Production, characterisation and economic validation of fuel pellets from Cassia Tora (Tafas in hausa language) for domestic and industrial applications

Abstract

ABSTRACT A laboratory scale method was used to produce pellets from cassia tora stems with pelletizing temperature conditions of 30, 45, 60, 75, 90, 105 and 120oC under a pressure of 50, 70, 90,120 and 140 MPa. A total of 30 pellets were produced under each condition of production. The physical and chemical properties of the pellets were investigated. The pellets produced under 75oC and 90 MPa were found to have durability 90 %. A Bulk density range of 617 to 619 kgm-3 was measured for all the produced pellets irrespective of production conditions. The pellets produced in the range of 50 MPa/30oC-140 MPa/120oC were found to have a moisture content ranging between 7.18- 9.6 %. Ash content of 4.2 % was achieved using both Thermogravimetry (TGA) and CEN/TC 335 standard. The gross calorific value of the pellet was determined to be in the range of 17.89-18.1 MJ/kg. TGA results also indicates low moisture and ash content and the process of pyrolysis occurred at 137-550oC at 10oC/min heating rate. The activation energies and reactivities determined from TG/DTG curve are 72.01, 106.81 and 88.67 kJ/mol and 1.76 E+19, 5.1 E+06 and 3.92 E+05 for step I, II and III respectively. A water boiling experiment was carried out to evaluate the cooking efficiency of the pellets compared to fuel wood, kerosene and liquefied natural gas (LPG). The energy intensities and energy cost of 1.2, 0.78, 0.56 and 1.36 kJ/g of water and 0.2, 0.7, 0.4 and 0.2 Nigerian Naira (N) were calculated for fuel wood, kerosene, LPG and the pellets respectively. vii An economic analysis of fuel pellet production from Cassia tora stems has been carried out for conditions found in Kano state, Nigeria. The total production cost, for a base case scenario of 5t/h and operating for 270 days a year, is £4/tonne (1094.5 Naira/ton) of pellets. A ‘Willingness to pay’ analysis was also performed using the Contingent Valuation Technique. A structured contingent valuation questionnaire was administered to 420 randomly selected households in the Kano metropolis and Chi-square analysis was conducted on the data collected. The results of the analysis, at a 5 percent (0.05) confidence level, showed that p-values were less than 0.05 (0.05>p) for all the responded variables. It is confirmed, from the analysis, that an inadequate supply of energy is a statistically significant problem in Kano state and households significantly use fuel wood for domestic energy applications. The results also indicated the willingness of households to switch to a new product and were willing to pay a mean amount of £5 (1361.5 Naira) for a ton of the fuel pellets. Properties of the cassia tora pellets were found to be comparable with other biomass fuel pellets. It is recommended that policy and investment should be geared towards fuel pellet production in Nigeria, to address problems of energy poverty and environmental deterioration, and provide a means for further economic development.