Pyrolysis of mixed engineering plastics: Economic challenges for automotive plastic waste

Chemical recycling of complex plastic waste via pyrolysis can reduce fossil resource dependence of the plastics value chain and greenhouse gas emissions. However, economic viability is crucial for its implementation, especially considering challenging waste streams with high shares of engineering plastics that have lower pyrolysis product quality than standard thermoplastics waste. Thus, this study conducts a techno-economic assessment determining the profitability factors of pyrolysis plants for automotive plastic waste in Germany including different plant capacities and calculating cost-covering minimum sales prices for the resulting pyrolysis oil. Main findings are that due to economies of scale, the cost-covering minimum sales prices vary between 1182 €/Mg pyrolysis oil (3750 Mg input/year) and 418 €/Mg pyrolysis oil (100,000 Mg input/year). The pyrolysis technology employed must be robust and scalable to realize these economies of scale. Large plant capacities face challenges such as feedstock availability at reasonable costs, constant feedstock quality, and pyrolysis oil quality, affecting pyrolysis oil pricing. Due to the limited yield and quality of pyrolysis oil produced from these technically demanding feedstocks, policy implications are that additional revenue streams such as gate fees or subsidies that are essential to ensure a positive business case are necessary. Depending on the assessed plant capacity, additional revenues between 720 and 59 €/Mg pyrolysis oil should be realized to be competitive with the price of the reference product heavy fuel oil. Otherwise, the environmental potential of this technology cannot be exploited.

A Novel Plenoptic Camera-Based Measurement System for the Investigation into Flight and Combustion Behavior of Refuse-Derived Fuel Particles

In the past several decades, refuse-derived fuels (RDFs) have been widely applied in industrial combustion processes, for instance, in cement production. Since RDF is composed of various waste fractions with complex shapes, its flight and combustion behaviors can be relatively complicated. In this paper, we present a novel plenoptic camera-based spatial measurement system that uses image processing approaches to determine the dwell time, the space-sliced velocity in the depth direction, and the ignition time of various applied RDF fractions based on the obtained images. The image processing approach follows the concept of tracking-by-detection and includes a novel combined detection method, a 2.5D multiple particle tracking algorithm, and a postprocessing framework to tackle the issues in the initial tracking results. The thereby obtained complete spatial fuel trajectories enable the analysis of the flight behaviors elaborated in the paper. The acquired particles' properties (duration, velocity, and ignition time) reversely prove the availability and applicability of the developed measurement system. The adequacy and accuracy of the proposed novel measurement system are validated by the experiments of detecting and tracking burning and nonburning fuel particles in a rotary kiln. This new measurement system and the provided experimental results can benefit a better understanding of the RDF's combustion for future research.

Exploring the synergistic effects of biochar and arbuscular mycorrhizal fungi on phosphorus acquisition in tomato plants by using gene expression analyses

Arbuscular mycorrhizal (AM) fungi are symbiotic organisms that contribute significantly to plant mineral nutrition, mainly phosphate. However, their benefits are constricted by the availability of phosphate in the soil, and thus they are recalcitrant as amendment in highly fertilized soils. Biochars are by-products of the pyrolysis of biomass in the absence of oxygen. They can improve soil properties and act as a source of nutrients for plants. However, depending on their origin, the final composition of biochars is extremely variable and thus, their efficiency unpredictable. In order to gain mechanistic insights into how the combined application of biochars and AM fungi contribute to plant phosphate nutrition and growth, we used gene expression analyses of key symbiotic marker genes. We compared for this analysis two biochars originated from very different feedstocks (chicken manure and wheat straw) on tomato plants with or without the AM fungus Rhizophagus irregularis. Our results show that the synergy between AM fungi and biochars as P biofertilizers is greatly governed by the origin of the biochar that determines the speed at which phosphate is released to the soil and absorbed by the plant. Thus, chicken manure biochar quickly impacted on plant growth by readily releasing P, but it turned out detrimental for symbiosis formation, decreasing colonization levels and expression of key symbiotic plant marker genes such as SlPT4 or SlFatM. In contrast, wheat straw biochar was inferior at improving plant growth but stimulated the establishment of the symbiosis, producing plants with the same concentration of phosphate as those with the chicken manure. Taken together, slow P releasing biochars from plant residues appears to be a more promising amendment for long terms experiments in which biofertilizers such as AM fungi are considered. Furthermore, our results indicate that implementing plant transcriptomic analyses might help to mechanistically dissect and better understand the effects of biochars on plant growth in different scenarios.

