*6.1.1 Oil recovery*

The oil content in SCG is highly dependent on the coffee variety (**Table 2**). It has been demonstrated that oil extracted from SCG could be used in biodiesel production. Solvent extraction and supercritical fluid extraction with CO2 and ethanol as a solvent

**145**

*6.1.2 Caffeine recovery*

and light-free environment process.

*Composition, ultimate, and proximate analysis of SCG.*

*Revalorization of Coffee Waste*

**Biochemical composition**

Ultimate analysis

Proximate analysis

*\*db: Dry base.*

**Table 2.**

*DOI: http://dx.doi.org/10.5772/intechopen.92303*

have been the methods used for oil recovery. The solvent type (ethanol anhydrous, ethanol hydrous, hexane, and methanol), g SCG/g solvent ratio (20.3–23.8 g/g), extraction time (19.5–30.4 min), and temperature (30°C) were studied. The oil yield obtained varied from 7.5 to 14.7 w/w% d.b. The best oil yield obtained (14.7 w/w% d.b.) was using 22.5 g SCG/g hexane, 30°C, and 30.4 min of extraction time [60, 63, 65].

ww%db\*

**Compound Concentration (wt%db\*)**

Lipids 6.7–19 Carbohydrates 14.1–72.4 Proteins 4.3–17 Mannose 21.2–47 Galactose 25–30 Glucose 19–24 Arabinose 3.8–6 Caffeine 0.96–7.9 Oil 10–20 wt%

Element ww%db\* C 52.1–53 H 6.8–7.03 N 1.71–3.47 S 0.1 O 34.7–38.1

Moisture 11.5–61 Volatile 79.5 Ash 0.68–2.2 Fixed carbon 8.2

Caffeine is an alkaloid, which is the coffee chemical compound most recognized in the world. The content of caffeine in coffee beans is higher than SCG; however, a high quantity remains in SCG. The Soxhlet extraction, ultrasoundassisted extraction, membrane technology, and pressurized liquid membrane with ethanol and water have been the methods used for caffeine recovery. The range of caffeine yield was similar for the different methods, falling in the range from 0.734 to 43 mg/g db [60, 61]. However, the pressurized liquid extraction (PLE) has the advantage of decreasing solvent use and operating time, being an oxygen

*Coffee - Production and Research*

surface area 1279.96 m<sup>2</sup>

acids, fatty acids, and minerals.

polysaccharides, and tannin recovering.

The use of activated carbon derived from SCG was recently reported, and the activation procedure was carried out with ZnCl2. To optimize the activated carbon production, an experimental design was performed; the independent factors were temperature (450 and 600°C), activation time (40 and 120 min), and impregnation ratio (0.5 and 1.5 g ZnCl2/g SCG), and the experimental responses were surface area, yield, and hardness. The optimal conditions were impregnation ratios of 1.5, 600°C, and 40 min. At these conditions, the experimental responses were

produced at these conditions was used to adsorb phenol from aqueous solutions, based on Langmuir isotherm, the maximum adsorption capacity was 160.52 mg/g,

The circular economy demands the efficient utilization of resources in the production systems and the long-term material use by recycling or remanufacturing [59]. This concept can be correctly applied to the product obtained from biomass processing, such as coffee waste. This material could be a feedstock for a monoprocess extraction, bioenergy production, and biorefining. The first stage of the process design is determining the composition of SCG, which has been shown to be highly dependent on coffee varieties [60–62]. The range of the biochemical composition values obtained is shown in **Table 2**. It is important to consider that SCG has a high quantity of organic compounds such as polyphenols, polysaccharides, amino

**6.1 Valuable chemical compound recovery by mono-process extraction**

These techniques use chemicals to extract valuable organic compounds (lipids,

The oil content in SCG is highly dependent on the coffee variety (**Table 2**). It has been demonstrated that oil extracted from SCG could be used in biodiesel production. Solvent extraction and supercritical fluid extraction with CO2 and ethanol as a solvent

polysaccharides, phenolics, tannins, and caffeine), and it could be assisted by ultrasound, enzyme, or microwave. These chemical compounds can be useful to obtain high added value products: biodiesel, cosmetics, food additives, pharmaceuticals, packing materials, and adhesives. These techniques are divided into conventional (Soxhlet extraction, maceration, and hydrodistillation) and nonconventional techniques (supercritical fluid extraction, enzyme-assisted extraction, ultrasound-assisted extraction, microwave-assisted extraction, pulsed electric-assisted extraction, and pressurized liquid extraction). The factors studied in the SCG mono-process extraction have been the coffee varieties, solvent, time, pressure, and temperature. The Soxhlet extraction process has several disadvantages, such as low productivity, high solvent consumption, and high extraction time [63]. Ultimately, the main goal of nonconventional methods is to decrease the utilization of synthetic and organic chemicals and operational condition and to improve the yield and quality of extract, which makes them environmentally friendly compared to conventional techniques [64]. Monoprocess extraction has been used in SCG for oil, caffeine, phenolic compounds,

and the equilibrium was attained less than 150 min [50].

**6. Mono-process extraction, bioenergy, and biorefinery**

/g, yield 26%, and hardness 76.77%. The activated carbon

**144**

*6.1.1 Oil recovery*


### **Table 2.**

*Composition, ultimate, and proximate analysis of SCG.*

have been the methods used for oil recovery. The solvent type (ethanol anhydrous, ethanol hydrous, hexane, and methanol), g SCG/g solvent ratio (20.3–23.8 g/g), extraction time (19.5–30.4 min), and temperature (30°C) were studied. The oil yield obtained varied from 7.5 to 14.7 w/w% d.b. The best oil yield obtained (14.7 w/w% d.b.) was using 22.5 g SCG/g hexane, 30°C, and 30.4 min of extraction time [60, 63, 65].
