As part of our efforts to diversify our energy sources, it's great to see the surge in interest and development of renewable energies such as solar and wind power, and innovations in tidal and wave power, but to really be able to reduce our use of fossil fuels, we might need to also explore some of our other options, such as using materials extracted from our waste streams as fuel.
One emerging technology is working toward converting some of the non-marketable post-consumer plastics into a solid low-carbon fuel. While recycling of some plastics back into other materials makes sense for closing the loop on plastics a bit, until we can divert all recyclables from the waste stream, using some of it as an alternative fuel may be yet another way we can diversify our energy sources.
"Although recycling rates have increased over the last few decades, more than 50% of our waste still ends up in landfills. Now, by using a novel energy recovery technique, we can reduce the amount that is sent to landfills and produce a fuel that is relatively clean and more energy dense than coal." - Webber Energy Group
So far, to my mind, there are plenty of 'ifs' that would determine whether or not this is not just feasible, but actually desirable as well, in terms of both the environment and the economy. Sure, it makes sense to reduce the amount of materials that are getting buried in landfills, and it makes sense to be able to take those waste materials and turn them into energy, but we also need to make sure we're not creating a bigger problem with air or water pollution, or opening a loophole for other types of industries incinerating their waste under the guise of "clean energy".
The American Chemistry Council has a site devoted to "From Chemistry to Energy" which has more information (although it's definitely biased in favor of the practice of "Energy Recovery" from municipal waste, as well as natural gas from shale).