A new bill being considered in Washington State would delay, for at least a couple of years, implementation of proposed rules that constrain crediting of avoided-methane offsets in the state’s Clean Fuel Standard (CFS). These offsets expand the scope of greenhouse gas (GHG) accounting for renewable natural gas (RNG) pathways to include avoided emissions from agricultural waste management and organic waste diverted from landfills. While RNG from waste is a low-GHG resource suitable for producing alternative fuels, such offsets divert CFS support to the agricultural sector and away from transport, the largest source of GHG emissions in Washington State.

That means the constraints on the offsets, which were proposed by the Department of Ecology, are important safeguards. Any delay would endanger the effectiveness of the CFS. Let’s review why.

The ICCT has extensively highlighted issues with unrestricted avoided-methane offset crediting for RNG in clean fuels programs, and California indeed adopted some restrictions in its recent Low Carbon Fuel Standard (LCFS) rulemaking. Washington’s proposed CFS update follows suit and would introduce a 15-year limit on avoided methane crediting for each RNG project. It would also require that participants demonstrate that at least some RNG is physically flowing into Washington; this starts in 2032 for fuel used in vehicles and in 2037 for RNG used for production of other alternative fuels. But there’s also a provision in Senate Bill (SB) 5601 that would override these safeguards, at a minimum through 2026. Its language targets RNG used for producing sustainable aviation fuel (SAF). But the proposed rules are not SAF-specific. Therefore, the safeguards could be jeopardized if SB 5601 is adopted as currently written.

There are two primary reasons for the concern. First, for as long as avoided-methane offsets are in use, a fuels program is not technology neutral because it allows some pathways to benefit from offset accounting but not others. A recent ICCT paper highlighted this issue by demonstrating the excessive policy value of avoided-methane hydrogen pathways under the LCFS compared with a technologically advanced green hydrogen pathway with near-zero in-sector emissions. Under a $75-per-credit scenario, dairy-RNG hydrogen in California could receive $3.30 per kg in credits compared with only $1.40 for green hydrogen. Similar outcomes are expected when comparing RNG-based SAF production with more scalable advanced solutions like e-kerosene, which is already being pioneered in Washington State. If the provision in SB 5601 that overrides safeguards on avoided-methane offsets takes effect, CFS support for innovative transportation technologies like e-kerosene could instead be diverted to pathways that rely on avoided-methane offsets.

Second, avoided-methane offsets can endanger the stability of a fuels program by disrupting the balance between the supply and demand of credits. This happens because offsets can enable deeply negative carbon intensity values that lead to a decoupling of credit generation from the supply of fuel. In other words, credits would be generated not from displacing fossil fuel, but from crediting changes in manure management practices at farms across the country. As shown in the figure, credit generation from dairy digester/animal waste compressed natural gas in the LCFS rapidly outpaced fuel volumes. In the second quarter of 2024, dairy and swine RNG generated 20% of program credits while making up only 3% of the alternative fuel used in California. This oversupply has contributed to a growing credit bank and declining LCFS credit values.

With credit values in the Washington CFS already declining to $22.93 per MT in January 2025, an influx of methane-offset-supported, negative-carbon-intensity RNG pathways would drive the price down further. This could severely damage the CFS’s ability to support in-sector emission reductions. In particular, low credit prices could stymie any CFS support for zero-emission vehicles and charging infrastructure aligned with Washington’s ambitious Clean Vehicles Program. This support is especially critical now that federal support for zero-emission vehicle adoption and charging infrastructure deployment is in question.

Allowing avoided-methane offsets without restrictions is all risk and no reward. It has the perverse effect of providing greater incentives to pathways that have less impact on in-sector emissions. If any language in SB 5601 serves to prevent or delay the implementation of the proposed safeguards, this would be the likely, unfortunate outcome.

This piece originally appeared in Punjab Kesari in Hindi.

For many reasons, Haryana is the automobile hub of India. Its electric vehicle (EV) policy, which began in 2022, marked a significant step toward reducing transportation emissions. Now more than 2 years into the 5-year policy, with the Government of India having released the Production Linked Incentive (PLI) scheme for the National Programme on Advance Chemistry Cell Battery Storage and the PM Electric Drive Revolution in Innovative Vehicle Enhancement (PM E-DRIVE) scheme, there’s a prime opportunity for Haryana’s new government to make strides in promoting EV adoption, particularly for electric cars.

Here are four areas where extra focus could help maximize the potential for success:

1.  Grow the charging infrastructure network. While Haryana’s EV policy promotes setting up charging points in designated urban areas, implementation has been relatively sluggish. For drivers of electric cars in particular, public charging stations are needed in cities and along major highways to make them feel most confident. This is a learning from regions with the highest EV adoption rates, and one example is Norway’s successful model, which ensures charging stations every 50 km on main roads. Norway has one of the world’s highest ratios of chargers to vehicles with 30 public chargers per thousand electric cars and vans. A focus on standardized public charging stations compatible with various EV models and on installing fast chargers would reduce time that drivers spend waiting for a charger, particularly in high-traffic areas, parking lots, and commercial hubs. As we outlined here, charging infrastructure standardization is crucial because it reduces investment costs through economies of scale and significantly improves user experience.

In addition, Haryana can complement Central Government funding available for charging infrastructure in PM E-DRIVE with its own financial incentives for installing home and workplace chargers. Norway’s experience was highlighted at our India Clean Transportation Summit 2024, where Markus Nilsen Rotevatn from the Norwegian EV Association explained that a suite of policies have combined to make EVs in Norway so cost-effective that consumers are choosing them for that reason alone.

2. State manufacturing and research and development (R&D) initiatives for EVs. Haryana’s many strategic advantages—proximity to key markets, robust road infrastructure that provides reliable connectivity to other parts of India, dedicated EV parks, and skilled manufacturing workforce—mean it’s well positioned to become an EV manufacturing hub. The government can offer financial incentives to attract investment from local and global EV manufacturers, battery producers, and component suppliers. One avenue is special economic zones (SEZs) for EV production, which are designated areas that provide benefits like tax exemptions, streamlined customs processes, and access to superior infrastructure. These zones can enhance productivity, reduce operational costs, create job opportunities, and contribute to economic development. In Haryana, such SEZs could be complemented by R&D centres that focus on advancing EV battery technology and cost-effective EV components through public-private partnerships with local universities and technical institutions.

