Effective microorganisms on organic matter with carbon and nitrogen mineralisation for empty fruit bunches composting

Abstract

This project aims to investigate the effect of Effective Microorganisms (EM) on the composting of oil palm empty fruit bunch (EFB) through organic matter degradation with carbon (C) and nitrogen (N) mineralisation by comparing the control sample (CTL) of EFB with no EM treatment and the EM-treated EFB sample (ETC). The maximum C mineralisation for CTL and ETC was recorded as 671.4 ± 86.55 mg CO2 Ckg-1d-1 on day one and 713.5 ± 68.5mg CO2 Ckg-1d-1 on day two respectively. ETC had C mineralisation remained significantly higher than CTL from day 28 until day 40 before falling on day 41 and became on par with CTL. The total organic matter loss was 3.75 ± 1.35% for CTL and 10.78 ± 3.77% for ETC. This resulted in a total mineralised C of 32.97 ± 2.25% and 37.7 ± 2.53% total organic carbon for CTL and ETC, respectively. For N mineralisation, the presence of NH4 + in early stage followed by NO3 - dominance on later stage indicated successful composting. CTL had final value of 0.1 and ETC had 0.04 for NH4 +/NO3 - ratio. For curve fitting, first order kinetic model and first order exponential model were chosen as they were showed to better describe mineralization for recalcitrant organic matter by other studies. The first order exponential model showed better fit with p-value of 0.275 as compared to the first order model with p-value of 0.981 in this work. First order kineitc model failed to describe the N mineralisation with a high p-value of 0.989. The unfitness of models could be due to insufficient data over limited experimental time and sampling error for heterogenous materials. This study showed that both CTL and ETC were able to produce mature compost but ETC had better performance on the efficiency of EFB composting based on organic matter degradation, C and N mineralisation coupled with several others parameters (C/N, temperature, pH and microbial profile).