- Non recyclables

Treatments for non-recyclable waste: creating energy, not waste

Once we have treated food waste, and recycled as much as we can, we need to think about how we can treat the materials that are left over.

The technology options for treating non-recyclable waste are complex and vary greatly.  However, they all share one main aim – to recover value from our left over waste by turning it into energy.  They turn our waste into a resource that we can use.

Advanced Thermal Treatment (ATT)

Uses heat to treat the waste that we can’t recycle. It turns waste into a fuel, which can be used to create heat and electricity.

Pyrolysis treats waste at temperatures between 300-800 degrees Celsius in the absence of oxygen. This produces a ‘syngas’ which can be burned to create energy.  A solid waste called char is also produced. 

Gasification operates at a higher temperature than Pyrolysis.  Some oxygen is added to this process, but not enough for the waste to fully combust.   This process also produces syngas which can be burned to create heat and energy.  The other product is a solid residue (slag or ash) which can be used as an aggregate for the construction industry.

Mechanical Biological Treatment (MBT)

Uses filter screens and magnets to sort our waste.  This acts as a final stage to make sure that everything that we can recycle has been collected as the process will capture materials like metal and glass.  The remaining biological waste, our food and garden waste, is then broken down through a composting process and dried out.  The compost can then be used in land restoration projects such as covering old landfill sites.

Mechanical Heat Treatment (MHT)

Combines mechanical and heat treatments, with the most common form being a steam treatment process.  Our waste is processed in a pressurised container.  This reduces organic waste into a material known as flock, while removing recyclable materials.  The remaining material is used as a fuel in a thermal heating process. 

Energy from Waste with combined heat and power (EfW)

Combusts waste at over 850 degrees Celsius.  Energy is recovered through the incineration process by using the heat to create steam.  This can be used for heating and power.  The ash from the incinerator, known as bottom ash is then filtered to remove any remaining metals while the rest can be used as an aggregate.  Filters capture any residues or particles from the incineration process, known as fly-ash, and this is sent to landfill.  Waste is recovered as a valuable source of heat and power.