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How does the Waste-to-energy technology work? What role can it play in heat and power production, for example as a production unit in district heating systems? This text provides knowledge about Waste-to-energy and waste incineration, including health studies and environmental impact. Cities, energy companies, waste management companies and other stakeholders can learn more about the waste recovery method, its role in recycling and its part in a circular economy.
Some materials are hard to recycle. But there is a way to make use of rubber boots, contaminated packaging and other waste that recyclers don’t want. Waste-to-energy (WtE) is a method for using waste as fuel to produce heat and electricity. The advantages? Reduced climate impact, and an opportunity for cities to achieve a sustainable and financially viable energy production unit.
Waste-to-energy is a collective term for the thermal treatment of household and commercial waste where the energy content is used as heat and electric power. The advantages are numerous. Using the energy content in waste - instead of sending it to landfills - will reduce the need for other energy sources for heating, including fossil energy. Less landfill space is required, and the emissions of methane (landfill gas) will therefore decrease. Lastly, heat customers can benefit, as well as cities aiming to be a part of the energy transition.
Waste and incineration requirements
for Waste-to-energy
By using waste as fuel to produce heat and electricity, the energy content of the waste is utilized. The weight of the waste is reduced to about one-fifth after incineration. Around 50 per cent of the waste fuel consists of household waste. The remaining waste comes mainly from industries and often consists of sorted fractions with a more homogeneous composition. However, these fractions differ greatly between the different countries and plants.
Normally, sorted combustible household waste is delivered to the plants. It must not contain hazardous waste, batteries, lamps or other electrical waste; nor should it contain packaging or newspapers. These should instead be sorted out and left for material recycling. Metal that is not packaging should also be sorted out since metal is a raw material with a very high recovery value. For metals that are present in composite objects, or where it's not feasible to sort them out mechanically, WtE can provide a solution for recovering them from the bottom ash.
Gypsum should also be sorted out. Gypsum, which is a chemical compound that includes calcium and sulphur, does not contribute energy. Sulphur in the waste is a burden on flue gas purification. Therefore, there are good reasons not to put gypsum and other sulphur-containing substances in combustible waste. Requirements are set for incineration properties for the other waste delivered to the plants. For example, the waste should not have too high a moisture content or contain materials that are unsuitable for incineration. Sampling and inspection in conjunction with the waste received at the plant ensures that these requirements are met.
After combustion, residues, such as slag, remain. It consists of materials that are not combustible or do not evaporate during combustion, so-called inert material. Examples of such materials are glass, porcelain, iron scrap, gravel and more.
Sweden produces the most energy per tonne of waste in Europe; about 3 MWh per tonne. Therefore, Swedish plants meet the energy efficiency criterion (R1) well (European Commission, Directorate-General Environment, 2008).
Figure 1. Principle layout of a Waste-to-energy plant (source: CEWEP).
Environmental impact
In the combustion process, mainly carbon dioxide and water are released. The flue gases, therefore, make up 99.9 per cent of substances that are normally present in the air, i.e. nitrogen, water vapour carbon dioxide and oxygen. The remaining part consists of hydrogen chloride, nitrogen oxides, sulphur oxides and trace elements.
Due to increased emission requirements, improved combustion conditions and better control of waste; emissions of waste from waste incineration have decreased significantly in recent decades. For example, emissions to air of heavy metals from waste incineration have been reduced by close to 99 per cent since 1985. Similarly, the total emissions of dioxins into the air have decreased from about 100 g to a few grams during the same period, even though three times more waste is burned today than in 1985.
Health studies
The potential health implications of WTE and MWI (Municipal Waste Incineration) have been discussed, for a long time. Many studies have investigated the health situation. A study in Portugal investigated the levels of dioxins and furans in the blood of residents living nearby waste incinerators in Lisbon and in Madeira Island. The findings from this investigation suggest that incineration does not impact the dioxin blood levels of nearby residents (Reis, o.a., 2007). This is supported by another study in Tarragona, Spain (Vilavert, Nadal, Schuhmacher, & Domingo, 2012). The British Health Protection Agency concluded that the risk of potential cancer due to residency near municipal waste incinerators is exceedingly low and probably not measurable (Maynard, Walton, Pollitt, & Fielder, 2010).
