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This study focuses on electrical stimulation for composting. Using the PSALSAR method, a comprehensive systematic review analysis identified 22 relevant articles. The examined studies fall into four main systems: electric field-assisted aerobic composting (EAAC), electrolytic oxygen aerobic composting (EOAC), microbial fuel cells (MFCs), and thermoelectric generators (TEGs). Apart from the main systems highlighted above, bioelectrochemically assisted anaerobic composting (AnCBE, III) is discussed as an underexplored system with the potential to improve the efficiency of anaerobic degradation. Each system is described in terms of key materials, composter design, operating conditions, temperature evolution, compost maturity, microbial community, and environmental outcomes. EAAC and EOAC systems accelerate organic matter decomposition by improving oxygen distribution and microbial activity, whereas MFC and TEG systems have dual functioning due to the energy generated alongside waste degradation. These innovative systems not only significantly improve composting efficiency by speeding up organic matter breakdown and increasing oxygen supply but also support sustainable waste management by reducing greenhouse gas emissions and generating bioelectricity or heat. Together, these systems overcome the drawbacks of conventional composting systems and promote future environmental sustainability solutions.
The MICRO4BIOGAS roadmap provides a concise overview of the European biogas sector, placing the spotlight on the microbiome as a key factor in improving biogas production. Central to this is bioaugmentation – the targeted introduction of high-performing microorganisms into biogas plants to optimize biological processes. Funded by the EU under the Horizon 2020 program, the project brings together 14 partners from six countries. One of its major achievements is a comprehensive metagenomic analysis of 80 samples, offering one of the most in-depth insights to date into the microbial communities of European biogas plants. The roadmap highlights the role of key microbial groups – including bacteria, archaea, fungi, and bacteriophages – and their contribution to the efficiency of anaerobic digestion. It also outlines the state of biogas development in selected EU countries and profiles relevant stakeholders in the sector. Beyond its technical focus, MICRO4BIOGAS aims to raise awareness of the crucial role microbiomes play in biogas production. A Europe-wide survey involving over 200 stakeholders and a collaboration with the Spanish municipality of Aras de los Olmos, which is committed to renewable energy, further enrich the project.
Microwave‑assisted organic acids and green hydrogen production during mixed culture fermentation
(2024)
Background The integration of anaerobic digestion into bio-based industries can create synergies that help render anaerobic digestion self-sustaining. Two-stage digesters with separate acidification stages allow for the production of green hydrogen and short-chain fatty acids, which are promising industrial products. Heat shocks can be used to foster the production of these products, the practical applicability of this treatment is often not addressed sufficiently, and the presented work therefore aims to close this gap. Batch experiments were conducted in 5 L double-walled tank reactors incubated at 37 °C. Short microwave heat shocks of 25 min duration and exposure times of 5–10 min at 80 °C were performed and compared to oven heat shocks. Pairwise experimental group differences for gas production and chemical parameters were determined using ANOVA and post–hoc tests. High-throughput 16S rRNA gene amplicon sequencing was performed to analyse taxonomic profiles. After heat–shocking the entire seed sludge, the highest hydrogen productivity was observed at a substrate load of 50 g/l with 1.09 mol H2/ mol hexose. With 1.01 mol H2/ mol hexose, microwave-assisted treatment was not significantly different from oven-based treatments. This study emphasised the better repeatability of heat shocks with microwave-assisted experiments, revealing low variation coefficients averaging 29%. The pre-treatment with microwaves results in a high predictability and a stronger microbial community shift to Clostridia compared to the treatment with the oven. The pre-treatment of heat shocks supported the formation of butyric acid up to 10.8 g/l on average, with a peak of 24.01 g/l at a butyric/acetic acid ratio of 2.0. The results support the suitability of using heat shock for the entire seed sludge rather than just a small inoculum, making the process more relevant for industrial applications. The performed microwave-based treatment has proven to be a promising alternative to oven-based treatments, which ultimately may facilitate their implementation into industrial systems. This approach becomes economically sustainable with high temperature heat pumps with a coefficient of performance (COP) of 4.3.
The holistic characterization of different microbiomes in anaerobic digestion (AD) systems can contribute to a better understanding of these systems and provide starting points for bioengineering. The present study investigates the microbiome of 80 European full-scale AD systems. Operational, chemical and taxonomic data were thoroughly collected, analysed and correlated to identify the main drivers of AD processes. The present study describes chemical and operational parameters for a broad spectrum of different AD systems. With this data, Spearman correlation and differential abundance analyses were applied to narrow down the role of the individual microorganisms detected. The authors succeeded in further limiting the number of microorganisms in the core microbiome for a broad range of AD systems. Based on 16S rRNA gene amplicon sequencing, MBA03, Proteiniphilum, a member of the family Dethiobacteraceae, the genus Caldicoprobacter and the methanogen Methanosarcina were the most prevalent and abundant organisms identified in all digesters analysed. High ratios for Methanoculleus are often described for agricultural co-digesters. Therefore, it is remarkable that Methanosarcina was surprisingly high in several digesters reaching ratios up to 47.2%. The various statistical analyses revealed that the microorganisms grouped according to different patterns. A purely taxonomic correlation enabled a distinction between an acetoclastic cluster and a hydrogenotrophic one. However, in the multivariate analysis with chemical parameters, the mainclusters corresponded to hydrolytic and acidogenic microorganisms, with SAOB bacteria being particularly important in the second group. Including operational parameters resulted in digester-type specific grouping of microbes. Those with separate acidification stood out among the many reactor types due to their unexpected behaviour. Despite maximizing the organic loading rate in the hydrolytic pretreatments, these stages turned into extremely robust methane production units. From 80 different AD systems, one of the most holistic data sets is provided. A very distinct formation of microbial clusters was discovered, depending on whether taxonomic, chemical or operational parameters were combined. The microorganisms in the individual clusters were strongly dependent on the respective reference parameters.
