The EPA should reconsider the current strict mandate on Diesel road-legal emissions,regarding their particular operation in a counterpoint to a regular spark-ignited engine. Some devices such as the EGR and SCR actually just transfer the pollution from the truck's tailpipe to an industrial chimney.
The EGR (Exhaust Gas Recirculation) leads to an increasement in the Diesel fuel consumption, which can be easily diagnosed from the enhanced particulate matter emissions, altough the Diesel Particulate Filter (DPF) hides this problem. Due to its prejudicial interference in the combustion process, the EGR is not compatible with a more accurate tuning for fuel-savings, which could lead to imrpovements not just environmentally-wise but also regarding national security due to the lesser dependence on foreign oil from politically-unstable lands.
The DPF getting more demanded also leads to an increasement on the regeneration cycles required to keep its operational conditions, also enhancing the Diesel fuel consumption. We all know the oil drilling, refining and logistics involved in the final destination of its derived products (gasoline, Diesel fuel, kerosene, among others) have its own environmental impact and a high energy expense, enhanced due to the misguided EPA standards which are actually not so effective concerning to environment protection.
Another currently-mandatory device, the SCR (Selective Catalyst Reduction) is also not so “clean”, since it increases the logistics complexity involved in Diesel vehicles' operation and leads to a high consumption of purified water, and also in case of an accident with leakage from the on-board urea tank it can easily contaminate water courses nearby, including underground waters.
Winter time is also critical for Diesel operators, since EGR-equipped vehicles have harsher start-ups and take a longer time to get a stable idling speed, which increases the particulate matter emissions due to the longer cold-phase after the start-up. The SCR is also a source of problems, since the urea-based fluid is easily prone to freezing due to the 67,5% water content.