In a paper titled Eco-Friendly Conveyor Belts (World Coal, October 2008), interesting arguments for why conveyor belts are the best option if one is after an ecological means of conveying were given.

In a study titled Energy efficient conveying technology and climate protection of the Mining University of Clausthal in Germany it was stated, that annually more than 12 billion tons of solid mineral resources are being extracted, with another almost 30 billion tons of overburden to be moved. In view of this volume, energy efficient means of transportation have to be considered.
If one is serious about ecological aspects, trucks, which are primarily being used in mines, must be replaced by belt conveyors, at least for longer distances. The study claims that an average mine belt conveyor consumes 0,20 kWh per ton and kilometer, which is a fifth of the consumption of heavy trucks. This of course also has a dramatic effect on the CO2 emission.