A team of US scientists has developed a way to extract hydrogen from any kind of plant matter. The discovery represents an important breakthrough which could pave the way for hydrogen to become a low-cost, mainstream fuel of the future.
Currently, the most common method for manufacturing hydrogen involves ‘steam reforming’ natural gas/methane (CH4) in the reaction: CH4 + 2H2O = CO2 + 4H2. However, the process needs high temperatures, and releases carbon dioxide. Another method is to split water into hydrogen and oxygen by electrolysis. Although there are no resultant carbon emissions, this process still requires a considerable amount of energy.
The commercial production of hydrogen gas from biomass was previously hampered by the high cost of the processes used and the relatively low quality of the end product. The team at Virginia Tech University has been researching new enzyme combinations, and engineering enzymes with desirable properties, for seven years. They have now succeeded in harnessing hydrogen from xylose, the most abundant simple sugar found in plants.
The energy stored in xylose splits water molecules, yielding high-purity hydrogen that can be used by proton exchange membrane fuel cells. Even more appealing, this reaction – using a customised cocktail of 13 enzymes, xylose, a polyphosphate and water – occurs at low temperatures (50°C), generating hydrogen with embodied energy that is greater than the chemical energy stored in xylose and the polyphosphate. The heat energy could be from waste heat, thereby further improving efficiency.
“If it can be done cheaply, this may develop into a very interesting alternative to the reformed hydrocarbons that make up the bulk of commercially produced and consumed hydrogen”, says Ross Gazey of the Pure Energy Centre in Shetland, which developed Britain’s first road-licensed hydrogen car.
The Virginia Tech researchers hope that extracting hydrogen from xylose will become commercially viable within three years.
Photo: Virginia Tech