Durable MAOC gain
—
tC/ha over period
Overflow to POM
—
tC/ha · higher reversal risk
Years to saturation
—
yr
MAOC share
—
% of total gain that is durable
Producer
—
tCO₂/ha credible as permanent sequestration
—
tCO₂/ha in POM — disclose separately or exclude
Base sustainability claims on MAOC gain only. POM is real sequestration but carries reversal risk that undermines a permanent removal story.
Project developer
—
tCO₂/ha issuable as high-permanence credits
—
credit stream status at saturation
POM tonnes may be issuable under some methodologies but attract buffer pool contributions and a permanence discount at market.
Ratings / investor
—
% of total gain in durable MAOC fraction
—
permanence signal — MAOC turnover century-scale; POM decade-scale
Projects below 60% MAOC share warrant deeper scrutiny of permanence claims regardless of methodology used.
MAOC accrual trajectory
MAOC stock
Cumulative POM overflow
MAOC capacity ceiling
Simplified model: annual MAOC increment = CUE × C inputs, capped at remaining mineral capacity. Excess enters POM. Does not model MAOC turnover or priming effects. CUE for managed agricultural systems is largely unmeasured — use as sensitivity analysis, not prediction.
References
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[1]
Sokol, N.W. et al. (2025). Microbe-mineral interactions dominate mineral-associated organic carbon formation in agricultural soils. Science Advances, eadv9482. doi.org/10.1126/sciadv.adv9482
[2]
Holm, S. et al. (2025). Tillage and microbial carbon use efficiency: a systematic review. Journal of Sustainable Agriculture & Environment.
[3]
Kallenbach, C.M. et al. (2019). Microbial physiology and necromass regulate agricultural soil carbon accumulation. Frontiers in Microbiology. doi.org/10.3389/fmicb.2019.01594
[4]
Cui, Y. et al. (2026). Global patterns in microbial carbon use efficiency driven by soil abiotic conditions. Science Advances, eadz5319. doi.org/10.1126/sciadv.adz5319
[5]
Georgiou, K. et al. (2022). Global stocks and capacity of mineral-associated soil organic carbon. Nature Communications, 13, 3797. doi.org/10.1038/s41467-022-31540-9
[6]
Hassink, J. (1997). The capacity of soils to preserve organic C and N by their association with clay and silt particles. Soil Biology and Biochemistry, 29(10). doi.org/10.1016/S0038-0717(97)00060-X