Complex Value Optimization for Resource Recovery (CVORR): A Tool for an Evidence-based Pathway to Circular Economy

Transcription

1 Complex Value Optimization for Resource Recovery (CVORR): A Tool for an Evidence-based Pathway to Circular Economy Maria CORONADO, Eleni IACOVIDOU, Jonathan BUSCH, Phil PURNELL, Costas A. VELIS * University of Leeds, Faculty of Engineering, School of Civil Engineering * Corresponding Author: Costas Velis: School of Civil Engineering Room 304. University of Leeds, Woodhouse Lane, LS2 9JT Leeds, UK. c.velis@leeds.ac.uk Abstract In established linear systems the values of materials are often lost or dissipated into waste ending up in landfills. Europe is proposing a range of measures to accelerate the transition from these linear systems to a more circular economy along the full supply chain. This requires new ways of looking at traditional industrial systems and materials flows, using a systems approach and taking into account multidimensional aspects of value embedded into products, items, components and materials, before they become waste and during their processing for value extraction. Here, we introduce a new methodological framework that combines life cycle inventories with the flow of materials capable of accounting for multiple values (economic, social, environmental and technical) of materials within resource recovery systems. This framework will allow for a whole system analysis of the complex values in waste, considering internal loop, system boundaries, and uncertainty, while extending significantly in the socioeconomic evaluation of the recourse recovery. Complex resource recovery implications of alternative scenarios for product/waste systems will be systematically assessed, including potential changes to the system upstream and downstream of waste generation point. The co-production system of coal-based electricity generation and concrete production is used here to illustrate the basic principles of the model framework. These systems are currently connected by the use of fly-ash, a waste by-product from coal fuelled electricity generation, as an additive in concrete production that replaces some of the cement. This reuse of fly-ash has multiple benefits, including carbon emission reductions and an improvement in the structural properties of the concrete. Interventions in coal electricity generation to introduce biomass or solid recovered fuels as a replacement for coal it increased the biogenic and alternative energy production but it renders the slag unusable as a cement replacement due to the higher alkaline content of the new fly-ash waste increasing so the negative environmental value of slag by making it an unrecoverable waste instead of a secondary raw material. The change in complex dimensions of value in this system resulting from an intervention upstream the waste generation illustrates the need for an integrated, whole systems approach. Keywords: Solid waste management; Resource recovery; Circular economy; Complex value optimisation; Modelling; Framework 1

2 1 Introduction Circular economy and resource efficiency feature in the top priorities of the European Commission (EC), aiming to establish a common and coherent EU framework for sustainable management of resources throughout their life-cycle. The EC is presenting an ambitious revised circular economy package in late 2015 to accelerate the transition to a more circular system of resource flows along the full supply chain. Taking optimal decisions on retaining as much as possible the original value of materials and functionality of products/items/compounds before they become waste, and on recovering value from wastes, require new ways of quantifying traditional industrial production, consumption and resource recovery systems and the underlying materials flows, taking into account all dimensions of value (socio-economic, environmental, technical, and functional) and their mutual trade-offs. Transforming the world into a more resource-efficient place necessitates tools capable of an evidencebased transition to circular economy. There is need to combine economic, technical and social valuation approaches with protection of the environment. The Complex Value Optimization Resources Recovery (C-VORR) research project aims to develop such next generation tools, going beyond conventional methods of estimating value and providing a robust, coherent and impartial approach for making the transition to a resource-efficient future. This new system approach attempts to combine and substantially extend the methodologies of life cycle assessment (LCA) and material flows analysis (MFA), providing so new insights on the performance of systems on circular economy goals. Existing approaches generally consider a single aspect (profit, carbon) at a time e.g. the R1 energy efficiency input-output formula for energy from waste (EfW) operations. Alternatively, they collapse multiple dimensions of value onto just one (usually financial), as in ecosystem services. Life cycle assessment (LCA) is a widely used methodology for assessing the environmental impacts of products and services, including all stages of the life cycle. In LCA, all environmental issues connected with the function of a process, product or activity, within a system, are identified and analysed in terms of various potential environmental impacts. This product need not be a material and hence an LCA model does not necessarily provide a mass balanced description of the system. This is in contrast with material (MFA) and substance flow (SFA) models where activities are linked by the flows of materials or substances only. MFA models are defined by a balance equation where the change in stock of every material in every activity must be equal to the inflow minus the outflow. The proposed novel framework and tool consists of a mass balanced material stock and flow model for the system (MFA) that includes all materials identified as carrying significant value as resources as well as other activities without mass flow links that also contribute significantly to social or environmental impacts (LCA). Trade-offs of the different dimensions of value is considered and optimisation for such multiple values is attempted. 2 Methodology The new methodology under development (Figure 1) aims to study the systems in sufficient detail to enable a transparent illustration of the value of resource flows and how changing system configurations impact on this. The new methodological framework (Figure 1) to assess the complex value implications of alternative scenarios for product/waste systems includes a narrative led identification and the development the dimensions of value that are relevant to a particular system and its stakeholder (framework + value flow analysis models). This is formalised as a set of scenarios for alternative system configurations and metrics that will be used for the value assessment of these scenarios. The assessment is enabled by a model of the stocks and flows of the physical (material, product and energy) constituents as well as the value properties of the system, explicitly considering selection of set of values and metrics for evaluation, internal loops, system boundaries and uncertainty, while extending significantly in the socioeconomic evaluation of the resource recovery. 2

