Continuous Anaerobic Co-Digestion of Biowaste with Crude Glycerol under Mesophilic Conditions

Abstract

A persistent topic of the anaerobic digestion of biowaste is the efficient use of co-substrates. According to Renewable Energy Sources Act the co-substrate input is limited to 10 percent of the average daily substrate feed in Germany. In this concern, the primary focus of this paper is to understand the suitability of crude glycerol in anaerobic digestion of biowaste. Two identical lab-scale anaerobic digester units were added with crude glycerol, and each unit was equipped with four identical fermenters. Unit A was fed with an average organic loading rate of 4.5 kg VS m−3 d−1, and the average organic loading rate of unit B was set at 5.5 kg VS m−3 d−1. The share of crude glycerol in the total feed was 0.77 percent of the fresh matter. The abort criterion is a ratio of the volatile organic acids and buffer capacity (FOS/TAC) in the fermenter above 1.2. The abort criterion was reached after 16 days. In summary, the results lead us to the conclusion crude glycerol is not suitable as a co-substrate for anaerobic digestion for several reasons.

Optimization of the Biomethane Production Process by Anaerobic Digestion of Wheat Straw Using Chemical Pretreatments Coupled with Ultrasonic Disintegration

“…However, WS is used as livestock feed, discarded carelessly, or burnt in an open field which involves serious environmental problems [5]. WS can be effectively treated by anaerobic digestion, which is one of the most promising technologies for converting biomass into biogas [6]. However, since the lignocellulosic material in WS is resistant to microbial attack, the AD process is significantly slowed down [7].…”

Optimization of the Process of Methane Production From Wheat Straw and Bovine Manure Co-Digestion by Ultrasound Disintegration and Physicochemical Treatments

“…The delignification of WS with a low concentration of H2O2 4% w/w was promoted due to the production of the HOO − anion, which in turn promoted the production of hydroxyl ( • OH) and superoxide (O2 − ) radicals. Similarly, the promotion of radicals with ultrasound enhanced solubilized lignin degradation [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17].…”

“…However, this latter is used as livestock feed, discarded carelessly, or burnt in an open field which involves serious environmental problems [3]. WS can be effectively treated by AD which is one of the most promising technologies with the potential to convert various biomasses to biogas [4]. However, the lignocellulosic material contained in the WS being resistant to microbial attacks, the AD process is considerably slowed down [5].…”

“…The impact of different pretreatment methods on biomass degradability is extremely different and mostly depends on the feedstock characteristics [6][7]. Several biomass pretreatments have been studied such as grinding [8], ultrasound [9][10], chemical processes [3-11-12], biological technique [13][14] and thermal methods [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15].…”

Energy Balance of Turbocharged Engines Operating in a WWTP with Thermal Hydrolysis. Co-Digestion Provides the Full Plant Energy Demand

“…This improvement in reactor capacity allows the treatment of co-substrates with high methane potential, thus producing more biogas to be valorized in the existent engines. High-strength organics considered suitable co-substrates include waste cooking oil, residual glycerin, or cheese whey from the food industry [49][50][51][52][53][54]. The organic fraction of municipal solid wastes has been extensively studied as co-substrate [55][56][57], but it has the risk of increasing the amount of inert material [58], deteriorating sludge agronomic quality.…”