MBT backed by new study to aid UK reach targets

Waste pre-treatment will play a crucial part in the implementation of waste disposal as the implications of the Landfill Directive and IPPC regimes take effect. The Government, and its agencies are playing active roles in advising industry and local authorities on how new technologies can be applied to handling the UK's waste. LAWE reviews recent developments and a major new study of MBT, which has been undertaken recently

The Government, through DEFRA's waste policy unit, has given broad indications of what options are likely to be available to local authorities for the pre-treatment of municipal solid waste.

These are:

  • 1 Source Separation of Recyclates a) Household Waste Recycling Act 2003 requires collection of at least two recyclates separate from the rest of the waste. i) This separation is a pre-treatment and is conducted by either (1) Householders separating recyclates of the LA's choosing and storing them in receptacles provided by the LA. (2) Kerbside separation of recyclates by collection crews (usually where the LA provides one container for a range of recyclates). b) Civic Amenity sites where the recyclates are placed into containers dedicated to specific materials. c) Recycling centres that receive waste directly from the public, similar to CA sites except some of the recycling activities (such as compaction and bailing) take place on site.
  • 2 Composting & Anaerobic Digestion d) The EU Landfill Directive requires the reduction in the amount of biodegradable municipal waste sent to landfill. Organic material can be stabilised, so that it will not degrade further and release greenhouse gasses into the environment when it is landfilled: i) Composting can be a pre-treatment where the purpose is to stabilise the organic fraction prior to landfill. ii) Anaerobic digestion recovers energy from waste with subsequent composting of the digestate as a stabilisation prior to landfill. Recovery of recyclates can take place either side of the anaerobic stage.
  • 3 Mechanical Biological Treatment (MBT) e) MBT is an umbrella term for a range of different processes that involve both mechanical and biological pre-treatment of waste. The order in which these processes take place can also vary. However, all MBT involves pre-treatment of waste, comprising material recovery, composting, production of Refuse Derived Fuel (RDF), etc. f) Autoclaving (pressure cooking) can be incorporated into an MBT process, as well as used in isolation to pre-treat residual waste prior to composting or material recovery (recycling). g) The biomass residue from MBT processes can be used on land, subject to its quality, or as a low carbon fuel in a range of energy recovery processes.
  • MBT study

    According to a recent study MBT of waste could offer a solution to meet stringent targets.

    The findings of the major year-long study were reported at a seminar at Imperial College. The study, carried out by Juniper, has been funded by SITA Environmental Trust through the Landfill Tax Credit Scheme, with additional support from ASSURRE. The purpose of the international study was to find out whether MBT is a viable form of waste management. One key question is "Can it enable local authorities to meet stringent targets for diverting waste from landfill?".

    The results of the study could have a significant influence on the waste management strategies of local authorities in the UK.

    Key findings include:
  • Juniper's one-year independent appraisal of MBT systems from throughout the world has concluded that MBT is likely to be an attractive option for many UK local authorities, despite a number of issues (which are detailed in the report).
  • This study has also identified reasons why MBT will be of interest in many other countries, including the new EU Member States, Mediterranean countries, Canada, Australia and Ireland. But, because of the way UK landfill diversion and recycling targets are structured, it is uniquely attractive for the UK.
  • Dealing with the outputs

    The main challenge associated with MBT is finding viable uses for the solid outputs from the process and securing long-term off-take arrangements for those materials. Juniper's study assessed 24 possible end-uses against five key parameters. These parameters were:

  • Usability and functionality
  • The balance of supply and demand
  • Economics
  • Regulatory and policy acceptability
  • Market appetite (the attitude of potential users).
  • This extensive analysis also included a review of the situation at key reference plants across Europe.

    Previous work had identified issues associated with the two main markets: production of an agricultural compost and production of a substitute for fossil fuels in power stations.

    Juniper's study concluded that the challenges associated with these applications are even greater than previously thought and that, unless government policy changes, take-up for such applications will be very limited.

    However, the study did identify a number of end-uses which are viable and which, together, could absorb all of the outputs from facilities, even if MBT is very widely adopted. These end-uses include certain specific and-remediation, soil improvement and civil engineering applications, as well as new ways of displacing fossil fuel through coupling the MBT plant to gasifiers or dedicated combustion units.

    Impact on UK targets

    Juniper has conducted an assessment of the role that MBT can play in meeting UK Landfill Diversion Targets. This evaluation has produced some surprising results, which could have far-reaching consequences.

    Juniper has shown that some processes have the potential to achieve diversion rates of up to 95%. But the precise level of diversion is very uncertain at the current time because the Environment Agency is in the middle of a consultation process on how this diversion rate will be measured and calculated.

    Juniper has modelled the effect of different methods of calculation - and the impact that this has on the headline performance against targets. Depending upon the type of system used, the reported rate could be as low as 14%, but in some cases could be more than 80% (expressed as the percentage diversion of the input to the MBT plant), even if the bio-treated output is sent to landfill.

    From the many discussions that Juniper has had in connection with this study, it is clear that the most important driver for considering MBT is a political desire by LA councillors to avoid the use of incineration. Until now it has been thought that it would not be possible to meet statutory targets (particularly the 2020 Landfill Diversion targets) without using thermal waste processing methods to some degree. Juniper's study indicates that this is not necessarily the case for every local authority.

    *Juniper's Report is entitled 'Mechanical-Biological-Treatment - A Guide for Decision Makers: Processes, Policies and Markets'. The report is available as a downloadable pdf from the websites of Juniper (www.juniper.co.uk), SITA Environmental Trust (www.sitaenvtrust.org.uk) and ASSURRE (www.assurre.org). ASSURRE was founded in 2000 and is a Brussels based, multi-sectoral Partnership for Action, which aims to be the leading European Association promoting Sustainable Resource Management.

    Purac targets waste sector

    Indicative of the interest the development in the UK waste industry is generating is the increased focus that Purac, a leading process technology contractor in the water and environmental sector, is bringing to bear on the market.

    Having a record of 40 years in the process plant business and with a turnover of around £50 million, employing around 300 people at its head office in Kidderminster, and on sites around the country, the company looks well placed to make an impact. Purac provides treatment technologies for a range of materials, and has delivered turnkey treatment plants up to £30 million in value.

    The company is now bringing these process engineering and contract delivery skills to the waste sector in the UK. Purac has acquired exclusive UK licences for the BTA Process for anaerobic digestion of wastes, one of the world's leading anaerobic digestion systems for solid waste with 24 references worldwide on a whole range of different applications. The company has also licensed the Rotoclave rotary autoclave from Tempico of New Orleans, USA, which, it says, shows great promise for efficient separation of BMW and recyclates from residual waste. Added to this Purac has a series of project partners for waste separation, composting systems and MBT systems.


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