The Effects of Inoculum Acclimatisation on the Methanogenesis of Ecklonia Maxima

Abstract

In the present scenario of the over dependence and shortcomings of fossil fuels, integrated biorefinery techniques have been developed to process biodegradable and sustainable feedstock for use as green energy. Brown seaweed biomass, recently has been under the spotlight for the production of biogas via anaerobic digestion. In this study, the effects of acclimatising inoculum to Ecklonia maxima, a brown seaweed type for the production of biogas have been investigated. Biomass of Ecklonia maxima were subjected to an acclimatisation period to enable anaerobic microbes cultured on the inoculum adapt to the feedstock. Mixtures of Ecklonia maxima with either acclimatised or unacclimatised inoculum were prepared and anaerobically digested for a period of 20 days. The proximate and ultimate results carried on the feedstock confirmed them suitable for the purpose. The carbon, hydrogen, nitrogen and sulphur (CHNS) content analysis result was used to calculate the theoretical yield potential which was 1844.0 ml/gVS for Ecklonia maxima. SEM - EDX were conducted on the samples to observe their morphology and chemical compositions. Fourier transform infrared (FTIR) spectroscopy was further conducted to identify the bonds and functional groups where both spectra recorded the presence of carboxylic, hydroxyl, ketones and ethers groups. Samples of biogas produced were analysed using gas chromatography to characterise the percentage of carbon dioxide (CO2) and methane (CH4). An optimum amount of ~55% methane was recorded by the mixture of Ecklonia maxima and acclimatised inoculum. The cumulative biogas yield for acclimatised sample was recorded as 1571.8 ml/gVS, very similar to 1564.0 ml/gVS predicted as the biogas potential (A) at a production rate (μ) of 296.2 ml/day using the modified Gompertz equation. The volume of biogas generated from the feedstock implies a positive influence of acclimatising inoculum on E. maxima