The term algae refers to a large group of mainly photosynthetic organisms that range in size from unicellular microalgae to vast multicellular macroalgae that can grow up to 70 m in length. Some 11,000 species of red, brown, and green seaweed are distributed across the planet and their diversity helps explain the lack of a conclusive definition for algae. Algae have been used as a source of food for centuries in Asia, while in Europe algae have historically been used mainly as animal feed, fertilizer for crops, and biomass for fuel, but interest in algae for human nutrition is increasing. About 200 species are used for human consumption, most of which are grown wild—less than 20 species are cultivated—and just six species are responsible for 90% of production. In her keynote address on the opening day of the conference, Pi Nyvall Collen from the Olmix Group, pointed to some of the positive impacts of seaweed production. In the sea these include mitigating the impact of eutrophication, global warming, and marine acidification, as well as providing habitat, food and shelter for marine organisms. Seaweeds are used in several industrial sectors including feed, fertiliser, food, nutraceutical, and cosmetics. Seaweed production leads to the creation of jobs and to improvements in human diets and health thanks to the large amounts of minerals, trace elements, vitamins, and small quantities of healthful omega-3 fatty acids, that algae contain. Despite these advantages few species are authorised for human consumption, production competes with other coastal activities, the market is underdeveloped, and the initial investment in cultivation technologies can be substantial, all of which prevent the seaweed sector from reaching its full potential.
Marine algae could become an important part of the blue bioeconomy
Acknowledging these bottlenecks, the European Commission launched in 2018 the Blue Bioeconomy Forum, a platform for a platform for entrepreneurs, researchers, government officials and other stakeholders to identify drivers and obstacles and to chart a way forward for the blue bioeconomy including the marine algae sector. Maris Stulgis from DG MARE sees multiple roles for algae—as a source of environmental services, a path towards sustainable food systems, and a means to reduce dependence on fossil fuels. The Blue Bioeconomy report from 2018, the Blue Bioeconomy Forum, and the annual Blue Economy Report, are some of the initiatives launched by the Commission with a bearing on algae, he told the audience. In addition, the European Green Deal is intended to make the EU economy more sustainable and has several initiatives, among others clean energy, circular economy, and preserving ecosystems and biodiversity, towards all of which algae production can contribute. As part of its Farm to Fork strategy the Commission envisages targeted support for the algae industry as it has the potential to become a sustainable protein source and contribute to global food security. The Commission’s guidelines for sustainable aquaculture are also being revised to focus more on sustainability, diversification (of species, production methods, and products), and innovation and thereby contribute to European Green Deal initiatives. An EU algae initiative is in the pipeline that will cover algae’s contribution to sustainable aquaculture, climate mitigation and adaptation, and the circular economy. New standards on algae and algae products have been adopted which help to define algae and remove some of the ambiguity that has surrounded them.
The Horizon 2020 is an EU programme for funding research and innovation activities. For the algae sector the programme is particularly interesting for its support for sustainable production and products, biofuels, and for research related to climate change. The programme is currently funding close to 100 algae-related projects, reported Zoi Konstantinou from DG MARE. Support for projects that are ready to go is also available through Blue Invest, a fund supporting blue economy priorities and which seven algae projects have made use of. For the programming period 2021 to 2027 Horizon Europe is the main funding programme for research and innovation and for the algae sector areas of particular interest are renewable energy, ecosystem services, new and innovative products, and production control.
