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

Andrea Crespo-Barreiro (), Natalia Gómez, Judith González-Arias, Noemí Ortiz-Liébana, Fernando González-Andrés and Jorge Cara-Jiménez
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Andrea Crespo-Barreiro: Chemical, Environmental and Bioprocess Engineering Group, Institute of Environment, Natural Resources and Biodiversity, University of León, Av. Portugal, 41, 24071 León, Spain
Natalia Gómez: Department of Mining, Topographical and Structural Technology, School of Mines, University of Leon, 24071 León, Spain
Judith González-Arias: Chemical, Environmental and Bioprocess Engineering Group, Institute of Environment, Natural Resources and Biodiversity, University of León, Av. Portugal, 41, 24071 León, Spain
Noemí Ortiz-Liébana: Chemical, Environmental and Bioprocess Engineering Group, Institute of Environment, Natural Resources and Biodiversity, University of León, Av. Portugal, 41, 24071 León, Spain
Fernando González-Andrés: Chemical, Environmental and Bioprocess Engineering Group, Institute of Environment, Natural Resources and Biodiversity, University of León, Av. Portugal, 41, 24071 León, Spain
Jorge Cara-Jiménez: Chemical, Environmental and Bioprocess Engineering Group, Institute of Environment, Natural Resources and Biodiversity, University of León, Av. Portugal, 41, 24071 León, Spain

Agriculture, 2023, vol. 13, issue 5, 1-14

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

Keywords: biochar; phytotoxicity; upscaling; polycyclic aromatic hydrocarbons; carbon sink; pyrolysis (search for similar items in EconPapers)
JEL-codes: Q1 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 (search for similar items in EconPapers)
Date: 2023
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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