NETL: Carbon Storage - CO2 Utilization Focus Area

Processes or concepts must take into account the life cycle of the process to ensure that additional CO₂ is not produced beyond what is already being removed from or going into the atmosphere. Furthermore, while the utilization of CO₂ has some potential to reduce greenhouse gas emissions to the atmosphere, CO₂ has certain disadvantages as a chemical reactant. Carbon dioxide is rather inert and non-reactive. This inertness is the reason why CO₂ has broad industrial and technical applications. Each potential use of CO₂ has an energy requirement that needs to be determined; and the CO₂ produced to create the energy for the specific utilization process must not exceed the CO₂ utilized.

The figure below illustrates most of the current and potential uses of CO₂. However, many of these uses are small scale and typically emit the CO₂ to the atmosphere after use, resulting in no reduction in overall CO₂ emissions. Some of the more significant current and potential uses of CO₂ are highlighted in the research underway in this focus area.

In general, the area of CO₂ utilization for carbon storage is relatively new and less well-known compared to other storage approaches, such as geologic storage. Thus, more exploratory technological investigations are needed to discover new applications and new reactions. Many challenges exist for achieving successful CO₂ utilization, including the development of technologies capable of economically fixing CO₂ in stable products for indirect storage.

	Description
	Instead of the traditional energy intensive steam curing technology, develop a concrete curing process that consumes substantial amounts of waste CO₂ from onsite flue gases and local combustion sources. The produced concrete products should exhibit material performance equal to that of the traditional curing process, while using less energy. This use of CO₂ should sequester the carbon for many years. The transition between demonstration and commercial scale should be rapid, since the new process and technology is anticipated to require limited modification to the existing curing process.
	Research Focus
	Improve curing rates and CO₂ yield to increase efficiency of CO₂ use. Develop curing processes based on carbonation chemistry rather than hydration chemistry to reduce energy requirements and CO₂ emissions. Develop cement to meet American Standard Test Method (ASTM) standards.
	Collapse Text

	Description
	Traditional monomers, such as ethylene and propylene, can be combined with CO₂ to produce polycarbonates, such as polyethylene carbonate and polypropylene carbonate. The advantage of this process is that it copolymerizes CO₂ directly with other monomers without having to first convert the CO₂ to carbon monoxide (CO) or some other reactive species. This significantly reduces energy requirements. There are many potential uses for polycarbonate plastics, including coatings, plastic bags, and laminates. Depending on the final fate of the plastic, such as a landfill, this use could represent semi-permanent storage of carbon. This promising CO₂ utilization technology needs to be proven at pilot scale.
	Research Focus
	Utilize waste energy or alternative energy sources to convert CO₂. Develop catalysts to reduce energy requirements. Develop stabilizers to inhibit degradation of plastics.
	Collapse Text

	Description
	Carbonate mineralization refers to the conversion of CO₂ to solid inorganic carbonates. Naturally occurring alkaline and alkaline-earth oxides react chemically with CO₂ to produce minerals, such as calcium carbonate (CaCO₃) and magnesium carbonate (MgCO₃). These minerals are highly stable and can be used in construction or disposed of without concern that the CO₂ they contain will release into the atmosphere. One problem is that these reactions tend to be slow, and unless the reactions are carried out in situ, there is a large volume of rock to move. Carbonates can also be used as filler materials in paper and plastic products.
	Research Focus
	Reduce energy requirements for grinding feedstock materials needed for the mineralization process. Utilize waste streams to obtain oxides from existing mining operations. Develop chemicals or catalysts to speed reaction rates and reduce thermal and pressure requirements. Meet industrial standards for building materials.
	Collapse Text

	Description
	Enhanced Recovery (ER) involves the injection of CO₂ into a depleted oil or gas bearing field to increase production. This could involve injecting CO₂ into clastic, carbonate, coal, or organic shale formations.
	Research Focus
	Maximize the amount of CO₂ that could be stored as well as maximize hydrocarbon production as part of these ER operations.
	Collapse Text

Each technology approach has a specific application, advantages over others, and challenges that are the focus of the existing and future research. Information on active CO₂ utilization projects receiving DOE funds that aim to obtain these goals for the Carbon Storage Program is provided in the following table.