Comparing the Toxicological Responses of Pulmonary Air-Liquid Interface Models upon Exposure to Differentially Treated Carbon Fibers

In recent years, the use of carbon fibers (CFs) in various sectors of industry has been increasing. Despite the similarity of CF degradation products to other toxicologically relevant materials such as asbestos fibers and carbon nanotubes, a detailed toxicological evaluation of this class of material has yet to be performed. In this work, we exposed advanced air-liquid interface cell culture models of the human lung to CF. To simulate different stresses applied to CF throughout their life cycle, they were either mechanically (mCF) or thermo-mechanically pre-treated (tmCF). Different aspects of inhalation toxicity as well as their possible time-dependency were monitored. mCFs were found to induce a moderate inflammatory response, whereas tmCF elicited stronger inflammatory as well as apoptotic effects. Furthermore, thermal treatment changed the surface properties of the CF resulting in a presumed adhesion of the cells to the fiber fragments and subsequent cell loss. Triple-cultures encompassing epithelial, macrophage, and fibroblast cells stood out with an exceptionally high inflammatory response. Only a weak genotoxic effect was detected in the form of DNA strand breaks in mono- and co-cultures, with triple-cultures presenting a possible secondary genotoxicity. This work establishes CF fragments as a potentially harmful material and emphasizes the necessity of further toxicological assessment of existing and upcoming advanced CF-containing materials.

Recycling of polystyrene-based external thermal insulation composite systems - Application of combined mechanical and chemical recycling

The material recycling of complex waste streams such as external thermal insulation composite systems (ETICS) is challenging, which is why their recycling in the sense of a circular economy is currently hardly established. Therefore, the combined mechanical and thermochemical recycling of ETICS based on expanded polystyrene (EPS) is investigated experimentally and by simulating full process chains in order to evaluate circular economy opportunities. Model ETICS as example for building and construction waste is pretreated mechanically, followed by either pyrolysis and / or gasification steps, and full mass and energy balances are derived. By the combined recycling, inorganic compounds can be separated to a large extent allowing a pre-concentrate generation. The plastic-rich pre-concentrate is converted into either pyrolysis oil with a high styrene monomer content of 51 wt% or to synthesis gas in the subsequent thermochemical conversions. The holistic approach enables a high carbon recycling rate between 53 and 68 wt%. In addition, the investigation reveals technology limitations and opportunities to be further developed and optimized.

Thermal treatment of carbon-fibre-reinforced polymers (Part 2: Energy recovery and feedstock recycling)

The use of carbon fibre (CF)-reinforced plastics has grown significantly in recent years, and new areas of application have been and are being developed. As a result, the amount of non-recyclable waste containing CF is also rising. There are currently no treatment methods for this type of waste. Within this project different approaches for the treatment of waste containing CF were investigated. Main subject of the research project were large-scale investigations on treatment possibilities and limits of waste containing CF in high temperature processes, with focus on the investigation of process-specific residues and possible fibre emission. The results showed that the two conventional thermal waste treatment concepts with grate and rotary kiln firing systems are not suitable for a complete oxidation of CFs due to the insufficient process conditions (temperature and dwell time). The CFs were mainly discharged via the bottom ash/slag. Due to the partial decomposition during thermal treatment, World Health Organization (WHO) fibres occurred in low concentrations. The tests run in the cement kiln plant have shown the necessity of comminution for waste containing CF. With respect to the short testing times and moderate quantities of inserted CF, a final evaluation of the suitability of this disposal path was not possible. The use of specially processed waste containing CF (carbon-fibre-reinforced plastic (CFRP) pellets) as a carbon substitute in calcium carbide production led to high carbon conversion rates. In the unburned furnace dust, which is marketed as a by-product of the process, CFs in relevant quantities could be detected.

