Waste gases are an increasing concern for their impact on the environment. This includes carbon dioxide (CO₂) produced from industry and transportation, and methane from distributed oil wells and shale gas formations. Generally, these gases are released to the environment, or CH₄ is burned to CO₂, as CH4 is a more harmful greenhouse gas than CO₂. Researchers are increasingly interested in methods to fix these two gases into valuable fuels and chemicals so as to achieve a sustainable economy. However, any such technology must be economically viable to ensure widespread adoption in the regions that these gases are released. Yet biological gas fixation has many limitations that currently prevent practical implementation. This includes biological limitations such as slow growth rates, and low biomass and product titers. Process limitations are also a concern, as full conversion is desirable and gas mass transfer can be a substantial rate limiting step.