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Ecofuel conversion technology of inedible lipid feedstocks to renewable fuel  245


            Table 9.4 Chemical composition range of dried spent coffee ground

            Chemical component        Range (wt%)           Reference
            Moisture                  5.0–10.0              [28, 52, 53]
            Lipid                     2.29–18.3             [28, 54]
            Protein                   1.02–17.4             [28, 52]
            Ash                       1.3–1.6               [28, 54]
            Carbohydrate              45.3–75.4             [28, 54]
            Cellulose                 8.6–12.4              [28, 54]
            Hemicellulose             36.7–39.1             [28, 54]
            Lignin                    23.9–29.8             [28, 55, 56]



           chemical constituents of dried spent coffee grounds compiled from various studies are
           presented in Table 9.4.
              Although spent coffee grounds are the waste sourced from human culture, spent
           coffee is not inherently safe for direct disposal. Fernandes et al. reported the latent
           danger of mutation and the cytotoxic effect of spent coffee ground waste leached
           extract toward aquatic plankton [57]. The leaching extract of spent coffee grounds
           contains a considerable amount of antioxidant compounds that can consume dissolved
           oxygen in water. Utilization of spent coffee grounds as cattle feed or plant fertilizer
           has been assessed to be ineffective. Plant growth inhibition, particularly during root
           elongation, was reported due to the presence of fatty acids that formed an inhibition
           layer for nutrients and oxygen absorption [58]. Composting of spent coffee grounds
           was slow due to the lack of mobile ions for the growth of composting bacteria in addi-
           tion to the slight antibacterial effect that was indicated by fewer bacteria present with
           comparison to the control system [59]. On the other hand, Givens and Barber spotted
           the low digestibility of spent coffee waste in sheep, deeming it a worthless ruminant
           feedstuff [60]. The analysis showed that spent coffee grounds had quite a high content
           of fiber, as reflected by the number of acid detergent fibers, yet the fact of the indi-
           gestibility of spent coffee grounds implied more on the high content of recalcitrant
           lignin bound with cellulosic fiber. Moreover, protein as the other valuable component
           for animal feed can actually be so low since the measurement of protein that is based
           on the nitrogen content, cannot distinguish between the nitrogen from amino acid and
           nonprotein nitrogen such as caffeine and melanoidins (nitrogenous brown-colored
           compounds of coffee from the Maillard reaction) [61].

           9.3   Biodiesel conversion technology

           9.3.1 Catalytic and noncatalytic biodiesel conversion
                  of rice bran/RBO
           Biodiesel can be produced catalytically or noncatalytically. The three types of cata-
           lysts commonly used are acid, base, and enzyme. Each type of catalyst has some
           advantages and some drawbacks for biodiesel conversion. Furthermore, those
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