Bioethanol from Lignocellulosic Biomass: Current Findings Determine Research Priorities

“Second generation” bioethanol, with lignocellulose material as feedstock, is a promising alternative for first generation bioethanol. This paper provides an overview of the current status and reveals the bottlenecks that hamper its implementation. The current literature specifies a conversion of biomass to bioethanol of 30 to ~50% only. Novel processes increase the conversion yield to about 92% of the theoretical yield. New combined processes reduce both the number of operational steps and the production of inhibitors. Recent advances in genetically engineered microorganisms are promising for higher alcohol tolerance and conversion efficiency. By combining advanced systems and by intensive additional research to eliminate current bottlenecks, second generation bioethanol could surpass the traditional first generation processes

Reviewing the thermo-chemical recycling of waste polyurethane foam

The worldwide production of polymeric foam materials is growing due to their advantageous properties of light weight, high thermal insulation, good strength, resistance and rigidity. Society creates ever increasing amounts of poly-urethane (PU) waste. A major part of this waste can be recycled or recovered in order to be put into further use. The PU industry is committed to assist and play its part in the process. The recycling and recovery of PU foam cover a range of mechanical, physical, chemical and thermo-chemical processes. In addition to the well- documented mechanical and chemical processing options, thermo-chemical treatments are important either as ultimate disposal (incineration) or towards feedstock recovery, leading to different products according to the thermal conditions of the treatment. The review focuses on these thermo-chemical and thermal processes. As far as pyrolysis is concerned, TDI and mostly polyol can be recovered. The highest recovery yields of TDI and polyols occur at low temperatures (150–200 ◦C). It is however clear from literature that pure feedstock will not be produced, and that a further upgrading of the condensate will be needed, together with a thermal or alternative treatment of the non-condensables. Gasification towards syngas has been studied on a larger and industrial scale. Its application would need the location of the PU treatment plant close to a chemical plant, if the syngas is to be valorized or considered in conjunction with a gas-fired CHP plant. Incineration has been studied mostly in a co- firing scheme. Potentially toxic emissions from PU combustion can be catered for by the common flue gas cleaning behind the incineration itself, making this solution less evident as a stand-alone option: the combination with other wastes (such as municipal solid waste) in MSWI′s seems the indicated route to go

Scientometric analysis and scientific trends on biochar application as soil amendment

This manuscript presents a scientometric analysis on the studies performed on the application of biochar for soil amendment in order to investigate the research and developments in this field and to identify the existing gaps to provide recommendations for future studies. A total of 2982 bibliographic records were retrieved from the Web of Science (WoS) database using appropriate sets of keywords, and these were analyzed based on the criteria of authors, publishing journals, citations received, contributing countries, institution, and categories in research and development. Based on these data, progress of research was mapped to identify the scientific status, such as current scientific and technological trends as well as the knowledge gaps. The majority of scientific developments started in the early 2000′s and accelerated considerably after 2014. China and USA are the leading countries in the application of biochar for the treatment of soils. Among the active journals, “Plant and Soil” has received the highest number of citations. This study attempts for a comprehensive discussion and understanding on scientific advances as well as the progress made, especially in recent years.publishe

Bio-energy Carriers as Back-up Fuel in Hybrid Solar Power Plants

Electricity from concentrated solar power (CSP) plants, gains an increasing interest and importance. To fully match the supply-demand principle, CSP processes include a thermal energy storage and back-up fuel supply. Novel CSP concepts are needed with specific targets of increased efficiency and reliability, and of reduced CAPEX and OPEX. The use of particle suspensions offers significant advantages since applicable in all sub-sections of the complete CSP as heat carrier from the receiver, to the heat storage, and ultimately to the power block. The use of particles in the steam generation (power block) is a common fluidized bed boiler technology. This paper will present the entire particle-based concept, while also discussing the potential to use biomass-based energy carriers as back-up heat supply. Process data and expected effects on the process economy of the system will be discussed

Reviewing the potential of bio-hydrogen production by fermentation

Hydrogen is a common reactant in the petro-chemical industry and moreover recognized as a potential fuel within the next 20 years. The production of hydrogen from biomass and carbohydrate feedstock, though undoubtedly desirable and favored, is still at the level of laboratory or pilot scale. The present work reviews the current researched pathways. Different types of carbohydrates, and waste biomass are identified as feedstock for the fermentative bio-hydrogen production. Although all techniques suffer from drawbacks of a low H2 yield and the production of a liquid waste stream rich in VFAs that needs further treatment, the technical advances foster the commercial utilization. Bacterial strains capable of high hydrogen yield are assessed, together with advanced techniques of co-culture fermentation and metabolic engineering. Residual VFAs can be converted. The review provides an insight on how fermentation can be conducted for a wide spectrum of feedstock and how fermentation effluent can be valorized by integrating fermentation with other systems, leading to an improved industrial potential of the technique. To boost the fermentation potential, additional research should firstly target its demonstration on pilot or industrial scale to prove the process efficiency, production costs and method reliability. It should secondly focus on optimizing the micro-organism functionality, and should finally develop and demonstrate a viable valorization of the residual VFA-rich waste streams

