Getty Images
In Fulton County, Georgia, students have been getting to school a little differently recently – even if they may not realize it.
The county has rolled out hundreds of propane buses to take kids to school, switching over from previously-used diesel. Across the United States, school districts are becoming increasingly interested in making the switch after recent studies concluded that polluting diesel buses are having an effect on students’ health.
A study released last month by West Virginia University concluded that air pollution emissions from propane school buses are significantly lower than those from diesel buses. The differences are particularly large because school buses stop and go so often. For such stop-and-go routes, emissions of nitrogen oxides (NOx) were 34 times lower for propane than for diesel buses. On city and highway roads, these air pollution emissions were 15 to 19 times lower.
Carbon emissions were 13% lower than for diesel buses on the stop-and-go routes, according to the study commissioned by the Propane Education and Research Council. However though the air pollution benefits are relatively clear, research on the carbon emission benefits of propane versus petrol gasoline or diesel fuel is less conclusive.
The combustion of liquified petroleum gases (LPG) like propane is more complete and efficient than gasoline or diesel, which means that the amount of carbon monoxide and hydrocarbons is far less. The emission from the tailpipe of an LPG engine are mostly just carbon dioxide and water. It emits virtually no soot.
Despite the cleaner tail pipe emissions, LPG is rarely used as a transport fuel. When it is, it is generally referred to as autogas.
Globally, autogas makes up just 1% of transport fuels, compared to 51% for petrol gasoline and 41% for diesel. In the United States, the use of propane fuel in passenger cars is unheard of – its use is limited to utility vehicles like school buses. But increasingly people are asking – if it’s been deemed to be so beneficial for school buses, why not try it out on passenger cars?
The reasons more and more school systems have been switching their school bus fleets to propane have mostly been economic. Propane is a much denser fuel and therefor you need far less of it, saving school systems money. But the air pollution benefits are also becoming an increasingly attractive motivator. It isn’t just about helping the environment – there is now also data that being in cleaner buses can help students’ academic performance.
A study by Georgia State University published in July compared the standardized test scores of students in Georgia school districts based on what types of school buses they were taking every day. It found that the students riding in buses that emitted less air pollution had higher test scores. This, they theorized, was possibly the result of the students on the cleaner buses missing less days of school.
Global push
Most people around the world are unaware that LPGs like propane can be used as a transport fuel. But with concerns about both air pollution and carbon emissions at the forefront of the political agenda, the industry is asking itself how it can communicate the short-term benefits to the wider public.
At a global conference of the LPG industry in Amsterdam last week, the potential for LPG as a transport fuel was being hotly debated by attendees. Some saw it as the next big thing for LPG, while others viewed efforts to push it as a transport fuel as a waste of time.
The use of autogas varies widely by country. In some countries it is only used for trucks or farm equipment. In others it isn’t used at all. And in some countries, it’s fairly common for people to convert their engines to autogas because the fuel is cheaper to purchase but still widely available at gas stations. These countries include Turkey, Ukraine, Poland, Korea and Russia. In Ukraine, almost a quarter of vehicles run on autogas. Autogas can often have a stigma as the “poor man’s fuel” in these countries, because it is more widely used in rural areas.
But autogas is still a very niche product. The five countries listed above account for half of the autogas used in all vehicles worldwide. And though there is moderate use in other countries like Mexico, Italy, Japan and the Netherlands, it’s still just a drop in the bucket of fuel used globally.
“Most of the leading markets are in decline,” Trevor Morgan, an analyst with Menecom Consulting, told the Amsterdam conference. And while global autogas use is on a slight upward trajectory, the fuel seems to be competing in an unfriendly regulatory environment in most places.
“The enormous disparity in the success of autos in competing against gasoline and diesel is explained mainly by differences in government incentive policies,” he said. The biggest policy determinator is taxation. In the United States there is almost no tax incentive for using autogas, and it is therefor almost completely absent from the passenger car market and only used for utility vehicles like school buses.
But in countries like Spain, Thailand, Italy, Ukraine and the Netherlands the taxation level on autogas is less than half of that on diesel and gasoline. Its use in those countries is therefor much higher because there is an incentive for people to convert their engines – and the demand means that autogas is available at most refuelling stations.
The taxation makes a difference for how long it takes someone to break even after converting their engine – something that costs anywhere between $500 and $2,000. In Bulgaria, a person can break even after driving 14,000 kilometres. In Canada, it would take 100,000 kilometres. And in the United States, a person would basically never recoup their engine investment costs.
This lack of policy incentive represents a lost opportunity, Morgan said. Under a baseline scenario with current policies, autogas use will not significantly expand and will decline from 2030. But with modest adjustments to fuel taxes and stronger measures to discourage diesel for environmental reasons, the autogas fleet could double by 2040. This would, according to his research, result in a 4% reduction in global nitrogen oxides emissions, a 5% reduction in particulate matter emissions and savings of 130 million tonnes on well-to-wheel emissions of CO2 by 2040.
This would, he said, yield a benefit of €54 billion from social, economic and environmental benefits by 2040 from cleaner air.
Competing With Electric
Climate campaigners aren’t too keen on the LPG industry promoting itself as a solution to air pollution or climate change. Even if it does burn cleaner than petrol gasoline or diesel (an assertion they say needs more study), it’s still a fossil fuel and automakers should be focused on switching production to electric vehicles instead.
The environmental NGO Transport & Environment says governments should not be taxing gas fuels lower than petrol gasoline or diesel, because the advantages over these fuels is minimal when compared to electric. They have produced a study concluding that the lower carbon footprint of LNG doesn’t necessarily translate to fewer carbon emissions. “In reality poor gas engine efficiency often offsets the benefit of the fuel already at tailpipe level,” they concluded. “This points to the need for policies based on measured performance – through the EU’s official tests – not the type of fuel.”
The LPG industry counters that widespread e-mobility is still a long ways off and cannot be the only solution. Right now there are less electric cars than autogas cars – representing 0.2% of the global market. To focus only on electric would let the perfect be the enemy of the good.
“Electrification is a bit of a comfort blanket, policymakers are clinging to it as the silver bullet,” said James Rockall, head of the World LPG Association. Alternative fuels like LPG should be encouraged by policies at the same time, he said, because all solutions are needed.
The jury is still out on whether switching to autogas would help significantly in the fight against climate change, but the benefits for city air pollution are fairly conclusive. As the industry looks to position the fuel as a cleaner alternative, there are still voices that say electricity should be the main focus for engine conversion.
