"Optimizing small-scale biogas technology for household energy and improvement of soil fertility within coffee-dairy production systems in Kiambu and Machakos Counties"
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Date
2023-09
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Abstract
Coffee farmers are major users of energy both for household heating and cooking as well as on-farm activities. In rural households, the primary source of energy remains firewood and charcoal with intermittent usage of kerosene and electricity. Coffee farmers also have soil fertility needs towards higher yields and profitable production not only for coffee but also for other associated crops (e.g., maize and beans). Over-reliance on charcoal and firewood is considered a risk and a prime factor contributing to deforestation and by extension climate change challenges. The repercussions would include lower precipitation, and declining soil fertility leading to low coffee yields and associated crops. Notably, poor management of inorganic and organic fertilizers (bio-slurry) from biogas has contributed to their soil being highly acidic leading to low coffee, maize, and beans yields. This has higher contributions to the loss of productive lands for coffee production and associated crops. Solutions towards mitigating these effects should address energy, integrated soil fertility management options, and scale-up these technologies to the affected coffee farmers. Technologies for alternative energy have been widely established, however, innovations that suit the needs of small-holder farmers are rare, since most of the options require heavy investment in material and labor. Recent innovations have focused on reducing the material cost of installation of alternative energy units as well as providing a source of organic fertilizer (bio-slurry) through the development of small-scale biogas installations. This project aimed to determine the efficiency of simple small-scale biogas technologies in the provision of rural energy and organic fertilizer within coffee and associated crops mixed farming communities. The project also sought to establish indices of having these technologies demonstrated and scaled up in feature in a Payment for Environmental Services (PES) market. A multi-disciplinary approach was employed in the implementation of the research project that entailed a survey of smallholder coffee farmers in Kiambu and Machakos to articulate energy and agronomic needs, installation of small-scale alternative energy units, testing the quality of gases as well as testing quality of bio-slurry from biogas digesters fed with different locally available substrates. Biodigester attributes were studied and evaluated for willingness to pay by farmers and indicated the relative importance of each attribute with reliability and biogas output being ranked the highest by farmers. The bio-digester technologies deployed were tubular and fixed dome, in which a challenge of Venting-loss of biogas through the overflow chamber- was observed. Bio-slurry testing on-farm indicated the potency of bio-slurry as a potent fertilizer for crop production. An opportunity for standardizing bio-slurry as a marketable product exists.