Valorization of Anaerobic Digestate from Biowaste to High-Value Bioproducts: A Review

Tumaševičiūtė, Rasa; Ignatavičius, Gytautas

doi:10.3390/proceedings2019016001

Cited by 1 publication

(2 citation statements)

References 28 publications

(25 reference statements)

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“…Although anaerobic digestate is generally considered a valuable commodity predominantly used as fertilizer, the sheer volume of its accumulation and the ecological problems accompanying massive fertilization require the implementation of more sustainable and economical utilization routes. For this, anaerobic digestate needs to be established as a resource for additional cascade valorization to facilitate comprehensive biomass utilization throughout the whole biogas production process (Guilayn et al, 2022 ; Kaur et al, 2020 ; Monlau et al, 2015 ; Tumaševičiūtė & Ignatavičius, 2019 ). In this study, we show that valuable sterol lipids are not degraded during anaerobic digestion in typical agricultural and biowaste biogas plants and therefore remain in the final digestates, which provides a novel opportunity for digestate valorization as a sterol resource for biotechnological applications.…”

Section: Discussionmentioning

confidence: 99%

“…Based on these concerns, restrictive regulations of digestate land application have been enacted by legislative bodies in most countries with significant biogas production capacities (European Parliament, 2019 ; U.S. Environmental Protection Agency, 2021 ; Wang et al, 2020 ). Accordingly, cascade valorization of anaerobic digestate is increasingly used to maximize biomass utilization and minimize its adverse effects (Guilayn et al, 2022 ; Kaur et al, 2020 ; Monlau et al, 2015 ; Tumaševičiūtė & Ignatavičius, 2019 ). Thermo‐chemical valorization, such as pyrolysis, combustion or hydrothermal carbonization, generates additional energy and value‐added products from whole or solid digestate in the form of heat, bio‐char, bio‐oils or syngas (Guilayn et al, 2022 ; Monlau et al, 2015 ; Sheets et al, 2015 ; Szulc et al, 2021 ).…”

Section: Introductionmentioning

confidence: 99%

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Biogas digestate as a sustainable phytosterol source for biotechnological cascade valorization

Weckerle

Ewald

Guth

et al. 2022

Microbial Biotechnology

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Every year, several million tonnes of anaerobic digestate are produced worldwide as a by‐product of the biogas industry, most of which is applied as agricultural fertilizer. However, in the context of a circular bioeconomy, more sustainable uses of residual digestate biomass would be desirable. This study investigates the fate of the sterol lipids β‐sitosterol and cholesterol from the feedstocks to the final digestates of three agricultural and one biowaste biogas plants to assess if sterols are degraded during anaerobic digestion or if they remain in the digestate, which could provide a novel opportunity for digestate cascade valorization. Gas chromatographic analyses showed that feedstock sterols were not degraded during anaerobic digestion, resulting in their accumulation in the digestates to up to 0.15% of the dry weight. The highest concentrations of around 1440 mg β‐sitosterol and 185 mg cholesterol per kg dry weight were found in liquid digestate fractions, suggesting partial sterol solubilization. Methanogenic batch cultures spiked with β‐sitosterol, cholesterol, testosterone and β‐oestradiol confirmed that steroids persist during anaerobic digestion. Mycobacterium neoaurum was able to transform digestate sterols quantitatively into androstadienedione, a platform chemical for steroid hormones, without prior sterol extraction or purification. These results suggest that digestate from agricultural and municipal biowaste is an untapped resource for natural sterols for biotechnological applications, providing a new strategy for digestate cascade valorization beyond land application.

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