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Das Institut für Abfall- und Kreislaufwirtschaft (IAK) der TU Dresden ist am von der Europäischen Union im Rahmen des H2020-Programms geförderten Projekts "Micro4Biogas" beteiligt. Ziel des Projektes ist es, zur Unterstützung und Modernisierung des Biogassektors in den EU-Ländern beizutragen. Im Mittelpunkt stehen die Untersuchung der anaeroben Vergärung und des Mikrobioms, welche trotz jahrzehntelanger Forschung nicht ausreichend entschlüsselt sind. Obwohl das Wissen über die beteiligten Mikroorganismen zunimmt, wird das Mikrobiom nach wie vor als "Black Box" betrachtet. Im Rahmen von Micro4Biogas erfolgt die Charakterisierung natürlicher mikrobieller Gemeinschaften sowie die Erforschung neuer synthetischer mikrobieller Gemeinschaften. Darauf aufbauend erfolgt die Entwicklung von Strategien zur gezielten Beeinflussung des Mikrobioms (Bioaugmentation), die dazu dienen, den Prozess robuster, schneller, produktiver und standardisierter zu gestalten. Das bestehende und generierte Fachwissen wird in einer frei verfügbaren Roadmap zusammengefasst. Die Roadmap soll zudem Leitlinien und Handlungsempfehlungen für Industrie und Politik zur nachhaltigen und optimierten Produktion von Biogas enthalten.
Composting is one of the most widely applied methods for recycling organic waste. This process has been proposed as one option that facilitates the reincorporation of materials into the production cycle. However, composting also generates environmental impacts. Life Cycle Assessment (LCA) is the most common approach to evaluate the environmental impacts of a process at different system stages. Nevertheless, applying LCA in composting facilities is challenging due to the extensive information required, the lack of standardization on the initial assumptions, the definition of system boundaries, and the high diversity of existing composting technologies. This paper systematically reviews LCA studies in biowaste and/or green waste composting. The study highlights the challenges that should be met in order to improving the application of LCA to evaluate the environmental impacts of this type or waste treatment strategy. The review protocol used identified 456 papers published between 2010 and 2022. After the screening, 56 papers were selected, read, and thoroughly analyzed. The results show that: i) about 68% of the studies aimed to compare composting with other solid waste management options; ii) there was a wide diversity among the impact categories considered, which predominantly included climate change and ozone depletion; iii) there was no consensus on the functional unit or the system boundaries; iv) the main gaseous emissions studied were ammonia, methane, and nitrogen oxide, which were generally determined by emission factors; v) the avoided environmental impacts associated with the end-product quality and its application as an organic amendment or soil improver were ignored. This work demonstrates the complexity of conducting credible and valid composting LCA studies and proposes seven recommendations for improving the application of this assessment methodology to analyze this waste management alternative.
Das Streben nach umweltfreundlicher Energie und Wertstoffen hat in den letzten Jahren, gestärkt durch Wirtschaft und Politik, den Drang nach Innovation erheblich angeregt. Dieser Entwicklungsdrang findet sich in vielen Bereichen wieder, unter anderem in der Bioökonomie und hier auch bei Biogasanlagen. Das Schlagwort „Mikrobiom“ ist im medizinischen Bereich bereits weit verbreitet und wird im populärwissenschaftlichen Bereich in zahlreichen Büchern diskutiert. Dies unterstreicht das große gesellschaftliche Interesse an diesem Thema. Neben diesen Erkenntnissen gewinnt das Mikrobiom im Bereich der Bioenergien zunehmend an Bedeutung. In den letzten Jahren sind in hochrangigen, internationalen Fachjournalen zahlreichen Artikel erschienen, welche aufzeigen, dass Biogasanlagen wahre Superhelden unter den Mikroorganismen beherbergen. Die hohe Diversität wurde bereits in zahlreichen Publikationen diskutiert. Trotz dessen wird das Mikrobiom als „Blackbox“ betrachtet. Wissenschaftler weltweit versuchen diese Blackbox aufzulösen und hierbei traten einige Überraschungen auf. Dieses neue Wissen könnte den Grundstein für neue Konzepte der Prozesssteuerung legen. Ziel der vorliegenden Arbeit ist in diesem Zusammenhang eine Kurzübersicht über mikrobielle Innovation im Zusammenhang mit anaeroben Mikrobiomen.
Der Artikel stellt das Fachgebiet der Kreislaufwirtschaft an der BTU vor. Forschungsthemen des Fachgebietes werden kurz erläutert. Diese umfassen Biolaugung zur Behandlung von Leiterplatten, anaerobe Fermentation als Multiproduktplattform, Power2Gas Prozesse sowie das Verständnis mikrobieller Gemeinschaften mit Bedeutung für die Kreislaufwirtschaft.
