawater medium at nominal bulk velocity of 20 cm s⁻¹ in a 100 L raceway pond of 20 cm liquid depth. This raceway was equipped with real-time measurement of CO2 concentration in the inlet and outlet gas for determination of CO2 uptake dynamics. Specific rates for CO2 uptake became saturated at 8000 ppm CO2. To match CO2 demand by the biomass under nutrient-replete conditions at 21 °C, the inlet gas CO2 was increased from 1000 to 4000 ppm (day 7–14), and then to 8000 ppm (day 14–23) at 0.010 L gas L⁻¹ liquid min⁻¹ gas flow. Over the 23 day cultivation, biomass on the panel increased by a factor of 48, with final biomass loading exceeding 10 kg FW m⁻² panel area, and cumulative CO2 capture of 65%. The cumulative average areal productivity within the panel zone of the raceway exceeded 60 g AFDW m⁻² day⁻¹, and final biomass density nearing 7.2 g AFDW L⁻¹ (47 g FW L⁻¹) was achieved after 23 days. Overall, these outcomes demonstrate the potential for land-based raceway cultivation of clonal red macroalgae of present and future commercial significance.
Chapter
Important advancements in seaweed production have driven the search for potential alternative molecules with great biotechnological interest. Several seaweed species have been cultivated worldwide and are exploited as a source of platform chemicals and specialty molecules such as polysaccharides. Seaweed polysaccharides have presented several applications in the industrial sector, mainly due to their capacity to form gels and viscous solutions. This chapter highlights the progress in seaweed polysaccharides production, as well as its potential, chemical structure, and biological activity. Furthermore, some economic aspects and commercial importance are summarized and discussed. We also address advanced technologies in massive seaweed production and their impact on the industrial scenario. The topics here studied include some of the main challenges of sustainable production of seaweed-derived polysaccharides.KeywordsSeaweed-derived polysaccharideMacroalgaeChallengesMarketOffshore cultivationIndustry
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This report has been commissioned by Sustainable Energy Ireland in order to provide an overview of marine algae as an energy resource, from either macroalgae or microalgae. It is also required to assess the potential resource in Ireland, determine the level of activity and identify research and development knowledge gaps. A biofuels obligation scheme is being proposed in Ireland which will see a percentage of fossil-fuels for transport being displaced by biofuels, ultimately reaching 10% (on an energy basis) by 2020. The achievement of this ambitious target is contingent on finding and commercialising new resources for transport fuel, as current feedstocks are not sufficient to meet the target. Microalgae are being widely researched as a fuel due to their high photosynthetic efficiency and their ability to produce lipids, a biodiesel feedstock. Macroalgae (or seaweeds) do not generally contain lipids and are being considered for the natural sugars and other carbohydrates they contain, which can be fermented to produce either biogas or alcohol-based fuels. A supply-chain analysis was carried out for both macroalgae and microalgae, technologies identified and research topics proposed to evaluate commercialisation potential of these resources for energy. For the purposes of this report tentative roadmaps based on high, medium and low scenarios are hypothesised for development of these resources by 2020.
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Artificial upwelling, as a geoengineering tool, has received worldwide attention because it may actualize ocean fertilization in a sustainable way, which could potentially alleviate the pressures on the fish stocks and human-driven climate change in the ocean. We reviewed the current knowledge on the development of an artificial upwelling system and its potential environmental effects. Special attention was given to the research progress on the air-lift concept artificial upwelling by Zhejiang University. The research on artificial upwelling over the past few decades has generated a range of devices that have been successfully applied in the field for months. Based on field experiments and the associated modeling results, part of them reported positive effects on increasing primary production and enhancing CO2 sequestration. However, as a significant disturbance to the environment, especially for large-scale applications, the uncertainties related to the potential effects on ecosystem remain unsolved. Zhejiang University has overcome the technical challenges in designing and fabricating a robust and high efficiency artificial upwelling device which has been examined in two field experiments in Qiandao Lake and one sea trial in the East China Sea. It was investigated that cold and hypoxic deep ocean water (DOW) could be uplifted to the euphotic layer, which could potentially change the nutrient distribution and adjust the N/P ratio. Both simulation and field experiments results confirmed that utilizing self-powered energy to inject compressed air to uplift DOW was a valid and efficient method. Therefore, further field-based research on artificial upwelling, especially for long-term field research is required to test the scientific hypothesis. © 2015 Science China Press and Springer-Verlag Berlin Heidelberg
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This publication was produced in recognition that there is a growing need to increasingly transfer land-based/coastal aquaculture production systems further offshore as a result of the expected increases in human population, competition for access to land and clean water needed to increase the availability of fish and fishery products much needed for human consumption. Mariculture, in particular offshore, offers significant opportunities for sustainable food production and development of many coastal communities, especially in regions where the availability of land, near shore space and freshwater are limited. This publication provides, for the first time, measures of the status and potential for offshore mariculture development from a spatial perspective that are comprehensive of all maritime nations and comparable among them. It also identifies nations that are not yet practicing mariculture that have a high offshore potential. The underlying purpose of this document is to stimulate interest for detailed assessments of offshore mariculture potential at national levels. Remote sensing for the sustainable development of offshore mariculture is included as Annex 3 to this publication in recognition of the importance of remote sensing as a source of data for spatial analyses to assess potential for offshore mariculture, and also for zoning and site selection as well as for operational remote sensing to aid mariculture management.
