Appropriate conditions for applying NaOH-pretreated two-phase olive milling waste for codigestion with food waste to enhance biogas production.

The high methane gas production potential of two phase olive milling waste (2POMW) makes its application to biogas plants in business an economical process to increase the productivity of the plants. The objective of this study was to investigate the appropriate conditions for the codigestion of NaOH-pretreated 2POMW with food waste. NaOH pretreatment can increase the methane production by increasing the soluble chemical oxygen demand (sCOD), but it may cause inhibition because of higher levels of alkalinity, sodium ion, volatile fatty acids and long chain fatty acids (LCFAs). Therefore, the first experimental phase of this study aimed to investigate the effect of different mixing ratios of 2POMW to food waste. A continuous stirred tank reactor experiment with different mixing ratios of 3%, 4.3%, 5.7% and 8.3% (2POMW: food waste) was conducted. NaOH pretreatment in the range of 6-20% was used. A mixing ratio up to 4.3%, when 10% NaOH pretreatment was used, caused no inhibition and increased methane production by 445.9mL/g-VS(2POMW). For this mixing ratio an additional experimental phase was conducted with the 20% NaOH pretreatment as the 20% NaOH pretreatment had the highest sCOD. The methane gas production was increased by 503.6mL/g-VS(2POMW). However, pH adjustment was required for applying this concentration of the high alkalinity 20% NaOH-pretreated 2POMW. Therefore, we consider using 10% NaOH pretreatment in a mixing ratio of 4.3% to be more applicable. The increase in methane gas production was correlated to the oleic acid concentration inside the reactors. The high oleic acid concentration of 61.8mg/L for the 8.3% mixing ratio was responsible for the strong inhibition. This study showed that adjusting the appropriate mixing ratio of the NaOH-pretreated 2POMW could increase the electricity production of a reactor that regularly receives food waste.

[1]  Michael Niaounakis,et al.  Olive Processing Waste Management: Literature Review and Patent Survey , 2006 .

[2]  J. M. González,et al.  Performance and microbial communities of a continuous stirred tank anaerobic reactor treating two-phases olive mill solid wastes at low organic loading rates. , 2006, Journal of biotechnology.

[3]  Caixia Wan,et al.  Enhanced solid-state anaerobic digestion of corn stover by alkaline pretreatment. , 2010, Bioresource technology.

[4]  I. Angelidaki,et al.  Optimization of biogas production from olive-oil mill wastewater, by codigesting with diluted poultry-manure , 2007 .

[5]  Rafael Borja,et al.  Influence of organic loading rate and hydraulic retention time on the performance, stability and microbial communities of one-stage anaerobic digestion of two-phase olive mill solid residue , 2008 .

[6]  H. Insam,et al.  Mesophilic and thermophilic co-fermentation of cattle excreta and olive mill wastes in pilot anaerobic digesters. , 2010 .

[7]  F. G. Fermoso,et al.  Assessment of two-phase olive mill solid waste and microalgae co-digestion to improve methane production and process kinetics. , 2014, Bioresource technology.

[8]  Rafael Borja,et al.  A study of anaerobic digestibility of two-phases olive mill solid waste (OMSW) at mesophilic temperature , 2002 .

[9]  V. J. Sinanoglou,et al.  Phenolic and antioxidant potential of olive oil mill wastes , 2011 .

[10]  S. Hrudey,et al.  The effects of phenol and some alkyl phenolics on batch anaerobic methanogenesis , 1984 .

[11]  Samir Kumar Khanal,et al.  Anaerobic Biotechnology for Bioenergy Production: Principles and Applications , 2008 .

[12]  Hubertus V. M. Hamelers,et al.  Microbial electrolysis cells for production of methane from CO2: long‐term performance and perspectives , 2012 .

[13]  A Roig,et al.  An overview on olive mill wastes and their valorisation methods. , 2006, Waste management.

[14]  Göksel N. Demirer,et al.  Anaerobic treatment of olive mill wastes in batch reactors , 2000 .

[15]  M. Hamdi.  Toxicity and biodegradability of olive mill wastewaters in batch anaerobic digestion , 1992 .

[16]  Samir Kumar Khanal,et al.  Anaerobic Biotechnology for Bioenergy Production , 2008 .

[17]  Shizhong Li,et al.  Alkaline pretreatment for enhancement of biogas production from banana stem and swine manure by anaerobic codigestion. , 2013, Bioresource technology.

[18]  C. J. Williams,et al.  Anaerobic treatment of olive mill wastewater and piggery effluents fermented with Candida tropicalis. , 2009, Journal of hazardous materials.

[19]  A. E. Greenberg,et al.  Standard methods for the examination of water and wastewater : supplement to the sixteenth edition , 1988 .

[20]  P. Kougias,et al.  Effect of feedstock composition and organic loading rate during the mesophilic co-digestion of olive mill wastewater and swine manure , 2014 .

[21]  Zilin Song,et al.  Anaerobic codigestion of pretreated wheat straw with cattle manure and analysis of the microbial community. , 2015, Bioresource technology.

[22]  S. Otles,et al.  Treatment of Olive Mill Wastewater and the Use of Polyphenols Obtained After Treatment , 2012 .

[23]  J. Lalman,et al.  Anaerobic degradation and methanogenic inhibitory effects of oleic and stearic acids. , 2001, Water research.