Energy from waste FAQs

West London’s black bin waste (rubbish) is collected from homes across west London and taken to one of two transfer stations in either Brentford or Ruislip. The waste is packed together and loaded onto trains to be taken to our energy recovery in Avonmouth, Bristol.

Sending the waste to our energy from waste facility by train instead of using lorries saves the equivalent of 130 road journeys a day. Six trains make the journey every week to the facility which converts up to 360,000 tonnes a year of our black bin waste into enough renewable energy to power 50,000 homes.

Recovering energy from waste material left over after recycling is an essential component of the “waste hierarchy” and, as a result, the UK’s recycling and waste management system.

The waste hierarchy1 (pictured below) is the policy framework which ranks waste management options according to what is best for the environment, and it has been largely responsible for determining the way the UK’s waste management infrastructure looks today.

Preventing waste, at the top of the hierarchy, is the best environmental option for all forms of material, while disposing of waste material in landfill, or through incineration without energy recovery, is the least preferred option.

The Landfill Tax, introduced in the UK in 1996, aimed to drive more waste material further up the waste hierarchy into energy recovery and recycling and thereby reduce disposal in landfill. As a result, over the past two decades, the UK has moved from single-digit recycling performance figures to an average household waste recycling rate of more than 45 per cent, while millions of tonnes of “residual waste” (the waste left over after recycling) is now used to generate energy instead of being disposed of in landfill.

There are currently between 50 and 60 energy recovery facilities across the United Kingdom and these typically serve the needs of specific local authorities and their surrounding areas. Combined, in 2019, these plants exported around 2% of the UK's total electricity generation or 6,600GWh, while those facilities connected to heating networks also exported 1400GWh of heat2.

The Environmental Services Association (ESA), and the wider recycling industry, are key proponents of a circular economy and this is at the heart of all that we do. The majority of our members have invested in services and infrastructure that provide solutions across the whole waste hierarchy - not just energy recovery - and we would like to see as much waste material recycled, re-used and put to good use as possible.

Once buried in landfill, the inherent resource value of waste materials is lost and cannot be returned to a circular economy, whereas activities further up the waste hierarchy are designed to extract the maximum value from these waste materials.

For residual waste left over after upstream recycling, re-use and waste avoidance measures have been implemented, generating energy and returning that energy back into the cycle of production is an essential, complementary, component of a circular economy.

Recycling and energy recovery have very different drivers and the availability of energy recovery infrastructure does not impact upon investment in recycling infrastructure or the performance of recycling services.

Investment in recycling to date has primarily been determined by the health of global secondary raw material markets, which have shown their constraints in recent years.

Recycling performance, and the availability of quality recyclable materials in the waste stream, is also influenced by complex drivers including product and packaging design choices and material uses; demographic and geographic factors; individual behaviour (and the factors that influence this behaviour); and recycling service design, among others.

However, if implemented correctly, measures due to be introduced in England through Defra’s Resources & Waste Strategy, along with counterpart policies in the devolved administrations, are likely to address many of these drivers and unlock a new wave of private sector investment in recycling infrastructure and funding for recycling services – while removing many un-recyclable packaging formats from the market.

As just one example of the efficacy of policy in this area, over the past two years, ESA members have already increased investment in domestic plastics reprocessing on the promise of a new "Plastics tax" which will drive market demand for recycled polymers in the UK.

There is no defined causal relationship between availability of energy recovery and recycling rates because there are a large number of complex factors which influence local recycling performance, which in turn affects the volume of residual waste arising as a proportion of all waste generated – since waste producer recycling activity always happens upstream of energy recovery.

To further illustrate this, both in Europe and in the UK, there are many local authorities which have access to energy recovery infrastructure and high rates of recycling, and there are also examples of local authorities which have access to energy recovery and low rates of recycling.

Any correlation between the two factors, in either scenario, is often cited as evidence of a causal relationship, but there are simply too many variables across local and national drivers to allow for a true and accurate comparator analysis to date.

Energy recovery infrastructure is designed to treat “residual waste”, which is a term used to describe the waste material left over after other upstream recycling, re-use and waste prevention activities and processes have taken place. This is typically anything people put in a general rubbish bin rather than separating for recycling.

Every person and business in the UK has access to comprehensive recycling services and we are all encouraged to reduce, re-use and recycle as much as possible in accordance with the waste hierarchy.

Despite this, many recyclable materials are disposed of as residual waste by waste producers and must be treated as such, because it is not practicable or economically viable to extract these materials for recycling once they enter the residual waste stream.

