Correlations between the Composition of Liquid Fraction of Full-Scale Digestates and Process Conditions

Fast development of centralized agricultural biogas plants leads to high amounts of digestate production. The treatment and disposal of liquid fractions after on-site digestate solid–liquid separation remains problematic due to their high organic, nutrient and aromatic contents. This work aims to study the variability of the remaining compounds in the digestate liquid fractions in relation to substrate origin, process parameters and solid–liquid separation techniques. Twenty-nine digestates from full-scale codigestion biogas plants and one waste activated sludge (WAS) digestate were collected and characterized. This study highlighted the combined effect of the solid–liquid separation process and the anaerobic digestion feedstock on the characteristics of liquid fractions of digestates. Two major clusters were found: (1) liquid fractions from high efficiency separation process equipment (e.g., centrifuge and others with addition of coagulant, flocculent or polymer) and (2) liquid fractions from low efficiency separation processes (e.g., screw press, vibrating screen and rotary drum), in this latter case, the concentration of chemical oxygen demand (COD) was associated with the proportion of cow manure and energy crops at biogas plant input. Finally, SUVA254, an indicator for aromatic molecule content and the stabilization of organic matter, was associated with the hydraulic retention time (HRT).

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Detailed monitoring of two biogas plants and mechanical solid–liquid separation of fermentation residues

Journal of Biotechnology ◽

10.1016/j.jbiotec.2009.01.016 ◽

2009 ◽

Vol 142 (1) ◽

pp. 56-63 ◽

Cited By ~ 66

Author(s):

Alexander Bauer ◽

Herwig Mayr ◽

Katharina Hopfner-Sixt ◽

Thomas Amon

Keyword(s):

Liquid Separation ◽

Biogas Plants ◽

Solid Liquid ◽

Solid Liquid Separation

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Enhancing Bioenergy Yields from Sequential Bioethanol and Biomethane Production by Means of Solid–Liquid Separation of the Substrates

Energies ◽

10.3390/en12193683 ◽

2019 ◽

Vol 12 (19) ◽

pp. 3683 ◽

Cited By ~ 1

Author(s):

Lisandra Rocha-Meneses ◽

Jorge A Ferreira ◽

Nemailla Bonturi ◽

Kaja Orupõld ◽

Timo Kikas

Keyword(s):

Flue Gas ◽

Cost Effective ◽

Separation Process ◽

Energy Output ◽

Bioethanol Production ◽

Liquid Separation ◽

Lignocellulosic Feedstock ◽

Transportation Sector ◽

Solid Liquid ◽

Solid Liquid Separation

The production of second-generation ethanol using lignocellulosic feedstock is crucial in order to be able to meet the increasing fuel demands by the transportation sector. However, the technology still needs to overcome several bottlenecks before feasible commercialization can be realized. These include, for example, the development of cost-effective and environmentally friendly pretreatment strategies and valorization of the sidestream that is obtained following ethanol distillation. This work uses two chemical-free pretreatment methods—nitrogen explosive decompression (NED) and synthetic flue gas explosive decompression—to investigate the potential of a bioethanol production sidestream in terms of further anaerobic digestion. For this purpose, samples from different stages of the bioethanol production process (pretreatment, hydrolysis, and fermentation) and the bioethanol sidestream went through a separation process (involving solid–liquid separation), following which a biomethane potential (BMP) assay was carried out. The results show that both factors being studied in this article (involving the pretreatment method and the separation process) served to influence methane yields. Liquid fractions that were obtained during the process with NED gave rise to methane yields that were 8% to 12% higher than when synthetic flue gas was used; fermented and distillation sidestream gave rise to the highest methane yields (0.53 and 0.58 mol CH4/100 g respectively). The methane yields from the liquid fractions were between 60–88% lower than those that were obtained from solid fractions. Samples from the bioethanol sidestream (solid fraction) that were pretreated with NED had the highest methane yield (1.7 mol CH4/100 g). A solid–liquid separation step can be a promising strategy when it comes to improving the energy output from lignocellulosic biomass and the management of the ethanol distillation sidestream.

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