The authors of the present work summarize their recently published article “Microbiome Characterization after Aerobic Digestate Reactivation of Anaerobically Digested Sewage Sludge” from Otto et al. (2023). This article presents the outcomes of a municipal-scale demonstrator plant implementing a recently patented process for improved sludge degradation within a municipal sewage treatment system. The study focused on a 1500 m³ sewage sludge digester, where an intermediate aerobic sewage sludge reactivation stage was introduced. This reactivation resulted in a 55% increase in biogas production and a 25% reduction in residual solids. For the residual NH4 in the liquid phase of the sewage sludge, the process achieved NH4-N removal rates exceeding 90%. To gain insights into the microbial community dynamics, 16S rRNA gene amplicon high-throughput sequencing was employed on the reactivated digestate. The analysis revealed a reduced population of methane-forming archaea compared to the primary digester, along with the detection of multiple ammonium-oxidizing bacteria. Notably, genera within the Chitinophagaceae family, comprising up to 18.8% of DNA sequences, were prevalent, alongside a small presence of Candidatus nitrosoglobus (<0.3%). The study highlights an economically viable approach for efficient nitrogen removal from sewage sludge while simultaneously increasing biogas yields and reducing potential pathogens in the residual material.
Unveiling the Biochar Potential: Lowering Greenhouse Gas Emissions across the Biogas Supply Chain
(2024)
The carbon-rich material known as biochar is the product of pyrolysis – a thermochemical conversion of biomass in the absence of oxygen. Given its characteristics, including long-term stability and sorption capacity, biochar has received increasing attention as a promising tool for addressing climate change and enhancing the production of biogas. This work combines both functions by examining, through different application scenarios, the potential role of biochar in mitigating greenhouse gas (GHG) emissions across the biogas supply chain. The wood-derived and high pyrolyzed biochar CarboFerm® was used as an example biochar for application in four different scenarios: (1) Application to soil without fertilizer, (2) application to soil with fertilizer, (3) application to biogas fermenter, (4) application to digestate treatment. The GHG mitigation was calculated by applying the methodology of the Renewable Energy Directive II (RED II). The scenario comparison resulted in GHG mitigation effectiveness of 0.03, 0.01, 0.06, and 0.03 g CO2eq / MJ biogas / t biochar, respectively. Thus, this study recommends using biochar in biogas fermenters and subsequently applying the biochar-enriched digestate to agricultural soil to reduce GHG emissions from biogas production. Furthermore, it is suggested that the mitigation potential of biochar may not be fully recognized in the RED, potentially resulting in an underestimation of its effectiveness.
In the last 20 years there has been a growing need for climate mitigation strategies. Starting with the Emission Trading in the Kyoto protocol in 1997, the concept of a carbon market arose. Carbon markets opened an avenue giving countries and businesses an opportunity to trade their emissions as a commodity. The Paris agreement has further acted as an incentive. This led to the introduction of the Carbon Credit. A single carbon credit has been defined as one ton of equivalent CO2, strategies to calculate a baseline for emissions and crediting systems followed. However, currently we still lack a universal method of estimation. There have been efforts by the UNFCCC’s clean development mechanism, IPCC and the private sector to develop calculation mechanisms. Despite this, there have been issues in the credibility of these credits. With the Introduction of the non-compliance market there has been a growth of carbon credits in the voluntary markets. This leads to the basic question: Do scientific articles give insight into the existing carbon credit market? The presented study aims to answer the question, using the PSALSA method of systematic review analysis.
Das Mikrobiom umfasst die Gesamtheit aller Mikroorganismen, die ein Makroorganismus (Mensch, Tiere, Boden oder Biogasanlage) besiedelt. Aufgrund der Komplexität und Individualität der interagierenden Parameter ist das Zusammenwirken des Mikrobioms nicht ausreichend erforscht. Diese Studie fokussiert auf die Beeinflussung des Mikrobioms von Biogasanlagen durch chemische, technische und mikrobielle Faktoren.
At the BIOENERGY DOC2022 (5th doctoral colloquium bioenergy), results from the currently running EU project Micro4Biogas were presented (https://micro4biogas.eu/). The presented poster describes the sampling of more than 70 samples from a large number of biogas plants in Germany and the Netherlands. Samples were analysed chemically and taxonomically. A comprehensive dataset was developed for the technical description of the respective plants. In the next step, a holistic, multivariate analysis of the collected data sets is planned.
Production waste from the manufacture of PCB often contains gold-containing contact-strips, whereby the gold content is < 1 %. Recycling of these gold coatings with conventional melting processes is technically hardly, since the carrier materials often contain mechanical reinforcements and flame retardants in addition to thermosetting plastics. With mechanical recycling, gold losses of 50% are possible.
Therefore, a bioleaching plant for the recovery of gold and copper as preliminary stage for the smelting process has been in operation on m&k´s site since May 2022. The bioleaching is realized with iron and sulfur oxidizing bacteria, e.g. Leptospirilum ferrooxidans. The apparatus consists of a 400 litres-leaching bioreactor and peripheral equipment (fermenter, cementation, filters). The plant can process up to 10 kg of gold-containing PCB waste per batch, while simultaneously regenerating a second batch of bioleaching fluid. The process can recover up to 450 mg goldtinsel and 25 g copperpowder per Kilogramm input.
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.
Background:
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.
Results:
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 main clusters 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.
Conclusions:
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.
Wissenschaftler*innen des europäischen Forschungsprojektes Micro4Biogas haben eine neue taxonomische Ordnung von Bakterien entdeckt und klassifiziert, die auf die Zersetzung von organischem Material spezialisiert sind und der Schlüssel zu einer optimierten Biogasproduktion sein könnten. Die von ihnen als Darwinibacteriales bezeichnete Ordnung ist eine der am häufigsten vorkommenden Bakterien-Ordnungen in Biogasanlagen, wurde aber bisher noch nie wissenschaftlich klassifiziert.