This section provides a brief guide to the key waste technologies. These are the main types of treatment that can be used to deal with our waste. The following table shows the waste technologies that are included in this section, and classifies them by treatment type.
|
Treatment Type
|
Technology
|
|---|---|
| Sorting | Materials Recovery/Recycling Facilities |
| Mechanical/Biological Treatment (hybrid) | |
| Composting | Anaerobic Digestion |
| In-Vessel Composting | |
| Mechanical/Biological Treatment (hybrid) | |
| Open Windrow Composting | |
| Thermal Treatment | Gasification |
| Incineration | |
| Mechanical/Heat Treatment | |
| Pyrolysis | |
| Disposal | Landfill |
Each technology guide provides information on what waste types can be inputted into the technology, the treatment process, and the outputs. Each guide also provides summary information about the potential impacts of the technology, the regulations that apply, and sources of further information.
Please select a technology from the menu below to find out more.
Introduction
Anaerobic digestion (AD) is a managed biological process in which biodegradable waste is broken down by naturally occurring micro-organisms in the absence of oxygen to produce a stabilised residue. AD can reduce the volume of waste by approximately 60%. While it has not been used for treatment of Biodegradable Municipal Waste (BMW) in the UK, the practice is increasingly common in Europe. In Scotland there is a plant currently under construction in the Western Isles for the treatment of BMW.
AD may be combined with a range of other waste treatment technologies. It can be used after waste has been treated at an MRF separation facility, and in conjunction with waste treatment technologies for the non-organic fraction of waste.
Inputs
BMW, agricultural residues, sewage sludge, and industrial organic wastes. Food wastes may be treated only if the plant is compliant with Animal By-Products (Scotland) (SSI 2003/411). Ideally this process should treat only segregated biodegradable waste. Mixed waste can be treated by anaerobic digestion; however this may result in contamination of the liquid and solid fractions which can make them less suitable as soil conditioners or fertilisers.
Process
Waste is collected and brought to the site where it is pre-treated to remove non-biodegradable materials such as plastics, metals and stones, and shredded to a uniform size in order to aid digestion. The biodegradable materials are transferred to an enclosed, oxygen free, warmed container. Bacteria then digest the waste, which can take from 12-30 days, producing biogas. The digested matter, or digestate, is then pumped into a storage tank, where biogas continues to be produced. The residual digestate can then be separated to produce fibre and liquor, which must be refined for use in horticulture or agriculture. Material going to landfill is stabilised and compacted in order to reduce leachates, dust and odour when it is in landfill. The waste water, which is high in nitrates, should be treated.
Outputs
- 30-60% is converted to biogas, which is rich in methane and can be used to generate electricity or heat;
- Fibre, which is nutrient rich and can potentially be used as soil conditioner, though the quality of this product and the certainty of end use depends heavily on the waste input and the extent of refining;
- Liquor can potentially be used as a liquid fertiliser, though as with fibre, the quality of this product and the certainty of end use depends heavily on the waste input and the extent of refining;
- Waste water and water vapour which may be recycled for the dilution of fresh waste is sent to a wastewater treatment plant, or applied to farmland as liquid fertiliser; and
- Non-organic waste (depending on contamination of input).
|
Impacts
|
Details
|
|---|---|
| Scale | A typical small-scale plant treating 5,000tpa would have a site area of approximately 0.15ha with a maximum building height of 10m.
A typical large-scale plant treating 40,000tpa would have a site area of approximately 0.6ha with a maximum building height of 10m. |
| Siting | Small-scale plants have low profile structures and may be situated in sub-urban and rural areas. Large-scale plants resemble standard industrial buildings and would be more suited to areas allocated for commercial/industrial areas. |
| Transport | Depending on scale, this may range from 4 waste collection vehicles per day to approximately 20 per day. Mitigation measures to regulate traffic flows can be introduced, such as routing away from inappropriate roads, residential areas, and schools, in order to minimise the impact of traffic upon the locality. |
| Noise | Noise will be generated by plant operations and traffic. However, PPC regulations require that noise is limited. Mitigation measures to minimise noise can be effectively applied. |
| Air Emissions | Emissions from anaerobic digestion are low compared with other waste disposal options.
Bioaerosols – biological particles suspended in air which have the potential to cause respiratory complaints if inhaled – may be released from the anaerobic digestion process, mainly from feedstock reception and the eventual aeration of the digestate. As the main process is enclosed all emissions are well controlled. There may be a minor increase in pollution due to the increase in traffic. |
| Leachates | Waste water, if left untreated, may cause pollution if not adequately contained and treated; therefore treatment of waste water may be necessary. |
| Dust & Litter | Dust and litter can sometimes be generated when waste is loaded, unloaded, and transported. However, at a well run facility this should be minimised. |
| Odour | AD plants are contained facilities so the potential for odour is greatly reduced. However, some odour cannot be avoided with any further composting of the solid fraction. At these points in time odour can be reduced through dampening material to reduce dust particles. |
| Health | There is no clear evidence of health impacts, although some plant employees have experienced skin and respiratory problems. See Defra website for more information of health impacts. |
Regulation
- EU Landfill Directive (99/31/EC) requires a reduction in the amount of BMW to landfill.
- Integrated Pollution Prevention and Control Directive (96/61/EC) was created to prevent or minimise emissions to air, water and soil, as well as waste.
- Animal By-Products Regulation (Scotland) (SSI 2003/411) establishes health rules concerning animal by-products not intended for human consumption and applies to food waste that is composted.
- Public Participation Directive (2003/35/EC) requires that the application and decision document for a waste treatment installation permit must be made available to the public for their comment.
