From moo to goo: Cooperating microbes convert methane to alternative fuel source
April 21, 2017 by Pacific Northwest National Laboratory
April 21, 2017, Richland, Wash. – Oil and gas wells and even cattle release methane gas into the atmosphere, and researchers are working on ways to not only capture this gas but also convert it into something useful and less-polluting.
Now scientists at the Department of Energy’s Pacific Northwest National Laboratory (PNNL) have developed a new system to convert methane into a deep green, energy-rich, gelatin-like substance that can be used as the basis for biofuels and other bioproducts, specialty chemicals — and even feed for cows that create the gas in the first place.
“We take a waste product that is normally an expense and upgrade it to microbial biomass which can be used to make fuel, fertilizer, animal feed, chemicals and other products,” said Hans Bernstein, corresponding author of a recent paper in Bioresource Technology.
Methane is an unavoidable byproduct of our lifestyle. Manure from dairy cows, cattle and other livestock that provide us food often breaks down into methane. Drilling processes used to obtain the oil and natural gas we use to drive our cars and trucks or heat our homes often vent or burn off excess methane to the atmosphere, wasting an important energy resourcePNNL scientists approached the problem by getting two very different micro-organisms to live together in harmony.
One is a methane-loving methanotroph, found underground near rice paddies and landfills — where natural methane production typically occurs. The other is a photosynthetic cyanobacterium that resembles algae. Originally cultured from a lake in Siberia, it uses light along with carbon dioxide to produce oxygen.
The two aren’t usually found together, but the two co-exist in harmony in a bioreactor at PNNL — thanks to a co-culture system created by Leo Kucek, Grigoriy E. Pinchuk, and Sergey Stolyar as well as Eric Hill and Alex Beliaev, who are two authors of the current paper.
PNNL scientist Hans Bernstein collected methane gas from a Washington dairy farm and Colorado oil fields and fed it to the microbes in the bioreactor.
One bacterium, Methylomicrobium alcaliphilum 20Z, ate the methane and produced carbon dioxide and energy-rich biomass made up largely of a form of carbon that can be used to produce energy.
But Methylomicrobium alcaliphilum 20Z can’t do it alone. It needs the other micro-organism, Synechococcus species 7002, which uses light to produce the steady stream of oxygen its counterpart needs to carry out the methane-consuming reaction.
Each one accomplishes an important task while supplying the other with a substance it needs to survive. They keep each other happy and well fed — as Bernstein puts it, they’re engaging in a “productive metabolic coupling.” READ MORE