Permanence Science for Credits

Same science, different program interpretations. Do not mix thresholds across registries.

Source	Threshold / use	Horizon
IPCC 2019 · estimates soil C stock change from biochar	Pyrolysis temperature class for F_perm; H/C_org & O/C as future options	100 years
NRCS CPS 336	H:C_org max 0.7 (practice eligibility—not a credit)	Soil amendment
Isometric soil	H/C_org < 0.5, O/C_org < 0.2; F_durable from Woolf-style (200y) or Ro (1000y)	200 or 1000 years
CSI Global Biochar C-Sink 3.3 · CSI GPC vs SPC Permanence Classes	H/C_org ≤ 0.40 for any GPC; > 0.40 = SPC only; Ro≥3.8% or HyPy≥90% → 90% GPC	GPC >1000y; SPC ≤1000y
Verra VM0044	H/C_org → Table 3 permanence factors; high ratios excluded	100 years
Puro Edition 2025	CORC200+ (“several centuries”); revised decay; Ro encouraged but does not yet quantify	Several centuries
EBC/WBC	Product quality classes feeding CSI / referenced by others	Quality + C-sink inputs

Two camps (active divergence)

Decomposition-model camp: IPCC appendix, models soil GHG from biochar, Puro CORC200+, Isometric 200y
Inertinite / Ro camp: inertinite permanence benchmark; Isometric 1000y; CSI upper class

Puro explicitly chose centuries not millennia pending more integrated science (Puro permanence post, 2025-07-03).

See also science-side Permanence hub (H-Corg and O-Corg, Woolf IPCC Fperm, Reflectance Ro and HyPy, Soil Temperature and Environment, Permanence Debates) and Consensus vs Debates. Do not duplicate methodology thresholds into those science notes.

Primary links