Die Anwendung von Biokohlen in der Landwirtschaft gewinnt durch die positiven Aspekte der Kohlenstoffsequestrierung, Bodenverbesserung und eines erhöhten Pflanzenwachstums in den letzten Jahren an Bedeutung. Deshalb geht die vorliegende Arbeit den Fragen nach, welche Wirkungen unterschiedliche Biokohlen in Kombination mit oder ohne Gärrest und / oder Stickstoffdünger auf die Bodenchemie, Bodenbiologie und Wachstum, Entwicklung, Ertrag, Ertragsstruktur, Nährstoffe sowie Qualität von Nutzpflanzen haben. Außerdem wurden die Effekte unterschiedlicher Biokohlen auf die Wurzelmorphologie von Sommerweizen quantifiziert. Eine weitere Frage war, inwiefern Biokohlen Stickstoffquellen sorbieren. Es wurden ein Feldversuch und mehrere Gefäßversuche durchgeführt, um die Änderungen der Bodenchemie, den Einfluss auf die Bodenbiologie am Beispiel von Collembolen und die Pflanzenparameter zu bestimmen. Für die Wurzeluntersuchungen wurden Rhizoboxversuche durchgeführt und zur Quantifizierung der Stickstoffsorption ein in vitro Versuch angelegt. Die Ergebnisse der Feld- und Gefäßuntersuchungen zeigten, dass die Biokohlen die Bodeneigenschaften positiv beeinflussten. Die Biokohlen nahmen keinen konsistenten Einfluss auf die Erträge von Kulturpflanzen. Die Nährstoffgehalte der Kulturpflanzen konnten zum Teil positiv beeinflusst werden. Die Collembolenabundanzen zeigten sowohl in der Feldstudie als auch im Gefäßversuch keine signifikanten Unterschiede zwischen den getesteten Biokohlen. Hohe Mengen der fermentierten HTC-Biokohle führten zu negativen Wirkungen auf die Collembolenabundanz im Gefäßversuch. Die Rhizoboxversuche zeigten einen positiven Einfluss der Pyro-Biokohle auf die oberirdische und unterirdische Trockenmasse sowie die Wurzelmorphologie von Sommerweizen. Unterschiedliche Stickstoffquellen wurden von der HTC-Biokohle stärker sorbiert als von der Pyro-Biokohle. Generell lässt sich aus den differenzierten Wirkungen der Biokohlen weitere Forschung mit dem Fokus Boden ableiten. / Over the past few years the use of biochars in agriculture has gained more importance due to positive effects on carbon sequestration, soil improvement and increased plant growth. Therefore, the present work pursues the question which effects different biochars have in combination with or without digestate and / or nitrogen fertilizer on soil chemistry, soil biology and growth, development, yield, yield components, nutrients and quality of crops. In addition, the effects of different biochars on root morphology of spring wheat were quantified. Further to elucidate potential mechanisms underlying biochar effects on crops it was studied how biochars sorb various nitrogen sources. A field test and several pot experiments were conducted to determine the changes in soil chemistry, the impact on soil-dwelling Collembola and plant parameters. For the root studies rhizobox experiments were performed. To quantify the nitrogen sorption of biochars an in vitro experiment was conducted. The results of the field test and pot experiments showed that biochars positively affected soil chemical characteristics. However, yields of crops were not consistently affected by biochars. The nutrient content of crops were positively influenced to some extent. The abundance of Collembola was not significantly influenced by the biochars tested in the field study and in the pot experiment. High amounts of fermented HTC-biochar had negative effects on the abundance of Collembola in the pot experiment. Rhizobox experiments showed a positive influence of Pyro-biochar on the aboveground dry matter, belowground dry matter and root morphology (e.g. root length) of spring wheat. Amount and reversibility of nitrogen sorption was dependent on the type of biochar with HTC-biochar sorbing more nitrogen than Pyro- biochar. Generally it can be concluded that because of the different effects of biochars further research with a focus on soil is needed.

