Hybrid drivetrains are being developed by Volvo trucks and heavy machines and Scania trucks for stop-and-go trucks, busses, loaders and so on.

In a low-energy future... efficiency becomes the prime consideration...

It will never make sense to burn ANY liquid fuel in an ICE at 30% efficiency >> throwing away 70% in the form of heat???

If we have a liquid or gaseous fuel... CNG; landfill gas, CTL... it will be primarily used as a chemical feedstock.

And if you did want to burn the fuel... then it would have to be in a stationary situation so that you can harvest the high-quality heat... for industrial process, space heating, water heating, greenhouses... whatever...

As for trash trucks... what better application for EV... frequent stop & start; no pollutants whilst idling, only low velocity needed... day-use only > over-night recharging

Hell, the British have had electric "milk delivery vehicles" going door-to-door for this identical role since way back in 1950s...

It also seems to me that a hybrid CNG truck would make a lot of sense for trash hauling. I'm fuzzy on whether current diesel engines can be converted to CNG like gasoline vehicles, but I do know that the Houston MTA runs most of its busses on CNG, but that these vehicles were purchased new. The buses are much cleaner and more quiet than diesel vehicles.
  The US gas situation is a heck of a lot better than the oil situation as far as supply. Most of the US sedimentary basins have only been explored thoroughly to 12,000 feet subsurface,and commercial production depths are now possible to 20,000 feet plus. Virtually all the oil is in the 2,000-10,000' depth range in wells, but the greater depth areas are prone to natural gas production. I think that we are still on the up slope in gas production as far as volumes.
  But costs go up exponentially as wells are drilled and completed at greater depths and in unconventional objectives such as coal bed methane and shale gas wells or in the deep water and subsalt plays offshore. And burning gas in vehicles still doesn't address global warming.
  Produced gas from organic wastes could have the CO2 captured and sequestered from both the upstream production and also from the exhaust of an electric generating plant in a much more cost effective manner through osmotic membrane technology,IMO because it has only one source.  

To John Milton,
Allow me to requote your paragraph, because it so correct....

"It would seem to me that a hybrid CNG trash truck would make the most sense, since they are probably the worst example of "stop and go" use I can think of the regenerative braking system really makes sense here to recover some of the energy required to accelerate all those tons of trash time and time again."

There are developments afoot that will astound you, then, but, surprisingly, they will be hybrids, but not gas electric style hybrids.  Due to the battery limitations, those are still half decade down the road for heavy vehicles.

But there is a better way.  Combined with CNG, the use of the Hydraulic Hybrid drive will enhance performance and efficiency.

http://www.nextenergy.org/industryservices/Hybrid__Hydraulics.asp

http://seniordesign.engr.uidaho.edu/2004_2005/dumpsterdivers/index.htm

http://www.greencarcongress.com/2005/02/epa_eaton_and_p.html

And of extremely great promise, the stats and details on the EPA/Eaton Corp./Ford partnership demondstrated on a sport ute:

http://www.epa.gov/otaq/technology/420f04019.pdf

On many stop and go and vehicles, including mail and delivery trucks and vans, UPS delivery vans, school buses, city passenger buses, and of course, sanitation trucks, the improvement in efficiency once these designs make their way into the fleet nation wide will result in declines of tens of millions of gallons in fuel consumption.  It is a revolution that is long overdue.

Roger Conner known to you as ThatsItImout