LPG, forklifts and emissions

Hi all

The situation is significantly more complex than has been suggested by many.

Electric forklifts are not zero emissions forklifts. They are zero emissions at the point of use. However battery charging produces hydrogen, and a kg of hydrogen is equivalent to around 8 kg of CO2 as greenhouse gases. And in producing electricity conventional power stations generate emissions, and after allowing for transmission and battery charger losses the level of these emissions is similar to those produced by a modern turbocharged diesel engine.

And whilst there is a strong belief that LPG is a "clean" fuel, this is not necessarily so. There are two situations where this belief can be very wrong.
Automotive LPG tends to have its composition regulated. In Europe the situation used to be that the concentrations of propane and butane varied from 100% propane: 0% butane in UK and Ireland to 20%:80% in Greece. These variations could cause significant levels of emissions, especially CO depending on the sophistication of the IC engine management system.

In the USA automotive complies with HD5 with 90% propane and a mix of other higher chain hydrocarbons.

However this does not mean LPG for forklifts is regulated (it is not regulated in Australia) and as a result the composition from LPG cylinder to LPG cylinder can be significant. With older IC engines in older forklifts which do not have O2 sensors coupled to air-fuel ratio adjusting systems the variation in CO emissions can be huge. I have measured levels up to 9% - a level which would have the CO levels in a moderate size warehouse above safe limits in minutes.

The other concern is LPG IC engines with catalytic converters. The catalytic converter only becomes effective when it is hot, and this can take up to 10 minutes with a lightly loaded forklift. So where LPG forklifts are used for short periods and intermittently, levels of emissions and pollutants may on average be high.

In the testing I have been involved with diesel engined forklifts have been the most consistent in respect of low emissions. Diesel NOx emissions may be 2-3 times higher, and PM10 particulates 8-10 times higher. But CO may be 8-10 times compared to an LPG unit in perfect tune, or much lower if the LPG unit is out of optimal tuning say due to variation in LPG composition.

Finally, because diesel engines are so much more efficient, and diesel tanks generally have a greater capacity than LPG cylinders, refuelling of a diesel forklift may only be required once for every three LPG cylinder changes. This gives productivity benefits.

As indicated, the situation is more complex that many realise.