FIELD NOTES: COLLECTING CARBON DATA
We Cannot Manage What We Do Not Measure
By growing rice and restoring wetlands, Metropolitan will stop and reverse subsidence, restore carbon to the land and potentially realize additional income to help maintain the levees and secure the integrity of the central Delta. One of the objectives of the Webb Tract Mosaic Nature-Based Solution grant is to reduce greenhouse gas emissions, so it is essential to quantify the island's emissions, which requires specialized equipment. Working with HydroFocus, Inc., an expert in hydrologic modeling and quantification of greenhouse gas emissions and reductions, Metropolitan purchased two eddy covariance stations and installed one in the agricultural area where the wetlands will be restored, and the other where the agricultural land will be used to cultivate rice.
Quantifying and marketing carbon credits requires a rigorous verification process using the data that the eddy covariance instrumentation provides. The HydroFocus team started collecting data in fields where wetlands and rice will be planted in September and October 2024, respectively. One year of data is necessary to estimate the baseline greenhouse gas emissions for comparison with the project conditions (rice and wetlands).
Subsidence is caused by the oxidation of organic compounds in the peat soils on Webb Tract. About 8 billion cubic meters of peat soil formed under wetland conditions in the Delta during the last 7,000 years. Starting in the mid-1800s, the wetlands were drained, and the peat soils were farmed. Exposure to aerobic conditions resulted in the microbial oxidation of the organic matter and the peat soils. As a result about 66% of the original accumulated peat soil disappeared.
The oxidation of these peat soils results in disproportionately large annual agricultural greenhouse gas emissions, which HydroFocus estimated at about 11 metric tons of carbon dioxide per acre and about 50,000 metric tons of carbon dioxide for the entire island. For comparison, the EPA reported that a typical passenger vehicle emits about 4.6 metric tons of carbon dioxide per year. Conversion of these disappearing soils to wetlands and rice will result in an estimated emissions reduction of about 30,000 metric tons of carbon dioxide annually.
The eddy covariance instrumentation shown in the picture above is being used to quantify the baseline emissions and will measure the emissions reductions from the conversion to wetland and rice. This will enable the verification of the project’s carbon benefit and sale of carbon credits. HydroFocus preliminarily estimated that annual income from the sale of carbon credits at about $583,700.
Webb Tract Project Manager Malinda Stalvey is participating in the newly formed Carbon Working Group, a collaborative effort initiated by The Nature Conservancy and the Delta Conservancy. This group aims to identify and remove barriers to projects that reduce greenhouse gas emissions, advance carbon sequestration, and generate carbon credits in the Delta.
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