Another study showing filter-equipped diesel school bus beats CNG on 'Toxics' now an SAE paper

Diesel Fuel News, March 17, 2003

For anyone who missed the clean-school-bus study from Southwest Research Institute and International Truck & Engine (see Diesel Fuel News 1/25/02, p4), now you can read it in an SAE paper (see SAE 203-01-1381). The study shows that clean-diesel buses can meet or beat CNG on most regulated and unregulated emissions, and even (in some cases) on NOx emissions, seen caused by problematic CNG exhaust sensors and natural gas that can contain too much ethane/butane or other NOx-boosting component.

However, clean-diesel defenders complain that some regulators (especially in California) keep giving CNG a free pass on non-compliant CNG fuel and excessive in-use emissions, and (thanks to certain "green" groups working with CNG lobby) give the bulk of taxpayer subsidies to the high-cost "alternative fuels" rather than lower-cost clean-diesel, to the detriment of air quality.