Bioavailability of Nutrients for Improved Methane gas Production by Addition of Chelating Ligands

Abstract

Our irreplaceable fossil fuels are fast diminishing. Therefore, an important precautionary measure will be to develop renewable energy sources. Biogas is renewable and an environmentally friendly alternative energy. This research work focused on addition of chelating ligands in order to improve methane gas yield, and decrease concentration of Volatile Fatty Acid produced within digester systems. The experimental analysis carried out involved the use of Flame Atomic Absorption Spectrophotometer , Biogas5000 analyser and other classical analytical tools. The concentration of trace metals presents namely Iron, Cobalt, and Nickel ranged from 0.001-0.050 mg/L. On addition of chelating ligands, Ethylene diamine-N,N-diacetic acid, Nitrilotri-acetic acid and Diethylenetriamine-pentaacetic acid, an increase in the Methane yield was recorded which ranged from 2-15%. The Volatile Fatty Acid concentration was generally low with values for Ethylene diamine-N,N- diacetic acid, Nitrilotri-acetic acid and Diethylenetriamine-pentaacetic acid given as 476.05 mg/L, 671.96 mg/L, and 737.63 mg/L respectively; with pH ranging from 6-7.5. The improvement in methane gas yield was due to the increased bioavailability of essential nutrients on addition of chelating ligands which invariably promoted the growth and stability of the methane producing bacteria thereby, improving methane production. The Volatile Fatty Acid values which were generally lower than 2000 mg/L are implicated in the high methane gas yield observed.