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Scientists solve two problems at once—turning methane pollution into sustainable fishmeal

Researchers have demonstrated that we can solve one food system problem—the huge quantity of feed needed to fuel the growing aquaculture industry, by simultaneously tackling another—the vast amount of methane pollution that escapes into the atmosphere each year and poses an enormous climate change risk.

www.anthropocenemagazine.org|Emma Bryce

In a study published in Nature Sustainability, the researchers show that capturing polluting methane gas that’s generated as a byproduct from industrial operations across the United States, then turning it into a feedstock to make protein-rich fishmeal, would be cheaper than making conventional meal from ocean-caught fish. What’s more, this waste methane could already supply 14% of the world’s fishmeal demand. That could expand to 100%, if greater technological advancements allowed us to capture all the stranded methane that exists across the US.

But how does methane become fish food—and why do we need it, in the first place? As global populations rise, large scale fish farming is seen as an increasingly viable way to plug the world’s growing protein gap. The problem is, those farmed fish need food, which is usually made from forage species that are extracted at industrial scales from the oceans and pounded into meal. As the aquaculture industry grows to keep up with demand, it’s putting more and more pressure on these critical marine resources—making it clear that we’re going to need alternatives, soon.

Where methane comes into this equation is that it turns out to be a very reliable feed source for a type of gas-guzzling bacteria called methanotrophs. If these organisms are grown in bioreactors and fed a steady supply of methane, combined with other nutrients such as nitrogen and phosphorus, they can transform those inputs into protein-rich biomass with a very similar nutritional profile to fishmeal. Not only could this bacteria-generated feed replace regular fishmeal, crucially it would also keep massively polluting methane out of the atmosphere: this gas has a warming potential up to 34 times higher than carbon dioxide, making it a major accelerant of climate change.

Feeding methane to bacteria has been on the cards for a while. But the new study is the first to explore the economic feasibility of turning this wasted resource into food.

Could Fungi Be the Key To Eliminating Uranium From the Food Chain?

Scientists looked at how chronic uranium exposure in the food chain from past mining might be reduced, examining how root fungi might alter the uptake of uranium in plants.

www.technologynetworks.com

Wasylenki says hardly anything is known about the role of fungi in the uptake of elements by plants. “We saw one experimental paper saying the fungi made the plants take up more uranium total, but only in the roots—it didn’t transport up into the shoots or leaves of the plants.”

She explains that in grazers, some pull up the whole plant to munch on, while others (like sheep) pluck the tops of the plants. Wasylenki and Dunlap wanted to test whether there was a way to stimulate growth of the right fungi and sequester uranium underground. “Then at least you would be helping to reduce the uranium consumption of guys that just crop the tops [of the plants],” notes Wasylenki.

The team grew sunflowers with and without symbiotic root fungi (called arbuscular mycorrhizal fungi). In particular, they were curious how the mineralogy of the soil and the presence of fungi would influence the uptake of uranium in sunflowers. Artificial soil (Turface) with no uranium present was used in the pots, and a layer of clay-rich material was added. Uranium was added in a known concentration when the plants were watered.

When they looked at the uranium concentrations in plant tissues, they found that the presence of fungi decreased the spread of uranium from roots to shoots. They also found that the presence of a clay layer in the soil increased the uptake of uranium in the plants. Wasylenki hypothesizes that “uranium would sorb to the clay surfaces, holding it there, so that it had a longer residence time around the roots.” She adds that while more uranium was taken up in clay-rich soils, less was translocated throughout the plant—more was stored in the root system of the sunflowers.