The Future of Biochar in Cocoa Systems

Biochar application has shown to have the potential to significantly increase crop yields in tropical agricultural systems. Reportedly, biochar application can positively affect root development by increasing root biomass and root surface area (in some cases more than 30%), thus alleviating plant nutrient and water deficiencies. Implementation of biochar-based fertilization to smallholder cocoa (agroforestry) systems and other tropical perennial crop systems can contribute to achieving a number of sustainable development goals, namely SDG1 (no poverty), SDG2 (zero hunger), SDG 13 (climate action) and SDG15 (life on land). This is, through providing more income and higher yields to farmers in conjunction with high carbon sequestration while reducing the fossil-fuel dependence of industrial fertilizer production and enhancing a number of other ecosystem functions and services.
The ecosystem service of sequestering carbon is a major advantage of biochar and therefore of high interest. An iterative process of biochar application possesses the potential to build up substantial carbon sinks. The agronomic application of pyrogenic carbon is recognised as a crucial (and multi-functional) negative emission technology. It has the potential for high offsets and rapid implementation according to the latest report of IPCC (2019). Moreover, through verification and trading of biochar-based carbon credits (e.g. through EBC, 2020) additional revenues can be generated by cocoa farmers.
Looking at the benefits of biochar on cocoa systems is a novel research line with a high societal impact potential. To date, no published scientific research exists about the effect of biochar-based fertilization on cocoa crop productivity using field trials. On the other hand, our research is supported by a fast-growing biochar related research community delivering steadily more data for other crops as well as new methods on biochar-based fertilization and soil improvement in tropical agriculture. This can potentially benefit research and technologies applicable to cocoa cultivation. Since 2020 the Institute of Tropical Plant Production and Agroecosystem Modelling (TROPAGS) of the University of Göttingen collaborates with the Ithaka Institute for Carbon Intelligence in a research effort to deepen the understanding of the agronomic potential of biochar application in cocoa production systems. This collaborative research is carried out in the greenhouse and through field trials and addresses relevant knowledge gaps in basic understanding and more applied research topics. Field experiments are currently conducted in Ghana, where the Ithaka Institute supported by the University of Göttingen is working in close cooperation with the local cocoa farmer communities and with a private sector partner who holds a major share of the global cocoa market.

Fig.1: Cocoa – Biochar trial at the University of Göttingen

During a field trial pilot launched in October 2020 in Ghana, a decentral scheme of biochar production was tested in Ghana. The team deployed “Kon-Tiki” kilns, i.e. flame curtain pyrolysis, to convert production residues of the coco value chain, namely pods and pruning wood, into biochar. Kon-Tiki kilns can be established decentralised and at very low costs.

Fig.2: Map, modified from Läderach et al. 2013, showing project locations in Ghana

The biochar produced, was consecutively milled and converted into a liquid biochar-based fertilizer and applied directly into the cocoa plant root zone through a novel injection technology. For the first time this new technology allows for a biochar incorporation in already established perennial systems. In Ghana, field experiments have been established covering distinguished cocoa age classes (mature and seedling stage) and climatic zones (wet region with nutrient constrains and dry region with water constrains). Parameters ranging from drought (seasonal Harmattan) survival rate, growth and vigour, to yield data are continuously monitored. There are plans to upscale to other cocoa production regions including Indonesia, Ecuador and Ivory Coast.
The ongoing field research will be complemented by laboratory and greenhouse-based trials at the University of Göttingen to enhance the mechanistic understanding of the underlying principles. The experiments shall utilize lysimeters and rhizoboxes to evaluate the effect of biochar application on drought stress, root morphology, phosphorus mobilisation and aluminium immobilisation.

Fig.3: Geo injection technique deployed in mature cocoa