'Dirty' biomass offers fast, cheap route to hydrogen fuel
08 April 2015
Researchers discover a way to create hydrogen fuel via a biological process that uses abundantly available corn stalks, cobs, and husks - so-called 'dirty' biomass.
“This means we have demonstrated the most important step toward a hydrogen economy – producing distributed and affordable green hydrogen from local biomass resources,” says Virginia Tech's Professor Percival Zhang, who led the research.
The Virginia Tech team, which also includes Dr Joe Rollin, a former doctoral student of Zhang’s, already has significant funding for the next step of the project, which is to scale up production to a demonstration size.
The work builds upon previous studies Zhang’s team did with xylose, the most abundant simple plant pentose sugar, to produce hydrogen yields that previously were attainable only in theory.
Unlike other hydrogen fuel production methods that rely on highly processed sugars, the Virginia Tech team used 'dirty' biomass — the husks and stalks of corn plants (corn stover) — to create their fuel. This reduces the initial expense of creating the fuel and enables the use of a fuel source readily available near the processing plants, making the creation of the fuel a local enterprise.
Rollin used a genetic algorithm along with a series of complex mathematical expressions to analyse each step of the enzymatic process that breaks down corn stover into hydrogen and carbon dioxide. He also confirmed the ability of this system to use both sugars glucose and xylose at the same time, which increases the rate at which the hydrogen is released. Typically, in biological conversions, these two sugars can only be used sequentially, not simultaneously, which adds time and money to the process.
One of the biggest hurdles to widespread hydrogen use is the capital cost required to produce the fuel from natural gas in large facilities. Distribution of the hydrogen to users of fuel cell vehicles is another key challenge.
Rollin’s model increased reaction rates by threefold, decreasing the required facility size to about the size of a petrol station, which reduces associated capital costs. The dominant current method for producing hydrogen uses natural gas, which is expensive to distribute and causes fossil carbon emissions.
To produce distributed hydrogen at affordable costs, product yield, reaction rate, and product separation must be addressed. In terms of product yield, the use of cell-free artificial enzymatic pathway not only breaks the natural limit of hydrogen-producing micro-organisms by three times but also avoids complicated sugar flux regulation.
The team also increased enzymatic generation rates. This reaction rate is fast enough for hydrogen production in distributed hydrogen-fuelling stations. The achieved reaction rate is at least ten times that of the fastest photo-hydrogen production system.
The reaction the researchers studied takes place at modest conditions. This means that hydrogen can be easily separated from aqueous reactants and enzymes. Also, enzymatic reactions such as those being used in this system generate high-purity hydrogen, perfect for hydrogen fuel cell vehicles.
The modest reaction conditions also indicate the feasibility of low-capital requirements for building distributed hydrogen generating and fuelling stations based on this technology.
“We believe this exciting technology has the potential to enable the widespread use of hydrogen fuel cell vehicles around the world and displace fossil fuels,” says Rollin.