Can EVs solve India's air pollution crisis?

Running entirely on electricity, battery operated electric vehicles (EVs) eliminate exhaust (or tailpipe) emissions. Several studies have indicated that transport is one of the largest sources of air pollution in Delhi, and in several other major Indian cities. This has led to many policies encouraging widespread EV adoption for combating poor air quality. And yet, while EVs can help improve local air quality, simply replacing existing vehicles with EVs will not be sufficient[1]. EVs could not only lead to increased emissions upstream, but potentially also worsen non-exhaust emissions.

Government agencies across India have been promoting EVs over the last few years. The recently reinstated Commission for Air Quality Management (CAQM), in its effort to mitigate air pollution in the National Capital Region (NCR) and adjoining areas, has urged state governments to expedite the notification of incentive-based policies for the promotion of EVs. The Delhi Government has also exempted EVs from restrictions on vehicular movement instated due to extreme levels of air pollution. These moves come amidst the backdrop of a wider push for electric mobility in the country, such as the launch of the Production Linked Incentive (PLI) Scheme to encourage the localisation of EV cell manufacturing in India, and the national-level FAME II subsidy scheme for EVs being bolstered by 20 states having drafted or notified an EV Policy.  Key benefits of EVs include the potential to reduce air pollutant emissions, carbon emissions, total cost of ownership of vehicles and fuel imports.

For pollution mitigation, there are two important factors that determine whether and how much EVs lead to net-benefits.

Exporting emissions elsewhere

First, while EVs eliminate emissions at the exhaust stage, these emissions get displaced upstream to the power generation stage. This means that for EVs running on thermal energy, vehicular exhaust emissions shift from areas with high vehicle density to where thermal power is generated – essentially exporting emissions from cities to other parts of the country. In reality, the electricity consumed by an EV at any given point originates from a specific energy supply mix, which consequently determines the level of emissions produced to power the EV. The energy supply mix is heavily context dependent – it can differ depending on both the location and time of charging. For example, an EV charging during the day is likely to have a far larger share of its energy originating from green sources such as solar, as compared to an EV charging at night. The share of various sources is also constrained by the installed capacity of these power sources and their utilisation. India, in particular, still generates nearly 80 percent of its power from fossil fuels. Emissions from these plants largely continue unabated as the country has struggled to introduce pollution control technologies[2]. Studies (1, 2) have indicated that should a transition to EVs be accompanied by a transition to a cleaner energy supply mix in the near future, India is likely to benefit from the reductions in air pollutant emissions present in internal combustion engine-based vehicle (ICEV) exhausts such as: particulate matter (PM), oxides of nitrogen (NOx), sulphur dioxide (SO2) and carbon monoxide (CO). The benefits would be relatively modest (and in the case of sulphur dioxide – non-existent), however, should the integration of more renewable energy sources and the installation of pollution control technologies fail.

Non-exhaust emissions could increase

Second, EVs also do not eliminate non-exhaust emissions. Singh et al. (2020) identify four types of non-exhaust emissions: brake wear, tyre wear, road wear and dust resuspension. Friction is responsible for the emissions resulting from wear, whereas several parameters such as “the state of (the) pavement, silt on the road, road surface humidity, vehicular weight and speed, and climate variables such as temperature, humidity and rainfall” play a role in determining the emissions due to resuspension. The road surface or pavement is also a crucial factor, as unpaved or partially paved roads can lead to significantly more PM emissions. The rate of silt loading on Indian roads is several times greater than the rates seen in more developed countries, exacerbating resuspension. Further, particles emitted by other sources such as thermal power plants and construction sites also accumulate on roads and get resuspended due to traffic (1, 2).

Figure 1: PM emissions from vehicular exhaust and non-exhaust sources in megacity Delhi. Source: Singh et al. (2020). Note: 1 gigagram or Gg = 1 kilotonne or one hundred thousand kilograms

Figure 2: Contribution of emission sources to emissions from different vehicle categories. Adapted from Singh et al. (2020). Note: HCV = heavy commercial vehicles; LCV = light commercial vehicles; 2W = two-wheelers; 3W = three-wheelers .

In their study, Singh et al. (2020) estimated that 86% of annual PM10 emissions from vehicles were due to non-exhaust emissions. Dust resuspension was the chief contributor to non-exhaust emissions, accounting for nearly 80 percent of the total. Strikingly, resuspension accounts for about 90 percent of the total emissions arising from cars and buses.  As exhaust emission standards for ICEVs have improved worldwide, the relative share of non-exhaust emissions in the total contribution of vehicular emissions has grown.

Non-exhaust emissions thus also become especially relevant when considering EVs. An increase in weight, in particular, can cause a significant increase in resuspension. Heavier vehicles also grind coarser grains into finer particles – further increasing resuspension. Timmers and Achten (2016) found that EVs on average are 24 percent heavier than corresponding ICEVs, which results in comparable amounts of PM10 and PM2.5 emissions from both EVs and ICEVs. While this is a serious concern, the elimination of exhaust emissions by EVs remains a benefit, as aerosols produced by combustion are typically more toxic than those of non-combustion origin.

Clearly, a 1:1 substitution of ICEVs to EVs alone is unlikely to improve overall air quality significantly. Generating more power from renewable energy sources, and incentivising charging at times when this power is available could significantly mitigate displaced air pollutant emissions resulting from EV charging. Successful implementation of pollution control technologies and sustained enforcement of emissions standards at coal-fired plants would also lead to cleaner EVs, and mitigate resuspension of accumulated PM dust originating from thermal power plants. Dust mitigation strategies[3] – if implemented successfully – could lead to a significant decrease in non-exhaust emissions. It is also important to not view EVs as a blanket solution to vehicular emissions. The role of non-exhaust emissions, and the near-constant growth of the vehicle population counteracting the gains made by improved emissions standards, makes it apparent that a shift away from the existing paradigm of mobility is needed. Promoting and integrating public transportation and non-motorised transport should be central to any future vision of mobility, with EVs playing a supporting role.

Footnotes:

[1] The focus of this piece is on ambient air pollutant emissions from EVs during their usage, and not on greenhouse gas emissions or other lifecycle environmental impacts of EVs.

[2] The deadline for the installation of Flue Gas Desulphurisation units has once again been pushed back from the initial proposed year of 2017, to as late as 2025 for some plants. Further, compliance remains extremely low. Sources: 1, 2.

[3] Strategies include: reduction of dust originating from non-transport sources such as construction and other combustion sources; resuspension mitigation by promoting lighter, slower and fewer vehicles; and the application of chemical or greening-based dust resuspension mitigation techniques. Sources: 1, 2, 3.

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(Environmentality is a collection of ideas, perspectives, and commentary by researchers at the Initiative on Climate, Energy and Environment, Centre for Policy Research, New Delhi. Views and opinions expressed in this blog are solely those of the authors. They do not represent institutional views.)