Changing lead into gold has long been a dream of mankind. Converting waste into a clean fuel with both economic and environmental benefits is a similar dream that began in 1993 when the Sanitation Districts of Los Angeles County started up the world's first full-scale facility producing a high quality clean fuel derived exclusively from landfill gas. This is especially important in the South Coast Air Basin.

The Puente Hills Landfill (left) receives an average of 12,000 tons of non-hazardous solid waste per day and produces over 30,000 cfm of landfill gas. The majority of the gas is collected and used as a fuel to produce approximately 50 megawatts of power at the Puente Hills Gas-to-Energy Facility (See below).

Clean Fuels Facility
A special pipeline was added to the existing gas collection system to draw a richer core gas from several, deep vertical wells in the landfill. The pipeline draws 250 cfm of gas containing approximately 55% methane, 45 % CO2 and less than 1% air. A very small portion of the landfill gas is collected to produce the compressed natural gas (CNG). The gas purification facility is shown at the right.

Membrane separation technology was selected to purify the gas because it requires minimal maintenance and is ideally suited to small quantities of gas. The equipment is designed for automatic, unattended outdoor operation. The gas is dewatered, purified and pressurized to produce 100 cfm of high quality CNG containing an average of 97.5% methane. The gas purification equipment (left) consists of the compression, membrane and gas storage skids.

The CNG is piped to a dispenser (right) that is similar to a conventional gasoline pump.

Clean Fuels Program
The goal of the Clean Fuels Program is to improve air quality through the processing of gas not used at the power plant into CNG fuel to achieve a substantial emissions reduction. The clean CNG fuel reduces air emissions in two ways. First, it lowers the emissions from vehicles that burn CNG instead of conventional fuel. Second, it avoids the flaring of excess landfill gas. This fuel is now used as a gasoline or diesel fuel substitute to reduce emissions in Districts' vehicles (pickups, and cars), and off road heavy-duty equipment.

Working with the South Coast Air Quality Management Districts (SCAQMD), the Sanitation Districts are studying new engine technology to improve the air quality in the air basin. The Districts have received grants from the SCAQMD to assist in demonstrating the use of CNG in heavy-duty water trucks and refuse transfer vehicles.

An even greater emission reduction would occur with the displacement of diesel in heavy-duty vehicles. Approximately 1,550 refuse trucks utilize the Puente Hills Landfill every day. Converting these trucks to CNG will reduce air emissions and dependence on non-renewable petroleum products. The total cost of the CNG facility was approximately $1 million. At full production the facility is capable of producing clean fuel at an equivalent gasoline cost of $0.50 per equivalent gallon of gas.