Sugar cane is currently used to produce large quantities of biofuel in Brazil

Credit: Wikipedia

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SYDNEY: A new process that runs on biomass and renewable energy could produce enough fuel to power all cars in America, say the U.S. scientists who proposed it today.

The method, enough to fuel the needs of other forms of transport too, recycles all the carbon dioxide (CO₂) usually wasted in the production of biofuels, making it far more efficient than previous techniques.

Transportation in the USA consumes a massive 16 per cent of all oil produced in the world, and coughs out 8 per cent of global CO₂ emissions from fossil fuels. Oil prices and concerns over global warming have made clean biofuels a hot topic of research as an alternative to petroleum.

The so-called ‘hybrid hydrogen-carbon process’ could potentially produce diesel fuel from coal or biomass, without adding to the total amount of CO₂ in the atmosphere. Biomass can be any plant or animal matter - typically biofuels are produced from crops such as soybeans or sugar cane. However, the process of converting biomass to fuel is inefficient, with two-thirds of it lost as CO₂ during conversion.

The new process, proposed by chemical engineers led by Rakesh Agrawal of Purdue University in Indiana in a paper published in this week's edition the U.S. journal Proceedings of the National Academy of Sciences, is unique because it uses hydrogen from renewable energy sources to trap all the CO₂ produced when making biofuel.

Agrawal’s method differs from current biodiesel production by reacting the wasted CO₂ with hydrogen, creating more diesel fuel. The hydrogen for this part of the reaction could be gleaned from water molecules using energy from non-fossil energy sources such as solar or nuclear power.

The gains in efficiency are so great that the same volume of biomass, previously predicted to satisfy only 30 per cent of yearly U.S. transport needs (1.239 billion tonnes), might now be enough to satisfy the entire industry, wrote the researchers. That amount of biofuel could be produced on an area covering 10 per cent of the U.S. landmass, they said.

Though running cars on diesel fuel would still generate CO₂ emissions, that CO₂ could effectively be reabsorbed from the atmosphere by growing more biomass - essentially creating a balanced CO₂ cycle.

“This is a much cleaner process than other coal or biomass-to-fuel process options,” Agrawal told Cosmos Online. It also offers the big benefit that existing infrastructure can be used to deliver the fuel – a benefit which “alternative energies such as electricity and hydrogen are, as yet, unable to deliver,” he said.

Agrawal predicts that, using the process, biomass alone could satisfy our fuel needs when coal runs out. He also argues that it could lead to birth of a new “hybrid hydrogen-carbon economy".

For trains, planes, and automobiles, the researchers point out that the biggest challenge of energy produced by nuclear, solar, wind and other non-fossil fuel sources alone is storage. “For a given on-board storage space, the lower storage energy densities of batteries and hydrogen severely limit the driving distance [as opposed to gasoline or diesel]. Also, the energy and cost associated with the delivery of these energies is a large fraction of the cost.”

“This is an interesting concept which has been talked about in scientific circles for a while,” commented Behdad Moghtaderi, of the University of Newcastle’s Priority Research Centre for Energy in New South Wales. Though it could succeed in the U.S., “the weakest link of the proposal, is the production of hydrogen,” he said.

The hydrogen used in the new process would be generated by splitting water molecules using solar, wind or nuclear power. “This isn’t viable in an Australian context simply because we don't have sufficient water resources to enable the production of hydrogen at reasonably large scales.”

The researchers agree that hydrogen production is as an area that needs more consideration. To implement the new chemical processs, cost-effective hydrogen production methods and biomass ‘gasifiers’ that can use recycled CO₂ must be developed, they said.

Currently the transportation sector generates huge volumes of carbon emissions, and there has been much discussion about technologies that could remove carbon from the atmosphere to balance this (see The race for Branson's millions, Cosmos Online).

Cosmos online approached the industry-funded Cooperative Research Centre for Greenhouse Gas Technologies, in Canberra, to comment on how the new findings might impact on the industry concerned with removing carbon from the atmosphere. However, they declined to talk to us.

More information:

National Biodiesel Board (U.S.)
Rakesh Agrawal's university website
When it becomes available later this week, use this link to access
Agrawal's paper in the Proceedings of the National Academy of Sciences.