From farm to table, most greenhouse gas emissions from the food system come from food production — particularly from the production of meat and dairy. Food system activities, from production and transportation to storing food in landfills, emit greenhouse gasses that contribute to climate change. Now, a new study from Stanford University suggests one greenhouse gas can be captured and transformed into feed for farmed fish.
Published in the journal Nature Sustainability, the study unveils a new, cost-effective method of producing fishmeal from methane, a greenhouse gas emitted and flared from industrial sources across the US. Here’s how it works: methanotrophic bacteria, which serve as biofilters for the oxidation of methane, transform the greenhouse gas into protein-rich fishmeal for farmed fish.
“In the rapidly growing aquaculture industry, methanotrophic additives have a favorable amino acid profile and can offset ocean-caught fishmeal, reducing demands on over-harvested fisheries,” the study’s authors write.
Other efforts are currently underway to capture and transform methane, whereby methane is processed and burned for energy or sold in order to remove it from the atmosphere. For example, manure and flatulence from cows, a source of methane, can be trapped and turned into natural gas. However, this method and others like it can be expensive and inefficient. That’s why Stanford researchers wanted to make a paradigm shift and create a high-value product using biotechnology.
Alhough carbon dioxide is more abundant in the air than methane, the global warming potential (GWP) of methane is about 80 times greater than that of carbon dioxide over a period of 20 years. Methane also threatens air quality, causing an estimated one million premature deaths annually. Since the beginning of the Industrial Revolution, methane’s concentration has grown more than twice as fast as that of carbon dioxide.
This is where methanotrophic bacteria come in. The methane-consuming bacteria can be grown in chilled, water-filled bioreactors and fed pressurized methane, oxygen and other nutrients. The resulting protein-rich biomass can be used for fishmeal in aquaculture feed, counteracting demand for fishmeal made from plant-based feeds or small fish that require valuable resources to produce.
Since seafood consumption has increased more than fourfold since 1960, fish farms have become the provider of about half of all the animal-sourced seafood we consume. The challenge will only grow as the global demand for blue foods – fish, shellfish and algae – will likely double by 2050, according to the Blue Food Assessment.
The researchers examined scenarios in which methane is sourced from landfills and oil and gas facilities, wastewater treatment plants and natural gas purchased from the commercial natural gas grid. Their analysis found that methanotrophic fishmeal production costs were between $1,546 and $1,783 per ton, depending on the source of methane. Electricity costs could also be lowered with reactors that more efficiently transfer heat and require less cooling.
“Our results show that current technology can enable production, in the United States alone, equivalent to 14 percent of the global fishmeal market at prices at or below the current cost of fishmeal,” the Stanford researchers said.
The study ultimately concludes that two problems can be solved with one cost-effective, sustainable solution.