Marble Sludges as Environmentally Friendly Catalysts in Olive Pomace Pyrolysis: Effect of Sludge Composition on Pyrolysis Products

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 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. Pyrolysis product yields and characteristics of pyrolysis biochars were investigated. The highest product yield for biochar liquid and gas fractions was obtained with the catalyst (K1) that is the sludge obtained from physicochemical treatment of travertine type marble processing wastewater with alum. The biochar obtained for OP-K1 pyrolysis has the highest initial decomposition temperature. Biochar obtained by using K6 catalyst (physicochemical treatment sludge of natural stone type marble processing wastewater with PEL) had a more granular distribution. Biochar having the highest calorific value (1193 cal/g) was obtained with the catalytic pyrolysis of olive pomace with the marble sludge obtained from physicochemical treatment of natural stone type marble processing wastewater with alum catalyst (K4). Biochars obtained with the K1 and K6 catalysts has similar calorific values. Besides calorific values, the characteristics of biochars indicated that these biochars can be used 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.