Environmental impact of catalytic converters and particle filters for agricultural tractors determined by life cycle assessment

Emissions from agricultural tractors have a detrimental impact on health and the environment. Stricter emission standards have resulted in great reductions in emissions from new vehicles. However, the long life time of tractors means that emissions from older vehicles remain substantial. One way to reduce these emissions is to retrofit catalytic converters, but the manufacture and use of catalytic converters consumes resources and slightly reduces engine efficiency. Life cycle assessment (LCA) can be used to determine their full environmental impact.This study considered three after-treatment options: no retrofit; a diesel oxidation catalyst (DOC)/diesel particulate filter (DPF) system; and a selective catalytic reduction (SCR) catalytic converter. Two vehicle usage patterns were considered, one following the legal test cycle (used for all off-road vehicles) and one corresponding to average agricultural tractor usage.With most of the assessment methods used in LCA, the impact change was small and totally dominated by changes in tractor emissions. All assessment methods gave the SCR catalytic converter a better value than the DOC/DPF system. The DOC/DPF system decreased the impact on human health, while the SCR catalytic converter decreased the acidification and eutrophication impact. Both catalytic converter increased abiotic resource consumption substantially. The legal test cycle produced similar results to the agricultural tractor usage cycle.

► Three after-treatment options for agricultural tractors investigated.
► Life cycle assessment used to determine total environmental impact.
► Local emissions from tractors dominated the total impact for all options.
► Low impact from catalyst relative to CO2 & fuel with most assessment methods.
► Legal standard and tractor specific usage patterns produced similar results.