Increase and regulation of biogas production

A main experience has been that a number biomass types may contain stones and metal parts, and that it is very important that the feeding system can handle this kind of compounds, especially if deep litter is to be used. The so far most successful system was installed by Bånlev Biogas, where deep litter is mixed with slurry and stirred in a small primary tank in which objects can sink to the bottom without major problems.
The timing of the project has been good, as simultalneously considerable interest for using deep litter has emerged within the biogas business. It seems that the preferred method is to stirr deep litter with manure in a tank before pumping into the digesters
One of the questions that arose along the way, it is the one about the need for crushing or shredding of solid biomass. Both Linkogas and Bånlev have concerns about increasing volumes without further pretreatment, as they fear building of floating layer in the digesters. Both plants consider additional investments in equipment for shredding. Vegger, which is the third company in the project decided, based on the same considerations, to purchase a newly developed chain crusher from the Danish
company, Xergi .
Aarhus University has investigated the possibility of seasonal and daily regulation of biogas production using alternative solid biomass types. The results show that especially seasonal adjustment is possible by increasing the feeding of for example deep litter during winther seasons. Not all solid biomass is equally suitable, for example, large amounts of fiber fraction from pig manure may lead to process inhibition due to high concentrations of nitrogen. Production “on-demand” is also possible, but it requires more easily digestible resources such as corn silage or sugar beets. If such biomasses are used the possibilities of production regulation will be defined by the upper limit for dry matter handling in the plant