Martin Luther University Halle-Wittenberg

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Sustainable soil amendment strategy enhancing carbon sequestration and carbon dioxide removal in European Agriculture (SUSCARBO)

Climate-smart agriculture and greenhouse gas mitigation through biochar application?

Soils are an important carbon sink, as they contain more carbon than stored in terrestrial vegetation and the atmosphere combined. Several studies showed that there is still potential to store even more carbon in soils, if certain management practices are applied. This process of storing soil organic carbon (SOC) in soils, better known as carbon sequestration, describes how organic carbon is input into soils and converted into a long-term (> 100 years) stabilized form. At the same time, carbon dioxide is removed from the atmosphere by carbon sequestration. This sequestration process can be achieved using different strategies e.g. using soil amendments. In this context, biochar technology is a viable strategy because it has the potential to 1. increase SOC stocks in the long-term as the highly aromatic structure of biochar leads to a reduced microbial decomposition rate and a long mean residence time of approximately 556 years. And 2. biochar application also reduces soil-borne CO2 and N2O-GHG emissions, compared to conventional mineral fertilization.

Another approach which is often used as a fertilizer and soil amendment is manure. Manure is a collective term for excrements of different animal species, urine, plant materials and straw but also livestock feed residues and human household waste. Manure might also increase carbon in soils as these materials have high carbon content. However, organic matter in manure might also be easily degraded due to its high nitrogen content or its low carbon-to-nitrogen ratio.

In fact, rather the use of biochar as a fertilizer and soil amendment product seems to provide an all-round solution. However, as the biochar technology is a relatively “new” one, there is a lack of data regarding factors influencing the sequestration potential of biochar both in the short and the long-term. Especially the long-term nature of the sequestration effect is still little researched due to the lack of data from long-term field experiments.

This dissertation project addresses this research gap. In order to successfully answer the question whether the application of biochar on European soils is a more suitable option to sequester atmospheric carbon dioxide in the short and long term than conventional agricultural application practices, several ongoing but also already abandoned biochar trial fields will be resampled and analyzed. The focus will be not only on carbon stock change, but also on potential site-specific influencing factors. In order to broaden the horizon of carbon dioxide mitigation, upstream processes in the production of biochar will also be quantified and assessed using life cycle assessments. By using this holistic approach, it will be possible to outline climate-friendly and therefore sustainable production systems for Central Europe.