Soil Carbon Calculator

This calculator estimates how much CO2-equivalent a field can sequester per year by stacking published base per-acre rates for four common regenerative practices: cover cropping (0.4 tCO2e/acre/year, in the range Poeplau & Don's (2015) meta-analysis of cover-crop trials found — about 0.32 tonnes of carbon per hectare per year), no-till (0.35, informed by West & Post's (2002) global analysis of long-term tillage trials, which found a conventional-to-no-till shift sequesters roughly 57 g C/m²/year on average), compost application (roughly 0.085 tCO2e per ton applied, based on compost's organic-matter and carbon content with a long-term retention factor), and rotational grazing (0.9, the largest single lever if applicable, reflecting published field data on adaptive multi-paddock grazing from Teague et al. (2016)). The three practice rates other than compost are then multiplied by a "soil factor" that rewards starting from degraded ground: soils with low current soil organic carbon (SOC) have more room to gain carbon and sequester faster, so on a very depleted field (SOC near 0.1%) that factor can run as high as ~1.5x, pushing cover cropping toward ~0.6 and grazing toward ~1.3 tCO2e/acre/year — while carbon-rich soils see the factor shrink toward its 0.5x floor near saturation. The annual per-acre rate is multiplied by acreage for a field-wide total, then projected forward year by year with a straight-line reduction of 1.5% of the initial rate per additional year (floored at 30% of that rate), reflecting that sequestration slows as soil carbon nears a new equilibrium — a steady arithmetic taper, not a compounding percentage-of-remaining decay.

The projected SOC increase converts total sequestered CO2e back to elemental carbon (dividing by 3.667, the molecular weight ratio of CO2 to C) and assumes the top 6 inches of soil weighs about 1,000 tons per acre, a standard rule-of-thumb bulk density figure. Carbon credit revenue is a simple multiplication of tonnage by the entered market price and carries all the volatility of the voluntary carbon market itself. These are literature-based planning estimates, not measured results — actual sequestration varies enormously with climate, soil type, and monitoring methodology, and real carbon credit programs require third-party verification before any of this projected revenue becomes actual income.