ANALYSIS OF ENERGY CHARACTERIZATION OF RICE AND COFFEE HUSK BLEND IN NIGERIA

ABSTRACT
Production of first generation biofuels using food crops is under criticism over sustainability issues on food security. Tanzania is showing active interest in developing second generation biofuels to deal with some of such issues, especially from the feedstock point of view. This project work determine energy characteristics of rice and coffee husks blend in Nigeria. The results show that coffee husks have better energy quality than rice husks, while heating values of coffee are 18.34 MJ/kg and 13.24 MJ/kg for rice husk. Thermogravimetric analysis made for coffee husks blended rice husks at a ratio of 75 : 25% vol. show better material degradation characteristics yielding low residual mass of 23.65%, compared to 26.50% of char and ash remaining in pure rice husks. Derivative thermogravimetric analysis shows comparable hemicellulose degradation peak values of −11.5 and −11.2 and cellulose −3.20 and −2.90 in pure coffee and rice husks, respectively. In coffee and rice husks blends, substantial reductions of hemicellulose and cellulose peaks were observed. Use of coffee and rice husks blends applying high temperature gasification would reduce the latter’s flammability, while increasing its flame retention characteristics, hence offering opportunities for production of clean syngas in a sustainable manner.

INTRODUCTION
For many years, we have consumed fossil fuels with no worries about possible shortages, but, now, those same oil fields are running dry, while use of coal as a source of energy is also facing criticisms due to its contribution on environmental pollution, D. A. Mwakipesile (2012). In view of this situation, there has been a growing impetus looking for alternative sources of energy for the future. Biomass based second generation biofuels could partly assist to resolve some of these issues, especially from the feedstock point of view for energy production applying various conversion methods to improve the combustion efficiency, Tyebkhan G (2002). The advantages of using biomass are obvious as this material, is generally left to rot or burnt in an uncontrolled manner, producing CO2 as well as smoke.

Most African countries are facing problems of inadequate access to modern sources of energy, P. J. Haines (2002). The United Republic of Tanzania being one of the sub-Saharan African countries is showing active interest in the development of the second generation biofuels, especially from the feedstock point of view to address criticism over sustainability issues as well as arguments on food security arising from the production of 1st generation biofuels derived from food crops materials to replace the current use of petroleum products, P. J. Haines (2002).
Use of biomass materials, referred to as the second generation biofuel, derived from agricultural wastes and forest residue and a number of fast growing trees, and grown specifically for energy purposes, could provide opportunities for nonfood based feedstock materials. Tanzania is endowed with biomass potential for energy production originating from forest plantations and agricultural wastes supported by the already existing infrastructure for their deployment, Tyebkhan G (2002).

The conversion of biomass materials to gaseous or liquid form of energy is known to be easier to handle and make applications. Varied schemes of processes for converting biomass into valuable fuels also exist. These include biological processes to make ethanol or methane and thermal processes to make heat, gaseous fuels, liquid fuels, and solid fuels. During the process, a variety of secondary products can also be produced from the liquid and gaseous fuels. In this form, because of added value, the derived fuels can be used to produce electricity.

This paper reports on work done to determine the energy characteristics of selected agricultural residues originating from rice and coffee husks. The study conducted thermogravimetric analysis to obtain information on thermodegradation behaviour of the biomass materials and their main components (hemicellulose and cellulose). Use of the derivative thermogravimetric (DTG) analysis has also been made in order to establish materials suitability for the production of clean syngas for electricity generation in a sustainable manner applying high temperature gasification technology.