Ground Zero? Let’s get real on regeneration! Report: Assessing greenhouse gas emissions from post-harvest residue management in coffee and cocoa production systems

The critical need for the world to confront climate change has prompted major food industry players to make ambitious pledges to reduce greenhouse gas (GHG) emissions. Considering that a significant portion of GHG emissions within supply chains arise during the production of agricultural commodities, attention has now shifted towards “Regenerative Agriculture” as a pivotal strategy to reducing the carbon (C) footprint, alongside enhancing soil health and safeguarding biodiversity, while ensuring sustainable production and providing living incomes for farmers. The production processes of coffee and cocoa generate a substantial volume of residues. These residues emerge during various stages of post-harvest processing, encompassing wastewater, coffee husks, cocoa pod husks, pulp, and bean shells. Only in 2022-2023, the production of coffee residues reached about 10 million tonnes of solid waste and around 150 billion litres of wastewater globally. For cocoa, the residue production is estimated to be around 12.4 million tonnes per year. Improper handling of these residues can lead to a range of environmental challenges, including water pollution and eutrophication, K leaching, and the release of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). C footprint calculations (expressed as CO2-C emission rates per kg of
product produced) require the inclusion of the emissions from all activities inside the farm (on-farm), including those upstream related to the manufacture of farm inputs (off-farm) such as fertilizer and transport of materials to the farm, as well as post-harvest processes down the value chain. By understanding the intricacies of residue generation and exploring the sources of GHG production, stakeholders in these industries can work towards minimizing the ecological footprint in the supply chain and promoting more sustainable production.

In this report, we provide a comprehensive overview of the various residues produced during the processing of coffee and cocoa beans from harvest to green/dried beans, including processing that takes place directly on the farm and at centralised post-harvest processing facilities, such as washing stations in the case of coffee or cooperatives/collection centers in the case of cocoa. We also review the most common residue management strategies farmers use and their environmental implications in terms of GHG emissions, with a focus on CH4 and N2O. The primary objective is to identify the main points of environmental concern and propose methods for monitoring CH4 and N2O production during solid residue and wastewater treatment. The most common practice farmers use is leaving solid residues on the farm or centralised facilities in piles without proper management, probably leading to high GHG emissions, especially CH4. Similarly, in farms/ centralised facilities that use water for processing, wastewater is typically left in ponds without additional treatment. However, limited data is available on the total GHG emissions in such circumstances. Further research is needed to understand the role of emissions from residue piles and wastewater ponds in GHG production and their impact on the overall C footprint
of coffee and cocoa production. Considering all the available methods used to measure CH4 and N2O emissions, it is proposed to use the static chamber method to quantify GHG emissions from residue piles and the floating chamber method in combination with the headspace equilibration method for wastewater. These methods are relatively inexpensive, easy to adopt, versatile, and adaptable to varying field conditions. Employing these methods enables comparisons of different treatments across various piles and ponds, facilitating the development of strategies to decrease
GHG emissions during compost production and wastewater treatment. Studying the entire life cycle of coffee and cocoa industry products, including residue management practices, is crucial for developing sustainable solutions and reducing environmental impact.