Policy objective 6: To ensure that residual waste treatment complements activities higher up the waste hierarchy and maximises the value recovered from waste in terms of resources and energy.
Sufficient residual waste treatment capacity will be procured to ensure that the following objectives are achieved after taking into account the targeted levels of recycling and composting:
- Diversion of biodegradable waste from landfill to meet and exceed Dorset’s obligations under LATS in accordance with policy objective 5.
- Recovery of value from at least 75 per cent of municipal waste by 2020 in accordance with the strategic target in the National Waste Strategy.
The form of residual waste treatment will be evaluated on the basis of the environmental, social, economic and deliverability criteria set out in the section below.
A provisional assessment using environmental, social and economic criteria to ensure sustainability is fully addressed, indicates that the following forms of treatment perform reasonably well against the agreed criteria;
- Direct Energy From Waste (EfW)
- Autoclave (or Mechanical Heat Treatment (MHT)) followed by Advanced Thermal Treatment (Gasification or Pyrolysis) of the residue
- Mechanical separation followed by Advanced Thermal Treatment (Gasification or Pyrolysis)
- Mechanical Biological Treatment (MBT) with Anaerobic Digestion (AD) to produce biogas and production of a Refuse Derived Fuel (RDF) for combustion
However, a more rigorous evaluation will be undertaken as part of any future procurement process, taking into account the more detailed information that would then be available.
It is recognised that economies of scale are particularly relevant to the treatment of residual waste and opportunities for both collaboration with other authorities and co-treatment of a proportion of business waste will be explored where they can provide better value for money.
This would also assist with more sustainable management of business waste.
Policy links
This objective is linked to policy objective 3, 4 and 5. It also has significant cost implications and therefore an important link to policy objective 7.
Residual waste is that waste which is not recycled or composted and in Dorset it is currently disposed of to landfill. Recent progress with recycling and composting and the new target to achieve 60% by 2015/16 will help to significantly reduce the quantity of residual waste arising from the municipal waste stream.
However, there will always be a proportion of residual waste that needs to be dealt with. The current projected tonnages of residual waste arising from the municipal waste stream are detailed below
Projected tonnages of residual waste
Based on 1 per cent annual growth in total waste arisings and 60 per cent recycling achieved by 2015/16:
- 2007 to 2008 - 120000
- 2009 to 2010 - 112000
- 2012 to 2013 - 101000
- 2019 to 2020 - 98000
The cost of disposal to landfill is rising significantly as a consequence of the escalation of landfill tax in particular that for non-hazardous waste, which is currently £32/tonne and set to increase to £48/tonne in 2010/11.
The Government have clearly stated that it will increase further thereafter.
In order to meet the county’s LATS targets for the diversion of BMW from landfill it will be necessary to treat at least a proportion of the residual waste, as identified in policy objective 5.
It is currently predicted that it will be necessary to divert a minimum of approximately 40,000 tonnes of residual waste from landfill by 2020 in order to meet the WDAs’ LATS obligations.
Diverting this minimum quantity of waste from landfill would still mean landfilling approximately 58,000 tonnes of municipal waste with consequent emissions of methane and no recovery of value from the waste.
In addition, there are economies of scale involved in developing waste treatment facilities and it may not be cost-effective for Dorset to procure a facility of this marginal size.
When considering the procurement of infrastructure it is necessary to plan for the longer term needs of the next 25 -30 years both in terms of potential continued growth in waste and the availability of landfill.
It is recognised that increasing restrictions, reduced physical availability and rising costs are likely to prohibit the use of landfill for the disposal of municipal waste in the long run.
The possibility of a future ban on all biodegradable waste from landfill (biodegradable hazardous waste has already been banned) is discussed in the national Waste Strategy 2007 (WS2007).
Collaboration between authorities is encouraged by DEFRA in relation to the treatment of residual waste in recognition of the potential to deliver better value for money.
The Dorset councils work in partnership with both the Borough of Poole and Bournemouth Borough Council, in particular, and are seeking opportunities for joint working where this is beneficial.
A more holistic approach embracing both municipal and business waste is also now encouraged and it is estimated that approximately 400,000 tonnes of commercial waste is generated in Dorset (including the Bournemouth and Poole area) each year.
A more integrated approach provides a real opportunity to deliver more cost effective and environmentally sound options for Dorset as a whole, including both the public sector and SMEs in particular.
