
Contact Us       Consulting       Projects       Our Goals       About Us
home / Archive
Nature Blog Network






Creative Commons License

Thursday, July 17, 2008

Researchers develop two-stage process for optimal biohydrogen production

Researchers have combined the efforts of two kinds of bacteria to produce hydrogen in a bioreactor, with the product from one providing food for the other. According to an article [*.pdf] in the August issue of Microbiology Today, this technology has an added bonus: leftover enzymes can be used to scavenge precious metals from spent automotive catalysts to help make fuel cells that convert hydrogen into energy.

Hydrogen has three times more potential energy by weight than petrol, making it the highest energy-content fuel available. Research into using bacteria to produce hydrogen from waste biomass has been revived thanks to the rising profile of energy issues.

According to the researchers, the UK throws away a third of its food, wasting 7 million tonnes a year. The majority of this is currently sent to landfill where it produces gases like methane, which is a greenhouse gas 25 times more potent than carbon dioxide. Following some major advances in the technology used to make biohydrogen, this waste can now be turned into valuable energy.

Two-stage process

There are special and yet prevalent circumstances under which micro-organisms have no better way of gaining energy than to release hydrogen into their environment. Microbes such as heterotrophs, cyanobacteria, microalgae and purple bacteria all produce biohydrogen in different ways, says Dr Mark Redwood from the University of Birmingham.

When there is no oxygen, fermentative bacteria use carbohydrates like sugar to produce hydrogen and acids. Others, like purple bacteria, use light to produce energy (photosynthesis) and make hydrogen to help them break down molecules such as acids. These two reactions fit together as the purple bacteria can use the acids produced by the fermentation bacteria. The table (click to enlarge) gives an overview of different biohydrogenic micro-organisms. Note the two fundamental bioconversion pathways, based on fermentation and photosynthesis.

Professor Lynne Macaskie's Unit of Functional Bionanomaterials at the University of Birmingham has created two bioreactors that provide the ideal conditions for these two types of bacteria to produce hydrogen.
By working together the two types of bacteria can produce much more hydrogen than either could alone. A significant challenge for the development of this process to a productive scale is to design a kind of photobioreactor that is cheap to construct and able to harvest light from a large area. A second issue is connecting the process with a reliable supply of sugary feedstock. - Dr Mark Redwood
With a more advanced pre-treatment, biohydrogen can even be produced from the waste from food-crop cultivation, such as corn stalks and husks. Tens of millions of tonnes of this waste is produced every year in the UK. Diverting it from landfill into biohydrogen production addresses both climate change and energy security:

The University of Birmingham has teamed up with Modern Waste Ltd and EKB Technology Ltd to form Biowaste2energy Ltd, which will develop and commercialise this waste to energy technology.
In a final twist, the hydrogenase enzymes in the leftover bacteria can be used to scavenge precious metals from spent automotive catalysts to help make fuel cell that converts hydrogen into electricity. So nothing is wasted and an important new application can be found for today's waste mountain in tomorrow's non-fossil fuel transport and energy. - Professor Lynne Macaskie
Biohydrogen also has an advantage that might make it the fuel of the future: it can be made carbon-negative. When the CO2 that is released during the production stage is captured and sequestered, the fuel becomes carbon-negative, and using it would mean you would be taking CO2 out of the atmosphere (previous post).

According to several reports, biohydrogen remains the most competitive way to produce the fuel, as compared to hydrogen made from other renewable sources like wind or solar, which never succeed in turning it into a carbon-negative fuel and which remain very costly (see the recent EU HyWays report). However, the competitive bio-based method draws on the gasification of biomass, not so much on the microbial biohydrogen production method.


Mark Redwood and Lynne Macaskie, "Life’s a gas... and it’s hydrogen" [*.pdf], Microbiology Today, August 2008

Biopact: EU HyWays report concludes biomass least costly and preferred renewable for hydrogen production; hydrogen can replace 40% oil by 2050 - February 26, 2008

Biopact: Carbon-negative cars could mitigate 646% of global transportation CO2 emissions - June 20, 2008

Biopact: Carbon-negative bioenergy making headway, at last - June 06, 2008

Article continues