Talk to any dairy or pig farmer on the challenges they face and you will not miss feed and waste management; while their neighbours will complain of the waste odour.
Such farmers only need to integrate biogas production into their farming system and the odour and waste management problems will be buried.
Biogas has recently become attractive to many households due to increasing global demand for energy amid rising fossil fuel prices and concerted campaign for a reduction in greenhouse gas emissions.
The use of biogas has the effect of expanding farm income by utilising traditionally discarded animal waste and saving on fuel costs.
Loop farming
Biogas is a renewable energy produced from sewage waste, poultry droppings, dung from cows and pigs or any other organic waste on your farm. Biogas is called renewable energy because it can only be depleted when we stop producing waste! In a closed loop farming system where all waste is recycled this can continue forever. The potential of biogas is normally summarised using a three-legged chair analogue of energy, agriculture and environment.
The energy comes in the form of heat and electricity, the digestion of the waste makes it good manure for increased agricultural production and subsequently reducing raw waste run off into water bodies and thus conserving the environment. Pig waste for example is full of pathogens and ammonia which can be detrimental to crops and the environmental in its raw form but not when it has gone through a biogas digester.
Biogas is produced through a natural biological process called anaerobic digestion where bacteria convert organic materials into biogas in absence of oxygen. Biogas is mainly composed of methane and carbon dioxide. Methane accounts for 55 per cent to 65 per cent depending on the type of organic waste used.
Methane is a greenhouse gas; therefore its capture and utilisation translates into less greenhouse emission, good fertiliser and a form of saving to the farmer. When biogas reacts with oxygen, the product is clean energy as the reaction utilises methane and carbon and prevents them from accumulating in the atmosphere where they cause global warming. In the developed world, biogas is an industrial energy and is compressed and used to fuel cars.
Overflow tank
The biogas production technology is relatively simple and will typically have three sections namely the reception tank, digester where the fermentation takes place, the gas holder and an overflow tank.
The materials are locally available and the plant is relatively easy to set up. The plant can either be continuous where it is charged and discharged daily or batch type that is filled at once and only emptied after the material has been completely digested.
The simplicity of the technology is further exemplified by the fact that a single cow can produce enough waste that can be digested to supply enough biogas for a household’s cooking and lighting needs.
However, biogas should be handled carefully as the other gases in the mixture can be dangerous and can result in explosions, poisoning and diseases. Protective clothing and adequate ventilations for workers at the point of production and use is advised. When doing maintenance on the plant avoid confined spaces and pits.
Animal manure contains bacteria, fungi, viruses and parasites which can easily infect man. Carbon dioxide and hydrogen sulfide are poisonous gases which can cause death in human beings.
The writer teaches Agricultural Information and Communication Management at the University of Nairobi.
