I'm aware of the attempts to collect methane from landfills. But there is a better technology that will reduce waste entering landfills in the first place... Thermal depolymerisation. It is still a relatively fledgling - but proven - technology (14-ish years old) but worth looking into. http://www.changingworldtech.com/
This invention is recycling par excellence. It would mean a reduction of new fossil carbon into the atmosphere, with a superlatively effective reuse of existing biomass. It could also solve all the CH4 emission problems of landfills; in fact, farm waste, old tyres, landfills and sewage systems would become a resource.
I realise that this system is not the complete solution, and non-carbon energy sources must be 100% implemented as soon as possible, but it is certainly a huge step towards ameliorating our CO2 and CH4 excess. There are of course many other major environmental benefits such as the safe disposal of hospital waste, PCBs, and other toxic organic chemicals