A novel comprehensive procedure for estimating greenhouse gas emissions from water resource recovery facilities

The emissions of the major greenhouse gases (GHGs), i.e. carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) from water resource recovery facilities (WRRFs) are of increasing concern in the water industry. In order to produce useful and comparable information for monitoring, assessing, and reporting GHG emissions from WRRFs, there is a need for a generally accepted methodology for their quantification. This paper aims at proposing the first protocol for monitoring and accounting for GHG emissions from WRRFs, taking into account both direct and indirect internal emissions and focusing the attention on plant sections known to be primarily responsible for GHG emissions (i.e. oxidation tanks and sludge digestors). The main novelties of the proposed protocol are: (i) measurement of direct internal emissions ascribed to aeration devices; (ii) estimation of indirect internal emissions derived from field measurement; (iii) GHG emission offset due to biogas energy recovery quantified by monitoring biogas composition in case of anaerobic digestion. Finally, the proposed methodology enables and allows the gathering of useful information on plants (e.g. energetic efficiency of the aeration device system and composition of biogas produced in anaerobic digestion) to address potential strategies for improving the plants’ performance.