FG Kreislaufwirtschaft
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Heavy metals are essential for technological and economic growth but can cause serious environmental and health problems due to their toxicity and persistence. Traditional methods for metal recovery often have high costs and can create secondary pollution. Bioleaching offers a sustainable, low-energy, and eco-friendly alternative, effectively recovering metals from low-grade ores and various waste materials. Recovering metals from secondary sources such as industrial and electronic waste reduces the need for new mining, thus conserving natural resources and supporting circular economic goals. Recently, biomining has expanded beyond Earth, showing promising results in space environments. This review discusses the current understanding of bioleaching processes, their potential for sustainable metal recovery on Earth and in space, their challenges, and future perspectives. Overcoming technical challenges, such as raw material composition, slow reaction kinetics, optimization of process parameters, and addressing safety concerns is crucial. A further increase in research focus aiming at scaling up bioleaching technology is essential, alongside addressing ethical and economic concerns related to space mining.
Die Landwirtschaft spielt in Georgien trotz zunehmender Urbanisierung eine zentrale wirtschaftliche Rolle, insbesondere in ländlichen und gebirgigen Regionen, wobei 16 % der Erwerbstätigen rund 6,2 % des BIP erwirtschaften. Herausforderungen wie geringe Wettbewerbsfähigkeit, unzureichende Landverteilung, fehlende moderne Technologien, geringe Abfallverwertung und Umweltbelastungen durch unsachgemäße Entsorgung von landwirtschaftlichen Rückständen erfordern innovative Ansätze. Das Waste2Wealth- Projekt (W2W), gefördert vom BMUKN, zielt darauf ab, diese Rückstände systematisch zu nutzen und Wissen, Technologie und Praxis miteinander zu verbinden. Hierzu werden Potenzialanalysen für landwirtschaftliche Reststoffe durchgeführt, Verwertungswege wie Biogasproduktion und Biokohleherstellung geprüft, und praxisnahe Instrumente wie das W2W-Whitebook, digitale Lernplattformen („Digitales LERNHAUS“), Train-of-Trainer-Module und ein mobiler Demonstrationscontainer implementiert. Das Projekt fördert Kapazitätsaufbau, Stakeholder-Engagement und den Technologietransfer zwischen Deutschland und Georgien, um eine zirkuläre Bioökonomie zu etablieren, die ökologische Nachhaltigkeit, wirtschaftliche Entwicklung und die Nutzung lokaler Ressourcen verbindet.
Despite increasing urbanisation, agriculture plays a central economic role in Georgia, especially in rural and mountainous regions, with 16 % of the working population generating around 6.2 % of GDP. Challenges such as low competitiveness, inadequate land distribution, a lack of modern technologies, low waste recycling rates and environmental pollution caused by the improper disposal of agricultural residues require innovative approaches. The Waste2Wealth (W2W) project, funded by the BMUKN, aims to systematically utilise these residues and combine knowledge, technology and practice. To this end, potential analyses for agricultural residues are being carried out, recycling methods such as biogas production and biochar production are being examined, and practical tools such as the W2W White Paper, digital learning platforms (‚Digitales LERNHAUS‘), train-of-trainer modules and a mobile demonstration container are being implemented. The project promotes capacity building, stakeholder engagement and technology transfer between Germany and Georgia in order to establish a circular bioeconomy that combines ecological sustainability, economic development and the use of local resources.
Bioaugmentation, the intentional introduction of specific microorganisms into anaerobic digestion (AD) systems, has shown promise in enhancing methane production and in mitigating stressful conditions, particularly in systems operating below optimal performance. This review presents a systematic literature review (SLR) of research on bioaugmentation in AD. This review identified and analysed studies meeting predefined eligibility criteria through a structured methodology involving research protocol, search, appraisal, synthesis, analysis, and reporting. A notable innovation of this review is its comprehensive critical comparison of different controls used in bioaugmentation studies, which has been inadequately addressed in previous literature. To facilitate the functional understanding, strains for bioaugmentation were grouped into the four phases of anaerobic digestion (hydrolysis, acidogenesis, acetogenesis and methanogenesis). A highly diverse set of microbes has been described for bioaugmentation, especially from the families
Clostridiaceae, Pseudomonadaceae and Syntrophomonadaceae. Most works are related to hydrolysis. The few works that address acidogenesis are mostly related to dark fermentation. Several studies used methanogenic archaea as well as syntrophic acetate oxidising bacteria, despite the difficulties in culturing them. On the other hand, studies applying strains for acetogenesis were largely underrepresented. Especially works on syntrophic propionate and butyrate oxidation (SPO and SBO) were missing.
