Effect of Fuel Material Compositions on Combustion Properties of Wood Chips from Smallhold Farm Plots in a Sudano-Sahelian Environment of Nigeria

Aims: The study explored the combustion properties of woods and barks of some selected trees and the mixtures of the two in order to map out how fuel material composition affect the combustion properties of biomass materials.

Study Design: The study is a two-factor factorial experiment in a completely randomized design. The main factors are the tree species and fuel material types.

Place and Duration of Study: Tree samples used for this study were coppiced stems harvested from smallhold farm plots along the Damaturu - Gujba fuelwood corridors in Yobe State. The analytical study was carried out in Wood and Fibre Science Laboratory of the Department of Forestry and Wildlife, University of Maiduguri, Nigeria between April 2018 and December 2019.

Methodology: Ten tree species were used for this study. Each species was replicated 3-times, making a total of 30 stems with their dbh between 10 and 15 cm. A sample billet of 20 cm log was cut from each stem at 10 cm below and above dbh. Each billet was debarked, chipped separately and dried to approximately 12% moisture content. From the chips, 100% wood, 95%W-5%B, 90%W-10%B and 100% bark fuel material samples were created, grinded with mechanical grinder and sieved to approximately 0.4 mm particle size based on ASTM D2013-86. The sieved samples obtained were then analyzed for their percentage moisture content, volatile matter, fixed carbon, ash and gross calorific values using ASTM standard methods. The data obtained were subjected to Analysis of variance from which % variance component and LSD were computed α = 0.05 and 0.01 level of significance.

Results: All the measured parameters varied significantly among the tree species and the compositions of the fuel materials obtained from them. Majority of the variation in the fuelwood properties were attributed to the composition of the fuel materials obtained from the trees rather than the species they were made of. On the average, moisture content of the samples ranged from 27.66 to 40.44%, volatile matter (61.38 to 75.11%), ash (0.52 to 2.42%), fixed carbon (24.19 to 36.20%) and gross calorific value (32.99 to 33.02 MJ.kg-1). The moisture and ash contents of the fuel materials obtained from all the tree species increased with the level of bark inclusion whereas, volatile matter content and gross calorific values decreased significantly with level of bark inclusion (P < 0.05). Also, gross calorific value of the fuel materials correlates positively with volatile matter and fixed carbon contents. But, correlate negatively with moisture and ash contents. Among the studied tree species, chips obtained from A. leiocarpus had the highest energy value, followed by C. arereh and B. aegyptiaca while P. reticulatum, A. sieberiana and C. lamprocarpum had the least energy value in that order.

Conclusion: Based on their energy value and ash content, minimizing the bark content in wood chips is important from energy and environment point of view. Therefore, chips with 100% wood and those with 5% bark inclusions are recommended for heat generation.