Growth models and biomethanation of marine microalgal biomass
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Date
2017
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Publisher
Universiti Teknologi Malaysia
Abstract
Innovative schemes driven towards renewable energy generation are vital to resolve the turmoil caused by depleting trends in fossil reserves where microalgal biomethanation have drawn significant interests. This integrated system is centred on the subject of sustainability, highlighting key factors that influence the performance stability and its biomass requirements to drive anaerobic digestion for methane generation. The experimental photobioreactor system used for Nanochloropsis oculata (N. oculata) cultivation was modelled based on a set of designated features to yield three defined kinetic expressions - eMK, eHK and eDK that were simulated in time to produce the trajectories extended with additional state variables. While preserving the digester’s stability and avoiding alkalinity additions, the microbial consortia embedded within the anaerobic palm oil mill sludge served as the sole digesting inoculum for the pseudoplastic biomass. Stable digestion with methane productivity of 0.24 L.CH4 .g-1.VS was measured for digesters exclusively fed with N. oculata biomass at an organic loading rate of 4 kg.COD.m-3.d-1. The co-digestion processes exerted synergetic effects on the stability of the anaerobic digester with a methane productivity of 0.12 L.CH4 .g-1.VS at 50% feed composition of palm oil mill substrate and 50% N. oculata biomass. Metagenomic analyses of the digesting sludge suggests that these methanogens are a phylogenetically diverse guild of prokaryotes from the orders Methanobacteriales, Methanomicrobiales and Methanosarcinales. The data obtained suggests that methanogenic strains of the genus Methanosaeta such as the aceticlastic NaCl-requiring methanogens - Methanosaeta concilii and Methanosaeta harundinacea; the hydrogenotrophic methanogens - Methanobacterium kanagiense, Methanospirillum hungatei, Methanobacterium formicicum and Methanoculleus palmolei were the predominant metabolic drivers for the methanogenesis of N. oculata biomass. The coupled system processes for microalgal biomethanation employing strategic process controls, plays essential roles in the recycling of carbon within the biosphere, and features its feasibility for future microalgal-based biorefineries in temperate and tropical regions
Description
Thesis (Ph.D (Biosciences))
Keywords
Marine microbiology, Biomass energy