Rhabdoid tumors in patients conceived following ART: is there an association?

STUDY QUESTION: In children affected by rhabdoid tumors (RT), are there clinical, therapeutic, and/or (epi-)genetic differences between those conceived following ART compared to those conceived without ART? SUMMARY ANSWER: We detected a significantly elevated female predominance, and a lower median age at diagnosis, of children with RT conceived following ART (RT_ART) as compared to other children with RT. WHAT IS KNOWN ALREADY: Anecdotal evidence suggests an association of ART with RT. STUDY DESIGN, SIZE, DURATION: This was a multi-institutional retrospective survey. Children with RT conceived by ART were identified in our EU-RHAB database (n = 11/311 children diagnosed between January 2010 and January 2018) and outside the EU-RHAB database (n = 3) from nine different countries. A population-representative German EU-RHAB control cohort of children with RTs conceived without ART (n = 211) (EU-RHAB control cohort) during the same time period was used as a control cohort for clinical, therapeutic, and survival analyses. The median follow-up time was 11.5 months (range 0-120 months) for children with RT_ART and 18.5 months (range 0-153 months) for the EU-RHAB control cohort. PARTICIPANTS/MATERIALS, SETTING, METHODS: We analyzed 14 children with RT_ART diagnosed from January 2010 to January 2018. We examined tumors and matching blood samples for SMARCB1 mutations and copy number alterations using FISH, multiplex ligation-dependent probe amplification, and DNA sequencing. DNA methylation profiling of tumor and/or blood samples was performed using DNA methylation arrays and compared to respective control cohorts of similar age (n = 53 tumors of children with RT conceived without ART, and n = 38 blood samples of children with no tumor born small for gestational age). MAIN RESULTS AND THE ROLE OF CHANCE: The median age at diagnosis of 14 individuals with RT_ART was 9 months (range 0-66 months), significantly lower than the median age of patients with RT (n = 211) in the EU-RHAB control cohort (16 months (range 0-253), P = 0.03). A significant female predominance was observed in the RT_ART cohort (M:F ratio: 2:12 versus 116:95 in EU-RHAB control cohort, P = 0.004). Eight of 14 RT_ART patients were diagnosed with atypical teratoid rhabdoid tumor, three with extracranial, extrarenal malignant rhabdoid tumor, one with rhabdoid tumor of the kidney and two with synchronous tumors. The location of primary tumors did not differ significantly in the EU-RHAB control cohort (P = 0.27). Six of 14 RT_ART patients presented with metastases at diagnosis. Metastatic stage was not significantly different from that within the EU-RHAB control cohort (6/14 vs 88/211, P = 1). The incidence of pathogenic germline variants was five of the 12 tested RT_ART patients and, thus, not significantly different from the EU-RHAB control cohort (5/12 versus 36/183 tested, P = 0.35). The 5-year overall survival (OS) and event free survival (EFS) rates of RT_ART patients were 42.9 ± 13.2% and 21.4 ± 11%, respectively, and thus comparable to the EU-RHAB control cohort (OS 41.1 ± 3.5% and EFS 32.1 ± 3.3). We did not find other clinical, therapeutic, outcome factors distinguishing patients with RT_ART from children with RTs conceived without ART (EU-RHAB control cohort). DNA methylation analyses of 10 tumors (atypical teratoid RT = 6, extracranial, extrarenal malignant RT = 4) and six blood samples from RT_ART patients showed neither evidence of a general DNA methylation difference nor underlying imprinting defects, respectively, when compared to a control group (n = 53 RT samples of patients without ART, P = 0.51, n = 38 blood samples of patients born small for gestational age, P = 0.1205). LIMITATIONS, REASONS FOR CAUTION: RTs are very rare malignancies and our results are based on a small number of children with RT_ART. WIDER IMPLICATIONS OF THE FINDINGS: This cohort of patients with RT_ART demonstrated a marked female predominance, and a rather low median age at diagnosis even for RTs. Other clinical, treatment, outcome, and molecular factors did not differ from those conceived without ART (EU-RHAB control cohort) or reported in other series, and there was no evidence for imprinting defects. Long-term survival is achievable even in cases with pathogenic germline variants, metastatic disease at diagnosis, or relapse. The female preponderance among RT_ART patients is not yet understood and needs to be evaluated, ideally in larger international series. STUDY FUNDING/COMPETING INTEREST(S): M.C.F. is supported by the 'Deutsche Kinderkrebsstiftung' DKS 2020.10, by the 'Deutsche Forschungsgemeinschaft' DFG FR 1516/4-1 and by the Deutsche Krebshilfe 70113981. R.S. received grant support by Deutsche Krebshilfe 70114040 and for infrastructure by the KinderKrebsInitiative Buchholz/Holm-Seppensen. P.D.J. is supported by the Else-Kroener-Fresenius Stiftung and receives a Max-Eder scholarship from the Deutsche Krebshilfe. M.H. is supported by DFG (HA 3060/8-1) and IZKF Münster (Ha3/017/20). BB is supported by the 'Deutsche Kinderkrebsstiftung' DKS 2020.05. We declare no competing interests. TRIAL REGISTRATION NUMBER: N/A.