Therefore, in line with our philosophy and high-level principles to minimise waste to landfill, meet and eventually exceed landfill targets, work in collaboration with others and provide good value for money, any treatment facility for residual waste should be of a scale to:
- minimise waste to landfill
- provide some spare capacity for
- higher levels of waste growth
- locally produced business waste
- other local authorities waste where there are appropriate synergies
- provide a cost-effective solution for Dorset
On the basis of this information it is currently considered prudent to plan for a residual treatment capacity of approximately 150,000 tonnes per year. This capacity is made up of the following:
- kerbside residual waste. Landfill minimised - variation due to recycling performance and waste growth. 80,000 - 110,000 tonnes
- HRC residual waste - following pre-treatment - 10,000 tonnes
- capacity for business waste or other authorities waste 50,000 tonnes
- plant capacity 140,000 - 170,000 tonnes
This capacity has been assumed in the provisional evaluation of residual treatment options which has been undertaken in relation to this strategy.
This is not, however, fixed and will be kept under review. In particular, a more rigorous evaluation will be undertaken before finalising any procurement and this will take into account a full risk assessment, the circumstances at the time and the most optimum solution then available.
In the short term to meet the landfill diversion targets prior to a waste treatment facility being operational, an interim contract has been agreed with New Earth Solutions near Poole to assist with Dorset’s requirements for diversion from landfill up to 2012.
This involves quite small tonnages and a permanent solution is required to meet the longer term needs.
Other interim contracts may also be required depending on waste growth, recycling behaviour and procurement.
The previous strategy (2003) identified a process of Mechanical Biological Treatment (MBT) leading to the production of a Refuse Derived Fuel (RDF) as the preferred form for treatment of residual waste.
However, there have been significant developments in available technologies over the last five years and it has also become clear that allowing greater flexibility for industry to respond innovatively to our needs is likely to deliver more cost effective solutions.
A full re-evaluation of the potential solutions was undertaken as part of the review of the strategy.
The assessment process, involving a Sustainability Appraisal (SA) and Strategic Environmental Assessment (SEA), is fully described in the Sustainability Appraisal Report.
The approach is based on evaluation of potential options against an agreed list of sustainability criteria and weightings.
The criteria have been developed with reference to European and national laws, the South West Regional Sustainable Development Framework and Dorset’s own sustainable development aspirations.
Natural England, English Heritage and the Environment Agency were consulted about the criteria during the Scoping Stage of the Sustainability Appraisal.
The list of criteria set out in the information below has been adopted following consultation during the Scoping Stage.
Evaluation criteria
Assessment criteria
Basis of measurement
Table - Environmental criteria
Environmental criteria |
Basis of measurement |
Air quality |
Emission of potentially acidifying gases to the atmosphere |
Water quality |
Emissions of potentially eutrophic and ecotoxic compounds into freshwater aquatic systems |
Land take |
Estimated land take for waste treatment facilities, measured in hectares |
Impact on human health |
Toxicity levels generated by the waste treatment facility. |
Nuisance |
Levels of noise, odour and litter nuisances caused by waste activities |
Traffic & transport |
Traffic impacts associated with transporting waste and the outputs generated from the facility to their final destination, calculated as tonne miles |
Climate change impacts |
Emission levels of potentially global warming gases to the atmosphere through the operation of the facility |
Energy recovered/saved |
Maximising the total energy recovered and/or saved by processing the waste stream with added value attributed to that amount deemed "renewable". |
Contribution to recycling and recovery targets |
Tonnage of waste recycled and recovered |
Minimise biodegradable waste sent to landfill |
Amount of Biodegradable Municipal Waste (BMW) diverted from landfill by recycling, composting and treatment. |
Minimise residue to landfill |
Tonnage of material waste sent to landfill following recycling/ treatment. Tonnage of hazardous waste tonnes requiring treatment/disposal |
Dealing with outputs locally |
Relative proportions of outputs from treatment of waste that are used/disposed of within the county (excluding that exported from the county for recycling). |
Built & historic environment |
Potential impacts on the physical environment in terms of visual impact |
Table - Social criteria
Social criteria |
Basis of measurement |
Employment |
How many jobs will the facility or new collection systems generate? Will they provide stable, long-term employment? |
Participation levels |
Ease of participation and the variation of the service across Dorset. Risk of fly tipping. |
Table - Economic criteria
Economic criteria |
Basis of measurement |
Strive to have best value waste management service |
Cost of delivering the service based on capital, operational and collection costs across the county |
Reducing risk and commercial & financial robustness |
- how confident can we be that the technologies will work reliably for the long term?
