Biomass as a source of energy

PHOTO: SG Preston

Biomass can be defined as organic matter generated from a living thing or a previously living thing. This biomass which can be generated from homes, agricultural farms, forests, industries, etc are sometimes classified as waste material and then disposed. Sadly, they are disposed in a manner that constitutes public health and environmental nuisance to mankind. The fact that there is need to reduce the amount of waste being generated is no longer new. What is relevant now is how to convert this waste into valuable uses like generation of energy. This will not only generate energy but will reduce the quantity of waste that requires final disposal.

Agricultural residues provide a good source of biomass for energy generation. Nigerian farmers produce large quantities of crop residues which in most cases are not put to maximum utility. Rice husk, sugar cane fibre, coconut husk, coconut shells are common agricultural residues that will readily serve as sources for biomass energy. The business as usual practice by Nigerian farmers is to burn these residues, allow farm animals to graze them or plough them back into the soil. However, some portions of these residues can be set aside and processed into liquid fuels which will be used to provide heat and electricity. Animal wastes are also a good source of biomass energy. Animal and poultry manures are easily available sources of biomass for energy generation. The business as usual practice by farmers is to spread these residues on the farms to serve as fertilizers. The challenge with this is that it causes environmental damage in form of harmful odour and contamination of water bodies when rainfall and run-offs directs the waste from the farms into water bodies. Waste from food processing and abattoirs are also animal wastes that are good sources for biomass energy generation.

Another readily available source for biomass energy generation is municipal solid waste. This includes decayable and non-decayable wastes that are usually dumped into sanitary landfills. The municipal solid waste can be converted into energy by direct combustion or natural anaerobic digestion.

Another source of biomass for energy generation is forestry residues. This includes residues generated during cutting of branches in plantations, clearing of roads for logging activities, cutting stem-wood for timber, wood processing into saw dust and wood chips. These residues which are usually left on the sites to rotten can be collected and used to provide energy. Industrial wastes are also a good source for biomass energy generation. These include residues and by-products from the food industry ranging from industrial meat production to confectionery production. It also includes foods like fruits, vegetables, pulps, starch, sugars, coffee that do not meet regulatory standards and consequently disposed off. Industrial wastes also include liquid waste generated during washing of meat, fruits and vegetables as well as pre-cooking of meat, poultry, fish. Liquids generated during wine making and cleaning activities are not left out. All these are industrial wastes which can be used to provide energy.

There are different pathways through which biomass can be converted to energy. One such pathway is thermochemical conversion. Thermochemical conversion can only be used to create energy when heat recovery is involved. Heat recovered from the combustion of biomass is then used to power turbines for electricity generation or for direct water heating. Another pathway for converting biomass into energy is biochemical conversion. It is used when the biomass has a high percentage of organic biodegradable matter and high moisture content. This involves composting the biomass in a controlled and oxygen-deficient condition which results in the production of a biogas that can be used to provide electricity and heat. The third pathway for generation of energy from biomass is physico-chemical conversion. This involves processes that improve the physical and chemical characteristics of the biomass into high energy fuel pellets that are friendly to the ecosystem.

Waste to energy reduces green house gas emission and is therefore a very efficient means of addressing the challenge of climate change. This is because it reduces the dependence on fossil fuel energy. It provides an alternative source of energy that is better than fossil fuel in terms of damage to the environment.

• Eke can be reached at martinseke@rocketmail.com

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