Biogas Potential of the Side Streams Obtained in a Novel Phenolic Extraction System from Olive Mill Solid Waste

Abstract

The olive oil production is an important industrial sector in many Mediterranean areas, but it is currently struggled by the necessity of a proper valorisation of the olive mill solid waste or alperujo. The alperujo is the main by-product generated during the two-phase olive oil extraction, accounting for up to 80% of the initial olive mass. The alperujo is a source of valuable compounds, such as the pomace olive oil or highly interesting phenolic compounds. In the present research, a novel biorefinery approach has been used for phenolic compounds recovery. However, the extraction of these valuables compounds generates different exhausted phases with high organic matter content that are required to be managed. This study consists of the evaluation of the anaerobic biodegradability of the different fractions obtained in a novel biorefinery approach for the integral valorisation of alperujo. The results show that the different phases obtained during the biorefinery of the alperujo can be effectively subjected to anaerobic digestion and no inhibition processes were detected. The highest methane yield coefficients were obtained for the phases obtained after a two-months storages, i.e., suspended solids and liquid phase free of suspended solids, which generated 366 ± 7 mL CH4/g VS and 358 ± 6 mL CH4/g VS, respectively. The phenol extraction process reduced the methane yield coefficient around 25% due to the retention of biodegradable compounds during the extraction process. Regardless of this drop, the anaerobic digestion is a suitable technology for the stabilization of the different generated residual phases, whereas the high market price of the extracted phenols can largely compensate the slight decrease in the methane generation.

Towards the Integral Valorization of Olive Pomace‐Derived Biomasses through Biorefinery Strategies

“…In some cases, the integration of operations has been tested on a laboratory scale, while in other cases theoretical approximations have been made. Olive pomace provided phenolic-rich extracts along with fuel gas through pyrolysis [21,135] and anaerobic digestion [136]. Alternatively, Ribeiro et al [67] proposed wet and dry fractionation to recover phenolic compounds, a pulp fraction, and a stone-rich fraction as biofuel.…”

Microbial Population Dynamics during Unstable Operation of a Semicontinuous Anaerobic Digester Fed with a Mild-Treated Olive Mill Solid Waste

“…Among all types of bioprocesses, anaerobic digestion can be highlighted, which allows taking advantage of this source of organic matter, generating methane and a stabilised digestate for agricultural use, i.e., a source of energy and biomass for use in agriculture [6,7]. The extraction of phenolic components during the application of the three-phase extraction system would be favourable for the subsequent anaerobic digestion process due to the toxic effect of these compounds on anaerobic microorganisms, particularly the methanogens [8]. In this sense, the necessity arises to study the use of this technology from the two fractions, liquid and solid, which allows a better use while allowing us to manage the growing volumes of this by-product, generating energy and improving the conditions of exhaustion in the olive plantations themselves.…”

Use of Anthracophyllum discolor and Stereum hirsutum as a Suitable Strategy for Delignification and Phenolic Removal of Olive Mill Solid Waste

“…OMSW is composed of olive husk, olive pulp, and olive vegetation water, resulting in a substrate rich in lignocellulosic fibers and polyphenols [ 23 , 24 ]. Polyphenols in OMSW create a high antimicrobial activity that can hamper the valorization of this biomass through microbe-mediated processes [ 25 ]. In this context, few studies have described the use of WRF for the pretreatment and further valorization of OMSW.…”