One of the problems with the disposal of even household trash (in California, at so-called Class 3 landfills) is that pollution, particularly of groundwater, may result, even from well constructed sites. Sometimes construction is less than ideal; sometimes earth movement or earthquakes fracture the containment systems.
For years some particularly toxic types of waste, such as refinery sludge, have been "remediated" by breaking them into their constituent atoms with plasma torches. Such technology can be expensive, running $2,000 per ton of waste. Since costs are beginning to drop and strategies to use the byproducts of the process to generate electricity are being considered, there may be a path toward decreasing the use of landfills.
If the waste is turned into its constituent carbon and oxygen atoms, then these can be recombined into CO and H, the latter being linked up as diatomic hydrogen molecules. The electricity generation thus comes from "torching" organic materials into syngas, a mixture of CO and H, which is burned to generate electricity. Metals and other inorganics conceptually fall to the bottom of the torch chamber as slag, which may have use as bricks or road paving.
One technological advance that helps this concept are improvements in plasma torches. The nickel alloys in the torches have improved considerably, and hold up better even in such a harsh environment. Also, computational fluid dynamics (http://en.wikipedia.org/wiki/Computational_fluid_dynamics) can be applied so that the rubbish mix going into the process is maximized for syngas production.
The first such plants were built in Japan, driven by the high cost of land. There are now pending more than 3 dozen proposals to build plasma-torch syngas plants in the U.S. Some of the proposals harken back to the days of yore when syngas was an important industrial input; it was eclipsed by the petro chemical industry, but may arise again.
For more information, see http://www.tampabay.com/news/perspective/turning-garbage-into-gas/1150825, http://science.howstuffworks.com/environmental/energy/plasma-converter.htm, http://www.slate.com/id/2181083/, and http://discovermagazine.com/2007/may/the-ultimate-garbage-disposal.