Nutrient Recovery from Digestate of Agricultural Biogas Plants: A Comparative Study of Innovative Biocoal-Based Additives in Laboratory and Full-Scale Experiments.

Nutrients can be recovered from the digestate of an agricultural biogas plant in the form of solid fraction and serve as crop fertilizers. Removal of suspended solids with screw press separators is the most commonly used technique for treating digestate from biogas plants. To increase separation efficiency and nutrient transfer to the solid phase during separation, eight biocoal-based additives were investigated, which were based on beech wood and produced by pyrolysis at temperatures of 350 °C and 600 °C. Four of the biocoals were impregnated with CaCl2 or MgCl2 before pyrolysis. The reaction time between the additives and the digestate varied from 5 min to 2 weeks. The application of MgCl2-impregnated biocoal synthesized at 600 °C for 20 h increased the nutrient removal efficiency by 76.33% for ammonium and 47.15% for phosphorus, compared to the control (the untreated digestate).

Newly Diagnosed Metastatic Intracranial Ependymoma in Children: Frequency, Molecular Characteristics, Treatment, and Outcome in the Prospective HIT Series.

BACKGROUND: Data on frequency, clinical presentation, and outcome of primary metastatic intracranial ependymoma in children are scarce. PATIENTS AND METHODS: Prospective data on patients younger than 21 years with metastatic intracranial ependymoma at first diagnosis, registered from 2001 to 2014 in the HIT-2000 trial and the HIT-2000 Interim Registry, were analyzed. RESULTS: Of 453 registered patients with intracranial ependymoma and central neuropathology review, initial staging included spinal magnetic resonance imaging in all patients and lumbar cerebrospinal fluid (CSF) analysis in 402 patients. Ten patients (2.2%) had metastatic disease, including three with microscopic CSF positivity only (M1 metastasis stage, 0.7% of patients with CSF staging). Location of the primary tumor was supratentorial in four patients (all supratentorial RELA-fused ependymoma [ST-EPN-RELA]) and within the posterior fossa in five patients (posterior fossa ependymoma type A [PF-EPN-A], n = 4; posterior fossa ependymoma not further classifiable, n = 1), and multifocal in one patient.All four patients with ST-EPN-RELA were alive in first or second complete remission (CR) 7.5-12.3 years after diagnosis. All four patients with macroscopic metastases of posterior fossa or multifocal ependymoma died. Three patients with initial M1 stage (ST-EPN-RELA, n = 1; PF-EPN-A, n = 2) received chemotherapy and local irradiation and were alive in second or third CR 3.0-9.7 years after diagnosis. Progression-free and overall survival of the entire cohort at 5 years was 13% (±6%), and 58% (±16%), respectively. CONCLUSION: Primary metastatic disease is rare in children with intracranial ependymoma. Prognosis may depend on molecular subgroup and extent of dissemination, and relevance of CSF analysis for initial staging remains to be clarified. IMPLICATIONS FOR PRACTICE: Childhood ependymoma presenting with metastasis at first diagnosis is very rare with a frequency of 2.4% in this population-based, well-characterized cohort. Detection of microscopic metastases in the cerebrospinal fluid was extremely rare, and impact on prognosis and respective treatment decision on irradiation field remains unclear. Initial metastatic presentation occurs in both supratentorial RELA-fused ependymoma and posterior fossa ependymoma. Prognosis may differ according to extent of metastasis and biological subgroup, with poor prognosis in diffusely spread metastatic posterior fossa ependymoma even after combination therapy with both intensive chemotherapy and craniospinal irradiation, which may help to guide individual therapeutic decisions for future patients.

