Dear EarthTalk:

We used to hear a lot about algae's potential as a renewable source of biofuels. Is it still being cultivated and processed accordingly?

P.K., Richmond, VA

In recent years, algae has emerged as a potential renewable and less pollutive energy resource. Some species have high levels of fat, carbohydrates and proteins that can produce up to 30 times more energy than other biofuels. And algae, unlike corn and soy-based biofuels, can thrive well in a variety of environments (including otherwise unusable waste or brackish water). Combined, the high-energy content and abundance of algae make it a promising alternative to current fuel sources.

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Some companies, including the low-carbon energy research organization, Decerna, experimented with algae, hoping it could be produced at an industrial level. They cultivated it in artificial light, feeding it a mixture of glycerol, yeast and various chemicals. They then extracted the functional fats and converted them into biodiesel. The researchers calculated the energy required during each stage of the process and the carbon emissions produced from burning the resulting biodiesel. They concluded that the production process required more energy than the final product generates, and that total emissions produced during the production and combustion phases of the algae surpassed those of traditional petroleum diesel.

It was also learned that the extraction of the algae’s biomolecules may involve the use of harsh chemicals or solvent, and that the growth of algae may also require chemicals like fertilizers and pesticides, which can have adverse effects on aquatic ecosystems if they get into surrounding water bodies through runoff, or if they accumulate in the algae biomass. Mechanical procedures require fewer chemicals but are less effective at separating the diverse array of materials within the algae. Also, cultivation of algae on a large scale uses large amounts of electricity as it often relies on artificial lighting to ensure optimal and controlled growth conditions. Moreover, the space required to grow and process algae on a commercial scale can also be a significant environmental concern. Large-scale algae cultivation facilities often occupy substantial land areas or require dedicated infrastructure such as ponds, bioreactors or photobioreactors.

Despite the promise that algae holds, there is a clear need for technological advancements across the entire supply chain. Techniques for seaweed cultivation, harvesting and transportation must be made more efficient. Several laboratories, such as the National Renewable Energy Laboratory and the Las Alamos National Laboratory, have been cultivating and manipulating particular strains of algae to genetically maximize the production of fuel biomolecules and other bioproducts. Additionally, improvements in pre-treatment methods, co-digestion processes, and the development of eco-friendly extraction techniques are essential. Furthermore, advancements in fuel conversion technologies are necessary to ensure that the algae is economically viable and able to be implemented into the current infrastructure. With these changes, perhaps we will see the rise of algae-based biofuels in the future.

CONTACTS

• Algae for global sustainability? https://www.sciencedirect.com/science/article/pii/S006522962100015X
• The use of algae for environmental sustainability: trends and future prospects, https://pubmed.ncbi.nlm.nih.gov/35332453/
• Developing algae as a sustainable food source, https://www.frontiersin.org/articles/10.3389/fnut.2022.1029841/full
• Role of microalgae in achieving sustainable development goals and circular economy, https://www.sciencedirect.com/science/article/pii/S0048969722057886.

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