Controversial and complex: Waste-to-energy and district heating

District heating is the largest energy source for building heating in Sweden: it supplies 90% of the heat demand of multi-family buildings and around 50% of total building heat demand.67 The network is fed by many sources: from excess heat from industrial processes and data centres, to combined heat and power (CHP) plants and boilers. [68] Currently, however, waste-to-energy plants contribute approximately 25% of the district heating energy supply. [69] A well-established practice, Sweden recovers energy from half its household waste —meaning that in 2019, each Swedish resident sent an average of 235 kilograms of household waste to incineration, topping the EU rate by 20 percentage points. Sweden's 35 incineration plants supply electricity to 700,000 households—and district heating to 1.2 million. [70] And it's an efficient system: Sweden recovers more energy from waste than all other European nations. Domestic waste generation doesn't even fulfil its infrastructure's capacity, leading to plants treating more than 1.5 million tonnes of waste from other European countries: incineration plants require constant inputs to supply enough electricity and heat, even more so than other waste management facilities. But while this is firmly entrenched in Sweden, it has drawbacks that shouldn't be ignored: energy recovery from waste does not qualify as 'circular', and the EU has made moves to phase down the practice. While a portion of what's incinerated, such as hazardous or medical waste, doesn't have options for higher value retention, Sweden may aim to cut the use of high-value, recyclable waste in waste-to-energy by improving sorting and recycling infrastructure. Its district heating system is also already linked to electricity through heat pumps—meaning there is already an opportunity to produce heat through sources other than waste. Geothermal heat pumps can also be integrated into the district heating network as third parties; rather than being mutually exclusive, they are complementary and in theory, mutually reinforcing.

However, it may also be noted that the country is potentially 'locked into' a system that protects vested interests, and may reduce investment in higher-value cycling applications. While the capacity to recycle plastics and other forms of waste remains relatively low, CHP plants based on waste-to-energy remain the best option. This could be interpreted as a failure to establish strong markets for recycled materials, and the efficient recycling practices needed to do so. Yet the companies investing in waste-to-energy are often different from those that may invest in recycling infrastructure and technology.

While we model increasing the number of heat pumps in the district heating system, there are an abundance of other options to shift away from waste-to-energy. Locally generated renewable energy, for example, could be fed into district heating. This is already a reality in some places, as many combined heat and power plants operate in, or in the vicinity of, urban areas, making them more readily accessible to households; while several large scale heat pumps recover heat from the ground, sea or sewage water and feed it into the district heating system. Moreover, it could be possible to lower the temperature of the district heating grid, by making the least performing buildings more energy efficient; or feeding waste heat into the grid at lower temperatures, for example by cooling data centres. As more Swedish companies aim to produce fossil-free hydrogen—a major decarbonisation pathway popular among industry players—this technology may also play a more prominent role in the energy system in some parts of Sweden.

While the current system is complex, a realistic scenario could see a gradual shift away from waste-to-energy backed by public policy and regulatory changes and an understanding of electricity and heat production in a circular resource system. Using excess heat from industries and carrying out waste-to-energy processes for non-recoverable or hazardous waste remain valid opportunities to continue using Sweden's vast infrastructure.

Sparking high-value material reuse in the Swedish construction sector

Sweden is making strides to ensure its infrastructure build-up is based on green principles. Based on new policy instruments proposed by the Delegation for a Circular Economy, [73] the Swedish Environmental Protection Agency (EPA) is investigating how materials excavated during construction processes can become more circular.[74] As of August 2020, stricter regulations have been rolled out for construction and demolition waste: higher-value waste management practices are now prioritised over low-grade applications.[75] The reuse of building materials is being made even easier through, for example, the creation of the Center for Circular Construction (CCBuild). The Center offers several digital services to support a transition to circular flows, from a Product Bank and Inventory App to a digital marketplace to buy and sell secondary materials. Businesses are also able to make use of value analyses, including performance reports and quality criteria for secondary materials, to guide the process.[76] While these initiatives have sparked a paradigm shift in the building sector by targeting waste and increasing material reuse, strategies that address overconsumption and unsustainable materials still need to scale up.