Christof Knoeri currently works as a Postdoctoral Reserach Fellow at the Sustainablity Research Institute in February 2012 . Prior to this he was a Research Associate at the Life-Cycle Assessment and Modelling Group at Empa Materials Science & Technoloogy, Switzerland where he also did his PhD. In addition, he worked as a Guest Lecturer at the Institute for Systems Science, Innovation & Sustainability Research at the University of Graz, Austria and at the Chair for Human-Environment Relations at the University of Munich, Germany. His research interests are modeling human-emvironmental systems in general and agent-based modeling in particular. He is currently working on the EPSRC funded "The land of the MUSCos" project.
Abstract: Construction and demolition (C&D) waste, being already the largest waste fraction in industrialized countries, is expected to increase in the future. C&D waste recycling has been considered to be a valuable option not only for minimizing C&D waste streams to landfills but also for mitigating primary mineral resource depletion. Even though the use of recycled mineral construction materials (RMCM) is regulated and successful application examples are available, construction stakeholders do not yet broadly apply them. Although various criteria hindering a transition towards a broader application of RMCM have been identified, it is yet unknown how these criteria differ among decisions, stakeholders and applications. We therefore analyze construction stakeholders’ behavior, and decision-making regarding RMCM for the construction material market in Switzerland. Stakeholders’ decision-making was quantified with the analytical hierarchy process (AHP) in a survey in combination with their behavior. The results demonstrate
the importance of stakeholder interaction, i.e. most stakeholders decide which material to apply based on interaction with other stakeholders e.g., recommendations and specifications. However, the initial general specification by awarding authorities that construction should be sustainable has little relevance to the subsequent material decisions. On the contrary the role of the recommendation of engineers, have a high impact on the subsequent decisions by the other stakeholders. Results also confirm that RMCM are broadly accepted in civil engineering (CE), whereas in structural engineering (SE) RMCM are still a niche product. The good alignment of the outcome of decision modeling with observed behavior shows the usefulness of analyzing decision-making with AHP.
Abstract: The potential of agent-based modeling (ABM) has been demonstrated in various research fields. However, three major concerns limit the full exploitation of ABM; (i) agents are too simple and behave unrealistically without any empirical basis, (ii) 'proof of concept' applications are too theoretical and (iii) too much value placed on operational validity instead of conceptual validity. This paper presents an operationalization approach to determine the key system agents, their interaction, decisionmaking and behavior for context specific ABM, thus addressing the above-mentioned shortcomings. The approach is embedded in the framework of Giddens' structuration theory and the structural agent analysis (SAA). The agents' individual decision-making (i.e. reflected decisions) is operationalized by adapting the analytical hierarchy process (AHP). The approach is supported by
empirical system knowledge, allowing us to test empirically the presumed decision-making and behavioral assumptions. The output is an array of sample agents with realistic (i.e. empirically quantified) decision-making and behavior. Results from a Swiss mineral construction material case study illustrate the information which can be derived by applying the proposed approach and demonstrate its practicability for context specific agent-based model development.
Abstract: Emerging technologies such as information and communication-, photovoltaic- or battery technologies are expected to significantly increase the demand for scarce metals in the near future. The recently developed methods to evaluate the criticality of mineral raw materials typically provide a ‘snapshot’ of the criticality of a certain material at one point in time by using static indicators both for supply risk and for the impacts of supply restrictions or economic importance. While allowing for insights into the mechanisms behind the criticality
of raw materials, these methods cannot account for continuous changes in products and/or activities over time. We propose an approach which goes beyond this static state of the art insofar as it includes the dynamic interactions between different possible demand and supply configurations as a precondition for the evaluation of criticality. The framework developed integrates an agent-based behavior model, where demand emerges
from individual agent decisions and interaction, into a dynamic material flow model, representing the materials’ stocks and flows across their lifetime. Within this framework, the evaluation of criticality is exemplarily specified for the environmental dimension by applying life-cycle assessment methodology.
