Soil liming

Summary

This methodology represents carbon dioxide (CO₂) emissions associated with the application of lime (carbonate minerals) to managed soils. The data and calculation methodology is sourced from the IPCC, as published in Volume 4, Chapter 11 - N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application of their 2006 IPCC Guidelines for National Greenhouse Gas Inventories.

The methodology

Emissions model

Liming is used to reduce soil acidity and improve plant growth in managed systems, particularly agricultural lands and managed forests. Adding carbonates to soils in the form of lime (e.g., calcitic limestone (CaCO₃), or dolomite (CaMg(CO₃)₂) leads to CO₂ emissions as the carbonate dissolves and releases bicarbonate (2HCO₃^-), which evolves into CO₂ and water (H₂O).

The methodology calculates CO₂ emissions based on the mass-balance of carbon (C) applied during treatment. This assumes that all C added to soils is eventually emitted as CO₂.

This methodology represents the IPCC Tier 1 approach.

Model data

The precise relationship between the quantity of lime applied and the quantity of CO₂ emitted depends on the mineralogy of the lime used, and, in particular, its carbon content. Carbon content (by weight) factors are provided for two carbonate minerals - limestone and dolomite. These values allow the conversion of a quantity of carbonate into a quantity of C.

In addition, this methodology uses a second conversion factor, representing the ratio of the molecular mass of CO₂ and the atomic mass of C. This quantity allows the conversion of a quantity of C into the corresponding quantity of CO₂. In combination, these two conversion factors enable the conversion of a quantity of carbonate into a quantity of CO₂ emitted - under the assumption of mass-balance.

Activity data required

CO₂ emissions are directly proportionate to the quantity of lime applied, which therefore needs to be specified in order to make an emissions calculation.

Calculation and results

The CO₂ emissions calculated by this methodology represent those attributable to the specified quantity of lime applied to managed soils.

Additional information

Lime applied in fertilizers

According to IPCC advice, lime which is applied to managed soils within a broader mixture of fertilizers should be accounted for using this methodology.

Related methodologies

A number of other methodologies focus on emissions from managed soils. These include those arising from the addition of urine and dung, urea and synthetic and organic fertilizers, as well as organically-managed soils.