In one of the most extensive studies so far about the risks of MWI there was no evidence for association between MWI proximity and infant health outcome (Ghosh, o.a., 2019). There are also studies that have been monitoring the effect on crops near three different MWI plants for multiple years (2004-2013). The results showed that the emissions did not affect the quality of milk from cows who had been fed cattle feed from the area in the study (van Dijk, van Doorn, & van Alfen, 2015).
Waste to Energy in a Circular Economy
There is an ongoing discussion about waste incineration, and how it might be conducive to reuse and recycling. According to the EU Framework Directive for waste and the Swedish Waste Ordinance, waste incineration with efficient energy recovery is to be regarded as waste recovery.
In a circular economy, the value of products and materials is maintained for as long as possible. Waste and resource use are minimised, and when a product has reached the end of its life, the resources are kept within the economy to be used again and again and create further value. The waste hierarchy is clear: Waste incineration is not a competitor to reuse and recycling. The value of products shall be maintained at the top of the waste hierarchy as long as possible. But when the products no longer are suitable for recycling, they still have value as fuel for heat and power production.
Figure 2. Municipal waste treatment in the European countries 2018 (source: CEWEP).
Figure 2 above shows how the waste is treated in the EU countries. It illustrates that the countries with the highest Waste-to-energy treatment also have the lowest share of landfill and the highest recycling shares. Many countries have a landfill ban or are in the process of introducing one. Besides materials that for different reasons are not suitable for material recycling such as dirty, mixed, and degraded materials; there are also materials that are contaminated in other ways that make them unsuitable for recycling. The WtE plants can destroy many of the organic pollutants and collect inorganic substances that we don't want to spread or recycle into new products.
Text by: Henrik Bristav (RISE)
Henrik Bristav (RISE Research Institutes of Sweden), mail
- Energy savings
- Green jobs
- More renewable energy
- Reduced costs
- Reduced climate impact
References:
- European Commission, Directorate-General Environment. (2008). Guidelines on the interpretation of the R1 energy efficiency formula for incineration facilities dedicated to the processing of municipal solid waste according to Annex II of Directive 2008/98/EC on waste. European Commission. Retrieved from https://ec.europa.eu/environment/waste/framework/pdf/guidance.pdf
- Ghosh, R. E., Freni-Sterrantino, A., Douglas, P., Parkes, B., Fecht, D., de Hoogh, K., . . . Hansell, A. L. (2019, January). Fetal growth, stillbirth, infant mortality and other birth outcomes near UK municipal waste incinerators; retrospective population based cohort and case-control study. Environment International, 122, pp. 151-158. doi:10.1016/j.envint.2018.10.060
- Maynard, R. L., Walton, H., Pollitt, F., & Fielder, R. (2010). The Impact on Health of Emissions to Air fron Municipal Waste Incinerators. Health Protection Agency. Retrieved from https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/335090/RCE-13_for_web_with_security.pdf
- Reis, M. F., Miguel, J. P., Sapaio, C., Aguilar, P., Melim, J. M., & Päpke, O. (2007, April). Determinants of dioxins and furans in blood of non-occupationally exposed populations living near Portuguese solid waste incinerators. Chemosphere, 67, pp. S224-S230. doi:10.1016/j.chemosphere.2006.05.102
- van Dijk, C., van Doorn, W., & van Alfen, B. (2015, March). Long term plant biomonitoring in the vicinity of waste incinerators in The Netherlands. Chemasphere, 122, pp. 45-51. doi:10.1016/j.chemosphere.2014.11.002
- Vilavert, L., Nadal, M., Schuhmacher, M., & Domingo, L. J. (2012, July 22). Long-term monitoring of dioxins and furans near a municipal solid waste incinerator: human health risks. Waste Management & Research, 30(9), pp. 909-916. doi:10.1177/0734242X12453974
External links:
- Why waste your energy? Video by European WtE.
- CEWEP – Confederation of European Waste-to-Energy Plants
Relevant Wikipedia articles:
Related Celsius content:
Webinar: Waste heat from Renova to Göteborg Energi DHC Network