Thermo-stabilized lignin fibers from pH-fractionated softwood kraft lignin were carbonized to various temperatures during thermomechanical analysis (TMA) under static and increasing load and different rates of heating. The aim was to optimize the carbonization process to obtain suitable carbon fiber material with good mechanical strength potential (high tensile strength and high E-modulus). The carbon fibers were therefore mainly evaluated of mechanical strength in Dia-Stron uniaxial tensile testing. In addition, chemical composition, in terms of functional groups, and elemental (atomic) composition was studied in Fourier transform infrared spectroscopy (FTIR) and in energy-dispersive X-ray spectroscopy (EDS), respectively. The structure of carbon fibers was imaged in scanning electron microscope (SEM) and light microscopy. Thermogravimetrical analysis was performed on thermo-stabilized lignin fibers to evaluate the loss of mass and to calculate the stress-changes and diameter-changes that occur during carbonization. The TMA-analysis of the deformation showed, for thermo-stabilized lignin fibers, a characteristic behavior of contraction during carbonization. Carbonization temperatures above 1000°C seemed most efficient in terms of E-modulus and tensile strength whereas rate of heating did not matter considerably. The E-modulus for the fibers was improved significantly by slowly increasing the load during the carbonization. The tensile strength remained however unchanged. The FTIR-analysis indicated that many functional groups, mainly oxygen containing, dissociate from the lignin polymers during carbonization. The EDS supported this by showing that the oxygen content decreased. Accordingly, the relative carbon content increased passively to around 90% at 1000°C. Aromatic structures in the carbon fibers are thought to contribute to the mechanical strength and are likely formed during the carbonization. However, the FTIR result showed no evident signs that aromatic structures had been formed, possible due to some difficulties with the KBr-method. In the SEM and light microscopy imaging one could observe that porous formations on the surface of the fibers increased as the temperature increased in the carbonization. These formations may have affected the mechanical strength of the carbon fibers, mainly tensile strength. The carbonization process was optimized in the sense that any heating rate can be used. No restriction in production speed exists. The carbonization should be run to at least 1000°C to achieve maximum mechanical strength, both in E-modulus and tensile strength. To improve the E-modulus further, a slowly increasing load can be applied to the lignin fibers during carbonization. The earlier the force is applied, to counteract the lignin fiber contraction that occurs (namely around 300°C), the better. However, in terms of mechanical performance, the lignin carbon fibers are still far from practical use in the industry.

Soot is a carbonaceous materials produced as a result of incomplete combustion of fuels (gasoline, diesel, etc). At the present level of automobile technology, emission of soot from combustion in diesel engine appears to be an inevitability. The disadvantage in the diesel combustion is that it is not homogeneous throughout the cylinder. So the fuel-air ratio cannot be maintained constant throughout the flame zone and hence rich combustion zone leads to the formation of soot. Diesel engine combustion processes produce a large amount of soot, which is one of the major pollutant emissions of the exhaust systems. The fraction of combustion particulate, which is soot, is often estimated by finding the insoluble portion of the particulate. Hydrocarbons or other available molecules may also condense on or beads orbed by soot depending on the surrounding conditions. Other particulate matter constituents include partially burned fuel/lubricant oil bound water, wear metal and fuel derived sulfate. In diesel engine lubrication, soot has long been recognized as the major contaminant that is detrimental to engine lubrication, particularly in friction and wear. Different techniques for soot abatement have been investigated by researchers from the field of combustion and fuel. In spite of the large numbers of investigations of soot formation conducted till date, there is relatively little quantitative information is available about the mechanisms and governing rate processes. Some of the studies focused on the combustion chemistry of soot formation while some emphasized on engine design. On the other hand comparatively a few research works are coming out from the tribological point of view. Considering that internal combustion engines play such an important role in industry, investigative research of the parametric influences of particle size, agglomeration, oil viscosity, additives and surfactant as well as chemistry and electrical properties of particles on wear as well as into the wear mechanisms have not perhaps been as extensive as it is detrimental. Existence of a large numbers of variables in tribological contacts makes the situation very complex and difficult to analyze it quantitatively. In this complex scenario, where many