Anaerobic digestion: an engineered biological process

Ometto, Francesco; Karlsson, Anna; Ejlertsson, Jörgen; Björn, Annika; Shakeri, Sepehr Yekta

doi:10.1016/b978-0-12-815554-7.00005-2

Cited by 5 publications

(9 citation statements)

References 53 publications

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“…Incineration and anaerobic digestion (AD) are two viable ways to produce energy from biomass, whereas the latter process is preferred to manage biodegradable residues with high moisture content. Besides, AD is an environmentally friendly (it occurs in nature) and cost-effective technology in terms of operational costs [5,6]. In practice, AD is a complex biological process that converts, in the absence of external electron acceptors (e.g., oxygen), organic matter into a value-added product, biogas.…”

Section: Introductionmentioning

confidence: 99%

“…This gaseous mixture is mainly composed of methane (60-70%) and carbon dioxide (20-30%). In minor quantities, biogas also presents trace elements from the respiration of the microorganisms [6]. In addition to the energetic gas mixture, anaerobic digestion reduces the volume of substrates and may eliminate the pathogen microorganisms present in the reactional mixture.…”

Section: Introductionmentioning

confidence: 99%

“…In addition to the energetic gas mixture, anaerobic digestion reduces the volume of substrates and may eliminate the pathogen microorganisms present in the reactional mixture. This process occurs in four stages: hydrolysis, acidogenesis, acetogenesis, and methanogenesis, involving a wide number of biochemical transformations and different enzymes [6]. Hydrolysis is considered the rate-limiting step, so pre-treatments can be implemented to make the organic matter more accessible to microorganisms [6,7].…”

Section: Introductionmentioning

confidence: 99%

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Bioenergy Production through Mono and Co-Digestion of Tomato Residues

et al. 2021

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The agro-industry of tomato generates three types of residues: ripe rotten tomato (unfit for consumption) (RT), green (unripe) tomato (GT), and tomato branches including leaves and stems (TB). These materials are commonly wasted or used as feed for livestock. Energy production through anaerobic digestion is an alternative way to manage and simultaneously valorise these materials. Initially, the operating conditions of mono anaerobic digestion were investigated using RT. Thus, a design of experiments based on a two-level fractional factorial design with resolution V was performed to determine the factors that affect biochemical methane potential (BMP). The substrate to inoculum ratio (SIR), total volatile solids concentration (VSt), working volume (WV), presence of nutrients (Nu), and the pre-incubation of the inoculum (Inc) were investigated. The results showed that SIR is the most important factor. The maximum BMP for RT was 297 NmLCH4/gVS with SIR = 0.5; tVS = 20 g/L; WV = 20%; no pre-incubation and the presence of nutrients. Using these optimum operating conditions, co-digestion was investigated through a mixture design approach. The substrates RT and GT presented similar BMP values, whereas TB led to a significantly lower BMP. Indeed, when high concentrations of TB were used, a significant decrease in methane production was observed. Nonetheless, the highest BMP was achieved with a mixture of 63% RT + 20% GT + 17% TB, with a production of 324 NmLCH4/gVS, corresponding to a synergetic co-digestion performance index of about 1.20. In general, although the substrate RT generates the highest BMP, the mixture with GT did not impair the methane yield. Overall, the co-digestion of tomato residues must be conducted with SIR close to 0.5 and the content of tomato branches in the reaction mixture should be kept low (up to 20%).

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Bioenergy Production through Mono and Co-Digestion of Tomato Residues

et al. 2021

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“…Anaerobic digestion is divided into four consecutive stages: hydrolysis, acidogenesis (fermentation acidification), acetogenesis and methanogenesis [12]. The first stage of anaerobic digestion is the hydrolysis of polymeric macromolecules, such as proteins, carbohydrates and lipids into smaller molecules, which are more soluble and easily assimilated by microorganisms [12,13]. In the acidogenesis stage, acidogenic bacteria intracellularly metabolize the soluble products formed during hydrolysis.…”

Section: Introductionmentioning

confidence: 99%

“…The metabolism of these compounds results in the formation of alcohols, ketones, CO 2 , H 2 S and, mainly volatile organic acids, with acetic, propionic and butyric acids found in higher concentrations [10,14]. The acetogenesis is a consecutive step in the process, where intermediate organic compounds such as propionate and butyrate are oxidized to acetate, CO 2 and H 2 [13,15]. The final stage is the methanogenesis, which is performed by methanogenic archaea producing methane mainly from acetate [16].…”

Section: Introductionmentioning

confidence: 99%

Characterization of the biodegradation of synthetic and organic wastewater in an anaerobic tank reactor using microalgae

Magyar

Vogel

Tóth

et al. 2021

IRASE

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The anaerobic digestion is a well-known method in waste management of biodegradable wastes to transform waste to energy. Proper digestion requires optimal fermentation conditions to improve the quality and yield of biogas.The objective of this study was to characterize the biodegradation process of synthetic and organic wastewater. Microalgae (Chlorella vulgaris) were utilized as a bioindicator for anaerobic digestion and monitoring of the fermentation process. Besides bioindication, the viability of the microalgae and the chlorophyll concentration were also assessed in such fermentation processes, since microalgae can be a potential source for biofuel production and a plant nutrient.The biodegradation process was studied for a month in an anaerobic tank reactor. The fermentation processes and lengths of the fermentation stages were successfully monitored and separately identified based on the pH and gas development. Furthermore, the amount and dynamics of the biogas yield also revealed that the fermentation process was about 510 hours in both cases. In contrast, increased temperature in thermophilic range (45°C) accelerates the degradation processes and resulted in shorter hydrolysis (60 hours), acetogenesis (24 hours) and longer methanogenesis (81 hours) stages, where higher biogas yield was also achieved (59.3%). During the process, the concentration of nutrients showed logarithmical tendencies and COD showed power tendency in time. The extent and the direction of the changes were in correspondence with microalgae activity. In thermophilic circumstances, living microalgae biomass dropped significantly without recovery therefore such an environment is not a viable option for microalgae growth. Moreover, dead microalgae biomass seems to act as a substrate for fermentation slightly increasing the concentration of some nutrients in the wastewater.

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