Natural Gas - CO₂ removed from natural gas is often treated as a waste gas and simply vented to the atmosphere. If the waste gas contains significant amounts of hydrocarbons or other impurities, it must usually be treated in a flare or thermal oxidizer before being vented further adding to the operating cost of the natural gas treatment. This is a particular concern for small-scale natural gas treatment systems using membranes or pressure swing adsorption (PSA) for CO₂ removal.

Biogas – Biogas is a renewable energy source produced from the anaerobic digestion of organic waste streams. Raw biogas is a mixture of primarily methane (CH₄) and CO₂, but it also contains a host of other impurities, including hydrogen sulfide (H₂S), siloxanes, nitrogen, and water vapor. These impurities can be corrosive to equipment, reduce the energy value of the gas, and in the case of H₂S, are highly toxic. The process of “upgrading” or “purifying” biogas involves removing these contaminants to increase the methane concentration and produce high-quality biomethane (which can be used as vehicle fuel, can be injected into natural gas pipelines, or used to generate electricity).

Wastewater – The removal of dissolved CO₂ from wastewater improves the efficiency of downstream processes and offers a potential avenue for carbon capture. The presence of CO₂ in water, often from biological processes or natural sources, can lower the pH, making the water more acidic and potentially corrosive to pipes and equipment. Processes like “decarbonation” or “degasification” use techniques such as air stripping or membrane contractors to transfer the dissolved CO₂ from the liquid phase to a gas phase. This not only helps to adjust the pH for subsequent treatment steps, such as in reverse osmosis or deionization, but also provides a concentrated stream of CO₂ that can be utilized. Other processes cause the captured CO₂ to react with alkaline materials in the wastewater, forming stable carbonate minerals. This effectively sequesters the carbon while simultaneously creating a valuable product and improving water quality.

Ethanol and Ammonia Production – The fermentation process in ethanol plants and the chemical reactions in ammonia manufacturing produce a significant amount of CO₂ as a byproduct. This CO₂ is relatively easy to capture and purify for reuse.

Industrial Flue Gases – Waste streams from industrial facilities, such as those in the steel and cement industries or from power plants have several impurities and require intensive purification. However, advanced technologies and SulfaTrap sorbents make this a viable option. This “point-source” carbon capture can turn what would otherwise be a major emitter into a source of recycled CO₂.

SulfaTrap’s proprietary sorbents are designed to remove a wide range of impurities from gas and liquid streams. Our solutions are applied in various industries including natural gas, biogas, petrochemicals and the production of food-grade CO₂.

Sulfur Compounds:

• Hydrogen Sulfide (H₂S): A common and highly corrosive impurity in many gas streams.

Organic Sulfur Compounds:

• Mercaptans (e.g., methyl mercaptan, ethyl mercaptan, tert-butyl mercaptan)
• Sulfides (e.g., dimethyl sulfide, disulfides, trisulfides)
• Thiophenes (e.g., tetrahydrothiophene)
• Carbonyl Sulfide (COS)
• Carbon Disulfide (CS₂)

Other Impurities:

• Metals including mercury and arsenic
• Halides such as chlorides
• Siloxanes such as those man-made organic compounds found in biogas and other streams
• Volatile Organic Compounds (VOCs)
• Heavy Hydrocarbons (particularly relevant for controlling the hydrocarbon dew point in gas streams)
• Nitrogen (N₂) can be selectively rejected from natural gas and biogas

Global market for food-grade carbon dioxide (CO₂) is very large (multi-billion dollar). The market for food-grade CO₂ in the USA, is robust and continues to grow, driven primarily by the high demand from the US food and beverage industry. The North American share of the global food-grade CO₂ market was approximately 39% in 2024 due to this high demand. CO₂ is a critical ingredient for carbonation in a wide range of products, including soft drinks, sparkling waters, and beer. Beyond beverages, food-grade CO₂ is essential for cryogenic freezing, chilling, and modified atmosphere packaging (MAP), which extends the shelf life of perishable goods like meat, poultry, and baked goods. While the market is experiencing growth, it is also sensitive to supply chain vulnerabilities, as seen in past shortages. This has led to an increased focus on alternative sourcing and on-site CO₂ recovery technologies by some companies to ensure a stable supply and mitigate price volatility.

