Diana often took a photo of progress on the Incinerator when she cycled past.
Year: 2013
Carbon monoxide
Carbon monoxide is colourless, odourless, and tasteless, but highly toxic. It is the most common cause of fatal air poisoning in many countries.
Carbon dioxide
| Molar mass | 44.01 g/mol |
| Lifetime in atmosphere | No single lifetime can be given |
| Global Warming Potential over 100 years | 1 |
| Estimated emissions in 2008 | 51,762,916 Gg |
| Atmospheric concentration in September 2013 | 393,510,000 ppt |
Nearly all of the carbon content in incinerated waste is emitted to the atmosphere as carbon dioxide. Municipal solid waste contains approximately the same mass fraction of carbon as does carbon dioxide itself (27%), so incineration of 1 tonne of waste is estimated to produce approximately 1 tonne of carbon dioxide.
Carbon dioxide emitted by human activity is of course the main cause of global warming leading to climate change. Under the Climate Change Act 2008, the UK is committed to reduce greenhouse gas emissions from 1990 levels by at least 80% by 2050. In 1990, emissions from energy consumption were 10.5 tonnes of carbon dioxide per capita, so the target is slightly over 2 tonnes per capita.
In 2011, UK emissions from energy consumption were 8 tonnes per capita, the reduction from 1990 largely due to the replacement of coal by gas in electricity generation. The Exeter Incinerator is designed to accept up to 60,000 tonnes per year of waste, from Exeter and the immediate surrounding area in Devon. With a population of about 120,000, that means 0.5 tonnes of carbon dioxide added to every person’s carbon budget. But suppose the Incinerator replaced some carbon emissions from other energy plant……
Incinerators have electricity generation efficiencies of 14-28%. The waste heat can be used in a district heating network, giving efficiencies higher than 80%. The Exeter Incinerator will initially provide electricity to the national grid, and has the potential to export heat but only if a district heating network is established on the Marsh Barton estate.
So the Incinerator will produce electricity at a substantially lower efficiency than the rest of the national grid, and displace lower carbon alternatives.
2,3,7,8-Tetrachlorodibenzo-p-dioxin
Polychlorinated dibenzo-p-dioxins (PCDDs; known colloquially and inaccurately as dioxins) are subject to the European Waste Incineration Directive, which puts strict limits on emissions to air. Incineration is controlled to minimise their production, and the flue gas is treated post-combustion. The resulting toxic fly ash must be handled as hazardous waste.
Emissions of dioxins and furans from an incinerator typical of those currently operating in the UK (230,000 tonnes per year) are approximately equivalent to emissions from accidental fires in a town the size of Milton Keynes (population 230,000). That is, emissions from the Exeter Incinerator will be equivalent to half the emissions from accidental fires in Exeter.
The structure of dioxins comprises two benzene rings (six carbon atoms) joined by two oxygen atoms. Chlorine atoms may be attached to this structure at any of positions 1–4 and 6–9 in the above picture, which gives 75 flavours. Hydrogen atoms are attached to the remaining positions.
Dioxins are commonly regarded as highly toxic compounds that are environmental pollutants and persistent organic pollutants. Of the 75 flavours, the seven below are considered toxic by the World Health Organization (WHO). 2,3,7,8-Tetrachlorodibenzo-p-dioxin* became known as a contaminant in Agent Orange, and is the most toxic of all. It is therefore designated the reference molecule for rating toxicity.
|
Flavour (DD stands for |
Formula |
WHO Toxicity |
|
2,3,7,8-Cl4DD |
C12H4Cl4O2 |
1 |
|
1,2,3,7,8-Cl5DD |
C12H3Cl5O2 |
1 |
|
1,2,3,4,7,8-Cl6DD |
C12H2Cl6O2 |
0.1 |
|
1,2,3,7,8,9-Cl6DD |
C12H2Cl6O2 |
0.1 |
|
1,2,3,6,7,8-Cl6DD |
C12H2Cl6O2 |
0.1 |
|
1,2,3,4,6,7,8-Cl7DD |
C12HCl7O2 |
0.01 |
|
Cl8DD |
C12Cl8O2 |
0.0003 |
For more information, see the Wikipedia articles about polychlorinated dibenzodioxins and specifically 2,3,7,8-Tetrachlorodibenzo-p-dioxin.
