Biogas potential of OFMSW through an indirect method

The usual tests for measuring the anaerobic biogas potential (ABP) of the Organic Fraction of Municipal Solid Waste (OFMSW) are reliable, but are not practicable as a routine analysis. These types of analysis are expensive and time-consuming, requiring 21 (partial biogas production) to 100 days (total biogas production). Moreover, the operators of anaerobic digestion plants have often to choose which biomasses to use, depending on their digestibility and economical convenience. These matrices delivered daily to the plants, are heterogeneous especially with regard to the content of the biodegradable fraction, responsible for the potential production of biogas. In such a context, rapid methods for assessing potential biogas productions are needed for helping operators in their choices. In order to contribute to face these problems, in this work the Dynamic Respiration Index (DRI) was used to predict the anaerobic biogas potential. In this way is possible to know the ABP value in a short period of time (1–4 days). Two dynamic respirometric approaches were considered: the main difference between them is the temperature control (kept steady in one case, uncontrolled in the other one). In particular, DRI24 is determinated as the average integral over a period of 24 hours during the peak of maximum consumption in terms of oxygen. DRI24 is less affected by any oxygen consumption peak of limited duration. For these reasons it was recommended to use its value to determinate the Potential Production of Biogas. A literature equation which determines the ABP from the value of DRI was modified in order to take advantage of the characteristics of the respirometric method with controlled temperature. About 130 Nm3/t of food waste was assessed for the studied area, thanks to this method. In this way it was demonstrated that the plant operators can adopt a quick method to characterise the biogas potential of the OFMSW arriving daily at their plant, like a routine analysis.