Every year, tonnes of waste are buried in landfill sites and the materials are lost forever. Most petrochemical plastics are designed to be durable and resist degradation. They can be broken down by sun light. When they are buried in landfill sites, however, they remain virtually forever.

Although some landfill sites are equipped with landfill gas capture facilities, nearly 50% of the gases is carbon dioxide, posing problems when using landfill gas for energy [9]

Meanwhile, harmful substances including acid gases released from landfill sites severely affect human health [1]. For example, babies of women living within 7 km from hazardous landfill sites have a significant excess of non-chromosomal congenital anomalies.

Incineration is burning the waste as a fuel. During the combustion process, heat and electricity can be generated with an efficiency of 27% [2]. Thus incineration is a one-time-only affair; the resources which went into the production of these materials are lost to the atmosphere. Meanwhile, ash generated in incinerators, counting for more than 28% of the total waste fed in, has no market as its toxic component poses risks to human health [3].

Incinerator emissions do not just damage the environment [4]; people from all age groups who live 3 km to 7.5 km away from incinerators have shown substantial excess cancers [5] [6]. Statistically significant excess of cancer births have also been observed near industrial incinerators.

Gasification is the conversion of materials with carbon and hydrogen in their chemical structure into syngas i.e. hydrogen gas and carbon monoxide, which are combusted to produce electricity with an efficiency of 37% [2]. Gasification requires intensive energy input to achieve 1200 to 2000 working temperature and 6900 kPa working pressure [2] [7]. Gasification is still facing many challenges. For instance ash and dust can pollute the syngas, and most gasifiers requires external heat supply [8].

For materials like plastics, the gasification products are sometimes used to re-form the monomers for plastics, which costs more energy than breaking down to monomers [2], and the energy used for production of the material is wasted.

If paper, cardboard plastics, metals and wood are kept chemically pure and physically separated then they can often be recycled and reused. A large percentage of our waste, however, is mixed together or contaminated with food waste and other contaminants. The consequence of this is that mixed waste cannot be recycled with current technologies. Current recycling facilities rely on man power and mechanical processes. Sophisticated recycling plants do a great job at recovering large pieces of rigid material, but it is impossible for them to separate waste which has been broken into tiny fragments.