Posted by: Francis Koster Published: March 28, 2011

School System Makes “Bio” Gas for its Bus Fleet

School System Makes "Bio" Gas for its Bus Fleet

by Francis P. Koster, Ed.D.

The Gaston County school system in North Carolina has developed a program to generate biodiesel for its bus fleet.  This program converts enough waste vegetable oil from the school cafeteria and other sources to fuel all of its buses.  By converting the buses to run on biodiesel, air pollution is reduced, money is saved, and jobs are secured. 

In 2005 the sixth largest school system in North Carolina began running its school buses on biodiesel generated by the school system.  

The first year of operation they were able to make 10,000 gallons of biodiesel.  Two years later their facility was producing 500 gallons per day. [10]   

Cost Savings and Pollution Control

The Gaston County school system is able to produce biodiesel for $0.60 per gallon.  The  buses travel 11,000 miles every day. 

Consequently the school system is able to save over $300,000 per year. [1] [2]

In addition to cost savings, the biodiesel program is an effective way of reducing air pollution.  Petroleum based diesel emits various types of pollutants when combusted including carbon monoxide, hydrocarbons, sulfur dioxide and toxic particulates.  These pollutants are linked to health problems such as cardiovascular disease, lung cancer and respiratory problems such as asthma.  Because exhaust fume concentrations inside school busses are typically 3 to 5 times higher than outside air it is important to reduce overall emissions however possible.

Little or no modification is needed for standard diesel engines to run on biodiesel.  In its pure form (called “B100”), biodiesel actually cleans the engine intake and fuel tank of buildup from petroleum based diesel use.  This led to an interesting discovery, for as the engine and tank is cleaned of lingering residue, the engine’s fuel filters may clog until the remaining old diesel fuel has been removed.  The Gaston County school buses encountered this clogging problem which caused some of the buses to break down.  This was traced to the fact that the biodiesel was cleaning the engines, resulting in a need for more frequent filter changes.  These cleaner engines required less frequent expensive maintanence.  After the filters were replaced more frequently, the engine problems ended.

Process Information and Issues Encountered

The school’s biodiesel is made from vegetable oil reclaimed from their cafeterias, local recycling centers, area restaurants and large manufacturers that produce waste oil.  Because the school system is a public institution, it has non-profit status which allows for corporate partners to make charitable donations of larger volumes of waste vegetable oil to the biodiesel program, instead of paying to have it hauled off.

Since 2005, the school system has been processing hundreds of thousands of used vegetable oil using about $78,000 worth of surplus parts purchased from eBay and army surplus stores. [6]

Biodiesel fuel is created by mixing the oil with alcohol and sodium hydroxide (lye) in a digester. The oil is heated before being poured into a vat where it then sits for a 2 hour chemical reaction. After an additional 8 hours, glycerin is drained from the mix. [7]  Once the vegetable oil is converted to biodiesel, sufficient heat and fuel filtering are key to ensuring the engines properly combust the processed vegetable oil.


1.  Regarding greenhouse gas emissions, the National Biodiesel Board reports biodiesel emits 78% less carbon dioxide than petroleum based diesel. [8]

2.  Biodiesel reduces emissions of particulate matter, hydrocarbons and carbon monoxide.  This decrease is due to the fact that biodiesel contains more oxygen by weight.  Oxygen allows the fuel to burn more completely, further reducing air emissions. [9]

3.  Biodiesel exhaust on average has 48% less carbon monoxide than petroleum diesel. [11]

4.  Total hydrocarbons (which contribute to smog and ozone) are two-thirds lower for biodiesel compared to regular diesel. [11]

5.  Sulfur oxides (which are building blocks to acid rain) are non-existent in biodiesel, but exist in significant concentrations in diesel. [11]

6.  Particular matter from biodiesel is about 47% less than that of diesel emissions. [11]

Going Forward

In the future the school’s Assistant Transportation Director, Grady Truett, hopes to build a biodiesel plant at nearby landfills to capture methane - an important ingredient for biodiesel. And while there are other projects in the works to convert waste to new fuel sources, the Gaston County School system has taken advantage of the hundreds of thousands of gallons of used vegetable oil.  By converting the vegetable oil to fuel, the schools are able to insulate themselves from rising petroleum costs and improve the air quality for students riding the buses.

Other school systems across the U.S. have enacted similar biodiesel bus programs.

Contact Information

Superintendent - Gaston County Schools

L. Reeves McGlohon

Phone:  704-866-6111

Fax: 704-866-6321


 Similar Programs

Key West High School

Hoover, Alabama

[1] [2]






[8] National Biodiesel Board “Benefits of Biodiesel” citing a study by the U.S. Department of Energy; National Renewable Energy Laboratory “Biodiesel Handling and Use Guide” January 2009

[9] Biodiesel Production in Municipalities and High Schools A Primer

[10] University of Tennessee, Office of Bioenergy Programs: Biodiesel: A Primer


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