Seaweed biofuel farms have come a step closer to reality with an improvement in the way seaweed sugars can be converted to ethanol. Dried seaweed can be fermented to produce ethanol but breaking down galactose, the dominant sugar in seaweed, is a slow process.
Now, researchers have modified the expression of three genes of the yeast Saccharomyces cerevisiae, which is used in the fermenation process tobreak down sugars to ethanol. The improved strain creates more enzymes, leading to a 250 per cent increase in the rate of galactose sugar fermentation compared with a control strain, according to a paper in the current issue of Biotechnology and Biongineering (March).
Yong-Su Jin, one of the study's authors, and a researcher at the University of Illinois at Urbana-Champaign, United States, told SciDev.Net that his group will now explore the feasibility of harvesting and fermenting seaweed on large scales, which may involve cultivating plants along arrays of floats to ensure they receive enough sunlight.
Seaweed can produce biofuels in a more environmentally sustainable way than land-based crops, as it does not require fresh water or fertilisers, and it could potentially provide income for people in the small island nations of South-East Asia.
One problem facing land-based biofuel crops — such as rapeseed in Europe and palm oil in South–East Asia — is food security, as they may use land that could instead be used to grow food crops. They also require vast amounts of water at a time when water supply systems are becoming increasingly strained.
'The natural, obvious choice [for biofuels] is marine biomass,' said Jin, adding that seaweed is abundant near shorelines and is already harvested by many nations for food and medicine. It could also act as a sink for excess nutrients from nearby fish farms, according to Peter Schiener, who works on BioMara, a UK–Irish project seeking to demonstrate the feasibility of marine biofuels.
'Improvement of the conversion rate from galactose to ethanol certainly helps in increasing yields and making the whole process more economical,' said Schiener. Any country with a coastline could exploit marine biomass as a fuel resource, he added. 'Nations such as Chile, Brazil, India and China certainly have something to offer here.'
But Paul Dupree, a biofuels specialist at the University of Cambridge, United Kingdom, warned that practical challenges lie ahead. 'Sea-based farming may have the benefit of not competing for land and water supply with farming for food. [But] it has the disadvantage of being costly, due to the difficulty of maintaining and harvesting seaweed in ocean waters.'