Effect of pH, substrate loading, oxygen, and methanogens inhibitors on volatile fatty acid (VFA) production from citrus waste by anaerobic digestion

• Published in: Bioresource technology Vol. 302; p. 122800
• Main Authors: Eryildiz, Bahriye, Lukitawesa, Taherzadeh, Mohammad J.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.04.2020
• Subjects: 2-bromoethanesulfonate (BES); acetic acid; acidification; Anaerobic digestion; Anaerobic digestion, citrus waste; Anaerobiosis; Bioreactors; butyric acid; Citrus; citrus peels; citrus waste; Fatty Acids, Volatile; gas production (biological); hexanoic acid; Hydrogen-Ion Concentration; inoculum; Inoculum to substrate ratio; Inoculum to substrate ratio2-bromoethanesulfonate (BES); juices; lipid content; Methane; methane production; methanogens; Oxygen; Resource Recovery; Resursåtervinning; toxicity; Volatile fatty acids; wastes; Inoculum to substrate ratio; 2-bromoethanesulfonate (BES); Oxygen; Anaerobic digestion, citrus waste; Volatile fatty acids
• ISSN: 0960-8524; 1873-2976; 1873-2976
• DOI: 10.1016/j.biortech.2020.122800

[Display omitted] •Acidogenesis of citrus waste was better at controlled pH 6 at low substrate loading.•Addition of inhibitor for methanogens did not significantly increase VFA yield.•The presence of initial O2 did not negatively impact the VFA yield.•D-Limonene and peel oil also can also inhibit acidification of citrus waste. Citrus waste from e.g., juice production is a potential substrate for anaerobic digestion (AD). However, due to the toxic citrus peel oil content, citrus waste has several challenges in biogas production. Hence, volatile fatty acids (VFAs) are very interesting intermediate products of AD. This paper was aimed to investigate VFA production from citrus wastes by boosting its production and inhibiting methane formation. Therefore, the effects of inoculum to substrate ratio (ISR), O2 presence, pH, and inhibitor for methanogens, in VFA production from citrus waste through acidification process were studied. The addition of 2 g/L methanogens inhibitor and the presence of O2 in the reactors were able to reduce methane production. The highest yield of VFA (0.793 g VFA/g VSadded) was achieved at controlled pH at 6 and low substrate loading (ISR 1:1). Acetic acid (32%), caproic acid (21%), and butyric acid (15%) dominate the VFA composition in this condition.