A new design tool for solid-state anaerobic digestion
Un nouvel outil de dimensionnement pour la digestion anaérobie par voie solide
Résumé
Batch mode solid state anaerobic digestion (SS-AD), with leachate recirculation, is the most adapted technology to treat solid agricultural with high solid content. Methane production kinetics of these substrates, through batch mode SS-AD, is an important factor to develop such a process at farm scale. However, only little information was found about laboratory scale reactor studying SS-AD. Then, six small scale reactors (8 liters) were developed to measure real-time methane production rate (MPR) on cattle manure, wheat straw, hay and mixture thereof. Reactors are divided in two parts: one to load the substrate, and the other, under the first, to load the leachate. A recirculation loop enables watering the substrate’s top with the leachate, which flows through the waste mass and goes back to the leachate tank. The biogas production is recorded continuously and methane content is measured once every day. Kinetics pattern for beef and dairy cattle manure, and a mixture of it, present a similar MPR with two production peaks close to 15.5 NLCH4/gVS/d. Wheat straw chart shows a similar MPR with delayed and less intense peaks of methane (about 12 NLCH4/gVS/d). Cattle manure/wheat straw/hay mixture is a “hybrid” form with a first intense peak (15.5 NLCH4/gVS/d, equivalent to manure kinetic) and a low delayed second peak (8.7 NLCH4/gVS/d, equivalent to wheat straw kinetic). With that kinetics it is possible to simulate a farm scale MPR which will help designing SS-AD plants.