Recycling water to reduce algae production costs
Many of the presentations focused on ways to reduce the cost of production. Leen Bastiaens from Vito, a Belgian research organisation, showed how algae production could be made more efficient by reusing the medium the algae are grown in. Recycling reduces water consumption and saves on the cost of salts (added when freshwater replaces seawater as the medium). A computer controlled submerged membrane-based technology (Membrane Algae Filtration, MAF) developed at Vito enables preharvesting of microalgae and medium reuse. It produces a permeate comprising water and almost all the salts which can be reused after adding some nutrients (nitrogen and phosphorus). The other output is a preconcentrated algae biomass that can be further concentrated if necessary. Trials linking a MAF to 1,500 l bioreactors revealed that water reuse and salt reuse were both between 90 and 95%, while algae concentrations of up to 60 g of organic matter per litre were obtained. Reusing the medium did not show any negative impact on algae growth. Dr Bastiaens said the technology was being developed in two directions: upscaling the membrane surface to 10 sq. m for daily harvesting of up to 3,000 l; and testing it with different algae species. While all the algae tested were successfully harvested using MAF, one of them, Rhodomonas, a microalgae lacking a cell wall, also demonstrated the technology was safe even for fragile cells at high volumes. With Rhodomonas, high concentration factors (above 100) were achieved using MAF and the technology could also be used to desalt the biomass, which is relevant when the product is intended as food or feed.
Achieving the economies of scale necessary for commercialisation
The algae sector has the potential to contribute significantly to several worthy goals including food security, sustainable energy, and climate change mitigation, but it is hampered by unfavourable economics that constrain it to niche markets in the case of microalgae and by a lack of space to expand in the case of macroalgae. Prof. Gabriel Acien from the University of Almeria together with colleagues in the Sabana project worked on ways to reduce the cost and increase the scale of algae production to make it more economically viable. The project was funded under the Horizon 2020 programme and led to the construction of R & D and production facilities at the university. Trials were carried out to integrate treatment of wastewater from urban and livestock sources with an algae biorefinery to synthesise valuable products for agriculture and aquaculture in a bid to increase the sustainability of the entire food production system. Technologies were evaluated that would deliver high value products such as biostimulants, biopesticides, and feed additives. The analysis of biomass production showed that recycling seawater or using sewage, getting nutrients from manure or sewage, and using flue gases as a carbon source were necessary for environmental sustainability. The data from the trials confirmed that raceway and harvesting technology could be optimised to keep costs below EUR5/kg. And below EUR2/kg was achievable if production was coupled with the treatment of wastewater. Crops treated with the biostimulants and biopesticides produced from the microalgae responded with larger root development, a 20% improvement in production of first quality fruits, and a 40% reduction in adverse effects from fungi. The aquaculture feed additive had a positive impact on fillet texture and on fillet lipid degradation under storage with the addition of just 4% of the additive to the aqua feed. However, the latest data from the project suggest that the market for the agriculture products is more lucrative than that for the aquaculture feed additives. Not only is the value of the biomass much higher, but even with small production capacities it is possible to enter this market. On the other hand, returns from the wastewater treatment are much lower than the value of the biomass. The knowledge generated by the Sabana project can be used to design commercial-scale production systems with harvesting and processing systems tailored to the target products.
A potential area of interest for algae farmers is offshore farming. This would get around the challenge of space in coastal areas and allow large scale production. Bernardete Castro from Algaemech said that mechanisation and modern technology could lower the cost of production. She presented a business case for offshore seaweed farming based on a 500 ha farm established at a wind farming site using lines and nets to grow algae. The model showed that line-based systems were viable in 2020 and that there was a significant reduction in costs over two decades. For net-based systems further cost reductions and increases in yields were necessary to make them economically feasible.