Abstract: This paper provides an input to the question on how socio-ecological transitions can be empirically simulated. Socio-ecological transitions are characterized by a non-linear development process depending on the interaction between individual behaviour, social structure, and environmental conditions. These transitions can be viewed as emerging phenomena, similar to the process of innovation and imitation, and therefore can be simulated utilizing agent based modelling (ABM). ABM has mostly been applied to simulate socio-ecological transitions on a theoretical level; the empirical applications relate to land use and land use change. One of the major difficulties is to operationalize and quantify the relationship between individual action and social structure. We present an approach relying on Structural Agent Analysis and show how this qualitative method can be used as a basis to develop quantitative rules describing the emergence of social structure phenomena. This workshop has two aims: First, to provide a typology of issues in socio-ecological transitions which have been empirically simulated with ABM. Second, to discuss methodologies for an operationalization and quantification of (i) agent rules; and (ii) interactions among agents on the one hand and between agents and the environment on the other hand, each in the context of socio-ecological transitions.
Abstract: With the increasing scarce metals demand from emerging technologies such as information-, photovoltaic- or battery technologies, a (scientific and public) debate has arisen over the ques-tion, if the diffusion of these technologies could possibly be limited by future supply restrictions for mineral raw materials. Recently, several indicator-based assessment methods have been developed to evaluate the criticality of mineral raw materials, for example by the National Research Council or the European Commission. The main drawback of these methods is that they typically provide a ‘snapshot’ of the criticality of a certain material at one point in time by using static indicators for supply risk and impact of supply restrictions or economic importance. Although these methods provide insights into the mechanisms behind the criticality of raw materials, they cannot account for changes in products or activities over time. Moreover, they do not fully consider the evolution of background systems on which these products or activities depend (e.g. energy - and raw material supply chains).
The approach we propose goes beyond this state of the art insofar as it includes dynamic interactions between different possible demand and supply configurations as a precondition for the evaluation of criticality. In our integrated framework, demand emerges from individual agent decisions, while the supply chain is represented by material stocks and flows. As a consequence, the framework links an agent-based demand model with a dynamic material flow model. In addition, it also includes a module for the subsequent evaluation of criticality, which is exemplarily specified for the environmental dimension of criticality by applying life-cycle assessment methodology. In our contribution we will sketch the framework and discuss first experiences from its implementation in a case study related to rare earth elements.
Abstract: Large and growing amounts of construction waste are produced annually in Switzerland. Even tough in 1997 82% of the mineral construction waste in Switzerland was
recycled, the recycling rates differed significantly across regions. Furthermore, though technical solutions for higher applications are available, reused mineral construction
materials are usually used for low-grade applications. These phenomena are mostly related to decisions made at the level of the individual system agents. Throughout the preconstruction phase, interacting stakeholder groups i.e. contractors, architects, engineers and awarding authorities, decide about the application of different construction materials. They consider mainly technical, economic and aesthetic attributes. The ecological aspect of different mineral material applications is largely neglected. That is, the stakeholders’ behavior regarding the construction material choice, having ecological consequences, is basically determined by others than ecological considerations.
We present an approach to analyze and operationalize multi-attribute decisions based on the analytical hierarchy process (AHP) for an agent based model (ABM). AHP as a multi attribute utility method allows for considering the ecological utility besides the dominating technical and economic attributes of different material application options. Additionally, AHP consistency analysis provides empirical information about the type of decision to be implemented in the ABM.
Abstract: Large and growing amounts of construction waste are produced annually in Switzerland. Even tough in 1997 82% of the mineral construction waste in Switzerland was recycled, the recycling rates differed significantly across regions ranging from 67% in the Canton of Basel City to 87% in the Canton of Valais. In order to support policy and industrial decision-makers and give recommendations for a sustainable construction material management, we analyze and model the supply and demand for recycling mineral construction materials (RMCM). In doing so, we combine an agent based decision-making model of the RMCM demand with a regionalized material flow model of RMCM supply.
