2.15 Clearing the Air – Automobiles and Other Vehicles

Where It All Begins Most poisonous gases in auto exhaust are waste products of incomplete combustion  When there is not enough oxygen, CO and unburned hydrocarbons are formed  High temp. in auto’s engine causes nitrogen to combine w/ oxygen to produce NOx In an internal combustion engine the fuel burns (explodes) inside a closed cylinder

Too Many Cars, Too Many Miles More cars are on the road over the last few decades, leading to increased congestion (traffic jams) and “wasted” fuel Cars produce 95% of all CO emissions and 55% of NOx

The Government Steps In California was first to require pollution controls on cars CAA set strict standards for 3 major air pollutants in car exhaust  Hydrocarbons  CO  NOx Several methods to reduce vehicle exhaust pollution:  Recycling vapors back into engine  Inject additional air  Catalysts to assist in complete fuel combustion

Catalytic Converter Catalytic converters – stainless steel containers that contain platinum catalyst and reduce hydrocarbon and CO emissions  Platinum allows oxygen to react w/ more CO and unburned hydrocarbons before leaving tailpipe Second-generation catalytic converters produce 70% less NOx and 90% less CO and hydrocarbons than cars w/o pollution controls

Get the Lead Out Refineries could produce high-octane fuel from low- quality crude oil by adding lead Lead was phased out of gasoline b/c it ruined catalytic converters Banned in 1996 in U.S. Still used in Middle East and Central Asia

Redesigning the Engine Stratified internal combustion engine was introduced by Honda and has 2 combustion chambers in each cylinder  Fewer NOx  More fuel can burn completely, lowering CO Diesel engine has 2 advantages over gasoline:  Less CO and hydrocarbon emissions  Better fuel economy Major problems w/ diesel engines:  Excessive NOx  Excessive PM  Diesel trucks account for 90% of vehicular PM emissions

Can We Meet the Standards? Millions of people live in areas w/ unhealthy ozone levels >30 states have inspection and repair programs  Check emission controls  Check for leaks in evaporative emission system  Closed system that collects vapors from gas tank and prevents hydrocarbons from entering the atmosphere Stage I vapor recovery – vapors are transferred to the tank truck when the truck delivers fuel to the storage tank Stage II vapor recovery – collect vapor from the gas nozzle and send it back to the storage tank

In order to meet CO standard, some states must use oxygenated fuels  Ethanol  MTBE  Banned in U.S. due to groundwater contamination Some vehicle fleets use “clean fuels,” which emits 90% less pollution  Compressed natural gas  Methanol (from natural gas)  Ethanol (from corn)  Electricity 2007 requirements for diesel vehicles include high-efficiency catalytic exhaust emission control devices Some states require employers to offer telecommumications