Biofilms have some advantages over suspended cultivation
The quest to increase environmental and economic sustainability of algae biomass production was the subject of several interventions at the conference. Algae production is mainly based on suspended cultures that require large volumes of water. Extracting the biomass requires the use of energy to concentrate, harvest, and dry the production. Freddy Guihéneuf presented a rotating algal biofilm that was developed at Inalve, the company at which he works. A biofilm is a collection of microorganisms growing on a surface and embedded in a matrix they secrete that holds them together. Biofilms have advantages over suspended cultivation in that they require less water, harvesting costs are lower, and biomass productivity, in this case of Tetraselmis suecica, is higher. The gentle harvesting method (by scraping) also prolongs the shelf life of the microalgae paste. The company has upscaled the production system from 0.1 sq. m to 25 sq. m and explored the impact of system shape and rotation speed on productivity. The result has been an increase from 3-4 g/sq. m/day to more than 6 g/sq. m/day using a cylindrically shaped system and a speed of 0.174 to 0.263 m/s. Studying the periodicity of harvesting suggested a period of 12 days gave the maximum yield of 60 t/ha/year. In addition, the biochemical composition of the biomass remained stable for harvesting periods between 7 and 14 days. Since the company targets the market for live feed for aquaculture it was necessary to test cell viability. Experiments showed that after 14-21 days 50-60% of the cells were viable when stored at
4 degrees. The live feed was tested on oysters to see if it could improve their quality, which tends to deteriorate during the depuration process. The experiments showed a 70% decrease in mortality and a 1-2 point increase in the flesh index compared with oysters that were not fed. Moreover, an analysis of the nutritional value of the oysters that received the live feed showed an increase in the lipids, glycogen and the omega-3 fatty acid content compared with the control.
Biomass producers have different drying techniques to choose from
After harvesting microalgae, the moisture content of the biomass can be as high as 80% necessitating dehydration to commercialise the product. Drying is expensive and can have an impact on the quality of the product, so the method chosen influences the economics of the production. Ioannis Tzovenis from the University of Athens presented the results from laboratory tests of four ways of drying spirulina, a planktonic blue-green alga found in the tropics. The objective of the tests was to obtain the highest product quality in terms of nutritional content and functionality, and bring moisture content down to under 7% at a reasonable cost. Greenhouse drying uses solar energy which keeps costs low, however there is a risk of impaired product quality, Hot air drying has the advantage of low cost but energy efficiency is low, nutrients are degraded and taste is affected negatively. Vacuum drying preserves the nutritive value and has a high drying rate, but the costs are high. Finally, freeze drying results in the highest quality of all the methods, but the drying rate is slow and the costs are high. The scientists carried out a lifecycle assessment of producing dry Spirulina biomass using the different drying techniques. This showed that freeze drying produced the greatest environmental burden due to high energy consumption although the quality of the final product was relatively high. The other three methods showed no difference regarding environmental impact, so the choice would depend on the trade offs that a commercial operation is ready to accept.
Algae can also counter some health impacts caused by poor lifestyles
Among the apparent benefits of spirulina is its effect against NASH, a disease of the liver correlated with an excessive intake of calories and a sedentary lifestyle. A French company, Algosource, manufactures a product based on spirulina that is effective in preventing NASH. In a study of three groups of mice fed on three diets—normal; western (highly calorific); and western plus the spirulina derivative—Olivier Lepine, the managing director, showed that after 25 weeks, the group receiving the spirulina extract put on less weight and showed less tissue fat than the other two groups, despite having a higher intake of food. Liver parameters were also much better for this group compared to the other two. In addition, all the genes involved in liver functioning were also affected by the spirulina extract. Further trials involved human subjects, where the researchers looked at antioxidation parameters and liver parameters. The results harmonised with the animal trials: an increase in food intake for the spirulina extract group without an increase in weight. There was also less oxidative stress damage in this group. Similar though statistically insignificant changes were recorded with the liver parameters, BMI, and fatty liver index. The results suggest that the spirulina extract, the first extract to be clinically tested, protects against NASH, but other studies are
The high content of valuable nutrients in microalgae means that small quantities can be used to enrich staple foods, however, the nutritional benefits need to be weighed against changes in texture and taste. Cristiana Nunes from the University of Lisbon tested the potential of adding microalgae to bread using three microalgae, organic Chlorella vulgaris produced under autotrophic conditions, and blond and smooth Chlorella both produced under heterotrophic conditions. The latter two showed lower protein and higher carbohydrate levels than the former. All three microalgae were incorporated into wheat bread doughs and Ms Nunes and her colleagues found that water increased with the level of microalgae added due to the higher protein content, and that dough stability declined, however the elasticity of the dough remained unaffected. The baked bread showed an increase in firmness which was attributed to the protein content. In addition, when 6% microalgae was added (as opposed to 4%) there was a decline in the volume of the bread. In the sensory analysis bread with the organic Chlorella scored lower than bread with the other two. In terms of colouration the change was most dramatic again with bread mixed with organic Chlorella. She concluded that both the heterotrophically produced smooth and blond Chlorella could be used to enrich bread without putting off consumers.
