Preliminary Analysis on Bio-Acidification Using Coffee Torrefaction Waste and Acetic Acid on Animal Manure from a Dairy Farm

This study investigates bio-acidification as a method to decrease the pH of animal manure in dairy farms through the application of coffee silverskin (i.e., a coffee torrefaction waste) and acetic acid. The aim was to focus on the preliminary analysis needed to assess the suitability of using this mitigation strategy. This analysis was carried out by developing a three-step methodology. The first step included the identification of the appropriate proportions of coffee silverskin and acetic acid at the laboratory scale; in the second step, the best treated proportions were analysed in field conditions to compare the statistical differences among the pH of the control and treated samples. In the third step, territorial evaluation was carried out to verify the availability of the coffee waste in the territory based on the use of a Geographic Information System (GIS). Based on the results, a reduction of 38% and 31% in pH was observed in samples treated with acetic acid and coffee silverskin at the laboratory scale and in field conditions, respectively. The territorial analysis showed that it is possible to valorise this agro-industrial waste while minimising environmental impacts due to transportation if the coffee industry is located within a 75 km distance.