Limited future for energy from incinerated waste imports

Five per cent of Denmark’s electricity and 20% of its district heating is supplied by energy from incinerating waste, around 10% of this waste is imported. This practice is unlikely to be compatible in the longer term with decarbonising energy production, explain Marie Münster and Amalia Pizarro from the Technical University of Denmark and Ciprian Cimpan from the University of Southern Denmark

The future of waste incineration is of significant interest in a country like Denmark, which boasts some of the most energy efficient waste facilities in the world. Energy from these plants supplies around 5% of the country’s electricity and 20% of its district heating. Higher EU recycling targets and landfill bans are, however, changing the game, as are concerns about building too many incineration plants and a fear of stranded assets as climate targets tighten. Waste to fuel these facilities is imported into Denmark, but our research shows this is unlikely to remain a climate-friendly solution given the long-term focus on decarbonising energy production.

Waste imports bring greenhouse gas reductions as, for the moment, they displace coal and natural gas for electricity and district heating production in Denmark, and mean less waste goes into landfill in other countries. But waste combustion emits greenhouse gases and it is important to question whether imports have a role in an increasingly decarbonised economy.

The carbon footprint of combustible waste imports depends on how the waste would otherwise be treated in its country of origin, and the emissions from power and heat generation in the importing country’s energy system.

Denmark plans to rid its electricity and district heating production of fossil fuels in the coming years. This means the import of waste with fossil content would only make sense from a climate perspective if the alternative was for it be dumped abroad in an old-fashioned landfill with high methane emissions or if Denmark would otherwise use unsustainable biomass with high indirect land-use change emissions.

At least one Danish operator is also exploring the impact carbon capture and storage (CCS) would have on the carbon footprint of waste incineration.

Stranded assets

Any new incineration plants must neither hinder recycling targets nor lock Denmark into importing waste. Facilities are at risk of becoming stranded assets if importing waste to produce energy is no longer ecologically attractive because of climate goals. CCS could improve its carbon footprint, as could the import of non-fossil waste, such as wood wastes.

The uses of imported waste, were it to continue, could also change. The significant challenge of decarbonising certain sectors, such as heavy transportation or process heating, mean new ways of managing the remaining fractions that cannot be recycled could be explored, such as gasification or pyrolysis. The value of using waste as a resource and to reduce the use of fossil fuels in these sectors might be higher than for electricity and district heating generation if technology becomes cost-competitive.

Our study shows that imports of up to 300,000 tonnes of combustible waste currently provide socio-economic benefits, not taking environmental impacts into account, especially to cover the need for extra power and heat in winter. This threshold is likely to increase as incineration plants become more efficient or set fees for accepting waste at a level that undercuts landfill in exporting countries. Less efficient heat pumps and high wood pellets prices would, furthermore, increase the value of waste as a fuel and vice versa.

In short, importing residual combustible waste for Danish incineration plants that produce power and heat may have positive socio-economic value now and in the short-term future. The business case will be helped if, as expected, waste incineration plants, in an effort to ensure their future and better manage change, move towards centralised cogeneration to benefit from economies of scale.

But our research suggests that in the longer term, expected reductions in greenhouse gas emissions from power and heating systems, and improvements in waste management in countries of origin, are likely to rule out imports of waste for incineration as a good idea from a carbon footprint perspective

Marie Münster is a professor with special responsibilities at the Technical University of Denmark, Amalia Pizarro is a PhD student at the Technical University of Denmark and Ciprian Cimpan is postdoctoral researcher at the University of Southern Denmark

Links to research:

• The economic value of imports of combustible waste in systems with high shares of district heating and variable renewable energy
• The climate footprint of imports of combustible waste in systems with high shares of district heating and variable renewable energy

Image: Matilda Fenger Flindt

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