Western Isles Area Waste Plan

3 Western Isles Best Practicable Environmental Option (BPEO) for Municipal Solid Waste (MSW) – The Strategy For Change

This chapter sets out the BPEO for MSW.

Public Consultation
Two extensive public consultation processes were carried out as part of the Western Isles BPEO decision process. The first sought local views on five strategic options, and the second on the Draft AWP itself. The five options were developed by the WSAG and focused around anaerobic digestion, composting, incineration with energy recovery, waste export, and continued landfill respectively (waste prevention and minimisation was a salient feature of all the options). The overwhelming majority of responses stated a preference for either anaerobic digestion or composting as the mainstay of the AWP, and this concurred with the view of the WSAG. The other key finding, which again concurred with the views of the WSAG, was the need to dramatically improve access to and use of recycling facilities throughout the Isles. These twin components – centralised digestion and composting and increased recycling – are the main elements of the Western Isles BPEO.

Other Key Local Considerations
A major factor influencing the Western Isles BPEO process was the geographical fragmentation and remoteness of the area, and its highly dispersed human populations. These factors make waste management proportionally more expensive than other mainland regions, and this is compounded as more complex segregation and collection systems are put in place. The separate kerbside collection of recyclable wastes is difficult to justify in remote parts of the islands on both economic and environmental grounds. However, in the absence of a mixed waste energy-recovery facility, achieving the Landfill Directive targets for biodegradable municipal waste (BMW) diversion will require separate kerbside collection of these wastes.

The selection of anaerobic digestion (AD) and composting as mainstay of the BPEO was strongly influenced by the potential local utility of the soil-enhancing products associated with these processes – e.g. in restoring coastal ‘machair’ land. The local applicability of waste-derived soil enhancing materials has already been clearly demonstrated by the three existing Scottish Water pilot projects. An integrated ‘dual’ system, employing both anaerobic digestion and composting processes, allows flexibility in inputs (to accommodate seasonal changes in waste composition) and in the end products produced, the latter affording a greater range of applications to be considered.

Another consideration was the perceived need to allow the integration of other, non-MSW streams in future, particularly as regulatory controls on these wastes tighten, and the costs associated with more traditional disposal methods (such as landfill or spreading) increase. Many important local non-MSW are biodegradable, such as fish and agriculture-related wastes. Again, an integrated anaerobic digestion and composting system should allow greater flexibility to accommodate different wastes at different times, particularly as such a system could be modular, and adapted to accommodate other waste streams.

Anaerobic digestion was seen as particularly attractive to the Isles as the energy by-product produced by this process could be utilised to support local industrial processes, making a positive contribution to the local economy.

Full details of the key stages and decision-making criteria applied in determining this BPEO are detailed in the Draft Western Isles Area Waste Plan 2002 (to obtain a copy see Annex 4). A summary of the overall AWP process is given on page 10.