The Telegraph
Since 1st March, 1999
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Making hydrogen, naturally
An experimental hydrogen-fuelled car from Toyota, and (above) Percival Zhang

Living cells usually do not waste energy or resources, and so only make substances that are useful to them. From this one can deduce that no organism makes something that is not useful to it. This is why we cannot generally find biological sources for substances that are useless to living beings. Does it mean that we cannot make them using biological principles'

Consider an obvious example. Hydrogen is a great energy source for modern lifestyles, provided we know how to make it cheaply and use it safely. The best way is to find a biological source for the gas, but unfortunately, hydrogen is not useful to a living being. Living cells get their energy from elsewhere, a molecule called ATP. This is why it is difficult to find bacteria that can synthesise hydrogen from natural raw materials. However, some scientists are now finding methods to make hydrogen naturally, by combining natural enzymes in innovative ways. This is a new science called synthetic biology.

Recently, Percival Zhang, assistant professor of biological systems engineering at Virginia Tech in the US, and his collaborators at two other US labs announced that they had found an innovative method to make hydrogen. Their raw material was cellulose, and they used 13 enzymes in a combination never before seen in nature. These enzymes broke down cellulose and water, producing carbon dioxide and hydrogen. Zhang reckons that he can get to a commercial product — for example, one that can be used in an automobile — in five to 10 years. “It is like the airplane of the Wright Brothers,” says Samir Brahmachari, director of the Institute of Genomics and Integrative Biology (IGIB) in Delhi. “It will take a long time to become a commercial product.”

Many scientists and economists say that current technologies do not permit the use of hydrogen as a fuel in automobiles. There are some fundamental barriers to its widespread use. We need to learn to make hydrogen cost effectively, lowering the production cost four times. Fuel cells, a type that produces energy from hydrogen and oxygen, are even less useful now, as they need to be 10 times less expensive. Also, we need to produce hydrogen without using fossil fuels, and learn to transport it cheaply.

The current source of hydrogen is natural gas, which is expensive and dangerous to use. Since natural gas ultimately comes from the bowels of the earth, it is not carbon neutral — which means using it increases carbon dioxide emissions. We could solve this problem if we use biomass, which is carbon neutral because the carbon dioxide in it came from the atmosphere only recently. We know how to convert biomass into hydrogen, but at a high cost using chemical methods. Chemistry is not as intricate and efficient as biology.

This is why many scientists are looking for biological methods to make hydrogen. The maverick scientist Craig Venter, who was a key figure in the sequencing of the human genome, is looking at the most inaccessible places to find some microbes that can make hydrogen. Scientists like Venter expect to find not the perfect microbe but a set of genes that may be useful; they could then tweak and combine the genes and create a biological factory to produce hydrogen. It is no accident that Venter’s company is called Synthetic Genomics.

Some Indian labs are also trying to develop hydrogen through biological means. IGIB in Delhi has isolated some useful genes from bacteria, but it is yet to combine them in ways that could make hydrogen effectively.

In theory, cellulose is a great source of hydrogen. In practice, it is difficult to make hydrogen out of it without spending a lot of energy and money. Engineers generally use a chemical process at high temperature and pressure, not the ideal conditions to create inside an automobile. “Our technique works at normal temperature and pressure,” says Zhang. He isolated 13 enzymes that can be used in sequence to convert cellulose and water into hydrogen and carbon dioxide. The enzymes came from spinach, rabbit, bacteria, yeast and other widely different organisms.

Zhang had help from scientists at Oak Ridge National Laboratory and Georgia University. He is building something that can be used to produce hydrogen inside an automobile. This hydrogen will then combine in a fuel cell with oxygen to produce electricity and water. This water will then be used again to produce hydrogen. Since the raw material is cellulose, the process is carbon neutral, which means that it neither increases nor reduces the carbon dioxide in the atmosphere. To be of use as a regular energy source, Zhang has to reduce the cost and increase the efficiency more than a thousand times. “This is very easy,” says Zhang, who thinks that the only barrier to commercialisation of this research now is funding.

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