Marble sludges as environmentally friendly catalyst in olive pomace pyrolysis: Effect of sludge composition on pyrolysis product distribution and biochars

Abstract

Waste management of olive pomace is difficult because of the high production amount and nonbiodegradable organic substances. Catalytic pyrolysis process is one of the effective methods for olive pomace (OP) management and for obtaining valuable organic substances from it. Therefore, in this study, different types of marble sludge were used as catalyst in the olive pomace pyrolysis process at 500 °C temperature and 40% catalyst dose. While K1, K2, K3 are the sludges obtained from physicochemical treatment of travertine type marble processing wastewater with alum, FeCl3 and PEL, respectively, K4,K5 and K6 are the corresponding physicochemical treatment sludges of natural stone type marble processing wastewater. Pyrolysis product yields and characteristics of pyrolysis biochars were investigated. The highest product yield for biochar liquid and gas fractions was obtained with the K1 catalyst. The biochar obtained for OP+K1 pyrolysis has the highest initial decomposition temperature. Biochar obtained by using K6 was more granular. Biochar having the highest calorific value (1193 cal/g) was obtained with the catalytic pyrolysis of OP with K4 catalyst. Biochars obtained with the K1 and K6 catalysts have similar calorific values. Besides calorific values, the characteristics of biochars indicated that these biochars can be used for diverse purposes either as additive or feedstock. Consequently, K1 catalyst can be recommended for olive pomace catalytic pyrolysis when biochars are evaluated in terms of product yield and biochar characteristics. © 2023 The authors.