Further Information
Introductory:
- www.sepa.org.uk/pdf/nws/planning/leaflets/anaerobic.pdf
- www.sepa.org.uk/pdf/nws/guidance/thermal_treatment.pdf
- www.defra.gov.uk/environment/waste/wip/newtech/pdf/Intro…
- www.foe.co.uk/resource/briefings/anaerobic_digestion.pdf
Intermediate:
- www.environment-agency.gov.uk/wtd/679004/679026/679085/…
- www.energy.ca.gov/pier/renewable/biomass/anaerobic_digestion/
Detailed:
- www.defra.gov.uk/ENVIRONMENT/waste/research/health/index.htm
- www.defra.gov.uk/environment/waste/wip/newtech/pdf/advanced…
- www.mbt.landfill-site.com/AD/ad.html
- www.seas.columbia.edu/earth/wtert/sofos/Ostrem_Thesis_final.pdf
- www.communities.gov.uk/pub/713/PlanningforWasteManagement…
- www.compost.org.uk/downloads/faqs/Composting_commercial…
Introduction
The key aspect of gasification is that it is done in a low-oxygen atmosphere thus avoiding direct combustion. Gasification is the controlled combustion of waste at temperatures up to 1400oC producing a synthetic gas known as syngas which can then be used to generate electricity and/or heat. Gasification can reduce the volume of waste by up to 90%. Gasification is a relatively new technology for the treatment of Municipal Waste (MW). There are currently no gasification plants treating MW in Scotland; however there is a fully operational (but not full scale) demonstration plant in Bristol that combines both Gasification and Pyrolysis. Gasification can be combined with a range of other waste treatment technologies.
Inputs
Gasification can treat MW and other waste types including commercial and industrial waste, and clinical waste.
Process
Waste is collected and delivered to the site where it is pre-treated to remove non-combustibles such as glass and metal, remove excess moisture, and sometimes shredded to a uniform size. It is then fed into the gasification reactor where it is burnt. The unburned residue, or bottom ash, from the non-organic fraction of MW is stabilised and is deposited into a quench tank. Magnets remove any ferrous metals from the ash for recycling and the remaining ash may be recycled for use in construction. The combustion process also produces carbon which is transformed into syngas. This can be used at the plant to generate electricity and/or heat, or can be refined, using a system of scrubbers and cleaners, to produce a highly efficient gas which can be further scrubbed of pollutants for combustion on-site or transported to other energy generation sites. Gasification plants are able to operate at less than 100% of capacity and do not need to run 100% of the time, as start-up periods are relatively short, so there is flexibility when there is a decline waste availability.
Outputs
1 tonne of MW produces approximately:
- 150-300kg of ash residue for use in construction or landfill;
- 20kg of hazardous waste to landfill; and
- Syngas.
|
Impacts
|
Details
|
|---|---|
| Scale | A plant treating approximately 50,000tpa would have a site area of approximately 1-2ha with a maximum building height of 25m. The stack height will depend upon the requirements for air dispersion, but may range from 30-70m. |
| Siting | Unlike large thermal treatment facilities gasification proposals are likely to offer the opportunity to consider wider locational options in mixed use areas. Preference should be given to areas allocated for business use or traditional commercial/industrial urban area. Compatible with more intensive class 4 & 5 activities under the Use Classes Order. Existing waste sites should also be considered. |
| Transport | A plant treating 50,000tpa would require approximately 20 waste collection vehicles per day. Mitigation measures to regulate traffic flows can also be introduced, such as routing away from inappropriate roads, residential areas, and schools. |
| Noise | Noise will be generated by plant operations and traffic. However, PPC regulations require that noise is limited. Mitigation measures to minimise noise can be effectively applied. |
| Air Emissions | Research that does exist suggests that, in comparison with other forms of thermal treatment, emissions are comparable or lower. |
| Dust, Litter & Odour | There is very little practical experience of such facilities to determine whether these issues will be significant. However, at well run facilities this should be minimised. |
| Health | There is no clear evidence of health impacts, although some plant employees have experienced skin and respiratory problems. See Defra website for more information of health impacts. |
Regulation
- EU Landfill Directive (99/31/EC) requires a reduction in the amount of BMW to landfill. The Directive also requires Member States to set up a national strategy for the implementation of these targets.
- Integrated Pollution Prevention and Control Directive (96/61/EC) was created to prevent or minimise emissions to air, water and soil, as well as waste.
- Waste Incineration (Scotland) Regulations (SSI 2003 No170) introduced strict regulatory controls and set minimum technical requirements for waste incinerators.
- Public Participation Directive (2003/35/EC) requires that the application and decision document for a waste treatment installation permit must be made available to the public for their comment.
Further Information
Introductory:
- www.defra.gov.uk/environment/waste/wip/newtech/pdf/advancedthermaltreat.pdf
- www.sepa.org.uk/pdf/nws/guidance/thermal_treatment.pdf
Intermediate:
- www.environment-agency.gov.uk/wtd/679004/679021/679065/?version=1&lang=_e
- www.foe.co.uk/resource/briefings/gasification_pyrolysis.pdf
- www.mbt.landfill-site.com/Pyrolysis___Gasification/pyrolysis___gasification.html
- www.environment-agency.gov.uk/wtd/679004/679021/679065/?lang=_e
Detailed:
- www.defra.gov.uk/ENVIRONMENT/waste/research/health/index.htm
- www.wasteresearch.co.uk/ade/efw/gassification.htm
- www.communities.gov.uk/pub/713/PlanningforWasteManagement…
Introduction
Incineration is the controlled combustion of waste including energy recovery. Heat released from the combustion can be recovered and used to generate electricity, heat, steam or hot water; this process is often known as Energy from Waste (EfW). Incineration can reduce the volume of waste by up to 90% and reduces the hazardousness of waste. It is a common technology in Europe, and there are a number of plants operating in the UK including a small-scale plant in Lerwick, Shetland and a large-scale plant in Dundee. Incineration may be combined with a range of other waste treatment technologies.
