Annual CO2 and CH4 fluxes of pristine boreal mires as a background for the lifecycle analyses of peat energy

This study was conducted to improve the estimates of C gas fluxes in boreal ombrotrophic and minerotrophic mires used in the lifecycle analysis of peat energy. We reviewed literature and collected field data from two new sites in southern Finland. In the literature, annual estimates of net CO 2 exchange varied from -85 to +67 g C m -2 a -1 for ombrotrophic mires and from -101 to +98 g C m -2 a -1 for minerotrophic mires. Correspondingly, net CH 4 flux estimates varied from less than -1 up to -16 g C m -2 a -1 and from less than -1 up to -42 g C m -2 a -1 for ombrotrophic and minerotrophic mires, respectively. Negative values indicate net efflux from the ecosystem. The modelling of C gas fluxes for the 30 simulated years clearly highlighted the need for long-term records of multiple environmental factors from the same sites, and the need for a number of improvements in the modelling of fluxes, as well as the environmental conditions driving C fluxes. The reduction of uncertainty in the background values of lifecycle analyses requires more detailed knowledge of the mire types used for peat harvesting and long-term field measurements combined with the developed process models and meteorological information. The use of C gas fluxes in pristine mires as a background for anthropogenic emissions is, however, only one option. Another option could be to consider anthropogenic emissions from the use of peat energy as such.