3. Financial incentive structures. Though Haryana’s EV policy includes purchase incentives for electric two-wheelers, three-wheelers, and cars, registration fee waivers, and road tax exemptions, there are ways to expand the financial benefits. Taking cues from successful global models in the United States, the United Kingdom, and China, Haryana’s government could collaborate with financial institutions to offer low-interest loans for EV buyers and give them more time to repay EV loans. Additionally, the government could create a financial risk management fund from the State Transport Fund for Accelerating EVs and support banks that lend to middle-class buyers and fleet operators. This could be especially effective now, as interest rates are not low. A fixed percentage of the State’s Transport fund could be allocated to things like providing purchase subsidies, developing charging infrastructure, and electrifying public transportation. The fund can also be used to provide free parking or reduced tolls.

4. New regulatory frameworks and building codes. Following models from Europe, Haryana could consider introducing low-emission zones (LEZs) in pollution-heavy cities like Gurugram and Faridabad. LEZs are geographically defined areas where access restrictions are applied to polluting motorized vehicles. The importance of LEZs was highlighted recently in a convening organized jointly by the Government of Haryana Transport Department and the ICCT. The Haryana Pollution Control Board mentioned LEZs in its Winter Action Plan 2024–25, but action on the ground has yet to commence. Updating building codes to require that new residential and commercial buildings be EV-ready and mandating that government departments transition to battery electric vehicles within a specified time frame are other ways to support the market.

Several supplementary measures would also support these priorities. From public-awareness campaigns that leverage multiple channels including television, social media, and community events, to educational programs in technical institutions that focus on EV technology and a robust battery recycling infrastructure with appropriate regulations, such measures work together to create a supportive ecosystem that enables widespread EV adoption.

Delivering on the vision in Haryana’s EV policy is expected to generate substantial environmental and economic benefits, including significant reduction in vehicular emissions, improved air quality across urban centres and avoided premature deaths through reduced air pollution, job creation across the EV value chain, and the positioning of Haryana as a competitive EV manufacturing hub in North India. The state EV policy complements the National Electric Mobility Mission Plan’s goal of 30% EV penetration by 2030 and strengthens India’s commitment under the Paris Agreement to reduce emissions intensity by 45% by 2030. While this agenda is ambitious, the long-term benefits to public health, employment, and economic growth make this transition not just desirable but imperative for Haryana’s sustainable future.

This piece was originally published in the Hindustan Times.

Road traffic congestion is a pressing issue in many of India’s metropolitan centres. Gridlock brings prolonged commute times, excessive fuel consumption, air and noise pollution, and elevated greenhouse gas emissions. The National Capital Region has been in the spotlight as traffic has worsened with urban sprawl. According to research published by the International Council on Clean Transportation (ICCT), on-road vehicles were responsible for nearly three-quarters of the transportation health burden in New Delhi in 2015.

To address peak-hour congestion, Delhi’s government reportedly plans to introduce a pilot congestion tax that would charge drivers who use select roadways during busy periods. Also known as congestion pricing, this aims to ease traffic and reduce pollution by discouraging unnecessary trips and encouraging drivers to use alternative routes, travel at off-peak times, shift to public transport, or share rides (and fees) with others. A 2010 study by the ICCT found that congestion tax schemes in London, Singapore, and Stockholm reduced congestion by 13%–30% and greenhouse gas emissions by 15%–20%.

This isn’t the first time Delhi has considered congestion pricing. Proposals in 2009 and 2018 failed to advance. Still, as Delhi looks ahead to its congestion tax pilot, I’ll highlight experiences from other cities that can provide valuable insights into how these schemes could be employed to effectively reduce traffic and air pollution.

Dynamic pricing

Delhi’s pilot would reportedly charge vehicles entering the city at 13 major entry points during morning and evening peak hours. With over 1.1 million vehicles entering and exiting daily, this makes sense, as such corridors are often heavily congested. A 2016 Centre for Science and Environment (CSE) cross-border traffic survey at nine major entry points to Delhi accounting for about 70% of traffic into the city found that the number of personal and passenger cars and two-wheelers entering daily was about the same as the number of vehicles registered in the city in a year.

At the same time, with over 1,800 new vehicles added to the Capital’s roads daily, an entry-point congestion tax during peak hours could miss an opportunity to address a large portion of daily vehicle emissions. Another CSE study estimated that the traffic at surveyed border points contributed just 10% of the total pollution loads emanating from the transport sector in Delhi. Administering taxes only at peak hours can also mean overlooking emissions during off-peak times, including those from heavy-duty vehicles, which are responsible for 20%–30% of transport sector pollution in Delhi and operate predominately outside of peak hours.

Other countries have sought to balance pollution and emission reduction aims against commuter access through dynamic pricing schemes that apply city-wide and have fees that rise at times of high congestion and drop during less busy times. In Singapore, an early pioneer in congestion pricing, charges are regularly reviewed and adjusted in response to changes in traffic patterns. Rates vary throughout the day and rise and fall gradually around periods of high traffic, which helps avoid surges before and after the designated peak hours.

Targeting the most polluting vehicles

Delhi reportedly plans to impose charges on most vehicles but exempt two-wheelers and electric vehicles. Congestion pricing programs in other countries have also provided discounts or exemptions for certain travelers, such as for residents of the designated taxation area, diplomatic vehicles, and emergency vehicles.

However, in Delhi, discounts and exemptions for any personal or commercial vehicle may risk undermining the core congestion and emission reduction aims of the schemes. For instance, two-wheelers, with reportedly about 1,100 new registrations  each day,  are roughly one in three vehicles on the road and are the second-largest contributor to transport pollution, according to The Energy and Resources Institute. Lessons can also be drawn from Delhi’s own 2016 odd-even scheme, which aimed to reduce pollution by restricting the operation of vehicles based on license plate number and exempted two-wheelers, women-only vehicles, and taxis, among others. Observers assessed that the program had minimal impact on pollution due in part to an increase in the use of exempted vehicles.

Pricing framework

Policymakers in other countries have wrestled with how to set congestion charges high enough to encourage reductions in vehicle use without placing a disproportionate financial burden on low-income travelers. In the 1970s, Singapore’s congestion toll led to a larger-than-expected drop in traffic that raised commuter welfare concerns. More recently, London revised its fee upward to maintain effectiveness in response to inflation.

