BLOG – Waste to Energy: how it compares to recycling

Waste to Energy (WtE) has seen a surge in popularity in the UK and internationally in recent years as a way of bridging the gap between recycling and landfill. Once materials that can be recycled have been removed from the waste stream, WtE provides a further way to process the remaining waste instead of directing it straight to landfill. While Devon Contract Waste supports any initiative that reduces the amount of waste reaching landfill, we believe it’s important to look at the total impact of WtE and how it compares to recycling.

Where WtE comes in

Under the EU Waste Framework Directive the UK must apply the waste hierarchy:

  • Reduce – cut down on the amount of waste we produce
  • Re-use – use items more than once whenever possible
  • Recycle – process waste items into re-useable materials
  • Recover – waste contains energy that can be unlocked and used
  • Dispose – final remaining waste is usually sent to landfill

Devon Contract Waste operates at the Recycle stage – sorting and processing waste materials into separate streams that can be re-used. WtE is part of the Recovery stage of the hierarchy. WtE plants use waste as fuel, instead of fossil fuels, to heat water that produces steam, which drives turbines to generate electricity.

WtE is the final stage of our own Zero to Landfill process. Once all recyclables have been sorted for onward processing, around 42% of our collected waste is sent for incineration to generate energy. WtE plays an important role in waste management but we believe strongly that it should be our last resort in the management of waste and we should always aim to recycle more to reduce the amount of waste that will be burned.

High cost / low volume

WtE plants are complex facilities that are expensive to build compared to a recycling centre – or materials recovery facility (MRF). Exeter’s WtE plant was built to process 65,000 tonnes of waste per year at a cost of £45 million. A typical materials recovery facility (MRF) with a processing capacity of 250,000 tonnes per year would cost around £11 million and would generally recover around 58% of materials for recycling, before the remainder was processed for WtE. In terms of the capability of each process to divert waste from landfill, recycling materials is more economical, and more efficient.

Energy efficiency

The energy produced by WtE plants most commonly generates electricity for homes but cogeneration plants can also provide heat for nearby businesses. Each tonne of waste processed generates around 500kWh of electricity which is enough to power 15 average households for a day. However, depending on the materials being processed, it could be more energy efficient to recycle. For example, recycling one tonne of aluminium (instead of making it from raw materials) saves 14,000kWh – enough electricity to power those same 15 households for four weeks.

Impact on recycling rates

Ideally, before waste reaches a WtE plant, all recyclables should have been removed. Not only for the efficiency we outlined above, but because less carbon-rich recyclable material in the waste mix (eg cardboard, plastic, metals and wood) means less CO2 output when the waste is burned. Some argue that the presence of WtE plants may discourage recycling, particularly among domestic households. Increased levels of these carbon-rich materials in the WtE fuel will mean more CO2 emissions. The link between WtE facilities and recycling rates hasn’t been proven but it remains an important consideration in planning a waste programme.

Polluting outputs

WtE produces less CO2 compared to the equivalent production of new materials. It also avoids the release of methane – another greenhouse gas – that would otherwise seep from landfill sites. But the incineration of waste releases a great number of toxic gases and substances which must be tightly controlled. Acidic gases such as nitrogen oxide must be neutralised, and toxic mercury must be removed. WtE is also not 100% efficient at processing its fuel, producing a final ash deposit which is usually sent to landfill.

Sustainability in the UK

Only certain types of waste are suitable for WtE processing which means that the availability of this fuel is an important consideration in a WtE programme. With many WtE plants already operating in the UK, capacity is outstripping the available fuel. UK WtE plants are importing waste from other countries in order to remain sustainable. While this is clearly preferable to simply sending the waste to landfill in the country of origin, the carbon miles travelled by thousands of tonnes of waste rather defeats the object. Sweden, for instance, is importing around 800,000 tonnes of waste per year, generating enormous quantities of CO2. We don’t feel that the UK should be contributing to this when we have an opportunity to invest in better recycling.

What does the future hold?

There is no straightforward answer to striking the right balance between recycling and WtE. As long as we continue to produce waste that cannot be recycled, WtE provides an energy efficient alternative to landfill disposal, despite its downsides. What remains critical is ensuring that our national recycling effort is maximised to reprocess as many materials as we can, in turn ensuring WtE is as efficient as possible, and landfill sites are consigned to the history books.