*The ‘p’ stands for ‘para’, indicating the oxygen atoms are opposite each other. The oxygen atoms could be next to each other, which would be indicated by ‘o’ for ‘ortho’, but this molecular configuration is unstable.
2,3,4,7,8-Pentachlorodibenzofuran
Polychlorinated dibenzofurans (PCDFs; known colloquially as furans) are subject to the European Waste Incineration Directive, which puts strict limits on emissions to air. Incineration is controlled to minimise their production, and the flue gas is treated post-combustion. The resulting toxic fly ash must be handled as hazardous waste.
Emissions of dioxins and furans from an incinerator typical of those currently operating in the UK (230,000 tonnes per year) are approximately equivalent to emissions from accidental fires in a town the size of Milton Keynes (population 230,000). That is, emissions from the Exeter Incinerator will be equivalent to half the emissions from accidental fires in Exeter.
The structure of furans comprises two benzene rings (six carbon atoms) joined directly and by one oxygen atom. Chlorine atoms may be attached to this structure at any of positions 1–4 and 6–9 in the above picture, which gives 135 flavours. Hydrogen atoms are attached to the remaining positions.
Of the 135 furan flavours, the ten below exhibit dioxin-like properties and are given toxicity ratings by the World Health Organization (WHO). Furans are commonly regarded as highly toxic compounds that are environmental pollutants and persistent organic pollutants.The reference molecule for rating toxicity is 2,3,7,8-Tetrachlorodibenzo-p-dioxin.
|
Flavour (DF stands for |
Formula |
WHO Toxicity |
|
2,3,7,8-Cl4DF |
C12H4Cl4O |
0.1 |
|
1,2,3,7,8-Cl5DF |
C12H3Cl5O |
0.03 |
|
2,3,4,7,8-Cl5DF |
C12H3Cl5O |
0.3 |
|
1,2,3,4,7,8-Cl6DF |
C12H2Cl6O |
0.1 |
|
1,2,3,7,8,9-Cl6DF |
C12H2Cl6O |
0.1 |
|
1,2,3,6,7,8-Cl6DF |
C12H2Cl6O |
0.1 |
|
2,3,4,6,7,8-Cl6DF |
C12H2Cl6O |
0.1 |
|
1,2,3,4,6,7,8-Cl7DF |
C12HCl7O |
0.01 |
|
1,2,3,4,7,8,9-Cl7DF |
C12HCl7O |
0.01 |
|
Cl8DF |
C12Cl8O |
0.0003 |
For more information, see the Wikipedia article about dioxins and dioxin-like compounds.
3,3′,4,4′,5-Pentachlorobiphenyl
Polychlorinated biphenyls (PCBs, not to be confused with printed circuit boards) are not subject to the European Waste Incineration Directive, but emissions can be controlled in the same way as dioxins and furans; incineration is controlled to minimise their production, and the flue gas is treated post-combustion.
The structure comprises two joined phenyl rings (six carbon atoms). Chlorine atoms may be attached to this structure at any of positions 2-6 and 2′-6′ in the above picture, which gives 209 flavours. Hydrogen atoms are attached to the remaining positions.
Of the 209 PCB flavours, the twelve below exhibit dioxin-like properties and are given toxicity ratings by the World Health Organization (WHO). PCBs are commonly regarded as highly toxic compounds that are environmental pollutants and persistent organic pollutants.The reference molecule for rating toxicity is 2,3,7,8-Tetrachlorodibenzo-p-dioxin.
