There are systems that feed natural gas or propane into the diesel engines, and City Of Long Beach CA has been using natural gas / diesel hybrid trash collection trucks for many years. They work great, and only use 10% diesel while the main fuel is burning natural gas.
Because Long Beach is a utility, they can buy gas at 42 PSI, compress it to 4,000 PSI, and buy at a great rate. I think that 115,000 Btu's only cost about $1.85 last time I checked. That is like buying gasoline for $1,85 per gallon!
If the natural gas tank runs out, they will burn the normal mix of 100% diesel. They burn much cleaner on Natural gas.
The systems for propane injection into the diesel engines I have not worked with them. But they say that by adding a small amount of propane, they can reduce the amount of diesel burned, and the exhaust gas is much cleaner. While very easy to clean up a 2000 diesel engine, the 2007 and later ones are much more difficult to get 'cleaned up' as they started out from the factory very clean. By 2011, they where so clean, the joke is that the inside of the exhaust system is not covered with soot, but actually is rusty due to lack of soot.
I was thinking that for the emergency generators at my work, natural gas put into the fresh air would reduce fuel consumption by 10% to 20%, depending on the amount of natural gas being used. This would extend our fuel tank from about 30 hours to a extra day or two, again depending on the amount of natural gas used.
Fred.
