Use of diluted poultry manure as a low-cost emulsifier for anaerobic digestion of used cooking oil

Abstract

The aim of this study was to evaluate the anaerobic co-digestion of diluted poultry manure (DPM) and used cooking oil (UCO). Mixtures of DPM with different UCO dosages (1 to 6% v/v) were prepared using a high-shear emulsifier and digested in batch anaerobic reactors. Increasing the UCO dosage increased the emulsion COD (from initially 64 to 182 g · L−1) but emulsion stability was affected adversely. UCO at the optimum dosage (1.5 to 2.0% v/v) was further digested in a semi-continuous mesophilic anaerobic reactor, to assess process feasibility at organic loading rates (OLRs) up to 8 g · L−1 · d−1. The reactor was stable, yielding biogas at 0.45 L · g−1 COD, with low supernatant COD (<6 g · L−1), negligible VFA accumulation and no foaming.

Performance of an anaerobic plug-flow reactor treating agro-industrial wastes supplemented with lipids at high organic loading rate

“…The results of this study reveal the potential of the PFR for high-rate anaerobic digestion of complex agro-industrial wastes. Similar biogas yield values were reported for a CSTR treating DPM and UCO; however, at significantly lower OLR (5 to 8 g L −1 d −1 ) compared to the PFR (10 to 15 g L −1 d −1 ) (Eftaxias et al, 2019). Therefore, it is also possible to decrease the required digester volume by implementing a PFR instead of a CSTR design.…”

“…During Period I, DPM was used as the main substrate supplemented with UCO after emulsification pre-treatment, while gradually increasing the UCO dosage every 15 days of reactor operation (from 0.35 ± 0.01 to 0.80 ± 0.11 and 1.11 ± 0.09% v/v). Emulsification pre-treatment was performed according to Eftaxias et al (2019). During Periods II and III, dairy manure was the main substrate supplemented with emulsified animal fat.…”

“…The former is designed with external separation and recirculation of the anaerobic biomass, while the latter implements membrane filtration to retain the anaerobic sludge inside the reactor. Under these conditions the washout of lipids and anaerobic biomass, which is often encountered in conventional CSTR digesters, is minimized or completely avoided, and the applied OLR can be increased up to 8 g L −1 d −1 as demonstrated in previous studies (Dereli et al, 2014; Diez et al, 2012; Eftaxias et al, 2018, 2019; Lienen et al, 2014).…”

Feedstock thermal pretreatment selectively steers process stability during the anaerobic digestion of waste activated sludge

“…One of the most common solution for preventing process failure is anaerobic co-digestion. Codigestion can improve process stability, by (1) diluting potential inhibitory substances, such as ammonia, and (2) optimising the nutrient balance (Eftaxias et al 2019;Mata-Alvarez et al 2011;Mata-Alvarez et al 2000). Nevertheless, process stabilization and optimization remains difficult (Hubenov et al 2015;Kacprzak et al 2010), and the unbalanced availability of suitable feedstocks, due to seasonal variation in supply and geographical reasons, is another problem that hampers an efficient co-digestion process (Hagos et al 2017).…”