There are other strategies. Currently, pricing in Singapore and Milan’s Area C varies by vehicle size and heavier, more polluting vehicles pay higher charges than lighter ones. This reflects their greater impact on both traffic congestion and pollution levels. Remote sensing, a method used to monitor real-world tailpipe emissions, could offer support for tailoring congestion prices to the emissions of different vehicles. This technology has been deployed in Europe, the United States, Spain, Sweden, and elsewhere to identify high- and low-emission vehicles and detect possible vehicle tampering. A recent ICCT study that took measurements via remote sensing in Delhi and Gurugram highlighted the difference between real-world tailpipe emission levels and laboratory limits and the need for advanced techniques for emissions monitoring.

A review of congestion pricing pilot programs in U.S. cities identified a number of possible approaches to mitigate the impacts of these schemes on low-income groups, including discounts, exemptions, and rebates. Such measures aim to minimize the financial burden on disadvantaged communities while maintaining the program’s effectiveness. Additionally, cities like Bogotá (Colombia) have adopted approaches that consider drivers’ income level alongside vehicle emissions to establish an equitable pricing structure.

The role of public transportation and supportive policies

Delhi has more than 7,500 buses in operation and over 390 km of metro connectivity, including links to other major cities. Still, challenges persist, including irregular bus frequency, overcrowding during rush hours, poor conditions of the bus, and last-mile connectivity issues for metro users. Ensuring that the public transit system is reliable, well-integrated, and equipped for last-mile connectivity through feeder bus services and pedestrian and cycling infrastructure is critical to realizing the shift away from private transport envisioned under congestion tax schemes. Indeed, congestion pricing was also considered recently in Bangalore and Mumbai, but it stalled due to concerns about the capacity of the public transport system to provide sustainable alternatives to private vehicle users.

Other cities have used revenues from congestion pricing to pay for upgrades to the public transit system. In London, the net revenue from congestion pricing has supported efforts to enhance bus fleets, expand bicycle and pedestrian lanes, improve road safety, and more. Cities like London, Paris, and Brussels have implemented scrappage programs that provide subsidies to retire older, higher-emitting vehicles and encourage a shift to public transit or cleaner private vehicles. Furthermore, initiatives like Delhi’s Mohalla bus scheme, a feeder bus service designed for neighbourhood-level operations, are expected to bridge the last-mile connectivity challenges by deploying 9 m zero-emission buses at scale.

In considering congestion taxing to help address poor air quality, Delhi has the opportunity to draw on global insights and establish a strong precedent for tackling traffic congestion and air pollution together. Success in this would promote sustainable urban mobility that offers a safer, healthier environment for its residents.

A recent report by the North American Council for Freight Efficiency (NACFE) highlighted the role of natural gas as a transport fuel and estimated that the greenhouse gas (GHG) emission savings from a natural gas engine are in the range of 13%–18% compared with diesel fuel. However, NACFE “focused most [its] discussion on the tank-to-wheels effects of the alternate fuels” in comparing a natural gas-powered truck with a diesel truck doing the same route. An analysis of the complete fuel-cycle GHG emissions (i.e., well-to-wheel) would cover emissions associated with all the steps of producing, transporting, and consuming the natural gas and diesel used for those trucks. As I’ll show here, the emission impacts of the upstream natural gas supply chain complicate the climate benefits of using natural gas for trucks.

The primary issue is methane leakage. Natural gas is mostly methane (85%–90% by volume) and its production involves multiple steps during which methane could be released into the atmosphere through leaks and venting. This happens all along the supply chain and these upstream emissions are noteworthy because methane is a potent GHG.

Upstream methane emissions can be substantial and they’re not easy to estimate. For example, using ground-based measurements validated by aircraft observations, researchers have estimated that methane emissions from the oil and natural gas (O&NG) industry are much higher than previously estimated by the U.S. Environmental Protection Agency (EPA). Methane emission estimates reported in EPA’s national GHG inventory are based on adding up the emissions from individual components of natural gas production equipment. Although this kind of bottom-up methodology provides detailed data from routine equipment behavior, it does not detect super-emitters, which can be unpredictable and can emit unusually large amounts of methane (one example is malfunctioning equipment). Alternate measurement approaches such as remote sensing of methane emissions via satellites or aerial surveys can help cover vast areas and detect these super-emitters, but such top-down emission estimates can also overestimate emissions. For instance, this technique might not be able to differentiate between O&NG sites and other sources of methane, such as landfills or dairy farms.

It’s also important to differentiate between emissions from combined O&NG production and emissions from producing just natural gas. For sites that produce both fuels, part of the methane emissions should be attributed to the oil produced alongside natural gas on an energy-weighted basis. The left column in Figure 1 illustrates the range of methane losses from O&NG production normalized by natural gas production using data from recent literature. These losses are calculated by dividing methane emissions by the amount of methane produced. The data from both bottom-up (e.g., EPA) and hybrid methodologies (i.e., a mix of bottom-up data and satellite or aerial surveys) were used for these estimates. The methane loss estimates in the right column in Figure 1 illustrate the emissions allocated solely to natural gas production, so they are allocation-adjusted loss rates. When the O&NG sector is considered, the methane loss rate ranges between 0.4% and 9.6%, with a mean of 3.4%. When losses are allocation adjusted, it ranges between 0.4% and 4.8%, with 1.8% as the mean.

Note: Methane emissions from O&NG production are from Alvarez et al. (2018), EPA (2024), and Sherwin et al. (2024). Methane emissions allocated to NG production are from Omara (2018) and Sherwin et al. (2024). 

To understand the climate impacts of upstream methane losses, let’s explore the fuel cycle GHG emissions of natural gas-powered heavy-duty trucks. Figure 2 illustrates the differences in well-to-wheel GHG emissions for 40-tonne trucks that run on compressed natural gas (CNG), normalized per mile, for each fuel option analyzed. We used the mean methane loss rate for natural gas production (1.8%) as well as the minimum (0.4%) and maximum (4.8%) loss rates from Figure 1 to provide the range of emissions estimates indicated by the error bar. The fuel economy of a heavy truck running on natural gas of 6.5 miles per diesel gallon equivalent was taken from the NACFE report. To compare our analysis with diesel-powered trucks, we used the U.S. national average for the carbon intensity of diesel fuel from the U.S. Renewable Fuel Standard, 91.9 g CO₂e/MJ. Non-CO₂ tailpipe emissions (methane and nitrous oxide) from GREET 2023 were included as equivalent amounts of CO₂ in the combustion emissions for diesel and natural gas-powered trucks. The system boundary for natural gas includes extraction, processing, transport, fuel refining and distribution, and methane leakage for all steps. As illustrated in Figure 2, with the mean methane emissions rate of 1.8%, our estimates are a 6% GHG emission savings from CNG trucks compared with diesel ones. However, the same estimate shows that if there is a methane leakage rate greater than 2.5%, that would make CNG trucks worse than diesel ones from a climate perspective.