- are there other similar plants operating at a commercial scale?
- will the private sector and banks support the project?
- will significant risk still reside with councils?
- will there be long term markets for the outputs?
- what is the public perception of the type of technology and how will this affect planning?
- how certain can we be about costs?
- what is the risk of delay and how much might this cost?
|
These criteria were initially weighted on the basis of the professional judgement of officers and advisors and subsequently modified following feedback from the consultation.
The criteria are grouped under the three principle sustainability considerations, namely:
- environmental
- social
- economic
These three high level categories have first been weighted by allocating marks out of ten in each case.
These high-level scores have then been allocated across the detailed criteria within a particular category by awarding each criterion a mark out of ten in the same way. The weightings derived from the process are then expressed as a percentage for ease of overall comparison.
These weightings, determined on the above basis, have been used to complete a provisional assessment of the options.
It is proposed that the criteria and weightings used to let the contract for the final choice of residual waste treatment in the future should be based on those contained in this strategy.
However, it is recognised that some amendment may be necessary to select any additional considerations relevant at the time the WDA procures a contract, including for example deliverability, available technologies and funding.
A provisional assessment of currently available technologies has been undertaken as part of the review of the strategy to identify those that perform well against the selected sustainability criteria.
A more rigorous evaluation will be undertaken as part of any procurement process, taking into account the more detailed information that would be available and any additional considerations that are relevant.
There are currently a wide range of technologies and permutations of options becoming available for the treatment of residual waste. Nine generic options have been identified for evaluation as listed below.
These generic options have been drawn up with the intent of embracing all the potentially feasible forms of solutions available.
Key to abbreviations used:
- ATT Advanced Thermal Treatment
- MBT Mechanical Biological Treatment
- MHT Mechanical Heat Treatment
- RDF Refuse Derived Fuel
- SRF Solid Recovered Fuels
Summary of residual treatment options considered
Scenarios
Scenario 1 - Mechanical separation with Advanced Thermal Treatment
Process description/sub-options
Following mechanical separation to recover further recyclable material the remaining waste is placed in gasification or pyrolysis chambers and heated to high-temperatures in low or zero levels of oxygen.
The process, which is similar to the production of coal gas in the past, generates gases which are collected and combusted to produce heat.
Scenarios
Scenario 2 - Direct EfW
Process description/sub-options
An Energy from Waste (EfW) plant is essentially a furnace that burns waste at a high temperature.
Heat from the combustion process is usually used to generate electricity, and may also be used to supply heat to external users (termed combined heat & power or CHP). The resulting flue gases are subject to rigorous cleaning processes in accordance with the EU Waste Incineration Directive (2000) before emission to the atmosphere.
Direct EfW is therefore very different from the old generation of mass burn incinerators that were mainly used to reduce the volume of waste with no recovery of energy and only minimal environmental control measures.
Scenarios
Scenario 3 - Autoclave (or MHT) with Advanced Thermal Treatment
Process description/sub-options
Autoclave or Mechanical Heat treatment (MHT) is a form of waste treatment that utilises heat, steam and pressure to treat the waste. Following the process high quality and clean plastic, ferrous and non-ferrous metals are then separated out. The remaining cellulose material, or biomass, can be used as feed stock for the gasification/ pyrolysis techniques described above.
Scenarios
Scenario 4 - MBT/MHT with RDF output
Process description/sub-options
Mechanical Biological Treatment (MBT) involves the mechanical separation of waste into those materials that can be recycled, a fraction comprising paper and plastic fragments which has a high calorific value and can be used as a fuel (Refuse Derived Fuel - RDF) and a fibre fraction.
The RDF material can be used on or off-site for use as a co-generation fuel. A variant on this option is the use of MHT or autoclaving to assist in the initial separation of the waste. In this scenario the resulting fibre fraction from either process is then composted aerobically with the stabilite material being sent to landfill.
This is similar to the preferred option identified in the previous waste strategy, published in 2003.
Scenarios
Scenario 5 - MBT with aerobic composting
Process description/sub-options
Mechanical Biological Treatment (MBT), as described above, but without the separation of an RDF and with all the remaining material being composted aerobically and the stabilised material being sent to landfill or, potentially where it is of better quality, being used as a soil improver (in non-food applications).
