The domestic alternative fuel: LPG
By Allen Penticoff
[dropcap]When[/dropcap] I first began the Mr. Green Car column, I did a series of reports on alternative fuels. These included: diesel; biodiesel; vegetable oil; compressed natural gas; ethanol; hydrogen; electricity; and even compressed air among others.
Somehow, I missed reporting on one alternative fuel that has been around a long time and has proven benefits but is little used in the United States as a transportation fuel: liquid petroleum gas (LPG).
Most of us know it by the name propane – that cooks our steaks on the grill or heats our homes if we live in rural areas. There are other LPG flammable liquids going by other names and they are sometimes mixed into the fuel. particularly butane.
LPG is really a waste byproduct of natural gas production and the gasoline refining process. It has been around and used for many purposes since the dawn of the petroleum energy age. In 1910 a process was developed to liquefy these gases, and a second method using compression was developed in 1912. Commercial use of LPG rapidly developed, including use in motor vehicles.
LPG turns from liquid to vapor at minus 44 degrees Fahrenheit. However, it will remain liquid under pressure with only 177 psi even at 100 degrees Fahrenheit. This is why the tank for your grill feels liquidy when you carry it, yet burns as a vapor upon release of the natural vapor pressure within the tank.
If released as a liquid, LPG instantly becomes a vapor in the atmosphere. As a consequence of this low pressure, the tanks needed to contain the liquid do not have to be built to withstand extremely high pressure – as do compressed natural gas (CNG) and hydrogen which remain gaseous. Due to this, the system is much less expensive to manufacture and adapt to vehicles.
In automotive use, LPG/propane is known as “autogas,” and in places that provide filling service for vehicles equipped to burn LPG you will see signs for “autogas” – even right here in Rockford at Menards.
There have been decades of conversion of gasoline burning engines to run on autogas. Very commonly used elsewhere in the world, autogas is the third most popular transportation fuel.
In the past, most systems relied on burning the vaporous gas, however newer systems use the LPG in liquid form via electronic fuel injectors directly into the engine. The older vaporous system may be set up to be “dual fuel” where either gasoline or LPG can be burned. Some systems even allow for an automatic switch over when higher power is needed. The direct injection LPG systems are less likely to be dual fuel, and they also provide more power under all circumstance than the vaporous systems.
What got me interested in LPG is that I went on a tour of the Kobussen Buses facility in Brodhead, Wisconsin. While on the tour, driver trainer Michael Lowery mentioned that some of the buses were set up to operate on propane. That of course prompted questions on my part.
Kobussen Buses is contracted with many Wisconsin communities to provide school bus service. They also have small bus charter service. Presently they have 542 buses, 95 of which operate on propane; the rest operate on diesel. The LPG buses were purchased already converted and none of them are “dual fuel.”
An LPG bus costs about $8,000 more to acquire than a standard diesel bus. All LPG buses use large “gasoline” type engines (diesel engines do not convert to LPG readily). An LPG bus will get about 4 miles per gallon while a diesel bus sees 7 mpg.
Compressed natural gas is cheaper to purchase as a fuel but the conversion is far more expensive. Presently at the Brodhead facility, their propane supplier fills the buses but they will have their own filling capabilities by end of summer 2017. With such large purchases of propane, they are getting the fuel for $1.20 per gallon (versus a bit over $2 per gallon retail) so that is 30 cents-per-mile on LPG. Presently they buy diesel for $2.45 per gallon – yielding 35 cents per mile. This adds up savings quickly for the kind of miles these buses roll daily.
According to Dan Kobussen, vice president and owner of this family business – and their Brodhead maintenance chief, Travis Shrader – the reduced maintenance costs of the LPG buses also adds to their cost efficiency. One instance is the LPG buses use only 7 quarts of oil per change (and it is quite clean when changed) versus 20 quarts for a diesel bus.
Other savings are in the form of not needing DEF liquids or replacing carbon trap filters. Also, no electricity is needed to keep the engines warm ready for start up. LPG buses don’t sit around idling, consuming fuel and polluting the air in school zones or terminals.
Lowery first reported to me that they love the propane buses because no pre-heat or warm up period is needed. The LPG buses fire right up on the coldest mornings and quickly rise to a higher operating temperature compared to a diesel bus. This also makes for a more comfortable cabin for the driver and passengers.
“As a driver, I love how quiet the propane fueled bus is compared with a diesel,” Lowery said. “The loudest thing on the bus is the turn signal. This allows me to better hear traffic and emergency vehicles, so I can react quicker – making my trip safer for my passengers. Also, with this new quieter environment, I can hear every kid on my bus and be involved in their conversations. My kids love it too!”
Lowery also reports that refueling is only a little slower than filling with diesel, easy, safe and clean. All drivers are trained to do their own refueling.
Kobussen adds to that, “Propane helps Kobussen reduce our costs which we pass onto our school districts and it burns cleaner which helps our precious cargo breathe easier.”
As an alternative fuel, propane releases nearly as much carbon dioxide as burning gasoline (15 percent less CO2) but it lacks many of the organic compounds that gasoline and diesel fuels contain and pump into our atmosphere unburned. Not as clean as CNG, it still is far better for the environment than conventional fuels, and LPG is nearly all domestically produced in the U.S. and Canada.