Note: Fossil CNG results are estimated using GREET 2023 and assumptions therein for CNG production and combustion in dedicated CNG-fueled vehicles using a 100-year global warming potential for greenhouse gases. 

Thus, even with optimistic assumptions for upstream methane leakage, we estimate that CNG trucks only offer mild GHG reductions, if any, compared with petroleum diesel. This means that the estimated GHG savings for switching to natural gas trucks are marginal at best. However, there is also a long-term problem: Purchasing natural gas trucks may create technology lock-in. The CNG trucks purchased today and in the next several years could be on the road well into the 2030s, when zero-emission vehicles that provide much larger emission benefits could be more widely available. Battery electric trucks using grid-average electricity already generate deeper GHG savings than CNG trucks in many regions, and these GHG savings will grow over time as the grid decarbonizes. Adopting CNG could mean foregoing substantial GHG savings in the future from zero-emission vehicles.

Durante los últimos años hemos observado un rápido aumento de proyectos de transporte público cero emisiones en América Latina. Santiago cuenta actualmente con 2.480 buses eléctricos y ha anunciado planes de sumar 1.200 más en 2025, mientras que Bogotá ha decidido permitir solo buses cero emisiones a su sistema de autobús de tránsito rápido (BRT, de sus siglas en inglés) a partir de 2022 y ya tiene 1.486 buses eléctricos operativos. Aun así, incluso con más de 6.000 autobuses en operación en América Latina, los pilotos siguen siendo importantes para el aprendizaje.

El Consejo Internacional de Transporte Público (ICCT), a través de la iniciativa Zero Emission Bus Rapid-deployment Accelerator (ZEBRA), acompaño la realización de dos pilotos en el sistema de transporte de Medellín entre febrero y mayo de 2023. Estos pilotos fueron realizados en rutas barriales operadas por transportadores tradicionales, que presentan mayores retos y barreras de implementación que los sistemas de transporte concesionados tipo BRT. Se dio apoyo técnico a las empresas Flota Nueva Villa (FNV) y Expreso Campo Valdés (ECV), las cuales operan el en sector nororiental de Medellín, para realizar pilotos en tres rutas con longitudes entre los 12-14 km y con pendientes altas, cercanas al 25% en algunas zonas.

Los pilotos cubrieron toda la gama de actividades necesarias para comenzar a operar buses eléctricos. En términos de infraestructura, se solicitó disponibilidad de electricidad a la empresa de energía e instaló un cargador para los buses. Se realizaron pruebas de campo de la flota para garantizar el desempeño adecuado del bus, se capacitaron los operadores en como conducir para mejorar el desempeño energético del bus y se definieron los planes de operación para garantizar la autonomía del bus eléctrico en cada ruta seleccionada. Al final, los buses eléctricos cumplieron con las expectativas y funcionaron sin contratiempos.

Encontramos que los pilotos siguen siendo fundamentales para abordar tres tipos de cuestiones que son claves en el escalamiento de servicios de buses eléctricos: consideraciones tecnológicas, organizacionales y regulatorias.

Desde el punto de vista tecnológico, se observa que los mayores cambios que acompañan la transición a los autobuses eléctricos ocurren en la planificación de la operación y el mantenimiento, que están directamente relacionados con el uso del nuevo sistema de propulsión. De esta manera, los pilotos permiten validar la capacidad de baterías requeridas para los vehículos, la potencia de los buses, el diseño de las carrocerías y los costos reales de operación y mantenimiento. Adicionalmente, para el sistema de carga es posible identificar el tipo y potencia de cargador requerido y su concordancia con los planes de carga necesarios para cumplir con la programación de despachos de los buses.

En cuanto a la organización, los pilotos muestran brechas donde se puede requerir habilidades, personal o sistemas de gestión adicionales para cumplir los planes operacionales. Como resultado de la implementación del piloto es posible implementar programas de capacitación y o proponer cambios organizacionales para poder hacer efectiva la implementación de la electromovilidad en las empresas.

Finalmente, en términos de regulación, los pilotos ayuden a identificar las homologaciones, permisos y ajustes contractuales necesarios para implementar los proyectos de autobuses eléctricos, que de otra manera pueden producir riesgos de implementación inviabilizando o retrasando los cronogramas inicialmente previstos. Con los pilotos, las rutas criticas desde el punto de vista regulatorio y contractual pueden ser identificadas y priorizadas para reducir costos y tiempos de implementación.

De esta manera, los pilotos permiten entender mejor los aspectos técnicos, legales y financieros necesarios para establecer sistemas de autobuses eléctricos y detectar y abordar brechas en las interacciones entre autoridades, transportadores, fabricantes de flota y proveedores de energía que pueden retrasar la implementación. Esto puede ser especialmente útil en sistemas de transporte en los cuales la adopción de tecnologías cero emisiones y regulaciones relacionadas con ellos hayan sufrido un rezago que dificulte los cambios en la infraestructura y en las organizaciones necesarios para la implementación de la electromovilidad.

En este contexto, para los tomadores de decisiones responsables para el diseño de sistemas de transporte público, los pilotos pueden servir como una herramienta útil y un ejercicio orientador, ya sea como una fase previa a la estructuración a detalle o como una fase temprana en la implementación. Esto puede ayudar a respaldar la implementación exitosa de proyectos de buses eléctricos y generar la confianza que todos los actores requieren para dar este importante salto hacia la sostenibilidad ambiental.

The climate impacts of aviation are increasingly coming into focus. Following sharp traffic reductions due to the COVID-19 pandemic, greenhouse gas (GHG) emissions from airlines are expected to exceed 2019 levels this year. Recognizing the need to reduce emissions in line with the Paris Agreement, in 2022 aircraft manufacturers agreed to support the aviation industry’s goal of net-zero carbon dioxide (CO₂) emissions in 2050.