opposed effects are playing their roles in soot tribology, the influence of the physical, structural and mechanical properties of soot on engine tribology has limited attention. We focus our study on one of the end effects of engine soot; friction and wear of the engine components. Since a diesel engine is not particularly suitable for use in a laboratory study of the fundamental processes and parameters of combustion due to its inherent difficulties on control and safety as well as data analysis uncertainty, so the most useful studies of soot fundamentals have emerged from studies of processes which have used simplified environments such as diffusion flames. We focus on soot tribology in steel-on-steel interaction in the presence of soot material suspended in relatively simple paraffinic hydrocarbons, hexadecane; with and without an additive. The physical, structural, chemical and mechanical properties of the particle and their changes as a function of tribological parameters are monitored throughout this study. Three type of soot are used in this work. Firstly, commercial grade carbon blacks has been used as soot simulant. Secondly, to enable controlled variations of the physical, mechanical, chemical and geometrical parameters of the particles, soot is generated in-situ by burning ethylene gas and the particles are extracted thermophoretically from different thermal zones of the flame. Thirdly, to establish the validity of the study, two types of diesel soots are extracted from an engine and studied. The objective is to use such an understanding to elucidate the basic mechanisms of friction and wear in the presence of soot which may limit the performance of a diesel engine. From our study we find that these soots have widely different morphologies, crystallographic orders and reactivity. At tribological contact the soot agglomerates fragment to primary level particles. The physical and chemical properties of such particles determine the friction between and wear of mating components. If the soot is strongly graphitic, the friction and wear are moderate. If the soot is made of chemically active organic groups, the friction and wear are high. The hardness, friction and resistance to material removal of the soot collected near the flame tip and diesel soot are found to be high compared to the other types of soot. Besides, the high hardness, irregular primary particle shape, large inter-particle adhesion leading to agglomeration and more abrasive nature of diesel soot influence the metal wear adversely. This trend of soot tribology is profound when these soots are suitably dispersed in the oil by the addition of dispersants, in our case it is polyisobutylene succinimide. Different functional groups present on the soot surface play important role in defining the interaction between surrounding medium and contacts which, in turn define the contact conditions, particle/agglomerate behavior and soot tribology. Finally, agglomeration is simulated using the features of a dissipative particle dynamics package as the simulation technique. Simulations are performed on a sizeable number of particles to observe agglomeration behavior, on simple environment, in future which can be further extended.

The thesis discusses the use of biomass for electricity island operation. The first chapter explains the concept of biomass and its distribution. It also shows the potential and availability of biomass. The second chapter describes the transformation of biomass into a suitable fuel form. The third to fifth chapter describes the conversion of biomass as a fuel into electrical energy through combustion, Stirling and steam engine. In these chapters there are brought the following parameters and prices of these motors and single-phase and three-phase alternators that can be connected to these engines. Other chapters describe the production of electricity in line with consumption, where the cost per hour to run engines for the various types of fuel and price of the electricity produced in kilowatt hours is calculated. In the last chapter of the thesis there is described the possibility of accumulation of electrical energy.

Nano-scaled carbons were produced by thermal treatment of pine wood chips and bio-char. The influence of temperature, heating rate, pyrolysis time, and type and flow rate of purge gas on the production of nano-carbons was investigated. Using TEM and SEM, different carbon-based nanomaterials were observed in the prepared samples. The effect of metal ion doping on the bio-char was also investigated. Highly functionalized nano carbonaceous materials were synthesized by low temperature hydrothermal carbonization (HTC) using glucose, sucrose, xylose, and cellulose. Carbon-encapsulated iron (Fe@C) core-shell particles were also synthesized by the HTC method and used as catalyst for Fischer-Tropsch synthesis to produce liquid hydrocarbons from syngas; it showed excellent activity. Nano-structured Co-Mo carbides over several nano-sized carbon materials were prepared using the carbothermal reduction and carbothermal hydrogen reduction methods. Nano-structured Co-Mo carbides derived from Vulcan® XC-72 were used as the catalyst to produce higher alcohols.

