Scaling-Up of the Production of Biochar from Olive Tree Pruning for Agricultural Use: Evaluation of Biochar Characteristics and Phytotoxicity

Due to the large acreage of olive trees in Mediterranean basin, biochar from tree pruning may become an important resource as part circular economy strategies. However, so far, there is not much knowledge on whether same characteristics are repeated once production up-scaled industrial level. Accordingly, this study aimed scale up with three reactors (semi-pilot, pilot and industrial) ascertain parameters that determine obtained its possible toxicity use agriculture or environmental applications. First, conditions semi-pilot reactor were optimised by testing temperatures (400, 500 600 °C), result °C was optimal temperature because a high carbon content (70.88%), moderate pH (8.1), good sink (R50 > 0.5) low contents PAHs (<6 mg/kg) heavy metals, resulting phytostimulanting effect for all crops studied. Then, upscaled, using pyrolysing temperature. At scale, accurate control essential when above 650 reached, showed 11, severe phytotoxicity. The longer retention time material pyrolysers improved stability and, therefore, biochar’s role sink. Consequently, it proven produce adequate applications large-scale equipment, two most factors needing time.