Green Technology

Widespread questions in soil carbon monitoring

This text is sponsored by Indigo Ag.

Advancing sustainable farming means working to enhance the best way we measure each its monetary and environmental advantages. This permits a stronger market to develop the place farmers are compensated for transitioning to regenerative administration. 

One solution to obtain that is through the use of modeling and soil sampling to set a excessive commonplace for a way soil carbon modifications are quantified. That’s why in 2019, Indigo Ag launched Carbon by Indigo to interrupt new floor in soil carbon quantification in shut partnership with the scientific neighborhood. Our DayCent-CR biogeochemical mannequin is calibrated, validated and reviewed by impartial specialists — after which accredited to be used by crediting packages such because the Local weather Motion Reserve (CAR). Importantly, our strategy additionally accounts for the uncertainties inherent in carbon measurement. 

Purchase-in from the scientific neighborhood is important for supporting the development of fashions corresponding to DayCent-CR. Just lately, the Indigo staff printed a peer-reviewed paper on Indigo Ag’s carbon quantification mannequin within the main science journal Geoderma. Within the paper, we offer deeper transparency for a key element of our total MRV (monitoring, reporting and verification) processes. This expands on the documentation and overview of the mannequin validation to be used beneath the CAR Soil Enrichment Protocol (SEP) which can be already publicly obtainable together with different documentation for every of our credit score issuances. 

Indigo is the one agricultural offset producer to have each registry approval of our mannequin validation in addition to tutorial peer-review, demonstrating our dedication to the scientific integrity of our packages. Publication of Indigo’s calibration and validation work in Geoderma will enhance stakeholder (together with patrons, verifiers, lecturers, authorities and others) confidence within the high quality of Indigo’s sustainability packages and carbon credit. 

But many sustainable farming stakeholders, together with patrons, verifiers, lecturers and regulators have questions on soil carbon monitoring. Listed below are 4 frequent questions we obtain: 

What’s a soil carbon mannequin, and why do we have to calibrate and validate it?

Soil carbon monitoring instruments embody biogeochemical course of fashions, corresponding to DayCent-CR, that simulate modifications in soil natural carbon (SOC) on the soil-plant-atmosphere interface. Instruments corresponding to this enable us to quantify the variety of soil carbon credit produced by regenerative agriculture. DayCent is the every day time-step model of the CENTURY mannequin originating out of Colorado State College, and the “CR” signifies the proprietary “credit-ready” model utilized in Indigo’s carbon crediting program. We use the mannequin because the core element of the excellent quantification strategy required by the Soil Enrichment Protocol.

Whereas DayCent-CR comes with a normal “manufacturing unit setting,” we have to calibrate it to the assorted crops, practices and geographies which can be inside Indigo’s mission. We then have to measure how nicely the calibrated mannequin performs by a validation train. If a mannequin is used with out being calibrated, or exhibits poor efficiency by validation, it’ll produce inaccurate estimations. As credit are bought by corporations to offset their very own emissions, it’s of extremely excessive significance to make sure that any carbon credit score produced and bought is predicated on actual carbon reductions and sequestration.

What information are used within the calibration and validation course of?

Customers of soil carbon fashions should be cautious concerning the information used within the calibration and validation course of. For DayCent-CR, the mannequin is calibrated and validated with measurements of SOC from printed discipline research obtained by a literature search. The CAR Soil Enrichment Protocol (SEP) mannequin validation steerage units the standards for what SOC information can and can’t be included. In complete, we used 668 SOC inventory measurements for calibration and validation of DayCent-CR.

Our mannequin can even be improved over time by ingesting further, high-quality information.

How do you handle mannequin uncertainty?

To supply credit, we use our calibrated DayCent-CR coupled with precise soil carbon measurements collected from mission fields. The SOC measurements are then used to initialize our mannequin. This course of permits us to supply credit on a a lot bigger acreage and on a shorter timescale than soil sampling alone. “Validating DayCent-CR for cropland soil carbon offset reporting at a nationwide scale” additionally explains how we calculate mannequin uncertainty and the implications of mannequin uncertainty. We’ve additionally mentioned uncertainty on this place paper: “Managing Quantification Uncertainty in Agricultural Carbon Markets.” With mannequin enhancements from DayCent-CR 1.0 to DayCent-CR 1.0.2, we had been capable of cut back our project-level uncertainty deduction from 37 p.c to 18 p.c. No mannequin will give estimates which can be one hundred pc sure, so we deduct credit from the general complete that we produce to account for uncertainty and guarantee we’re promoting an appropriately conservative variety of credit.

Why is it essential to report mannequin outcomes?

To ensure that credit to bear verification in opposition to the CAR SEP, we should clarify our mannequin validation course of and showcase the leads to a validation report. The experiences should be reviewed by an impartial third occasion modeling knowledgeable. As soon as accredited, these experiences seem on CAR’s web site and are accessible for anybody to learn and scrutinize. 

Because the inception of the carbon program, we’ve got accomplished two mannequin validation experiences: DayCent-CR model 1.0 in 2021 and DayCent-CR model 1.0.2 in 2022. Each time we add a brand new crop or potential apply change to our mannequin, we should re-calibrate it and create an up to date mannequin validation report.

“Validating DayCent-CR for cropland soil carbon offset reporting at a nationwide scale” highlights the outcomes from Indigo’s second validation report, the place we added cotton as newly eligible crop in 2022.

What’s subsequent for soil carbon measurement?

In 2019, we began a long-term, large-scale soil carbon experiment on cropland fields which have transitioned to regenerative administration. We’re starting to research soil carbon inventory change at early (lower than 5 a 12 months) time scales. We plan to publish the information, after which add them to our mannequin calibration and validation dataset to enhance DayCent-CR. The experiment is ongoing, and we’ll proceed to watch SOC and extra soil well being properties.

Be taught extra from Indigo Ag concerning the progress being made to make agriculture extra sustainable for individuals and the planet. 


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