Biofuels from the sea

Seaweed may prove a viable future biofuel, especially if harvested in summer. The use of kelp (laminaria digitata) could provide an important alternative to terrestrial grown biofuels. However, the suitability of its chemical composition varies on a seasonal basis. Harvesting the kelp in July, when carbohydrate levels are at their highest, would ensure optimal sugar release for biofuel production.

“The storage carbohydrate and soluble sugars get converted into ethanol in the fermentation process, so we need as much as possible,” says Jessica Adams, a lead researcher at Aberystwyth University. “Metals can inhibit the yeast too, so we also want these to be as low as possible.” After collecting monthly samples of kelp from the Welsh coast, researchers used chemical analysis to assess the seasonal variability. Their results would be presented at the Society for Experimental Biology Annual Conference in Glasgow next month.

Kelp can be converted into biofuels in different ways, including fermentation or anaerobic digestion-producing ethanol, and methane or pyrolysis (a method of heating the fuel without oxygen), which produces bio-oil. The chemical composition of the seaweed is important for both these processes.

Research into biofuels has focused on terrestrial plants. However, these have the serious drawback of the conflict between using land to grow food or fuel. Marine ecosystems are an untapped resource that account for over 50 per cent of global biomass. Seaweeds are capable of producing more biomass per square metre than fast-growing terrestrial plants such as sugarcane.