Agglomeration State of Titanium-Dioxide (TiO2) Nanomaterials Influences the Dose Deposition and Cytotoxic Responses in Human Bronchial Epithelial Cells at the Air-Liquid Interface

Extensive production and use of nanomaterials (NMs), such as titanium dioxide (TiO2), raises concern regarding their potential adverse effects to humans. While considerable efforts have been made to assess the safety of TiO2 NMs using in vitro and in vivo studies, results obtained to date are unreliable, possibly due to the dynamic agglomeration behavior of TiO2 NMs. Moreover, agglomerates are of prime importance in occupational exposure scenarios, but their toxicological relevance remains poorly understood. Therefore, the aim of this study was to investigate the potential pulmonary effects induced by TiO2 agglomerates of different sizes at the air-liquid interface (ALI), which is more realistic in terms of inhalation exposure, and compare it to results previously obtained under submerged conditions. A nano-TiO2 (17 nm) and a non-nano TiO2 (117 nm) was selected for this study. Stable stock dispersions of small agglomerates and their respective larger counterparts of each TiO2 particles were prepared, and human bronchial epithelial (HBE) cells were exposed to different doses of aerosolized TiO2 agglomerates at the ALI. At the end of 4h exposure, cytotoxicity, glutathione depletion, and DNA damage were evaluated. Our results indicate that dose deposition and the toxic potential in HBE cells are influenced by agglomeration and exposure via the ALI induces different cellular responses than in submerged systems. We conclude that the agglomeration state is crucial in the assessment of pulmonary effects of NMs.

A novel TEM grid sampler for airborne particles to measure the cell culture surface dose

The applied surface dose is a key parameter for the measurement of toxic effects of airborne particles by air liquid interface exposure of human lung cells. Besides online measurement of the deposited particle mass by quartz crystal microbalance frequently other dose metrics such as particle size distribution, surface and agglomeration state are required. These particle properties and their spatial distribution can be determined by digital processing of micrographs obtained by transmission electron microscopy (TEM). Here, we report the development and characterization of a novel holder for film coated TEM copper grids, which allows for sampling under identical geometric and ambient conditions as in a cell culture chamber. The sample holder avoids artefacts by reliable grounding of the grids and improves handling of the grids to prevent damage of the sensitive film. This sample holder is applied during exposure experiments with titanium dioxide nanoparticles. The measured dose of 0.2 µg/cm² corresponds well to the mass loading signal of the quartz crystal microbalance. Additionally, the spatial distribution of particles on the sampling surface shows a good homogeneity of deposition. This novel sampling method allows verifying other dosimetry methods and gives additional information about particle properties and homogeneity of the dose.

Waste incineration of Polytetrafluoroethylene (PTFE) to evaluate potential formation of per- and Poly-Fluorinated Alkyl Substances (PFAS) in flue gas

In recent years, concerns over some per- and polyfluorinated alkyl substances (PFAS) have grown steadily. PFAS are a large group of chemical substances with widely differing properties. While one class of PFAS, fluoropolymers, have been demonstrated to meet the OECD criteria for polymers of low concern during the in use phase of their lifecycle, questions remain regarding waste handling at the end of useful life for products containing fluoropolymers. To show that polytetrafluoroethylene (PTFE) can be almost fully transformed into fluorine (F) (as hydrofluoric acid (HF)) and to study the possible generation of low molecular weight per- and polyfluorinated alkyl substances (PFAS), PTFE combustion under typical waste incineration conditions at the BRENDA (German acronym for "Brennkammer mit Dampfkessel") pilot plant at Karlsruhe Institute of Technology (KIT) was investigated. Results indicate that, within procedural quantitation limits, no statistically significant evidence was found that the PFAS studied were created during the incineration of PTFE. Therefore, municipal incineration of PTFE using best available technologies (BAT) is not a significant source of the studied PFAS and should be considered an acceptable form of waste treatment.

Modelling grate combustion of biomass and low rank fuels with CFD application

A reactor cascade model is used for the numerical simulation of the fixed bed combustion of biomass, municipal solid waste and other low rank fuels. Non-spherical particle geometries are accounted for via their plain specific surface. The model is able to reproduce key quantities like ignition delay time, ignition rate, reaction front velocity and mass conversion rate in close agreement with experimental data. This provides a basis to transfer the fixed bed results to the situation of continuous combustion on forward acting grates. A simplified numerical procedure is presented for this purpose. It allows to estimate the structure of a fuel bed moving on the grate as well as the overbed gas temperature and composition. These data serve as input for separate CFD applications which simulate the gas flow in small scale and in industrial scale power plants together with the associated heat transfer processes. Validation of the modelling is presented for lab scale and bench scale experiments as well as for an industrial municipal solid waste incinerator.

