By Victoria Wallace, MESM '21
Thinking of becoming a vegetarian? You’re not alone. Globally, however, the demand for meat has been rising, along with an expanding middle class.[i] This trend concerns many environmentalists, who fear that the rising rate of meat consumption is unsustainable. You may have heard that eating meat is bad for the environment, and one of the main reasons for this is land use—specifically, the land used to grow food for livestock.[i] To meet the rising demand for meat and reduce environmental impacts, scientists are searching for alternative feed ingredients, which could help make meat production more sustainable. In a recent study, published in January 2019 in the Journal Environmental Science & Technology, PhD candidate Jessica Couture and her research group turned to what may seem like an unlikely solution: microorganisms.
Most of the time, the protein in livestock feed is supplied by grain, seeds, beans, or even fish.[i, ii] The decline of wild fish stocks, however, has put pressure on the aquaculture industry. Fish farming operations often rely on fish meal as a protein source for carnivorous species, such as salmon. “A lot of times we're feeding them more fish than we're producing,” Couture explains. “And we can’t keep pulling fish out of the ocean.”
A common alternative to fish meal is soy, which is nutritious, protein-rich, and cost-effective. However, soy is an important crop for the global food supply, and diverting more soy to livestock raises concerns about food security.[i, ii] In addition, soybean fields occupy large swathes of land and consume fresh water through irrigation.[i] A more sustainable option could be protein sourced from microbes, but, until recently, little was understood about the environmental trade-offs between protein sources.
Specifically, the research team looked at whether bacteria or yeast could be used as a protein source for farm-raised salmon. The researchers compared each type of microbial protein to soy using a life cycle assessment approach. This method allows for comparison of environmental impacts at every stage in the production process. Each protein source—yeast, bacteria, and soy—was evaluated on seven environmental impact indicators. While both types of microbe meals compared favorably to soy, yeast meal looks particularly promising, outperforming soy on all seven indicators.[ii]
Protein-rich meals, however, are just one of many ingredients in a livestock feed. Salmon feed is formulated to meet the fish’s nutritional needs and promote rapid growth. Microorganisms would only be one part of this formulation, and other ingredients have their own environmental impacts.
Because other ingredients contribute to the life cycle assessment, the research team had different results when comparing meals to feeds. Microbe-based protein meals decrease the environmental impact of the feed as a whole, but the impacts of other ingredients outweigh these benefits. “It’s another layer of information,” Couture says. “Yes, using these alternative proteins does decrease the environmental impacts of salmon feeds, but there’s still work to do with the other ingredients.”
Microbial protein sources are not currently being used in industrial salmon feeds. “The hold-up is scale, and not being able to produce enough efficiently,” Couture explains. That said, the aquaculture industry is growing and, along with it, the demand for feed. Ideally, the aquaculture industry would use a specific type of microbial protein meal, formulated especially for fish. Fish feed companies would prefer it this way—to avoid competition with industries that make food for humans, pets, and other animals.
Considering the pressure on industries, human population growth, and the rising demand for meat, it may be only a matter of time until yeast-fed salmon hit the seafood section. And it might not just be salmon; microbial genomes can be changed meet the nutritional needs other farm-raised animals, as well. Even if the meat and fish industries grow, it’s possible that future feed formulations will be more environmentally friendly. We may not all need to be vegetarians, after all.
[i] Kim, S. W., et al. "Meeting Global Feed Protein Demand: Challenge, Opportunity, and Strategy." Annual Review of Animal Biosciences, 7(1), 2019, pp. 221–243.
[ii] Couture, J. L., et al. Environmental Benefits of Novel Nonhuman Food Inputs to Salmon Feeds. Environmental Science & Technology, 53(4), 2019, pp. 1967–1975.
[iii] Food photo created by pvproductions.