Investigation of sustainable utilization of agricultural waste through coffee husk and cow dung briquettes for domestic energy production and emission performance

The widespread use of traditional biomass fuels like firewood and charcoal in developing countries contributes to deforestation, indoor air pollution, and energy insecurity. Agricultural residues such as coffee husks offer a renewable alternative, but their direct utilization is limited by low bulk density and poor combustion efficiency. This study developed and characterized coffee husk briquettes using cow dung as a natural binder in varying proportions (0%, 10%, 20%, 30%). Briquettes were evaluated for physicochemical, thermal, chemical, and emission properties according to ASTM standards. Key results showed moisture content of 4.40–5.60 wt.%, volatile matter of 67.83–69.84 wt.%, ash content of 8.96–14.76 wt.%, and density ranging from 730.7 to 1042 kg/m³. Compressive strength varied from 2.749 to 3.679 MPa, with higher and lower heating values between 18.31–22.06 MJ/kg and 14.36–16.49 MJ/kg, respectively. Specific fuel consumption ranged from 0.10605 to 0.13665 kg/L. Emission levels of NOx and SO₂ ranged from 8.2–17.69 PPM and 170.99–201.32 PPM, respectively, within standards. The findings confirm that coffee husk briquettes with cow dung binder are a viable, sustainable energy option, suitable for rural and coffee-producing regions.