Evaluation of spent coffee grounds biochar and its effect in plant growth-promoting

Abstract

Due to modern agriculture practices, such as the massive use of chemical inputs, and the growing level of greenhouse gas emissions, it is increasingly latent the need to find technologies that help to mitigate the impacts caused in the ecosystem. In this context, the use of biochar stands out, a material produced from the pyrolysis of biomass waste. Biochar has the ability to improve soil physical and chemical properties, besides contributing to carbon stock and increase of microbial biodiversity. Therefore, the present work aimed to evaluate the production of biochar from spent coffee grounds waste at different temperatures, test the immobilization of microorganisms on its surface and investigate its role in promoting the growth of the vegetable Eruca vesicaria subsp. Sativa (arugula). The produced biochar had its physicochemical properties characterized by acid-base titration and pH analysis. The porous structure of biochar, as well as the efficiency of the biochar-microorganism complex, was evaluated by Scanning Electron Microscopy. In the presence and absence of biochar and biochar-microorganism complex, the cultivated crops were evaluated by determining the number of leaves, the length of aerial parts, the weight of fresh aerial parts, and the weight of dry aerial parts. The produced biochar showed a porous structure with positive results for the immobilization of microorganisms. In terms of vegetable cultivation, the application of biochar on the soil did not produce significant differences in the quality of the seedlings when compared with the control. However, the use of spent coffee grounds biochar inoculated with A. platensis cyanobacterium promoted plant development, providing the best results for all variables. The found results suggest the use of spent coffee grounds biochar as a carrier of microorganisms and put in evidence the potential of A. platensis in plant growth promotion.