Inputs
Incineration can treat a wide range of waste types including Municipal Waste (MW), industrial waste, and Refuse Derived Fuel (RDF). While large-scale plants can treat unsorted waste, small-scale plants are specifically designed to take a relatively homogenous, pre-processed feedstock.
Process
Waste is collected and delivered to the site where it is deposited in a bunker and mixed to ensure a more consistent and even calorific mix. It is then fed into a furnace where it is burned. Small-scale plants may require an initial injection of auxiliary fuel to start up. There are a number of different furnace designs: the furnace may use oscillation, rotation, or a grate system to ensure a more even burn, or may use fluidised beds to create turbulence in order to maximise combustion of waste. The unburned residue, known as bottom ash, is stabilised and is deposited into a tank. Magnets remove any ferrous metals from the ash for recycling, and the remaining ash can be recycled for use in construction. The hot gasses produced during combustion are then directed to a boiler where electricity can be generated and heat recovered. Gases are thoroughly cleaned using a range of emission control systems before they are emitted to the atmosphere. Filtered particles are collected and sent to special waste landfill. Under the Waste Incineration (Scotland) Regulations 2003 all emissions are continuously monitored.
Outputs
1 tonne of MW produces approximately:
- 30-60kg of hazardous waste for landfill;
- 200-300kg of bottom ash for landfill;
- 30-50kg of metals extracted from bottom ash for recycling;
- waste water for treatment via a sewage treatment plant;
- Electricity and Heat: approximately 2,000 kilowatt hours of heat per tonne of waste can be recovered, of which 90% is available for export once a certain fraction has been used for running the plant; and
- Emissions.
|
Impacts
|
Details
|
|---|---|
| Scale | A typical small-scale plant treating up to 90,000tpa would have a site area less than 2ha, with a maximum building height of 25m.
A typical large-scale plant treating approximately 400,000tpa would have a site area of approximately 5ha, with a maximum building height of 30m. The stack height for both small and large-scale plants may be very similar, around 40-70m, due to requirements for air dispersion. |
| Siting | Preference should be given to areas allocated for business use or in traditional commercial industrial urban areas. Existing waste sites should also be considered . |
| Transport | Depending on scale, this may range from 20-50 waste collection vehicles per day (for a plant treating 50,000tpa). If the plant is directly linked to an industrial operation waste import will be nil.
Mitigation measures to regulate traffic flows can also be introduced, such as routing away from inappropriate roads, residential areas, and schools, in order to minimise the impact of traffic upon the locality. |
| Noise | Noise will be generated by plant operations and traffic. However, PPC regulations require that noise is limited. Mitigation measures to minimise noise can be effectively applied. |
| Air Emissions | Incineration plants have reduced emissions over the last ten years by a factor of 10 or more as a result of changes in regulation. Current carbon dioxide emissions from EfW contribute 1.6% of UK total. Methane emissions are 0.002% UK total.
Materials such as heavy metals will be retained in the bottom ash, or in the air cleaning system or emitted to atmosphere. There may be a minor increase in pollution due to the increase in traffic. |
| Dust & Litter | Dust and Litter are sometimes generated when waste is loaded, unloaded, and transported. However, at well run facilities this should be minimised. |
| Odour | Some odour cannot be avoided at waste treatment facilities, especially in delivery stages. At these points in time odour can be reduced through dampening material to reduce dust particles. New plants minimise odour through enclosing the process, maintaining negative pressure and filtering air. |
| Health | Dioxins, which are formed by the burning of chemicals that contain chlorine, are harmful to human health. Research has shown that, since 1992, there has been a 70% reduction in the amount of dioxins released into the environment. Since 1990 there has been a 98% reduction of emissions with potential harm to health from the thermal treatment of MW. See Defra website for more information of health impacts. |
Regulation
- EU Landfill Directive (99/31/EC) requires a reduction in the amount of BMW to landfill. The Directive also requires Member States to set up a national strategy for the implementation of these targets.
- Integrated Pollution Prevention and Control Directive (96/61/EC) was created to prevent or minimise emissions to air, water and soil, as well as waste.
- Waste Incineration (Scotland) Regulations (SSI 2003/170) introduced strict regulatory controls, whereby all emissions are constantly monitored, and minimum technical requirements for waste incinerators have been established.
- Public Participation Directive (2003/35/EC) requires that the application and decision document for a waste treatment installation permit must be made available to the public for their comment.
- Animal By-Products Regulation (Scotland) (SSI 2003/411) establishes health rules concerning animal by-products not intended for human consumption and applies to food waste that is composted.
Further Information
Introductory:
- www.defra.gov.uk/environment/waste/wip/newtech/pdf/intro…
- www.sepa.org.uk/pdf/nws/guidance/thermal_treatment.pdf
Intermediate:
- www.r-p-a.org.uk/portal_group_view.fcm?groupid=4
- www.esauk.org/work/briefings/efw.asp
- www.environment-agency.gov.uk/wtd
- www.mbt.landfill-site.com/EfW/efw.php
Detailed:
- www.defra.gov.uk/ENVIRONMENT/waste/research/health/index.htm
- www.communities.gov.uk/pub/713/PlanningforWasteManagement…
Introduction
In-Vessel Composting (IVC) is a managed process in which biodegradable waste is broken down by naturally occurring micro-organisms with oxygen to produce a stabilised residue known as compost. There are several IVC plants in the UK including one in Lanarkshire, two in Aberdeenshire, one in Fife, three in Argyll & Bute, and one under construction in Highland.
IVC can be combined with a range of other waste treatment technologies. It can be used after waste has been treated at a Materials Recovery/Recycling Facility (MRF) and in conjunction with waste treatment technologies for the non-organic fraction of waste.
Inputs
Biodegradable municipal waste (BMW), agricultural waste and food processing wastes. Food wastes may be treated only if the plant is compliant with Animal By-Products (Scotland) (SSI 2003/411). Ideally this process should treat only segregated biodegradable waste. Mixed waste can be treated by anaerobic digestion; however this may result in contamination of the liquid and solid fractions which can make them less suitable as soil conditioners or fertilisers.