Achieving that goal will require a gargantuan effort by stakeholders including airlines, fuel providers, and aircraft manufacturers, and an estimated US$4 trillion in new investments in clean fuels and planes for international flights alone. Moreover, according to our research, starting around 2035, all new subsonic aircraft would need to be zero-emission throughout their operating lifetimes.

That’s sobering, especially given how rare new aircraft types are today. Beyond work to certify Boeing’s widebody 777X, none of the “big three” western commercial manufacturers (Airbus, Boeing, and Embraer) have announced plans to certify new aircraft types before 2035. And only new types hold the potential for substantial improvements in fuel efficiency and, potentially, the shift to zero-carbon fuels like hydrogen.

But one manufacturer, Boom Supersonic, seems unbothered by the huge effort that’s needed. Boom just completed the eighth test flight of its one-third scale XB-1 demonstration aircraft. Boom aims to break the sound barrier by the end of the year, en route to bringing its Mach Number 1.7 aircraft, Overture, into service by 2029. They argue that supersonic aircraft “are twice as fast so it’s also going to decarbonise twice as fast.” But how does that square with flight physics and a net-zero carbon budget?

Due to technological advances since Concorde was developed in the 1960s, it’s expected that Overture will be more fuel efficient than the jet-fuel-guzzling Concorde aircraft that flew in the 1980s and 1990s. But subsonic aircraft have improved over time, too, and today’s advanced widebody aircraft like the Boeing 787 and Airbus A350 burn 30% less per seat km than the B747-400 aircraft that shared the skies with Concorde.

Due to Overture’s high speed, small size and therefore poor economy of scale, small payload capacity, and limited range (it requires refueling stops on longer flights), it’ll inevitably burn more fuel per seat than competing subsonic widebodies. According to Boom, a seat on Overture will consume two to three times more fuel than business class seating on today’s widebodies, and seven to 10 times more fuel than an economy seat. Because CO₂ emissions scale with fossil fuel burn, supersonics will have a disproportionately high climate impact.

Boom points to the promise of sustainable aviation fuels (SAFs) to address these emissions. SAFs are alternative jet fuels produced from biological or renewable feedstocks that can have lower life-cycle emissions than conventional jet fuel. But SAFs remain scarce (just 0.2% of fuel supply in 2023), expensive (generally quoted as two to five times higher than fossil jet fuel costs), and they come with sustainability concerns of their own.

So, if Overture successfully makes it to market, what would that mean for a net-zero carbon budget? I ran the numbers using the approach from last summer’s paper with Supraja Kumar, namely, to estimate the GHG emissions associated with new aircraft deliveries throughout their operating lifetimes. I started by assuming that Boom will deliver 1,000 of its Overture aircraft by 2050; this is 33 aircraft produced annually at its Overture Superfactory in Greensboro, North Carolina, starting in 2029, and then a doubling of annual production via a second production line in 2042.

Drawing on previous modeling that we did with MIT, I assume that an average Overture flight burns 44 tonnes of jet fuel over a typical flight of 3,800 km and operates at an average speed of 1,350 km per hour (approximately MN 1.27 at 50,000 ft). That’s 75% of design cruise speed, which is the average for subsonic aircraft in our recent paper, after accounting for time spent in the slower takeoff, climb, descent, and landing phases of flight.

Each Overture is assumed to operate as a typical widebody subsonic aircraft, meaning that it flies an average of 2,900 hours per year over its typical lifetime of 25–30 years. I ran two cases to bound the range of uncertainty on future SAF use: a business-as-usual (No SAF) case and a Maximum SAF case that assumes ReFuelEU Aviation levels of SAF globally through 2050. That’s equivalent to the European Union’s ambitious SAF mandate, which will require 70% SAF supply at EU airports in 2050, but implemented globally. This is an aggressive assumption, given that SAF mandates are still in their infancy outside of Europe.

The results are frankly startling. Beginning in 2029, 1 year of Overture deliveries would emit between 113 and 155 million tonnes (Mt) of CO₂ over their lifetimes in the Maximum and No SAF cases, respectively. To put those numbers in perspective, in 2022, the entire country of Chile emitted 137 Mt of GHGs. That means Overture deliveries alone would be responsible for a GHG footprint equal to the fifth largest economy in South America, home to nearly 20 million people. Lifetime emissions from a year of deliveries are estimated to rise to between 128 Mt (Max SAF) and 310 Mt (No SAF) CO₂ by 2050. That’s equivalent to about 40% of the emissions from Airbus deliveries in 2023, and would be from a manufacturer building less than one-tenth as many aircraft.

How do these emissions relate to aviation’s remaining net-zero carbon budget? The figure below shows cumulative lifetime emissions from Overture deliveries under the No SAF (blue) and Maximum SAF (red) cases. Absolute CO₂ in billion tonnes (Gt) is shown at left and the share of aviation’s remaining net-zero budget is shown at right. I estimate that Overture deliveries through 2050 would emit between 2.4 and 4.8 Gt of CO₂ over their lifetimes. That’s between about one-quarter and one-half of aviation’s remaining 9.4 Gt net-zero carbon budget.

Figure. Cumulative CO₂ emissions (left) and share of a net-zero aviation carbon budget (right) from Overture aircraft by delivery year and scenario

This means that a single startup manufacturer could consume at least one-quarter of aviation’s remaining net-zero carbon budget through 2050. That leaves much less available for conventional aircraft to sip the SAF that Overture would gulp. And remember, if Boom’s estimate of Overture’s fuel burn per seat is correct, one gallon of SAF burned in a subsonic plane would provide 6.6 times more passenger kilometers of travel than on Overture.

So, in our carbon-constrained world, there’s reason to think the return of supersonic aircraft will be double the trouble, not twice as nice.

This piece was originally published in The Hindu Business Line. 

 The post-Diwali air quality index (AQI) is being widely discussed in newspaper reports, and with the exception of 2022, the day after Diwali 2024 had the lowest 24-hour average AQI for that day since 2015. In the last 2–3 months, Delhi enjoyed its best air quality of the year and once saw an AQI close to 53. It was similar at this time last year, when Delhi had a few months of good AQI and clear skies. This is all the result of multiple initiatives by agencies, including the environment and transport departments of the Government of Delhi, the Commission for Air Quality Management, and more.  

This article intends to look at some the transport-specific initiatives, including the Delhi Electric Vehicles policy, which was released in August 2020 and is currently extended till March 2025. This was a major milestone in the city’s strategy to combat air quality issues. Indeed, the city has over time created and executed several actions to improve air quality, and one of the key strategies has been electrification of the transport sector. As Delhi paves its way towards EV policy 2.0, let’s look at its electrification journey through the lens of public transport service improvement. 