Many environmental crises are threatening to collapse human societies, but also life on the Earth as we may know. Climate change due to anthropogenic global emissions is one of the main issues, but also soil degradation, and the management of the enormous amount of organic wastes that are harmfully released into the environment by human activities. On the one hand, direct spreading of biowastes onto the land is often limited due to eutrophication or pollution by toxic compounds. On the other hands, these biomasses may contain nutrients, such as phosphorus (listed as a critical raw material) and nitrogen, which could be recovered to sustain the high demand in expensive soil amendments and fertilizers. Thus, finding new solution to close the loop towards circular economy and sustainable processes is crucial, nowadays, to convert the global trends and restore the delicate equilibrium in the water-food-energy nexus, with soil ‘under special surveillance’. In this framework, many researchers are focusing their attention on hydrothermal carbonization (HTC) as a possible candidate, in particular to treat moist biowastes and obtain useful solid (hydrochar) and liquid (HTC liquor) products. Nutrients contained in biowastes are sensitive to HTC process parameters and initial feedstock properties, thus it is crucial to analyze their distribution and (im)mobilization among the HTC products for their reuse in soil. On the other hand, since some organic compounds are generated during the thermochemical process, which may be responsible for toxicity to plants and other organisms, analysis of their possible toxicity towards the biosphere becomes crucial before implementation at a large scale. This thesis collects our efforts to explore new processes and deepen the knowledge about the possibility to produce amendments suitable for soil application from hydrochar. The core is from a process engineering perspective, focusing on the production phase and the characterization of the products, never forgetting any possible limits or the implications on ecotoxicological issues. In the first part of the thesis, ‘How to make hydrochar a soil amendment?’ is the main question. Based on few pioneer studies about composting of hydrochar, we assessed a complete analysis of hydrochar co-compost, produced from the 25-day aerobic stabilization of digestate of organic fraction of municipal solid waste, together with a fraction of its hydrochar, and green waste. Under the umbrella of C2Land project (funded by The European Institute of Innovation & Technology -EIT), we produced this new amendment in specifically designed bioreactors, then we characterized the products from the point of view of physico-chemical properties, nutrients distribution, toxicity to plants and mammalian cells. We are confident that the crucial result of toxicity removal from hydrochar through composting will attract the interest of many stakeholders, since implementing HTC in anaerobic/aerobic plants is almost ready to be applied at a large scale. Moreover, an experimental campaign performed at the University of Leeds further explored the effect of some other post-treatments on hydrochar composition and phytotoxicity, depending on the initial feedstocks (manure, sewage digestate, water hyacinth, and grass). The second part of the thesis was dedicated to nutrients recovery, necessary when some harmful matrixes - such as the municipal sewage sludge digestate - are not allowed to be reused for agricultural purposes, due to law limitations or pollution issues. In this case, nutrients recovery (N, P) could be achieved chemically, via HTC and struvite precipitation, being struvite recognized as a good fertilizer. Firstly, we performed a techno-economic assessment of the implementation at a district level of HTC-centered sewage sludge management. The mass reduction of waste streams may have some important effects on transportation costs, while the recirculation of HTC liquor back to the anaerobic digestors can imply more biomethane production with increased revenues. A mass balance for the potential of N and P recovery through struvite precipitation in the centralized facility was also assessed. Secondly, a near-zero waste treatment process for municipal sewage sludge via HTC was designed according to the available literature and preliminarily analyzed at lab level. The fractionation of the different types of phosphorus was analyzed through the STM-P protocol before and after HTC, confirming the mineralization of organic phosphorus during the process. Citric acid was validated as a good green solvent for phosphorus extraction and high-quality struvite precipitation, even if the process was not still optimized in terms of yields. Future works may identify the best process parameters for final metal recovery from liquid byproducts in order to internally recirculate them back to water line, and to characterize the leached hydrochar as purified renewable fuel or soil amendment. Thus, the proof-of-concept chain would be confirmed and could be applied to the sustainable HTC-centered biorefineries of the future.