Scenarios
Scenario 6 - MBT/MHT with AD
Process description/sub-options
Mechanical Biological Treatment (MBT) or Mechanical Heat treatment (MHT) as described above, followed by anaerobic digestion (AD) of the resulting fibre fraction to generate a biogas for energy production.
The stabilised output is sent to landfill.
Scenario 7 - MBT with AD and RDF output
Process description/sub-options
Mechanical Biological Treatment (MBT) as described above including the production of RDF followed by anaerobic digestion (AD) of the resulting fibre fraction to generate a biogas for energy production. The stabilised output is sent to landfill.
Scenario 8 - Landfill
Process description/sub-options
All waste is sent un-sorted to a EU specification landfill with energy recovery from landfill gas.
As noted above, various forms of residual waste treatment have the potential to generate energy through some form of combustion.
Energy can therefore be recovered from the waste, and this can make a valuable contribution to mitigate against climate change by displacing the need for other forms of energy generation using fossil fuels.
Depending on the particular choice of residual treatment, if energy is produced, a proportion of this maybe classified as renewable. The Bournemouth, Dorset and Poole Renewable Energy Strategy has identified recovery of renewable energy from waste as a priority area.
DEFRA have recently put an emphasis on authorities utilising Combine Heat and Power (CHP) technologies.
When energy is being generated the most efficient solution is combined heat and power, where the heat is utilised as well as producing electricity.
For each of the scenarios which include combustion to produce electricity the option to also utilise the heat in a combined heat and power (CHP) scheme has also been considered.
In addition to the scenarios identified above, plasma arc gasification is a new method of treatment that combines a first stage gasification, with a second stage high electrical energy/high temperature stage (created by an electrical arc) to treat the waste.
The solid residues are vitrified at the high temperature. It is not yet available on a commercial scale for treatment of residual waste in the UK and there is insufficient data available for it to be have been included in our provisional assessment.
It is not currently considered a viable option but it could be included in future evaluations if it becomes a sufficiently proven option by then.
The evaluation process is described in detail in the Sustainability Appraisal report and the conclusions are summarised as follows.
The provisional evaluation, based on the sustainability criteria and weightings as agreed by officers and modified in light of the outcomes of the public consultation process ranks the options in the following order:
- 1st - Direct EfW
- 2nd - Autoclave (or MHT) with Advance Thermal Treatment (ATT)
- 3rd - MBT with AD and RDF output
- 4th - Mechanical separation with Advanced Thermal Treatment (ATT)
- 5th - MBT/MHT with RDF output
- 6th - MBT/MHT with AD
- 7th - MBT with aerobic composting
- 8th - Landfill
This has been a desktop exercise and ultimately a procurement process would determine the most suitable option.
All the treatment options considered perform significantly better than continuing to landfill
the residual waste.
The options appraisal included a high level comparison of costs. This was based on an estimate of the Net Present Cost (NPC) of each option including the capital cost of building the facility and the cost of operating it over its life (typically 20 – 25 years).
These costs are discounted over time and added together to give a simpler comparison between the options at today's prices.
The results are presented in the table below:
Table - Net Present Cost (NPC) of each option
Ref |
Technology |
NPC (£) Low is best |
Normalised Score (out of 10, high is best) |
1 |
Mechanical Separation with Advanced Thermal Treatment |
110,000,000 |
10 |
2 |
Direct EfW |
115,000,000 |
9.6 |
3 |
Autoclave (or MHT) with Advanced Thermal Treatment |
112,000,000 |
9.9 |
4 |
MBT/MHT with RDF Output |
147,000,000 |
7.5 |
5 |
MBT with Aerobic Composting |
176,000,000 |
6.2 |
6 |
MBT/MHT with AD |
186,000,000 |
5.9 |
7 |
MBT with AD and RDF Output |
155,000,000 |
7.1 |
8 |
Landfill |
223,000,000 |
4.9 |
It should be noted that determination of detailed cost estimates is beyond the scope of a strategy and these figures are therefore only indicatory.
Much more detailed cost estimates will be determined as part of the business case for delivering the residual waste treatment solution in due course.
Economies of scale are particularly relevant to the treatment of residual waste. A single plant is thus likely to be the most economic and the options evaluation, based on the full list of criteria, indicates that a single plant serving the whole county generally performs best.
Opportunities for both collaboration with other authorities and co-treatment of a proportion of commercial waste will be explored and, where viable, will be adopted if they can provide better value for money.