Waste is a vast resource. According to the European waste hierarchy, waste should be prevented, reused, and recycled. Instead of going into a landfill, energy should be recovered from waste that cannot be recycled because it is too dirty, mixed or degraded having undergone several times of recycling. In 2015, the average European generated 476 kg of waste–26% of this waste ended up in landfills, which is the least desirable option. Landfills pose a number of environmental risks: they emit methane which is a very potent greenhouse gas while microplastics from uncontrolled landfills find their way into oceans and rivers. Over time, groundwater can even become polluted through landfill leaching.

With a population of over 46 million, Spain still landfills around 11 million tonnes of municipal waste every year meaning that around 1/6 of all landfilled European waste is Spanish waste. However, Districlima, a heating and cooling network in the city of Barcelona is a clear example of how residual waste can contribute not only to sustainable waste management but also to the Energy Union targets of reducing greenhouse gas emissions and European energy dependence on fossil fuels.

Under the current Renewable Energy Directive, energy recovery from the biodegradable fraction of municipal waste is considered renewable energy (biomass). While the obvious preferable option for biowaste is to compost it, this needs to be clean biowaste. If the biogenic waste is polluted or difficult to separate from the remaining residual waste (a good example of that is a used cardboard pizza box), this waste is not suitable for quality compositing or recycling. The best option for this waste is to be treated in waste-to-energy plants that produce clean, renewable and local energy from it.

Since the commissioning of the Districlima network back in 2004, TERSA, the waste-to-energy plant of Barcelona, has been directly supplying the network with energy in the form of steam. Depending on the time of year, the steam is used to produce heating or cooling. Using district network for cooling also reduces the use of hydrofluorocarbons (HFCs), normally used in stationary air conditioners, which are thousands of times more destructive to the climate than CO2. The TERSA waste-to-energy plant produces most of the heat and a good share of the cold for this 16.8 km long network, which helped Barcelona reduce its fossil fuel consumption by 58% and save almost 19.000 tonnes of CO2 emissions yearly. Because of the reduced CO2 emissions in heating and cooling compared to fossil fuels, the energy performance of the buildings served by Districlima improved from 99,83 kgCO2/m² (E-label) to 55,14 kg CO2/m² (C-label). The network currently supplies 95 clients including hotels, hospitals, convention and education centres and continues to expand.

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