Delhi’s EV policy set a 50% electrification target for new public transport vehicles and covered new stage-carriage buses procured for the city’s fleet, including for last-mile connectivity services. 

The transition to electric started with public buses, and in a significant move under the Faster Adoption and Manufacturing of Electric Vehicles (FAME) II scheme, Delhi procured and deployed 400 electric buses (e-buses) in 2022 at a competitive rate of ₹43/km. These buses have now been operational for over 2 years and each 12 m e-bus can operate for 120 km on a single charge, which contributes to a significant reduction in carbon footprint. A study estimated that replacing Delhi’s entire existing bus fleet with new e-buses could reduce total pollutant emissions by nearly 75%.

In addition to deploying e-buses, the Delhi Government floated tenders for e-scooter and e-cycle adoption in January 2024, to diversify the transport options available in the city. Additionally, pursuant to an initiative focusing on gender equity introduced in April 2022, the Delhi Government issued permits for 3,500 e-autos and 500 of these were earmarked for female-driven e-autos. Training programs for female drivers are underway and interdepartmental coordination is helping to streamline the process of bringing onboard women-owned e-autos.

Building infrastructure

Delhi’s commitment to building infrastructure for electric vehicles is also evident in the efforts of Delhi Transco, which issued tenders to set up charging and battery-swapping facilities across the city. Companies like Sun Mobility have already begun setting up these facilities and users are given subsidized rates, to help ensure the affordability and accessibility of e-mobility solutions. Another outcome of these tenders is that, in collaboration with the Delhi Metro Rail Corporation and the Transport Department, Sun Mobility has launched three-wheeler-e-rickshaw services to improve last-mile connectivity.

Public transport services that operate at high frequency and on shorter routes are needed. A major initiative is the Mohalla bus scheme, which was formulated to create neighbourhood-level connectivity using the e-bus fleet. The e-buses procured under the Mohalla bus scheme are set to be deployed soon.

Even though Delhi’s EV policy envisioned only 50% of all new stage-carriage procurement to be electric, all buses deployed by the Delhi Government since January 2024 are electric. This year alone, from January to August 2024, 595 e-buses were deployed in Delhi. Delhi’s efforts to promote electric mobility not only improve sustainability but also offer long-term economic and health benefits by reducing fuel costs and improving air quality for residents. 

Supporting the deployment of electric vehicle (EV) chargers is a critical part of vehicle electrification efforts around the world, including in Indonesia. Leveraging our study assessing charging infrastructure needs for electric cars in the country in 2030, the ICCT recently undertook new analysis to support Indonesia’s Just Energy Transition Partnership in developing the 2024 Comprehensive Investment and Policy Plan. We’ve teamed up with the Energy Efficiency and Electrification Working Group under the leadership of the Net Zero World Initiative, and as part of this, extended our 2030 charging infrastructure projections to estimate needs in Indonesia in 2035.

In short, pushing for greater adoption of home charging will be crucial for reducing government expenditure on public chargers. Let’s go through the basic elements first and then we’ll detail how we arrived at this.

For EVs, there are private chargers and public chargers. In our updated analysis to 2035, we categorize chargers located in single-family homes and vehicle depots as private chargers. The costs of installing private chargers are borne by individuals or companies. Under the category of public chargers are public destination, en-route, workplace, and public residential chargers. (In our earlier study, public residential was not included. However, as more and more chargers are being installed in residential complexes and apartment buildings in Indonesia, our analysis to 2035 includes public residential.) Although the funds for public charging infrastructure are usually provided by the government, regulation in Indonesia allows private actors to invest.

There are also two primary charger types in Indonesia: Level 2 and direct current fast charging (DCFC). The capacities of Level 2 chargers range from 7 kW to 22 kW, and these are mostly used for home, depot, public destination, workplace, and public residential charging. DCFC capacities in Indonesia range from 25 kW to 200 kW and these can fully charge an electric car in 20–60 minutes; DCFC is often used for en-route and public destination charging.

Table 1 details the results of our assessment of charging needs to 2035, for which we considered three scenarios of home charging adoption, 60%, 70%, and 80%. Under a scenario where 80% of EV owners have home charging, we estimate that 71,647 public chargers would be needed, and these would cost approximately Rp. 15.4 trillion (US$964 million) by 2035. The need for public chargers is greater when there is less home charging, and with adoption rates of 70% and 60%, it would require 93,876 public chargers and 116,112 public chargers, respectively. The total investment needed could be as high as Rp. 21.2 trillion (US$1.33 billion) under the 60% scenario and around Rp. 18.3 trillion (US$1.15 billion) for the 70% scenario.

Table 1. Total chargers (units) needed by 2035 under 60%, 70%, and 80% home charger adoption

As you can see from the table, public charging infrastructure is dominated by public destination and public residential. The public residential chargers are Level 2 chargers in residential complexes, and they’re used most often as a substitute for a private home charger. Note, too, that by 2035, Level 2 chargers are projected to be approximately 78% of all chargers across Indonesia. For DCFC chargers, these would be required in large numbers for en-route applications—99% of the 6,184 en-route chargers estimated to be needed by 2035. This all helps illuminate the expected needs in various locations for both government and private stakeholders involved in deployment.

We map the number of chargers that we estimate will be needed in each province in Figure 1. In 2035, around 64% of all chargers are projected to be in the top five provinces by number of chargers: DKI Jakarta, Jawa Barat, Jawa Timur, Jawa Tengah, and Sumatra Utara. This is aligned with our projections for total the stock of electric cars in 2035, as most of the electric cars are expected to be in those provinces.

Figure 1. Distribution of public chargers for electric cars in Indonesia under the ICCT’s 80% home charging share scenario

Note: This map is presented without prejudice to the status of or sovereignty over any territory, the delimitation of international frontiers and boundaries, and the name of any territory, city, or area.

A recent survey showed that EV users in Indonesia prefer to charge their vehicles (two-wheelers and cars) at home because they mostly use their EVs for short-distance trips. Similar preferences are seen in many other regions, and that’s why our estimates show that as home charger adoption increases, the need for public charging infrastructure decreases. Because of this, pushing for more home charger adoption would help minimize the amount of state budget needed for public charging infrastructure.

