Burning waste to generate energy?

Article by Isabel Key and Mina Frost.

Household waste can be burnt at ‘waste-to-energy’ power stations in order to generate energy for electricity or heating [1]. How does this work?

Waste in many forms (paper, food, plastic, metal etc. [2]) is burnt at a power station [3]. The heat created is used to evaporate water, producing steam which is then heated to about 380°C [3]. The hot steam causes a turbine to turn, which runs a machine that generates electricity [4,5].

One benefit of burning waste is that less needs to go to landfill – the burning process still produces some waste that needs to be disposed of, but the volume (amount) is reduced by about 87% [1]. It can also mean that less fossil fuel is used globally for generating energy [4]. Although it would be better not to produce the waste to start with and generate energy from low-emission sources like wind, solar and nuclear [6,7].

However, there are major disadvantages to burning as a method of waste-disposal. Firstly, when waste burns it releases carbon dioxide into the atmosphere, contributing to climate change [6]. In the future, this may be avoided by using chemical engineering to capture the CO2 released before it enters the air, but this technology is currently too expensive to be competitive [8,9].

Furthermore, burning waste releases toxic air pollutants such as sulphur dioxide [10,11] which makes rain acidic, killing trees [12], and is bad for human health, exacerbating breathing problems [13]. One study found that women exposed to more pollution from waste burning stations in Italy had a higher chance of miscarriage during childbirth [14].

Many argue that we should not be burning materials, but instead be reusing and recycling them [15,16,17]. The idea is to have a ‘circular economy’ – materials that are no longer useful can be used to make new products [18]. To achieve this, we would need a complete overhaul in how objects are manufactured and what happens to them when they are at the end of their (current) life [18].

References

[1] https://www.eia.gov/energyexplained/biomass/waste-to-energy.php

[2] https://www.epa.gov/sites/production/files/2018-07/documents/smm_2015_tables_and_figures_07252018_fnl_508_0.pdf See: Figure 17

[3] https://www.researchgate.net/figure/Schematic-of-the-waste-to-energy-WtE-plant-and-main-components-Red-dash-Grid_fig1_319994353 Download paper, and see materials and methods

[4] https://www.epa.gov/smm/energy-recovery-combustion-municipal-solid-waste-msw#HowWorks See: Energy recovery from combustion; The mass burn process

[5] https://www.bbc.co.uk/bitesize/guides/zbsdmp3/revision/1 See flow diagram – the water, turbine, generator stage of the process also applies to waste-to-energy plants

[6] https://www.ipcc-nggip.iges.or.jp/public/gp/bgp/5_3_Waste_Incineration.pdf See: Estimation of the specific emissions of a power plant mix per kWh Net, 690g CO2/kWh

[7] https://www.parliament.uk/documents/post/postpn_383-carbon-footprint-electricity-generation.pdf See: Fig 2, even the highest range bar (solar PV) emits fewer grams of CO2-equivalent (CO2 and other greenhouse gases combined) than waste-to-energy does for just CO2 (see reference [M)

[8] https://www.globalccsinstitute.com/wp-content/uploads/2019/10/Waste-to-Energy-Perspective_October-2019-5.pdf See: Waste-to-Energy + CCS

[9] https://www.mckinsey.com/~/media/mckinsey/dotcom/client_service/sustainability/cost%20curve%20pdfs/pathways_lowcarbon_economy_version2.ashx See: Exhibit 1

[10] https://onlinelibrary.wiley.com/doi/full/10.1111/jiec.12701?casa_token=9Yy-pE6BfqkAAAAA%3AG5C5SnDlK_3n8YickIBRjvjamWeXDzBfRTyKfKcAjXNUhF7ydqEWRhJMdNPQxu9p9aZVs6ZNkJTiSg

[11] https://www.sciencedirect.com/science/article/pii/S187802961630158X

[12] https://www.sciencedirect.com/science/article/pii/0269749188901868

[13] https://www.sciencedirect.com/science/article/abs/pii/S0002962915325933

[14] https://insights.ovid.com/article/00001648-201311000-00010

[15] https://theconversation.com/climate-explained-seven-reasons-to-be-wary-of-waste-to-energy-proposals-128630

[16] https://zerowasteeurope.eu/2018/02/9-reasons-why-we-better-move-away-from-waste-to-energy-and-embrace-zero-waste-instead/

[17] https://www.theguardian.com/environment/2019/feb/28/burning-issue-are-waste-to-energy-plants-a-good-idea

[18] https://www.nature.com/news/the-circular-economy-1.19594

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