Science - September 26, 2009

Highway to green electricity

The inhabitants of the province of Groningen will draw a part of their electricity from the road shoulder or berm, starting from Monday. Is this as sustainable as expected? Alterra will be leading the experiment to find out.

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The Groningers are prepared for the experiment. Or are they? The poster publicizing the event is as striking as it is misleading: a pole with a power point sticking out of a berm. But it's not as simple as it looks. In fact, between berm and power point lie several steps. The green energy in Groningen will be extracted in a generator which runs on biogas. The gas will be produced by fermentation of mowed berm debris. To be exact, it is co-fermentation. Berm debris will be fermented together with animal manure, potato fibre and wheat yeast concentrate, explains Phillip Ehlert from Alterra.
 732 years of computer use
The fermenter is located in the small village of Lellens in Groningen. That's where the experiment will begin on Monday. The set-up can ferment four tons of mowed debris from the berms along the N360, N46 and N993 daily. This process will produce biogas. How much? That has yet to be seen, said Ehlert, not wanting to commit himself. The province itself is less reserved. It has estimated that the berms can provide 400 tons of mowed debris each year, enough to provide lighting for an entire Groningen household for 198 years, to wash their clothes for 462 years, or to meet their computing needs for 732 years. All from the berms, and Groningen has 10,000 tons of vegetation growing along its roads each year.
Balance
Groningen Province is convinced that fermentation of berm debris will have environmental benefits. 'It may lead to less CO 2 emission', but Ehlert does not consider the facts cut and dried. 'Trial studies have shown us that this is sustainable.' The current sustainability study is the gist of Alterra's role in this project. The Groningen berm debris has hitherto been composted; CO 2 is produced in the process.  While combustion of biogas also releases CO 2 , the resulting electricity can reduce the use of fossil fuels. Further research has to be carried out to establish how this balance works out with composting and with fermentation. 
Experiments
Ehlert says that there is still a lot of research to be done. 'Berm debris is not easy to work with', he explains. Quality and usability depend on the type of vegetation, the time of the year when mowing takes place, and whether mowing is done close to the edge of the road. The environmental aspects of the compost is also important. It has to be clean enough for use as soil manure. The researchers have up to next spring to complete their assignment.

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