Process
Waste is collected and brought to the site where it is initially sorted to remove any non-biodegradable waste and shredded to a consistent size. It is then put into a closed reactor where the composting process is speeded up through the management of water, air and heat. This process typically takes between 7 and 21 days. The material is then subject to another screening to remove any traces of metals, and goes through a further maturation period of up to 10 weeks. It can then be used as compost or soil conditioner.
Outputs
1 tonne of MW produces approximately:
- 200-300kg of emissions (mainly water vapour and carbon dioxide (CO2));
- 500kg-600kg of compost;
- 50-300kg remainder to landfill (depending on contamination level of waste); and
- 200kg of wastewater which can be treated or reused on site or treated at a sewage treatment works.
|
Impacts
|
Details
|
|---|---|
| Scale | A typical large-scale plant treating 200,000tpa would have a site area of approximately 5-6 ha.
A typical medium-scale plant treating 25,000tpa would have a site area of approximately 1-2ha with a maximum building height of 5m. |
| Siting | Enclosed facilities are suited to areas allocated for business use and traditional commercial/industrial urban areas, and are compatible with the more intensive Class 4 and 5 activities under the Use Classes Order. Existing waste sites should also be considered for this type of composting facility. |
| Transport | Although there will be an increase in traffic, measures to regulate traffic flows can be introduced in order to minimise the impact of traffic upon the locality. |
| Noise | Noise will be generated by plant operations and traffic. However, PPC regulations require that noise is limited. Mitigation measures to minimise noise can be effectively applied. |
| Air Emissions | Bioaerosols (biological particles suspended in air which have the potential to cause respiratory complaints if inhaled) may be released from the composting process, mainly from feedstock reception and the eventual aeration of the digestate. However, Environment Agency research suggests that bioaerosol levels are likely to be equal to or below natural levels within 250 metres of a composting operation.
There may be a minor increase in pollution due to the increase in traffic. |
| Leachates | Leachate not re-circulated in the process should be collected and treated. Leachate, if left untreated, may cause pollution if not adequately contained and treated, therefore treatment of waste water may be necessary. |
| Dust & Litter | Dust and litter can sometimes be generated when waste is loaded and unloaded. |
| Odour | Some odour cannot be avoided with composting facilities, especially in delivery stages. At these points in time, odour can be reduced through dampening material to reduce dust particles. Because the process is covered, the potential for odour to be a nuisance is largely avoided. |
| Health | There is no clear evidence of health impacts, although some plant employees have experienced skin and respiratory problems. See Defra website for more information on health impacts. |
Regulation
- EU Landfill Directive (99/31/EC) requires a reduction in the amount of BMW to landfill.
- Integrated Pollution Prevention and Control Directive (96/61/EC) was created to prevent or minimise emissions to air, water and soil, as well as waste.
- European Standards, PAS100 and EU Class-1 compost quality control standards.
- Public Participation Directive (2003/35/EC) requires that the application and decision document for a waste treatment installation permit must be made available to the public for their comment.
- Animal By-Products Regulation (Scotland) (SSI 2003/411) establishes health rules concerning animal by-products not intended for human consumption and applies to food waste that is composted.
Further Information
Introductory:
- www.sepa.org.uk/pdf/nws/planning/leaflets/invess_compost.pdf
Intermediate:
- www.mbt.landfill-site.com/Composting/composting.html
Detailed:
- www.defra.gov.uk/ENVIRONMENT/waste/research/health/index.htm
- www.compost.org.uk/downloads/faqs/Composting_commercial…
- www.communities.gov.uk/pub/713/PlanningforWasteManagement…
Introduction
Landfill is the disposal of waste into or onto land. Today, landfill sites are constructed and operated to strict technical standards in order to reduce environmental effects. In 2005 there were 190 landfill sites in operation in Scotland.
Inputs
Most types of waste may be disposed of via landfill; however the EU Landfill Directive 1999/31/EC requires that Landfill sites must now be classified as either hazardous, non-hazardous, or inert. Reducing the amount of waste to landfill is currently being encouraged by the Landfill Directive to recover value from waste and develop more sustainable waste management.
Process
When waste is received it is weighed and checked to ensure it is compliant with its landfill operating licence. It is then tipped into the landfill, compacted and covered to prevent odour, litter, and pest infestations. The waste will then be gradually decomposed by microbes. This decomposition process, mixed with rainwater creates leachates and gas, which are both taken out of the landfill through a system of pipes. The leachates are then usually taken for treatment, while the gas, mainly a mix of carbon dioxide and methane, may be burnt off or used in an on-site energy generation plant which contributes energy to the national grid. When landfill has reached maximum capacity it is covered completely with an engineered cap, e.g. using clay and restored using soils or other covering materials so that the sites can be used for agriculture, amenities or nature conservation.
Outputs
- Landfill Gas (primarily methane (CH4) and carbon dioxide (CO2), which may be burned for energy.
- Leachates (a liquor resulting from water passing through the waste mass).
|
Impacts
|
Details
|
|---|---|
| Scale | A typical small-scale landfill treating 10,000tpa would have a site area of approximately 1-2ha.
