Two types of biochar obtained from waste from the coffee chain, the grounds (waste generated in the production of soluble coffee) and the parchment (generated as coffee is pulped), and incorporated into the soil proved to be efficient in reducing contamination by heavy metals and improving soil quality. Biochar can be obtained from any biomass, such as coffee chain waste, in line with principles of socio-environmental responsibility, circular economy and sustainability. According to the researchers, the results regarding the levels of calcium, copper, organic carbon and activity of the enzymes dehydrogenase and protease were used as a basis to calculate a Soil Quality Index (SQI), allowing the assessment of the impacts of biochars. The soil sample with biochar made of coffee parchment presented a higher SQI, but both managed to reduce the concentration of metals in the soil, and thus contribute to improving soil quality. The research was led by Aline Coscione from the Agronomic Institute (IAC), in collaboration with Embrapa Environment. The experiment lasted for 90 days and by the time it started to be conducted, there had been limited understanding of the use of biochar to improve soil quality as measured through SQIs. According to Cristiano Andrade, a researcher at Embrapa Environment, soil quality refers to its capacity to perform roles like supporting plant production and regulating water flow in the environment, which are important for ecosystem balance. Thus, quality indices can combine variations in soil attributes and measure the performance of one or more of such roles in the environment. The research team addressed that as the study progressed. Enzymatic activities, for instance, play a crucial role in nutrient cycling and thus in maintaining soil fertility. The enzyme dehydrogenase is particularly important in biochemical processes as it relates to the oxidation of organic matter. Meanwhile the enzyme protease is involved in the soil nitrogen cycle. Calcium content is closely related to agricultural production, especially in tropical soils, which are naturally acidic and have unsatisfactory nutrient levels. Despite copper being a micronutrient, it can become toxic at high concentrations. To obtain the SQI, the approach to enzymes is "the more the merrier", since they are involved in nutrient cycling and, consequently, in plant development. For copper, the approach is it is desired “within a range”. In the latter case, soil quality losses occur when the copper content is above or below the limits of said range. . According to Ruan Carnier, who participated in the research as a PhD candidate at IAC and who is now a collaborator at Embrapa, the action of the enzyme dehydrogenase obtained a very low score in all the treatments, with amounts below the established limit. “As it is an intracellular enzyme, Carnier explains, it directly reflects the activity of microorganisms and it is highly sensitive to changes. Thus, in this study, the reduced activity of the enzyme was mainly attributed to the toxicity of the metals present in the soil”. The biochars we used are alkaline, Carnier explains. "When they are added to the soil, biochars raise the pH of the medium, which consequently reduces the availability of heavy metals. In addition, biochars have specific characteristics such as porosity and functional groups on their surface, which contributes to the sorption of heavy metals, reducing availability in the soil". The full paper by Ruan Carnier, Cleide Aparecida de Abreu, Ana Olivia Fernandes, Adriana Parada Dias Silveira, Aline Renée Coscione (Agronomic Institute - IAC), and Cristiano Alberto de Andrade (Embrapa Environment) can be accessed here.