This is a new issue of the newsletter from Deloitte Tohmatsu Sustainacraft.

Methodology Updates is a series covering carbon and biodiversity credit methodologies. This article introduces Isometric’s Enhanced Weathering in Agriculture v1.2 protocol, and a new module under public consultation.

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Author: Julia Dohner (Carbon Specialist)

Introduction

Isometric is a leading standard for crediting carbon removal via Enhanced Weathering (EW) in agriculture, and its certified projects are already delivering commercially. In April 2026, Alt Carbon issued 2,500 tonnes of enhanced-weathering CO₂ removal to Mitsui O.S.K. Lines (MOL), the largest single delivery of Isometric-certified EW credits to date. This newsletter article introduces the Isometric’s Enhanced Weathering in Agriculture v1.2 protocol, giving particular attention to how field measurements are used to quantify carbon removal. This article also discusses Isometric’s new module under public consultation, which describes how models can be used to supplement in-situ measurements for carbon removal quantification.

EW is a carbon removal approach intended to accelerate the slow natural process of rocks undergoing the chemical weathering reaction, which eventually sequesters carbon in the ocean for 10,000+ years (Kanzaki et al., 2023). Under Isometric's protocol, removals by EW are quantified using chemical measurements taken from the soil or soil porewater. However, high precision and sampling density are necessary to resolve the weathering signal, which is very small in the background of natural processes occurring in an open agricultural setting. The protocol prescribes sampling layout approaches, and rewards reduced uncertainty achieved through increased sampling.

While current methodologies focus on measurement-based removal quantification in EW, the use of models to supplement in-situ data has the potential to reduce measurement costs and unlock scale. However, weak guidance on models risks overstating removals and eroding credit integrity. Isometric’s new module attempts to address these risks by providing guidelines for models behind very high verification hurdles, which Isometric acknowledges no model may currently clear. The module signals where the market is heading rather than opening a usable pathway today.

This article first reviews the scientific basis of enhanced weathering as a carbon removal approach. It next outlines the structure of Isometric’s protocol, including eligibility and applicability, system boundaries and LCA emissions, net CDR and uncertainty treatment, monitoring, reporting and verification, and durability. It then explains the rationale for Isometric’s new module and gives a brief overview of its contents. Finally, it compares Isometric's EW protocol with Puro.earth's, another major standard with an enhanced weathering methodology.