The aquatic plant is a large, fast growing green algae that can be found near shores (profile at the AlgaeBase; image, click to enlarge). It thrives in nutrient-rich zones, especially there where water is contaminated by nitrogen runoff from agriculture. Interestingly, its sugar content is relatively high, making it a potential feedstock for cellulosic ethanol production.
Michael Bo Rasmussen of the National Institute of Environmental Research at the University of Aarhus has already carried out two tests with the algae and thinks harvesting them as a biomass source might make sense. The species grows fast, doubling its biomass every three to four days. Rasmussen estimates the theoretical yearly yield to be between 200 and 500 tons of wet biomass on a 'hectare' basis (even though comparisons with terrestrial plants are difficult). Denmark's total potential would be an annual production of around 80,000 to 100,000 tons. Importantly, the algae doesn't need fresh water to grow and it occurs near shores, making it accessible. The seaweed could be harvested in its wild form, and thus contribute to re-oxygenating zones that have been invaded by the algae.
Large scale cultivation
Like Japanese researchers, the Danish scientists are thinking of cultivating the algae on a large scale. Traditional seaweed cultivation techniques, refined in Japan, could be modernized and applied to a modern aquacultural biomass industry. Ulva lactuca thrives when fed with liquid fertilizer and carbon dioxide, the greenhouse gas. Denmark's economy generates an excess of both these nutrients. Rasmussen estimates that an optimal production process based on feeding the algae the right amount of fertilizer and CO2, could yield up to 500 tons of biomass per hectare. But for the time being, such a high-tech form of aquaculture would be prohibitively expensive, the researcher says:
energy :: sustainability :: ethanol :: biomass :: bioenergy :: biofuels :: algae :: seaweed :: Denmark ::
Rasmussen's project is one of the proposals selected for funding by the Aarhus Research Foundation, which is freeing up 48 million kroner (€6.4/US$8.8 million) for 16 different projects over the 2007-2011 period.
The idea of harvesting algae from the open ocean keeps popping up each time oil prices reach records. In the 1970s, several similar ideas were launched and received modest funding, both in the U.S., Japan and the EU. Scientists can now pick up on the research of their older collegues. Recently, a company that used to work on micro-algae production in closed photobioreactors decided to do just that and started looking at harvesting biomass from algae blooms found in the open ocean (previous post).
Some of these aquacultural projects may make sense over the ultra-long term provided major R&D breakthroughs are made. However, ideas like growing algae in closed photobioreactors are not feasible (more here) because uncompetitive; likewise, growing the micro-organisms in open ponds requires serious advances in biotechnology to bring costs down by at least a factor of 20.
Picture: Ulva lactuca Linnaeus. Photographer: Katrin Österlund © Katrin Österlund. Oliveira, E., Österlund, K. & Mtolera, M.S.P. (2005). Marine Plants of Tanzania. A field guide to the seaweeds and seagrasses. pp. 267. Stockholm: Botany Department, Stockholm University. Credit: AlgaeBase.
Futura-Sciences: Une idée danoise : le biocarburant à base de laitue de mer - July 25, 2007.
University of Aarhus: Stort potentiale i biobrændstof fra havet - June 222, 2007.
AlgaeBase: Ulva lactuca Linnaeus profile.
Biopact: Scientist skeptical of algae-to-biofuels potential - interview - July 18, 2007
Biopact: Harvesting algae blooms from the open ocean - March 01, 2007