In terms of climate change Methane is not really our friend, but maybe it can be fish food? A recent study published in Nature Sustainability suggests that transforming this potent greenhouse gas into protein rich feed for farmed fish is a potential solution to reduce methane emissions and conserve wild fish populations. It may sound a little fishy, so let’s dive in for a closer look.
What is Methane’s role in climate change?
By now, most people are familiar with carbon dioxide (CO2), the poster child for climate change issues. However, methane (CH4) is carbon dioxide’s less famous, more potent relative. Methane has about 25 times the global warming potential (GWP) as the infamous carbon dioxide over a 100 year period, as methane cycles through the atmosphere faster than carbon dioxide. Calculating the GWP of a greenhouse gas standardizes it in terms of carbon dioxide, so releasing 1 kg of CH4 into the atmosphere is equivalent to releasing 25 kg of CO2. From 2014-2018, the United States’ methane emissions exceeded 630 million metric tons of CO2 equivalents per year. This equals the amount of CO2 produced by all the cars in Japan and India combined!
Stranded methane, or methane emissions from manmade facilities that have the potential to be used, is sourced from either landfill sites, water treatment plants, or oil and gas facilities. As of 2018, oil and gas facilities accounted for nearly 30% of methane emissions, while landfill and wastewater treatments accounted for 17% and 2%, respectively. Methane emissions aren’t slowing down anytime soon, so we need to figure out what to do with them. That’s where fish food swims in!
Fumes to fish food
Global fish farming is a growing industry, generating $271.61 billion in 2018 and is projected to reach $376.48 billion by 2025. Farmed fish eat fishmeal sourced from wild caught fish. Not only is this cannibalistic, but it’s also bad for wild fish populations! Fish don’t need to eat other fish, they just need the right mix of nutrients and proteins that these other fish have to offer. So, what if we could make something with that same mix of amino acids and nutrients? That’s where methanotrophic bacteria come in. Methanotrophic bacteria can eat methane and turn the gas from a potent GHG into a protein-rich biomass, which incidentally has a similar protein profile to fishmeal. Talk about a so-fish-ticated solution! Stanford researchers outlined the process of using methanotrophic bacteria to turn methane into animal feed and analyzed the economic feasibility of using this process as a replacement for current fishmeal sourcing practices
How it works
First the “stranded” methane, or methane emissions from manmade facilities that have the potential to be used, is sourced from either a landfill site, water treatment plants, or oil and gas facilities. The methane is cleaned, removing contaminants such as H2S and siloxanes. The “Cleaned” methane is then compressed along with additional air. The compressed air and methane then go into a methanotroph reactor containing water, macronutrients and methanotrophic bacteria. In the reactor, biomass is produced and is transferred to a dewatering centrifuge. Excess water from the biomass goes back to the methanotrophic reactor to be used for cooling. Finally, biomass goes to a dryer, and once dried can be used for animal feed.
To process approximately 1.4 tons of methane, this process requires approximately 8,290 kWh of electricity, releases heat and 2 tons of CO2.
Should we seize the oppor-tuna-ty?
Results of the study showed methanotrophic feed has many benefits. Turning methane into animal feed could cut methane pollution while simultaneously reducing dependence on wild caught fishmeal, which is great for fighting climate change and wild fish populations. Furthermore, methanotrophs don’t require light, which enables high volume and dense production of proteins. This low spatial footprint is good for land use. Additionally, high quality fishmeal is composed of 60-72% crude protein while methanotrophic biomass is 67-81% crude protein, potentially making methanotrophic biomass more nutritious. So, should we take the bait and start making all our fishmeal from methane? Maybe, but a few things need to happen before this becomes a reality.
