Method for determination of methane potentials of solid organic waste Trine L. Hansen a , Jens Ejbye Schmidt a , Irini Angelidaki a , Emilia Marca a , Jes la Cour Jansen b , Hans Mosbæk a , Thomas H. Christensen a, * a Environment & Resources DTU, Technical University of Denmark, Kongens Lyngby, Denmark b Department of Water and Environmental Technology, Lund Institute of Technology, University of Lund, Lund, Sweden Accepted 24 September 2003 Abstract A laboratory procedure is described for measuring methane potentials of organic solid waste. Triplicate reactors with 10 grams of volatile solids were incubated at 55  C with 400 ml of inoculum from a thermophilic biogas plant and the methane production was followed over a 50-day period by regular measurements of methane on a gas chromatograph. The procedure involves blanks as well as cellulose controls. Methane potentials have been measured for source-separated organic household waste and for individual waste materials. The procedure has been evaluated regarding practicality, workload, detection limit, repeatability and reproduci- bility as well as quality control procedures. For the source-separated organic household waste a methane potential of 495 ml CH 4 /g VS was found. For fat and oil a lag-phase of several days was seen. The protein sample was clearly inhibited and the maximal methane potential was therefore not achieved. For paper bags, starch and glucose 63, 84 and 94% of the theoretical methane potential was achieved respectively. A detection limit of 72.5 ml CH 4 /g VS was calculated from the results. This is acceptable, since the methane potential of the tested waste materials was in the range of 200–500 ml CH 4 /g VS. The determination of methane potentials is a biological method subject to relatively large variation due to the use of non-standardized inoculum and waste heterogeneity. Therefore, procedures for addressing repeatability and reproducibility are suggested. # 2003 Elsevier Ltd. All rights reserved. Keywords: Methane; Biogas; Organic waste; Characterization; Laboratory measurement 1. Introduction Several batch methods exist for measuring methane potentials of waste. The basic approach is to incubate a small amount of the waste with an anaerobic inoculum and measure the methane generation, usually by simul- taneous measurements of gas volume and gas composi- tion. However, the technical approaches in terms of pretreatment of the sample, inoculum, gas measurement technique and incubation vary significantly among the published methods (Adani et al., 2001; Eleazer et al., 1997; Harries et al., 2001; Heerenklage and Stegmann, 2001; Owen et al., 1979; Owens et al., 1993). Some of these differences originate from the purpose of measuring the methane potential and from the type of waste samples measured. Most of the methods are geared to either very homogenous samples, such as sewage sludge, or to samples with low methane potentials, such as waste from old landfills or biologically pretreated waste. We have adapted and modified existing procedures, in particular inspired by Angelidaki and Ahring (1997), to an easy-to-operate method of determining methane potentials of solid waste samples generating high amounts of methane. Here, the procedure and the experiences obtained from measuring methane poten- tials of more than 100 waste samples during a 2-year period are described. The method was used to characterize organic waste, separated from household waste, regarding methane potential as relevant in the context of treatment by anaerobic digestion. The main goal was to determine the methane potential in terms of STP (STP: standard 0956-053X/$ - see front matter # 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.wasman.2003.09.009 Waste Management 24 (2004) 393–400 www.elsevier.com/locate/wasman * Corresponding author. Tel.: +45-4525-1603; fax: +45-4593- 2850. E-mail address: thc@er.dtu.dk (T.H. Christensen).