Abstract
Macadamia nut shell (MNS) is a type of waste lignocellulose obtained from macadamia nut production processing. Large MNS wastes caused serious resource waste and environmental pollution. So, preparation of hydrochars from MNS via hydrothermal carbonization (HTC) is of great significance. HTC of MNS was conducted to study the effect of process parameters, including HTC temperature (180–260°C) and residence time (60–180 min) on the properties of hydrochars. Results showed that the increase in HTC temperature and residence time decreased the mass yield of hydrochars and increased the high heating value of hydrochars. Furthermore, the C content of hydrochars increased, whereas the H and O contents decreased. Mass yield of hydrochar is 46.59%, energy yield is 64.55% and the higher heating value is 26.02 MJ kg−1 at a temperature of 260°C and time of 120 min. The surface structure of hydrochars was rougher compared with that of MNS as observed via scanning electron microscopy. The chemical and combustion behaviour of MNS and hydrochars was analysed by Fourier transform infrared spectroscopy, and thermogravimetric analysis indicated that decarboxylation and dehydration reactions were the predominant pathways during the HTC process. Results showed that HTC can facilitate the transformation of MNS into solid fuel.
Highlights
Energy demand continues to increase with the growth of the world population [1,2]
Macadamia nut shell (MNS) is a type of waste lignocellulose obtained from macadamia nut production processing
The chemical and combustion behaviour of MNS and hydrochars was analysed by Fourier transform infrared spectroscopy, and thermogravimetric analysis indicated that decarboxylation and dehydration reactions were the predominant pathways during the hydrothermal carbonization (HTC) process
Summary
Energy demand continues to increase with the growth of the world population [1,2]. the demand for energy in industrialization and urbanization leads to severe energy shortage and environmental pollution [3,4,5]. The comprehensive utilization of MNS is an important issue to be solved in the development of the macadamia nut industry. The use of MNS has been investigated and explored in various approaches. Zheng et al [10] explored a new method to produce a high-performance sodium-ion battery enhanced by MNS-derived hard carbon anode. Rodrigues et al [11] produced activated carbon-derived MNS for potential use as an adsorbent for phenol removal. Li et al [12] investigated nitrogen-doped activated carbon from MNS and its application in supercapacitors. Studies on the energy utilization of MNS are rarely reported. In these respects, a related study has been conducted [13,14]. The results show that prepared biochar from MNS offers an important application prospect
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