Anaerobic digestion of animal waste: effect of mixing.
Six laboratory scale biogas mixed anaerobic digesters were operated to study the effect of biogas recycling rates and draft tube height on their performance. The digesters produced methane at 0.40-0.45 L per liter of digester volume per day. A higher methane production rate was observed in unmixed digesters, while increased biogas circulation rate reduced methane production. However, different draft tube heights caused no difference in the methane production rate. Air infiltration (up to 15% oxygen in the biogas) was observed in the digesters mixed by biogas recirculation. Slight air permeability of tubing or leakage on the vacuum side of the air pump may have caused the observed air infiltration. The similar performance of the mixed and unmixed digesters might be the result of the low solids concentration (50 g dry solids per liter of slurry) in the fed animal slurry, which could be sufficiently mixed by the naturally produced biogas.
Chemical Reaction Engineering Laboratory (CREL), Department of Chemical Engineering, Washington University, 1 Brookings Drive, Campus Box 1198, St Louis, MO 63130 4899, USA.
Khursheed
K
Karim
K
K
Thomas Klasson
Rebecca
R
Hoffmann
Sadie R
SR
Drescher
David W
DW
Depaoli
M H
MH
Al-Dahhan
D000704:Analysis of Variance; D001421:Bacteria, Anaerobic / Q000378:metabolism*; D001674:Bioelectric Energy Sources; D019149:Bioreactors; D008372:Manure / Q000382:microbiology*; D008697:Methane / Q000378:metabolism*; D014865:Waste Disposal, Fluid / Q000295:instrumentation / Q000379:methods*
D008372:Manure; D008697:Methane