A typical large-scale landfill treating 1,000,000tpa would have a site area of approximately 100ha. |
| Siting | Landfills are usually sited in rural areas due to their requirement for a relatively large area of void land. Sites should avoid residential and commercial areas. |
| Transport | This depends largely on the scale of the landfill; for an operation landfilling 250,00tpa there would be approximately 50 deliveries per day. Mitigation measures to regulate traffic flows can also be introduced, such as routing away from inappropriate roads, residential areas, and schools, in order to minimise the impact of traffic upon the locality. |
| Noise | Noise will be generated by plant operations and traffic. However, regulations require that noise is limited. Mitigation measures to minimise noise can be effectively applied. |
| Air Emissions | The amounts of Greenhouse Gasses emitted from landfill contribute significantly to climate change. In 2004 landfill contributed 31% of the UK’s methane emissions. Landfill sites can implement techniques to capture emissions in order to carry out controlled burning. There may also be a minor increase in emissions due to the increase in traffic. |
| Leachates | Leachates may contaminate water supplies; however this may be prevented by lining landfill sites and collecting leachates for treatment. |
| Dust & Litter | Dust and litter can sometimes be generated when waste is loaded and unloaded. Litter may also be a further problem on site and for neighbouring areas if not adequately managed. |
| Odour | Some odour cannot be avoided, especially when loading and transporting waste. However, a number of techniques can be utilised in order to reduce odour. |
| Health | Several studies have been undertaken to investigate the link between landfill sites and health. While correlations have been found, it is not certain that the landfill site is responsible for the health problems. See www.sahsu.org/pdf/techreportv6.pdf for more information. |
Regulation
- EU Landfill Directive (99/31/EC) requires a reduction in the amount of BMW to landfill, the segregation of hazardous and non-hazardous waste, and pre-treatment of waste prior to landfill.
- Scotland’s National Waste Plan aims to reduce MW to landfill from 90% to 30% by 2020.
Further Information
Introductory:
- www.sepa.org.uk/pdf/nws/promotion/landfills.pdf
Intermediate:
- www.netregs.gov.uk/netregs/275207/663559/?version=1&lang=_e
- www.sepa.org.uk/nws/data/returns.htm
- www.environment-agency.gov.uk/yourenv/eff/1190084…
Detailed:
- www.defra.gov.uk/ENVIRONMENT/waste/research/health/index.htm
- www.integra.org.uk/facts/extrafacts/landfill.html
Introduction
Materials Recovery/Recycling Facilities (MRFs) are locations where waste undergoes treatment to be separated and sorted mechanically and/or manually. There are a number of MRF sites in Scotland including one in Aberdeen and one in Grangemouth. MRFs can be used as a preliminary waste treatment process and combined with a range of other waste treatment technologies.
Inputs
The waste input depends upon the type of MRF facility. “Clean” MRF facilities processes dry recyclables only, while “dirty” MRF facilities can process mixed municipal waste and some industrial waste. Dirty MRF is also associated with Mechanical Biological Treatment MBT, due to the possible similarities in the way in which dirty MRF and MBT separate mixed waste. MRF facilities in the UK tend to be clean MRF facilities, and it is unlikely that dirty MRF facilities will be introduced.
Process
Waste is deposited at the plant where it is then separated through a system of conveyer belts, screening and other sorting systems. The type of separation process utilised depends largely on both input and after use of the separated materials. After the materials have been sorted they can then be bulked and then transported for further processing.
Outputs
Depending on input, for every 1 tonne of waste there is approximately:
- 400-970kg of recyclable material. Dirty MRF will typically recover 100-150kg of material that is recyclable;
- 250-400kg of material for biological treatment usually by composting or anaerobic digestion. Organic outputs from a dirty MRF will usually be contaminated and of limited value; and
- 30-710kg waste to landfill.
|
Impacts
|
Details
|
|---|---|
| Scale | A typical plant treating 50,000tpa would have a site area of approximately 1-2ha with a building height of 12m. |
| Siting | Preference should be given to industrial or degraded sites or sites on or close to existing waste management facilities. Where possible facilities should be located at least 100 metres from sensitive properties. |
| Transport | This depends largely on the scale of the plant; for a plant treating 50,00tpa there would be approximately 20-30 deliveries per day. Mitigation measures to regulate traffic flows can also be introduced, such as routing away from inappropriate roads, residential areas, and schools, in order to minimise the impact of traffic upon the locality. |
| Noise | Noise will be generated by plant operations and traffic. However, PPC regulations require that noise is limited. Mitigation measures to minimise noise can be effectively applied. |
| Air Emissions | There may be some increased pollution as a result of transportation. |
| Leachates | As most facilities are under cover and on concrete hard standing leachates are unlikely to cause a problem. |
| Dust & Litter | Mixed waste, including paper and plastics may result in litter problems. However, carrying out the process indoors should control problems associated with dust and litter. These processes should be carried out indoors. |
| Odour | Some odour cannot be avoided, especially when loading and transporting waste. However, a number of techniques can be utilised in order to reduce odour. |
| Health | There is no clear evidence of health impacts. See Defra website for more information of health impacts. |
Regulation
- EU Landfill Directive (99/31/EC) requires a reduction in the amount of BMW to landfill.
- Integrated Pollution Prevention and Control Directive (96/61/EC) was created to prevent or minimise emissions to air, water and soil, as well as waste.
- Public Participation Directive (2003/35/EC) requires that the application and decision document for a waste treatment installation permit must be made available to the public for their comment.
Further Information
Introductory:
- www.torbay.gov.uk/index/environment-planning/waste/recycling/mrf.htm
- www.defra.gov.uk/environment/waste/wip/newtech/pdf/intro…
Intermediate:
- www.sepa.org.uk/pdf/nws/planning/leaflets/mat_recovery.pdf
- www.mbt.landfill-site.com/Dirty_MRF/dirty_mrf.html
- www.mbt.landfill-site.com/MRF/mrf.html
Detailed:
- www.defra.gov.uk/ENVIRONMENT/waste/research/health/index.htm
- www.communities.gov.uk/pub/713/PlanningforWasteManagement…
Introduction
Mechanical/Biological Treatment (MBT) is a hybrid treatment which combines biological and mechanical techniques, and may also use techniques to produce Refuse Derived Fuel (RDF). MBT can reduce the volume of waste to landfill by around 20% depending on the input, improves the quality of recyclable materials, and stabilises waste. There are over 70 MBT plants working in Europe, and there are a number of MBT plants operating in the UK including three in Argyll and Bute. MBT may be combined with a range of other waste treatment technologies.