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Macro algal seaweeds are a promising feedstock for biofuels production. Yet, their relatively low fermentable carbohydrate content and the inefficient methods used for their conversion hamper their utilization. The optimized production of Ulva rigida co-cultured with fed-fish in an offshore mariculture (fish cages) system is reported. Enhanced production of biomass with elevated content of desired carbohydrates is achieved. The farmed biomass was further converted to bioethanol by a one-step sonication assisted SSF process. An ethanol yield of 16 wt. % (based on the dry weight of algae) is obtained.
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Obesity is a major global health problem. However, current therapeutic strategies for obesity are limited. Obesity results from an imbalance between energy intake and energy expenditure, and the treatment of obesity is based on the correction of this metabolic imbalance. Anti-obesity drugs can shift this balance in a favorable way by reducing food intake, altering metabolism, and by increasing energy expenditure. There is a growing consensus that pharmacotherapy is appropriate for many individuals who are unable to lose weight through less intensive measures. However, side effects may ensue phamacotherapy for obesity. Only two drugs (sibutramine and orlistat) are currently approved for the long-term treatment of obesity. Sibutramine inhibits the reuptake of serotonin and norepinephrine. Orlistat works by blocking the pancreatic lipase. However, phamarcotherapy may not be the ultimate resolution for obesity management. Because the underlying pathophysiology in each individual varies in many aspects, it is recommended to provide individualized and tailored medication in addition to other anti-obesity supportive treatments.
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The conversion processes of macroalgae for biofuels can be divided into thermochemical (dry) and microbiological (wet) processes. The chemical composition of macroalgae together with the pre-treatment method, conversion conditions, and the characteristics of the microbes involved (wet processes) determine the yield and the properties of the biofuel produced. Macroalgae are often rich in carbohydrates, and therefore well suited for biogas, biobutanol and bioethanol productions. The content of triacylglycerols (TAGs) is the best indicator for the suitability of the alga for biodiesel production. TAGs have a high conversion rate to biodiesel, high percentage of fatty acids, and they lack phosphorus, sulfur and nitrogen. Macroalgae can have high metal concentrations, which can have an impact on conversion processes: metals may inhibit or catalyse the processes. High sulfur (especially in green algae) and nitrogen contents are also characteristic to macroalgae, and may be problematic in the production of biogas (NH3-toxicity) and the use of the oil and biodiesel (high concentrations of H2S and NOx-compounds). Macroalgae have proven to be suitable material for conversion processes, but further optimization of the processes is needed. At present, macroalgae are not economically, or in many cases not even environmentally, sustainable material when the whole production chain is considered. In this review we summarize information on the chemical composition of macroalgae in a prospect of biofuel production, and the current situation in the field of macroalgal-based biofuel production.
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Filamentous species of Ulva are ideal for cultivation because they are robust with high growth rates and maintained across a broad range of environments. Temperate species of filamentous Ulva are commercially cultivated on nets which can be artificially 'seeded' under controlled conditions allowing for a high level of control over seeding density and consequently biomass production. This study quantified for the first time the seeding and culture cycle of a tropical species of filamentous Ulva (Ulva sp. 3) and identified seeding density and nursery period as key factors affecting growth and biomass yield. A seeding density of 621,000 swarmers m-1 rope in combination with a nursery period of five days resulted in the highest growth rate and correspondingly the highest biomass yield. A nursery period of five days was optimal with up to six times the biomass yield compared to ropes under either shorter or longer nursery periods. These combined parameters of seeding density and nursery period resulted in a specific growth rate of more than 65% day-1 between 7 and 10 days of outdoor cultivation post-nursery. This was followed by a decrease in growth through to 25 days. This study also demonstrated that the timing of harvest is critical as the maximum biomass yield of 23.0±8.8 g dry weight m-1 (228.7±115.4 g fresh weight m-1) was achieved after 13 days of outdoor cultivation whereas biomass degraded to 15.5±7.3 g dry weight m-1 (120.2±71.8 g fresh weight m-1) over a longer outdoor cultivation period of 25 days. Artificially seeded ropes of Ulva with high biomass yields over short culture cycles may therefore be an alternative to unattached cultivation in integrated pond-based aquaculture systems.
