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12/02/12
 

Fill it up on premium seaweed

Researchers are looking to turn sugars found in marine crops into biofuel, writes David Derbyshire

Off the northeast coast of China, the lines of floats stretch for miles across the sea. Each float is attached to a rope, and from each rope hang long heavy strands of seaweed. Every day boatmen paddle out to gather the slimy harvest, returning to shore overloaded.

The seaweed farm at Sanggou Bay is one of the biggest in the world and its rafts and ropes stretch for six miles. Soon, if scientists are right, its soggy crop could power our cars, lorries and buses.

China produces 9m tonnes of commercial seaweed a year — about half the global total. It is a hugely labour-intensive process, but the crop has many uses. It is an ingredient in food, textiles, cosmetics, printing and medicine.

Now researchers are developing ways to turn the sugars and starches it contains into cost-effective biofuel to replace conventional diesel and petrol from fossil fuels and green fuel made from land crops.

Using existing biofuel technology to process seaweed is prohibitively expensive, but the sums could add up if the costs fall and the price of fossil fuel continues to soar. It could become a valuable new crop around the coast of Britain.

The benefits of turning seaweed into liquid fuel are enormous. Unlike conventional biofuel crops, such as maize and sugar cane, it does not compete for space needed to grow food. This means its production puts no pressure on food prices. Also, it puts no temptation on developing countries to clear pristine forests.

While many biofuels are farmed intensively, and have a huge carbon footprint from fertiliser, water and transport, seaweed needs nothing more than salt water, light and space.

Researchers from the Bio Architecture Lab in Seattle announced last month that they had found a way to genetically engineer E.coli bacteria so that they break down seaweed to make sugars that can be processed for fuel.

And Novozymes, a Danish biotech company, last week announced a deal with India's Sea6 Energy to develop a process for producing fuel from the marine crop.

Seaweed has been harvested by mankind since the dawn of history and has been farmed for at least 400 years. In the 17th century, farmers threw bamboo branches into shallow seawater to attract the spores and cultivate the plant.

Large-scale cultivation is a recent phenomenon, however. Today most commercial production is in China, Japan, Indonesia and the Philippines. The favoured variety for eating — Saccharina japonica - is also a good source of the sugars that can be converted into fuel.

In China, seaweed is grown on "rafts" — 60-metre ropes kept afloat by plastic floats. Hanging from these are twometre ropes, weighed down with stones, to which young plants are attached. They take nine months to grow to full size.

It is estimated that one square foot of ocean is capable of growing 10 times more crops, in the form of seaweed, than the same amount of land.

Once harvested, there are various ways to convert seaweed into biofuel. The plant material must first be broken down into sugars, usually done by microbes or fungi. The sugars are fermented with yeast to produce alcohol. The alcohol is extracted from the mix, allowing the solids left behind to be used for animal feed or food supplements.

Seaweed can also be anaerobically digested, or broken down by microbes without the presence of oxygen to produce methane. This can be burnt to generate heat, or compressed to make liquefied natural gas.

There is nothing new about obtaining fuel from seaweed. In the 1960s and 1970s, American researchers showed methane could be extracted. However, their experiments were abandoned because of problems with growing the plant off the Californian coast.

The French have also experimented with seaweed farms off Brittany, while the Crown Estate, which owns almost all the sea bed out to 12 nautical miles from the UK coast, is planning a large-scale seaweed farm off Scotland.

Michele Stanley of the Scottish Association for Marine Sciences, believes the biggest challenge is not turning seaweed into fuel, but producing the marine plant economically.

Her team, based in Oban, is halfway through a four-year trial of seaweed cultivation. The best results come from brown seaweed, or kelp.

"We have a project looking at methane and ethanol and they are both feasible," she said."The big question in Europe is the cultivation costs.

"We can't compete with China on labour costs. They send men out on boats and they pull in the material by hand. We can't do that, so it's a question of getting costs down."

Novozymes believes the most productive farms will be in warmer waters, which helps to explain its research agreement with India's Sea6. The plan is to find efficient enzymes from Novozyme's library of chemicals and genetically modify bacteria to produce them in large quantities. They would then be mixed with seaweed in vats to release the sugars.

Lars Christian Hansen, Europe president of Novozymes, said: "The economics will be there on the technical side, but whether you can ...grow, collect and process the seaweed in an economic way is the question."

In the tropics, the process could be labour-intensive without being prohibitively expensive. In Europe, it would have to be automated because labour costs are high, he said.

Harvesting and processing are only part of the biofuel equation, however. The other big unknown is the impact of industrial-scale seaweed farms on marine ecosystems.

Stanley said: "It could be that it improves biodiversity because you establish a habitat for fisheries and you might leave part of the crop behind for fish. But there are potential negative impacts.

"If you pick the wrong areas, bits of biomass could sink to the sea floor and rot, which could create anoxic [lowoxygen] conditions. That's why we are going for a small pilot area so we can monitor what is happening."

Even if the trials in Britain and the work on enzymes are successful, the first commercial production will be at least three or four years away. "It could be the next decade," admitted Stanley. "But people are getting more interested."


Copyright David Derbyshire 2011