• To understand and quantify energy usage associated with the collection, separation, processing and disposal of the materials that constitute MSW;

• To produce a model of the energy and materials balance that can be used for evaluation and comparison of alternatives and combinations of options for the management of MSW

Description and Methodology
The aim of the project is to identify and promote sustainable urban waste management practice by developing tools for rational assessment and comparison of different options, taking into account both energy and materials flows. The city of Southampton will be used as an initial case study for the model development, and the research team will work closely with the local authority and the Project Integra waste management group. The work will involve the following tasks and activities:

• Types and quantities of wastes generated: Identification of the types and quantities of municipal solid waste (MSW) generated and their ultimate disposal routes (including re-use, recycling, recovery) will be carried out on the basis of analysis of existing waste stream collection and disposal data, supplemented where necessary by additional surveys and sampling;

• Collection methods: Existing and potential collection methods (eg. conventional refuse collection, integrated source separation, kerbside collection of recyclables, drop-off, CA sites) will be identified, and typical energy requirements determined related to tonnages, taking into account vehicle type, mileages, transfer operations, volumes, special requirements for materials segregation etc. This will be based on operational data from participating organisations, compared with and supplemented by calculated values and information in published literature;

• Unit sorting operations: Unit sorting operations in different types of materials recovery facility will be identified and typical energy requirements determined in relation to tonnages of recovered materials. This work will be carried out in conjunction with waste management contractors and specialist groups involved in the design and operation of sorting facilities;

• Reuse / recycling / recovery options: This will establish the energy required or generated by different re-use/recycling/recovery options (including bio-processing and combustion) for a range of materials (glass, paper, plastics, organics, metals). The work will initially be based on an extensive survey of existing data, in conjunction with trade associations, industry bodies, specialist networks and interest groups;

• Exceptional materials: It will be necessary to identify material flows not covered in the above analysis (eg. white and electronic goods, end-of-life vehicles, hazardous materials) and to propose methods for establishing an energy balance for their re-use, recovery or disposal. In each case a basic approach will be put forward, and where possible additional data will also be gathered in specific projects in the Consortium’s programme (eg. Projects 5, 6, 7);

• Final disposal of residuals: This work will establish the energy inputs and outputs related to final disposal of residuals after different processing options (eg. site restoration; energy recovery from methane; energy costs for leachate treatment). The work will draw on team members’ expertise, supplemented by published results and data from partner organisations;

• Model construction: The modelling approach will initially be piloted by deriving the energy balances and formulae associated with different collection, sorting, reprocessing and/or disposal routes for a single selected material or component of the waste stream. Once the approach has been verified, the model will be extended to cover a full range of materials, to allow calculation of an overall energy balance and materials flows associated with different management options within the study area. The model will be validated by comparison with data from other sources where this is available: it is anticipated that the amount of suitable data will be limited, and it will therefore be necessary to develop alternative engineering methodologies for validation. Data used for modelling and the model results will be tested against existing data where these are available, and will be submitted to experienced individuals in different sectors of the waste management industry for critical appraisal of the techniques and results. Sensitivity analysis will be carried out to identify areas where more data are required for a fully robust and comprehensive model;

• Modelling scenarios and production of energy footprints: The model will be run for a series of different scenarios, to explore the effect on the overall energy balance of changes in current collection, sorting, processing and disposal options in the study area. Materials flow patterns will be explored leading to the most favourable energy and materials balance (ie. the most sustainable use of resources once material has been designated as waste). Techniques and practices will be identified where energy expenditure outweighs any potential benefit from the operation being conducted, or where improvements in efficiency have a significant impact on the energy balance. The analysis will consider the potential for implementation of proposed alternatives, including land use implications and benefits from associated projects. The results will provide both specific information on the study area, and general conclusions.

The proposed project consists of two stages. The first stage will involve data collection and development of a basic model structure. In this stage, the focus will be on gathering existing, readily-available data from industry and literature sources, life cycle analyses etc. It is anticipated, however, that data on certain processes and waste streams (eg. novel thermal technologies, separate collections for bulky wastes) will be scarce: as mentioned above, a number of the Consortium’s projects have therefore been set up specifically to obtain these data and/or an improved understanding of the processes involved. The second stage will therefore consist of three main components: additional data collection and development of approaches for problem areas; extension, updating and testing of the model in the light of incoming information; running of more advanced and sophisticated what-if scenarios; and development of a user-friendly interface to allow full utilisation as a research and planning tool. The work will be carried out by Southampton with advice from Surrey and Imperial College.

Deliverables
   Deliverables from the project will include:

1. A database of energy usage for different unit operations in the collection, sorting, processing and disposal of key components in the municipal solid waste stream.

2. A mass balance for materials in the study area taken from the point at which they are categorised as waste, to their final reuse, recycling or disposal.

3. A mechanistic model in the form of a flowchart-based spreadsheet for calculation of the overall energy and materials balance for different waste management options.

4. A manual describing the basis of the model, to allow modification and customisation by users elsewhere.

5. A report including an assessment of current and alternative scenarios for the greater Southampton area, identification of areas where improvements in technology or operational practice would have a significant impact on energy and materials balances, and proposals for future work.

6. Publications describing the project findings, in the form of articles in industry, professional and scientific journals and web-based materials.

Contributions to Waste Consortium Headline Objectives
This project is central to the headline objectives, as it provides a tool for rational comparison of urban waste management options. The project focuses on energy, but makes a major contribution to full understanding of the resource cycle. The process of model development also provides a framework for analysis of other environmental, social and economic factors and a basis for policy formation.