Carbon emission output is one major global problem. Technologies considered environmentally friendly often come with massive drawbacks since current technologies rely on the use of (heavy) metals and rare earth elements (REEs) which have toxic effects when released into the environment. Phytoextraction may depict an innovative supply of metals, while removing contamination of agricultural land at the same time. Metallophytes are not only capable of surviving the toxicity of released metals, they are also able to extract metals from soil making the land usable for agricultural purposes. After doing so the biomass of these plants can be harvested and used to produce bio-ores with 99-100% purity. Being deemed a scientific curiosity for long, research about these plants and their potential use has awakened from its 20 years long slumber and is growing at an accelerating pace. Usage of those phytes to recycle bottom ashes from municipal solid waste incineration, treat waste water and remediate closed mining sites and much more is germinating. Accumulating plants were put from field to the lab and more recently are being put back from the laboratories on the fields. The current gaps in available data are about to be filled and will show if these plants are able to deal with greater challenges than surviving under the conditions they do, which in itself is astonishing already.
Carbon emission output is one major global problem. Technologies considered environmentally friendly often come with massive drawbacks since current technologies rely on the use of (heavy) metals and rare earth elements (REEs) which have toxic effects when released into the environment. Phytoextraction may depict an innovative supply of metals, while removing contamination of agricultural land at the same time. Metallophytes are not only capable of surviving the toxicity of released metals, they are also able to extract metals from soil making the land usable for agricultural purposes. After doing so the biomass of these plants can be harvested and used to produce bio-ores with 99-100% purity. Being deemed a scientific curiosity for long, research about these plants and their potential use has awakened from its 20 years long slumber and is growing at an accelerating pace. Usage of those phytes to recycle bottom ashes from municipal solid waste incineration, treat waste water and remediate closed mining sites and much more is germinating. Accumulating plants were put from field to the lab and more recently are being put back from the laboratories on the fields. The current gaps in available data are about to be filled and will show if these plants are able to deal with greater challenges than surviving under the conditions they do, which in itself is astonishing already.
Der vorliegende Review Artikel thematisiert die Rückführung von abgelagerten Ressourcen aus Deponien und es werden verschiedene Deponieklassen in Anlehnung an die deutsche Deponieverordnung erläutert. Deutschland dient als positives Beispiel für die Errichtung sicherer Deponien, welche je nach Ablagerungsmaterial in unterschiedliche Deponieklassen unterteilt werden. Trotz der fortschrittlichen Ablagerung im internationalen Vergleich ist der Unterhalt einer solchen Deponie als nicht nachhaltig einzustufen. Die Rückgewinnung von Ressourcen ist eine Möglichkeit, die Nachhaltigkeit zu erhöhen. Allerdings ist es umständlich, Deponien zurückzubauen und den Abfall zu sortieren sowie aufzubereiten. Durch verschiedene Aufbereitungsverfahren kann zwischen unterschiedlichen Abfallarten differenziert und so der Output an die gegebene Situation angepasst werden. Unter den verschiedenen Wertstofffraktionen versprechen insbesondere Metalle einen großen Erlös beim Weiterverkauf. Bei Nichtmetallen steht die energetische Nutzung im Vordergrund. Neben den betraglichen Erlösen sind Opportunitätskosten von großer Bedeutung. Neben vermiedenen Kosten für die Instandhaltung werden auch sozialen und ökologischen Folgen reduziert. So können Landflächen zurückgewonnen werden, die als Baugrund genutzt werden können. Die effektive Verwertung von Abfall führt zu einer Reduktion, wodurch die ökologischen Folgen von zu viel Abfall eingegrenzt werden. Deponiebergbau findet schon in vielen Regionen der Welt seine Anwendung. In Anbetracht der Tatsache, dass die Ressourcenknappheit und der steigende Bedarf eine Einschränkung im Konsum hervorrufen können, wird die weitere Erforschung und die technische Umsetzung des Deponiebergbaus zunehmend wichtig.