The market for CO₂ is segmented by purity grade, as different applications require varying levels of cleanliness and freedom from impurities. The purer the gas, the more specialized and often more expensive it is.

Industrial Grade CO₂ is the most common and the least pure form of CO₂. Typically, industrial grade CO₂ has a purity level of around 99%. it is used in a wide range of applications where a high level of purity isn’t critical such as, welding, fire suppression systems, food production and as a feedstock for various chemical processes.

Food-grade CO₂ is used in the food and beverage industry and is regulated by agencies like the FDA. The purity required is 99.9% and higher, with strict limits on specific impurities that could affect the taste, aroma, or safety of food and drinks. This market is particularly important for carbonated beverages, cryogenic freezing, and modified atmosphere packaging.

Medical-grade CO₂ is held to an even stricter standard, with a minimum purity of 99.999% and, crucially specific controls on impurities to ensure it is safe for medical applications. It is used in surgeries as an insufflation gas to inflate body cavities for better visibility and in other medical procedures.

Research, Laser and Semiconductors also require ultra-pure CO₂ for sensitive applications. These can reach purities of 99.999% or higher. These markets include laboratory research, specialized laser applications, and the electronics and semiconductor industry, where even trace impurities can damage delicate components.

The removal of CO₂ from gas streams is a critical process for various industries, including energy production, natural gas processing and chemical manufacturing. The choice of process depends on factors such as the CO₂ concentration in the gas stream, the desired purity, and the overall economics.

Chemical Absorption (Amine Scrubbing) is one of the most widely used and mature technologies. Amine scrubbing is often used in post-combustion capture from power plants and industrial facilities. The gas stream is passed through a solvent, typically an amine solution (such as monoethanolamine, MEA), which chemically reacts with and absorbs the CO₂. The CO₂-rich solvent is then heated in a separate vessel to release the CO₂ in a concentrated, high-purity stream, allowing the solvent to be recycled.

Physical Absorption is suitable for gas streams with a high concentration of CO₂ and high pressure, such as in pre-combustion capture in integrated gasification combined cycle (IGCC) power plants or natural gas processing. Physical solvents like Selexol or Rectisol do not chemically react with the CO₂ but instead dissolve it under high pressure. The CO₂ is then released by simply reducing the pressure, which is often more energy-efficient than the heating required for chemical absorption.

Adsorption (Solid Sorbents) use a solid material called a sorbent. The sorbent captures CO₂ molecules on its surface. Sorbents can be regenerated by changing the temperature (temperature swing adsorption, TSA) or pressure (pressure swing adsorption, PSA). This process is gaining traction for its potential to be more energy-efficient and for use in specific applications like direct air capture (DAC), where CO₂ is removed directly from the atmosphere.

Membrane Separation technologies use a semi-permeable membrane that selectively allows CO₂ to pass through while blocking other gases. This process is driven by a pressure difference across the membrane. It is a modular and compact technology, making it suitable for smaller-scale applications or for integration into existing processes. However, challenges remain in developing membranes with both high selectivity and high flux (flow rate).

Cryogenic Distillation is a process that involves cooling the gas stream to very low temperatures to liquefy the CO₂ (the CO₂ has a higher boiling point than other components like nitrogen and methane). The liquified CO₂ can then be separated by distillation. While this process is highly effective at producing high-purity CO₂ (often food-grade), this method is very energy-intensive and is typically only used for gas streams with a high initial concentration of CO₂.

Oxy-fuel Combustion is an alternative approach to capture, where the fuel is burned in a pure oxygen environment instead of air. This process a flue gas consisting primarily of CO₂ and water vapor. The water vapor is easily condensed, leaving a highly concentrated stream of CO₂ that is ready for transport and storage. The main challenge with this method is the high cost and energy required to produce the pure oxygen.