Forklift Emissions Study

Washington, D.C. — The Propane Education and Research Council (PERC) released a review of forklift emission studies that compares the emissions data of propane to compressed natural gas (CNG) or gasoline. The review finds that propane delivers the highest energy efficiencies when compared to other fuel production life cycles.

The review also shows that propane forklifts, when fitted with approved closed loop controls and exhaust catalysts, result in very low emissions that meet and exceed California Air Resource Board Large Spark Ignition (CARB LSI) standards.

"Eighty percent of class 4 and 5 internal combustion forklifts are fueled by propane," said Roy Willis, PERC president. "Yet the forklift market is plagued by reports that are misleading or contain conflicting data on the relative emissions benefits of various fuels. We believe this review sets the record straight; when forklift emissions data is compared accurately, propane delivers the highest efficiencies and remains one of the cleanest fuels available for industrial lift trucks."

Conducted by two independent alternative fuel vehicle (AFV) experts, the review, "Industrial Truck Emission Data Compared by Fuel," examined research findings from seven forklift emissions studies performed between 1990 and 2002. "Testing conditions are an integral part of research studies," said William McGlinchey, one of the review’s authors. "Our review has found that previous research studies often did not use the same fuel delivery system and engine, elements that are crucial for accurate comparative studies."

The authors examined two studies that used Life Cycle Analysis (LCA) emissions models to assess the emissions impact of "upstream" production of a given fuel, and found that propane delivers the highest total energy efficiency relative to other fuels. Regardless of the source of production -- petroleum or natural gas -- propane delivers the highest overall total efficiency rating, 89.3 percent, as compared to compressed natural gas (87.2 percent), conventional gasoline (81.6 percent), reformulated gasoline (82.6 percent), conventional diesel (85.6 percent) or reformulated diesel (83.6 percent).

The LCA emissions model, developed by Argonne National Laboratory, provides estimates rather than specific emissions quantities. However, in the absence of specific emissions quantities, these estimates are the best available indicators of total emissions contributions for fuel production. The model estimates upstream and total fuel cycle energy consumption, greenhouse gases, and emissions for both short-and long-term scenarios. The model describes upstream emissions as the emissions emanating from pre-consumer fuel processing from feedstock to the gas station dispenser.

Propane produces low tailpipe emissions

The review finds that when propane is compared accurately to CNG or gasoline, differences in industrial truck tailpipe emissions are negligible. In addition, the review revealed that:

The most recent substantive comparison of gasoline and propane, a 2002 study conducted by Southwest Research Institute on behalf of CARB, found that emissions results meeting CARB LSI standards for large spark ignited industrial trucks could be obtained using propane and a properly operating control system and exhaust catalyst.

Forklift manufacturers and fuel systems technologies manufacturers that have met current CARB LSI requirements, including Ford Power Products, IMPCO, Jasper, MCFA, Mitsubishi, NACCO, Nissan and Toyota, all used propane fuel systems for the certification. Two manufacturers also certified gasoline engines, but none of these manufacturers chose to certify CNG fuel systems in 2001 or 2002.

Zenith Fuels Systems, Inc., a manufacturer of fuel delivery systems for industrial engine applications, conducted tests using the same fuel system and engine to compare tailpipe emissions. The test found that propane was capable of producing emissions well below CARB regulations.

Maintenance is key to performance

The review emphasizes the role that regular maintenance plays in fuel control system performance and emissions reduction. "Our next step is to support the training and maintenance needs of propane-powered forklift operators," said Willis. "PERC has funded programs to ensure that propane-powered forklift operators receive the support they need to comply with emissions standards and achieve greater return on their investments."

PERC, in its most extensive research project to date, is working with several forklift manufacturers and a private research institution to build and demonstrate the next generation of clean, low emissions forklifts.

For the full report on the study, click here.

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