Trajectories of Body Mass Index from Childhood to Young Adulthood among Patients with Type 1 Diabetes-A Longitudinal Group-Based Modeling Approach Based on the DPV Registry.

OBJECTIVE: To identify distinct longitudinal patterns of body mass index (BMI) z score in type 1 diabetes from childhood to young adulthood and secondly to determine sex differences as well as associated clinical covariates. STUDY DESIGN: A total of 5665 patients with type 1 diabetes (51% male) with follow-up from 8 to 20 years of age from the multicenter diabetes prospective registry DPV were studied (baseline diabetes duration ≥1 years, BMI z score aggregated per year of life). Latent class growth modeling (SAS: PROC TRAJ) was applied to analyze BMI z score over time. RESULTS: Six distinct BMI z score trajectories were identified (group 1: 7% of patients, group 2: 22%, group 3: 20%, group 4: 16%, group 5: 25%, and group 6: 10%). Group 1, 2, 5, and 6 had an almost stable BMI z score, either in the low, near-normal, high stable, or chronic overweight range. Group 3 (60% girls) increased their BMI during puberty, whereas group 4 (65% boys) had a BMI decrease. Similar patterns were observed for girls only, whereas boys followed nearly stable trajectories without fluctuation over time. Between the near-normal and the other groups, significant differences (P < .05) in sex ratio, migration background, mental health, height z score, glycated hemoglobin A1c, diabetes treatment, dyslipidemia, hypertension, and smoking were observed. CONCLUSIONS: In youth with type 1 diabetes, a great heterogeneity of BMI z score trajectories exists that highlight the importance of personalized sex-specific intervention programs for subjects at risk for unfavorable BMI development.

Development of a production chain from vegetable biowaste to platform chemicals.

BACKGROUND: A future bioeconomy relies on the development of technologies to convert waste into valuable compounds. We present here an attempt to design a biotechnological cascade for the conversion of vegetable waste into acetoin and electrical energy. RESULTS: A vegetable waste dark fermentation effluent containing mainly acetate, butyrate and propionate was oxidized in a bioelectrochemical system. The achieved average current at a constant anode potential of 0 mV against standard hydrogen electrode was 177.5 ± 52.5 µA/cm2. During this step, acetate and butyrate were removed from the effluent while propionate was the major remaining component of the total organic carbon content comprising on average 75.6%. The key players with regard to carbon oxidation and electrode reduction were revealed using amplicon sequencing and metatranscriptomic analysis. Using nanofiltration, it was possible to concentrate the propionate in the effluent. The effluent was revealed to be a suitable medium for biotechnological production strains. As a proof of principle, the propionate in the effluent of the bioelectrochemical system was converted into the platform chemical acetoin with a carbon recovery of 86%. CONCLUSIONS: To the best of our knowledge this is the first report on a full biotechnological production chain leading from vegetable waste to the production of a single valuable platform chemical that integrates carbon elimination steps leading to the production of the valuable side product electrical energy.

Laparoscopic treatment of celiac artery compression syndrome in children and adolescents.

