The days of semi trucks blowing off black smoke are soon to be over. Next year in January, California’s ban on large, diesel trucks (semi trucks and buses) made before 2010 will go into effect. So, why before 2010? Starting in 2008, the EPA mandated that all large diesel trucks have Diesel Particulate Filters (DPF) installed, which drastically reduces the toxic particulate matter (soot) emitted by the exhaust of diesel trucks. This also increased fuel efficiency, as captured soot in the filter can burn to produce energy for the truck. Then, the EPA mandated Diesel Exhaust Fluid (DEF) in all trucks made after 2010.
DEF is a fluid used to treat the exhaust, which in a Selective Catalytic Reduction (SCR) system, reduces NOx (nitrogen oxides) emissions to near zero. Trucks before then of course have no DPF or DEF, because their emissions were never regulated, meaning there was no effort to have technology to reduce emissions. As such, they’re quite dirty air offenders, and is why all trucks made before 2010 are targeted by California’s ban. This can greatly hurt trucking companies that may have ponied up to buy “newer” trucks right before the EPA mandates (2007), as large diesel trucks can easily last for decades. Oh well, they can still operate out of California, for now, before other states, if not the country, follows suit.