Alternative Transport Fuels : Let’s Clean the Smokescreen

Manoj Pandey*

The provocation for this article is many social media comments claiming that electric vehicles are totally pollution-free,  or stating that total replacement of petrol and diesel with ethanol is the only way out of vehicular pollution, and also wondering why hydrogen is not being used yet as vehicle fuel, and so on. It looks that people are influenced, sometimes in the wrong direction, by data and statements served out of context. What make the topic even more topical are some recent studies on emissions from alternate fuels, and the Indian government’s renewed push to ethanol blending in petroleum fuels.

Let us start with some straight facts about alternative fuels. In short, ethanol and electricity are the two main alternative fuels being used in large quantities in many countries. Biodiesel is in use in some situations. Natural gas and petroleum gas (LNG, LPG, CNG, etc) have become so mainstream, these are no longer alternative fuels. Others are yet in experimental stages or being used in very small quantities.

Road transport is one of the main polluters. Vehicles keep polluting the environment from their production to operation, maintenance and disposal. The main culprit is the fossil fuels used in the vehicles; the gases produced in combustion (=burning) in vehicle engines produce pollutants and – worse –  the main gas, carbon dioxide, is a greenhouse gas – one that lead to rise in atmospheric temperature and consequent climate change.

Since road vehicles are the main mode of transport in almost all countries, they contribute significantly to pollution and greenhouse gas emission. Take the example of India, where –

  • 18% of the total energy is consumed by the transport sector, and road vehicles are a major part of it;
  • 97% of road vehicles still run on petrol or diesel;
  • transport sector produces about 142 million tonnes of carbon dioxide, which is approximately 14 per cent of the country’s energy-related carbon dioxide emissions. Out of it, 123 million tonnes is contributed by road transport segment.

This all makes road transport the third-biggest contributor of greenhouse gases in India.   

Internal combustion engine and associated technology

The bulk of the petroleum fuel consists of a number of complex carbon compounds (=hydrocarbons), while some nitrogen and sulphur compounds are also present in traces.

In the present technology, the engine (called internal combustion engine) aims at burning the complex carbon compounds into simple end products (carbon dioxide and water). However, the technology is far from perfect. As this burning is not complete, it leads to many half-broken compounds leaking into the atmosphere. Besides, only a part of the energy generated during combustion translates into wheel movement. As there are mechanical parts that convert the energy first to linear movement of pistons in the engine and then into rotating motion for running the wheels, a large part of energy is wasted and a good deal of mechanical wear and tear takes place. 

The harm caused to the environment by the internal combustion engine depends a lot on the fuel used. Diesel has more particulate matter as compared to petrol, while petrol produces more carbon dioxide for the same unit of fuel.

Carbon dioxide is the main product of combustion. It is a non-polluting gas but is a greenhouse gas and because it is produced in huge quantities by millions of vehicles on the road, it is responsible for much of the rise in atmospheric temperature in recent years. The nitrogen and sulphur compounds present in petrol and diesel, when oxidized during combustion, produce oxides, which also are greenhouse gases and pollutants. Compounds that do not fully burn give rise to smoke. Though the problem of incomplete burning has been reduced to a good extent of late by additional refining and use of some additives, it remains an issue in poor countries due to use of old vehicles, improper maintenance of vehicles, contamination during transportation of fuels, etc. The break-down of complex hydrocarbons also results in the production of carbon monoxide, which is a highly toxic gas.

Natural gas: a clean fuel?

You must have noticed the green colour painted all over gas stations and on gas-driven vehicles? That paints the gas as a green, environment friendly fuel. Gases used in vehicles as fuel are cleaner than petrol and diesel, but fossil fuels they are.

The most used form of gas in the transportation sector is CNG or compressed natural gas. For bulk transportation and storage, LNG (which is natural gas compressed into liquid) is preferred. LPG (liquefied petroleum gas) is also used in vehicles but is not as popular.

