Feb
24
Exhaling Hydrogen
February 24, 2009 | 4 Comments
Hydrogen is easily the most desired substance for chemistry and fuel making. Matched up with carbon from single carbon molecules up to sixteen or so plus hydrogen makes hydrogen carbon molecules the densest, richest, easiest to handle, lowest cost and familiar fuel products. The engines to use them are at hand and efficiency is the goal that incrementally gets answers surely and steadily.
But getting it free from water or separating it from hydrocarbons for use limits products and makes them expensive when energy for the splitting gets expensive. This makes the research out of Virginia Tech, Oak Ridge National Laboratory (ORNL), and the University of Georgia interesting in the extreme.
The team has produced hydrogen gas pure enough to power a fuel cell by mixing 14 enzymes, one coenzyme, cellulosic materials from nonfood sources, and water heated to only about 90 degrees (32 C). The enzymes consume cellulose from woodchips or grass and exhale hydrogen.
Hydrogen Enzyme Cocktail Process Diagram. Click for more.
The team announced three advances in their latest “one pot” process: A novel combination of enzymes, an increased hydrogen generation rate — to as fast as natural hydrogen fermentation, and a chemical energy output greater than the chemical energy stored in sugars – the highest hydrogen yield reported from cellulosic materials. Double check . . . yes, the Virginia Tech press release says “a chemical energy output greater than the chemical energy stored in sugars.”
Percival Zhang, assistant professor of biological systems engineering in the College of Agriculture and Life Sciences at Virginia Tech says, “In addition to converting the chemical energy from the sugar, the process also converts the low-temperature thermal energy into high-quality hydrogen energy – like Prometheus stealing fire.”
Jonathan Mielenz, leader of the Bioconversion Science and Technology Group at ORNL adds, “It is exciting because using cellulose instead of starch expands the renewable resource for producing hydrogen to include biomass.”
Zhang explains, while using cellulosic materials isolated from wood chips in the current research, other crop wastes or switchgrass could also be used. “If a small fraction – 2 or 3 percent – of yearly biomass production were used for sugar-to-hydrogen fuel cells for transportation, we could reach transportation fuel independence.” Zhang clarifies by adding that the 3 percent figure is for global transportation needs. The United States would actually need to convert about 10 percent of biomass – which would be 1.3 billion tons of usable biomass.
The earlier sugar-to-hydrogen fuel cell idea began as a theory. The vision is for the ingredients to be mixed in the fuel tank of your car, add enzymes to a mixture of starch based polysaccharides and water, then the enzymes use the energy in the starch to break up water into only carbon dioxide and hydrogen. A membrane bleeds off the carbon dioxide and the hydrogen is used by the fuel cell to create electricity. Water, a product of that fuel cell process, will be recycled for the starch-water reactor. Laboratory tests confirm that it all takes place at low temperature–about 86 degrees F—and at atmospheric pressure.
Thus, a car with about a 12-gallon tank could hold 27 kilograms of starch, which is the equivalent of 4 kg of hydrogen. Zhang estimates the range would be more than 300 miles. One kg of starch will produce the same fuel cell energy output as 1.12 kg (0.38 gallons) of gasoline in an engine.
This is the most recent research expands the potential from straight starch to cellulose for a fuel base. The new developments are published in the Wiley journal ChemSusChem (Chemistry and Sustainability), in the article Spontaneous High-Yield Production of Hydrogen from Cellulosic Materials and Water Catalyzed by Enzyme Cocktails.
Clicking the links above in order from the top will take you to the press releases. There you will find links to more details about Zhang’s and the ORNL work.
This research offers the other hand some interesting questions. The remains from the reaction, such as carbon and the minerals would be accumulative in the tank. Those remains might be quite valuable, as they haven’t been heated to ignition. The issues of exchanging them out at a refill would seem at first thought to be less than difficult and essentially harmless organics.
I have no doubt these scientists are on to something important. Whether or not the research leads to personal vehicle solutions is very much up in the air. Yet the concept is coming to fruition, in a market where raw cellulose and starches are common, the prospects look extremely good from larger transport to industrial applications. Free hydrogen is very useful, and there is a lot of it locked up in biomass every year over the face of most of the planet.
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Team this up with New Holland’s prototype fuel cell tractor – and you have a tractor that not only cuts brush – BUT EATS IT!
Nice site, nice and easy on the eyes and great content too.
Splendid, as a gentleman would say. Brilliant work on this writing. I sincerely appreciate it ;).