Design of a Co-Digestion biogas plant for households: A study case of Rwanda, Gicumbi District.

Abstract

Energy is a backbone for economic development globally as well as in Rwanda. Low access to the reliable energy resources for Rwandans is a crucial challenge that needs more efforts to be resolved. Households in Rwanda are the major consumers of the energy with 91% of primary energy consumption and 51% of electricity consumption, whereby 99 % of the energy consumed in households come from biomass. Several researches, for alternatives and modern energy use for environmental sustainability, have been done. Among them biogas technology, which was introduced in the current energy mix of Rwanda with the target of providing clean and environmental friendly energy alternatives for Rwandans. At first, NDBP was developed by the Government, in collaboration with SNV, with the intention of deploying biogas digesters around the country for household as well as institutional levels. Among the challenges encountered by this program were high upfront cost to initiate a biogas digester deployment and low access to the feedstock resources mainly. This program was required to have at least two heads cattle per house in order to launch a biogas plant. In this regards this thesis work was intended at designing a co-digestion biogas plant that would use human faeces along with caw dung to generate biogas for households in Rwanda. This work is one of the solutions for feedstock materials, and biogas plant. In study a centralized digester plant for 5 households was looked at in order facilitate the financial affordability of the plant. The specific home activities considered during the design of biogas plant in the study were direct cooking and heating water through biogas stove. This study was carried out in Gicumbi District, Northern Province of Rwanda as the pilot study. A biogas plant of 30.82 m3 volume of size, with 25.6m3 of digester volume and 5.22 m3 volume of gas holder is required in order to provide 2.9 m3 of biogas per day, that is equivalent to the daily energy needs per each of 5 households. The use of this co-digestion biogas plant would save 2.1tones of charcoal for 5 households annually. This could help to preserve the environment through reduced forest cutting. The financial analysis found that a (Bricks/concretes) biogas plant, in the study, needs RWF 4,000,000 or USD 4444 as initial investment, with annual income of RWF1,221,300 or USD1188 in terms of saving from buying charcoal and due to the selling of bio-slurry as fertilizers