Transportation department converts 8 more buses to compressed natural gas, equivalent to taking 35 cars off roads per year
The Eagle County School District will soon have nearly half its school bus fleet running on a renewable energy source.
On Wednesday, the school board approved converting an additional eight buses, on top of six already converted, to a system that burns renewable compressed natural gas, rather than diesel.
Together, the 14 buses would lead to annual carbon dioxide emissions savings of 168 metric tons of carbon dioxide, equivalent to removing 35 cars from the road.
"We think that this is really the best system for us, and it really accomplishes both the money savings and being conscious of our carbon footprint," said Christof Abraham, the district's director of transportation during Wednesday's school board meeting.
Compressed natural gas is made by compressing natural gas to less than 1% of its volume at standard atmospheric pressure, producing a cleaner energy source than gasoline or diesel. The renewable compressed natural gas the school district's buses run on, through a system from the company Demi Diesel Displacer, is even more climate friendly because it is made from cow manure.
"It's an even more eco-friendly version of compressed natural gas, where it's actually refined from cattle and refined into a compressed natural gas," Abraham said.
The process of making the renewable natural gas involves capturing and cleaning up the biogas from cow waste to make it usable as a fuel source. The gas is then delivered by Black Hills Energy through fuel lines to the district's fueling pumps. It takes each bus about six hours on the fueling line to refuel.
The Demi renewable natural gas system is a displacement system. It introduces compressed natural gas into the bus engine's combustion chamber to offset the amount of diesel that needs to be used, Abraham said.
This minimizes the amount of diesel fuel the bus needs to run. Renewable natural gas itself has a near zero emissions factor, allowing the bus to run more cleanly.
The school district selected compressed natural gas over other renewable energy technology options because of Eagle County's "unique environment," Abraham said. "Hot and cold, mountain passes, the altitude and the length of many of our routes."
Electric vehicles have "range limitations, reliability issues, also massive costs" in procuring the buses and the accompanying charging technology, Abraham said. They also tend to struggle in cold temperatures. "That was not a viable application for our particular school district."
Propane-powered buses were also an option, as the cost is similar to diesel buses, but they have reliability issues because they use a diesel motor without diesel fuel, a lubricant. It is also difficult to get pure propane fuel, Abraham said.
The Demi renewable natural gas system the transportation department selected is "a happy medium," Abraham said.
Last year, the district converted six school buses to renewable natural gas.
"They're very easy to maintain, minimal cost to up fit the buses, and we've had a very good experience with them so far," Abraham said.
The district's existing diesel buses can be "up fit" with the renewable natural gas system, meaning there is no need to purchase new vehicles. The alternative fuel source does not affect the range or the power of the buses. And so far, the system has proven to be extremely reliable.
In both the electric and propane buses, "if any system on the bus fails, the bus does not move," Abraham said. The Demi renewable natural gas system is separate from the bus' diesel system, so if the natural gas system were to fail, it can be shut off and the bus can revert to diesel power to get to its destination.
The compressed gas form also makes the fuel "resistant to gelling" in the cold, Abraham said. "We had more issues with our early formulation of diesel than we have ever (had) with renewable natural gas."
The renewable natural gas also saves the school district money.
The six buses currently operating have provided the district with a daily savings of about $70. The buses ran throughout 2024, with an annual savings of $12,000.
Adding the eight buses approved on Wednesday, the 14 total buses are projected to save the district nearly $30,000 over the course of a year.
The total cost of up fitting the 14 buses and installing the fueling systems costs the district $147,000 total. The funds for the purchase will be supplied from ballot measure 5B, approved by voters in November 2023 allowing the district to increase its debt by $100 million to support investments like transportation and employee housing.
Abraham said he expects the district to break even on the investment in a little over four years.
The district's entire fleet contains 35 buses. While there are others that may be converted at a later date, 14 have been selected for renewable natural gas thus far because, due to limited drivers, the district does not always run all 35 vehicles.
"This is a conservative number to make sure that it is being utilized every day," Abraham said. "This 14 will really round out our 'route' buses."