Recently, the energy decline movement has proposed a new idea: large semi trucks cannot run on any fuel other than diesel. Only diesel offers the combination of high energy density for long hauls, and high torque for heavy loads. No other fuel or energy source will do. Battery electric trucks do not have sufficient range for long hauls.
Furthermore, gasoline is not suitable for heavy trucking. Gasoline has enough energy density for long hauls, but gasoline engines do not have enough torque to carry such heavy loads. Large diesel truck engines often produce 1,500 ft-lb of torque, which is several times higher than even the largest gasoline SUV engines. As a result, semi trucks can only use diesel as fuel.
This idea is not correct. Heavy trucks could easily run on gasoline or many other fuels. The torque of gasoline engines could easily be increased using a simple gear reduction. A simple 3:1 gear reduction would increase the torque of gasoline engines (and decrease the RPMs) so that the torque is far higher than a diesel engine. A gear reduction decreases RPMs and inceases torque, which is one of the main purposes of the transmission in almost every motor vehicle. As a result. it’s obviously possible to increase the torque arbitrarily by using gears.
Large semi trucks frequently already have 2 (sometimes 3) separate transmissions in series, with 12 or more separate gear combinations. Adding another simple gear reduciton would only modestly increase the complexity and wear of the transmission.
There is also another way (besides gears) for semi trucks to run off gasoline. It would be quite possible to build gasoline-electric trucks, where the engine is not connected to the wheels at all. The gasoline engine drives a generator, which generates electricity, which powers an electric motor and drives the wheels. This kind of setup is already widespread and is used in almost all locomotives, many large articulated city buses, and a few passnger cars (Mazda MX-30 and Honda Clarity). In these vehicles, the torque of the engine is completely unimportant because the engine is not connected directly to the wheels. In this case, only the power of the engine is important, and even some big SUV engines have sufficient power to drive a large semi truck.
It is also possible to liquify coal and create synthetic diesel thereby, which is perfectly suitable for trucks. This has already been done on a massive scale. The South African company, Sasol, has been liquifying coal and creating diesel for many years on an industrial scale.
It would also be possible to use battery-electric trucks for long hauls, by stopping to recharge for an hour during the middle of the day when the sun is shining. The trucks only need enough range to make it from one recharging station to another. Bear in mind that truckers are paid to do this. Things which consumers find inconvenient will be done by truckers if necessary. For example, truckers have been tolerating the complicated manual transmissions and 12+ gears on trucks for many decades. The large transmissions of semi trucks (with 12 or more gears) are necessary because the engine of a semi truck is just large enough to carry the load, unlike passenger cars which are absurdly overpowered for their weight. As a result, a sem truck needs more than 12 gears, and complicated shifting, to reach freeway speeds. If truckers were willing to tolerate the complicated shifting, then they will be willing to tolerate stopping and recharging once a day for an hour around noon, or at staggered times.
Finally, there is one more energy option for trucks. Gasoline could be used in existing turbines for electricity generation at power plants, and the natural gas which is freed up thereby could then be used as a truck fuel. Natural gas is obviously a suitable fuel for heavy long-distance trucking, because there are already more than 100,000 natural gas semi trucks in China alone which are used for long distance trucking. Natural gas is far more abundant than diesel ever was.
As a result, we could use the following fuels for heavy long-distance trucking:
1. Solar or wind energy, by stopping and recharging a battery electric truck every 300 miles or so.
2. Diesel fuel (obviously)
3. Gasoline
4. Natural gas
5. Coal (using liquefaction)
6. Kerosene (can be used in either spark ignition or compression ignitiion vehicles)
7. Biodesel from crops such as soy or canola
8. Solar or wind energy which has been converted into liquified hydrogen
The clear conclusion is that we have a massive abundance of truck fuel, far into the future. We have centuries until we run out of truck fuel just from fossil sources, and even then, we have other options.