Inputs
Unsorted Municipal Waste and non-hazardous waste. MBT is sometimes referred to as “dirty MRF” as it processes mixed household waste. This is in contrast to “clean MRF” which is associated with processing of dry recyclables.
Process
The MBT process and outputs depends greatly upon the needs of the recipients of the outputs and the availability and access to markets for the outputs. However, the process generally follows one of two routes. Waste is collected and brought to the site where it can then be treated mechanically then biologically, or biologically then mechanically. Waste is treated mechanically in order to reduce its volume and separate it into different waste types. The biodegradable fraction of the waste is treated in a managed biological process in which it is broken down by naturally occurring micro-organisms. The organic output may have a higher level of contaminants (for example plastics and glass) than other biological treatment processes which only treat BMW, such as Open Windrow Composting or Anaerobic Digestion.
Outputs
1 tonne of MW produces approximately:
- 250kg Water Vapour & CO2;
- 35-345kg recyclable materials;
- 500kg organic output – use as compost is dependent on quality of the material. This material may also be used to make refuse derived fuel (RDF);
- 100-200kg of residual waste to landfill;
- Wastewater.
|
Impacts
|
Details
|
|---|---|
| Scale | A typical plant treating 50,000tpa would have a site area of approximately 1-2ha with a maximum building height of 20m. |
| Siting | Preference should be given to industrial or degraded sites or sites on or close to existing waste management facilities. |
| Transport | This depends largely on the scale of the plant; for a plant treating 50,00tpa there would be approximately 20-30 deliveries per day. Mitigation measures to regulate traffic flows can also be introduced, such as routing away from inappropriate roads, residential areas, and schools, in order to minimise the impact of traffic upon the locality. |
| Noise | Noise will be generated by plant operations and traffic. However, PPC regulations require that noise is limited. Mitigation measures to minimise noise can be effectively applied. |
| Air Emissions | Bioaerosols (biological particles suspended in air which have the potential to cause respiratory complaints if inhaled) may be released from the anaerobic digestion process, mainly from feedstock reception and the eventual aeration of the digestate.
There may be a minor increase in pollution due to the increase in traffic. |
| Leachates | Waste water, if left untreated may cause pollution. However appropriate treatment will prevent any serious water pollution. |
| Dust & Litter | Dust and litter are sometimes generated when waste is loaded, unloaded, and transported. However, at a well run facility this should be minimised. |
| Odour | Some odour cannot be avoided, especially when loading and transporting waste. However, a number of techniques can be utilised in order to reduce odour. |
| Health | There is no clear evidence of health impacts. However, DEFRA have identified the need for further research into the effects of emissions of particulates from MBT. See Defra website for more information of health impacts. |
Regulation
- EU Landfill Directive (99/31/EC) requires a reduction in the amount of BMW to landfill.
- Integrated Pollution Prevention and Control Directive (96/61/EC) was created to prevent or minimise emissions to air, water and soil, as well as waste.
- Public Participation Directive (2003/35/EC) requires that the application and decision document for a waste treatment installation permit must be made available to the public for their comment.
- Animal By-Products Regulation (Scotland) (SSI 2003/411) establishes health rules concerning animal by-products not intended for human consumption and applies to food waste that is composted.
Further Information
Introductory:
- www.sepa.org.uk/pdf/nws/planning/leaflets/mech_bio.pdf
- www.defra.gov.uk/environment/waste/wip/newtech/mechbiotreat.pdf
Intermediate:
- www.sepa.org.uk/pdf/nws/planning/leaflets/mat_recovery.pdf
- www.mbt.landfill-site.com/Dirty_MRF/dirty_mrf.html
- www.mbt.landfill-site.com/MRF/mrf.html
Detailed:
- www.defra.gov.uk/ENVIRONMENT/waste/research/health/index.htm
- www.communities.gov.uk/pub/713/PlanningforWasteManagement…
- www.defra.gov.uk/environment/waste/wip/newtech/pdf/advancedbiotreat.pdf
- www.environment-agency.gov.uk/commondata/acrobat/mbt_output_guidance_1149762.pdf
Introduction
Mechanical/Heat treatment (MHT), including techniques such as autoclaving, is a treatment process which incorporates heat using steam (either wet or dry) with or without pressure, alongside a number of separation techniques. MHT reduces the volume of waste by 60/70%, stabilises waste and produces material suitable for energy generation. MHT is a relatively new technology for the treatment of Municipal Waste, though there are a number of demonstration plants operating in the UK. MHT can be combined with a range of other waste treatment technologies.
Inputs
Unsorted or separated Municipal Waste, commercial waste, clinical waste, animal by-products and certain industrial wastes.
Process
Waste is collected and brought to the site where it is placed in a pressurised container called an autoclave and then “cooked” using steam for about 90 minutes at a temperature of 160oC. The process is effective in killing off viruses and pathogens and transforming the physical characteristics of the waste. The waste is then easily separable into recyclates, Refuse Derived Fuel (RDF) and organic fibre. After separation glass, metals and plastics are cleaned and can then be sent on for further treatment. RDF can be used for energy generation. The organic fibre requires further treatment for use as compost.
