What are the worst polluters in Delhi NCR? Here’s what a TERI report says

The 2021 draft report was prepared by The Energy and Resources Institute (TERI). The Delhi government had tasked TERI with the task as part of a project to identify sources of pollution in real-time. For Delhi, while the report estimates emissions from different sources within the city, it does not factor in the contribution of sources from outside Delhi.

What did the inventory say about Delhi?

While vehicles are the single largest contributor to most of Delhi’s air pollutants, tailpipe emissions from two-wheelers form the largest chunk of vehicular emissions.

Of the six air pollutants that the draft report lists, vehicles are the largest contributors to three. Vehicles are the largest emitters of PM2.5 in Delhi, making up around 47% or 9.6 kt/year (kilotonnes per year) of the total estimated PM2.5 emission of 20.32 kt/year. This was followed by road dust (20%, 4.09 kt/year of PM2.5). Vehicles are also the largest emitters of nitrogen oxides (Nox), contributing 78% or 119.6 kt/year to the estimated Nox load of 153.53 kt/year, and non-methane volatile organic compounds (NMVOCs), contributing around 49% (88.02 kt/year) of the total load of 180.52 kt/year.

Of the six air pollutants that the draft report lists, vehicles are the largest contributors to three. (Graphic: Ritesh Kumar/Express)

Among vehicles, two-wheelers are the largest source of PM2.5, PM10, sulphur dioxide, and carbon monoxide. Three-wheelers are the largest source of VOCs, while buses have been identified as the largest source of Nox (see box).

What did it say about NCR?

In the NCR (which includes Delhi, 13 districts of Haryana, eight districts of UP, and two districts of Rajasthan), the report identified industries as the largest source of particulate matter (41% contribution to PM10, 44% to PM2.5), followed by stone crushers (22% to PM10, 19% in PM2.5). Power plants in the NCR are the largest contributors of SO2 (46%), while transport contributes the most to carbon monoxide (97%), VOCs (58%), and Nox (66%).

This inventory, however, estimates sources of pollution before the ban on coal use kicked in across the NCR. The Commission for Air Quality Management ordered in 2022 that coal use for industrial and domestic purposes would be banned in areas with PNG supply from October 2022 onwards, and in other areas from January 2023 onwards. It continued to allow the use of coal in thermal power plants.

Among vehicular sources in the NCR as well, two-wheelers are the largest contributors to PM2.5 (31%) and CO (51%), while buses contribute the most to Nox (34%).

For NCR, this inventory estimates sources of pollution before the ban on coal use kicked in.

The report also points to a continued use of fuelwood in Delhi and in the NCR. Having collected information through household surveys, the report estimates that “the average per capita consumption of fuelwood and LPG in slum households of Delhi was 560 kg and 45 kg respectively during 2021.” Where fuelwood contributes around 0.8 kt/year to PM2.5 levels and 1.1 kt/year to PM10 in Delhi, LPG contributes 0.2 kt/year to PM2.5 and PM10 each, the report estimates.

What did the earlier emission inventories for Delhi say and how is this one different?

Delhi has had three other emission inventories over the past decade.

IIT Kanpur: An inventory for Delhi developed by professors at IIT Kanpur, based on data collected in 2013-14 and submitted to the Delhi government in 2016, shows a slightly different picture.

In 2013-14, industrial emissions in Delhi contributed a large share to gaseous pollutants and PM10. In the years since then, industries in Delhi were directed to run on piped natural gas (PNG). The largest contributor to PM2.5 was road dust (38%), followed by vehicles (20%), while the largest chunk of PM10 came from road dust and industrial sources. The largest contribution of SO2 and Nox also came from industrial emissions. Vehicles were the largest contributor only to one of five pollutants the inventory listed — carbon monoxide (83%).

Among vehicles, the largest contributor to both PM10 and PM2.5 in the IIT Kanpur inventory was trucks, making up around 46% of each type of particulate matter emissions. This was followed by two-wheelers, contributing around 33% each to PM10 and PM2.5. While buses were the largest emitters of Nox, two-wheelers contributed the most to carbon monoxide, and four-wheelers were the largest emitters of SO2.

Since then, the Eastern and Western Peripheral Expressways became operational in 2018, which are meant to divert traffic not destined for Delhi. Delhi Environment Minister Gopal Rai has repeatedly appealed to Haryana and UP to ensure that truck traffic not destined for Delhi is diverted via these routes.

SAFAR: An emission inventory developed by the Indian Institute of Tropical Meteorology’s System of Air Quality and Weather Forecasting and Research (SAFAR) in 2018 pointed to transport as the largest source of PM2.5 (41%) and Nox (76%), while dust was the largest contributor of PM10 (55%).

TERI/ARAI: TERI and Automotive Research Association of India made an inventory for 2016 for Delhi and the NCR, which was part of a report prepared for the Ministry of Heavy Industries. This identified transport as the largest contributor of PM2.5 (39%) and Nox (81%) in Delhi.

Road dust contributed the most to PM10 (35%), while power plants (Delhi had two coal-fired plants — Badarpur and Rajghat, which have been shut since then) contributed the largest share of SO2 (71%). Within the transport sector, trucks contributed the most to PM2.5 levels (32%), followed by two wheelers (26%).

Why is an emission inventory important?

The draft report stated that “one of the preliminary steps towards forming an air quality management plan is to generate source-wise emission inventories of different pollutants…Also, emission inventories are an important input to the atmospheric models for simulation of atmospheric pollutants.”

The emission inventory is crucial to the Air Quality Early Warning System (which provides air quality forecasts) and the Decision Support System (DSS, which helps determine the sources of PM2.5 on a day, and provide an estimate of the contribution from these sources for the next three days), both of which are projects by the Indian Institute of Tropical Meteorology. These systems are important for decision making — emergency measures for pollution mitigation kick in based on forecasts.

A team member who is part of the two projects said they were waiting for data from certain sectors of the 2021 emissions inventory to update the forecasting system. “Since the inventory had not been updated, we were using an earlier TERI inventory, which we projected for 2021 and used. It is important to have an updated inventory, otherwise there could be some uncertainties in source attribution. The international practice is to update the inventory every three years or so, since large changes (on the air pollution front) don’t occur in the short term. But for Delhi-NCR, considering the measures and changes in policy, it needs to be done in six months to a year. Since an inventory cannot account for every small source, there will still be uncertainties, but it needs to be updated,” the team member said.

The draft report on the inventory, dated January 2023, has not been made public, but was submitted to the Central Pollution Control Board (CPCB) by the Delhi Pollution Control Committee (DPCC). In 2022, the CPCB wrote to the DPCC, and the pollution control boards of UP, Haryana and Rajasthan, stating that, as per a Commission for Air Quality Management (CAQM) policy document, updating the emission inventory and source apportionment study in the NCR must be completed by December 2023 for Delhi and the nearby districts. The CPCB wrote to the DPCC and the State PCBs again in 2023 reminding them to submit the “peer reviewed EI (emission inventory) and SA (source apportionment) report” to the CPCB.

In a matter concerning air pollution in Delhi, the CPCB told the National Green Tribunal (NGT) in December last year that for Delhi-NCR districts, a draft emission inventory report was submitted by the DPCC.