A comprehensive analysis of operations and mass flows in postharvest processing of washed coffee

Although coffee is one of the most valuable and widely traded agricultural commodity in the world (US$83 billion in 2017 revenue), little information exists in the scientific literature regarding coffee bean postharvest processing. In particular, sustainability analyses require information on the coffee bean mass and property changes during processing, from harvest to final consumption. In this study, a detailed analysis of the washed or wet-processed method for coffee postharvest processing is provided. Mass flow data were collected through site visits, surveys, laboratory measurements, and interviews with coffee wet and dry mill operators in several countries throughout Central America and Mexico, as well as roasters and cafes in the United States, to establish representative mass flow rates and process flow diagrams from harvest to cup. Results indicate that 100 kg of harvested coffee cherries will on average yield 2.6 kg of mass consumed by humans as exported coffee, equivalent to approximately 839 metric cups (250 ml) of drip brew coffee or 897 metric shots (30 ml) of espresso. The remaining 97.4 kg provide opportunities for development of alternative products, and other economic uses. Importantly, the data suggests that more mass is lost during depulping in practice than previously indicated by laboratory measurements. This study provides a foundation for further investigations in the fields of equipment improvement, byproduct utilization, and environmental and economic sustainability of the coffee processing and distribution chain.