Application of hydrolytic enzymes for improving biogas feedstock fluidity

Abstract

The composition of feedstock for biogas plants has changed during recent years. There has been an increase in the share of energy crops and residue from agriculture. As a consequence the contents of digesters are less fluid and hence, the effort for mixing has increased. Applying enzymes seems to be a promising way of improving fluidity. In this study the effects of enzyme application were investigated for a set of materials – grass silage, feed residue, maize silage, and rough-ground rye as feedstock for anaerobic digestion. After enzyme application these materials were mixed with cattle slurry and the probable effect was assessed with three different apparatus – fluidmeter, rotation rheometer, and torquemeter. The instruments proved applicable, in general, whereas grass silage could only be measured with the torquemeter. Fluidity of untreated material increased in the following row: grass silage