BACKGROUND: The celiac artery compression syndrome (CACS) is a rarely diagnosed disorder, which is characterized by chronic abdominal pain and vegetative symptoms. The role of surgical treatment in celiac artery decompression has been discussed controversially by numerous authors. After first casuistic descriptions of a laparoscopic treatment in adults we established this novel minimally invasive procedure for treatment in children and adolescents. PATIENTS AND METHODS: Between 2005 and 2014 we operated 58 patients (47 female, 11 male) from 7 to 25 years who had been diagnosed with celiac artery compression. The patients presented with severe chronic abdominal pain, vegetative symptoms and a reduced quality of life. Doppler sonography showed an increased blood flow velocity of the celiac artery with maximum of 190 - 450 cm/s (mean 259 cm/s).MR angiography demonstrated a characteristic hook-shaped appearance of the celiac artery with severe localized compression. RESULTS: All patients underwent laparoscopic decompression of the celiac artery. We observed complications in 3 patients (5,2 %). Postoperatively all patients (100 %) were immediately free of abdominal pain. Doppler sonography showed a marked reduction in celiac blood flow velocity to 70 - 190 cm/s postoperatively (mean 178 cm/s). A return of vessel diameters to normal dimensions was documented by postoperative MR angiography. During a median follow up of 62 months we observed a recurrence of the celiac artery compression in 4 patients (6,9 %). CONCLUSIONS: Laparoscopic treatment of celiac artery compression syndrome offers a novel, safe, reliable and, compared to open surgery, less invasive approach. The surgical treatment is indicated in patients with characteristic symptoms and typical findings at Doppler sonography and MRA after exclusion of other abdominal pathologies. The work-up of chronic abdominal pain in children and adolescents should include a color Doppler sonography to look for celiac artery compression.

Effect of different pH-values on process parameters in two-phase anaerobic digestion of high-solid substrates.

In many publications, primary fermentation is described as a limiting step in the anaerobic digestion of fibre-rich biomass [Eastman JA, Ferguson JF. Solubilization of particulacte carbon during the anaerobic digeston. J WPCF. 1981;53:352-366; Noike T, Endo G, Chang J, Yaguchi J, Matsumoto J. Characteristics of carbohydrate degradation and the rate-limiting step in anaerobic digestion. Biotechnol Bioeng. 1985;27:1482-1489; Arntz HJ, Stoppok E, Buchholz K. Anaerobic hydroysis of beet pulp-discontiniuous experiments. Biotechnol Lett. 1985;7:113-118]. The microorganisms of the primary fermentation process differ widely from the methanogenic microorganisms [Pohland FG, Ghosh S. Developments in anaerobic stabilization of organic wastes-the two-phase concept. Environ Lett. 1971;1:255-266]. To optimize the biogas process, a separation in two phases is suggested by many authors [Fox P, Pohland GK. Anaerobic treatment applications and fundamentals: substrate specificity during phase separation. Water Environ Res. 1994;66:716-724; Cohen A, Zoetemeyer RJ, van Deursen A, van Andel JG. Anaerobic digestion of glucose with separated acid production and methane formation. Water Res. 1979;13:571-580]. To carry out the examination, a two-phase laboratory-scale biogas plant was established, with a physical phase separation. In previous studies, the regulation of the pH-value during the acid formation was usually carried out by the addition of sodium hydroxide [Cohen A, Zoetemeyer RJ, van Deursen A, van Andel JG. Anaerobic digestion of glucose with separated acid production and methane formation. Water Res. 1979;13:571-580; Ueno Y, Tatara M, Fukui H, Makiuchi T, Goto M, Sode K. Production of hydrogen and methane from organic solid wastes by phase separation of anaerobic process. Bioresour Technol. 2007;98:1861-1865; Zoetemeyer RJ, van den Heuvel JC, Cohen A. pH influence on acidogenic dissimilation of glucose in an anaerobic digestor. Water Res. 1982;16:303-311]. A new technology without the use of additives was developed in which the pH-regulation is executed by the pH-dependent recycling of effluent from the anaerobic filter into the acidification reactor. During this investigation, the influence of the different target pH-values (5.5, 6.0, 7.0 and 7.5) on the degradation rate, the gas composition and the methane yield of the substrate maize silage was determined. With an increase in the target pH-value from 5.5 to 7.5, the acetic acid equivalent decreased by 88.1% and the chemical oxygen demand-concentration by 18.3% in the hydrolysate. In response, there was a 58% increase in the specific methane yield of the overall system. Contrary to earlier studies, a marked increase in biogas production and in substrate degradation was determined with increasing pH-values. However, these led to a successive approximation of a single-phase process. Based on these results, pH-values above 7.0 seem to be favourable for the digestion of fibre-rich substrates.

