Utilising biomass waste as a fuel for diesel generators

The purpose of this study was to research ways whereby biomass waste could be used as a fuel for diesel generators in developing countries for small-scale renewable electricity generation. In particular, by adapting diesel generators to run as gas-diesel dual fuel engines. Biomass waste/residues can be used to produce a gaseous fuel using gasification (syngas) and/or anaerobic digestion (biogas) which can be used to substitute diesel in dual fuel combustion. Tanzania and Uganda were selected as the focus of this study due to their low electrification rates.
This thesis investigated the energy potential of four biomass residue streams (from agriculture, forestry, livestock, and urban human waste) in Tanzania and Uganda. From this, the net electricity generation potential was calculated based on overall efficiencies of 10 and 25% (from biomass to net electricity) for the base year of 2019. This work found that both countries have a plentiful supply of biomass residues; the calculated net electricity generation potential from these combined residues was found to exceed the electrical energy generated nationally for both countries.
This thesis also researched the impact of dual fuel combustion using syngas and biogas. When compared with diesel combustion, the advantages were the lower emissions of nitrogen oxides (NOx), particulate matter mass, and particle number, alongside reduced diesel consumption. The disadvantages were a reduction in the brake thermal efficiency (BTE), and an increase in the total hydrocarbons (THCs), carbon monoxide (CO), methane (CH4), and formaldehyde emissions. Higher THC and CO emissions can be mitigated by utilisation of a diesel oxidation catalyst (DOC).
Increasing the hydrogen content of the simulated syngas led to an improvement in the BTE and reductions in the CO, THC, CH4, and formaldehyde emissions; in contrast, NOx emissions increased when compared to the syngas blends with lower hydrogen content.