11CO2 positron emission imaging reveals the in-situ gas concentration profile as function of time and position in opaque gas-solid contacting systems

The in situ analysis of industrial processes, mostly conducted in opaque equipment is difficult. Whereas previously the positron emission technique was successfully applied to study the flow and mixing in gas-solid and liquid-solid systems using radio-active tracer particles, research on imaging a radio- active tracer gas is scarce. The present paper demonstrates the use of a fully three-dimensional (3D) Positron Emission Tomography (PET) in imaging the adsorption of 11CO2 tracer gas, while validating the measurement by conventional exit gas analysis. It will be demonstrated that PET can be used to measure the kinetics of high-pressure CO2 adsorption in situ, including the essential breakthrough and mass transfer zone characteristics. Such high-pressure operation is characteristic of pre-combustion CO2 capturing processes. It is expected that this work will foster further studies of gas-solid systems of adsorption, gas-solid catalysis, gas-solid hydrodynamics, and processes where the gas-solid interaction is of primary importance

On the ‘bio-way’ to sustainability: Novel fermentation pathways to produce fuels and chemicals

The search for novel technologies to generate renewable chemicals and fuels has attracted large attention in recent years, mainly because of the necessity to develop sustainable alternatives for fossil fuel based processes. The conversion of biomass and organic wastes by fermentation processes is of growing importance. Whereas in the past microbial conversions were limited to ‘simple molecules’ like bio-ethanol, methane (via anaerobic digestion) or hydrogen production, the application of microbial resource management paves the way towards the fermentative production of more complex and value added organic molecules, which can be used as a feedstock in chemical processes or as liquid fuel. In both cases, they can replace fossil fuels. Microbial resource management aims to control and steer the capabilities of complex communities by operating the bioreactors in such a way to promote the development of a microbial community that accommodates the desired functional process. The application of molecular biology and the advent of culture-independent molecular techniques like high throughput DNA sequencing methods has caused a revolution in the capabilities to practice microbial resource management, opening the door to engineer communities with superior functions. Currently, bioreactors exploiting natural microbial communities for bioenergy production are commonly operated based on bulk parameters and empirical expert knowledge. The composition of the fermentation mixture in the bioreactor often remains a black box. The ability of current molecular and cell based methods to derive structurefunction-relationships, that is, correlations between the microbial community structure and dynamics, and the reactor performance, are considered as key-criteria for the future development of biofuel production. This paper will review the current state-of-the art in fermentation technology and will analyse the current trends in microbial resource management. Examples of applications will be presented with a focus on integration with process measurements to improve system performance.status: publishe

Anaerobic digestion as a key technology in bio-energy production: Current achievements and challenges

Anaerobic digestion has been applied for many decades for the treatment of organic wastes like manure, wastewater sludge and crop residues. Whereas these streams were considered as a nuisance in the past, nowadays, emphasis lies on resource recovery. These wastes are, indeed, providing an important source of renewable energy. Therefore, there is a renewed interest in anaerobic digestion as a technology for sustainable renewable energy production. Also, anaerobic digestion plays a central role in a biorefinery concept. All over Europe, the application of anaerobic digestion is steadily growing, although there are major differences between individual countries on the adaptation of this technology. Because of the high complexity of the degradation mechanisms occurring, digesters are currently still treated as black box systems, and are mainly designed by rules of thumb. Much research is carried out to gain additional insight to be used for process optimisation. Some major research topics include (i) reducing the long retention times in the digester, (ii) increasing the (limited) biogas production efficiency (currently merely ca. 50% of the organic matter in the waste stream is converted to biogas), (iii) increasing the methane content in the biogas (hereby increasing its heating value), (iv) opening the way to include lignocellulosic materials as feedstock for digestion and (v) adapting the digestion process to cope with inhibition by recalcitrant LCFA (for high lipid containing feeds) and ammonia (for high nitrogen containing feeds). The aim of this paper is to provide an overview of the current status on anaerobic digestion research. First, an overview on the application of the technology in European countries will be provided, and it potential will be highlighted. Next, the main trends in anaerobic digestion research will be critically discussed. Highly innovative research topics in anaerobic digestion include (i) stimulation of the anaerobic micro-organisms by process technological innovations (e.g. application of microwaves and ultrasonic fields), (ii) integration of knowledge on microbial community composition and development in steering anaerobic digestion and (iii) advanced mathematical modelling for simulation and control of the digestion. Current achievements will be highlighted and future opportunities will be identified. The main aspects will be illustrated by some examples of state-of-the-art research in the respective domains.status: publishe