Suitability of Co-Composted Biochar with Spent Coffee Grounds Substrate for Tomato (Solanum lycopersicum) Fruiting Stage

Abstract

Peat is the predominant component of growing media in soilless horticultural systems. However, peat extraction from peatlands destroys these fragile ecosystems and emits greenhouse gas emissions (GHG). Peat replacement by other growing media is, thus, paramount to ensure a more sustainable horticultural sector. This study investigated the agronomical performances of two spent coffee ground-based composts with and without biochar, during three different stages of tomato (Solanum lycopersicum L.) development: seeds germination (0–6 days), seedling development (7–49 days), and plant-to-fruit maturity (36–100 days). The two composts were used as peat replacement and mixed with peat at four different volumetric proportions: 100% (pure compost), 50%, 30%, and 15%. The substrates had a stimulant effect on seed germination but induced stunted growth due to the elevated electrical conductivity. For the latest stages of plant development, compost with and without biochar mixed with peat at 50% promoted an increase in fruit production of 60.8% and 100.3%, compared to the control substrate. The present study provides evidence that combining biochar with spent coffee ground compost represents a potential alternative for peat-based growing media promoting a circular production model in the horticultural sector, but the results are dilution- and plant development stage-dependent.

Toward Circular Economy: Potentials of Spent Coffee Grounds in Bioproducts and Chemical Production

“…SCG biochar was reported to show a high removal efficiency and stabilization of trace elements in soil, with further studies being necessary on its biological toxicity [128]. SCG-derived biochar has been found to improve soil quality (soil amendment) by enhancing the soil's water retention, nutrient retention, and cation exchange capacity when compared to peat-growing media [129]. Its porous structure creates a habitat for beneficial microorganisms and promotes soil aeration.…”