Grass and straw preperation (GuS-Preperation)

The structure and consistence of the substratum used in a digester has a fundamental effect on the quantity of the gained gas. Substances such as lignin and cellulose are not biodegradable by bacteria using anaerobic fermentation. Furthermore, easily biodegradable organic substances cannot be reached by these bacteria when being coated with lignin or cellulose.

Our thermo-mechanical grass- and straw digestion procedure (GuS- Preperation) improves the biological availability of persistent substances.

Due to this milling the original substance achieves a larger working surface so that the bacteria are enabled to digest the substrata more intensively.

The grade of milling is influenced by the opening of the port at the outlet of the twin screw extruder. The narrower it is, the higher is the success in milling during the GuS-Preparation.

The illustration demonstrates that due to the GuS-Preperation the methane yield of grass silage is noteworthy heightened. The results of the gas yield are presented in litre per kilogramme organic dry substance (1 N / kg organic dry substance). In addition, the GuS-Preperation affects the chronologically process of the biogas production. Substrata which are prepared with the GuS-method show a considerably faster increase of the methane yield; due to the milling of the grass silage by dint of the twin screw extruder the curve displays a longer exponential lapse and a higher yield is reached faster in contrast to the original although the period of fermentation is equal.

The acceleration of the biodegradability leads to the achievement of the final value of the original by the grass silage already at the eighth day out of 30 test days.

By the use of the GuS-Preparation organic substances can be made better available for the bacteria, because the working surface of the particles is enlarged and organic substances are set free respectively. In the experiment the methane yield compared to the starting material could be increased up to 26%.

Further positive effects of the GuS-Preparation:

• obviation / lowering of floating layers in digesters
• cutback of the time of stirring in the fermenter
• faster and better homogeneity
• cutback of the stressed farmland for the provision of substrata (renewable resource) for the production of biogas