Enhanced biomethane production associated with olivine-stimulated CO2 reduction in petroleum reservoir production water.

Biomethanation, in which microbes convert CO2 into biomethane (bCH4), is a promising strategy for simultaneously recovering bioenergy and managing carbon. Electron donors are critical regulators of microbial CO2 reduction. However, a knowledge gap exists regarding both olivine as an electron donor in petroleum production water and its comparison with other mineral-based electron donors. Therefore, this study investigated the potential of natural olivine and iron ore to stimulate bCH4 production under laboratory-simulated petroleum reservoir conditions. Natural olivine-amended microcosms exhibited a high bCH4 production of 218.59 μmol/L·g of olivine, indicating a 49.04% increase compared to those amended with natural iron ore. The results also suggested that acetate and residual organic carbon present in the production water likely served as additional substrates for bCH4 production. Additionally, 16S rRNA gene sequencing revealed that the microbial communities responsible for bCH4 production were dominated by CO2-reducing methanogens closely related to Methanothermobacter and Methanobacterium. To the best of our knowledge, this study is the first attempt to unravel the use of natural olivine in this context, offering a novel strategy for CO2 reduction and bCH4 energy production.