Valorisation of waste materials using pyrolysis

Chhiengputheavy Chhorth

Diplomová práce

Abstract:

The environment is threatened by the overuse of synthetic pesticides and fertilizers. Nonetheless, variety of waste materials such as biomass ash (BA), sewage sludge (SS), plant residues, and by-products such as flue gas desulfurization gypsum (FGDG), and phosphogypsum (PG) are capable of being valorized and restoring plant nutrients. The use of these materials on agricultural land is fraught with danger due to the potential presence of hazardous substances like heavy metals, pathogens, organic and inorganic compounds, and pharmaceuticals that could endanger the environment. This experiment involved co-pyrolyzing a mixed sample of feedstock material in different proportions and were labeled as TA (SS+BA+FGDG), TB (SS+BA+FGDG+PG), and TD (SS+BA+PG). The pyrolysis was carried out at two different temperatures 500°C and 900°C, with the focus on producing an innovative recycled PSK-fertilizer product. The study evaluated the total and available content of specific group of elements, including potential toxic elements (As, Cd, Cr, Pb), macronutrients (Ca, K, Mg, P, S), and micronutrients (Cu, Fe, Mn, Ni, Zn), to determine the impact of co-pyrolysis treatment. Additionally, pH content and biochar yield were also measured. The biochar yield and the pH level of the biochar was influenced by increasing the temperature. At 500°C, the pH value was 9, but it increased to between 11 and 12 at 900°C. The biochar yield decreased as the temperature increased to 900°C, TA exhibited the greatest biochar yield at 500°C (71%) and at 900°C (47%). The total and available content of potential toxic elements was influenced by increased temperatures, the total content was lower at 500°C for As and Cr (19 mg/kg and 45 mg/kg, respectively). The availability of potential toxic elements was observed to decrease with pyrolytic temperature especially for As. For instance, the available content of As was found to be below limit of detection for all co-pyrolysis mixtures at 900°C. The temperature had an influence on other elements such as Cd and Cr causing them to decrease as well at 900°C. On the other hand, the total content of P was increased with temperature, reaching a maximum value of 56 g/kg in TD at 900°C. The highest total content of K and S were also reported to be higher in 900°C (84 g/kg and 95 g/kg) respectively. Conversely, the available content of P, K, and S was higher at 500°C, with 4.9 g/kg for P, 70 g/kg for K and 64 g/kg for S in the co-pyrolytic mixture TA. In contrast, the available content of feedstocks exhibited a decrease value of Ca, K, P, S, and Zn as the temperature increased. However, Cu and Ni remained below limit of detection at 900°C. This investigation demonstrated that the co-pyrolytic mixture and temperature increase during pyrolysis has influenced the content of both total content and availability content of the elements.

Keywords

Co-pyrolysis, Sewage sludge, Biomass ash, Phosphogypsum, Flue gas desulfurization gypsum

Jazyk práce: angličtina

Datum vytvoření / odevzdání či podání práce: 21. 4. 2024

Obhajoba závěrečné práce

• Obhajoba proběhla 23. 5. 2024
• Vedoucí: Ing. Filip Mercl, Ph.D.
• Oponent: Hynek Roubík, Ph.D.

Česká zemědělská univerzita v Praze

Fakulta agrobiologie, potravinových a přírodních zdrojů

Magisterský studijní program:
Natural Resources and Environment