Outputs
- Organic fibre, which can be blended and used as a soil conditioner
- Recyclable materials
- RDF may also be produced from the organic fibre and residual waste
|
Impacts
|
Details
|
|---|---|
| Scale | Plant size may be variable. A typical plant treating 100,000tpa would have a site area of approximately 1.8 hectares. |
| Siting | Preference should be given to industrial or degraded sites or sites on or close to existing waste management facilities. |
| Transport | A plant treating 50,000tpa would require approximately 20 waste collection vehicles per day. Mitigation measures to regulate traffic flows can also be introduced, such as routing away from inappropriate roads, residential areas, and schools. |
| Noise | Noise will be generated by plant operations and traffic. However, PPC regulations require that noise is limited. Mitigation measures to minimise noise can be effectively applied. |
| Air Emissions | There is not sufficient data in the UK of emissions. However, they are not likely to vary from emissions from other similar processes, such as MBT. There may be a minor increase in pollution due to the increase in traffic. |
| Leachates | Steam may be recycled in the process, so the output of contaminated water may not be large. However, careful management of water will be required. |
| Dust & Litter | Dust and Litter are sometimes generated when waste is loaded, unloaded, and transported. However, at a well run facility this should be minimised. |
| Odour | Some odour cannot be avoided, especially when opening and the subsequent cooling. However, a number of techniques can be utilised in order to reduce odour. |
| Health | There is not sufficient data in the UK on potential health impacts. |
Regulation
- EU Landfill Directive (99/31/EC) requires a reduction in the amount of BMW to landfill.
- Integrated Pollution Prevention and Control Directive (96/61/EC) was created to prevent or minimise emissions to air, water and soil, as well as waste.
- Public Participation Directive (2003/35/EC) requires that the application and decision document for a waste treatment installation permit must be made available to the public for their comment.
- Animal By-Products Regulation (Scotland) (SSI 2003/411) establishes health rules concerning animal by-products not intended for human consumption and applies to food waste that is composted.
- Waste Incineration (Scotland) Regulations (SSI 2003 No170) introduced strict regulatory controls and set minimum technical requirements for waste incinerators.
Further Information
Intermediate:
- www.environment-agency.gov.uk/wtd/679004/679032/679093…
Detailed:
- www.defra.gov.uk/ENVIRONMENT/waste/research/health/index.htm
- www.defra.gov.uk/environment/waste/wip/newtech/pdf/Mech…
Introduction
Open Windrow Composting (OWC) is a managed biological process in which biodegradable waste is broken down by naturally occurring micro-organisms to produce a stabilised residue. There are currently a number of OWCs operating in Scotland, including one at Deerdykes in Cumbernauld.
OWC can be combined with a range of other waste treatment technologies. It can be used after waste has been treated at an MRF separation facility, and in conjunction with waste treatment technologies for the non-organic fraction of waste.
Inputs
Biodegradable Municipal Waste (BMW). Only meat excluded food wastes can be treated, as stipulated by the Animal By-Products (Scotland) (SSI 2003/411) Regulations. Ideally this process should treat only segregated biodegradable waste. Mixed waste can be treated by anaerobic digestion; however this may result in contamination of the liquid and solid fractions which can make them less suitable as soil conditioners or fertilisers.
Process
Waste is collected and brought to the site where it is checked to ensure it is of sufficient quality. It is then shredded and piled into windrows, which are elongated piles shaped for ideal composting. Aeration is encouraged by suitable mixing of the initial material and regular mechanical agitation (turning). Decomposition is allowed to continue until the waste has been stabilised and matured. Before use, the compost is checked for contaminants to ensure that it fulfils the physical, chemical and biological requirements for commercial compost.
Outputs
1 tonne of BMW will produce approximately:
- 200-300kg of gas emissions including CO2, Water vapour and methane;
- 500-750kg of compost – use dependent on quality of the material; and
- 50-300kg of residual waste to landfill.
|
Impacts
|
Details
|
|---|---|
| Scale | A typical large-scale plant treating 25,000tpa would have a site area of approximately 2-3 ha. The height of windrows is usually no more than 3m high. Dependent on type of windrow turning machinery used. |
| Siting | Traditional windrow composting plants can blend in with suburban and rural development due primarily to their low profile structures and their similarity to other rural developments (eg farms). Such facilities would not normally be compatible with a hi-tech business park environment or an urban setting. Existing waste sites should also be considered for this type of composting facility. |
| Transport | A plant treating 25,000tpa would require approximately 20-40 waste collection vehicles per day. Mitigation measures to regulate traffic flows can also be introduced, such as routing away from inappropriate roads, residential areas, and schools. |
| Noise | Noise will be generated by plant operations and traffic. However, PPC regulations require that noise is limited. Mitigation measures to minimise noise can usually be effectively applied. |
| Air Emissions | Bioaerosols – biological particles suspended in air which have the potential to cause respiratory complaints if inhaled – may be released from the process, mainly from feedstock reception and aeration of the windrow.
There may be a minor increase in pollution due to the increase in traffic. |
| Leachates | Waste water, if left untreated, may cause pollution if not adequately contained and treated. Treatment of waste water may be necessary. |
| Dust & Litter | There is a potential for some dust and litter to present a problem. However, this can be mitigated by maintaining moisture levels so as to reduce dust, and restricting movement of the waste to when wind-levels are low. |
| Odour | Some odour cannot be avoided with composting facilities, especially in delivery stages. Odour can be reduced by prompt processing of the input material. Odour produced during the decomposition process can be reduced by maintaining aerobic conditions within the windrow. |
| Health | No clear evidence of health impacts. See Defra website for more information of health impacts. |
Regulation
- EU Landfill Directive (99/31/EC) requires a reduction in the amount of BMW to landfill.
- Integrated Pollution Prevention and Control Directive (96/61/EC) was created to prevent or minimise emissions to air, water and soil, as well as waste.
- Public Participation Directive (2003/35/EC) requires that the application and decision document for a waste treatment installation permit must be made available to the public for their comment.
- Animal By-Products Regulation (Scotland) (SSI 2003/411) establishes health rules concerning animal by-products not intended for human consumption and applies to food waste that is composted.
