Combustion and energy content comparison of loose biomass briquettes produced from cow dung and cactus binders

This paper compares combustion behaviour and energy content of cow dung and cactus bonded briquettes. Briquettes were produced using yellow thatching grass, groundnut shells, sugarcane leaves, Mopani leaves and combination recipe (composed of all loose samples) collected from a location in the north eastern part of the Limpopo province. The aim was to identify loose biomass feedstock available in that location to sustainably produce good quality briquettes with the highest energy content and good combustion behaviour. Cow dung and cactus were selected as binders during the briquetting process. Briquettes produced with cow dung binder exhibited good performance with regards to improved energy content. The briquettes were produced for varying compaction pressures of 6, 12 and 19 MPa. Cow dung bonded briquettes were found to have the highest energy content across all pressures. At 6 MPa, Mopani leaves briquettes had 21.53 MJ/kg, groundnut shells 16.85 MJ/kg at 12 MPa and sugarcane 19.11 MJ/kg at 19MPa. The lowest energy content for cow dung was reported with yellow thatching grass at minimum average of 14.84 MJ/kg across all pressures. Cow dung bonded briquettes were found to have the highest combustion rates across all pressures with groundnut shells recording 209.67 g/min at 19 MPa, 104.71 g/min at 12 MPa and 83.16 g/min at 6 MPa. The lowest performance was recorded for sugarcane leaves at 38.13 g/min. Cactus bonded briquettes were found be very low on both energy content and combustion rates due to its pressure insensitivity and higher moisture content. The highest energy content for cactus bound briquettes was found to be at 16.49 MJ/kg for Mopani leaves followed by groundnut at 15.5 MJ/kg with the lowest at 12.6 MJ.kg for yellow thatching grass. The highest combustion rate was found at combination recipe with 59.48 g/min followed by Mopani leaves at 53.91 g/min. The lowest was 3.36 g/min for yellow thatching grass. Overall, cow dung bound briquettes performed better than cactus briquettes for all compaction pressures.