India Environment Portal Knowledge for change

The CNG imperative

• 30/03/2001
• Down To Earth

CSE Pollution Load Model
CSE estimated the actual impact of moving public vehicles to cng fuel on the air pollution load of Delhi.

The model helps to predict the future vehicular pollution load in two possible scenarios. Impacts of interventions such as those ordered by the Supreme Court are measured against (i) a no-change scenario where the vehicles continue to emit as now. This baseline scenario, however, includes implementation of Euro i and Euro ii standards for cars and a ban on commercial vehicles over 15 years old. (ii) Impact of other interventions like improvements in vehicular standards, fuel quality, changes in transport modes, improvements in emissions and emergency measures like restricting traffic on highly polluted days.



This is the first policy tool of its kind developed in India for air quality management. It helps to identify measures needed to achieve clean air by a specified date. cse is using this model to develop an action plan that would ensure clean air in Delhi by 2010 or 2015. The model will later be made available to state pollution control boards to develop action plans for their own cities.
Setting the target
As the first step in air quality management, cse set out to know the precise amount of emissions that needs to be brought down to achieve clean air round the year. According to the Central Pollution Control Board, clean air is defined as achieving ambient air pollution levels that are 50 per cent of the standards set for each pollutant, round the year. Therefore, cse took the peak ambient pollution in a recent year and estimated the reduction needed to achieve the clean air level. It has then used the same ratio to reduce the vehicular pollution load to a target level. In the case of particulates, pollution load has to be reduced by over 90 per cent of the current load. In the case of oxides of nitrogen, the required reduction is about 70 percent. Both particulate pollution and nitrogen oxides are the key concerns from diesel vehicles.

This is still a rough picture because for predicting ambient pollution reduction, the model will have to consider atmospheric factors like rain, wind, temperature and other meteorological conditions that affect pollution concentration in the atmosphere. This can be done only with the help of an additional model called an atmospheric dispersion model which will show how pollution by vehicles, industries, power stations and generators together with meteorological conditions to create air pollution concentrations. cse intends to develop such a model over the next year.

Allowing Euro ii diesel taxis and buses to ply would mean lesser reduction in particulate emissions, but a greater threat to public health.

Any slippage on the cng strategy cannot be allowed as Delhi is reeling under severe particulate pollution load killing one person per hour. cse study proves that implementation of the court order to move all buses to cng is critical to get near the clean air targets by 2010.