Study of optimal conditions in semi-continuous anaerobic co-digestion of table olive effluents and pig manure in a perfectly stirred reactor
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Brines from table olive elaboration were co-digested with pig manure, obtaining high methane productions. In particular, the methane yields obtained for pig manure total solid (TS) initial concentrations of 2%, 7%, 9% (wet basis, wt.) were 106, 213 and 247 mL CH4 gVS-1add, respectively, using mixtures of two types of brine (acid (A) and basic (B)) generated in the elaboration process. Moreover, an experiment with only basic brine was made, using a pig manure TS concentration of 7% wt. In this case, a methane yield of 224 mL CH4 gVS-1add was obtained. The methane production rate was calculated in experiments of 7% pig manure TS concentration and a high kinetic constant of 0.31 d-1 was obtained for the mixture of residual brine. Finally, the effect of Na+ cation concentration was evaluated in the mixture A:B during co-digestion processes with a 7% wt. pig manure TS concentration and inhibition was detected in this process with a [Na+] of 0.56% wt. of the total sample. An energy and economical study on the treatment of these wastewaters by means of anaerobic co-digestion demonstrated a great economic benefit for the producer industry, a reduction in the diesel consumption used to produce its energetic demand and a reduction cost of 3.63 €/m3 generated of A:B brines mixture with ratio 2:1.
KeywordsWastewater Salt concentration Energy study Total solid Methane production Kinetic
This research was carried out as a part of the 0450_AGRI_SOS_6_E 0406 and ALTERCEXA II 4 E: Medidas de adaptación y mitigación al cambio climático a través del impulso de las energías renovables en Centro, Extremadura y Alentejo (Fase II). Projects of the Programme for cross-border cooperation between Spain and Portugal 2007–2013. Also, it was finnanced with the Project PCJ1006 (2011-2015) “Planta integrada para la fijación de CO2 en microalgas y su aprovechamiento en un proceso de co-digestión para la generación de energía térmica y eléctrica” included in the Programme “Cooperation Projects in strategic sectors between researcher groups and industries” of Junta of Extremadura (Spain).
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