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Marine microalgae are the natural source of proteins and oils in the marine food web. Here is described a method for saving 30% of the world fish catch by producing fishmeal and fish oil replacement products from marine microalgae.
Fishmeal and fish oil are unique nutritional ingredients, produced by rendering ~30% of the wild fish catch. Annual production has been limited since the 1980s, when global fish catch reached maximum sustainable yield, at 5-6 million tons’ fishmeal and 1 million tons’ fish oil.
Demand has been increasing, especially as an essential ingredient in aquafeeds. Fishmeal offers a high-protein (60– 65%) ingredient, with a balanced amino acid profile.
Fish oil has a high level of n-3 highly unsaturated fatty acids (HUFA), which promote optimal growth and health. Prices of both commodities have more than tripled in the past 10 years. The aquaculture industry is the fastest-growing sector of food production in the world, growing at 8.8% per year from 1980 to 2010.
“The question is, where will fishmeal and fish oil come from in the future? The present supply is unsustainable. Replacements have been sought, but no satisfactory replacement products exist.”
The best alternate sources of protein currently available – soybean protein concentrate, wheat gluten, or corn gluten still need to be supplemented with essential amino acids like methionine and lysine. Plant protein meals also contain anti-nutritional components which compromise digestion.
“Replacements for fish oil are more problematic, as direct sources of n-3 HUFA are not produced in sufficient quantities by terrestrial plants.”
The best sources of protein and oil for the diets of marine animals are marine microalgae, the very base of the marine food chain. Marine microalgae have a balanced amino acid profile, and some of them are the natural source of n-3 HUFA.
Microalgae would be a commercial replacement for the highest quality fishmeal and fish oil but the cost of production has been considered too high. Here we present a study that builds on recent advancements in large-scale algae productivity.
Methods
The algae production system modeled in this study (Figure 1) is based on the cultivation facility presented by Beal et al. and Huntley et al., but is located in Thailand and modified to include a total lipid extraction using ethanol and hexane.
The cultivation facility consists of a hybrid system of photobioreactors (PBR) and raceway ponds for cultivation of Desmodesmus sp. The facility includes 92 ha of sunlit cultivation area and 114,000 m3 of growth volume. Seawater is supplied from a 50-m pipeline and a gravity-based canal system typical of Thailand aquaculture (requiring 0.9 kJ/L for pumping).
The total capital cost for the facility is $29.3 M. All capital costs were adjusted to Thailand prices using a geographic cost modifier of 0.58 with respect to costs in the U.S. as determined previously by Beal et al. Labor requirements to grow and process the algae are based on Beal et al., but adapted to Thailand labor costs.
Results
Techno-economic Results
The Net Present Value (NPV) of the facility after 30 years of operation was determined to be $26.9 M. This profit represents a 92% return on investment. During the first 10 years of operation, when loan payments and depreciation are applied, the cumulative discounted cash flow increases from −$11.7 M to $9.5 M.
From year 11–30, annual gross revenue ($10.7 M) exceeds annual costs ($4.1 M) by $6.6 M, resulting in $1.3 M of annual tax payments and a steady increase in cumulative discounted cash flow to $26.9 M. The largest contributors to the capital costs ($29.3 M) include pond liner ($8.4 M), pipes ($3.8 M), pumps ($2.8 M), ring dryer ($1.6 M), filter press ($1.2 M), extraction equipment ($1.2 M), and buildings ($1.3 M).
When summing other costs over the entire 30-year facility lifetime, the largest costs include: taxes ($45.9 M), carbon dioxide ($38.6 M), PBR plastic ($15.0 M), labor ($11.1 M), electricity for circulating growth volumes ($10.7 M), heat ($8.6 M), loan interest ($8.2 M), insurance ($7.8 M), maintenance ($7.8 M), ammonia ($7.3 M), and water supply electricity ($6.3 M), for a total of $168 M.
Revenues from algae oil (fish oil replacement) and residual algal biomass (fishmeal replacement) over the 30-year facility life are $126 M and $197 M, respectively.
EROI Results
The Energy Return On Investment (EROI) for the facility in this study is 0.69, which indicates that more energy is expended than generated. The largest energy expenditures are associated with carbon dioxide acquisition (44%), heat for extraction and drying (24%), electricity for pond circulation (9%), and electricity for water supply (7%) (Table 1).
As shown in Figure 2, the algal products modeled in this study outperform many other protein sources with respect to EROI. Seafood, in particular, has a very low EROI (0.03), which indicates that replacing fish oil and fishmeal with algal biomass could provide significant primary energy savings.
However, the terrestrial feed crops of corn and soybeans have a significantly higher EROI than the algae products in this study. Unlike algae, terrestrial crops do not require external carbon supply or continuous mixing during cultivation, and the drying requirement is much lower than for algal biomass.
