Combustion behaviour of loose biomass briquettes resulting from agricultural and forestry residues

Reliance on round wood for heating and cooking has increased the percentage of deforestation to 0.7% per annum especially within sub-Saharan region where communities live off the electricity supply grid. The majority of these communities rely on agriculture and forestry activities for sustenance. Therefore, large amounts of agricultural and forestry residues are produced annually although they are considered to be of low energy content. This paper investigates the combustion behaviour of the loose biomass briquettes produced from residues collected from a rural community in the Limpopo Province of South Africa. These included mopane leaves, ground nut shells, sugar cane leaves, yellow thatching grass, cactus plant and cow dung among others. Biomass briquettes were produced from these residues for various proportions and compaction pressures (6, 12 and 19 MPa) with cow dung or cactus plant as a binder. The produced briquettes were tested for energy content and burnt in a biomass briquette stove while monitoring mass decay or burn rate and temperatures. The optimum briquettes were found to be of the cow dung binding compacted at a pressure of 19 MPa.

Introduction

Energy supply for space heating and cooking for off grid communities has been a challenge for many centuries, more so in Sub-Saharan Africa. The most convenient available sources include round wood, despite the free available loose biomass generated annually from agricultural and forestry activities. It is reported that loose biomass in the form of agricultural and forest residues has low energy content resulting poor combustion behaviour [1].