Further Information
Introductory:
- www.defra.gov.uk/environment/waste/wip/newtech/pdf/Intro…
Intermediate:
- www.sepa.org.uk/pdf/nws/planning/leaflets/windrow.pdf
- www.mbt.landfill-site.com/Composting/composting.html
- www.letsrecycle.com/materials/composting/news.jsp?story=5785
- www.defra.gov.uk/environment/waste/wip/newtech/pdf/advancedbiotreat.pdf
Detailed:
- www.defra.gov.uk/ENVIRONMENT/waste/research/health/index.htm
- www.communities.gov.uk/pub/713/PlanningforWasteManagement…
- www.compost.org.uk/downloads/faqs/Composting_commercial…
Introduction
Pyrolysis is the controlled combustion of waste in the complete or partial absence of oxygen at temperatures between 400ºC and 800ºC. It reduces the volume of waste by approximately 90%, and produces gas for energy generation. Pyrolysis is a relatively new technology for the treatment of Municipal Waste (MW). There are currently no pyrolysis plants treating MW in Scotland; however there is a fully operational (but not full scale) demonstration plant in Bristol that combines both Gasification and Pyrolysis. Pyrolysis can be combined with a range of other waste treatment technologies.
Inputs
Pyrolysis can treat MW and other waste types including commercial and industrial waste, and clinical waste.
Process
Waste is collected and delivered to the site where it is pre-treated to remove non-combustibles such as glass and metal, remove excess moisture, and sometimes shredded to a uniform size. It is then fed into the pyrolysis reactor where it is burnt, or “pyrolysed”. The unburned residue, or char, from the non-organic fraction of MW is stabilised and is deposited into a quench tank. Magnets remove any ferrous metals from the ash for recycling and the remaining ash may be recycled for use in construction. The combustion process also produces carbon which is transformed into syngas. This can be refined, using a system of scrubbers and cleaners in order to remove tar, sulphur compounds and other acid gases, which are then sent to landfill. This produces a highly efficient gas for combustion on-site or transported to other energy generation sites.
Outputs
1 tonne of BMW will produce approximately:
- 200-300kg of char for use in construction or landfill;
- 20kg of hazardous waste for landfill; and
- Syngas. This provides a high efficiency energy generation in comparison with other heat treatment facilities, due to the degree of refinement of the syngas.
|
Impacts
|
Details
|
|---|---|
| Scale | A plant treating approximately 50,000tpa would have a site area of approximately 1-2ha, with a maximum building height of 25m. The stack height will depend upon the requirements for air dispersion, but may range from 30-70m. |
| Siting | Unlike large thermal treatment facilities pyrolysis proposals are likely to offer the opportunity to consider wider locational options in mixed use areas. Preference should be given to areas allocated for business use or traditional commercial/industrial urban area. Compatible with more intensive class 4 & 5 activities under the Use Classes Order. Existing waste sites should also be considered. |
| Transport | A plant treating 50,000tpa would require approximately 20 waste collection vehicles per day. Mitigation measures to regulate traffic flows can also be introduced, such as routing away from inappropriate roads, residential areas, and schools. |
| Noise | Noise will be generated by plant operations and traffic. However, PPC regulations require that noise is limited. Mitigation measures to minimise noise can be effectively applied. |
| Air Emissions | Very little research has been undertaken in the UK on the air emissions associated with gasification systems. One study shows that Pyrolysis gives rise to a relatively low quantity of solid residue per tonne processed, about half the quantity produced by mass burn incineration.
There may be a minor increase in pollution due to the increase in traffic. |
| Dust, Litter & Odour | There is very little practical experience of such facilities to determine whether these issues will be significant. However at well run facilities this should be minimised. |
| Health | There is no clear evidence of health impacts. See Defra website for more information of health impacts. |
Regulation
- EU Landfill Directive (99/31/EC) requires a reduction in the amount of BMW to landfill.
- Integrated Pollution Prevention and Control Directive (96/61/EC) was created to prevent or minimise emissions to air, water and soil, as well as waste.
- Public Participation Directive (2003/35/EC) requires that the application and decision document for a waste treatment installation permit must be made available to the public for their comment.
- Animal By-Products Regulation (Scotland) (SSI 2003/411) establishes health rules concerning animal by-products not intended for human consumption and applies to food waste that is composted.
- Waste Incineration (Scotland) Regulations (SSI 2003 No170) introduced strict regulatory controls and set minimum technical requirements for waste incinerators.
Further Information
Introductory:
- www.defra.gov.uk/environment/waste/wip/newtech/pdf/advancedthermaltreat.pdf
Intermediate:
- www.environment-agency.gov.uk/wtd/679004/679021/679047/?version=1&lang=_e
- www.mbt.landfill-site.com/Pyrolysis___Gasification/pyrolysis___gasification.html
- www.sepa.org.uk/pdf/nws/planning/leaflets/gas_pyro.pdf
Detailed:
- www.communities.gov.uk/pub/713/PlanningforWasteManagement…
- www.defra.gov.uk/ENVIRONMENT/waste/research/health/index.htm
For an alternative technology, please select one from the menu below.
Images used in this section were taken from the following sources:
www.sepa.org.uk/pdf/nws/planning/leaflets/anaerobic.pdf
www.naftc.wvu.edu/NAFTC%20eNews/November%2005/altethanol.html
www.sepa.org.uk/pdf/nws/planning/leaflets/invess_compost.pdf
www.sepa.org.uk/pdf/nws/promotion/landfills.pdf
www.sepa.org.uk/pdf/nws/planning/leaflets/mech_bio.pdf
www.habmigern2003.info/biogas/Pyrolysis-
www.communities.gov.uk/pub/713/PlanningforWasteManagementFacilitiesAResearchStudy_id1145713.pdf
  |
||
| © 2008 Waste Aware Scotland | Islay House, Livilands Lane, Stirling, FK8 2BG Tel: 01786 468 248 Fax: 01786 464 611 | Terms & Conditions | Contact Us |
|
11/02/2009
|
Home | FAQ | Forum | Glossary | Vacancies | Site Map | Links | Contact Us
|
 |
 |
 |
|
Latest News: Go Greener And Save Over £400 By Reducing Food Waste
|
|