Meeting the Challenge: The Center for Carbon Capture and Conversion Takes A Proactive Approach
By Trina Igelsrud Pfeiffer, School of Energy Resources – University of Wyoming
Since its inception in July 2016, the Carbon Engineering Initiative Program under the Center for Carbon Capture and Conversion (CCCC) at the University of Wyoming School of Energy Resources has focused on defining the feasibility of manufacturing value-added high-carbon content products from Wyoming Powder River Basin (PRB) coal. These value-added products will command price premiums beyond simple energy content value. In the past seven years, CCCC researchers working in this area have developed a two-step upstream process: Solvent Extraction and Fast Pyrolysis that produces coal extract materials and coal char. Using materials from this upstream process, downstream products are being made into economically attractive coal products that are superior to current market products.
The current focus is to identify and produce coal products that consume large quantities of coal. These products are in the areas of asphalt binder for roads and roofing materials, building materials (bricks, foam, drywall, pavers, aggregate for roads and other products), soil amendment, reclamation and graphene oxide.
One of the products identified early on is coal-derived asphalt binder. The extract, from the Solvent Extraction process, is used to make coal-derived asphalt binder. The concept was originally developed at a lab scale and is currently at the pilot scale. Western Research Institute is working with CCCC and focusing on the chemistry, characteristics and blending of the coal extract being made for asphalt products. The Solvent Extraction Team within CCCC is working on the scale-up and design of a commercial plant. Both groups are working together to develop a product that can be processed in an economical and environmentally friendly way.
The coal-derived asphalt products have a lower carbon footprint than their petroleum-based counterpart. Petroleum-derived asphalt products produce 376 kg CO2e/ton of asphalt while coal-derived asphalt products produce 73kg CO2e/ton of coal-derived asphalt. This drastic difference could aid the petroleum-based asphalt companies meet the new standards of lower CO2 emissions by blending some of the coal-derived asphalt products into their product. Side-by-side testing of a mixed product (petroleum-based mixed with coal-based asphalt binder), a pure coal asphalt product and a pure petroleum-based product will be conducted in the future to compare how each formulation performs during a multi-year cycle.
The coal-derived asphalt binder is also being used for roofing materials and initial testing shows great potential. Both paving and roofing industries need alternative products that can meet the challenges of environmental regulations. Coal-derived asphalt is a product that could contribute to the solution.
Bricks made with coal char (a product of coal pyrolysis) are a product that has great potential. By using coal char as the raw material, the resulting bricks have a Class A fire rating, which is extremely important in building materials. Compared with conventional clay bricks, coal char-derived bricks are less expensive to make, are at least as strong and are half the weight of a clay brick (which helps with transportation costs).
Two test houses, a standard clay brick house and a coal char brick house, were built side by side in the spring of 2022 in Laramie, Wyoming. Data has been gathered for over a year to compare the two structures. The results show the char brick house emits lower VOCs than the clay brick house. The char brick house is also cooler in the summer months than the clay brick house. The building materials team has developed a generation two brick which is more compact and has even better weathering properties. Generation two bricks will replace the generation one bricks on the char brick house in the spring of 2024, and there will be another year’s worth of comparative data gathered in the subsequent months.
The building materials team has also been working on block pavers, carbon insulating foam, construction grout and aggregate for road construction. The team is working actively on some additional new products as well, which are in the proof-of-concept phase. Another area of research by the building materials team is adding graphene oxide from coal to concrete. Adding a small amount (0.05%) of graphene oxide increases the concrete strength by over 20%.
The soil amendment product being developed has been shown to help with water retention in soil and aids in reducing nitrogen runoff. Field trials at the Powell and SARAC Research Centers in Wyoming are in their third year of data gathering, and the results will be analyzed in the fall of 2023.
In August, the soil amendment team worked with Peabody personnel to test the use of the coal-derived soil amendment for reclamation efforts at their North Antelope Rochelle Mine near Gillette, Wyoming. The soil amendment is also being mixed with Wyoming-based algae, which is expected to further enhance soil health. The algae consume CO2 to multiply and are expected to be used to aid in the cleanup efforts of the pyrolysis and solvent extraction of gases making a coal refinery that produces coal to products materials a net zero carbon emitting facility.
Life Cycle Analysis (LCA) and economic viability of the coal-based products are in progress. There have been many product ideas generated from work explored under the Carbon Engineering Initiative. Not all products will be pursued due to unique scale-up challenges which impact economic viability. The products discussed above have been shown to be economically viable. There are many other products that are currently making their way through the LCA and scale-up vetting process.
The commercialization of the coal refinery (pyrolysis and solvent extraction processes) is underway with a semi-works plant being built at the Wyoming Innovation Center in Gillette, Wyoming. Both the pyrolysis and solvent extraction processes were bench-scale that moved into pilot-scale over the past four years. Both pilot scale processes have been scaled up from gram scale to kilogram scale, and data collected from these pilot plants are being used to help engineer the semi-works plant in Gillette.
The engineering for the semi-works plant is underway, with the first phase being the site prep and utility tie-ins for both processes. The second phase, pyrolysis engineering, procurement and construction is also underway. The pyrolysis unit construction is expected to be completed by the fall of 2024. The third phase of the project is the solvent extraction unit. This unit will take about 18 months to complete. Engineering of the solvent extraction unit is expected to be done in the spring of 2024, with construction starting in the fall. The semi-works plant will make tons of material that can be used in large-scale projects, such as paving a section of road with the coal-derived asphalt product. Data gathered by running the semi-works plant will aid in the engineering of the commercial coal refinery plant. The plan for the commercial coal refinery is to consume two-unit trains of coal a day.
The efforts of the principal investigators dedicated to the work identified by the Carbon Engineering Initiative have led to the tremendous success of the coal-to-products work done at the University of Wyoming School of Energy Resources under CCCC. Continued research in this area is expected to yield more high-volume products that can be made from Powder River Basin coal. CCCC’s efforts on commercialization and scale-up of both main processes (solvent extraction and pyrolysis) and the downstream products have helped move the idea of a coal refinery from a conceptual idea to lab and pilot scale facilities with semiworks scale in process. The semi-works scale will generate information leading to a commercial scale coal refinery to produce valuable coal to products materials. Coal is a viable resource that can be used in several ways. CCCC’s Carbon Engineering Initiative work is just scratching the surface of the potential for this valuable carbon ore.