Enhanced biomethane production by co-digestion of mixed sewage sludge and dephenolised two-phase olive pomace

Abstract

In this study, co-digestion of mixed sewage sludge from a wastewater treatment plant (WWTP) and partially dephenolised two-phase olive pomace (DOP) as a co-substrate was addressed with the aim of improving the biodigestibility of both substrates. The introduction of DOP into WWTP anaerobic digester facilities could significantly increase biomethane production and enhance the sustainability of both activities. An improvement in the system’s performance was supported by stability parameters: total alkalinity increased and stabilised with the addition of 5% v/v DOP, and the specific energy loading rate was maintained at 0.177 ± 0.03 d−1, which indicated better buffer capacity and stability in the bioreactor, and the possibility of enhancing the organic loading rate. In terms of average daily biogas production rate, an increase of 39% was achieved, up to 0.39 ± 0.11 L L−1d−1. Moreover, there was a 40% and 37% improvement in specific methane production and methane production rate, respectively, up to 0.28 ± 0.02 L CH4 g TVS−1 and 0.26 ± 0.08 L L−1d−1. In addition, the proposed strategy leads to an energy saving of 20,328.6 kWh year−1 at the WWTP as a result of the electric energy production surplus, corresponding to an annual saving of €3293.23.

Cold-pressed fruit and vegetable juice pomaces: decision making about their suitability for anaerobic digestion

“…This strategy has been applied in previous studies showing that co-digestion of agro-industrial biowaste with substrates with a low C/N improves the methane yield; for example, incorporation of only 5% olive pomace increased the specific methane yield by 40%. 90…”

“…This strategy has been applied in previous studies showing that co-digestion of agro-industrial biowaste with substrates with a low C/N improves the methane yield; for example, incorporation of only 5% olive pomace increased the specic methane yield by 40%. 90 Route B -AD of pomace pulps (FVPP). Table 7 presents the BMP th predicted based on physicochemical characterization of the different FVPP (Table 5).…”

Anaerobic Digestion of Organic Solid Waste: Challenges Derived from Changes in the Feedstock

“…Microbial growth and activity strongly depend on the environmental pH [19][20][21]. According to literature, methane producers are most active at a neutral pH, i.e.…”

“…The SELR is defined as the quotient between the daily feed organic load (expressed in g of tCOD (L•d) −1 ) and the active biomass inside the digester (expressed in g VSS L −1 ) (VSS, volatile suspended solids) (Eq. ( 1)) and can be considered as an indicator of food to mass ratio (F/M) [19]. Thus, if the food mass in the feedstock exceeds the mass of decomposer microorganisms, it could cause a metabolic imbalance because of the acidification and inhibition of methanogenic microorganisms [36].…”

A mini-review of biomethane valorization: Managerial and policy implications for a circular resource

“…In detail, bioeconomy is defined as a paradigm capable to convert renewable energy resources (RES) biologically deriving from the land and sea – animals (Silva et al, 2020), water (Hildebrandt and Bezama, 2018), crops and agrowaste (Moustakas et al, 2020), forests, etc. – to energy (Fragoso et al, 2021), food (Ragossnig and Ragossnig, 2021) and materials (Lekkas et al, 2021). Several industries are exploiting the results of such paradigm: from agriculture, forestry, fishing and aquaculture, through manufacture of food, beverages, tobacco, bio-based textiles, wood products and furniture, paper, bio-based chemicals, up to manufacture and production of pharmaceuticals, plastics and rubber, liquid biofuels and bioelectricity (European Commission, 2018).…”