1.0 Introduction
1.1 Background of the study
Biomass, particularly agricultural residues seem to be one of the most promising energy resources for developing countries (Patomsok, 2008). Rural households and minority of urban dwellers depend solely on fuel woods (charcoal, firewood and sawdust) as their primary sources of energy for the past decades (Onuegbu, 2010). Of all the available energy resources in Nigeria, coal and coal derivatives such as smokeless coal briquettes, bio-coal briquettes, and biomass briquettes have been shown to have the highest potential for use as suitable alternative to coal/ fuel wood in industrial boiler and brick kiln for thermal application and domestic purposes. Global warming has become an international concern. Global warming is caused by green house gasses which carbon dioxide is among the major contributors. It was shown that increased emissions of CO2 have been drastically reduced owing to the fact that the rate of deforestation is higher than the afforestation effort in the country.
The use of fuel wood for cooking has health implications especially on women and children who are disproportionately exposed to the smoke apart from environmental effects. Women in rural areas frequently with young children carried on their back or staying around them, spend one to six hours each day cooking with fuel wood. In some areas, the exposure is even higher especially when the cooking is done in an unventilated place or where fuel wood is used for heating of rooms. Generally, biomass smoke contains a large number of pollutants which at varying concentrations pose substantial risk to human health. Among hundreds of the pollutants and irritants are particulate matters, 1, 2-butadiene and benzene (Schirnding and Bruce, 2002).
Studies showed that indoor air pollution levels from combustion of bio fuels in Africa are extremely high, and it is often many times above the standard set by US Environment Protection Agency (US-EPA) for ambient level of these pollutants (USEPA, 1997). Exposure to biomass smoke increases the risk of range of common diseases both in children and in adult. The smoke causes acute lower respiratory infection (ALRI) particularly pneumonia in children (Smith and Samet, 2000; Ezzati and Kammen, 2001).
Agro waste is the most promising energy resource for developing countries like ours. The decreasing availability of fuel woods has necessitated that efforts be made towards efficient utilization of agricultural wastes. These wastes have acquired considerably importance as fuels for many purposes, for instance, domestic cooking and industrial heating. Some of these agricultural wastes for example, coconut shell, wood pulp and wood waste can be utilized directly as fuels.
Fortunately, researches have shown that a cleaner, affordable fuel source which is a substitute to fuel wood can be produced by blending biomass (agricultural residues and wastes) with coal. Nigeria has large coal deposit which has remained untapped since 1950’s, following the discovery of petroleum in the country. Also, millions of tones of agricultural wastes are generated in Nigeria annually. But it is unfortunate that farmers still practice “slash-and-burn” agriculture.
These agricultural wastes they encounter during clearing of land for farming or during processing of agricultural produce are usually burnt off. By this practice, not only that the useful raw materials are wasted, it further pollutes the environment and reduces soil fertility.
On the other hand, the majority of the huge materials are not suitable to be used directly as fuel without undergoing some processes. This is probably as a result of inappropriate density and high moisture contents and these factors may cause problems in transportation, handling and storage. Most of these wastes are left to decompose or when they are burnt, there would be environmental pollution and degradation (Jekayinfa, and Omisakin, 2005).
Researchers have shown that lots of potential energies are abounding in these residues (Fapetu, 2000). Hence, there is a need to convert these wastes into forms that can alleviate the problems they pose when use directly. An assessment of the potential availability of selected residues from maize, cassava, millet, plantain, groundnuts, sorghum, oil palm, palm kernel, and cowpeas for possible conversion to renewable energy in Nigeria has been made (Jekayinfa and Scholz, 2009).
However, these health hazard faced by people from the use of fuel wood, along with the agricultural wastes management and reduction of pressure mounted on the forest can be mitigated if Nigeria will switch over to production and utilization of bio-coal briquette; a cleaner, and environmental friendly fuel wood substitute made from agricultural wastes and coal. Moreover, this will offer a good potential for utilization of a large coal reserve in Nigeria for economic diversification and employment generation through bio-coal briquette.
In countries like Japan, China and India, it was observed that agricultural waste (agro residues) can also be briquetted and used as substitute for wood fuel. Every year, millions of tonnes of agricultural waste are generated. These are either not used or burnt inefficiently in their loose form causing air pollution to the environment. The major residues are rice husk, corn cob, coconut shell, jute stick, groundnut shell, cotton stalk, etc. These wastes provide energy by converting into high-density fuel briquettes. These briquettes are very cheap, even cheaper than coal briquettes. Adoption of briquette technology will not only create a safe and hygienic way of disposing the waste, but turn into a cash rich venture by converting waste into energy and also contributing towards a better environment.
Coal can be blended with a small quantity of these agricultural waste (agro residues) to produce briquettes (bio-coal briquettes) which ignites fast, burn efficiently, producing little or no smoke and are cheaper than coal briquettes.
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