About 6 million tons of coffee waste are generated annually in the world, which in most cases are not recycled, accumulate and have a negative impact on the environment due to the content of caffeine, tannin, polyphenols and other toxic substances. The use of coffee waste as organic fertilizer is limited by the presence of the same toxic compounds. A possible approach to reducing the negative impact of coffee waste on soil biota may be their composting, including vermiculture. This study conducted an ecotoxicological assessment of coffee waste before and after vermicomposting using earthworms Eisenia andrei. Initial waste showed high toxicity: coffee grounds were classified as hazard class II, coffee chaff − as hazard class III. After vermicomposting, toxicity decreased: samples with 25−50% waste content became low hazardous (class IV), and with 100% − moderately hazardous (class III). The study confirmed that vermicomposting is an effective method of coffee waste detoxification, allowing to obtain safe organic fertilizers. Dosages of no more than 50% of waste in compost were recommended for practical application.
S.M. Fortova (Wed,) studied this question.