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Innovations in Gaseous, Liquid and Solid Products during Biogas Generation...
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Innovations in Gaseous, Liquid and Solid Products during Biogas Generation and Utilization

A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Environmental and Green Processes".

Deadline for manuscript submissions: closed (30 June 2024) | Viewed by 6971

Special Issue Editors

Prof. Dr. Paul A. Scherer

E-Mail Website
Guest Editor
Department of Biotechnology, Faculty of Life Sciences, University of Applied Sciences (HAW-Hamburg), 21030 Hamburg, Germany
Interests: anaerobic waste water treatment; anaerobic solid waste treatment; hygienic aspects; microbiome studies; batch and continuous biogas fermentation with energy crops and agricultural residues; fermentation analytics; trace elements; consultancy of biogas plant operators; fuzzy logic control; MilliGascounter (patents)
Prof. Dr. Richard Arthur

E-Mail Website
Guest Editor
Department of Energy Systems Engineering, Dean of Faculty of Engineering, Koforidua Technical University, Koforidua P.O. Box KF981, Ghana
Interests: anaerobic digestion of agricultural residues and energy crops; waste-to-energy; wastewater treatment; batch and continuous fermentation; fermentation analytics; trace elements; climate protection; bioenergy resources assessment

Special Issue Information

Dear Colleagues,

The number of full-scale biogas plants is continuously increasing worldwide, especially in Germany, with approximately 9800 biogas plants. Biogas technology is not just an energy technology, but an environmental technology as well. It can sanitize and detoxify fecal material such as livestock manure, and the digestates can be used as fertilizer or as a base for humus formation. Digestate, in turn, can be transformed into biochar, but this manufacturing process is not within the scope of this Special Issue. Straw, grass, polluting algae, water hyacinths, wild flowers, municipal biowaste and even restaurant leftovers can also be used as input. In parallel, the question arises as to which waste materials can be best used in a given country without competing with land use for food production. The microbiology in the fermentation reactor also needs attention. Biogas is unique, CO2 neutral or, in some coupled processes, even CO2 negative, but sometimes the greenhouse gas balance is challenged. Therefore, articles about the GHG balance are also welcomed. The purified gaseous product, biomethane, is the only one that embodies the three types of energy: electricity, heat and fuel. The biogas can be compressed and used in a decentralized manner. Many countries have a gas grid for conventional sources such as fossil gas, which could serve as a huge energy battery to store biomethane. A country like Denmark, for example, has set itself the goal of becoming completely independent of gas imports in the next decade through biomethane. By producing electricity in a central heating power plant, heat can be used as byproduct. This leads to the highest conversion efficiency of about 90% in renewables, which is feasible. In times of resource dependency, gas is becoming increasingly important as a directly usable product (including the use of CO2 in pure form for industrial purposes). Anaerobic degradation processes also concentrate salts; the effluent products ammonium and H2S could represent a severe environmental and technical problem. In some regions, the use of digestates as fertilizers is limited, while in other regions it is highly recommended. Therefore, there are developments in densely populated areas to refine fermentation residues to produce humus formers, transportable inorganic salts as fertilizers and potable water. Therefore, manuscripts on these topics are also welcomed.

Prof. Dr. Paul A. Scherer
Prof. Dr. Richard Arthur
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Processes is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • emissions
  • greenhouse gases
  • effluents
  • biogas plants
  • digestates
  • fertilizers
  • biomethane

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Published Papers (4 papers)