A demonstrator plant of a recently patented process for improved sludge degradation has been implemented on a municipal scale. In a 1500 m3 sewage sludge digester, an intermediary stage with aerobic sewage sludge reactivation was implemented. This oxic activation increased the biogas yield by up to 55% with a 25% reduction of the remaining fermentation residue volume. Furthermore, this process allowed an NH4-N removal of over 90%. Additionally, 16S rRNA gene amplicon high-throughput sequencing of the reactivated digestate showed a reduced number of methane-forming archaea compared to the main digester. Multiple ammonium-oxidizing bacteria were detected. This includes multiple genera belonging to the family Chitinophagaceae (the highest values reached 18.8% of the DNA sequences) as well as a small amount of the genus Candidatus nitrosoglobus (<0.3%). In summary, the process described here provides an economically viable method to eliminate nitrogen from sewage sludge while achieving higher biogas yields and fewer potential pathogens in the residuals.
In den letzten Jahren hat in der Forschung und Wirtschaft die mikrobielle Biogasproduktion großes Interesse geweckt. Mit diesem Konzept könnte die Versorgung mit erneuerbarer Energie in Zeiten geringerer Energieerzeugung gewährleistet und zusätzlich die Umwelt geschont werden. Bei der Power-to-Gas Technologie wird überschüssige elektrische Energie für die Herstellung von Wasserstoff durch Elektrolyse verwendet. Anschließend werden Wasserstoff und Kohlenstoffdioxid mithilfe von hydrogenothrophen methanogenen Archaeen zu Methan (CH4) umgewandelt. Bei ausreichender Qualität (>97%) könnte dieses ins nationale Erdgasnetz eingespeist werden. Dieses Verfahren kann durch die direkte Zugabe von H2 in einem Fermenter (in-situ) oder extern in einem separaten Biogasreaktor (ex-situ) stattfinden. In der vorliegenden Arbeit wurden die jüngsten Forschungsergebnisse in Bezug auf das ex-situ Verfahren analysiert und zusammengetragen. Genauer wurde die Beeinflussung der Prozessvariablen sowie optimale Reaktionsbedingungen diskutiert. Zusätzlich zum eigentlichen Ablauf des ex-situ Prozesses wird am Ende der Arbeit die Wirtschaftlichkeit erörtert. Die Ergebnisse belegen, dass die ex-situ Biomethanisierung eine Produktgasqualität von mehr als 95% erreichen kann. Dafür müssen die Prozessvariablen jedoch optimal eingestellt werden. Gut geeignet wäre z.B. eine mit Methanobacterium angereicherte Mischkultur mit einem pH-Wert im Bereich von 7,1 bis 8,5. Weiterhin erläutern viele Studien, dass eine ausreichende Nährstoffversorgung, 5 bar Betriebsdruck und eine Umgebungstemperatur von 35 °C bis 55°C optimale Betriebsbedingungen darstellen. Aus wirtschaftlicher Sicht ist Biomethan nach aktuellem Stand der Technik preisintensiver als herkömmliche Methanquellen. Jedoch könnten unter Berücksichtigung umweltschonender Effekte, Klimaschutz sowie dem Vertrieb von CO2- Zertifikaten die Kosten ausgeglichen und ein niedrigeres Preisniveau erreicht werden. Zusammenfassend stellt Power-to-Gas eine vielversprechende Zukunftstechnologie dar, welche die Möglichkeit auf eine umweltfreundliche und nahezu CO2-neutrale Biomethanproduktion unter Verwendung überschüssiger Energie eröffnet.
Aufgrund einer weltweit geringen Recyclingquote der Kunststoffe von 9% und Belastung von Luft, Wasser und Boden, ist es notwendig das Recycling und alles darum zu optimieren. Das Ziel der vorliegenden Arbeit war es unterschiedliche Methoden des Recyclings und Prozesse vor dem Recycling, wie die Sortierung und Reinigung zu analysieren und in Bezug auf ihre Effizienz zu bewerten. Im Rahmen dieser Untersuchung wurde das Sortierverfahren der Flotationstrennung mit diversen Ausgangsstoffen genauer untersucht. Hier beweisen experimentelle Ergebnisse eine maximale Rückgewinnungsrate von 99,34%. Zudem wurde auch die beste sensorgestützte Sortierungsmethode im Zusammenhang der verwendeten Literatur genannt. Dieser Mechanismus nennt sich VIP-Scores-Verfahren. Zur Thematik Reinigung von kontaminierten Kunststoffen gibt es ein neuartiges Verfahren zur wasserlosen Reinigung mit Flusssand. Diese Methodik erlaubt eine Reinigungsrate von bis zu 97% bei einer mittleren Partikelgröße. Dazu geht diese Arbeit auf Verfahren des mechanischen, chemisch und thermischen Recyclings ein. Mechanisches Recycling bringt eine hohe Energierückgewinnungsquote mit sich. Jedoch müssen für die Durchführung dieser Prozess einige Bedingungen erfüllt sein. Das thermochemische Verfahren der hydrothermalen Verflüssigung bietet dagegen Möglichkeiten auch gemischte Kunststoffe zu verarbeiten. Des Weiteren ist das Upcycling von Kunststoffen mittels enzymatischer Depolymerisation möglich. Der Stand der Forschung dieser Arbeit beschränkt sich auf den Zeitraum 01.01.2020- 14.11.2022.
