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Monday, March 3, 2008

Pollution from Motor vehicles and its control measures:


Pollution from Motor vehicles and its control measures:

Pollution from motor vehicle is the single largest source of air pollution emissions. Motor vehicle exhaust is a complex mixture, composition of which depends on fuel used, and type and operating condition of the engine – whether it uses any pollution control devices.

At present, motor fuels consists of Petrol, Diesel, LPG (mostly Butane) and CNG. In recent times, people have been very much successful in reducing motor vehicle pollutants; but due to enormous growth in population of vehicles on urban roads, the effectiveness of the new technology in reducing pollution is not very much relevant and practicable. Over the year, engine efficiency has also gradually improved with progress in Electronic ignition, Fuel injection systems and Electronic control unit; and so, the emission standards. The major constituents of motor vehicle pollutants are 74% Carbon monoxide (CO), 16% hydrocarbon (hc), 8.5% nitrogen oxides (NOx), 0.8% particulate matter and 0.6% sulfur oxide (SOx).

Carbon monoxide (CO): a product of incomplete combustion. Carbon monoxide reduces the human blood's ability to carry oxygen and is dangerous to people with heart diseases.

Carbon dioxide (CO2): It is well known that, carbon dioxide has very prominent role in global warming as a greenhouse gas.

Hydrocarbons (HC): This is generated due to unburned or partially burned fuel and is a major contributor to urban toxic smog. They may cause lunge, liver damage and cancer to human being.

Nitrogen oxides (NOx): These are generated when nitrogen in the air reacts with oxygen under the high temperature and pressure conditions inside the engine. NOx emissions contribute to both smog and acid rain.

Sulfur oxides (SOx): Produced by combustion of petrol or diesel.

Evaporative emissions: These are produced from the evaporation of fuel, and are largely contributor to urban smog, as these heavier molecules stay closer to ground level.

Thus, Motor vehicles contribute significantly to greenhouse gases but nevertheless the rise and rise of petrol, diesel and kerosene vehicles continues at an alarming rate. Experts say, if all vehicles were tuned correctly there would be up to:

(a) 16 per cent less tailpipe hydrocarbon emissions;

(b) 26 per cent less tailpipe carbon monoxide emissions;

(c) 9 per cent less nitrogen oxides emissions.

The expert study also revealed that, on an average, maintenance to polluting vehicles does not require the replacement of major or expensive parts. Tuning is mainly limited to the following: (a) replacing points and air filter; (b) replacing fuel filter (if necessary); (c) replacing oil and oil filter; (d) checking spark plug condition and gap—adjusting or replacing as necessary; (e) checking distributor condition and operation and adjusting as necessary; (f) checking and adjusting idle mix and speed; (g) checking and replacing spark plug and distributor leads as necessary; (h) checking and replacing hoses and other minor items in fuel/electrical/emission control system as necessary; (i) examining vehicle diagnostics and replacing faulty components.

Additional technologically advanced incorporated emission control systems may be used, such as: (i) Emissions control systems for engines using diesel, ultra-low sulfur diesel, bio-diesel, natural gas, or propane fuels; (ii) Selective Catalytic Reduction (SCR) technology to reduce NOx with the SCR Catalyst – mostly for stationary IC engines; (iii) Catalyzed diesel particulate filters to reduce Particulate Matters, CO and HC from diesel engines; (iv) Oxidation catalysts to reduce CO and HC emissions; (v) Three-way catalysts to reduce NOx , CO and HC emissions.

Engine Technology

Emissions reductions can be achieved by improving engine technology or using alternative fuels or reformulated gasoline.

Among engine improvements, the catalytic converter, which extracts pollution from exhaust, has made the largest contribution to reduce vehicles emissions in recent years. A catalytic converter does not operate effectively, however, until it reaches its operating temperature after a car has been running for a few minutes. High sulfur content in fuel has been shown to reduce the effectiveness of the catalytic converter. To reduce these emissions, a low sulfur fuel has been introduced by many Govt. Authorities. Researchers are exploring ways to reduce the time needed to heat the catalytic converter.

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