Evaluation of the agronomic potential of the byproduct of anaerobic digestion of agri-food waste (digestate) as a fertilizer: Measurement of the relative chlorophyll index (RCI) as a diagnosis of the nutritional status of hydroponic lettuce crops

• Grant number: 25/10813-6
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: August 01, 2025
• End date: July 31, 2026
• Field of knowledge: Agronomical Sciences - Agronomy
• Principal Investigator: Célia Regina Montes
• Grantee: Luísa Ferreira Gomes
• Host Institution: Instituto de Energia e Ambiente (IEE). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The use of a byproduct of anaerobic digestion of agri-food waste (digestate) in plant production is not yet a reality in Brazil. However, research is being developed to analyze its application in replacing conventional fertilizers in vegetable production. Plant production using biofertilizers transforms food production into a circular economy, with the potential to minimize the effects of organic waste generation. The project will focus on determining chlorophyll concentrations in lettuce produced in a hydroponic system to determine the IRC index (relative chlorophyll index) over the different harvests during the year, and its correlations with physiological, nutritional and productive parameters of lettuce. The project will be carried out in an agricultural greenhouse installed next to the IEE/USP Biogas Plant, which produces biogas and has digestate as a byproduct. The experiment in which the IC project is included is being conducted in randomized blocks with five treatments and four replicates, with the treatments being the replacement of the commercial nutrient solution for lettuce with diluted digestate, applied via the NFT system (laminar flow of nutrients technique), which is part of the larger project CNPq Project 406348/2022-7 "Valorization of digestate produced in biogas plants of USP and UFC in conventional and hydroponic cultivation". It is expected that fertigation with digestate in different concentrations, replacing the nutrient solution, will bring agronomic benefits without compromising the nutritional status of the plants, monitored by measuring chlorophyll levels and their correlation with the physiological and productive parameters of lettuce. Keywords: Circular economy, Food waste, Digestate, Lettuce