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Draft PPS18: Renewable Energy
Annex 1: Energy from Waste (Thermal Processes)

D1. There are various technological configurations adopted to extract energy from waste. These can be broadly subdivided into thermal and biological processes. This section relates to the thermal processes, which use a high temperature process to release the chemical energy in the fuel.
D2. This section offers guidance on types of thermal plant used to extract energy from the biodegradable fraction of waste. It discusses their main characteristics, the basic technology and their environmental implications. The Government Renewables Obligation Order definition is adopted here as the definition of what constitutes renewable energy in relation to energy from waste, and this is defined below.

Municipal Solid Waste

D3. Municipal solid waste (MSW) is the term used to describe those wastes gathered from domestic and commercial premises by the local waste collection authority. The quantity of MSW available is broadly proportional to the population of an area, but its composition will be affected by local factors such as the method of waste collection and the extent of waste recycling.

Business Waste

D4. Non-hazardous industrial and commercial waste arisings in the UK have been estimated to be around 25 million tonnes per year, consisting mostly of paper, cardboard, wood and plastics. The disposal route for the bulk of this waste is landfill, although a small amount is incinerated along with MSW. In general, non-hazardous business waste can be preprocessed in similar ways to MSW to enable combustion using a range of technologies.

Other Relevant Wastes

D5. The main types of other wastes suitable for energy from waste schemes are as follows:
Sewage sludge: in 1999 (latest available figures) the UK produced 1.13million tonnes of sludge (dry solids). This corresponds to an average of about 20kg generated by each person and may be considered for combustion or other thermal processes for the disposal of this material.
Wood processing waste: small quantities of processed wood waste are produced by the furniture industries and can be classed as renewable, in their uncontaminated form.

Waste Arisings & Collection

D6. The source and collection method of the waste material affects the scope for using it in energy generation. MSW arisings are spread through an area, and are collected by local authorities or their contractors and taken to disposal sites. Other wastes arise at specific locations and lend themselves to small-scale energy schemes. There are economies of scale with larger more centralised plants.
D7. The Renewables Obligation Order (Northern Ireland) 2006 Opens link in a new browser window states that only electricity derived from ‘biomass’ will be eligible for Renewable Obligation Certificates (ROCs). ‘Biomass’ is defined here as a fuel of which at least 98% of the energy content is derived from plant or animal matter or substances derived directly or indirectly there from (whether or not such matter or substances are waste) and includes agricultural, forestry or wood wastes or residues, sewage and energy crops.
D8. A generating station which is fired wholly or partly from waste is excluded from receiving ROCs unless:
  • the only fuel is biomass in accordance with the above definition; or
  • advanced conversion technologies (e.g. pyrolysis and gasification) are used to produce a fuel gas, in which case ROCs can be claimed for the biomass fraction of the fuel. This is an incentive for the development of new technology which is inherently cleaner and can be deployed on a smaller scale.
D9. In accordance with this definition, conventional waste incinerators firing MSW will not be able to claim ROCs for the electricity they generate. Only those installations eligible for ROCs are counted as renewable energy generation in the context of this document. Any firing of non-biomass waste will result in the plant being subjected to far more stringent controls, which needs to be borne in mind when considering MSW as a fuel.
This section contains the following sub-categories:
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