Natural gas wins over petrol and diesel in these respects:

  • CNG engine’s maintenance costs are low.
  • There is no risk of evaporation or leakage from the vehicle’s storage tank because it is sealed.
  • It causes less pollution: does not have lead (lead additives are mixed in petroleum fuels), and has negligible amounts or no particulates and nitrogen / sulphur pollutants. Overall, the CNG engine produces 20-30% less greenhouse gases and about 95% less pollutants than petrol and diesel.

Owing to its economic advantages (more than its being clean), natural gas has become a popular transport fuel in many countries. Governments have been promoting it in a big way because it is available in large quantities, is less costly as it does not need refining (as compared to crude), and is easy to transport in bulk. These economic advantages, supported by environmental considerations, make it an ideal fuel in the eyes of governments, especially when no cleaner and cheaper fuels are available. As it costs less to customers and does not require major design changes in existing vehicles, it is lapped up by commercial users. 

But what is not well-known is that it is the push from petroleum companies themselves that has made CNG popular at the cost of more promising fuels. We shall discuss that in a while but, before that, let us examine its green claim a bit more closely.

CNG is chemically methane, a greenhouse gas that is 80 times more potent as a greenhouse gas than carbon dioxide. The gas does leak during exploration, transport and handling. These quantities may not be too large, but they should count when we assess one fuel against others.

CNG is a fossil fuel. It is abundant but not renewable. Its reserves are not present in all countries, and many countries do not own the exploration and extraction technologies. So, gas economy is almost as exploitative as crude economy.

Though the tailpipe emission (=emission coming out of engine exhaust pipe) from CNG is much cleaner than that from petrol and diesel, its contribution towards greenhouse effect is only slightly less.

Big petroleum multinationals have been lobbying in national and international fora and with national governments to support natural gas as a clean, commercially viable fuel. Their lobbies are supposed to have led to compromises in energy/ environmental policies being adopted worldwide. They use all means to influence legislators, policy makers and people at large. Election funding and employing government servants are two direct ways they are reported to be compromising policy formulation and implementation at top levels. They are also supported by governments of nations and provinces (e.g. States in the US) that have huge natural gas reserves. In pursuing their vested interest, they often bring forth the interests of people employed by or dependent on the petroleum and gas industry. In recent years, they have been spending huge sums on social media campaigns for moulding public opinion.

Since the petroleum/ CNG companies could not directly argue against clean non-fossil fuels, they started promoting natural gas a viable bridge fuel till other clean fuels became commercially viable. This argument is supposed to have greatly influenced the global environment policy in the recent times. Opponents of natural gas argue that popularization of this fuel disincentivizes commercial adoption of cleaner fuels while releasing as much greenhouse gases as petroleum fuels. They also tell, indiscreet funding by public financing bodies (e.g. massive financing by ADB for developing natural gas infrastructure in Asia) is hurting the adoption of better technologies and fuels.

Biofuels: an alternate fuel with great promise?

Biofuels are fuels obtained from biological entities – seeds and fruits, living tissues, and dead biological matter.

The most popular biofuel is ethanol (which is the key ingredient of alcoholic drinks). When it is mixed in small quantities with petroleum fuels, no change is needed at all in the engine of vehicles produced in the last two decades. However, for a higher ratio of ethanol blending, some adjustments need to be made, and newer vehicles are being produced with such a provision.

Brazil was the first to introduce ethanol-mixing in petrol and diesel. As of today, it is also the country with the highest level of mandatory ethanol blending. 

The percentage of ethanol mixing in petrol and diesel is indicated by its E value; for example, E10 petrol has ten percent ethanol. Modern vehicles need no change up to this level of ethanol blending. In Brazil, the mandatory alcohol mixing for vehicles is 18-25 percent, and a good number of flexible fuel vehicles in Brazil run on 100% ethanol (=E100). In the US, most petrol is E10 while vehicles up to E85 are also in use. Many other countries, especially in Europe, use E10 blending levels.

In India, the present ethanol mixing level is 8%, which is to be increased to 10% by the next year and 20% by 2025 according to the roadmap released by the government last month. 