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Research

18 pages, 3810 KiB  
Article
Continuous Biological Ex Situ Methanation of CO2 and H2 in a Novel Inverse Membrane Reactor (IMR)
by Fabian Haitz, Oliver Jochum, Agnieszka Lasota, André Friedrich, Markus Bieri, Marc Stalder, Martin Schaub, Ulrich Hochberg and Christiane Zell
Processes 2024, 12(10), 2305; https://doi.org/10.3390/pr12102305 - 21 Oct 2024
Viewed by 1618
Abstract
A promising approach for carbon dioxide (CO2) valorization and storing excess electricity is the biological methanation of hydrogen and carbon dioxide to methane. The primary challenge here is to supply sufficient quantities of dissolved hydrogen. The newly developed Inverse Membrane Reactor [...] Read more.
A promising approach for carbon dioxide (CO2) valorization and storing excess electricity is the biological methanation of hydrogen and carbon dioxide to methane. The primary challenge here is to supply sufficient quantities of dissolved hydrogen. The newly developed Inverse Membrane Reactor (IMR) allows for the spatial separation of the required reactant gases, hydrogen (H2) and carbon dioxide (CO2), and the degassing area for methane (CH4) output through commercially available ultrafiltration membranes, enabling a reactor design as a closed circuit for continuous methane production. In addition, the Inverse Membrane Reactor (IMR) facilitates the utilization of hydraulic pressure to enhance hydrogen (H2) input. One of the process’s advantages is the potential to utilize both carbon dioxide (CO2) from conventional biogas and CO2-rich industrial waste gas streams. An outstanding result from investigating the IMR revealed that, employing the membrane gassing concept, methane concentrations of over 90 vol.% could be consistently achieved through flexible gas input over a one-year test series. Following startup, only three supplemental nutrient additions were required in addition to hydrogen (H2) and carbon dioxide (CO2), which served as energy and carbon sources, respectively. The maximum achieved methane formation rate specific to membrane area was 87.7 LN of methane per m2 of membrane area per day at a product gas composition of 94 vol.% methane, 2 vol.% H2, and 4 vol.% CO2. Full article
(This article belongs to the Special Issue Innovations in Gaseous, Liquid and Solid Products during Biogas Generation and Utilization)
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17 pages, 9534 KiB  
Article
Pelletized Straw for Biogas Production—Substrate Characterization and Methane Formation Potential
by Fabian Gievers, Meike Walz, Kirsten Loewe and Achim Loewen
Processes 2024, 12(8), 1549; https://doi.org/10.3390/pr12081549 - 24 Jul 2024
Cited by 1 | Viewed by 1521
Abstract
The use of agricultural residues in biogas plants is becoming increasingly important, as they represent an efficient and sustainable substrate alternative. Pelletizing straw can have positive effects on transportation, handling, and biogas production. In this study, different grain straw pellets from mobile and [...] Read more.
The use of agricultural residues in biogas plants is becoming increasingly important, as they represent an efficient and sustainable substrate alternative. Pelletizing straw can have positive effects on transportation, handling, and biogas production. In this study, different grain straw pellets from mobile and stationary pelleting plants in Germany as well as the corresponding untreated straw were characterized and investigated for their suitability for anaerobic digestion (AD). Therefore, tests on the biochemical methane potential (BMP) and the chemical–physical characterization of unpelletized straw and straw pellets were carried out. The characterization of the pellets and the straw revealed a high average total solid content of 91.8% for the industrially produced straw pellets and of 90.8% for the straw. The particle size distribution within the tested pellet samples varied greatly depending on the pelleting process and the pre-treatment of the straw. In addition, a high C/N ratio of 91:1 on average was determined for the straw pellets, whereas the average higher heating value (HHV) content of the pellets was 17.58 MJ kg−1. In the BMP tests, the methane production yields ranged from 260–319 normal liter (NL) CH4 kg−1 volatile solids (VS) for the straw pellets and between 262 and 289 NL CH4 kg−1 VS for the unpelletized straw. Overall, pelleting increases the methane yield on average from 274 to 286 NL CH4 kg−1 VS, which corresponds to an increase in methane yield of 4.3%. Based on the results, the feasibility of using straw pellets for AD could be confirmed, which can facilitate the possibility of increased biogas production from agricultural residues such as straw pellets and thus make the substrate supply more sustainable. Full article
