Biomethane Production From Residual Algae Biomass (Ecklonia maxima): Efects of Inoculum Acclimatization on Yield

Abstract

This paper presents the effects of inoculum acclimatization on biomethane production from extraction residues of the seaweed (Ecklonia maxima) via anaerobic digestion. Anaerobic digestion of Ecklonia maxima has been studied with and without acclimatized inoculum under mesophilic conditions (~37 °C) for a digestion period of twenty (20) days. The acclimatized inoculum-seaweed sample recorded the highest methane yield of~ 862 ml CH4/gVS (~ 55% of the total biogas produced) compared to the~580 ml CH4/gVS recorded for the non-acclimatized inoculum- seaweed sample, both within the first ten (10) days. Kinetic studies on acclimatized and non-acclimatized samples were carried out using the modifed Gompertz model. The model showed coefcients of determination (R2 ) of 0.99 and 0.98 with an estimated yield rate (µ) of~296 ml/ gVS/day (0.4 days phase lag, λ) and~60 ml/gVS/day (3.4 λ) for the acclimatized and non-acclimatized samples respectively. The Fourier transform infrared spectroscopy (FTIR) analyses revealed the presence of carboxylic, hydroxyl, ketone and ether groups which further corroborated the suitability of E. maxima for biogas production. The implications of the results are discussed to elucidate the potential of seaweed as a renewable energy source for macroalgae biorefnery.