Heavy-duty diesel vehicle Nox̳ aftertreatment in 2010 : the infrastructure and compliance challenges of urea-SCR

Abstract

Increasingly stringent heavy-duty vehicle emission regulations are prompting the use of PM and NOx aftertreatment systems in the US, the EU and Japan. In the US, the EPA Highway Diesel Rule, which will be fully implemented in 2010, has stimulated debate over whether urea selective catalytic reduction (urea-SCR) or lean NOx traps (LNT) are the better NOx aftertreatment approach for meeting this new standard. And, if urea-SCR is indeed the preferred option, how can its compliance and infrastructure challenges be overcome during the relatively short window of time between now and 2010. This thesis begins by performing a comprehensive technical and economic assessment of urea-SCR and LNT aftertreatment to determine which technology is more appropriate for use in heavy-duty vehicles and how sensitive that judgment is to changes in key variables, such as the price of urea. The focus then shifts to an exploration of the various compliance and infrastructure challenges associated with urea-SCR, namely the need to have a replenishable supply of urea. In particular, the actions and policies necessary to surmount those obstacles are discussed. Next, the policies and market factors that played a role in the EU's successful introduction of urea-SCR are examined and assessed for their ability to be applied in the US context. Finally, the long-term viability of urea-SCR is appraised through an investigation of the potential for competing emission control technologies to emerge and the prospect that urea-SCR becomes adopted by the light-duty diesel market. This thesis concludes by offering both a prognosis for what can be expected to occur between now and 2010, given the current course of action, as well as policy recommendations for how that trajectory might be corrected, such that the introduction of urea-SCR in 2010 is achieved with the maximum air quality benefit at the lowest cost.