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More Sustainable Energy from Agriculture is Possible

The Bioenergy Site – August 2011


With the aid of improved technology, biomass from agriculture can contribute even further to sustainable energy production via more efficient biogas production


Scientists from Aarhus University have studied a method for pre-treating biomass that can increase methane yield in the biogas plant by up to 20-30 per cent.
With extrusion biomass is subjected to mechanical treatment in a continual process.
The raw material is fed into one end of the extruder and transported through the system by screws. During the process the material is mixed, fragmented and heated.
The process causes the plant fibres and cell walls to be torn apart so that sugars and other compounds become more readily available to the bacteria that digest them during the biogas process.
The scientists investigated how much extrusion can increase methane production during biogas production. To that aim, they studied five different kinds of biomass with dry matter contents of over 20 percent, including straw, grass, pig manure, cattle manure and deep litter.
The scientists registered the biogas potential and size distribution of the samples and the increase in temperature and energy consumption during the process.
The results showed that extrusion separated the biomass and increased the temperature due to friction heat. Large particles were affected the most. Extrusion improved digestion of poorly digestible organic compounds. Some organic compounds, that were normally not digestible, were also broken down.


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