Emissions of EC, OC, and PAHs from cottonseed oil biodiesel in a heavy-duty diesel engine.

Biodiesel fuels, made from renewable resources, have emerged as viable alternatives to conventional diesel fuel, but their impact on emissions is not fully understood. This study examines elemental carbon (EC), organic carbon (OC), and polycyclic aromatic hydrocarbons (PAHs) emissions from cottonseed oil biodiesel (CSO-B100). Relative to normal diesel fuel, CSO-B100 reduced EC emissions by 64% (±16%). The bulk of EC emitted from CSO-B100 was in the fine particle mode (<1.4 μm), which is similar to normal diesel. OC was found in all size ranges, whereas emissions of OC(1.4-2.5) were proportionately higher in OC(2.5) from CSO-B100 than from diesel. The CSO-B100 emission factors derived from this study are significantly lower, even without aftertreatment, than the China-4 emission standards established in Beijing and Euro-IV diesel engine standards. The toxic equivalency factors (TEFs) for CSO-B100 was half the TEFs of diesel, which suggests that PAHs emitted from CSO-B100 may be less toxic.