Use of biogas as alternative fuel for tobacco curing: Case for Zimbabwe

This research study investigated tobacco curing activities in the country. Historically tobacco related activities were responsible for over 15% of annual deforestation in Zimbabwe, due to the energy intensive tobacco curing process by the majority of small scale farmers who use firewood as they find coal expensive to procure. This practice is not sustainable hence need to consider the feasibility of biogas as an alternative fuel for tobacco curing. The study was undertaken on a sample of small scale tobacco farmers, and the feed stock was mainly from dung from cattle, goats and chicken droppings. A technical evaluation was done for an average farmer, and came up with a 12m³ fixed dome biogas digester to produce 2.6 m³ of biogas on daily basis. A bulk tobacco curing barn of dimensions 3m x 4m x 8m was selected, and was calculated to require 1475,8 m³ of gas produced by the biomass digester which would generate up to 949m3 per annum. This was found to save up to 65% in energy requirements for the average farmer during curing. A general “feasibility calculator“ for individual farmers was generated which other functions could be used to check individual farm biogas potential and compare it with required biogas for curing a specific amount of tobacco and give costing results for implementation if the farmer intended to consider biogas tobacco curing.