Treating the waste we can’t recycle

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

Man carrying black, non-recyclable waste refuse sackOnce we have reduced and recycled as much as we can, we need to develop new waste treatment facilities that can make the most of the waste that is left over as an alternative to throwing it in landfill.

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.

Below is a description of main types of treatment technologies currently available to treat our residual waste.

Energy from Waste

Energy from Waste (EfW) offers a tried, tested and tightly regulated technology that is based on the burning of waste in a highly controlled environment. Waste can be pre-sorted at the start of the process to collect any recycling that has been missed, and it is then treated at temperatures over 850 degrees Celsius.

Energy is recovered during the incineration process by using the heat produced to create steam.  The steam powers a turbine that in turn generates electricity for local homes and businesses.

EfW plants can also be used to supply hot water for domestic and commercial heating, or high-pressure steam that can be used for industrial processes. This type of facility is known as a Combined Heat and Power (CHP) plant, because of the two types of energy it produces.

The process reduces the volume of the waste treated by up to 90%.  The ash produced goes through a final check to remove any remaining metals, and it can then be used in construction projects like new roads.

Any gases created are cleaned, and air particles are filtered. ‘Fly-ash’ is collected in air clean up systems and is sent for specialist treatment.  Throughout the process, emissions will be closely monitored to ensure these facilities meet strict environmental standards.  EfW facilities in Wales will need to comply with the Waste Incineration Directive, which has been put in place to ensure that these facilities do not cause any harm to the environment or public health.

Compared to landfill, a conventional EfW plant can result in a reduction of between 32% and 41% in greenhouse gas emissions.

In short: waste is used to generate heat and electricity for local homes and businesses.

Energy from Waste process diagram

EfW process diagram graphic PDF

 

The Lakeside Energy from Waste Ltd Colnbrook facility

 

 

 

 

 

“The Lakeside Energy from Waste Ltd Colnbrook facility”

 

Watch our film about Energy from Waste “Energy from Waste an alternative to landfill”:

Advanced Thermal Treatment

The two main types of advanced thermal treatment are called Gasification and Pyrolysis. They are very similar processes, and both use heat to treat our waste.

The main difference is that Gasification occurs with a limited amount of oxygen, while Pyrolysis occurs with no oxygen at all.

Both technologies require waste to be pre-treated so that materials that don’t burn, such as metals and glass, can be removed.  Heat is then used to treat the remaining waste.

Advanced thermal treatments help recover plastics and chemicals that can be reused, and also produce a gas that can be burned to create energy.  The ash that is left at the end of the process can be used in the construction industry.

Similar to Energy from Waste, emissions are closely monitored to ensure the facilities meet strict environmental standards.

In short: waste is broken down into chemical products and a gas that can generate energy.

Mechanical Biological Treatment

Mechanical Biological Treatment (MBT) is an intermediate waste treatment technology designed to remove any recycling left in your rubbish bin or black bag.

MBT uses a range of equipment to sort and remove any recycling or compostable material that may have been missed in your rubbish bin or black bag. These include:

Screens can help to remove the larger pieces of waste

Magnetic separation can remove the ferrous metals (cans made of tin)

Eddy current separation can remove the non ferrous metals (cans made of aluminium)

Optical separation can separate certain types of plastics

Air classification can help to separate light and heavy materials (paper for example).Once separated some of the materials can go on for further recycling

MBT is not a replacement for local recycling and composting schemes, it simply compliments the wider treatment of our waste. The materials recovered from the MBT process will be of a lower quality than the ones collected for recycling at the kerbside.

After the MBT process has removed any valuable materials from our rubbish bags, and composted any biodegradable waste most of the remaining material is then turned into a refuse-derived fuel for use in energy from waste plants.

Inside Avonmouth Mechanical Biological Treatment facility

As with all waste facilities, MBT plants will need an environmental permit and their performance will be monitored closely.

 

 

 

Avonmouth MBT facility. Image courtesy of New Earth Solutions Group

In short: waste is reduced in volume and can be turned into a fuel for burning.

 

Mechanical Heat Treatment

Mechanical Heat Treatment (MHT) is a term that is used to describe a number of different processes that involve the mechanical (separation) and thermal (heat) treatment of waste.

The most common method of MHT currently being used is called Autoclaving.  This steam treatment process can produce some better quality recyclable materials, such as glass and metals, as the steam cleans them and reduces any contamination.

After the steam treatment, the process is similar to that outlined for Mechanical Biological Treatment. 

Food and garden waste is reduced into a material that can be used in land reclamation, while the remaining material can be used as a fuel.

These facilities need an environmental permit and their performance will be monitored closely.

In short: waste is turned into a fuel and we recycle as much as possible.

“80 percent of people agree that building new waste treatment facilities will help us manage our waste in a greener way”