This study presents the first application of fuzzy logic control (FLC) for regulating in-situ biological methanation via H2 injection in a fixed-bed reactor. Given the role of CH4 as a storable and infrastructure-compatible energy carrier, the aim was to improve CH4 production by dynamically adapting the H2 supply to the metabolic capacity of the microbiome. This will pave the way for the biological utilisation and storage of renewable H2. Over a 226- day operational period, H2 input was gradually increased based on real-time headspace gas measurements. Coupling the gradual increase in H2 supply with real-time gas composition data allowed the microbiome to adapt dynamically to changing process conditions. This approach led to a 49 % increase in CH4 concentration, from 58.4 % to 87.0 %, and improved H2 conversion rates from 98.2 % to 99.0 %. Chemical analyses of COD, organic acids and nitrogen were performed, as well as taxonomic analyses using 16S rRNA sequencing, and multivariate methods were applied to confirm the adaptation of the microbiome to the FLC H2 injection. The adopted microbial community was dominated by strictly hydrogenotrophic methanogens, Methanoculleus and Methanobacterium, while increased abundances of Petrimonas, Rectinema, Syntrophomonas, and Geobacter indicate interspecies H2 transfer and syntrophic cooperation enhancing methanogenesis. These findings demonstrate that FLC-based H2 control enables dynamic adjustment of in-situ methanation, optimising the interaction between hydrogenogenic, fermentative, syntrophic acetate-oxidising, and hydrogenotrophic microorganisms. This work introduces an adaptive control strategy that supports stable and efficient bio-CH4 production and represents a significant advance in the field of power-to-gas technologies.
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.
Biogas, a mix of CO2, CH4 and small proportions of other gases, is a biofuel obtained by anaerobic digestion (AD). Biogas production is often considered a black box process, as the role and dynamics of some of the microorganisms involved remain undisclosed. Previous metataxonomic studies in the frame of the MICRO4BIOGAS project (www. micro 4biog as. eu) revealed that MBA03, an uncharacterised and uncultured bacterial taxon belonging to phylum Bacillota, was very prevalent and abundant in industrial full-scale AD plants. Despite the efforts, this taxon has not yet been cultivated, which makes the analysis of its taxonomy, ecology and metabolism even more challenging. In the present work, 30 samples derived from anaerobic digesters were sequenced, allowing the reconstruction of 108 metagenome-assembled genomes (MAGs) potentially belonging to MBA03. According to phylogenetic analyses and genomic similarity indices, MBA03 was classified as a new bacterial order, proposed as ‘Candidatus Darwinibacteriales’ ord. nov., which includes ‘Candidatus Darwinibacter acetoxidans’ gen. nov., sp. nov. of ‘Candidatus Darwinibacteriaceae’ fam. nov., along with ‘Candidatus Wallacebacter cryptica’ gen. nov., sp. nov. of the ‘Candidatus Wallacebacteriaceae’ fam. nov. Ecotaxonomic studies determined that AD processes are the main ecological niche of ‘Candidatus Darwinibacteriales’. Moreover, metabolic predictions identified Darwinibacteraceae members as putative syntrophic acetate-oxidising bacteria (SAOB), as they encode for the reversed Wood–Ljungdahl (W–L) pathway coupled to the glycine cleavage system. This suggests that Darwinibacteraceae members could work in collaboration with hydrogenotrophic methanogenic archaea to produce methane in industrial biogas plants. Overall, our findings present ‘Candidatus Darwinibacteriales’ as a potential key player in anaerobic digestion and pave the way towards the complete characterisation of this newly described bacterial taxon, which has not yet been cultured.
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.
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.
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.