Mendukung perluasan adopsi pengisi daya kendaraan listrik merupakan bagian penting dalam program elektrifikasi transportasi di seluruh dunia, termasuk di Indonesia. Memanfaatkan studi awal tentang perhitungan kebutuhan infrastruktur pengisian daya untuk kendaraan listrik roda empat di Indonesia pada tahun 2030, ICCT malakukan analisis baru untuk mendukung Just Energy Transition Partnership yang sedang menyusun Comprehensive Investment and Policy Plan untuk tahun 2024. ICCT bekerja sama dengan Efficiency Energy and Electrification Working Group dibawah kepemimpinan the Net Zero World Initiative, untuk memperluas proyeksi infrastruktur pengisian daya pada 2030 dari studi sebelumnya dan memperkirakan kebutuhan infrastruktur pengisian daya di Indonesia untuk tahun 2035.

Jika dijelaskan secara singkat, hasil studi menunjukkan bahwa dengan mendorong penggunaan home charger yang lebih luas, hal tersebut berperan penting dalam mengurangi investasi yang harus dikeluarkan oleh pemerintah untuk perluasan SPKLU. Berikut kami jelaskan elemen-elemen dasar terlebih dahulu, lalu kemudian menjelaskan bagaimana kami sampai pada kesimpulan diatas.

Bagi kendaraan listrik, terdapat dua lokasi pengisi daya, yakni pribadi dan publik/umum (SPKLU). Di analisa terbaru kami untuk tahun 2035, kami mengkategorikan pengisi daya yang terletak di rumah dan depo kendaraan sebagai pengisi daya pribadi. Biaya pemasangan pengisi daya pribadi ditanggung oleh individu atau perusahaan. Sementara itu, untuk kategori pengisi daya umum, atau yang biasa dikenal SPKLU, dibedakan menjadi SPKLU di tempat umum, SPKLU di jalan raya, SPKLU di gedung perkantoran, dan SPKLU di komplek perumahan atau apartemen. (Dalam studi kami sebelumnya, SPKLU di komplek apartmen atau perumahan tidak masuk dalam perhitungan. Namun, karena semakin banyak SPKLU yang dipasang di kompleks perumahan dan apartemen di Indonesia, analisis kami terbaru untuk tahun 2035 menghitung SPKLU di lokasi tersebut.) Umumnya, biaya investasi untuk SPKLU biasanya disediakan oleh pemerintah, namun regulasi di Indonesia memungkinkan pelaku swasta untuk berinvestasi.

Terdapat juga dua jenis pengisi daya di Indonesia: Level 2 dan direct current fast charging (DCFC). Kapasitas pengisi daya Level 2 berkisar antara 7 kW hingga 22 kW, dan sebagian besar digunakan di rumah, depo, tempat umum, gedung perkantoran, dan komplek perumahan atau apartemen. Kapasitas DCFC di Indonesia berkisar antara 25 kW hingga 200 kW dan dapat mengisi penuh kendaraan listrik roda empat dalam waktu 20–60 menit; DCFC sering digunakan untuk pengisian daya di jalan raya dan tempat umum.

Tabel 1 merinci hasil perhitungan kami terhadap kebutuhan pengisian daya hingga tahun 2035, yang mana kami mempertimbangkan tiga skenario adopsi home charger (60%, 70%, dan 80%). Dalam skenario di mana 80% pemilik kendaraan listrik roda empat memiliki home charger, kami memperkirakan sekitar 71.647 charger SPKLU akan dibutuhkan, dan ini akan menelan biaya sekitar Rp. 15,4 triliun (US$964 juta) hingga tahun 2035. Kebutuhan SPKLU akan lebih besar ketika home charger lebih sedikit, dengan tingkat adopsi 70% dan 60%, diperlukan masing-masing 93.876 charger SPKLU dan 116.112 charger SPKLU. Total investasi yang dibutuhkan dapat mencapai Rp. 21,2 triliun (US$1,33 miliar) pada skenario 60% dan sekitar Rp. 18,3 triliun (US$1,15 miliar) pada skenario 70%.

Tabel 1. Jumlah charger (unit) yang dibutuhkan pada tahun 2035 sesuai adopsi home charger 60%, 70%, dan 80%

Seperti yang dapat dilihat dari table diatas, infrastruktur pengisian daya publik didominasi oleh SPKLU di tempat umum dan di komplek perumahan atau apartemen. SPKLU di komplek perumahan atau apartemen adalah pengisi daya Level 2 dan paling sering digunakan sebagai pengganti home charger. Perhatikan juga bahwa pada tahun 2035, pengisi daya Level 2 diproyeksikan berjumlah sekitar 78% dari semua pengisi daya di seluruh Indonesia. Untuk pengisi daya DCFC, pengisi daya ini akan diperlukan dalam jumlah besar untuk SPKLU di jalan raya— dimana 99% dari total 6.184 charger SPKLU di jalan raya yang akan dibutuhkan pada tahun 2035. Temuan tersebut dapat membantu mengarahkan kebutuhan SPKLU di berbagai lokasi bagi pemangku kepentingan (pemerintah dan swasta) yang terlibat dalam pengembangan SPKLU.

Kami memetakan jumlah charger SPKLU yang akan dibutuhkan di setiap provinsi pada Gambar 1. Pada tahun 2035, berdasarkan perhitungan jumlah charger SPKLU, sekitar 64% dari semua charger SPKLU diproyeksikan berada di lima provinsi berikut: DKI Jakarta, Jawa Barat, Jawa Timur, Jawa Tengah, dan Sumatra Utara. Hal ini sejalan dengan proyeksi kami untuk jumlah kendaraan listrik roda empat pada tahun 2035, karena sebagian besar kendaraan listrik roda empat diperkirakan berada di provinsi tersebut.

Gambar 1. Distribusi SPKLU untuk kendaraan listrik roda empat di Indonesia berdasarkan skenario home charger 80% dari ICCT

Catatan: Peta ini ditampilkan tanpa praanggapan terhadap status atau kedaulatan wilayah manapun, penetapan batas internasional, dan nama wilayah, kota, atau area manapun.

