A literature-based comparison of embodied GHG emissions of forced main sewer additives with potential reductions in methane generation

Abstract

Abstract Fugitive emissions of methane (CH4) from force main sewers are of increasing concern. Dosing of additives into force main sewers could be employed to mitigate methane emissions. However, all additives will have embodied greenhouse gas (GHG) emissions. This study examined commonly employed additives in terms of modes of action and potential to mitigate methane generation. Typical dosing strategies reported in the literature for each chemical were compiled and their embodied GHG emissions were summarised from sources in the literature. The net emissions considering mitigated methane generation and embodied GHG emissions were calculated on the basis of typical usage reported in the literature. The results revealed that biofilm shocking strategies and addition of iron have the greatest net reduction in GHG emissions. There is, however, uncertainty associated with the mechanisms by which iron reduces CH4 generation in force mains. Furthermore, future changes in the sourcing of iron may increase its embodied emissions. A qualitative assessment of the impacts of additive use on downstream GHG emissions revealed that they are highly case specific.