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
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
Hydrogen Production by Fermentation
Over the last three decades, scientists at NREL have developed extensive expertise in pretreatment technologies to convert lignocellulosic biomass into sugar-rich feedstocks that can then be fermented by microbes to produce ethanol and various high-value chemicals. This substantial investment is now being leveraged to investigate the fermentation of sugars and pretreated biomass into hydrogen.
Researchers are working to identify efficient cellulolytic microbes, such as Clostridium thermocellum, that can directly ferment crystalline cellulose to hydrogen to lower the feedstock cost. Once a model cellulolytic bacterium is identified, its potential for genetic manipulations, including sensitivity to antibiotics and ease of genetic transformation will be determined. The next step will focus on developing strategies to generate mutants that are selectively blocked in the production of waste acids and solvents generated in fermentation reactions, to maximize the hydrogen yield. Our research also entails developing a more in-depth understanding of the underlying hydrogenase catalysts responsible for hydrogen production, with the ultimate goal of lowering the cost of renewable hydrogen fuel so that it's competitive with gasoline.
Contact: Pin-Ching Maness
