Cross-species comparison of ultramafic rock bio-accelerated weathering performance

Carbon mineralization sequesters atmospheric CO₂ by reacting it with cations from rock weathering to form carbonates. However, natural rates are too slow, and acceleration with chemical or mechanical methods is expensive. Microbial processes (acidolysis, redoxolysis, complexolysis) could speed weathering with less energy. However, no microorganisms have been employed at industrial scale to dissolve ultramafic rocks. Although some microbes dissolve ultramafic rocks), their performance remains poorly understood. Here, we compare the dissolution of dunite (> 90% olivine) by three mineral-dissolving microbes: Gluconobacter oxydansSphingomonas desiccabilis and Penicillium simplicissimum. G. oxydans outperformed the others, producing the most acidic biolixiviant (pH 2.15 at 1% pulp density) and extracting the most magnesium (3,130 mg/L at 3% pulp density). It also co-dissolved nine metals, including eight critical for energy technologies (Cr, Mn, Co, Ni, Cu, Zn) reaching up to 33 mg/L Ni. Increasing pulp density boosted metal dissolution by G. oxydans and S. desiccabilis but inhibited P. simplicissimum above 2% pulp density. These results show G. oxydans is best suited for engineering to enhance bio-accelerated weathering, reducing costs and environmental impacts. Finally, both G. oxydans and P. simplicissimum can use cellulosic hydrolysate instead of glucose, lowering substrate costs for biolixiviant production.