The analysis shows that the demand for RMCM is determined by four interacting agent groups i.e. contractors, architects, engineers and awarding authorities. Their decisions are based on various internal (e.g. personal experience, image or social desirability) and external (e.g. material prices, law, norms and trends) decision parameters. The supply for RMCM is manly driven by the regional building and infrastructure stocks and their life cycles defined by the local construction, reconstruction and demolition rates. The main influencing factors for the RMCM demand model (decision parameters) and supply model (building and infrastructure stocks and flows) both show spatial differences. Considering a combination of the two models highlights that their influencing factors are mutually dependent on two levels; on the individual level (e.g. personal experience depends on the utilized materials in construction) as well as on the regional level (e.g. RMCM prices depend on the local construction waste flows). We present and discuss an integrative modeling approach which captures both the spatial variability of the main influencing factors and their interdependencies on the individual and regional level.
Abstract: Introduction
Large amounts of construction waste are produced annually in Switzerland. The volume of 11 million tons in 1997 are likely to increase in the future because of the increasing requirements of accommodation space per capita and the decreasing availability of construction land, leading to demolition of old buildings. In 1997 the overall recycling rate of construction waste in Switzerland was quite high (82%), ranging from 67% in the Canton of Basle City to 87% in the Canton of Valais. That is, in Switzerland recycling is not equally accepted nor applied in all regions. Even though technical solutions for higher applications are available, reused mineral construction materials from buildings are usually down-cycled and used as uncompounded foundation layers.
The aim of the study is to support policy and industrial decision-makers and give recommendations for a sustainable construction material management. For doing so, we developed a comprehensive simulation approach consisting of.
1. A material and energy flow model simulates the amount of applied construction materials and supplied secondary products and the associated energy flows in different scenarios.
2. Based on individual agents’ decisions and interactions, a decision-making model simulates the demanded construction materials with agent based modeling.
3. The combination of the decision-making with the material and energy flow model allows for the assessment of the ecological sustainability of different scenarios.
This poster focuses on the decision-making model. We present an approach to analyze the decision-making structure i.e. decision interaction, options, decision parameters of the main system agents, providing a basis for the simulation of the decision process with agent based modeling.
Decision-making model
Introduction decision-making: Recycling rates and applications are mostly related to decisions made at the individual system agents’ level. It is considered that parameters such as image of recycling materials, risk perception, lack of experience with alternative materials or lack of trust on recommendations have an important influence on reducing demand for recycling material. Furthermore, the demand for recycling construction materials is not only determined by the decisions of one agent group. Several agent groups i.e. contractors, architects, engineers and the awarding authorities interact and are likely to have different ways to impact the system. However, to the authors` knowledge, so far, it has not been analyzed what the decision-structure of these agents are, how their decisions interact, and how they cumulatively affect the demand for recycling materials.
Method: With a system impact analysis we identified the important system agents regarding the utilization of recycling construction materials. Their decision-structures (decision interaction and options) were develo¬ped in semi-structured expert interviews. We determined the decision-making parameters (criteria) in an expert work¬shop. The criteria weights representing the importance of a certain criteria were operationalized in a survey. Finally the decision-making processes of the agent groups were implemented in an agent based model.
Preliminary results: The results show the specific decision matrixes regarding the utilization of recycling materials for each agent group and how the relevant agents interact. Each decision is based on various internal (e.g. personal experience or social desirability) and external (e.g. material prizes or norms and laws) decision criteria. These criteria vary among the agent groups e.g. private awarding authorities decide on construction specification considering social, economic and ecological aspects. The social aspects include image and trend of recycling construction materials and the social desirability of sustainable buildings. For public awarding authorities the social aspects additionally include the governmental policies for sustainable construction. Within each stakeholder group the decision criteria are the same, but their importance (weight) is different at the individual agent level. One awarding authority makes the construction specification considering almost only economic aspects whereas another awarding authority might focus more on social and ecological aspects. The interaction between the agents finally leads to a specific demand for recycling materials.
