Biodiesel is often touted as a cleaner alternative to fuel derived from crude oil. Research published in the International Journal Environment and Pollution shows that in the urban region of Porto, Portugal, where biodiesel is widely used particulates and some gaseous pollutant levels are lower, but toxic ozone levels are higher, and nitrogen dioxide levels are the same as they would otherwise be if conventional diesel were being used.
Isabel Ribeiro and colleagues at CESAM and Department of Environment and Planning, University of Aveiro, have investigated ground level atmospheric concentrations of common pollutants from diesel-powered vehicles. Carbon monoxide (CO), nitrogen oxides (NOx), non-methane volatile organic compounds (NMVOCs), 10 and 2.5 nanometre particulates, PM10, PM2.5, formaldehyde, acetaldehyde, acrolein and benzene are all released in the exhaust from diesel engines.
The researchers’ tests on standard diesel, blended biodiesel and biodiesel products show that particulate levels are much lower with biodiesel products. Particulates, which are essentially nanoscopic particles of soot have been implicated in respiratory health problems among people living in towns and cities where diesel traffic is common. The biodiesel products also generated lower levels of gaseous pollutants with the exception of one particular NOx compound, nitrogen dioxide. Worryingly, however, the team reports that ozone, which represents a pollution problem at ground level as opposed to an atmospheric essential at high altitude, is higher with biodiesel. The effect was small but measurable over the Porto urban region, the team asserts.
However, further studies are now needed to ascertain whether or not the reduction of other pollutants including NMVOCs, many of which are carcinogenic, as well as the reduction in particulates is offset in terms of public health by the rise in ozone.
Ribeiro, I., Monteiro, A., Martins, H., Freitas, S., Borrego, C., Lopes, M. (2015) ‘How does the use of biodiesel affect urban air quality?’, Int. J. Environment and Pollution, Vol. 58, Nos. 1/2, pp.79-88.