impact of increasing energy crop addition on process performance and residual methane potential in anaerobic digestion

• Published in: Water science and technology 2007-01, Vol.56 (10), p.55-63
• Main Authors: Lindorfer, H, Perez-Lopez, C, Resch, C, Braun, R, Kirchmayr, R
• Format: Article
• Language: English
• Subjects: Anaerobic digestion; Anaerobic processes; Anaerobic treatment; Anaerobiosis; biodegradation; bioenergy; Biogas; Bioreactors; Capacity; Conservation of Energy Resources; corn; Crop residues; Crops; Crops, Agricultural; Energy; Energy crops; equipment performance; Load distribution; Loading rate; Manure; Methane; Methane - metabolism; methane production; Organic loading; Pig manure; plant byproducts; Refuse as fuel; small grains; solids; Storage; Substrates; Volatile solids; volatilization; waste utilization
• ISSN: 0273-1223; 1996-9732
• DOI: 10.2166/wst.2007.728

In a full-scale agricultural biogas plant, the changes in process performance connected with the increasing energy crop addition were monitored. The substrates applied were pig manure, solid energy crops and agricultural residues. During the study, the organic loading rate and the volume-related biogas productivity were doubled to 4.2 kg VS/(m(.3)d) and 2.83 Nm(3)/(m(3).d) respectively, by means of increasing the energy crop ratio in the feedstock to 96.5% (volatile solids). This resulted in an increase of the electrical capacity on a level twice as high as before. At the same time, methane yield and organic degradation rate decreased slightly to 0.35 Nm(3)/kg VS(added) and 87.4%, respectively. The strongest impact observed was on the transfer of partly degraded organic material into the digestate storage and with this, an increase of the residual methane potential of the digestate. A maximum theoretical methane load in the digestate of 14.4% related to total methane production of the biogas plant was observed. This maximum level could be reduced to 5.5%.