Survei terkini menunjukkan bahwa pengguna kendaraan listrik di Indonesia lebih suka mengisi daya kendaraan mereka (baik kendaraan roda dua dan roda empat) di rumah karena sebagian besar dari mereka menggunakan kendaraan listrik untuk perjalanan jarak pendek. Preferensi serupa terlihat di banyak wilayah lain, dan itulah sebabnya perkiraan kami menunjukkan bahwa seiring dengan meningkatnya adopsi home charger, kebutuhan SPKLU akan menurun. Oleh karena itu, mendorong lebih banyak adopsi home charger akan membantu meminimalisir jumlah anggaran negara yang dibutuhkan untuk perluasan infrastruktur SPKLU. 

Although inherently challenging, the quantification of vehicle emissions has evolved considerably in recent decades and now extends well beyond the original lab-based measurements. Here we’ll explain a new development in the field from the University of York and the International Council on Clean Transportation, which partnered to create a technique that simplifies point sampling, an approach to measuring on-road emissions. We find that it can be adopted widely—by any city seeking to better understand transport emissions—and provides valuable new information about how much different vehicles are contributing to ambient air pollution.

The need for such a technique arises from the challenges inherent in measuring vehicle emissions: Millions of individual sources of emissions move in space and time and come from numerous generations of fuel, vehicle, and aftertreatment technologies. There are also environmental influences such as ambient temperature and road gradient.

One inescapable requirement is that numerous vehicles should be measured to achieve a representative sample and ensure that robust conclusions can be drawn from the data. This is especially true when characterizing the emissions of individual vehicle manufacturers or even specific vehicle models. Use of remote sensing technology is an attractive way to measure emissions from vehicles operating in real-world conditions because it records exhaust emissions of passing vehicles by shooting lights across vehicle exhaust plumes to measure the light absorptions of pollutants of interest. The TRUE Initiative uses such techniques extensively in many cities around the world.

While remote sensing has many advantages for measuring common pollutants such as nitrogen oxide, nitrogen dioxide (NO₂), and carbon monoxide, it’s not as well suited to measuring other pollutants in vehicle exhausts. Individual hydrocarbons that have harmful health impacts, including benzene and toluene, are typically not available, for instance, and neither are particulate metrics like particle number (PN) and black carbon (BC).

An alternative unobtrusive approach to measuring on-road emissions from traffic is point sampling, a technique where fast response instruments located curbside measure the dispersing plumes of passing vehicles. With point sampling, pollutants are extracted from the plume and rerouted to analyzers. Point sampling allows users to expand the number of measurable pollutants by using dedicated instruments that specialize in specific gaseous and particulate pollutants. As carbon dioxide (CO₂) is measured simultaneously with the air pollutants of interest, pollutant ratios can be determined (such as nitrogen oxides [NO_x]/CO₂) and from these, different emission factors can be calculated.

That said, point sampling brings its own challenges. For most roadside locations, individual vehicles are not conveniently separated from one another to allow individual plumes to be accurately measured as the vehicle passes; this can easily result in data loss of over 70%. A quiet location with low vehicle traffic is necessary, but simultaneously not very useful for achieving a large sample size. Conversely, a busier location quickly runs into the problem of overlapping plumes that mix with each other.

To find another way of approaching this problem, we developed an adapted analysis approach that generates disaggregated vehicle emissions information from data with plume overlap. Figure 1 shows an example of vehicle passes at a location in York (UK) over a 15-minute period. It’s clear there is no period where a single plume exists in isolation from others. The new analysis technique uses regression to relate roadside concentrations of different pollutants to the amount of plume that’s expected on average. Each time a vehicle of a particular type passes (denoted by the colors), an average plume profile is virtually added to the time series. The new technique is called plume regression and it not only greatly simplifies point sampling, but also provides valuable new information. The methodology behind plume regression is described in more detail in a paper published in Environmental Science & Technology earlier this month.

Figure 1. A 15-minute period of vehicle passes made at a location in York, with the vertical lines on the x-axis showing the time a vehicle passes the point sampling instruments

We applied this plume regression approach to several contrasting data sets and pollutants, including NO_x, NO₂, and ammonia in York, and NO_x, PN, BC, and 10 individual volatile organic compounds (VOCs) in Milan as part of the CARES project. We compared the NO_x emission factors derived from the plume regression with remote sensing data, and they showed very good agreement. Figure 2 shows an example of fuel-specific emission factors for NO_x from around 24,000 measurements in Milan. These results reflect the expected emission differences across fuel types and the reduction in emissions from older to newer Euro emission standards.

Figure 2. Fuel-specific NO_x emission factors (g/kg) based on the plume regression approach using data from the CARES project in Milan

In addition to providing emission factors, the new plume regression approach provides valuable information on concentration source apportionment, or how much of the pollutant concentration measured at the roadside is coming from different types of vehicles. For example, vehicle emission measurements alone cannot tell us how much of measured NO₂ at the roadside can be attributed to Euro 5 diesel cars. That requires more advanced air quality modeling to predict near-road concentrations, and it’s a challenging task in complex urban environments.

The information from the plume regression approach is highly valuable to those interested in reducing the roadside concentrations of important air pollutants. An example from Milan is shown in Figure 3, and the area of each rectangle represents the contribution made to roadside NO_x concentrations by different fuels and vehicle technologies. Observe that the bulk of NO_x is from diesel vehicles (blue) and a much smaller contribution is from gasoline (green), LPG (yellow), and CNG (purple). The major contribution is from diesel pre-RDE Euro 6 passenger cars and Euro 5 passenger cars; this is due to both their number and high real-world emissions.

Figure 3. Absolute concentration contribution to roadside NO_x at a roadside location in Milan, and the size of each area shows the total contribution to NO_x concentrations by fuel and vehicle types

This new plume regression approach could be widely adopted around the world. It’s basically the same as the ambient measurements already made at thousands of roadside sites that provide hourly pollution concentrations, but uses fast response instruments and adds a measure of CO₂, the byproduct of vehicle fuel combustion. Because of this, point sampling combined with the plume regression approach can enhance the existing capability of roadside monitoring sites. By quantifying vehicle emissions and estimating how much different vehicles are contributing to ambient air pollution concentration, the new method unlocks a large potential for cities to better understand transport emissions and develop data-driven policies to reduce one of the main sources of air pollution.

We are grateful to Naomi Farren and Sam Wilson for carrying out the measurements and to Kaylin Lee and Mallery Crowe for co-authoring the publication for Environmental Science & Technology. We also thank Ricardo for supporting the Ph.D. of Sam Wilson and Markus Knoll at the Technical University Graz and for sharing additional measurements from the Milan CARES campaign.