Tea Bag Index

The degradation of organic material is crucial for the growth and metabolism of plants and microorganisms: the necessary nutrients become available through decomposition and mineralization. This also releases the greenhouse gas carbon dioxide (CO2) into the atmosphere. Rapid degradation leads to increased CO2 emissions, while slow degradation increases carbon storage in the soil. In order to better understand the global CO2 cycle, it is therefore important to gather more information on decomposition rates in different soils.

With this tea bag method even laymen worldwide can make a valuable contribution to science and the environment: They simply bury tea bags in the ground, dig them out again after a while and weigh them. The weight loss indicates how much plant material, in this case tea, has been decomposed. This simple and inexpensive method for determining decomposition rates has been scientifically confirmed, and corresponding initiatives have already been launched in numerous countries around the world.

With these experiments, comparable data can be obtained worldwide, especially from regions for which no corresponding information is currently available


In addition to the partner school HBLA für Wein- und Obstbau Klosterneuburg, 150 school classes throughout Austria have registered for the project to investigate the decomposition processes of plant material in the soil.

The project involves burying tea bags in a green area (meadow, maize field, forest ground) close to the school and recording GPS data from the site. On the photos below you can see the students preparing their tea bags and then burying them with joy. After three months, the bags are excavated, dried, weighed and the results, including GPS data, are then entered into a map, which scientists can use to compare worldwide data. For example, the influence of location and soil composition on the rate of decomposition can be analysed. The basics of soil as well as the evaluation and interpretation of the data will be presented to the teachers involved in a workshop. At the big final presentation the combined results of all school classes - spread all over Austria - will be presented.

  • Target group: Pupils 10 years and older
  • Project duration: 2 years (September 2017 to August 2019)
  • Activities for schools: April/May/June 2018 (introductory workshop, burying tea bags), Sept 2018 (digging out tea bags, data evaluation), March 2019 (closing event)


Measuring soil activity with tea bags