On-Farm Conversion of Cannabis Sativa Waste Biomass into an Organic Fertilizer by Microbial Digestion

Abstract

Nearly 90% of the total biomass of hemp plants grown for cannabidiol (CBD) is left to rot in piles, burned, or hauled to landfills post-harvest even though these residues are nutrient-rich. Composting is an option for waste management and nutrient recovery for hemp producers. However, materials, labor costs, time, and space needed to properly construct compost piles pose significant logistic challenges to smallholder farmers who want to manage their waste on-farm. Additionally, the high lignin content of cannabis hurd is often poorly degraded if the compost fails to meet national organic standards for thermophilic conditions. A potentially more efficient and cost-effective alternative is to convert leftover cannabis waste into bio-fertilizers through a semi-anaerobic process by adding microbial inoculants that specialize in lignin degradation. Imio Technologies, Inc. (Imio) developed cannabis-specific microbial inoculants designed to optimize the conversion of hemp waste into a bio-available form. Applied as a liquid culture, Imio microbes colonize wasted stalks and produce organic acids and oxidative enzymes that decompose lignin and release plant nutrients. This study aimed to investigate the ability of Imio microbial inoculants to degrade lignin-rich material into a fertilizer substitute. At the conclusion of a 3-week digestion period, biomass was transformed into a more bioavailable form with a nutrient profile similar to finished composts. Two-week cured fertilizer generated through this process promoted greater root:shoot ratios, which suggests plant growth promotion, compared to a synthetically fertilized control group. The digested hemp fertilizer also showed a value-added property of disease suppression against the soilborne pathogen Rhizoctonia solani.