Feasibility of Using Oil from Spent Coffee Grounds in Small-Scale Marine Boilers

This study investigated the potential of using pyrolysis oil derived from spent coffee grounds (SCGs) as an alternative marine fuel to comply with the International Maritime Organization’s 2050 carbon-neutrality targets. A 30 L-class small-scale marine boiler was designed and fabricated to comparatively analyze the combustion and exhaust emission characteristics of coffee ground oil (CGO) blended with marine gas oil at blending ratios ranging from 0% to 25%. The experimental results indicated that as the blending ratio increased, the concentrations of oxygen and carbon monoxide slightly decreased, whereas those of carbon dioxide and nitrogen oxides (NOx) tended to increase. The combustion efficiency was consistently maintained at approximately 79.2%, confirming the potential feasibility of CGO as an alternative fuel. However, the study identified limitations in achieving carbon neutrality through blending alone. Consequently, further research on emulsification technologies and combustion optimization is needed to address phase separation caused by density differences and mitigate NOx emissions.