Allocation of GHG emissions in combined heat and power systems: a new proposal for considering inefficiencies of the system Remei Aldrich, F. Xavier Llauró, Josep Puig, Pere Mutjé, M. Àngels Pèlach * Lepamap Group, Dept. EQATA, Universitat de Girona, Campus Montilivi, Edifici P-I, 17071 Girona, Spain article info Article history: Received 29 July 2010 Received in revised form 17 February 2011 Accepted 18 February 2011 Available online 4 March 2011 Keywords: Cogeneration Emissions allocation Greenhouse gas emissions Paper industry Real CHP analysis abstract The paper industry is responsible for a considerable amount of greenhouse gas (GHG) emissions mainly due to its intensive energy requirements. The production of heat and power streams in a cogeneration system, i.e., a combined heat and power (CHP) plant, releases considerable amounts of GHG emissions into the atmosphere. Such emissions are already subjected to legislation globally. The amount of GHG emissions is usually calculated from the product of the total amount of energy activity multiplied by an emission factor. However, each energy output stream should get a share of emissions responsibility. This fact could assist in assigning weights to the emissions generated for power and thermal purposes in a combined heat and power plant. However, developing a suitable method of allocating emissions in a cogeneration system is still a concern and a subject research for scientists, companies and policy makers. This paper exposes and evaluates different published allocation methods and applies them to a real case of a combined heat and power plant integrated in a paper mill and proposes a new allocation method. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Improvements in reviewing, auditing and reporting greenhouse gas (GHG) emissions are becoming a major focus of interest for researchers and energy intensive industries like the paper industry (Avs ¸ ar and Demirer, 2008; Silvo et al., 2009). The paper industry is responsible for a considerable amount of GHG emissions, mainly due to its intensive energy profile (Thollander and Ottosson, 2010). According to Business Europe (2007), the Spanish pulp and paper sector was in 2007 the European leader in combined heat and power (CHP) plants. Moreover, the most recent sustainability reports of the Association of Spanish Pulp and Paper Manufacturers (ASPAPEL, 2009) added that this sector had installed nearly 60 CHP plants since 1990 and transformed the sector from a large elec- tricity consumer into an integrated energy business operation producing electricity efficiently. CHP plants provide great benefits to the pulp and paper industry, such as reliable power supply with consistent quality and efficient energy generation due to the simultaneous generation of steam and economic profit by selling electricity to the market pool. Therefore, emissions related to combined heat and power production should be determined and analysed in detail to set the appropriate targets and invest in successful emission reducing measures Different methods to correctly attribute CHP emissions to power and heat production have been published in the literature. The papers of Strickland and Nyober (2002), Rosen (2006a,b, 2008, 2009) and the GHG pulp and paper tool guidance (ICFPA, 2005) presented some common features. All of them estimate CHP system emissions based on fossil fuel combustion, after which they allocate total emissions along the different useful output energy streams, i.e., heat (steam or hot water) and power. The allocations are based on different criteria, which can be thought of as efficiency and thermodynamic methods, as shown in Fig. 1 . The efficiency method is based on the efficiency of the main facilities of the CHP, whereas the thermodynamic method is focused on the physical stage of the output streams. This paper analyses these methods and rearranges them to have a consistent unit base and mathematical equations, then applies the methods to a real scenario. In addition, a new method is proposed and is compared with the other two methods. 2. A description of the allocation methods A typical CHP plant configuration is presented in Fig. 2, and is used to compare the different allocation methods (Aldrich, 2009). This system is composed of a primary energy mover (in this case, a gas-fired turbine) with its corresponding generator. The exhaust * Corresponding author. Tel.: þ34 972418400; fax: þ34 972418399. E-mail address: angels.pelach@udg.edu (M.À. Pèlach). Contents lists available at ScienceDirect Journal of Cleaner Production journal homepage: www.elsevier.com/locate/jclepro 0959-6526/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jclepro.2011.02.014 Journal of Cleaner Production 19 (2011) 1072e1079