Science - February 12, 2009

ENERGY FROM GREEN SLURRY

They already provide us with the raw material for food, cattle feed, plastics and paint. But Professor René Wijffels has high hopes that algae will soon also be providing us with biofuels that don't compete with food production. He's working on setting up a pilot factory. From Food or fuel to food AND fuel, thanks to an expensive green slurry.

The alga <em>Dunaliella salina</em>
Eneco, Essent, Nuon and Delta are enthusiastic, says Professor of Bioprocess Engineering René Wijffels. These energy providers are contributing to the salaries of seven PhD students who are going to try to bring the cost price of a kilo of dried algae down from four euros to forty cents, and make it profitable to produce algae for biofuels. The companies are in Wijffels’ knowledge network, along with other potential users of algae: Unilever, Dow Chemical, Friesland Campina and Syngenta. The programme is part of the work of Wetsus, a centre for sustainable water technology in Leeuwaarden.

As well as research, some of the companies want to run a pilot of a few hectares. ‘They want advice on this, and were referred to Wageningen UR. That kind of scale is too risky at the moment, I think – we need an interim phase. My AFSG colleagues and I are now talking with several companies about a pilot factory of 120 square metres in Wageningen. We are in discussion with ministries and provincial governments about cost-sharing.’

The pilot factory is a test case for large-scale energy harvesting from algae, but algae are already being cultivated for several other purposes. Wijffels draws a pyramid. At the top are specific nutrients and fatty acids that you can extract from certain algae – such as beta carotene and omega 3 fatty acids. A kilo of algae used for this purpose is worth four to five hundred euros. One level down are the raw materials for the chemical industry, then comes cattle feed, and right at the bottom of the pyramid come biofuels. According to Wijffels, the lesson is that you have to get several ingredients out of algae to make them economically viable.
And that is exactly what is happening. The Wageningen alumnus Carel Callenbach and his company Ingrepro are constructing algae ponds and reactors on several locations, including at Akzo in Delfzijl. ‘We produce fatty acids from algae, which Akzo uses for coatings’, he says. The entrepreneur is also involved in Wijffels’ research programme, and Wageningen PhD students are regular visitors at his company. In all his projects he looks for clever ways of creating closed loop systems, so that the algae turn waste products into raw materials – the cradle to cradle principle.

Algae are supremely suited to this task as they grow on manure and turn CO2 into oxygen as they grow. Wijffels buys the manure and CO2 for his algae bioreactor. But Callenbach is given them by companies – and this solves a problem for them too. Like this, his AlgaePro concept meets the needs of pig farmers with too much manure and town councils with too much waste. Such linkages bring down the production costs tremendously. ‘In integrated production, I’m now down to 35 cents per kilo of dried algae’, says Callenbach.

With this sort of practical experience, is a pilot factory in Wageningen really necessary? Yes it is, says Lodewijk Westerling of the Amsterdam-based Spring Associates, another participant in the research programme. Spring Associates does research for KLM into the feasibility of fuelling planes with algae. Westerling is considering cultivating algae made up of about thirty percent oil, which are usable for kerosene. The rest of the algae should then be used for something else.

Westerling wants a production design for a low-cost algae bioreactor which produces significantly more energy than it costs to run. This requires knowledge in the divergent fields of biology, algaculture and process technology: knowledge which could come together nicely in Wijffel’s planned pilot project. Large-scale and energy-efficient algae production is the aim of another participating company, Neste Oil, too. This originally Finnish oil company has a patent for the processing of vegetable oil into a synthetic biodiesel. Unlike conventional biodiesel, which can only be added to mixtures to a maximum of five percent, Neste Oil's biodiesel can be used unmixed, says Henrik Erämetsä of Neste Oil. ‘We are building new factories in Europe and Asia, and in 2011 we shall need two million tons of vegetable oil to process into diesel’, says Erämetsä. ‘This brings the Food or fuel issue closer and closer, so we are looking for raw materials that could replace rape oil and palm oil. We are taking part in Wetsus to stimulate research into this.'

Research and implementation seem to be playing leapfrog, as Callenbach is setting up an algae plant at a palm oil factory in Malaysia. Following a tried and trusted recipe, he wants to use the waste from the palm oil factory to produce biogas and to grow algae. The clean, oxygen-rich water from the algae ponds will go to the fish farmer round the corner. Once the algae have been processed into biodiesel, the two-pronged enterprise will be producing both food ánd fuel.

OW DO YOU GROW ALGAE?
In a pond : A basin of thirty to forty centimetres deep with a paddle to stir the algae slurry. The system is cheap but not efficient: only one percent of the sunlight is transformed into chemical energy by the algae, using photosynthesis.

In a tube reactor : a one-hundred-metre-long, five-centimetre-wide transparent tube that lies horizontally on the ground. It can convert two percent of the sunlight into energy, but the disadvantage is that because the algae convert CO2 into oxygen, oxygen builds up in the tube reactor and restricts the growth of the algae.

Stacked tube reactor : reactor tubes are stacked up in each other’s shadow, so that the light intensity goes down. This leads to a photosynthesis efficiency of three to four percent.

Vertical reactor : The algae are in panels standing in rows. Efficiency can reach about five percent; researchers have established a theoretical maximum of ten percent. René Wijffels: ‘We started at one percent and now we’re half way to the maximum possible.’

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