Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel Full Length Article Predicting Wobbe Index and methane number of a renewable natural gas by the measurement of simple physical properties Partho Sarothi Roy a , Christopher Ryu b , Chan Seung Park a, ⁎ a Bourns College of Engineering, University of California Riverside, Riverside, CA 92507, United States b Department of Computer Science, California State University Fullerton, Fullerton, CA 92834, United States GRAPHICAL ABSTRACT ARTICLE INFO Keywords: Renewable natural gas Variable natural gas vehicle Wobbe Index Methane number ABSTRACT This study describes a fuel quality prediction strategy that predicts the fuel quality parameter and component composition of Renewable Natural Gas (RNG) containing CH 4 ,C 2 H 6 and CO 2 . Onsite measurement of the gas properties in a renewable natural gas (RNG) fuel is necessary to ensure an expected level of quality, which must be maintained for better combustion efficiency. The Wobbe Index (WI) and methane number (MN) are the natural gas quality indicators used. To predict the WI, MN, and component composition, a data set that consists of WI, MN, thermal conductivity and sound velocity of the gaseous fuel mixture as a function of its temperature, pressure and composition, was created. Through a regression analysis of the data set, a model that estimates the WI, MN and composition of the gaseous fuel mixture from its physical properties (temperature, pressure, thermal conductivity and sound velocity), was developed. The results of the study including the data set and the pre- diction model that can accurately estimate the WI, MN, and gas composition, is presented in this paper. 1. Introduction Renewable Natural Gas (RNG), i.e., natural gas produced from re- newable feedstocks (e.g., landfill gas, anaerobic digestion gas, etc.) is an important alternative fuel that can aid in achieving goals set by the local and federal governments related to fossil fuel replacement and greenhouse gas (GHG) emissions reduction. Most RNG production projects are small to medium scale by nature, and comprehensive gas cleanup/upgrading to meet the fuel specifications of pipeline natural gas is often not feasible from an economical perspective. This results in most RNG resources being wasted (e.g., flaring) or being left unused. The RNG from landfills or anaerobic digestion comes with a sig- nificant amount of CO 2 : the CH 4 concentration varies from 50 to 70% whereas CO 2 composition varies from 25 to 45% [1,2]. Upgrading RNG to the quality of a pipeline natural gas requires removal of CO 2 from the biogas as well as purification, drying, and compression. Among these https://doi.org/10.1016/j.fuel.2018.03.074 Received 15 December 2017; Received in revised form 10 March 2018; Accepted 12 March 2018 ⁎ Corresponding author. E-mail address: cspark@cert.ucr.edu (C.S. Park). Fuel 224 (2018) 121–127 0016-2361/ © 2018 Elsevier Ltd. All rights reserved. T