The effect of dry olive residue-based biochar on the risk element mobility and nutrient status of the contaminated soil

Bc. Kateřina Vejvodová

Master's thesis

Abstract:

The Mediterranean areas depend on their production of olives and olive oil, with Spain taking the lead in olive oil production. A two-phase extraction system is used which creates a by-product known as “alpeorujo”, which undergoes a second centrifugation to extract any residual oil, creating dry olive residue (DOR) as a waste product. The DOR is rich in mineral and organic matter and phytotoxic compounds (phenolic compounds, organic acids, high molecular mass polyphenols and glycoproteins) that can inhibit growth of microorganisms and plants.A possible way to decrease the phytotoxicity of the waste can be to transform it into biochar via pyrolysis and use it as an amendment for contaminated soils and to improve the nutrient status of soils. DOR from Spain was transformed into biochar at 350°C and 500°C in order to evaluate its effect on the mobility of As, Cd, Pb and Zn and Ca, Mg, P and K availability. A pot experiment was conducted over 3 months to observe the effect of each biochar on three levels of contaminated soil obtained from Přibram (low, medium and high levels of contamination). The biochar was applied at a 2% and 5% application rate. Triticum aestivum was grown in the soils to observe the availability and mobility of the risk elements. The different application rates and pyrolysis temperature were seen to influence the accessibility of the risk and essential elements in soils and Triticum aestivum plants.Soil properties and especially pH was found to statistically affect the bioavailability of risk elements in the soils, however the treatments were less significant. A greater significance was found for the essential elements, where soil, biochar production temperature and plant parts were statistically significant in improving essential element concentrations in plants (p<0.01; p<0.001). The correlation analysis found a positive correlation between the risk elements in soils indicating the similar source of soil contamination. The negative correlations among the risk elements and nutrient levels in plants indicate that the increase in the risk elements has led to the decrease of some of the essential element concentrations in plants.

Keywords

Dry olive residue, risk elements, mobility, nutrient availability, contaminated soil

Language used: English

Date on which the thesis was submitted / produced: 10. 4. 2019

Thesis defence

• Supervisor: prof. Ing. Jiřina Száková, CSc.
• Reader: Mercedes García Sánchez, Bc., externi

Czech University of Life Sciences Prague

Faculty of Agrobiology, Food and Natural Resources

Master programme:
Natural Resources Management and Ecological Engineering