3 Figure 1. Integrated whole system approach to recover value from complex waste processing systems The framework is co-developed with a set of four case studies which inform the methodologies for value selection, scenario and metric development, and modelling approach. The methodology can be applied to any industrial system to find optimal pathways for different sets of values in any point of the supply chain (downstream/upstream) to capture and retain values currently wasted or dissipated into waste. In this work, the co-production system of coal based electricity generation and concrete production is used to illustrate the model framework. 3 Results and discussion Fossil fuel based electricity generation and concrete production are both major contributors to the total carbon emissions of the UK. Coal fired power stations are the most carbon intensive and polluting parts of the UK s energy system. The only potential to reduce carbon emissions from this process is to use carbon capture and storage (CCS), or to use biomass / partly biogenic solid recovered fuels (SRF) to replace some of the coal. Concrete production is carbon intensive primarily because of the very high temperatures required for making cement. Carbon emissions in concrete production can be reduced by replacing some of the cement in concrete with alternatives such as, coal fly-ash, a waste product of coal electricity generation. The benefit of replacing some cement with fly-ash is not only evident in reducing the associated carbon emissions, but also by improving the structural properties of the concrete. The two production systems are hence linked as the by-product of the one is used as the raw material of the other. The policy pressure to reduce carbon emissions is leading coal fired power stations to convert to biomass and /or SRF co-firing. Coal fly ash has been used as a technical addition for concrete for years and a decision to partially replace coal with either biomass or SRF with the aim of reducing carbon emissions and costs could come with significant side-effects. One of these is the increase in the alkaline and unburnt carbon contents of the fly-ash waste, rendering it less usable / unusable as a cement substitute in concrete. This would lead to the disposal of the fly-ash by-product, breaking the 3

4 Flyash Book of abstracts of WASCON 2015 Resource Efficiency in Construction chain that links the electricity with the cement production system and diminishing the value recovered from the fly ash. The analysis of the environmental, technical, economic and social value of the co-production system of coal based electricity generation and concrete production, and the implications imposed on this based on the new scenario (Figure 2), is going to provide insights to the potential recovery of value. ELECTRICITY CONCRETE Coal Biomass or SRF Electricity Concrete Bottom ash Water Aggregate Cement Concrete waste ELECTRICITY CONCRETE Coal Electricity Fly ash Concrete Bottom ash Water Aggregate Cement Concrete waste Figure 2. Co-production system of coal based electricity generation and concrete production: co-combustion of biomass or solid recovered fuels (SRF) changes the properties of fly ash, rendering it less suitable for concrete production. 4 Conclusions The innovative, powerful framework and tool that is going to be developed for enabling the evaluation of various resource recovery systems based on the multiple dimensions of value will allow researchers and industry practitioners to: Obtain better knowledge and take optimal decisions over systems and their material flows. Identify where resource-related values are lost or dissipated within the system. Exemplify potential loops based on circular economy goals and mechanisms to capture different dimensions of values along the full supply chain (upstream and downstream). Assess the effects of interventions on the performance of the system. Establish new economic models that prevent value dissipation and promote value creation according to the goals of circular economy. 4

5 Acknowledgements Book of abstracts of WASCON 2015 Resource Efficiency in Construction This research is funded by the Natural Environment Research Council (NERC) and the Economic and Social Research Council (ESRC) (grant number: NE/L014149/1), with additional support from the Department for Environment, Food & Rural Affairs of UK (DEFRA), and in kind contribution from an extensive network of Project Partners and Supporters, to whom we express our gratitude. Opinions expressed here are the authors alone. 5