Putting metabolic engineering to use in the production of astaxanthin
Prof. Matteo Ballottari from the University of Verona is exploiting Nannochloropsis gaditana, a microalgae, for its content of astaxanthin, a powerful antioxidant, and EPA, an omega-3 fatty acid. Astaxanthin is used as an additive to fish and poultry feeds and as a colouring agent, but also has potential uses as a supplement to improve human health. Natural astaxanthin is produced mainly from a green alga, Haematococcus pluvialis that generates it under conditions of stress, but the growth rate is slow, it is difficult to cultivate, and extraction is expensive. One alternative is to produce it synthetically, but this raises issue of sustainability as the source is usually petrochemical, the synthetically produced variety has much less antioxidant activity compared to the natural product, and it is not approved for human consumption. Prof. Ballottari and his colleagues looked at N. gaditana which only produces traces of astaxanthin, if at all. Using metabolic engineering they produced a number of strains of which one was characterised by higher carotenoid content. The increased content of astaxanthin, production in a single cultivation step, and lower extraction costs potentially allow a large increase in production efficiency compared with current methods. The team also discovered that the same strain of N. gaditana also accumulated EPA, an important fatty acid for human and animal nutrition. Productivity of both ketocarotenoids and EPA was stable nor did the accumulation of the two compounds interfere with each other. Among the advantages of using N. gaditana compared with H. pluvialis was that it could be used to manufacture two products, astaxanthin and EPA, it is faster growing, it is compatible with current recovery systems for these two products, and it makes redundant the stage, where H. pluvialis must be stressed to trigger it to produce astaxanthin, leading to cost savings.
A source of biodegradeable bioplastic
Microalgae also have the potential to address another important issue, that of plastic pollution. Pablo Alvarez from CEA Tech, a French company, is using microalgae to produce bioplastics. Bioplastics that are biodegradeable and made from bio sources include PHA (produced from bacteria), PLA (from polymerisation of lactic acid), PBS (from polymerisation of succinic acid), and starch (from crops). Bioplastics from starch blends have about a fifth of the total bioplastics market, but since starch is produced from crops it can lead to friction between the food industry and the bioplastic sector. A potential alternative is to produce starch from microalgae such as Chlorella which when stressed can exhibit a starch content of 60%. CEA is currently involved two projects: Nenu2phar, where microalgae starch will be used to produce PHA; and Sealive (funded by the European Horizon 2020 programme) where starch, PHA, and PLA will be produced. The two projects plan to develop several commonly used plastic products including fish crates and fishing nets, thermoformed plastic trays for food packaging, and packaging film. Both projects will start with microalgae to produce starch which will be further processed to PHA.
Microalgae could also play a role in removing nutrients from agriculture effluents. Nutrients such as nitrogen and phosphorus contribute to eutrophication in the Baltic Sea, algal blooms, oxygen depletion, and turbidity of the water. Joao Salazar from the University of Turku in Finland used effluents from a cucumber greenhouse that were loaded with nitrogen in the form of nitrates and phosphorus. The effluent also had low turbidity so it would not block photosynthetic activity, and a pH close to neutral which is ideal to support algae. In the first trial, algae were grown in a photobioreactor with an overhead light source. Here more than 50% of the nitrogen and close to 100% of the phosphorus was removed from the effluent. In the second trial red and blue LEDs were used to illuminate the photobioreactor from the side. This time by the third day phosphorus removal was 100% and by the 15th day nitrogen removal was 100%. The dry weight of the algae biomass was 4.8 g/litre and it has now been preserved for further study. The results show the potential for using algae for sustainable water treatments.