operation and costs of Materials Recovery Facilities ... Understanding all stages from collection through sorting and bu
Local authority recycling
Recovering value from MRFs A review of key studies relating to the specification, operation and costs of Materials Recovery Facilities
Materials recovery facilities (MRFs) are increasingly important in providing quality raw materials to industry.
Contents Foreword 1 Introduction 2 MRF operations Receiving materials 3 Pre-sorting 3 Managing flows 3 Processing recyclables Separating fibre from containers 4 Sorting fibre 4 Sorting glass containers 6 Sorting metal containers 7 Sorting plastic containers 7 Baling and shipping 8 Managing residues 9 Costs MRF Cost Model 10 Cost implications 12 Contractual Arrangements Contractual relationships between MRF operators and local authorities 14 Safeguarding and improving performance 15 Conclusions 17
The UK is changing fundamentally the way it deals with its waste. From very low levels in 2000, recycling of waste has grown strongly and now stands at 27% for household waste in England and perhaps something over 50% for commercial and industrial waste. This change brings significant environmental benefits: in reducing the need to extract raw materials and in reducing climate changing carbon emissions by an estimated 10-15 million tonnes a year; equivalent to taking 3.5 million cars off the road. The change has not been effortless. Local collection systems, sorting and reprocessing capacity as well as the end markets for materials have all had to adjust to these new demands with some parts of the system being more responsive than others. As the Government is reviewing its waste strategy for England and signalling that a further significant expansion in recycling will be needed, WRAP has been reviewing key parts of the recycling system to identify areas that will need further attention to maximizing the benefits from increased recycling levels. Materials recovery facilities (MRFs) are increasingly important in providing quality raw materials to industry. MRF capacity in the UK is growing but it is unevenly distributed and investment in further capacity will be needed as demand grows. In most cases, MRFs are designed to separate co-mingled recyclables1 into their individual material streams and prepare them for sale into the commodity markets. Although few local authorities are likely to operate MRFs themselves, they will be involved in procuring services from private contractors that involve the design, commissioning and operation of MRFs. Understanding all stages from collection through sorting and bulking to the sale of recovered materials will ensure that, prior to embarking on the procurement route and preparing service specifications, local authorities are better informed about the cost implications of alternative options. This summary document draws together the results of recent studies commissioned by WRAP and draws on good practice in MRF design and management from the USA and Europe. It is intended as an introduction for those unfamiliar with the issues surrounding the specification, operation and costs of MRFs.
1. Around one third of English local authorities collect recyclable materials co-mingled but this number is expected to increase as recycling programmes expand. Most of the remaining authorities operate kerbside sort schemes whereby materials are separated at the kerbside into their individual material streams. Collections are made using stillage or multi-compartment vehicles thereby avoiding the need for sorting of materials at MRFs.
This summary document draws together the results of three separate studies commissioned by WRAP: MRF Case Study Review (contractor: The Dougherty Group LLC), which looked at material sorting practices and technologies employed at a cross-section of MRFs in England, the USA and Europe; MRF Cost Model and User Guide (contractor: Entec Consulting Ltd), which developed a costing tool for different materials sorting options; and Contractual Arrangements between Local Authorities and MRF Operators (contractor: AEA Technology plc), which reviewed and assessed existing contractual relationships between MRF operators and local authorities across the UK. It presents an overview of key aspects in the specification, operation and costs of MRFs with specific reference to: principles of MRF operations; the main steps involved in processing recyclables; costs and economy of scale benefits; and contractual arrangements to support investment and promote high standards of operation. It is intended as an introduction for those unfamiliar with the issues surrounding the specification, operation and costs of MRFs. The full reports are available on WRAP’s website – www.wrap.org.uk. The Cost Model is available on request.
MRF operations There should be sufficient capacity to store at least two days’ worth of incoming materials. Receiving materials It should be standard practice at a MRF for incoming recyclables to be received and stored, prior to processing, on a tipping floor which is protected from the weather. Water can significantly reduce the value of some recyclables especially paper and card. There should be sufficient capacity to store at least two days’ worth of incoming materials. This will enable collection rounds to continue even during unscheduled equipment downtime and at times of high demand such as the postChristmas period. It also gives the MRF a buffer so that it does not have to force material through the MRF faster than its design allows for, which can have adverse consequences for quality.
Pre-sorting Inclusion of an adequate pre-sort station in a MRF can deliver quality control and efficiency benefits. Pre-sorting not only allows removal of contaminants early in the sorting process, but also permits removal of specific recyclables that might otherwise hinder sorting activities downstream. Materials such as film plastic, oversized cardboard as well as non-recyclables (organics, wire, wood etc) can cause problems for some of the automated processing equipment, and can be removed at the pre-sort stage. This enables the processing equipment to operate as designed and makes manual sorting more efficient. Although pre-sort stations are common in North American and European MRFs, they are not incorporated in all MRFs in the UK.
Managing flows Efficient sorting critically depends on a continuous and even flow of material being maintained through the MRF. Levelling out the flow of material occurs as the materials enter the sorting process. This can be achieved by using a series of conveyors operating at variable speeds, stationary gates or metering drums.
The tipping floor at a MRF. Incoming materials are received and stored here prior to processing.
Separating fibre from containers In a MRF accepting fully co-mingled materials, one of the first processing steps involves separating fibre streams (i.e. paper, card, cardboard) from container streams (i.e. cans, plastic bottles, glass bottles/jars). A trommel screen typically is used for this purpose in the UK. In North America disc screens are more common. Depending on the size of the MRF, several stages of screening may be involved. The overall aim is to enable separate fibre and container streams to undergo appropriate sorting.
Sorting fibre To meet market specifications, fibre needs to be sorted into its various grades. Typically, MRFs in the UK sort three grades of paper: OCC (old corrugated cardboard), news & pams (periodicals and magazines), and mixed paper. Some MRFs only sort into OCC and mixed paper whilst some MRFs in North America sort into six grades. Sorting can be done (i) manually, (ii) using disc screens or (iii) using more advanced optical scanners. Smaller MRFs tend to rely on manual sorting, while larger facilities use disc-screens. The use of optical scanners is relatively new and, due to high capital cost, generally confined to high-throughput MRFs. Manual sorting at a MRF.
MRFs that ‘negatively sort’ paper (i.e. allow it to run off the end of the conveyor belt after other materials should have been extracted) have experienced quality-related problems when the materials have been shipped to UK paper mills. In some cases, loads that do not meet UK mill specifications are shipped overseas for recycling. The quality standards set in the UK do not have the clarity of the specifications used in some other countries. MRFs in the UK frequently appear to be guided by rather broad specifications (e.g.