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Solving straw issues

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As a feedstock, straw has a long retention time due to its high fibre content. Pretreatment technology can provide a solution for biogas producers.

The ever-increasing need to reduce production costs or comply with increasingly stringent biomethane regulations is pushing biogas plants — particularly those that use agricultural biomass — to re-use by-products that have always been considered as waste from the main crops, such as straw.

However, unlike traditional biogas crops, such as corn silage, straw has higher fibre content. Because of this, straw has a fairly long retention time before being digested by bacteria, an amount of time that biogas plants, designed to be fed with energy crops, often can’t guarantee. With such low retention times, the straw is not digested by bacteria and normally tends to gather on the surface. This arrangement leads to the development of surface crusts, which compromises the hydraulic management of the system and the mixing in the digesters.

For this reason, it is necessary to use a pretreatment system can efficiently break-up, increase the contact surface and reduce the...

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