Effect of inoculum type and organic loading on biogas production of sunflower meal and wheat straw

Inoculum plays a vital role in providing initial microbial population in anaerobic process. There is unavailability of standard inoculum in the Pakistan and the available inoculum requires pretreatment and preparation before use. Thus, in this study the effect of inoculum type and organic loading (OL) on the biogas yield of sunflower meal and wheat straw was evaluated. For this purpose, lab scale batch experiments were conducted at OL of 2 g VS L-1 in 225 mL glass bottle using digested manure, acclimatized sludge and septic tank sludge as inoculum. The highest biogas yield and volatile solids reduction of 768 NmL g(-1) VS and 78%, respectively, were observed from sunflower meal with digested manure. Reactor inoculated with digested manure also showed better buffering capacity in terms of pH. The inoculum selected from first experiment was used to study the effect of OL (2, 6, 10 and 14 g VS L-1) on biogas yield. Results showed that biogas yield decreased with the increased in OL. Stability parameters revealed that reactors can be operated safely up to OL of 10 g VS L-1. Biogas production data were modelled by modified Gompertz function.