Prediction of Biochemical Methane Potential of Palm Oil Mill Effluent

ABSTRACT

Exploring green energy options constitute a contemporary tenet in designing a sustainable future. This study investigated the independent variables (milling scales, types of fresh fruit bunches and seasons) that define the dynamics of biochemical methane potential (BMP) or bio-methane and organic content in palm oil mill effluent (POME) generated in ADAPALM (large-scale mill) and palm oil mills in its surrounding communities, located in Ohaji/Egbema LGA, Imo State, Nigeria. The eight communities that constitute ADAPALM were categorised into three strata in relation to the number of small-scale mills in each community (1-5mills, 6-10mills, 11-15mills). Besides the lone large and medium-scale mills, a small-scale mill was randomly sampled from a community in each stratum. Four homogenous samples of POME were collected from each mill for laboratory analysis of biochemical oxygen demand (BOD), chemical oxygen demand (COD), total organic carbon (TOC) and total carbon (TC) using standard methods for wastewater analysis. Prediction of BMP for each sample of POME composition and fraction of substrate used for cell synthesis (fs) wherein POME is classified was computed using biogas package. Data was analysed using tools of SPSS. Multiple linear regression reveals that there is a significant relationship between the predicted volume of BMP with milling scales and seasons (p<0.01), R²=0.927. Similarly, multivariate analysis of variance (MANOVA) shows that the organic content of POME is significantly related to milling scales and seasons (p<0.01). At fs=8% in methanogenic condition, BMP is 22.800±0.282LCH₄/m³POME and 75.532±0.149LCH4/m3POME in the wet and dry seasons respectively. These respectively correspond to methane production capacity of 0.057±0.005KgCH₄/KgCOD and 0.014±0.001KgCH₄/KgCOD. The variance explained by the dependent variable (R²) indicates the importance of these independent variables in determining the BMP and organic content of POME in the area. The predicted dynamics of BMP and their associated wastewater composition provide useful tools in regulating the wastewater content and evaluating its feasibility for bio-energy development.

Keywords: Dynamics, Bio-methane, Prediction, POME, ADAPALM, Biogas package