Abstract
This work presents a comparative study of the physicochemical properties of chars derived by three thermochemical pathways, namely: hydrothermal carbonization, HTC (at 180, 200 and 220 °C), pyrolysis, PY, (at 500, 600 and 700 °C) and microwave assisted pyrolysis, MW (at 300, 450 and 600 W). The mass yield of HTC samples showed a decrease (78.7 to 26.7%) as the HTC temperature increased from 180 to 220 °C. A similar decreasing trend in the mass yield was also observed after PY (28.45 to 26.67%) and MW (56.45 to 22.44%) of the food waste mixture from 500 to 700 °C and 300 to 600 W, respectively. The calorific value analysis shows that the best among the chars prepared by three different heating methods may be ranked according to the decreasing value of the heating value as: PY500, MW300, and HTC180. Similarly, a decreasing trend in H/C values was observed as: PY500 (0.887), MW300 (0.306), and HTC180 (0.013). The scanning electron microscope (SEM) analyses revealed that the structure of the three chars was distinct due to the different temperature gradients provided by the thermochemical processes. The results clearly show that the suitable temperature for the HTC and PY of food waste was 180 °C and 500 °C, respectively, while the suitable power for the MW of food waste was 300 W.
Highlights
Accepted: 16 February 2022Global food wastage continues to grow in alarming proportions, and this is not without far-reaching consequences for the environment [1]
A similar decreasing trend in the mass yield was observed after PY (28.45–26.67%) and microwave assisted pyrolysis (MW) (56.45 to 22.44%) of the food waste mixture from 500 to 700 ◦ C and 300 to 600 W, respectively
The yield of the char produced via hydrothermal carbonization (HTC) at 180 ◦ C was higher than the yield obtained via PY and MW at 500 ◦ C
Summary
Accepted: 16 February 2022Global food wastage continues to grow in alarming proportions, and this is not without far-reaching consequences for the environment [1]. Organization, the annual tonnage of wasted food worldwide is around 1.3 billion with roughly 45 to 80% of this waste discarded in landfills [2]. Despite being discarded, this food waste (which is usually processed through energy intensive processes), if properly harnessed, can serve as a valuable resource. Owing to food waste’s rich organic and energy contents, research efforts are being harnessed towards its possible conversion to value-added products such as char instead of being dumped in landfills [5,6]. On a w/w basis, food waste contains ≤33.2 of lipids,
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