About This Project

The oceans are a sink for CO2. Rocks such as olivine could be dissolved into ocean water, which would increase the pH and precipitate bicarbonate with magnesium to irreversible withdraw CO2 from the atmosphere and ocean. The natural weathering of olivine takes >10,000 years. Rapid solubilization olivine could neutralize human-produced CO2 and reverse global warming. We propose to create an enzyme that will catalyze and accelerate the solubilization of olivine.

Ask the Scientists

What is the context of this research?

The oceans have capacity to store CO₂ as bicarbonate ions, with residence times >50,000 years_­­. Soils and oceans already uptake and store nearly half of anthropogenic CO₂ emitted each year. The capacity of the ocean to store CO₂ is governed by its alkalinity, which is generated by natural weathering of silicate minerals. Mineral weathering occurs on geologic time scales. Moreover, CO­₂ uptake has already acidified the oceans, which slows further sequestration and damages ecosystems. “Enhanced weathering” of silicate minerals would increase ocean buffering and accelerate CO₂ sequestration. Olivine is an abundant mineral that can theoretically sequester 1 Gt CO₂ per Gt dissolved olivine: Mg_1.8Fe_0.2SiO₄ + 4CO₂ + 4H₂O --> 1.8Mg²⁺ + 0.2Fe²⁺ + 4HCO₃^- + H₄SiO₄

What is the significance of this project?

Sequestration of 1000 Gt of anthropogenic CO₂ by 2100 (the goal to limit average temperature increase to <1.5 degrees) might be achieved by dissolution of <50 Gt olivine/year, (less than the throughput of the global construction industry, indicating we could move this much rock). The natural weathering rate of olivine is only ~5 µm/year. Processing of 500-5000 Gt of olivine/year would be needed, because its dissolution rate is so slow.

Microbes accelerate dissolution of silicate minerals. This effect occurs only during microbial growth, however, suggesting that the weathering rate would scale linearly with the number of cultivated microbial cells. Catalytic molecules or processes are needed to accelerate the weathering of >50 Gt olivine.

What are the goals of the project?

Aim 1: De novo design of candidate olivine-degrading enzymes

Aim 2: Evaluation of olivinase activity at lab scale

The ultimate goal is to develop an enzyme that will be part of a scaled-up system that will solubilize olivine, a very abundant mineral, and allow its component ions to capture human-generated CO2 in the ocean. To neutralize excess CO2 at the rate it is currently produced, we estimate that we need to increase olivine solubilization rates by about 10-fold relative to natural weathering.