Integrated System for Electromicrobial Production of Butanol from Air-Captured CO2

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OPEN 2021
Berkeley, California
Project Term:
04/22/2022 - 04/21/2024

Critical Need:

The use of fossil fuels in transportation accounts for 29% of U.S. greenhouse gas emissions and contributes significantly to the ongoing climate crisis. There is a need for carbon-neutral drop-in substitutes for fossil fuels to substantially reduce the carbon footprint of the nation’s transportation sector without requiring significant changes to its infrastructure. The U.S. consumes more than ~130 billion gallons of transportation fuel per year, and despite anticipated reductions in gasoline use resulting from electric vehicle adoptions, demand for liquid fuels for heavy-duty, marine, and aviation transportation is expected to rise, so successful carbon-neutral, scalable, and economically competitive replacement fuels must be produced.

Project Innovation + Advantages:

The University of California, Berkeley (UC Berkeley) team will jointly develop an integrated process to produce butanol directly from air-captured carbon dioxide (CO2). Butanol has a higher energy density than ethanol and is a precursor to jet fuel. UC Berkeley’s system takes three main inputs: ambient air, water, and a sustainable energy source, and produces butanol. The steps to produce butanol are : (1) capturing CO2 directly from the air by a solid adsorbent, (2) using a chemoautotrophic microorganism to biologically fix the captured CO2 into acetate, and (3) using acetate as a feedstock for the heterotrophic production of butanol via metabolically engineered bacteria. (Chemoautotrophs are organisms that consume CO2 and a chemical source of energy; heterotrophs are organisms that cannot utilize CO2 and instead metabolize organic compounds for nutrition.) Preliminary models indicate that butanol production from the proposed process will be more sustainable than traditional butanol fermentation.

Potential Impact:

UC Berkeley’s proposed process will result in a ground-breaking carbon capture system coupled with electromicrobial production of a renewable biofuel and precursor to jet fuel.


The process will enable a technical roadmap to sustainable biofuels and value-added chemical products.


The proposed process is projected to have substantially lower GHG emissions compared with traditional corn-derived biofuels.


Preliminary analysis suggests that the proposed process can produce butanol at $6.60 per gallon of gasoline equivalent by 2030, with further room for cost reductions. This cost is within 50% of the current cost of corn-based biofuel ($4.50/gal gasoline equivalent including U.S. corn subsidies) with substantially less land use.


ARPA-E Program Director:
Dr. James Seaba
Project Contact:
Prof. Douglas Clark
Press and General Inquiries Email:
Project Contact Email:


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