Sweden waste to energy

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Sweden is actually one of the best countries concerning waste recycling and waste optimized treatment. Indeed almost 99% of households’ waste is recycled from one way or another: material recycling, biological treatment (as compost producing), energy recovery or landfill. Concerning energy recovery in Sweden, 48.6% of the households’ waste was treated via this process which is equivalent to 2 284 210 tonnes of waste. Moreover, 1 328 500 tonnes of waste were mostly imported from Norway, Great Britain and Ireland in order to be incinerated in Sweden. Energy recovery is produced by 33 incineration plants disseminated across the territory. So what is the Swedish waste to energy system?
First, the waste to energy general process, second, the emissions management resulting from the process and third the benefits from the process.

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First, the waste to energy process is a process consisting in transforming waste to energy. Waste which is brought to the incineration plant is checked and weighed. The waste-combustible is then stocked in bunkers. Then, a crane mixes the waste and drops it into the feed hopper from which it slips to the furnace. The waste starts to burn as soon as an oil burner is used. The furnace reaches a temperature of 1000°C and waste is almost totally consumed: hot gases and a residue (15% of the initial weight) called ‘’slag’’ are released. The slag is recycled as metal is reused and porcelain and tile are treated to produce gravel for roads. The least remainder (1%) is finally deposited in rubbish dumps. Long pipes that are inside the plants transport water heated at a high temperature and pressure by the gases. Consequently, water becomes steam, which steam will be used to generate electricity, heat and cooling. Steam will accordingly be directed towards a turbine which in return will activate a generator. The generator then produces electricity (the kinetic energy becomes electric energy). As steam passes through the turbine, it still contains a lot of energy. This energy, heat, will be transferred via a condenser from steam to water and will be dedicated to district heating. Once the heat energy is consumed, the water is driven back to the incineration plant to be heated again. The cooling system works the same way with cold water. At the end of the process, the remaining water is subject to a cleansing treatment before being released: The heavy metals are precipitated and drained, and the water then passes through carbon and sand filters which residues are deposited in abandoned mines.

Second, the process harnesses any toxic gaseous pollutant. At its end, the gases are cleaned from dust through an electrostatic precipitator. Dust is then transported to an ash silo. Other pollutants as heavy metals, acids, sulphur dioxide and moistures are captured via several towers using water mixed with other substances. These towers are called ‘’scrubbers’’. Afterward, the gases pass through a catalytic converter, a fine porous ceramic material to which is added ammonia to water solution. Thereby, the nitrous oxides (undesired chemical gaseous components) are converted into nitrogen (already very common and none-harmful to the atmosphere). However, the released gas still contains CO2, and the emitted quantities are not precisely unveiled knowing that incineration is a great cause of CO2 emissions (the main greenhouse gas that causes global warming). Nonetheless, 99% of it is none-toxic gas while still one per cent is dioxins. For this regard, strict regulations are applied as the environment code of January first 1999 or the tax on household waste incineration of 2006. More specifically, a European directive on incineration waste was introduced in Sweden in 2002. The directive provides technical requirements for the incineration plants and emissions limitations. Some power plants were rebuilt accordingly. In order to, Best Available Technologies (BAT) are landmarks to fulfil the requirements. They shall be efficient and affordable. Prescriptive reference documents determine the BAT standards and are produced by the European Union via Member States sharing information.

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Third, the benefits of the process are primarily the production of energy out of matter that is originally dedicated to unuseful and potentially polluting landfill (can be assimilated to the circular economy: the waste element or consumed energy becomes a wealth element or produced energy). Thereof, electricity, district heating and district cooling are generated out of waste incineration. In 2015, in Sweden, 17 tera watt per hour (TWh) were produced from energy recovery, among which 14.3 TWh were used for heating and 2.7 TWh for electricity. As we can see in the figure hereof, almost 6 million tonnes of waste were treated by waste to energy process in 2015, in Sweden. The waste has as well a commercial value as deals are reached for the treatment of above-mentioned foreign countries’ waste. Secondarily, the use of waste as a combustible is much more environment-friendly than other fuels. For example, in 2007, waste to energy helped to save 1.1 million cubic meters of oil equivalent and consequently 2.2 million tonnes of CO2 emissions. Therefore, since waste to energy plants were developed, the Swedish seem to live in healthier and more profitable conditions.

In conclusion, waste to energy is a process broadly developed by Sweden that allows transforming mainly half of its waste to energy to the first benefit of the Swedish. Energy recovery is a long process that needs a pre-recycling phase, an incinerating phase, a converting phase and a filtering phase. The benefits of the process include waste valorisation, emissions reduction and potential commercial opportunities. Indeed, our planet and our health are worth substantial innovations and long term visions.

 

References:

http://www.avfallsverige.se/fileadmin/uploads/forbranning_eng.pdf

http://www.avfallsverige.se/fileadmin/uploads/Arbete/Remissvar/swm_2016.pdf

The Swedish recycling revolution

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