Die kürzliche globale COVID-19-Pandemie hat deutlich gezeigt, dass hohe medizinische Kosten eine große Herausforderung für unser Gesundheitssystem darstellen. Daher besteht eine wachsende Nachfrage nach personalisierten tragbaren Geräten zur kontinuierlichen Überwachung des Gesundheitszustands von Menschen durch nicht-invasive Erfassung physiologischer Signale. Diese Dissertation fasst die Forschung zur Laserkarbonisierung als Werkzeug für die Synthese flexibler Gassensoren zusammen und präsentiert die Arbeit in vier Teilen. Der erste Teil stellt ein integriertes zweistufiges Verfahren zur Herstellung von laserstrukturiertem (Stickstoff-dotiertem) Kohlenstoff (LP-NC) ausgehend von molekularen Vorstufen vor. Der zweite Teil demonstriert die Herstellung eines flexiblen Sensors für die Kohlendioxid Erfassung basierend auf der Laserumwandlung einer Adenin-basierten Primärtinte. Die unidirektionale Energieeinwirkung kombiniert mit der tiefenabhängigen Abschwächung des Laserstrahls ergibt eine neuartige geschichtete Sensorheterostruktur mit porösen Transducer- und aktiven Sensorschichten. Dieser auf molekularen Vorläufern basierende Laserkarbonisierungsprozess ermöglicht eine selektive Modifikation der Eigenschaften von gedruckten Kohlenstoffmaterialien. Im dritten Teil wird gezeigt, dass die Imprägnierung von LP-NC mit Molybdäncarbid Nanopartikeln die Ladungsträgerdichte verändert, was wiederum die Empfindlichkeit von LP-NC gegenüber gasförmigen Analyten erhöht. Der letzte Teil erläutert, dass die Leitfähigkeit und die Oberflächeneigenschaften von LP-NC verändert werden können, indem der Originaltinte unterschiedliche Konzentrationen von Zinknitrat zugesetzt werden, um die selektiven Elemente des Sensormaterials zu verändern. Basierend auf diesen Faktoren zeigte die hergestellte LP-NC-basierte Sensorplattform in dieser Studie eine hohe Empfindlichkeit und Selektivität für verschiedene flüchtige organische Verbindungen. / The recent global COVID-19 pandemic clearly displayed that the high costs of medical care on top of an aging population bring great challenges to our health systems. As a result, the demand for personalized wearable devices to continuously monitor the health status of individuals by non-invasive detection of physiological signals, thereby providing sufficient information for health monitoring and even preliminary medical diagnosis, is growing. This dissertation summarizes my research on laser-carbonization as a tool for the synthesis of functional materials for flexible gas sensors. The whole work is divided into four parts. The first part presents an integrated two-step approach starting from molecular precursor to prepare laser-patterned (nitrogen-doped) carbon (LP-NC). The second part shows the fabrication of a flexible LP-NC sensor architecture for room-temperature sensing of carbon dioxide via laser conversion of an adenine-based primary ink. By the unidirectional energy impact in conjunction with depth-dependent attenuation of the laser beam, a novel layered sensor heterostructure with a porous transducer and an active sensor layer is formed. This molecular precursor-based laser carbonization method enables the modification of printed carbon materials. In the third part, it is shown that impregnation of LP-NC with molybdenum carbide nanoparticle alters the charge carrier density, which, in turn, increases the sensitivity of LP-NC towards gaseous analytes. The last part explains that the electrical conductivity and surface properties of LP-NC can be modified by adding different concentrations of zinc nitrate into the primary ink to add selectivity elements to the sensor materials. Based on these factors, the LP-NC-based sensor platforms prepared in this study exhibited high sensitivity and selectivity for different volatile organic compounds.

The study set out to understand and demonstrate the role the ICT sector could play as a critical enabler in the transition and progress towards an energy– efficient, low carbon economy. More specifically, the study of sustaining ICT for sustainability has twofold intent: (2) to investigate the direct footprint of ICT sector and explore how it can be tackled through adopting sustainable design–based solutions; and (2) to highlight the enabling potential of ICT sector to mitigate climate change and massively improve energy efficiency across the economy, identifying and quantifying the global ICT impacts and opportunities in the context of energy and carbon emissions savings. To achieve the aim of this study, a pertinent and extensive literature review covering theoretical, empirical, and critical scholarship was performed to investigate the phenomenon. The study draws on a variety of sources to survey the unsustainability of ICT sector pertaining to energy–intensive consumption and explore potential solutions through espousing environmental design practice, and also to examine the role of ICT in delivering energy–efficient solutions through its products and services. Validity was ensured through using quality academic and industry literature as well as relevant studies carried out by a range of eminent researchers, experts, and stakeholders (i.e. NGOs, research centers). Findings highlight the unsustainability of ICT sector regarding energy– intensive consumption and concomitant GHG emissions associated with its products and services. Of the whole lifecycle, the use phase of ICT is the most critical. Data centers and telecom networks devour energy. Planned obsolescence entrenched in software design shorten upgrade cycle, which makes software utilities a planet killer as to energy consumption. Alternative sustainable design–based solutions entail using renewable energy and most efficient energy required over ICT’s life cycle – de–carbonization strategy. Also, digitization is an effective strategy for ICT sector to slash energy use per unit. To reduce the footprint of data centers and telecom networks, design solutions vary from hardware and software to technological improvements. Designing out built–in obsolescence in software technology is a key factor in the energy equation. As for the enabling role of ICT, the findings are highly illuminating. The ICT sector must step up its efforts in reducing its direct footprint in order to claim a leadership role in an energy–efficient, low carbon economy. Although the ICT sector’s own emissions will increase because of global growing demand for its products and services, the real gains will come from its enabling potential to yield substantial energy efficiency improvements and emissions reductions across the economy. The sheer scale of the climate change challenge presents smart development mitigation opportunities for ICT sector to deliver environmentally sustainable solutions. The largest identified opportunities are: dematerialization; intelligent transport and logistics; intelligent buildings; smart power supply; and efficient industrial processes and systems. This study provides a novel approach into sustainable design in ICT, underlining unsustainable design practices in ICT sector. Review of the literature makes an advance on extant reviews by highlighting the synergic relationship between ICT design, sustainability, and the economy. / +46 704 35 21 35

