Performance analysis of butanol-diesel blends in internal combustion engines as pathway to bioenergy integration toward sustainability goals

The growing depletion of fossil fuel reserves and the pressing need to reduce greenhouse gas emissions call for sustainable alternatives for internal combustion (IC) engines. While first-generation biofuels like ethanol and biodiesel are well researched, higher alcohols such as butanol—especially from third-generation biomass—remain relatively unexplored. This study examines the performance, combustion, and emission characteristics of butanol-diesel blends (B10–B40) in a single-cylinder compression ignition (CI) engine across variable operating conditions. A particular focus is placed on evaluating the influence of injection pressure (200–260 bar) and timing (20°–26° bTDC) to identify optimal parameters for cleaner combustion. Experimental trials were conducted on a 4.4 kW, 1500 rpm engine, with B20 selected for detailed parametric analysis. Key performance indicators, including brake thermal efficiency (BTE), mechanical and volumetric efficiency, along with oxide of nitrogen (NOₓ), smoke, and unburned hydrocarbon (HC) emissions, were measured. Results showed a slight reduction in BTE with increased butanol concentration due to its lower calorific value. However, B20 offered an ideal compromise, achieving reductions in NOₓ (up to 32%), smoke (77%), and HC emissions (35%). Combustion analysis further revealed higher peak cylinder pressure and heat release rates for B20, with ignition delay and combustion duration influenced by both blend ratio and injection settings. This study highlights B20 butanol-diesel blends as a promising, cleaner-burning fuel that requires no significant engine modifications. By utilizing butanol from third-generation biomass, it aligns with global goals for renewable energy and carbon neutrality in transportation.