Screw pyrolysis technology for sewage sludge treatment

Sewage sludge quantities have grown continuously since the introduction of the European Directive (UWWTD 91/271/EEC) relating to the treatment of urban wastewater. In the present, most of the sewage sludge is combusted in single fuels incineration plants or is co-fired in waste incineration or coal power plants. The combustion of sewage sludge is a proven technology. Other treatments, such as fluidized bed gasification, were successfully adopted to produce suitable syngas for power production. Besides, the number of large wastewater treatment plants is relatively small compared to the local rural ones. Moreover, alternative technologies are arising with the main target of nutrients recovery, with a special focus on phosphorus. The aforementioned issues, i.e. the small scale (below 1MW) and the nutrients recovery, suggest that pyrolysis in screw reactors may become an attractive alternative technology for sewage sludge conversion, recovery and recycling. In this work, about 100kg of dried sewage sludge from a plant in Germany were processed at the newly developed STYX Reactor, at KIT. The reactor combines the advantages of screw reactors with the high temperature filtration, in order to produce particle and ash free vapors and condensates, respectively. Experiments were carried out at temperatures between 350°C and 500°C. The yield of the char decreased from 66.7wt.% to 53.0wt.%. The same trend was obtained for the energy yield, while the maximum pyrolysis oil yield of 13.4wt.% was obtained at 500°C. Besides mercury, the metals and the other minerals were completely retained in the char. Nitrogen and sulfur migrated from the solid to the condensate and to the gas, respectively. Based on the energy balance, a new concept for the decentral production of char as well as heat and power in an externally fired micro gas turbine showed a cogeneration efficiency up to about 40%.

Analysis of right and left ventricular deformation in former world class swimmers: evaluation using speckle tracking

AIM

There is a longstanding debate over the long-term effect of intensive endurance training on cardiac function. Usually, echocardiography has been used as a global evaluation of left ventricular (LV) or right ventricular (RV) function and dimensions. Recently, speckle tracking strain (ST) has provided an analysis of regional RV and LV function. Thus, the intention of the study was to carefully evaluate cardiac function in a group of former world class swimmers applying longitudinal strain (LS) and circumferential strain (CS) analysis.

METHODS

Twelve athletes (45±1.5 years) of a former training group involved in high intensity endurance training were examined 24.9±4.3 years after the end of their active swimming career. An echocardiography was performed and LV function was analyzed based on CS and LS. Also, LS was evaluated for the RV. All measurements were performed for epicardium and endocardium independently.

RESULTS

Mean LV endocardial LS was -20.0±6.3 and epicardial LS -20.2±6.2. LV endocardial CS was -21.3±8.0 and epicardial CS -11.9±4.2. RV endocardial LS had a mean value of -26.4±6.1 and epicardial LS of -28.2±5.6.

CONCLUSION

Twenty-five years after the cessation of endurance training, there was no evidence of a deterioration of RV or LV function as values for RV and LV strain measurements were within normal ranges.

Psychotropic drug prescription patterns among patients with bipolar I disorder

INTRODUCTION

Combination treatment, rather than monotherapy, is prevalent in the treatment of subjects with bipolar disorder, probably due to the complex and phasic nature of the illness. In general, prescription patterns may be influenced by the demographic characteristics of patients as well. We evaluated prescription patterns and the influence of demographic variables on these patterns in a voluntary registry of subjects with bipolar disorder.

METHODS

A subset of data from a larger voluntary registry was extracted for demographic variables and psychotropic medication use that had been reported in the month prior to registration by ambulatory, non-hospitalized subjects with bipolar I disorder in 1995/96 (n = 457).

RESULTS

Among the thymoleptic agents, lithium was prescribed in over 50% of subjects, valproate in approximately 40%, and carbamazepine in 11% of subjects. Eighteen percent of subjects had no prescription for thymoleptic agents. Nearly one-third of all subjects were receiving antipsychotic agents, of whom two-thirds were receiving the traditional neuroleptic agents. More than half of all subjects were receiving concomitant antidepressants, of whom nearly 50% received the SSRI antidepressants and nearly 25% received buproprion. Approximately 40% of subjects received benzodiazepines. Only 18% of subjects received monotherapy, and nearly 50% received three or more psychotropic agents. In general, no associations were noted between demographic parameters including age, gender, marital or educational status, and psychotropic prescriptions.

