Optimum Bio-digester Design and Operations

Abstract

Biogas is competitive, viable and generally sustainable energy resource due to abundant supply of cheap feedstock and availability of a wide range of biogas applications in heating, power generation, fuel, and raw material for further processing and production of sustainable chemicals including hydrogen and carbon dioxide and biofuels. The capacity of biogas power has been growing rapidly for the past decade with global biogas generation capacity increasing from 65 GW in 2010 to 120 GW in 2019 representing a 90% growth. The study showed that digester design, operation and maintenance is a very important aspect of biogas energy and technology development. It was established that there are three basic digester designs i.e. fixed dome, floating dome and fixed dome with expansion chamber. The main challenges facing digesters is silting, poor serviceability and limited mixing ability. Design improvements suggested are manual and motorised mixing and provision of access manhole to facilitate maintenance and service without stopping the entire process.

Biomethane Production and Applications

“…The Fischer-Tropsch synthesis (FT-synthesis) polymerizes the carbon and hydrogen atoms in syngas or biomethane to create long chain molecules. The process is run over iron or cobalt catalyst at 20-30 bars [14] in an overall exothermic process leading to polymerization of CH 2 to hydrocarbons with long chains called syncrude. The various reactions in Fischer-Tropsch process are summarized below;…”

“…Biogas is a renewable energy carrier that can be exploited directly as a fuel or as a feedstock for production of hydrogen or synthesis gas. The main constituents of biogas are carbon dioxide (CO 2 ) and Methane (CH4), but there are quantities contaminants like such as hydrogen sulfide (H 2 S), ammonia (NH 3 ), moisture and siloxanes whose existence and composition is a function of the source of biogas like landfills, anaerobic fermentation of manure [14,15]. The contaminants have the following undesirable effects to biogas applications a fuel; i.…”