MBT or Not To Be?
Adam Baddeley of Juniper Consultancy Services weighs up the merits of Mechanical Biological TreatmentThe EU Landfill Directive has resulted in the need for Local Authorities to invest in new treatment infrastructure to divert biodegradable municipal waste (BMW) from landfill.
On face value, energy-from-waste (EfW) facilities appear to be the simplest and most proven means of achieving this goal, but to determine which approach is likely to be the most widely adopted in the UK, EfW must be considered alongside newly marketed technologies, such as Mechanical Biological Treatment (MBT).
Potential approaches to BMW diversion must demonstrate that they are bankable in a Private Finance Initiative (PFI) context, and so must be assessed against a defined set of key risk factors, including:
If a particular waste management solution is to be successful, it will need to demonstrate high performance against each of these criteria for the full period of the contract - which may be up to 25 years in length.
Whilst incineration is considered to be a "final disposal" option, i.e. ash is sent to landfill, unless MBT is coupled with a dedicated thermal treatment facility, the technology is usually perceived as only a "pre-treatment" solution.
Concern about the marketability of the outputs from MBT processes is perhaps the single most significant factor constraining the technology at present.
Most MBT processes currently being included as part of PFI tenders are configured to produce either a solid recovered fuel (SRF) or a compost-like output (CLO).
A year-long study recently published by Juniper examines various potential applications for these outputs from a market, regulatory, technical, environmental, and supply/demand perspective.
Unless an existing, operational incinerator has spare capacity, SRF relies upon an appropriate facility for co-firing. Proponents of this type of MBT system often cite coal-fired power plants, cement kilns and industrial boilers as potential co-firing options, but Juniper's analysis indicates that as a result of various technical, regulatory and commercial constraints, these routes do not currently represent viable large-scale outlets for SRF in the UK.
The DTI is currently consulting, however, on whether to extend eligibility for Renewable Obligation Certificates (ROCs) to some mixed waste applications, and this may have a positive influence on the viability of some options.
The Juniper report also concludes that, as a result of competition from other better quality materials, such as large tonnages of source-separated green waste compost which meet the voluntary BSI PAS 100 standard , there will be only very limited outlets for CLO - for example, in land remediation projects or on energy crops - that would not require a potentially prohibitive gate fee.
An alternative approach, and one used in other Member States, is to configure MBT processes to produce a bio-stabilised residue that is sent directly to landfill.
This approach can alleviate some of the market risk associated with MBT, and because the BMW content of the residual waste is significantly reduced, it will have less impact on LATS performance.
Ever-increasing landfill taxes and limited landfill void space in many regions, however, mean that it may not be the lowest cost option over the long-term.
The way in which the biodegradable content of municipal solid waste (MSW) is measured in the UK will also influence the viability of this type of MBT.
Currently, how the BMW content of bio-treated residual waste is measured is the subject of an ongoing Environment Agency (EA) consultation process (on behalf of DEFRA), for which guidance is expected to be published this summer.
Plans for an EU Biowaste Directive have been unofficially abandoned, and although it is possible that an overarching Soil Strategy later this year could be used to create a harmonised BMW measurement, Brussels is likely to allow some flexibility for Member States over their choice of methodology, and thus it would be unlikely to affect the approach adopted in the UK.
To be considered bankable, treatment options should ideally have commercial reference sites that have been operating for a minimum of two years, although in some specific instances, the successful operation of demonstration facilities may be sufficient to gain investor confidence.
In the UK, all MBT configurations are viewed as less technically proven than mass-burn incineration, but due to the number of MBT reference plants operating in Europe, many such processes will nevertheless be considered bankable by the financial community.
This situation contrasts with many advanced thermal treatment technologies, such as pyrolysis and gasification, which have been successfully operated in Japan, but have not yet delivered enough hours of operation in Europe to be considered for most PFI projects.
Planning & Political Constraints
The operation of commercial reference facilities can also aid the passage of technologies through the UK Planning process, as site visits can be used to allay the concerns of Local Authority Planning Officers with regard to such potential issues as visual impact or odour.
Political resistance to incineration, as a result of the perceived health effects, has resulted in a groundswell of political enthusiasm for MBT as a way of meeting LATS targets without the need for controversial thermal treatment. But, even if an MBT solution is configured to produce a CLO, there remain health concerns, which DEFRA admits have not as yet been given full attention in any published research .
In attempts to increase the amount of permitted waste treatment capacity, ODPM is currently consulting on a new Planning Policy Statement (PPS) 10, but unless the government also implements a proposed "apportionment" strategy - whereby regional planning bodies would be required to allocate tonnages of waste requiring management to planning authorities - the wider industry remains sceptical of its prospects for success.
Local Authorities applying for PFI credits are advised by ODPM to draw up "output specification" contracts, in which successful bidders are likely to be bound to meeting specific LATS and BVPI recycling targets.
Prescriptive conditions regarding technology choice may be listed in the tender document, but ODPM recommends that "no unnecessary constraints" are placed upon the private sector and how services are delivered. As a result, waste management contractors are currently responding with a range of waste treatment solutions to meet these "output specifications".
Juniper's in-house forecasting model - based upon a multitude of variables including technical, planning and economic factors - indicates that the most likely scenario will result in a mix of technical solutions, developed according to the needs of each local situation.
The only certainty remains, however, that waste PFI projects which are not based upon a full assessment of each risk factor will be tantamount to commercial suicide.
By Adam Baddeley.
1 DEFRA has stated that WDAs will be fined £150 for every tonne of BMW sent to landfill in excess of their LATS allocation.
2 MBT: A Guide for Decision Makers: Processes, Policies and Markets, Juniper, March 2005.
3 Developed by The Composting Association, this states that to achieve certification, material must have been kept separate from non-biodegradables.
4 Assessing the diversion of biodegradable municipal waste from landfill by mechanical biological treatment and other options, Environment Agency, November 2004.
5 It is important to acknowledge that whatever system is adopted by the EA, the ash from incinerators will not count against BMW allowances.
6 Review of Environmental and Health Effects of Waste Management, Enviros et al on behalf of DEFRA, March 2004.
Juniper Consultancy Services