Overview

Project Highlights:

  • A circular economy aims to keep products, components, and materials at their highest utility and value at all times, and to minimise loss of resources through, for example, disposal to landfill.
  • Waste derived fuel (WDF) is any fraction recovered from any type of waste which can be thermally used. This project will focus on the non-hazardous waste component called Refuse derived Fuel (RDF) and will undertake a systematic characterisation of the calorific value, moisture, ash contents, metal contents, and scope for generation of other potential pollutants during combustion of RDF produced by different combinations of mechanical and biological treatment (MBT) plants, as part of an overall risk assessment.
  • The project will also support the development of UK policy related to RDF, including recommendations for standardisation of specifications for RDF and promotion of development of district-level waste-management solutions such as that in Rugby which produces fuel from wastes collected from Warwickshire, Northamptonshire and the Midlands.

As envisioned by the originators, a circular economy is a continuous positive development cycle that preserves and enhances natural capital, optimises resource yields, and minimises system risks by managing finite stocks and renewable flows. It works effectively at every scale. Minimising waste & recovery from waste is one key component of a circular economy. Energy recovery from enriched waste materials (such as RDF) can reduce consumption of fossil fuels and meet climate change emission reduction targets.  Additionally, it diverts wastes from landfill and incinerators which has obvious environmental implications. RDF typically consists of paper, plastics, textiles and other combustible materials produced after removal of glass, grit, ferrous materials, etc. from waste.  RDF can be generated by mechanical plants which shred and segregate the waste or by MBT plants which in addition to shredding and sorting, treat the organic/biological fraction of the waste. MBT plants are specifically suited to enrich waste for energy recovery and to recover economically valuable recyclables from mixed waste (black bag waste – see Figure 1). 

RDF can be utilised as a source of fuel in co-combustion facilities, such as power plants, cement kilns, pyrolysis and gasification plants and mono-combustion facilities such as Waste to Energy (WtE) plants as a secondary fuel.

The UK exports around 2.5 Million Tonnes of RDF per year. Characterisation (both physical and chemical) of RDF from different generators is imperative to improve the utilisation of these wastes in different industrial processes, and to explore potential environmental impacts and greenhouse gas emission reductions. That is the goal of the current project.

There is no formal definition, quality standard or specification for RDF in either UK or EU legislation. However, there is a specification for Solid Recovered Fuel (SRF) as per the British Standards (BS EN 15359:2011), in terms of technical requirements (Chlorine amount), environmental requirements (Mercury emissions), and economic requirements (Net Calorific Value). Technical standards for RDF (which are envisioned to be proposed based on this project) and characterisation of RDF from different sources can help to ensure its optimum utilisation in co-combustion plants, and its re-use in the circular economy rather than loss to landfill or incineration.

Two key configuration of Mechanical and Biological Treatment plants to produce RDF

Methodology

Surveys to inventorise different sources of RDF production  (commercial, industiral, domestic) and details of industries where RDF could be potentially used will be undertaken. Paramaters that could impact the operational porcess in co-combustion facilities will be assessed. Hence, particle size, physical form (powder and pellet), heavy metal content, moisture content and ash content will be anlaysed for the individual samples collected from different sources across the UK.  For economic reasons, calorific value is key and determination of biogenic content of the RDF will help to calculate financial benefits acruing via the Renewables Obligation Certificates for RDFs produced in the UK.  Chlorine (total) and water soluble chloride, Mercury, Aluminium, Suplhur, Nitrogen, other trace metals and volatile matter will be assessed which can influence the emission profile.

Characterisation results of the RDF from various MBT plants in the UK (e.g. PHS, Skansas, Biffa, Lancashire  Waste and Recyling , Sita UK, and others) will be compared with the reported RDF characterisation values from EU countries, such as Germany, Netherlands, Italy and Spain, and correlated with pocessing steps and input waste composition profiles.

Training and Skills

CENTA students are required to complete 45 days training throughout their PhD including a 10 day placement. In the first year, students will be trained as a single cohort on environmental science, research methods and core skills. Throughout the PhD, training will progress from core skills sets to master classes specific to the student's projects and themes. 

Project-specific training will be provided in heavy metal analysis, combustion analysis, extraction and characterisation, and in development of policy briefings and demonstration case studies for industry and regulators. A key outcome from the project will be input to development of standards for RDF and support to build the economic case for further utilisation of RDF as a fuel resource rather than a waste product to encourage investment nationally.

Timeline

Year 1: Gather data by conducting surveys of various RDF manufacturers in the UK and determine the major categories and amount of waste in each that are used to produce RDF. Acquire RDF samples from as many sources in the UK as possible, and begin physico-chemical characterisation (parameters listed in Methodology, starting with metals content and leeching of metals).  If RDF collected has the potential to be contaminated from infectious/clinical waste, microbial analysis will be performed. 1st paper.

Year 2: Gather detailed description of the technology and operational steps of various co-combustion plants operating in the UK (through surveys and published literature) which can potentially use RDF and determine specific criteria for utilisation of RDF in the UK.  Determine the subsidies that can be earned (or potential reduction in green house gas emissions and other environmental impacts) due to co-combustion of RDF in plants in the UK for various scenarios of utilisation in comparison to fossil fuels or other substitute fuels. Quantification of the potential for release of dioxins and overall calorific value of the various RDF samples, and initial mapping of these data back to the composition (% wood, paper, plastic etc.) contained in the various RDFs.  2nd paper.

Year 3: Assessment of the size and total surface area (nanoscale) of the metal contents in the RDF to predict environmental risks.  Model scenarios of metal release from RDF when stored for longer times, and assess biological implications of the released metals via mibrobial screens.  Submission of papers & thesis.

Partners and collaboration (including CASE)

Prof. Lynch is already collaborating with PHS who are piloting the production of RDF from one of their sites close to Birmingham, as a means to reduce the amount of waste going to landfill.  Specifically, we are undertaking a Lifecycle Assessment their old and new processes to compare the relative environmental footprints and built a case for the RDF-circular economy approach with waste becoming a resource. 

Further Details

Please contact Prof. Iseult Lynch, University of Birmingham, i.lynch@bham.ac.uk for further details.