Valorization of Waste From Agro-Industry Using Thermo-Chemical Treatments

Abstract

The increasing generation of solid waste and the interest in renewable and alternative energies has become goals in recent years. The objective of this work was to apply thermochemical conversion processes such as pyrolysis, and hydrothermal conversion (HTC and HTL) into waste from the industry such as the coffee husk (CH), and orange peel (OP) in order to determine their performance towards the production of biocarbon, distribution of organic liquid products, as well as characterization of the bio carbon, obtained. Pyrolysis treatments were carried out with a rapid heating ramp up to 500°C, HTC at 250C, and HTL at 280C for 4 hours in triplicates for each biomass. The highest bio carbon yield for OP was obtained by HTC with 36% w/w and for CH the pyrolysis with 40% w/w. The biocarbon obtained from the OP by pyrolysis has a high potential as fuel with a higher heating value (HHV) of 26,3 MJ/kg. On the other hand, in the CH processed by HTC and HTL reported HHV values of 23 MJ/kg. The processing by HTC and HTL favours the formation of biocarbon with high iodine and methylene blue (MB) indices compared to a commercial carbon, for the OP the values obtained are: 343 and 416 mg I2/g, and 174 and 188 mg MB/g whereas for CH 432 and 427 mg I2/g, and 264 and 173 mg AM/g. In relation to liquid organic products, the processing of OP induces the formation of organic compound fractions in the gasoline and diesel range (GRO+DRO) with values between 75-78% when the heat treatments are employed. For the CH, the highest fraction of GRO+DRO was obtained from the pyrolysis with 81%. The HTC obtained the lowest sulphur content for both processed biomass, where the values did not exceed 0.066% w/w.

Detection of adulterated coffee by fourier-transform infrared (FTIR) spectroscopy associated with sensory analysis

“…The coffee-husk samples exhibited lower absorbance values in the spectrum as the percentage of adulteration increased (Figure 3c); however, no strange peaks were present in the coffee spectrum. This may be because of the presence of some compounds, such as CGA, in low concentrations, which, as discussed above, have strong absorption at 1,450 cm -1 and 1,000 cm -1 (Strubinger et al, 2017).…”

“…Similar effects were observed in the coffee-husk samples (Figure 3c). This region showed peaks in the IR spectrum (Figure 1) of the coffee-husk and coffee-corn samples, which were due to the skeletal vibration of the glycosidic bonds in the starch (Strubinger et al, 2017). For the samples adulterated with beans (Figure 3b), an incidence in the wavenumbers 1,635 cm -1 , 1,533 cm -1 , and 1,245 cm -1 were evidenced, related to the amine groups (Alonso et al, 2008;Plans et al, 2013); the incidence was higher in beans due to their protein content.…”

“…For example, the major sawdust compounds, such as cellulose, lignin, and hemicellulose (Phonphuak;Chindaprasirt, 2015), can generate volatile compounds of interest at temperatures above 300 °C (Zhao; Jiang; Chen, 2017), i.e., temperatures far above that of this study. In the case of coffee husk, it shares some compounds similar to coffee but in a smaller proportion, such as CGA, caffeine, and trigonelline (Oliveira et al, 2018;Strubinger et al, 2017). The beans and corn have a higher content of carbohydrates and proteins, which are important precursors of flavors and aromatic compounds; this explains their greater impact on the sensory attributes of samples adulterated with these two types of grains.…”