The problem

Urban residues are municipal wastes linked to consumerism and generated by economic activities that constitute a global waste management problem.

The total urban residue collected worldwide is estimated to exceed 1.5 billion metric tons annually. About 65% of it goes to landfills or is thrown directly into the environment.
Over the recent years, Municipal Solid Waste (MSW) and other kind of residues have been fast evolving from the conventional management methods of landfilling, open-air burning, dumping in oceans, to more sophisticated methods.
In recent years the enormous environmental and economic downsides of landfilling have reached the top of waste policy agenda and alternatives are being sought to minimize landfilling, where policies tend towards to zero landfill and circular economy development (mainly in developed countries). Alternatives as incinerators which generate energy have proven to damage human health as carcinogenic dioxins are not eliminated even when sophisticated and very expensive filters are deployed. Meanwhile, recycling processes when deployed, are not keeping up with the high volume of waste. Recently, alternatives fuels such as biodiesel, bioethanol and bio-methanol production were expanded as a substitute for the growing energy demand. Their inherent problem is the raw materials for the production of these alternative fuels: food grains and forest trees crops.
It competes directly with human and livestock consumption of these same food crops.

The challenge remains to develop techniques that may be economical, easily replicable, avoid environmental pollution and risk to human health, reducing carbon emissions and promoting circular economy in recovering value from waste.