Liquefied Petroleum Gas, or LPG, is a fuel consisting of a mixture of hydrocarbons, primarily propane and butane. It has been used for decades in a variety of applications, including as a cooking and heating fuel, as a refrigerant fluid in air conditioning systems and as a propellant in aerosol sprays. When it is used as a fuel for motor vehicles, it is sometimes known as autogas or, simply, as propane.
It is usually obtained by refining crude oil or wet natural gas. Wet natural gas is natural gas that contains an excessive proportion of propane, butane and other non-methane hydrocarbon molecules.
Propane is used in a variety of transport applications including light, medium and heavy-duty vehicles. Its availability and use vary by country. Some countries have promoted the use of propane as a motor fuel as a part of their energy policy. In Turkey, for example, nearly 40% of all passenger vehicles run on propane, according to the World LPG Association. Globally, it’s the third most used fuel, after gasoline and diesel.
Propane engines grant a set of environmental benefits to users. The main ones have been described in the next section.
Propane engines reduce Greenhouse Gas Emissions
Propane vehicles can have significantly lower well-to-wheels emissions than gasoline, fossil natural gas and diesel vehicles. Well-to-wheels emissions account for the emissions occurring as a result of the production, transportation and distribution of fuels. When comparing the Greenhouse Gas (GHG) emissions resulting from the use of different fuels, well-to-wheels emissions are a more meaningful metric than tailpipe emissions.
Unlike methane, the primary constituent of natural gas, propane is not a GHG. Leaks and other irregular releases during transportation and storage are included in any well-to-wheels accounting, but they make no contribution to global warming.
A study by the Gas Technology Institute found that school buses running on propane can generate 21% lower well-to-wheels GHG emissions compared to buses running on gasoline. They can also be 7% lower than diesel and 12% lower than compressed natural gas.
Biopropane has a role in decarbonization
Renewable feedstocks, like agricultural waste products, spent cooking oil and animal fats, can also be used to make propane. Biopropane is often co-produced along with biodiesel via complex chemical processes. Chemically, biopropane is nearly identical to propane obtained from fossil resources, so both fuels are interchangeable in many applications.
The use of biopropane can effectively minimize a vehicle’s carbon emissions like renewable natural gas or biodiesel. Compared to other biofuels, however, biopropane currently remains a niche-use fuel, which is produced in relatively small quantities and has limited availability. As the supply of biodiesel and bio jet fuel grows, so will the supply of renewable propane.
Propane engines reduce emissions from air pollutants
Modern propane engines produce extremely small amounts of NOx. Under certain driving conditions, such as low speed city driving, propane engines will generate less than 4% of the NOx that a comparable diesel engine would produce.
Propane engines also produce almost no soot – only 2% of a diesel engine’s – and very little carbon monoxide. All of these make propane vehicles intrinsically clean. They are an attractive option for businesses that are required to comply with strict emissions standards – such as California’s. Propane engines will also be a great option for those who wish to make a positive impact on the air quality in the communities they reside in.
Propane is not toxic to the environment
Unlike other petroleum fuels, propane is nontoxic and presents no risk of soil or water contamination. If propane is spilled or leaked outdoors, it will quickly vaporize and harmlessly dissipate into the atmosphere. This makes installing propane fueling stations easy and cost-effective. There’s no permitting required by the Environmental Protection Agency. It does not affect the ozone layer and, as stated, has very low global warming potential.
Propane may not be an environmental pollutant, but it is a hazardous substance. It is extremely flammable, and being heavier than air, propane vapours can accumulate into low lying areas. This is why propane vehicles are often not allowed to use underground car parks.
In summary, propane is a great option for clean, environmentally-friendly vehicles. Propane vehicles have extremely low emissions of air pollutants and substantially lower GHG emissions than other vehicles running on other fossil fuels. Propane is also nontoxic, is not a hazard to plant or animal life and will not contaminate the environment. It also delivers the power and range required for many commercial vehicle applications.
Puneet Singh Jhawar is the General Manager of Global Natural Gas Business, Cummins.
