By Aminu Owonikoko
The global warming issue (greenhouse effect) in Nigeria and other parts of Africa and the rest of the world can be mitigated by turning our biomass and other waste materials into wealth. Intensive research has shown that biomass and waste materials are “resources” not “waste” anymore. They are regenerative!
Bioenergy (Biofuels/bioethanol/biodiesel) can be generated from biomass and waste materials. There is a global rush to biomass and waste materials as feedstocks (raw materials) for biofuels production because they are very cheap and readily available. Biomass is all plant and animal matters that has not been fossilised. They are lignocellulosic in nature. That is, they contain lignin, hemicellulose and cellulose. Examples of biomass and waste materials are: sawdust, woodchips, corn stover, municipal solids wastes (MSW), industrial and commercial wastes, animal wastes (like cow dung and chicken/poultry litter), sugar cane, corn, shredded paper, used cooking oil, jatropha, broomcorn, sorghum, straw, wood shavings, algae, cassava, bagasse, e.t.c.
All these resources can be employed to power our vehicles on the road, generate electricity and gas, and produce other biochemicals like fertilizers with readily available and proven technologies. These resources are in abundance in Nigeria and other parts of Africa but they are causing environmental ado to the country (continent) because they are left to be rotten, thus, generating biogas (methane and carbon dioxide) which are dangerous to the environment but they can be used for other useful purposes with readily available and proven technologies.
Our total dependency on fossil fuels (petroleum: oil and gas) is also causing economic problems to the nation. Research has shown that fossil fuels will dry (run) out one day. The need to generate energy from renewable/sustainable sources is very pertinent to our dear country and continent. Other countries like United Kingdom, United States of America, Australia, Sweden, Finland, Netherlands, India, Brazil, Switzerland and other European countries have imbibed in this by generating their energy from sustainable/renewable sources.
The process (conversion) technologies that can add value to our biomass and waste materials are not exorbitant. They are gasification, pyrolysis, trans-esterification, combustion, anaerobic digestion, fermentation and hydrolysis.
Pyrolysis is the process of heating biomass (mostly carbon-based wastes) at a high temperature in an environment with no oxygen. The restriction of air available during the chemical conversion process is to a greater degree than for gasification. Pyrolysis is the starting process for both combustion and gasification if sufficient oxygen or other oxidizing agents are present. In this process, biomass is broken down to achieve the following products: char (which can be activated to produce activated carbon), combustible gas, and liquid oil.
Gasification process is employed to convert a heterogeneous biomass feedstock to a consistent intermediate product consensually called producer gas. Biomass gasification yields a combustible gas that can be employed to generate heat, liquid fuels and electricity. Carbon monoxide, methane and hydrogen are the main combustible components of producer gas. In addition to these gases, gasification produces char, carbon dioxide, water vapour, and ash. The producer gas also contains nitrogen and small amount of oxygen (1-2%).
Transesterification: this is a chemical process that is employed to produce biodiesel (an ester) made from oils (e.g. used cooking oil) or fats. In this process, a catalyst causes the exchange of the alkoxyl group of an ester by another alcohol.
Anaerobic digestion: is the bacterial decomposition of the volatile solids to biogas (methane and carbon dioxide). Food processing, municipal solid and animal wastes can be used as feedstocks (raw materials) for anaerobic digesters.
Combustion is the complete oxidation of carbon to carbon dioxide with production of heat. The heat must be used immediately. In order to generate steam for electricity from biomass, biomass/waste materials can be combusted directly or it can be converted into gas to power a turbine. Combustion could be done on domestic heating, district heating, combined heat and power (CHP) and large-scale combustion.
Hydrolysis involves extracting simple carbohydrates from complex carbohydrates found in cellulose and hemicellulose. Extracting the carbohydrates may involve steam explosion of the cell wall, or dissolving the organic constituents with acids, enzymes, or organic solvents. Sugars resulting from hydrolysis can then be converted into ethanol through fermentation.
Fermentation: production of bioethanol through fermentation can be achieved in at least 3 ways:
(1) Directly using naturally available sugars, such as broomcorn, sugarcane, sorghum
(2) Indirectly using carbohydrate or starch sources, such as cassava
(3) In combination with acid hydrolysis or enzymatic hydrolysis of cellulose sources such as wood residues (like woodchips, saw dust and wood shavings) which produce sugars that can be fermented into biofuels (bioethanol).
All the succinct aforementioned conversion technologies can be employed in Nigeria and other parts of developing countries in Africa to add value to our biomass and waste without unnecessary costs, thus, it will mitigate the global warming issues and create more jobs to the nation and the continent. Further information is summarised schematically in the figure 1 below particularly for sugarcane which is tolerant and adaptable to other biomass materials with little retrofit (i.e. modification).
Aminu Owonikoko MPhil (UK), MSc (UK), B.Tech (Nigeria) Email: email@example.com Mobile number: +1 785 914 8240