CONCLUSION

Consistent with the anecdotal reports, these data confirm that combination treatment is far more common than monotherapy. Demography appears to have a minimal impact on cross-sectional prescription patterns in subjects with bipolar disorder. Given that combination treatments are the rule rather than the exception, we should strive to achieve rational, yet pragmatic, treatment guidelines and algorithms to minimize the risks while maximizing the benefits of these combination treatments for patients with bipolar disorder.

Effects of prior fluoxetine treatment on EEG sleep in women with recurrent depression

We examined whether fluoxetine treatment has persistent effects on electroencephalographic sleep after drug discontinuation in patients with recurrent major depression. Age-matched groups of 23 women were treated with interpersonal psychotherapy alone (IPT) or fluoxetine plus interpersonal psychotherapy (IPT + FLU). Sleep studies were conducted when patients were depressed, and again at remission, at least four weeks after fluoxetine discontinuation. The groups did not differ in depression ratings pre- to post-treatment. Significant group*time interaction effects were noted for REM sleep (p = .04) and slow wave sleep (p = .02). REM percentage and phasic REM activity increased in the IPT + FLU group but decreased in the IPT group. The effects of fluoxetine treatment on electroencephalographic sleep can be observed for at least four weeks after drug discontinuation and appear to represent both drug discontinuation and neuroadaptation effects.

Effects of diagnosis on treatment recommendations in chronic insomnia--a report from the APA/NIMH DSM-IV field trial

The objective of this study was to determine whether sleep specialists and nonspecialists recommend different treatments for different insomnia diagnoses according to two different diagnostic classifications. Two hundred sixteen patients with chronic insomnia at five sites were each interviewed by two clinicians: one sleep specialist and one nonsleep specialist. All interviewers indicated diagnoses using the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV); sleep specialists also indicated diagnoses according to the International Classification for Sleep Disorders (ICSD). Interviewers then indicated how strongly they would recommend each item in a standard list of treatment and diagnostic interventions for each patient. We examined differences in treatment recommendations among the six most common DSM-IV diagnoses assigned by sleep specialists at different sites (n = 192), among the six most common ICSD diagnoses assigned by sleep specialists at different sites (n = 153), and among the six most common DSM-IV diagnoses assigned by nonspecialists at different sites (n = 186). In each analysis, specific treatment and polysomnography recommendations differed significantly for different diagnoses, using either DSM-IV or ICSD criteria. Conversely, different diagnoses were associated with different rank orderings of specific treatment and diagnostic recommendations. Sleep specialist and nonspecialist interviewers each distinguished treatment recommendations among different diagnoses, but in general, nonspecialists more strongly recommended medications and relaxation treatments. Significant site-related differences in treatment recommendations also emerged. Differences in treatment recommendations support the distinction between different DSM-IV and ICSD diagnoses, although they do not provide formal validation. Site-related differences suggest a lack of consensus in how these disorders are conceptualized and treated.

Circadian patterns of unintended sleep episodes during a constant routine in remitted depressed patients

Theoretical models of depression have hypothesized phase or amplitude alterations in circadian measures including the sleep-wake rhythm. Whether such abnormalities occur only during the depressed state, or whether they persist into recovery, is less clear. We investigated the circadian pattern of unintended sleep episodes during 36 h of constant wakeful bedrest in two groups: 26 drug-free patients whose depression remitted following psychotherapy treatment, and a contrast group of 17 healthy young adults. The contrast group was not matched for age or gender. Both remitted depressed and contrast groups showed statistically significant linear and quadratic trends in the number of unintended sleep episodes, indicating monotonic and circadian influences across the study interval. We found no significant group differences in the pattern of sleep episodes. The number and timing of sleep episodes did not correlate significantly with core body temperature amplitude or timing or with baseline sleep duration or efficiency. The results do not support the hypothesis of a phase or amplitude change in sleep propensity as a trait abnormality in depression. However, the inclusion of a moderately depressed out-patient cohort, which showed only minor sleep changes and normal temperature profiles even while depressed, may have biased against finding significant differences.