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Biological Sciences

NREL's biological scientists conduct research on microorganisms—such as photosynthetic bacteria, cyanobacteria, and algae—and are discovering new ways to produce hydrogen and valuable reduced-carbon compounds. We are studying how, through photosynthesis, green algae and cyanobacteria can split water to produce hydrogen, and how, through fermentation, bacteria can produce hydrogen from lignocellulosic biomass feedstocks.

Photobiological Water Splitting

Image of two green ovals with two yellow strands at the bottom of each oval.

Microscopic view of the green alga Chlamydomonas reinhardtii.

Microorganisms, like green algae and cyanobacteria, can produce hydrogen by splitting water through a process called "biophotolysis" or "photobiological hydrogen production." This photosynthetic pathway produces renewable fuels without co-generating greenhouse gases. The scientific challenge associated with the approach is that the enzyme (a reversible hydrogenase) that actually releases the hydrogen is sensitive to oxygen. The process of photosynthesis, of course, produces oxygen and this normally stops hydrogen production very quickly in green algae. So, to overcome this problem, NREL scientists are generating O2-tolerant, H2-producing mutants from photosynthetic microorganisms by various genetic approaches. The ultimate goal of this work is to develop a water-splitting process that will result in a commercial H2-producing system that is cost effective, scalable to large production, non-polluting, and self-sustaining.

Contact: Maria Ghirardi

Producing Hydrogen by Fermentation

Hydrogen production via fermentation is a viable technology if two technical barriers can be overcome: the cost of the feedstock and the yield of hydrogen. Over the last three decades, scientists at NREL have developed expertise in pretreatment technologies, converting lignocellulosic biomass into sugar-rich feedstocks such as cellulose and hemicellulose. Microbes are readily available to ferment these substrates directly to hydrogen to address the feedstock barrier. Genetic tools need to be developed to optimize the metabolic pathway of cellulolytic microbes to increase the yield of hydrogen in lieu of waste organic acids. NREL is leveraging this substantial investment in fermentation to investigate fermenting pretreated biomass into hydrogen.

NREL's fermentation research includes bioprospecting microbes to directly convert pretreated biomass to hydrogen and developing a more in-depth understanding of the underlying hydrogenase catalysts responsible for hydrogen production with an ultimate goal of lowering the cost of renewable hydrogen fuel to make it competitive with gasoline.

Learn about NREL's fermentation projects.

Contact: Pin-Ching Maness