This study endeavors to investigate the negative environmental impacts of the prevailing ICT design approaches and to explore some potential remedies for ICT design unsustainability from environmental and corporate sustainability perspectives. More specifically, it aims to spotlight key environmental issues related to ICT design, including resource depletion; GHG emissions resulting from energy-intensive consumption; toxic waste disposal; and hazardous chemicals use; and also to shed light on how alternative design solutions can be devised based on environmental sustainability principles to achieve the goals of sustainable technologies. The study highlights the relationship between ICT design and sustainability and how they can symbiotically affect one another. To achieve the aim of this study, an examination was performed through an extensive literature review covering empirical, theoretical, and critical scholarship. The study draws on a variety of sources to survey the negative environmental impacts of the current mainstream ICT design approach and review the potential remedies for unsustainability of ICT design. For theory, central themes were selected for review given the synergy and integration between them as to the topic under investigation. They include: design issues; design science; design research framework for ICT; sustainability; corporate sustainability; and design and sustainability. Findings highlight the unsustainability of the current mainstream ICT design approach. Key environmental issues for consideration include: resource depletion through extracting huge amounts of material and scarce elements; energy-intensive consumption and GHG emissions, especially from ICT use phase; toxic waste disposal; and hazardous substances use. Potential remedies for ICT design unsustainability include dematerialization as an effective strategy to minimize resources depletion, de-carbonization to cut energy consumption through using efficient energy required over life cycle and renewable energy; recyclability through design with life cycle thinking (LCT) and extending ICT equipment’s operational life through reuse; mitigating hazardous chemicals through green design - low or non-noxious/less hazardous products. As to solving data center dilemma, design solutions vary from hardware and software to technological improvements and adjustments. Furthermore, corporate sustainability can be a strategic model for ICT sector to respond to environmental issues, including those associated with unsustainable ICT design. In the same vein, through adopting corporate sustainability, ICT-enabled organizations can rationalize energy usage to reduce GHG emissions, and thereby alleviating global warming. This study provides a novel approach to sustainable ICT design, highlighting unsustainability of its current mainstream practices. Review of the literature makes an advance on extant reviews of the literature by highlighting the symbiotic relationship between ICT design and environmental sustainability from both research and practice perspectives. This study adds to the body of knowledge and previous endeavours in research of ICT and sustainability. Overall, it endeavours to present contributions and avenues for further theoretical and empirical research and development. / +46704352135/+212662815009

This report travels through multiple disciplines to seek innovative and sustainable energy solutions for wastewater treatment plants. The first subject is a report about increased global temperatures and an over-exploitation of natural resources that threatens ecosystems worldwide. The situation is urgent where the current trend is a 2°C increase of global temperatures already in 2040. Furthermore, the energy-land nexus becomes increasingly apparent where the world is going from a dependence on easily accessible fossil resources to renewables limited by land allocation. A direction of the required transition is suggested where all actors of the society must contribute to quickly construct a new carbon-neutral resource and energy system. Wastewater treatment is as required today as it is in the future, but it may move towards a more emphasized role where resource management and energy recovery will be increasingly important. This report is a master’s thesis in energy engineering with an ambition to provide some clues, with a focus on energy, to how wastewater treatment plants can be successfully integrated within the future society. A background check is conducted in the cross section between science, society, politics and wastewater treatment. Above this, a layer of technological insights is applied, from where accessible energy pathways can be identified and evaluated. A not so distant step for wastewater treatment plants would be to absorb surplus renewable electricity and store it in chemical storage mediums, since biogas is already commonly produced and many times also refined to vehicle fuel. Such extra steps could be excellent ways of improving the integration of wastewater treatment plants into the society. New and innovative electric grid-connected energy storage technologies are required when large synchronous electric generators are being replaced by ‘smaller’ wind turbines and solar cells which are intermittent (variable) by nature. A transition of the society requires energy storages, balancing of electric grids, waste-resource utilization, energy efficiency measures etcetera… This interdisciplinary approach aims to identify relevant energy technologies for wastewater treatment plants that could represent decisive steps towards sustainability.