Performance, Emissions and Enviroeconomic Assessment of Diesel–Waste Tyre Pyrolysis Oil–n-Butanol Blends in a Single-Cylinder Engine

This study evaluates the performance, emissions and enviroeconomic implications of diesel–waste tyre pyrolysis oil (WTPO)–butanol blends in a single-cylinder, direct-injection diesel engine operated at 1500 rpm across 10–50 Nm. Five fuels were tested: neat diesel (D100), D90T10, D80T20, D80T10B10 and D60T20B20. Relative to D100, oxygenated blends incurred a modest fuel-consumption penalty (peak ≈ +8% BSFC), yet delivered pronounced reductions in incomplete-combustion products: carbon monoxide fell by about 50% at high load with D60T20B20. WTPO-only mixtures increased unburned hydrocarbons, whereas adding 10% butanol suppressed HC. Conversely, nitrogen oxides rose by roughly 15–45%, highest for D60T20B20, while tailpipe CO2 decreased slightly (≈4% at 50 Nm). A simple carbon-pricing lens (€70 t-1 CO₂) indicated a ~4% lower carbon-cost component for D60T20B20 than D100 at high load. Considering these trade-offs, D80T10B10 emerges as the most pragmatic configuration, balancing efficiency with air-quality benefits and moderating the NOx rise. The results support partial substitution of diesel by WTPO and butanol where NOx control (e.g., EGR or calibration) is feasible, coupling local pollutant mitigation with incremental decarbonisation and modest cost gains.