Anaerobic co-digestion of poultry droppings and briquetted wheat straw at mesophilic and thermophilic conditions: Influence of alkali pretreatment

Anaerobic co-digestion of poultry droppings (PD) and briquetted wheat straw (BWS) with alkali additive in the form of KOH (BWSadd) or without any additive (BWSraw) was conducted using continuously stirred tank reactors (CSTRs) under both mesophilic (35 degrees C) and thermophilic (53 degrees C) conditions. The aims of the study were to compare 1) co-digestion of PD and BWS versus mono-digestion of PD; 2) co-digestion of PD and BWS with or without additives; and 3) mesophilic and thermophilic anaerobic digestion (AD). Co-digestion of PD and BWS was superior to mono-digestion of PD in terms of gas production. Co-digestion of PD with BWSadd at thermophilic temperatures resulted in a higher methane volumetric yield per kg substrate compared to mesophilic conditions. With and without additive, co-digestion with BWS produced 8% and 11% higher yields at thermophilic conditions than at mesophilic conditions. Co-digestion of PD with BWSadd resulted in, respectively, 14% and 27% more methane produced at mesophilic and thermophilic conditions over mono-digestion of PD. When mono-digesting PD, the mesophilic temperature was superior to the thermophilic since methane yield was higher in the mesophilic temperature regime. (C) 2018 Elsevier Ltd. All rights reserved.