Alternative Fuels, Carbon, Research

Science Says “Go!” at the Red Trail Energy Ethanol Plant

Thursday, February 4, 2021

RICHARDTON, N.D.—Science says “Go!” on a carbon capture and storage (CCS) project in Richardton. CCS addresses environmental concerns and strengthens the local economy by reducing carbon dioxide emissions which also increases the value of the ethanol. Red Trail Energy, LLC (RTE) and its research partner, the Energy & Environmental Research Center (EERC), investigated every aspect of the permanent geologic storage potential deep below the plant, the cost of CO2 capture, and the likelihood that low-carbon fuel (LCF) markets and regulations would line up to make North Dakota’s first-ever commercial CCS project safe and cost-effective.

The positive outcomes bring the implementation of a commercial-scale CCS system at the RTE facility one giant leap forward. Generating an ethanol fuel applicable for LCF programs will provide a long-term premium market for RTE, providing stability for employees and local corn growers. The results also provide a path forward for other North Dakota renewable energy or biofuel producers in the region to add value to their products with LCF programs, such as California and Oregon.

Years of research went into that conclusion. The thorough analysis of geology more than a mile underground required innovative sleuthing and a variety of techniques. In addition to gathering existing drilling data, RTE drilled two holes more than 6400 feet deep to collect geologic data, rock, and fluid samples. Over 950 ft of rock as well as fluid samples were collected and analyzed by researchers to develop a model of the subsurface and evaluate its ability to accept and contain CO2 captured from RTE’s ethanol processing. EERC researchers also used a geophysical survey to project sound waves from the surface into the subsurface and analyze the reflected signal.

Drilling exploratory holes allows researchers to collect rock samples deep below ground, cutting core that arrives at the surface encased in long metal sleeves. The sleeves are measured, labeled, and cut to 3-foot lengths for shipment to the lab.

The myriad analyses fed the creation of computer models of the subsurface in the RTE study area. Improved and refined with each new set of data, these models provided a geologic template for CO2 injection simulations to predict CO2 movement during storage. The target storage layer below the RTE plant is called the Broom Creek Formation. It is a thick, porous sandstone layer pressed between thick layers of tightly sealed shale. EERC researchers used the model to predict the effects of CO2 injection on those geologic seals, including safe injection pressures for maintaining those confining layers. They evaluated the entire geologic structure of the area around Richardton, looking for faults, fractures, seismic activity, and potential mineral resource zones. In the end, the results show that the Broom Creek and its shale seals do indeed have the ability to safely and permanently store the nearly 200,000 tons of CO2 to be captured and injected annually by RTE through decades of operation. The results of these efforts are needed to prepare the required North Dakota permit application for commercial CO2 injection and storage, called a CO2 storage facility permit.

A rock core cut from the target CO2 storage layer 6400 feet below ground shows the pink sandstone of the Broom Creek Formation. It has the consistency of playground sand.

The immediate economic driver is the LCF markets in states like California which are looking for ways to reduce the carbon footprint of transportation fueled by the internal combustion engine. The RTE CCS team has been working with West Coast regulators to ensure that the delivered ethanol will meet the requirements of California’s Low Carbon Fuel Standard, a program that includes monitoring to ensure that the CO2 stays permanently trapped in its storage layer. Other states with LCF programs are expected to adopt those standards in the future. Ensuring a market share is critical to survival in the shifting energy market.

In addition to economics, technology is a major limiting factor in the rate at which innovative concepts become reality. Are the materials, processes, and technologies needed to carry out CCS on an ethanol plant available? Separating and capturing CO2 from ethanol-fermentation gases have become established processes in the last 10 years and require site-specific engineering and not-quite off-the-shelf equipment. The compression, transport, and injection of CO2 have been effectively developed over 40 years of enhanced oil recovery (EOR). The novel technological challenge for dedicated CO2 storage (a challenge not faced by EOR) is proving that it stays put—and doing so affordably and thus sustainably. Innovations by researchers and private companies continue to expand the toolbox and bring down the cost of monitoring CO2 deep underground.

The RTE CCS project work included creating a monitoring plan that accounted for technical, economic, and regulatory components. For example, elements of the plan are focused on tracking CO2 during injection and in the storage zone using real-time pressure and temperature data, as well as repeating monitoring well testing and geophysical surveys at specified intervals. Other elements include monitoring groundwater and soil gas as assurance of environmental protection.

North Dakota legislators and regulators recognized the potential for CCS to play a critical role in the state’s energy production and made key decisions to regulate geologic storage projects within the state. In April 2018, the U.S. Environmental Protection Agency formally recognized the framework and procedures established by the ND Department of Mineral Resources (DMR) by granting the DMR’s application for Class VI primacy. Class VI refers to the EPA well classification established to regulate wells dedicated to permanent CO2 storage. North Dakota’s proactive request for primacy from EPA maintains the safe implementation established by federal regulations, facilitates communication, and incorporates local geology expertise.

Once the permits are approved, the exploratory hole drilled in spring 2020 will be converted into the CO2 injection well. The second test site, drilled in October, will be converted into a monitoring well for the CCS project.

The next steps, as laid out in DMR regulations, require the submission of a complete North Dakota carbon storage permit application. All of the research results must be compiled into a five-part package of evidence making the case for safe, permanent geologic storage beneath the RTE ethanol plant.

The DMR, in consultation with the ND Department of Environmental Quality, will evaluate the permit application to determine whether approval should be granted. This first-time regulatory process is estimated to take 8–12 months and includes a public comment period and hearing. Approval would bring RTE one step closer to becoming the first facility in North Dakota to commercially capture and permanently store CO2.

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