This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: When landfills and wastewater treatment plants create methane as a byproduct, much of it is simply burned and its value is lost. But the gas is an energy-rich resource that could be recycled as a fuel, chemical feedstock or bioproduct.
Capturing and converting waste methane offers an opportunity to recover energy and create useful products from an otherwise wasted gas stream. To harness that resource, researchers at Lawrence Livermore National Laboratory (LLNL) have developed a solid-state bioreactor that can convert methane into succinate, a valuable chemical used to make polymers, stabilize drugs, enhance food flavor and more. The small, efficient bioreactor performs more than 10 times better than conventional liquid-state systems—and it consumes less power.
"Bioproduction using poorly soluble gases has long been limited by slow mass transfer and low efficiency because conventional liquid-phase bioreactors are not well suited for gas fermentation," said LLNL scientist and corresponding author Fang Qian. "With growing interest in recovering energy and valuable products from waste gas streams, new bioreactor technologies designed specifically for gas fermentation are greatly needed." The new method, published in Scientific Reports, exploits the unique metabolisms of methanotrophs, bacteria that naturally consume and process methane. "These microbes are naturally designed to do the conversion.
They work without added heat, without added pressure, without all these things that a chemical process normally requires," said LLNL scientist and author Samantha Ruelas. "That's the beautiful thing about this biology. Because it's natural, you don't need those things, and without them, it can be more cost-effective." Usually, bioprocesses take place in a large vat.
The gas is dissolved in water, the mixture is vigorously stirred, and the bacteria work their magic. But for poorly soluble gases like methane, it is a slow process that requires significant energy and operating costs. As a result, performing methane bioconversion at scale has been an economic challenge.
"Rather than have this big tank of a 'broth' that you're putting gas into, we produced these thin structures that we call scaffolds," said LLNL scientist and author Nathan Ellebracht. They have a lattice structure, and we put the microorganisms into a hydrogel that fills these really thin walls." The hydrogel walls are mechanically robust and resistant to degradation. The scaffolds supporting them can accommodate many times more bacteria than a vat.
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