As a result, the superior areal productivity of algae in comparison to terrestrial crops is offset by the carbon and energy demands required for production.
GHG Results
The Life-cycle greenhouse gas (GHG) impact of algal biomass in this production model is 3.96 kg of CO2e per kg of algal biomass (including oil and meal fractions).
Similar to the energy impacts, most GHG emissions are associated with upstream impacts for carbon dioxide (56% of total) and heat produced from natural gas (18% of total). The GHG emissions can be compared with soybeans, which can be considered as a reference scenario.
“The average GHG impact of soybeans sold on the global market, according to ecoinvent 3.2, is 3.90 kg CO2e/ kg soybeans. This is comparable to the GHG emissions calculated here for microalgae.”
However, the global number for soybeans is an average of soybean production in several regions and GHG emissions are highly affected by deforestation rates, resulting in a wide range from 0.39 kg CO2e/kg soybean with no deforestation to 5.78 kg CO2e/kg soybean with high deforestation.
The microalgae would then be environmentally competitive only if substituting soybeans produced in regions with high deforestation rates.
Discussion
To replace Thailand’s current fishmeal production with algae meal would require from 98 to 127 such facilities, on a total land area about 10,900 to 14,100 ha. One hundred such facilities (11,100 ha) would produce 0.28 million tons yr−1 of protein, comparable to 0.40 million tons yr−1 of fishmeal.
This amount of land is currently available in Thailand; as of 2016, more than 750,000 ha were under cultivation for oil palm in Thailand. The 11,100 ha required for 100 algae production facilities represent only 1.5% of the land dedicated to oil palm.
“Such an industry would require a capitalization of $3.0 billion and would yield annual net income of $0.66 billion on annual sales of $1.0 billion.”
On a global scale, replacement of fishmeal by algae meal would need about ten times more capital and land, for a total of $30 billion and 111,000 ha.
Granted that the algae facilities are not likely to all be located in Thailand, despite the modest amount of land required, we presume that enough land can be found in comparable environments – tropical locations where the cost of capital and labor are comparable to those in Thailand, or perhaps even more favorable.
Global net income of $6.5 billion on sales of $10 billion await players in this new industry, which is poised to grow quickly.
“Algae production is a far more sustainable industry than continuing to harvest 30% of the world fish catch for fishmeal and fish oil at everincreasing cost. The release in fishing pressure could have a dramatically favorable effect on marine ecosystems.”
The fishes that are caught for rendering into fish oil and fishmeal are typically small, primarily herbivorous fish such as anchovies and menhaden. By not fishing for these fish we leave a huge food resource behind that fuels the production of fishes at higher trophic levels, including finfishes like tuna and salmon that are currently limited in supply.
This would reverse the trend of fishing down the food web and would go a long way towards restoring sustainable global fisheries.
Conclusion
A viable commercial technology is presented for producing marine microalgae to replace the unsustainable supply of fishmeal and fish oil.
In Thailand alone, which produces about 10% of the current world supply, an investment of $3.0 billion on only 11,100 hectares, roughly 1.5% of the land now dedicated to oil palm production, would yield annual net income of $0.65 billion on sales of $1.0 billion.
The global market would be ten times more profitable. If microalgae were used to replace fishmeal and fish oil globally, the effect would be to remove 30% of fishing pressure at the lower end of the food web and would contribute to a restoration of marine ecosystems.
This informative version of the original article is sponsored by REEF
This is a summarized version developed by the editorial team of Aquaculture Magazine based on the review article titled “MARINE MICROALGAE COMMERCIAL PRODUCTION IMPROVES SUSTAINABILITY OF GLOBAL FISHERIES AND AQUACULTURE” developed by: COLIN M. BEAL – B&D Engineering and Consulting LLC and Pacific Aquaculture & Coastal Resources Center; LÉDA N. GERBER – Pacific Aquaculture & Coastal Resources Center; SUPIS THONGROD – Thai Union Feedmill Co., Ltd.; WUTIPORN PHROMKUNTHONG – Prince of Songkla University; VISWANATH KIRON, Nord University – JOE GRANADOS – Pacific Aquaculture & Coastal Resources Center; IAN ARCHIBALD – Pacific Aquaculture & Coastal Resources Center and Cinglas Ltd; CHARLES H. GREENE – Pacific Aquaculture & Coastal Resources Center and Cornell University; MARK E. HUNTLEY – Pacific Aquaculture & Coastal Resources Center and Cornell University.
The original article was published on OCTUBRE, 2018, through NATURE. The full version, including tables and figures, can be accessed online through this link: DOI:10.1038/s41598-018-33504-w
