A recent review of forklift emissions studies compares data relating to propane-powered forklifts with data for forklifts operating on compressed natural gas or gasoline. The review, sponsored by the Propane Education and Research Council and conducted by two independent experts, finds that in terms of fuel production life cycles, propane provides the highest energy efficiency rating, at 89.3%, compared to CNG at 87.2% and gasoline at 81.6%. Titled “Industrial Truck Emission Data Compared by Fuel,” the report examines findings from seven forklift emissions studies performed between 1990 and 2002.
According to PERC president Roy Willis, propane is used to power the majority of internal combustion forklifts, but the market is “plagued by reports that are misleading or contain conflicting data on the relative emissions benefits of various fuels.” Willis says that if forklift emission results are compared accurately, propane remains one of the cleanest and most efficient fuels available for industrial lift trucks.
The PERC review also finds that forklifts with closed-loop controls and exhaust catalysts have significantly lower emissions, and that differences in tailpipe emissions for different types of fuel are negligible. Perhaps not surprisingly, the review concludes that to achieve these high levels of efficiency, propane forklifts require regular maintenance, and forklift operators require training to provide that maintenance.
Optimized LPG Engine Emissions
| Description | HC | NOx | HC+NOx | CO |
|---|---|---|---|---|
| Baseline | 1.3 | 15.7 | 16.9 | 9.9 |
| Closed-loop/OEM catalyst | 0.5 | 0.5 | 0.7 | 4.0 |
| Closed-loop w/new calibration | 0.3 | 0.7 | 1.0 | 7.9 |
| Closed-loop w/larger catalyst | 0.3 | 0.0 | 0.3 | 5.5 |
| Source: California Air Resource Board; South Coast Air Quality Managment District Note: Chart shows emissions test results produced by current lift truck engine technology for forklifts powered by liquified petroleum gas. |
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