Composting Coffee Chaff (Silverskin)

Coffee silverskin is high in nutrients, but contains recalcitrant and phytotoxic compounds, limiting its use as a mulch or soil amendment. Fortunately, composting can reduce or eliminate these problems. Composting has been shown to degrade the phytogenic compounds in coffee silverskin, providing a route for safely returning coffee silverskin nutrients to the soil. Picca et al. (2022) have shown that composting with garden prunings, and biochar eliminated phytotoxicity while making nitrogen readily available. Gonzalez-Moreno et al. (2020) demonstrated a similar outcome with vermicomposting. However, they noted that coffee silverskin can be toxic to worms in high concentrations.

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