Abstract This study aims to assess methane (CH4) and carbon dioxide (CO2) concentrations in the ventilation systems of two coal mines (A and B) in the Santa Catarina coal deposit in southern Brazil (Paraná Basin, Bonito Formation), and estimate their greenhouse gas (GHG) emissions. The highest CH4 levels (1.8%) were recorded in strong methane emanation areas in mine A, below the lower explosive limit (5%). The IPCC-recommended methods significantly overestimated the methane emission (up to 80%) when compared to the experimental data measured for each mine. Application of an alternative method made it possible to estimate direct CO2 emissions, indicating that CO2 accounted for 22 to 77% of total GHG emissions. Carbon dioxide emissions are generally not included in GHG emission inventories, indicating that the coal industry underestimates the contribution of this gas. As such, it is recommended that the methodology used for these calculations be revised and that specific emission factors be applied for each mine. In order to improve the accuracy of inventories, more sampling needs to be carried out in all operational and abandoned mines.

The objectives of this study were twofold: to assess two chromatographic methods for the analysis of greenhouse gases (GHG) and carbon monoxide, and to propose and evaluate a low-cost and reusable alternative system for their sampling and storage, using 10 different container configurations (flasks and bags). To that end, standard samples containing the gases of interest (CO2, CH4 and CO) and different types of real samples were tested. Finally, procedures for the sampling, storage and analysis of CO2 and CH4 were evaluated and optimized. Two chromatographic methods were applied, using different analysis conditions and columns. Gas chromatography analysis of sample stability and container reusability demonstrated that borosilicate flasks with butyl rubber and PTFE/silicone septa are ideal for storing samples, allowing up to 5 successive sampling cycles with no significant loss of recovery. For larger volume samples, multilayer foil bags are the most stable for the compounds analyzed. The tests conducted with real and synthetic gas samples under optimized chromatography conditions using both methods indicated satisfactory performance for CO2 and CH4 quantification. However, CO analysis in the column with a polystyrene-divinylbenzene stationary phase (Method 1) produced an artifact due to the presence of oxygen in the samples, restricting its quantification.