Every year, tonnes of waste are disposed in landfill sites and the materials are lost forever. Plastics, designed to be resistant to biodegradation, can potentially remain in the land forever. Subsequently, the “lifespan” of landfill sites are extremely limited.

Apart from these, methane and carbon dioxide produced in landfill sites cannot be captured to generate energy, but released in the atmosphere, enhancing the greenhouse effect.

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

Incineration is the conversion of materials to carbon dioxide and water. 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.

Gaisification 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. However a large percentage of our waste 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.

Separation facilities are required to deal with mixed waste and there is a limit to how much of the materials can be recovered. Often more than a fifth of the materials which pass through can not be separated. At the site we visited this amounts to 320,000 tonnes a year of waste which must be disposed of by the previous three options. Our waste to P3HB system diverts the waste to produce valuable commodities and reduce the environmental impact.