Sunday, January 26, 2014

Vehicle Particulate Emissions

{Author's note: this post is about ICEs not EVs}

Atmospheric particulate matter are tiny particles suspended in air.  The particles can be both naturally occurring (volcanos, dust storms) or man-made/anthropogenic (vehicle emissions, power plants, concrete manufacturing).  Anthropogenic atmospheric particulate matter “is consistently and independently” are related to the most serious health effects including lung cancer and and cardiopulmonary deaths.  (Wikipedia, “Particulates).

Various government agencies have been working to reduce particulate emissions from a range of sources, chief among them are cars and trucks.  The classic source of particulate emissions is the older diesel cars and trucks that can be seen puffing out black smoke.  Modern diesels use particulate filters and frequently emit fewer particles than many directed injected gasoline engines.

Emissions regulations are an array of acronyms, bins, phase in dates, and other confusing jargon.  In the USA, this is further complicated by there being two different sets of emissions regulations, one created by the EPA, the other created by California but followed by many other states that can choose between either EPA or California rules.  It is slightly bizarre that the state of Massachusetts (for example) is subjected to California air quality laws.

Below are the particulate emissions limits created by the EPA which uses a “bin” system of which bin 5 is generally considered the most important because that is the median number that vehicle manufacturers must meet.  Note that emission will be reduced by almost two orders of magnitude (200 down to 3 mg/mile) from 1991 to 2025.
1991 200 mg/mile (Tier 0)
1994 80 mg/mile (Tier 1)
2004 10 mg/mile (Tier 2)
2017-2025 3 mg/mile (Tier 3)

California has a similar system (with different acronyms of course) that concludes with 1 mg/mile particulate specification by 2028.  I wonder if there will be fewer particulates coming out of the engine than going in at that point in time
2004-2007 80 mg/mile LEV1
2015-2019 10 mg/mile  (LEV2)
2017-2021 3 mg/mile (LEV3)
2025-2028 1 mg/mile (LEV3)

The Europeans have been on top of this problem as well, which is probably more important over there because of the high penetration of diesel engines in the passenger vehicle market.  Interestingly, 2014 will be the first year when they implement particulate emissions requirements on DI (direct injected) gasoline engines reflecting the tendency of DI engines to produce more particulate emissions than modern particulate filtered diesels.
1992 PM=140 mg/km,  diesel,  (Euro 1)
1996 PM=100 mg/km, diesel,  (Euro 2)
2000 PM=50 mg/km, diesel,   (Euro 3)
2005 PM=25 mg/km, diesel,  (Euro 4)
2011 PM=4.5 mg/km, PN=6e11 particles/km, diesel,  (Euro 5b)
2014 PM=4.5 mg/km, PN=6e11 particles/km,diesel+gasoline,  (Euro 6)

Emissions regulations are very complicated and the above numbers should be taken as general trends.  Undoubtedly an expert would talk about the phase-in dates and the percentages of vehicles that need to meet a given specification on a given year, or that the number only need to be achieved as a “fleet average” not for an individual vehicle, or that certain changes in gross vehicle weight will change the specification.  All that is true but the above numbers are intended to give a quick overview of the requirements, something that is desperately needed in the emissions literature.  This could be a book writing opportunity.  Who wouldn’t want a copy of “Particulate Emissions for Dummies” under their Christmas tree.