Abstract
This study compares emissions from Euro VI-D Diesel and CNG buses across temperatures from -7 °C to 35 °C. Pollutants including NOx, THC, CH(4), CO, NH(3), N(2)O, HCHO, Solid Particle Number larger than 23 nm (SPN23) and larger than 10 nm (SPN10) were measured. Both buses complied with Euro VI-D but exceeded European Commission's proposed Euro 7 limits, notably for NOx and SPN10. The CNG bus also surpassed NH(3), CO, and CH(4) limits, while the Diesel exceeded N(2)O limits. High NH(3) emissions were observed from CNG (up to 0.320 g/kWh), with Diesel reporting lower levels (up to 0.021 g/kWh). HCHO emission from both vehicles were very low. SPN23 was under limits, but SPN10 exceeded Euro 7 limits at cold start tests. CNG's CH(4) and N(2)O emissions constituted up to 4.6% and 3.5% of CO(2) equivalent, respectively. Diesel bus showed negligible CH(4) but N(2)O emissions represented up to 37% of CO(2) equivalent.