Reference values of naturally occurring biogenic CO2 and CH4 fluxes from soils

This report presents a data analysis on natural emissions of carbon dioxide (CO2) and methane (CH4) from soils. These emissions are primarily linked to natural biological activity in the soils. This study was performed from selected field measurements data acquired by INERIS from numerous different sites and territories for over 20 years. On one hand, it confirms that there is no significant emission of CH4 from soils that are normally water drained and, on the other hand, that there is a generalized presence of a natural, largely measurable, CO2 flux on almost all-natural soils. The analysis furthermore demonstrates that the CO2 flux undergoes general and very pronounced seasonal variations that drive the other studied influence factors. The data set was statistically processed. This allowed us to establish the ranges of normal values, average values, low limits, high limits, and the most frequent values for specific configurations. This study resulted in reference data for natural emissions, which are useful to evaluate non-biogenic gaseous phenomena, such as post-mining gas emissions. These reference data can also be used outside of the mining and post-mining context, in areas with industrially polluted soils or to assess emissions from underground storage. Practical recommendations are proposed to lead to professional standards for in situ measurement of gaseous emissions from soils.