There are significant advantages of use of ethanol as a transport fuel:

  • Ethanol is a renewable fuel, as most of it is produced by fermentation of sugar or starch (drawn in raw form from sugarcane or corn). There are also efforts to make ethanol from cellulose (drawn from grasses and crop residues) and algae, but these methods are not yet commercially viable.  
  • Ethanol breaks down into carbon dioxide and water, thus has no particulate matter, chemical additives, complex carbon compounds, carbon monoxide or nitrous/ sulphur oxides. Thus, it causes no pollution during combustion. 
  • As said earlier, ethanol blending up to a certain level does not need change in engine technology. Thus, it does not put any additional economic burden either on manufacturers or users.
  • Ethanol can be locally produced and does not need costly imports and refining infrastructure. It suits developing countries, most of which have tropical or sub-tropical climate, are net petroleum importers. Their climate is good for growing corn and sugarcane and for fermentation.

But is ethanol that innocent a fuel?

No. It, too, has a dirty tail.

Ethanol may be a cleaner fuel than petrol and diesel in terms of local pollution (particulate matter, complex carbon compounds, etc) but it produces just a little lower amount of carbon dioxide per unit of energy as compared to petrol and diesel. Fermentation of raw material itself emits a good deal of carbon dioxide. 

The crops grown for ethanol production need a large area, fertilizers, plant-protection chemicals and water. This can add up to a huge environmental cost. It becomes worse in regions where water is not abundantly available (e.g. Punjab, Haryana and western UP in India, where wheat-rice-sugarcane cropping has depleted water levels to unsustainably low levels, besides damaging soil health).

There is a big debate on the use of food crops for biofuels. For example, corn, sugarcane, sugar beet and sorghum are used for human and animal consumption. Large-scale diversion of these crops/ cropping areas for producing biofuels when a big global population is underfed raises the issue of food vs fuel. Many see such diversion as anti-poor and unjust. 

A notion seems widespread that during their lifecycle, biofuel crops absorb large quantities of carbon dioxide and thus net carbon emission from biofuels is zero. This argument has merit only when we compare biofuels with fossil fuels. In real terms, the notion is misconceived because these crops replace more environment friendly crops such as fodder crops that could have been grown in the same land. If crop diversion is not to take place, more forests need to be cut to grow these additional crops.

Even in economic terms, the balance of costs and benefits in the use of ethanol as transport fuel depends on dozens of factors including feedstock used, land-use change for growing these crops, additional irrigation requirement, transportation cost, and technology used for extraction of alcohol. In the US, where corn is used for producing ethanol, the total energy saving is very low as compared to Brazil where sugarcane is used for producing alcohol. In India, molasses (a by-product in sugar production) is being primarily used for ethanol production, which makes ethanol cheaper than petrol and diesel but not by a big margin.

All things considered, use of biofuels, especially ethanol, is at present a tempting proposition for countries dependent on import of costly fossil fuels. 

Electric vehicles: the last resort?

Electricity is another source of energy being promoted worldwide in transportation. Many governments including the US, China, the EU and India are shifting from fossil fuel to electricity in public transportation, and they also give incentives to industry and users for fast adoption of electrical vehicles.

Electricity is dubbed as the cleanest among the available vehicle fuels. Before arriving at a conclusion, please look at some relevant facts:

  • Electric vehicles (EVs) do not cause any emission of gases from the vehicle. 
  • The cost of production and transport of electricity is less as compared to other fuels, when compared in terms of cost per unit distance covered by the vehicle.
  • Running cost of electrical vehicles is lower than that for petrol and diesel vehicles.
  • Electric vehicles are less prone to wear and tear as there is no complex mechanical transmission from the engine to wheels. It reduces the cost of maintenance.
  • EVs are less noisy.
  • EVs are easier to drive because they do not have a gear system.
  • As electricity grids are becoming more efficient and cleaner, because of improvement in technology and with the introduction of more renewable energy, EVs are turning that much cleaner.