Conclusion
This procedure shows how to identify the important system agents, survey their decision-making structure and interaction and how to determine their decision-making parameters. Furthermore, we will show how the results can be integrated in a broader system simulation allowing for a sustainability assessment of different scenarios based on individual decision-making processes.
Abstract: Large amounts of building materials are demanded annually in Switzerland. The volume of 60 Million tons new building resources used in 2002 are likely to increase in the future because of the increasing requirements of accommodation space per capita. On the other hand, more and more mineral construction waste will be generated due to deconstruction or demolition of old buildings. Closing material cycles is technically feasible to a certain extent and might provide economic and ecologic benefits depending on various situational and contextual factors. However, potential (economic and ecologic) benefits are often not realized since decisions to use recycled mineral construction materials are not made by a single, well informed decision maker but by the interaction of various actors. Furthermore, the main agents affecting the demand for recycled mineral construction materials, i.e., contractors, architects, engineers and the awarding authorities, are likely to have different ways to impact the system. However, to the authors` knowledge, it has never been analyzed how these agents make their decisions, how their decisions interact, and how they cumulatively affect the demand for recycling materials.
The present study analyzes the decision structure of the important system agents and simulates the process with agent based modeling (ABM). ABM allows for generating results concerning present and future demands based on agents´ decision trees. In our study we build a specific decision tree regarding the utilization of recycling materials for each agent group. Each decision in these trees is based on various internal (e.g., required accommodation space or personal experience) and external (e.g., material prizes or norms and laws) parameters. Decisions are modeled based on probabilities, e.g., a higher demand for recycling materials occurs if these materials are recommended by the Canton; a lower demand results from a lacking competitiveness against virgin materials. The interaction between the agents finally leads to a specific demand for recycling materials. Changes in the internal and external parameters are modeled in form of scenarios providing different input values. The decision trees are developed in semi-structured expert interviews and calibrated against the agents´ behavior analyzed in structured interviews from a larger sample. We will present several scenarios for recycling of construction materials and discuss the effects of planned policies regarding the demand for recycling materials and the environmental consequences.
Abstract: Large amounts of construction waste are produced annually in Switzerland. The volume of 11 million tons in 1997 are likely to increase in the future because of the increasing requirements of accommodation space per capita and the decreasing availability of construction land, leading to demolition of old buildings. In 1997 the overall recycling rate of construction waste in Switzerland was quite high (82%), ranging from 67% in the Canton of Basle City to 87% in the Canton of Valais. Reused mineral construction materials from buildings are usually down-cycled and used as uncompounded foundation layers. That is, in Switzerland recycling is not equally accepted nor applied in all regions. These emergent phenomena are mostly related to decisions made at the level of the individual system agents. It is considered that parameters such as acceptance, risk perception, lack of experience with alternative materials or lack of trust on recommendations have an important influence on reducing demand for recycling material. Furthermore, the main agents affecting the demand for recycling construction materials, i.e., contractors, architects, engineers and the awarding authorities, are likely to have different ways to impact the system. However, to the authors` knowledge, so far, it has not been analyzed what the decision-making trees of these agents are, how their decisions interact, and how they cumulatively affect the demand for recycling materials.
The present study analyzes the decision structure of the important system agents and simulates the process with agent based modeling (ABM). ABM allows for generating results concerning present and future demands based on agents´ decision trees. In our study we build a specific decision tree regarding the utilization of recycling materials for each agent group. Each decision in these trees is based on various internal (e.g., required accommodation space or personal experience) and external (e.g., material prizes or norms and laws) parameters. Decisions are modeled based on probabilities, e.g., a higher demand for recycling materials occurs if these materials are recommended by the Canton; a lower demand results from a lacking competitiveness against virgin materials. The interaction between the agents finally leads to a specific demand for recycling materials. Changes in the internal and external parameters are modeled in form of scenarios providing different input values. The decision trees are developed in semi-structured expert interviews and calibrated against the agents´ behavior analyzed in structured interviews from a larger sample. We will present several scenarios for recycling of construction materials and discuss the effects of planned policies regarding the demand for recycling materials.