The more we all recycle, the less recyclable material will be left in the residual waste stream, but there are many complex drivers of recycling behaviour. All of these drivers need to be considered and addressed to help people to recycle more.

Materials which could have been recycled often arise in the residual waste stream and this can happen for one of several reasons.

Typically, materials which could have been recycled are simply placed in the residual waste bin by a person discarding the material instead of being recycled. Once they enter this waste stream, these materials are destined either for landfill or energy recovery because it is not viable to extract these materials from the waste stream. This is why it is important that we all place the right material in the correct waste stream.

In some cases, materials are separated for recycling but are either not recyclable, or become too heavily contaminated - with food waste for example – to be economically recycled. Typically, any material separated for recycling that is not subsequently of sufficient quality to be made into new things, will be diverted to the residual waste stream and will therefore be treated in energy recovery or landfill.

Energy recovery is a largely transitionary technology which allows waste producers to divert material from landfill while society pursues a more circular economy - by moving an increasing proportion of waste material further up the waste hierarchy.

However, even if the UK meets its ambition of achieving a 65% average recycling rate by 2035, the waste sector still forecasts a significant shortfall in energy recovery capacity in 2035 based on current trajectory, since there will always be a remaining portion of waste material left over that will require treatment without relying on landfill. The Resources & Waste Strategy also sets a target of no more than 10% municipal waste to landfill target by 2035 and energy recovery will be essential to achieving this target.

The primary role of energy recovery is to provide a sanitation service to society by treating the residual waste left over after recycling. This waste would otherwise go to landfill. It cannot therefore be directly compared with other forms of energy generation, since the energy generated is a by-product of the primary waste sanitation process, while conversely, other forms of energy generation clearly are not designed to process waste.

At present, policy-makers and those involved in recycling and waste management use the Greenhouse Gas (GHG) emissions arising from the treatment of waste in landfill as the basis for comparison with energy recovery carbon performance, since the primary purpose of both solutions is to dispose of residual waste.

At present performance, energy recovery represents a lower carbon solution for the treatment of residual waste than landfill and the delta in emissions performance between energy recovery and landfill is likely to further grow in favour of energy recovery with efforts to de-carbonise feedstock and improve the efficiency of these facilities in future.

Waste treatment and disposal is an essential component of society and will remain so in future – certainly within the UK’s transition to a net-zero carbon economy by 2050. The carbon-reduction performance of the recycling and waste management sector is recognised by the Committee on Climate Change and we have reduced our emissions by 63% compared to 1990 levels – which has largely been achieved by moving waste material out of landfill. However, increasing recycling and lowering carbon from energy recovery are both essential to our sector achieving net zero carbon emissions and therefore playing our role in hitting the UK’s carbon targets.

The ESA and its members will publish a Net Zero Carbon Strategy for the recycling and waste sector in 2021 setting out how it will lower carbon from the full range of activities, including energy recovery.

The ESA and its members are developing a Net-Zero Carbon Strategy which will drive down carbon emissions associated with energy recovery by working with others to remove as much recyclable fossil- based materials from residual waste streams as possible.

This will be most effectively be achieved through upstream interventions designed to encourage greater recycling of plastics; while longer term secondary interventions will include maximising the use of heat- energy from these facilities as well as electrical energy; and by exploring the potential for carbon capture and storage – which is in line with recommendations made by the Committee on Climate Change.

Control of emissions starts in the furnace with good combustion control to supply the correct proportion of air and maintain the temperature. Gases from the burned waste are thoroughly cleaned, in a process which uses ammonia, activated carbon and lime, before the gases are passed through a fine fabric filter, neutralising pollutants and removing particles. Monitors in the chimney continuously check emission levels for compliance with the stringent limits set out in the facility’s environmental permit

Attempting to segregate materials once they enter the residual waste stream is expensive, energy- intensive and produces poorer quality recycled material. Experience tells us that pre-treament solutions, such as mechanical biological treatment (MBT), have been unreliable and costly, and often fail to meet their promised performance.

Furthermore, any plastics (or any other material) removed from the residual waste stream are often low quality or heavily contaminated and still require a viable use or alternative treatment solution. As such, experience tells us that interventions should be focussed further upstream to stop recyclable plastics from entering the residual waste stream in the first place.

Segregating material for recycling is most effective when it occurs further upstream of waste disposal activities. Everyone in the UK has access to comprehensive recycling services and recyclable materials should be separated for recycling, with only those materials that cannot be recycled placed in the residual waste stream.