The US Department of Energy's National Renewable Energy Laboratory (NREL) has managed to extract more fuel from algae biomass through a new biorefinery process.
In traditional processes, the algae produce lipids that get converted into fuels. NREL, however, says that through certain techniques microalgal biomass can produce carbohydrates and proteins in addition to lipids.
In previous work, the lab used a solid-liquid separation process to convert the carbohydrates to fermentable sugars, which can then be used to produce ethanol. A substantial part of the sugars, up to 37%, were lost during that process, though.
The new research skips the separation process and exposes all algae components directly to fermentation conditions. Thus both ethanol and lipids can be recovered simultaneously. After upgrading the lipids to renewable fuels, scientists achieved a total fuel yield of 126 gallons gasoline equivalents (GGE) per tonne of biomass, 32% more than the yield from lipids alone, at a cost of USD 9.91 (EUR 8.77) per GGE in the case of Scenedesmus acutus.
The new process, dubbed Combined Algal Processing (CAP), could reduce the cost of algal biofuel production by nearly USD 10 per GGE compared to a "lipids only" process, says NREL. This is far from competing with petroleum, but it shows a way forward to achieve that goal, the lab says.