CAFAMORE – CArbon FArming MOnitoring and REgistry

Background and Objective

Carbon farming refers to the application of certain agricultural management practices with the aim of storing atmospheric CO₂ in the soil in the long term by building up soil carbon. Under the CRCF guideline, this additional accumulated soil carbon is to be made eligible for trading on voluntary carbon markets through so-called CO₂ certificates. However, this requires the collection of large amounts of spatial and temporal soil information in order to determine the effectiveness and uncertainties of the measures implemented. 

The calculation of soil carbon stocks is based on the soil carbon content and bulk density of the soil, which are subject to high seasonal and spatial variability. This leads to high uncertainties in determining changes in soil carbon stocks and thus triggers controversial discussions at the political, scientific and social levels about whether carbon farming is a reliable climate mitigation measure or whether there is a risk of ‘greenwashing’. This also applies to the permanence of this soil carbon, i.e. the question of whether long-term sequestration of carbon in the soil is possible, even under the influence of changing climatic conditions.

The aim of the CAFAMORE project at the Thünen Institute is therefore to develop robust methodologies to minimise uncertainties in soil carbon quantification and to create the basis for reliable monitoring of carbon farming measures. In cooperation with project partner FiBl from Switzerland (https://www.fibl.org/de/standorte/schweiz/departemente/bodenwissenschaften/bodenfruchtbarkeit-klima) and AgriCarbon from Scotland (https://www.agricarbon.co.uk), investigations are being carried out to quantify the spatial and temporal variance of soil carbon and to develop a permanence index that provides information about the stability and longevity of soil carbon. In order to assess the effectiveness of the measures, information on the business as usual, i.e. the trends of soil carbon without the implementation of carbon farming (‘baseline’), must also be estimated. This baseline work is being carried out in cooperation with project partner ILVO (https://pureportal.ilvo.be/en/projects/koolstoflandbouw-monitoring-en-registratie/).

Furthermore, CAFAMORE is investigating the possibilities of verifying reported carbon sequestration using remote sensing and increasing the reliability of CO₂ certificates. Together with the inter-institutional Thünen Remote Sensing (ThEO) (https://www.thuenen.de/de/thuenen-institut/verbundstrukturen/thuenen-fernerkundung), methods are being further developed that enable changes in soil carbon stocks to be detected on the basis of satellite data (see  DOI:10.1111/gcb.17608).

Approach

At ten locations around Braunschweig, soil samples will be taken every four to six weeks over a period of two years to a depth of 50 cm and analysed for bulk density and carbon content in order to map the seasonality and variance of carbon stocks. The sites studied differ in terms of both soil texture (sandy – silty – loamy – clayey) and tillage (conventional – reduced tillage – no tillage), thus covering a broad management gradient. To supplement the sampling, additional analytical methods such as soil spectroscopy (DRIFTS) and carbon fractionation are used to determine the stable and labile carbon pools and draw conclusions about the permanence of the sequestered carbon.

In addition to field studies, data from the German Agricultural Soil Inventory (BZE) and other soil monitoring data are used to test the extent to which soil carbon sequestration can be derived from satellite data. To this end, changes in soil reflectance are evaluated and correlated with reference data in order to calibrate spatiotemporal soil carbon models and generate comprehensive maps.