ORIGINAL PAPER A methodology for criticality analysis in integrated energy systems Michael Francis D. Benjamin • Raymond R. Tan • Luis F. Razon Received: 4 July 2014 / Accepted: 2 September 2014 / Published online: 9 October 2014 Ó Springer-Verlag Berlin Heidelberg 2014 Abstract Integrated energy systems (IES) such as poly- generation plants and bioenergy-based industrial symbiosis (BBIS) networks offer the prospect of increased efficiency and reduced carbon emissions. However, these highly- integrated systems are also characterized by the strong interdependence among component units. This interde- pendency results in the risk of propagation of cascading failures within such networks, where disturbances in the operation of one component results in ripple effects that affect the other units in the system. In this work, a novel criticality index is proposed to quantify the effects of a component unit’s failure to run at full capacity within an IES. This index is defined as the ratio of the fractional change in the net output to the fractional change in capacity of the component causing the failure. The component units in the entire system can then be ranked based on this index. Such risk-based information can thus be used as an important input for developing risk mitigation measures and policies. Without this information, risk management based only on network topology could result to counter- intuitive results. A simple polygeneration plant and two BBIS case studies are presented to demonstrate the com- putation of the criticality index. Keywords Integrated energy systems  Polygeneration  Bioenergy-based industrial symbiosis  Input–output model  Criticality index List of symbols AD Anaerobic digestion plant B Boiler unit BBIS Bioenergy-based industrial symbiosis BEP Bioethanol plant BDP Biodiesel plant BGP Biogas plant C Cooling CCS Carbon capture and storage CE Cement CH Chiller unit CHP Combined heat and power unit/plant CIS Critical infrastructure systems D Biodiesel E Bioethanol EIP Eco-industrial parks G Biogas GHG Greenhouse gas H Heat IES Integrated energy systems IO Input-output IS Industrial symbiosis M Malt MP Malt plant P Power RO Reverse osmosis unit SL Synergistic link W Treated water Mathematical nomenclature A Process matrix x Component unit capacity vector y Final output vector n Number of system component units/main product streams M. F. D. Benjamin  R. R. Tan (&)  L. F. Razon Chemical Engineering Department, De La Salle University, 2401 Taft Avenue, 0922 Manila, Philippines e-mail: raymond.tan@dlsu.edu.ph M. F. D. Benjamin Chemical Engineering Department, University of Santo Tomas, Espan ˜a Blvd, 1006 Manila, Philippines 123 Clean Techn Environ Policy (2015) 17:935–946 DOI 10.1007/s10098-014-0846-0