(This article belongs to the Special Issue Innovations in Gaseous, Liquid and Solid Products during Biogas Generation and Utilization)
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17 pages, 1704 KiB  
Article
Temperature Control Effect on Cheese Whey Anaerobic Digestion with Low-Cost Tubular Digesters
by Juan Luis Ramos-Suárez, Sergio J. Álvarez-Méndez, Eseró Padrón Tejera, Axel Ritter and Javier Mata González
Processes 2024, 12(7), 1452; https://doi.org/10.3390/pr12071452 - 11 Jul 2024
Cited by 2 | Viewed by 1342
Abstract
Cheese whey (CW) is a worldwide abundant by-product of the cheese industry, which can be used for biogas production if further processing is not performed to produce other valuable food products. This study evaluates biogas production from CW in low-cost, tubular reactors, thus [...] Read more.
Cheese whey (CW) is a worldwide abundant by-product of the cheese industry, which can be used for biogas production if further processing is not performed to produce other valuable food products. This study evaluates biogas production from CW in low-cost, tubular reactors, thus comparing the effect of temperature control. CW was monodigested in two tubular reactors at the pilot scale: one of them with temperature control (30 ± 3 °C) and the other one working at environmental conditions. The results show that CW could be monodigested in pilot scale tubular reactors, thus yielding high methane. Temperature control (30 ± 3 °C) at the pilot scale led to higher methane yields under all tested operating conditions, thus reaching 565.8 ± 20.9 L kg−1VS at an Organic Loading Rate (OLR) of 0.416 ± 0.160 kgVS L−1 d−1, which was higher than the maximum yield obtained without temperature control (445.6 ± 21.9 L kg−1VS) at 0.212 ± 0.020 kgVS L−1 d−1. Methane yield differences were attributed to the increase in temperature, thus leading to a more stable process and a higher degradation capacity. The increase in temperature is only worthwhile if adequate thermal insulation is used between the digester and the soil; otherwise, the increase in biogas production will not meet the digester’s heat demand. The anaerobic monodigestion of CW in low-cost tubular reactors is a promising alternative for CW valorization, thus leading to high biogas yields, which can be used in several energy applications replacing fossil fuels. Full article
(This article belongs to the Special Issue Innovations in Gaseous, Liquid and Solid Products during Biogas Generation and Utilization)
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16 pages, 2234 KiB  
Article
Restoring the Stability of Long-Term Operated Thermophilic Anaerobic Digestion of Maize Straw by Supplying Trace Elements
by Bridget Ataa Fosua, Lijuan Ren, Wei Qiao, Jiahao Zhang, Yanning Gao, Xianli Fu, Dunyao Yu and Renjie Dong
Processes 2023, 11(12), 3440; https://doi.org/10.3390/pr11123440 - 16 Dec 2023
Viewed by 1593
Abstract
Maize straw has been widely used for the production of energy through anaerobic digestion, but biogas production can be hindered by a lack of trace elemental nutrients. To address this issue, a lab-scale anaerobic plug flow reactor was continuously operated at 55 °C [...] Read more.
Maize straw has been widely used for the production of energy through anaerobic digestion, but biogas production can be hindered by a lack of trace elemental nutrients. To address this issue, a lab-scale anaerobic plug flow reactor was continuously operated at 55 °C for 300 days, with a hydraulic retention time of 42 days and an organic loading rate of 2.1 g total solids/(L·day). Results from this study showed that between days 101 and 194, the methane yield slightly decreased from 0.26 ± 0.04 to 0.24 ± 0.03 L/g volatile solids (VS), but significant volatile fatty acid accumulation was observed by reaching up to 2759 ± 261 mg/L. After trace elements were added to the reactor, the methane yield increased to 0.30 ± 0.03 L/g VS, with 53% methane content. Around 62% of the total chemical oxygen demand and volatile solids were broken down into methane. Volatile fatty acid levels dropped and stabilized at around 210 ± 50 mg/L, indicating restored process stability. The addition of trace elements increased the abundance of Firmicutes and decreased Synergistetes in bacteria while simultaneously increasing the abundance of Methanosarcina in archaea. In conclusion, trace element supplementation was experimentally found to be necessary for stable thermophilic anaerobic digestion of maize straw. Full article
(This article belongs to the Special Issue Innovations in Gaseous, Liquid and Solid Products during Biogas Generation and Utilization)
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