Optimising Environmental Performance of Symbiotic Networks Using Semantics Franjo Cecelja, Nikolaos Trokanas, Tara Raafat, Mingyen Yu Centre for Process & Information Systems Engineering, Faculty of Engineering & Physical Sciences, University of Surrey, Guildford, GU2 7XH, United Kingdom Abstract The paper introduces a semantic algorithm for building Industrial Symbiosis networks. Built around ontology modelling of knowledge in the domain of IS, the algorithm enables the acquisition of the explicit knowledge from the user through ontology instantiation and input/output matching based on semantic relevance between the participants. Formation of innovative Industrial Symbiosis networks is enabled by decomposition of parameters characterising respective resources and solutions, the process optimised for set environmental criteria. The proposed algorithm is implemented as a web service. The potential of the algorithm is demonstrated by several case studies using real-life data. Keywords Industrial symbiosis, Ontology, Semantic matching 1 Introduction Based on the principle of industrial ecology to reduce the use of virgin materials and energy by reusing water, recovering energy and utilising by-products, the items commonly called waste, Industrial Symbiosis (IS) describes the industrial network. Usually set on an ad-hoc principle IS networks focus on trading material, energy and water to gain economic, environmental and social benefits (Lehtoranta et al. 2011). Ad-hoc principle refers to collaboration between companies which normally do not have established consumer/supplier relationship and which occurs within strict geographical and environmental boundaries (Chertow 2004). Economic benefits are generated by the cost efficiency coming from the off-market prices of waste material and energy generation and they are driving force for private industry to participate. Tighter integration enables further economic savings through cascading of water and energy and sharing utilities and services and hence yielding collective benefits greater than the sum of individual benefits (Jae- Yeon et al. 2006). Tighter integration is also justified by environmental and social grounds. By focusing on reuse of waste, energy and water, environmental benefits are integral part of IS, which include landfill and pollutant savings, reduction in greenhouse gas generations, improved resource use efficiency and reduced use of non-renewable resources (Mirata and Emtairah 2005; Chertow 2007; Trokanas et al. 2013). These benefits are further amplified by geographical boundaries and localised operation. Some authors claim that localised operation of IS provides measurable outputs in revitalising urban and rural sites, promotes job growth and retention and encourages more sustainable development (Desrochers 2004; Jacobsen 2006; Chertow 2007; Lehtoranta et al. 2011; Chertow and Ehrenfeld 2012). It has been proven that environmental and social benefits are driving force behind the interest of city planners, economic development experts and real estate developers and agencies to take proactive role and to participate and promote (Chertow 2004; Alberta and Kevin 2008). In practice, IS occurs locally or regionally as spontaneous process or promoted and otherwise supported by states or regions. Key to establishing symbiosis is the matching of inputs and outputs to make links across