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The increasing demands placed on natural resources for fuel and food production require that we explore the use of efficient, sustainable feedstocks such as brown macroalgae. The full potential of brown macroalgae as feedstocks for commercial-scale fuel ethanol production, however, requires extensive re-engineering of the alginate and mannitol catabolic pathways in the standard industrial microbe Saccharomyces cerevisiae. Here we present the discovery of an alginate monomer (4-deoxy-l-erythro-5-hexoseulose uronate, or DEHU) transporter from the alginolytic eukaryote Asteromyces cruciatus. The genomic integration and overexpression of the gene encoding this transporter, together with the necessary bacterial alginate and deregulated native mannitol catabolism genes, conferred the ability of an S. cerevisiae strain to efficiently metabolize DEHU and mannitol. When this platform was further adapted to grow on mannitol and DEHU under anaerobic conditions, it was capable of ethanol fermentation from mannitol and DEHU, achieving titres of 4.6% (v/v) (36.2 g l(-1)) and yields up to 83% of the maximum theoretical yield from consumed sugars. These results show that all major sugars in brown macroalgae can be used as feedstocks for biofuels and value-added renewable chemicals in a manner that is comparable to traditional arable-land-based feedstocks.
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Microbial activity is a fundamental component of oceanic nutrient cycles. Photosynthetic microbes, collectively termed phytoplankton, are responsible for the vast majority of primary production in marine waters. The availability of nutrients in the upper ocean frequently limits the activity and abundance of these organisms. Experimental data have revealed two broad regimes of phytoplankton nutrient limitation in the modern upper ocean. Nitrogen availability tends to limit productivity throughout much of the surface low-latitude ocean, where the supply of nutrients from the subsurface is relatively slow. In contrast, iron often limits productivity where subsurface nutrient supply is enhanced, including within the main oceanic upwelling regions of the Southern Ocean and the eastern equatorial Pacific. Phosphorus, vitamins and micronutrients other than iron may also (co-)limit marine phytoplankton. The spatial patterns and importance of co-limitation, however, remain unclear. Variability in the stoichiometries of nutrient supply and biological demand are key determinants of oceanic nutrient limitation. Deciphering the mechanisms that underpin this variability, and the consequences for marine microbes, will be a challenge. But such knowledge will be crucial for accurately predicting the consequences of ongoing anthropogenic perturbations to oceanic nutrient biogeochemistry.
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A thorough of macroalgae analysis as a biofuels feedstock is warranted due to the size of this biomass resource and the need to consider all potential sources of feedstock to meet current biomass production goals. Understanding how to harness this untapped biomass resource will require additional research and development. A detailed assessment of environmental resources, cultivation and harvesting technology, conversion to fuels, connectivity with existing energy supply chains, and the associated economic and life cycle analyses will facilitate evaluation of this potentially important biomass resource.
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The oceanic distributions of nutrients and patterns of biological production are controlled by the interplay of biogeochemical and physical processes, and external sources. Biological and chemical processes lead to the transformation of nutrients between inorganic and organic forms, and also between dissolved and particulate forms. Physical processes redistribute nutrients within the water column through transport and mixing. The combined role of biogeochemical and physical processes is reflected in the observed distributions of nitrate, phosphate and silicate (macro-nutrients). These distributions broadly reflect those of classical water masses, as defined by temperature and salinity, highlighting the important role of physical transport. However, there are also significant differences between the nutrient and water-mass distributions, notably with nutrients showing stronger vertical and basin-to-basin contrasts. Biological production leads to these greater nutrient contrasts with inorganic nutrients consumed and converted to organic matter in the surface, sunlit ocean. A small fraction of the organic matter in this euphotic zone is exported to depth, driven by the gravitational sinking of particles and subduction of dissolved organic matter. This organic fallout is eventually remineralised leading to an accumulation of inorganic nutrients in deeper and older water masses.
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Nutrient loading to coastal bay ecosystems is of a similar magnitude as that to deeper, river-fed estuaries, yet our understanding of the eutrophication process in these shallow systems lags far behind. In this synthesis, we focus on one type of biotic feedback that influences eutrophication patterns in coastal bays-the important role of primary producers in the 'coastal filter'. We discuss the 2 aspects of plant-mediated nutrient cycling as eutrophication induces a shift in primary producer dominance: (1) the fate of nutrients bound in plant biomass, and (2) the effects of primary producers on biogeochemical processes that influence nutrient retention. We suggest the following generalizations as eutrophication proceeds in coastal bays: (1) Long-term retention of recalcitrant dissolved and particulate organic matter will decline as seagrasses are replaced by algae with less refractory material. (2) Benthic grazers buffer the early effects of nutrient enrichment, but consumption rates will decline as physico-chemical conditions stress consumer populations. (3) Mass transport of plant-bound nutrients will increase because attached perennial macrophytes will be replaced by unattached ephemeral algae that move with the water. (4) Denitrification will be an unimportant sink for N because primary producers typically outcompete bacteria for available N, and partitioning of nitrate reduction will shift to dissimilatory nitrate reduction to ammonium in later stages of eutrophication. In tropical/subtropical systems dominated by carbonate sediments, eutrophication will likely result in a positive feedback where increased sulfate reduction and sulfide accumulation in sediments will decrease P adsorption to Fe and enhance the release of P to the overlying water.
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