Towards the development of a biogas database system in Kenya – a multi-objective study on biogas usage and potency of various agricultural residues in Kenya

Abstract

Kenya being an agricultural based economy produces vast amounts of agricultural bio-waste such as maize/corn stalks, rice and wheat straws, tea and coffee waste, sugarcane, banana and barley residues, sisal and cotton wastes as well as other forest residues. Most of these residues are regarded as of no immediate value hence they are wasted in the farms through burning or uncontrolled decay thus leading to nutrient leakage and eutrophication to the surrounding water bodies as well as contributing to odour and green-house gas emission through release of volatile and un-burnt hydrocarbons. The main objective of the present research was to identify and develop biogas data variables in Kenya through a structured use of anaerobic digestion as a means of producing biogas from agricultural bio-waste including animal manure and crop residues. The short-term target of the research project was a phased development of well defined/structured data variables suitable for a multilayered database system on biogas energy in Kenya, which could later form a basis for the development of a real time biogas information dissemination platform that can be replicated in other regions across Africa. Literature review was done by means of desk study while field surveys were conducted to gather qualitative as well as quantitative data for analysis and uploading onto a Geographic Information System (GIS) based data mapping. Direct interviews were based on a schedule that employed a combination of direct site visits, emails and phone calls. Laboratory-based physical/bio-chemical characterization of biogas feedstock was also conducted. Discussions with diverse biogas stake holders elicited 100% support from respondents in addition to yielding an array of recommendations. The bio‐methane results further demonstrated the suitability of coffee pulp residue, cotton residue and maize stover as complementary biogas feedstock. The biogas quality in terms of hydrogen sulphide (H2S) and methane (CH4) content was quite promising. The biogas H2S content (ppmv) for all the substrates ranged from as low as 105 (for maize stover) to 1100 (sugarcane leaves) whereas the CH4 content varied from 40% (sugar cane leaves) to 62% (cotton residue). Generally CH4 content is required to be above 50% whereas the presence of contaminants such as H2S is supposed to be less than 1000ppmv. From the results, biogas from coffee pulp residue, sugarcane bagasse, maize stover, cotton residue and banana stalks can be recommended as suitable alternatives for domestic biogas production. Keywords: Biogas database, residue potency, energy, Kenya