But if you thought that EVs do not emit greenhouse gases or cause pollution, you are mistaken. Total greenhouse gas emission in the lifecycle of EVs is less than their petrol and diesel counterparts only after they have run a minimum distance. In a recent study based on a model that calculates lifetime emission of vehicles, the negative environmental impact of the latest Tesla electric car was found to be higher than a comparable regular car when driven for less than 21,725 km, mainly due to batteries. After that, the gain kept improving. The study model took into account hundreds of parameters to measure lifecycle emissions. Depending on different factors, the break-even point at which carbon emission from EVs starts becoming less than petroleum fuel vehicles can be as big as 40,000 km.

Having said that, let me add that considering the likely advances in various technologies in the next 10-15 years, EVs are likely to keep getting cleaner ahead of whatever gains the advancements in mainstream internal combustion technology bring about. A July 2021 study across many countries found that “emissions over the lifetime , of average medium-size BEVs registered today are already lower than comparable gasoline [=petrol] cars by 66%–69% in Europe, 60%–68% in the United States, 37%–45% in China, and 19%–34% in India.” The study projects that electric cars registered in the coming years will have hugely improved lifetime emission levels. (In India, the difference is less because production of internal combustion vehicles is less carbon-guzzling than in other countries while electricity production emits more carbon as it is mostly coal-based.)

Adoption of EVs: a slow process yet

So, as on today, electric mobility is the clear winner in terms of greenhouse gas emissions and pollution. Let us do a quick fact-check on the status and recent developments in this area.

  • Governments the world over have been giving incentives for wide-scale adoption of EVs. Emerging nations are far behind the developed ones but even in the latter, the adoption of EVs is rather slow.
  • India has lagged behind many other countries in adoption of EVs in a big way. However, the central government, followed by some state governments, has woken up to the reality of continued dependence on fossil fuels and the urgency to adopt clean technology to meet climate commitments. It is projected by NITI Ayog that with government incentives, promotion and lowering costs, about 40% sales of buses, 50% of cars and 60% of two-wheelers sold in India by 2030 will be electricity driven.
  • Electric vehicles need a different technology unlike CNG and biofuel vehicles (which require no or minor change in the existing engine design). This needs big investments and technology transfer.
  • At present, EVs are costlier than comparable fossil fuel vehicles, their batteries need to be charged after a short run, and they cannot run beyond city hubs without a charging infrastructure. Batteries used in electric vehicles can cause pollution and their disposal is a big environmental issue. 
  • Of all disincentives in fast adoption of EVs, the biggest one – for users – is the high acquisition cost of EVs. Prices are coming down mostly because of subsidies and tax benefits provided by the governments. As technology grows and EVs are mass-produced, the costs are likely to come down on their own. It is projected that starting 2025, EVs will start becoming cheaper than fossil fuel vehicles in many countries.
  • Batteries are the biggest polluting component in EVs. They are also heavy and, therefore, reduce mileage. They need to be charged frequently and replaced after their efficiency goes below about 70%. In this area too, developments are taking place at a fast pace. Starting with lead batteries, now the majority of batteries used in EVs are Lithium-ion batteries. Battery costs are dropping at 10% a year for some years, leading to lower operational costs of EVs. The shift in battery technology is towards solid-state Lithium batteries and Nickel-Cobalt-Manganese batteries. These batteries have advantages such as better charge holding capacity, light weight, and higher life. With adoption of these batteries, the mileage as well as frequency of charging vehicles will further improve.
  • One big hindrance in mass-production of EV batteries in countries such as India is non-availability of Lithium. This metal is being commercially extracted in only a handful of countries. From India’s point of view, aluminium fuel batteries are a promising technology because India has copious aluminium reserves, and Al-fuel batteries are not toxic like lithium ones and can drive 1000 km in one charge.
  • Battery disposal can cause a big challenge once EVs are adopted on a large scale. New batteries with higher capacity and re-purposing of batteries after their efficiency goes down look promising solutions.
  • The charging infrastructure is another big bottleneck in adoption of EVs. Governments, electricity companies and vehicle companies are developing fast-charging infrastructure in major cities in many countries. More battery capacity and the option of home charging for light motor vehicles and two-wheelers are other recent developments that will support the adoption of EVs.
  • Cities such as Los Angeles, Oslo, San Francisco and Beijing have embraced EVs in a big way. In Liuzhou in China, smaller cars that are inexpensive and can be charged at home, have become a big hit. Some experts see this becoming a worldwide trend in the coming years.
  • EV technology itself is becoming more efficient. New EVs can run long distances per charge by converting energy more efficiently and using light-weight batteries. Hybrid car technology uses the conventional internal combustion technology and harnesses part of energy in charging the batteries.
  • As the grid electricity gets cleaner (with the introduction of clean energy sources in electricity generation), the lifecycle greenhouse gas emission from EVs will come down to that extent.