|
Flavour |
Formula |
WHO Toxicity |
|
3,3′,4,4′-Tetrachlorobiphenyl |
C12H6Cl4 |
0.0001 |
|
3,4,4′,5-Tetrachlorobiphenyl |
C12H6Cl4 |
0.0003 |
|
2,3,3′,4,4′-Pentachlorobiphenyl |
C12H5Cl5 |
0.00003 |
|
2,3,4,4′,5-Pentachlorobiphenyl |
C12H5Cl5 |
0.00003 |
|
2,3′,4,4′,5-Pentachlorobiphenyl |
C12H5Cl5 |
0.00003 |
|
2′,3,4,4′,5-Pentachlorobiphenyl |
C12H5Cl5 |
0.00003 |
|
3,3′,4,4′,5-Pentachlorobiphenyl |
C12H5Cl5 |
0.1 |
|
2,3,3′,4,4′,5-Hexachlorobiphenyl |
C12H4Cl6 |
0.00003 |
|
2,3,3′,4,4′,5′-Hexachlorobiphenyl |
C12H4Cl6 |
0.00003 |
|
2,3′,4,4′,5,5′-Hexachlorobiphenyl |
C12H4Cl6 |
0.00003 |
|
3,3′,4,4′,5,5′-Hexachlorobiphenyl |
C12H4Cl6 |
0.03 |
|
2,3,3′,4,4′,5,5′-Heptachlorobiphenyl |
C12H3Cl7 |
0.00003 |
For more information, see the Wikipedia articles about polychlorinated biphenyls and dioxins and dioxin-like compounds.
Nitrogen oxides
Nitric oxide (NO) and nitrogen dioxide (NO2) are subject to the European Waste Incineration Directive, which puts strict limits on emissions to air. But removal of nitric oxide by incinerators is only about 60% effective and the remainder may be converted to nitrogen dioxide to form smog and acid rain.
Nitrogen dioxide has a variety of health impacts, such as higher incidence of respiratory symptoms in children, asthma, chronic obstructive pulmonary disease, lung cancer, heart disease in those over 65, and abnormally elevated immune and allergic responses. When nitrogen dioxide is combined with fine particulates and carcinogenic heavy metals (in particular cadmium), the effects on lung cancer are likely to be more potent.
Nitrous oxide
| Molar mass | 44.013 g/mol |
| Lifetime in atmosphere | 121 years |
| Global Warming Potential over 100 years | 298 |
| Estimated emissions in 2008 | 10,700 Gg |
| Atmospheric concentration in September 2013 | 325,924 ppt |
Nitrous oxide is not subject to the EU Waste Incineration Directive. But it is a greenhouse gas, with a global warming potential nearly 300 times that of carbon dioxide.
Sulphur dioxide
Sulphur dioxide is subject to the European Waste Incineration Directive, which puts strict limits on emissions to air.
Sulphur dioxide, along with particulate matter, is implicated in forming winter-time smog. It can cause irritation, coughing and a feeling of chest tightness. People suffering from asthma are particularly sensitive to high sulphur dioxide concentrations.
Particulate matter
Incinerators may emit fine particles, and the EU Waste Incineration Directive puts limits on emissions to air of heavy metals, dust, and total organic carbon, among other pollutants. Therefore, incinerators operate a filtration system to control particulate emissions.
Emissions of particulate matter from an incinerator typical of those currently operating in the UK (230,000 tonnes per year) are approximately equivalent to emissions from a 5 km stretch of typical motorway. That is, emissions from the Exeter Incinerator will be approximately equivalent to the emissions from the M5 between junctions 29 and 30.
PM10 is defined as the mass of particles of less than about 10 microns (or one-hundredth of a mm) in diameter per cubic metre of air. PM2.5 is the mass of particles of less than about 2.5 microns in diameter per cubic metre of air. PM10 and PM2.5 samples from around the world can vary substantially in their chemical composition and size distribution, and it is possible that associated metals and ultrafine particles are important. Yet international and national regulations are currently framed in terms of mass concentrations instead of, say, the chemical (metallic) composition, the number of particles and total surface area of particles per unit volume of air, or the capacity of particles to generate free radicals.
Long term exposure to particles affects the risk of mortality, especially from cardiovascular disease and from lung cancer. Short-term increases in concentrations cause increases in deaths from and hospital admissions for heart attacks and respiratory disease, and related symptoms.
