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Fast track from straw to energy

The effective use of straw in biogas production can be increased significantly with a new technology researchers at Aarhus University are helping to develop and test for commercial use.

2012.03.15 | Janne Hansen

A project at Aarhus University will demonstrate a very efficient use of straw for biogas production. Photo: Jesper Rais, AU

Researchers from Aarhus University are participating in a project to demonstrate the efficient and large-scale conversion of straw into biogas. The project will use a newly developed method for the pre-treatment of straw before it is added to the biogas plant.

The pre-treatment of straw before it is added in the biogas plant means that it can be digested with the manure and the biogas yield can be improved.

On an annual basis up to10,000 tonnes of straw will be pre-treated and digested along with manure at the large experimental biogas plant at AU Foulum, Aarhus University. A full-scale straw pre-treatment facility will be built for the purpose.

The system can be used for both biogas and bioethanol and other biofuels.

New energy efficient method
The process therefore requires no additional water. This means that the method uses a minimum of water and achieves a high accessibility of straw sugars.

With this method dry straw can be used in the reactor. With conventional methods, you would normally need to add about 5-10 times as much water as straw in the pre-treatment phase. So for each 10,000 t of straw, up to 100,000 tonnes of water would have been needed.  This should be seen in relation to the 30,000 t manure that the Aarhus University biogas plant can handle in a year.

Such a huge consumption of water has so far been a major hindrance to the large-scale use of straw for biogas production.

The new method, which the project will be testing and refining on a larger scale, can be used for other dry by-products from food production, such as waste from sugar cane plantations. In theory, one tonne of sugar cane bagasse can produce up to 300 l of ethanol, which would be a doubling of the current extraction of energy from sugar cane. The project may therefore have considerable potential in Brazil, China and other countries with a large production of sugar cane.

The project is funded by the Energy Technology Development and Demonstration Programme (EUDP) and conducted in collaboration with the companies BioFuelTechnology ApS who are managing the project, and C.F. Nielsen A/S.

Further information: Henrik B. Møller, Department of Engineering, telephone: +45 8715 7646, mobile: +45 4053 1596, email: HenrikB.Moller@agrsci.dk

Research, Bioenergy, Biomass, DCA