By Victoria Wallace, MESM '21
Thinking of becoming a vegetarian? You’re not alone. Globally, though, 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. One of the primary environmental impacts associated with meat comes from agriculture—specifically, the land used to grow feed for livestock (including beef, pork, chicken, and fish).[i] Finding alternative feed ingredients could help the agriculture and aquaculture industries meet the rising demand while reducing impacts. 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 feed ingredient: microorganisms.
The primary sources of protein in feed have traditionally been agricultural products—grains, seeds, and beans—and wild-caught fish.[ii] The decline of wild fish stocks has put pressure on the feed production industry to find a new source of protein. “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 water.” 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, raising concerns about food security. [i, ii] In terms of environmental impact, growing soybeans requires large swathes of land and consumes freshwater. [i] Concerns about sustainability, combined with the growing demand for fish and meat, have motivated the exploration of microbial protein alternatives.
Specifically, the research team looked at whether bacteria or yeast could be used in feed for farm-raised salmon. The researchers compared the microbes to soy using a life-cycle assessment process. This approach 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]
Could yeast or bacteria be the sustainable protein alternative protein that the aquaculture industry has been looking for? Unfortunately, there's no straightforward answer. 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. Overall, using microbe-based protein meals would decrease the environmental impact of the feed as a whole, but the impact of the other ingredients outweighed much of the benefit. “It’s another layer of information,” Jessica 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,” Jessica explains. The aquaculture industry is growing, though, and so is the demand for feed. Fish feed companies are looking for aquaculture-specific ingredients to avoid competition with other industries, including pet food, human food, and other feedstocks.
Considering this competition, 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; microbes can be manipulated to 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 might not all have to become vegetarians, after all.