Brazil is the largest worldwide producer of alcohol and sugar from sugar-cane and has an extensive alternative
program for car fuel which is unique. In the bagasse burning process, black fumes are expelled
through the chimney (fly ash recovered in the gas washer), and a
clearer ash falls to the bottom of the boiler (bottom ash). Tens of
thousands of tons of this fly ash (principally carbon and silica)
are released into the atmosphere (airborne fly ash) every year
and can be a health hazard.