Carbon Clean raised $150 million in a Series C to continue development of its modular carbon capture system.

Carbon Clean has been praised by many, most recently by Chevron, which led the round, as well as by BNEF, which named it a BNEF Pioneer last month because of the startup's small-scale approach to carbon capture and sequestration.

The technology is large-scale. The world needs to eliminate emissions on a large scale, and the technology benefits from a certain amount of scale. That's the reasonCCS is usually attached to coal- or gas-fired power plants.

There are still many smaller sites that need to be decarbonized even though they are currently wedded to fossil fuels. These are the companies that Carbon Clean pitches itself to, and the startup says that its modular approach can help polluters deal with their carbon emissions in a gradual way.

Carbon Clean relies on a tried-and-true process to remove carbon dioxide from exhaust streams. Exhaust containing carbon dioxide is sent through a filter that is wetted with a solvent. Carbon dioxide will bind to the amine at a lower temperature. The solvent is pumped to another container, where it is heated to 120 degrees C to release the gas, which is then compressed and sent elsewhere to be used or stored. Each company has its own amine solvent with different properties, and the details of the process may vary, but that is what it is.

Carbon Clean's amine solvent can be used to reduce costs by requiring less energy to heat and by reducing the amount of water used in the system. It will be hard to judge such claims until the company releases more data. Carbon Clean is likely to see a small improvement in energy use based on the general type of amine it uses.