On black carbon emission from automotive disc brakes

Black carbon, as a series of light-absorbing carbonaceous material, contributes significantly to current global warming. Black carbon has always been considered a product of incomplete combustion of fossil fuels and vegetation. In the road transport sector, combustion exhaust is thought to be the primary source of black carbon. This study uses a pin-on-disc tribometer to simulate automotive disc brake system and investigate its black carbon emission. The results verified the existence of black carbon emission from disc brake system. Brake pad surface treatment and graphite content also have strong influence on black carbon emission of disc brake contact. A scorched brake material features lower black carbon and particulate matter emissions than non-scorched brake materials. Meanwhile, high graphite content in the brake material tends to expedite black carbon emission. Black carbon emission shows a proportional correlation with PM1 levels from disc brake system. The fraction of black carbon in PM1 depends on the surface condition and graphite content of the brake materials. Future studies on the emission levels of black carbon under different traffic conditions and morphology of non-exhaust black carbon is suggested, which is essential for the enactment of relevant legislations and reduce its impact on global warming.