First experimental comparison of calorific value measurements of real biogas with reference and field calorimeters subjected to different standard methods

Abstract This study presents the first comparison of experimental calorific value measurements of real biogas performed with three different calorimeters: one reference gas calorimeter developed at the French metrology institute (LNE) and two field calorimeters (Union Instruments CWD, 2005 CT and Cutler Hammer Calorimeter) at the German metrology institute (PTB). All measurement results obtained for calorific values agree within their measurement uncertainties. Uncertainties vary from 0.2% to 2.0% (coverage factor, k  = 2) depending on the calorimeter and calibration procedure. Two different standards (DIN 51899 and ISO 6143) were used to calibrate the field calorimeters and these have been compared. This comparison focuses on the calibration procedure, calibration frequency, number and composition of calibration gases and evaluation algorithm.