Effect of inoculum size on production of compost and enzymes from palm oil mill biogas sludge mixed with shredded palm empty fruit bunches and decanter cake

Abstract

The effect of inoculum size on production of compost and enzymes from palm oil mill biogas sludge (POMS) mixed with shredded palm empty fruit bunches (PEFB) and decanter cake (DC) was studied using the mixed culture LDD1 as an inoculum. Three piles of 50 kg mixture (POMS:PEFB:DC = 2:1:1) with different inoculum sizes of 0.0075% (treatment A), 0.015% (treatment B), and 0.030% (treatment C) were set up. The physicochemical parameters were measured during the composting. All the compost appeared dark brown in color, crumbly, attained an ambient temperature and had the C/N ratio of 11:1 after 40 days fermentation, indicating the maturity of the compost. The optimal inoculum size was found to be 0.030% (w/w). For enzyme production, the highest carboxymethylcellulase (CMCase) activity was 3.23 Unit/g substrates at 12 days incubation whereas the highest xylanase activity was 3.11 Unit/g substrates at 6 days incubation. At the end of 60 days fermentation, the compost (treatment C) had a TN-P2O5 -K2O of 3.10-1.29-2.01% (dry basis). Therefore, the compost quality complied with the national compost standard set by the Ministry of Agriculture, Thailand.

Keywords

• palm oil mill biogas sludge
• composting
• palm oil mill wastes
• empty fruit bunch