Producing meat and seafood is big business, but the impact on the environment varies. As consumers focus more on making sustainable food choices, knowing more about the impact of each choice matters.

A study out of the University of Washington may have some answers.

"From the consumer's standpoint, choice matters," lead author and University of Washington professor in the School of Aquatic and Fishery Sciences Ray Hilburn, said in a statement. "If you're an environmentalist, what you eat makes a difference. We found there are obvious good choices, and really obvious bad choices."

Seafood (mostly) rises above

For the study, published in the journal Frontiers in Ecology and the Environment, researchers collected more than 300 published life-cycle documents for different animal protein production processes. These documents were "cradle-to-grave" assessments that considered the environmental impacts of all stages of a product's life. Of these, Hilborn and co-authors selected 148 reports that were both comprehensive enough but not too specialized to inform their study.

The researchers used four metrics to compare the impacts across different kinds of food production, including livestock, farm-raised seafood and seafood caught in the wild. They evaluated a product's energy use, greenhouse gas emissions, potential to contribute excess nutrients — like fertilizer — to the environment and the potential to emit substances that contribute to acid rain.

An oyster farm in Thailand Mollusk farms, like this oyster farm in Thailand, had lower environmental impacts compared to production of other proteins. (Photo: miiidoro/Shutterstock)

To best quantify the differences between the different kinds of proteins, Hilborn and his team compared the environmental impacts of those metrics by using 40 grams worth of each protein being evaluated. So, the researchers analyzed what the contribution to acid rain that 40 grams worth of beef or catfish might be given the data they had.

Forty grams is roughly the weight of a hamburger patty.

"This method gives us a really consistent measurement people can relate to," Hilborn said.

Production cycles that performed well across all metrics included farmed shellfish and mollusks, and capture fisheries such as sardines, mackerel and herring. Other seafood choices, like whitefish and farmed salmon, also did well.

Fish versus plant-driven diets

Stacks of lobster traps on a pier Lobster fishing was found to use a great deal of fuel, and thus contribute more to greenhouse gases, than other seafood fishing practices. (Photo: Mark Bulmer/Shutterstock)

Farmed seafood, like catfish and tilapia, used more energy than livestock production due to water circulation requirements. However, since livestock produces a lot of methane in manure, it did not perform well in the acid rain contribution category. Similarly, beef, along with farmed catfish, produced 20 times more greenhouse gases than farmed mollusk, small capture fisheries, farmed salmon and chicken.

Capture fisheries varied in their greenhouse gases emissions due to the difference in fuel consumption. Practices like purse seine netting used the least amount of fuel per 40 grams of protein while pot fisheries for lobsters used a great deal of fuel.

Researchers also compared their findings with the findings of similar work done regarding vegetarian and vegan diet impacts. They found that "a selected diet" of farmed and wild-caught fish had a lower environmental impact than either of those plant-driven diets.

"I think this is one of the most important things I've ever done," Hilborn said. "Policymakers need to be able to say, 'There are certain food production types we need to encourage, and others we should discourage.'"

The study was partially funded by Seafood Industry Research Fund, a non-profit that "awards grants to individuals and institutions to conduct forward-thinking research that will advance the seafood industry."

Hilborn came under scrutiny in 2016 following a Greenpeace report that he had failed to disclose that he received funding from the seafood industry in a few studies. Multiple academic journals and the University of Washington found that Hilborn was not in violation of disclosure policy procedures.

The study was published in the journal Frontiers in Ecology and the Environment.