EfW DEVELOPMENT GUIDANCE - Wrap

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WRAP – EfW DEVELOPMENT GUIDANCE – September 2012 1.0 Introduction This guidance examines the variables and properties of waste derived fuel materials, how they can influence the type of processing technology chosen and the different outputs. The characteristics of the waste feedstock and its variability are key parameters when determining which technology will be the most suitable for the EfW proposal. Understanding the composition and variation in the potential feedstocks/fuels will help operators select the right EfW technology, plant design and determine the overall energy efficiency that is achievable. A consideration of the potential waste feedstocks which will be available and suitable for the proposed energy from waste (EfW) facility is a key aspect of the development of the business case for a proposal 1 . A process designed to utilise waste biogenic content or a processed Refuse Derived Fuel (RDF) would suffer operational problems if suddenly faced with unsorted Commercial and Industrial (C&I) wastes or material heavily contaminated with food rich material. The overriding objective of the waste hierarchy is to drive material up the hierarchy as far as is possible, when it is possible, so as to maximise the potential to divert waste from landfill. The remaining waste, following recycling, re-use and composting, should then be managed in recovery facilities such as an EfW. These facilities have a key role to play within the hierarchy to divert residual waste from landfill. 2.0 Feedstock types The characteristics of the waste feedstock and its variability are key parameters to examine when determining which technology would be the most suitable for the proposed facility. The feasibility assessment will need to include a detailed analysis of the physical and chemical characteristics of the feedstock. Understanding the composition and variation in the feedstock will help select the right EfW technology at the plant design stage. This will need to be reviewed over the life of the contract as feedstock composition may change. The larger mass burn technologies are less sensitive to variations in feedstock, but the smaller-scale, more efficient processes such as gasification and pyrolysis, are much more sensitive to fuel change, generally requiring pre-treatment of feedstock. The physical and chemical properties of the waste can have an impact on the energy efficiency, operation and emissions of an EfW facility, as can factors such as moisture content, ash content and bulk density. Variety in these factors will define that fuel and its end usage, and lead to its determination as one of a number of pre-defined Waste Derived Fuels. Generally, they would be classed under one of the following headings, due to the factors listed beside them. Generic fuel type ‘RDF’ – Refuse Derived Fuel Biogenic content ‘SRF’ – Solid Recovered Fuel Typical calorific value 10-12 Mj/Kg 15-18 Mj/Kg 18-22 Mj/Kg Defining factor Residual material left over following the separation of recyclable materials in a MRF, Mechanical Biological Treatments (MBT) or transfer station General woody waste material, including forestry thinnings, joinery waste and clean or treated wood products A processed material specifically targeted for the higher CV fraction of the waste. Commonly used in cement kiln operations 10 See WRAP guidance on Feasibility and Good Practice Feedstock Home Funding Feasibility and Good Practice Planning Environmental permitting regulations Outputs Financial Incentives Waste Incineration Directive Glossary Guide page 42
WRAP – EfW DEVELOPMENT GUIDANCE – September 2012 3.0 Fuel preparation The feedstock may require further processing before it can be thermally treated in some of the technologies. For instance, some machinery which pyrolyses wood chip requires the chip to be of a certain and consistent size. The type of fuel preparation techniques used would depend on the input fuel and the EfW technology being used, but some commonly used fuel preparation techniques include: • Sorting. Either manual sorting or mechanical sorting in order to identify and remove any metals, rigid plastics, other recyclable materials or unusable contaminated materials which aren’t wanted within the fuel. Mechanical sorting techniques can include over-band magnets, density separators, infra-red optical scanners or wind blowing sifters. • Crushing or shredding. This reduces the material to a standard, general, or given size or can be used to homogenise the physical characteristics. • Screening. Screens (rotating drum screens, oscillating screens, star screens, etc.) can help remove aggregates or soil products from the feedstock, leaving a more usable, higher CV material to make up the fuel. • Washing. Removes contaminants stuck to the material. • Drying. Reduces moisture content. • Homogenisation. Generally the final stage in fuel preparation, these are processes designed to bulk the material, assist in its transport and storage or to present the fuel in a certain manner e.g. mixing, blending, compacting, pelletising or baling. 4.0 Feedstock security The whole process in setting up an EfW facility from concept, feasibility, design, commissioning to operation represents a significant capital investment over a long period of time. A cost benefit analysis needs to demonstrate to funders that sufficient suitable waste feedstock is available over that period to ensure the facility can run at or near capacity and generate the revenues or savings expected. Developers will therefore need to demonstrate feedstock security and consider any changes to their business that might impact on the quantity or composition of the waste feedstock they use. In some circumstances, it may be found that numerous EfW facilities in a small, concentrated area would lead to those facilities competing for waste feedstocks. This could lead to higher values for the fuels as the plants are prepared to pay more for the material (or reduce their gate fees) in order to continue operation. The signing of long term contracts or other business relationships such as partnerships, joint ventures, vertical integration, etc., can go a long way to guaranteeing fuel security and feedstock availability. Feedstock Home Funding Feasibility and Good Practice Planning Environmental permitting regulations Outputs Financial Incentives Waste Incineration Directive Glossary Guide page 43
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EfW DEVELOPMENT GUIDANCE - Wrap

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