Illinois Basin Decatur Project; soil carbon dioxide flux monitoring

The purpose of this report is to provide a summary of soil carbon dioxide flux measurements collected at the Illinois Basin - Decatur Project (IBDP). The IBDP is a geologic carbon storage project that successfully injected 1 million tonnes (1.1 million tons) of carbon dioxide (CO2) into t... Full description

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Authors:Carman, C.H.; Blakley, C.S.; Korose, C.P.; Locke, R.A., II
Source:Circular - Illinois State Geological Survey, No.599, 27p. Publisher: University of Illinois at Urbana-Champaign, Institute of Natural Resource Sustainability, Illinois State Geological Survey, Urbana, IL, United States. ISSN: 0073-506X
Publication Date:2019
Note:In English. 20 refs.
Subjects:ArcGIS; Carbon dioxide; Climate change; Fluid injection; Geographic information systems; Information systems; Mapping; Soils; Statistical analysis; Temperature; Underground installations; Underground storage; Illinois; Illinois Basin; Macon County Illinois; United States; Decatur Illinois; Flux; Illinois Basin Decatur Project
Coordinates:N393600 N400400 W0884500 W0891200
Record ID:2020016551
Copyright Information:GeoRef, Copyright 2020 American Geosciences Institute.
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The purpose of this report is to provide a summary of soil carbon dioxide flux measurements collected at the Illinois Basin - Decatur Project (IBDP). The IBDP is a geologic carbon storage project that successfully injected 1 million tonnes (1.1 million tons) of carbon dioxide (CO2) into the Mt. Simon Sandstone at an industrial site in Decatur, Illinois. Injection began on November 17, 2011, and concluded on November 26, 2014. The IBDP monitoring, verification, and accounting (MVA) program included a soil CO2 flux monitoring network that used the closed-chamber accumulation method to estimate fluxes in the study area on an approximately weekly basis from June 2009 to June 2015. The 109 discrete monitoring installations in the network were designed to examine the effects of vegetation removal and ring insertion depth (8 vs. 46 cm, or 3.1 vs. 18.1 in.) on the magnitude and variability of fluxes. The network consisted of three installation types: (1) bare-shallow, (2) natural-shallow, and (3) bare-deep. Bareshallow and bare-deep installations were inserted to 8 and 46 cm (3.1 and 18.1 in.), respectively, below the soil surface, and herbicide was applied around these two installation types to minimize the contribution of vegetation to soil CO2 fluxes. Natural-shallow installations were inserted to 8 cm (3.1 in.) below the soil surface, and vegetation was trimmed only when necessary to allow a flux measurement to be taken. Soil temperature and moisture data were collected simultaneously with flux measurements when possible to examine their relationship to fluxes. Soil temperatures were compared with local air temperatures measured at the Decatur airport, and when soil temperature data were not able to be collected, air temperatures were determined to be a satisfactory proxy. In total, 12,904 flux measurements were collected during the project. Nonparametric statistics were used to test fluxes measured at each location to evaluate whether CO2 injection activities had affected fluxes at the IBDP site. Overall, our statistical examination of the flux data indicated that soil CO2 fluxes at the IBDP site were not affected by CO2 injection. Soil CO2 fluxes varied with seasonal temperature cycles, as expected. Extremes in soil moisture affected the soil CO2 fluxes; for example, a drought in 2012 caused fluxes from April to July to be 37% lower than the site average for that period across all monitoring years. Fluxes at the bare-shallow installations ranged from 1.3 ± 1.0 to 1.8 ± 1.3 µmol m2s1, and those at the bare-deep installations ranged from 1.4 ± 1.5 to 1.8 ± 1.7 µmol m-2s-1. Fluxes at the natural-shallow installations ranged from 4.2 ± 3.7 to 5.3 ± 3.6 µmol m-2s-1. The IBDP benefited from the development of such a comprehensive data set, although similar high-density, high-frequency monitoring protocols may not be practical for larger scale demonstration and commercial projects. The IBDP network was not expected to provide a protocol for how to deploy soil flux monitoring, but rather to provide a detailed understanding of flux behaviors at one site so that those experiences could be used to guide the development of monitoring programs at other carbon capture and storage sites. Fluxes at the bare-shallow installations were smaller and less variable than those at the natural-shallow installations and would be more effective in identifying a surface leak signature if one were to occur. Therefore, the bare-shallow installation is suggested as the preferred type for monitoring soil CO2 fluxes at an industrial carbon capture and storage site. However, we recognize that this type of installation (e.g., one with periodic herbicide treatment) may not be practical for all sites. Measurements from a natural-shallow installation would also likely be able to detect leaks, but this type of installation could be more difficult to use because of the added CO2 flux variability of natural vegetation. In the closed-chamber method, flux measurements rely on gas exchange across the soil-atmosphere boundary, but freezing temperatures often prevented this gas exchange, which is a significant drawback to this monitoring technique. The closed chamber method can be used to provide estimates of leak quantification, but given the anticipated nature of leaks (e.g., diffuse, with small surface expression, possibly sporadic, with potentially low flux rates compared with the range of natural variability, and having potential surface expression as methane), soil flux was not used as a primary indicator of leakage at the IBDP. Instead, it was used as a point of reference to define flux variability over the life of the project should significant anomalous signals be observed. For researchers who wish to conduct further analyses, soil CO2 flux data collected at the IBDP from 2009 to 2015 are available in electronic format on request.