Combination of Dry Milling and Separation Processes with Anaerobic Digestion of Olive Mill Solid Waste: Methane Production and Energy Efficiency

Abstract

This experimental work aims at investigating the effects of milling; sieving; and electrostatic separation on the biochemical methane potential of two olive pomaces from traditional olive oil extraction (M) and from a three-phase system (T). Sieving proved to be efficient for increasing the soluble chemical oxygen demand in the smallest fractions of the sieve of both M (62%) and T (78%) samples. The positive fraction following electrostatic separation also enhanced chemical oxygen demand (COD) solubilisation by 94%, in comparison to sample T milled at 4 mm. Sieve fractions with a size greater than 0.9 mm contained 33% and 47% less lipids for the M and T biomasses; respectively. Dry fractionation modified sample properties as well as lipid and fiber distribution. Concomitantly; milling increased the accessibility and facilitated the release of organic matter. The energy balance was positive after knife milling and sieving; while ball milling and ultrafine milling proved to be inefficient.

Methane production by anaerobic co‐digestion of dairy manure and cassava wastes for energy recovery

“…The phenolic compounds were quantified by spectrophotometry according to the modified Folin-Ciocalteu method, using acetone 70% (v/v) in the extraction step. 14 The pH was measured using a digital pH meter (model mPA-210, MS-TECNOPON).…”

“…The quantification of extractives in CB and DM was conducted according to TAPPI (Technical Association of the Pulp and Paper Industry) T204 cm‐07 method, by a modified Soxhlet extraction, which employed cyclohexane instead of benzene and ethanol (50:50, v/v). The phenolic compounds were quantified by spectrophotometry according to the modified Folin–Ciocalteu method, using acetone 70% (v/v) in the extraction step 14 . The pH was measured using a digital pH meter (model mPA‐210, MS‐TECNOPON).…”

Biogas Production from Arthrospira platensis Biomass

“…According to Spínola et al [58], the biomass of A. platensis contains up to 76% protein, whereas the chemical analyses Another important factor is the protein content of the biomass, which affects the C/N ratio. For microalgae, this value ranges from 4.16 to 10 [54], while the optimum value for anaerobic fermentation is 20 to 35 [55]. A low C/N ratio can negatively affect the digestion process and lead to the release of significant amounts of ammonium nitrogen and the accumulation of volatile fatty acids [56].…”

The utilisation solutions of olive mill by‐products in the terms of sustainable olive oil production: a review

“…However, novel scientific researchers are mainly focused on the improvement of the methods for the conversion of olive pomace into liquid (biofuel) or solid (pellets) biofuel, which incorporates more value into the production cycle (Berbel & Posadillo, 2018). Anaerobic digestion of olive pomace can be used as an environmentally friendly method for biofuel production that provides good waste stabilisation and high energy recovery (Serrano et al ., 2017; Elalami et al ., 2018). The olive pomace phenolic content can inhibit the biomethanisation process during anaerobic digestion.…”

“…Same as olive pomace, OMSW has been considered as an important source of energy (Christoforou & Fokaides, 2016), frequently in the anaerobic digestion process for biogas production (Elalami et al ., 2018). In recent years, most of the papers have considered the utilisation as a feedstock in bioethanol production through anaerobic fermentation due to its high cellulose and hemicellulose content (Manzanares et al ., 2017; Abu Tayeh et al ., 2020).…”