Other alternative fuels

Experiments with different types of alternative fuels including cellulosic ethanol (ethanol produced from crop and wood residues), edible oils, butanol (a biofuel produced, like ethanol, by fermentation of biomass, it has some advantages over ethanol), dimethyl ether (a fuel usually obtained from natural gas as a clean substitute for diesel), biomethane (e.g. gobar gas or biogas), hydrogen, compressed air, nuclear energy and solar energy have been conducted for decades. Some have good potential because of low emissions and/or abundant supply. However, they have not yet become commercially viable. Some, such as biodiesel (produced from edible oils, animal fat and grease) have met with some success, but locally. Hydrogen cell technology looks highly promising but is as yet commercially unviable. The search for newer solutions continues.

The verdict

No vehicle fuel is without environmental cost, not even the best available alternative fuel. Of all fuels that are in use, electricity is the cleanest (in terms of pollution as well as emission of greenhouse gases) followed by ethanol and petroleum gases.


In this article I tried to defog the claims of cleanliness of alternative fuels, especially CNG which is touted as a green fuel. Taking the discussion further, let me emphasize that no source of energy for driving vehicles – even solar panels or Hydrogen cells – can be so clean that its production and distribution also do not emit greenhouse gases or cause pollution.

Clean fuels are an important component of climate action but they are just one of many. Technology needs even more attention. The highest attention needs to be given to overarching solutions in mobility sector – solutions that environmentalists harp on but governments and public overlook. For example, if a community decides to use human powered vehicles or to walk for their daily chores, that can result in more carbon saving than what the least polluting motorized vehicle can do.

That was a rather simplistic example. I am aware that such interventions can be local and small-scale, and difficult to implement, especially in developing, aspirational, countries. But there are many others that are doable and must be prioritized even more than looking for clean fuels. Incentivising and supporting public transportation, incentivising tech-upgradation, proper disposal of transport waste, and efficient management of government vehicles are some low hanging fruits that can give good results.

Since nobody – neither governments, nor political parties, nor companies, nor individuals –will be prepared to sacrifice their present for the sake of a cleaner future, whatever tech and fuel has potential of reducing greenhouse gases and pollution needs to be promoted. The rising demand for vehicular transport, especially in countries/ regions that are yet under-served, does not allow governments to subsidise and promote new technology and new fuels beyond a point. Within this reality too, policy makers can have a long-term vision. For example, they can limit the promotion of CNG to replacing petroleum fuels and not promote it so much that it becomes a hindrance in the adoption of cleaner technologies. If biofuels are to remain a major ingredient of fuel-mix, stress should be on using other plant materials than corn and sugar for producing ethanol. More hardy crops, grasses, crop residues, wood waste, spoiled foodgrain, algae, etc have shown promise, and can become better sources of ethanol if big push is given to R&D in this field.

Further reading


*Manoj Pandey is a former civil servant. He does not like to call himself a rationalist, but insists on scrutiny of apparent myths as well as what are supposed to be immutable scientific facts. He maintains a personal blog, Th_ink

Disclaimer: The views expressed in this article are the personal opinion of the author and do not reflect the views of which does not assume any responsibility for the same.


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