Effects of Environmental and Nutritional Conditions on Mycelium Growth of Three Basidiomycota.

In recent decades, an enormous potential of fungal-based products with characteristics equal to, or even outperforming, classic petroleum-derived products has been acknowledged. The production of these new materials uses mycelium, a root-like structure of fungi consisting of a mass of branching, thread-like hyphae. Optimizing the production of mycelium-based materials and fungal growth under technical conditions needs to be further investigated. The main objective of this study was to select fast-growing fungi and identify optimized incubation conditions to obtain a dense mycelium mat in a short time. Further, the influence of the initial substrate characteristics on hyphae expansion was determined. Fungal isolates of Ganoderma lucidum, Pleurotus ostreatus, and Trametes versicolor were cultivated for seven days on substrate mixtures consisting of various proportions of pine bark and cotton fibers. Furthermore, the substrates were mixed with 0, 2, and 5 wt.% calcium carbonate (CaCO3), and the incubator was flushed with 0, 5, and 10 vol.% carbon dioxide (CO2). All samples grew in the dark at 26 °C and a relative humidity of 80%. Evaluation of growth rate shows that cotton fiber-rich substrates performed best for all investigated fungi. Although Pleurotus ostreatus and Trametes versicolor showed comparatively high growth rates of up to 5.4 and 5.3 mm d-1, respectively, mycelium density was thin and transparent. Ganoderma lucidum showed a significantly denser mycelium at a maximum growth rate of 3.3 mm d-1 on a cotton fiber-rich substrate (75 wt.%) without CaCO3 but flushed with 5 vol.% CO2 during incubation.

Model Predictive Control: Demand-Orientated, Load-Flexible, Full-Scale Biogas Production.

Biogas plants have the great advantage that they produce electricity according to demand and can thus compensate for fluctuating production from weather-dependent sources such as wind power and photovoltaics. A prerequisite for flexible biogas plant operation is a suitable feeding strategy for an adjusted conversion of biomass into biogas. This research work is the first to demonstrate a practical, integrated model predictive control (MPC) for load-flexible, demand-orientated biogas production and the results show promising options for practical application on almost all full-scale biogas plants with no or only minor adjustments to the standardly existing measurement technology. Over an experimental period of 36 days, the biogas production of a full-scale plant was adjusted to the predicted electricity demand of a "real-world laboratory". Results with a mean absolute percentage error (MAPE) of less than 20% when comparing biogas demand and production were consistently obtained.

Environmental assessment of a two-stage high pressure anaerobic digestion process and biological upgrading as alternative processes for biomethane production.

Biomethane plays a key role in achieving decarbonization and sustainable development goals. According to the objectives that arise, choosing the most suitable production system allows optimization of production, thereby reducing CO2 emissions. In this study, three biomethane production scenario life cycle assessments were compared to determine which would maintain the lowest CO2 emissions. Conventional anaerobic digestion and an innovative process called two-stage high pressure anaerobic digestion were considered. These methods were combined with two upgrading processes: water scrubbing and biological upgrading. Cattle manure and sugar beets were used as substrates for the process. Emissions were 805.6 gCO2eq/m3CH4 for the traditional biogas production process combined with water scrubbing and 450.3 gCO2eq/m3CH4 for the two-stage anaerobic digestion process combined with biological upgrading. Furthermore, the analysis demonstrated that these values would be reduced by 29.5 % and 48.0 % if electrical energy were produced using only renewable energy sources.

Two-stage anaerobic digestion: State of technology and perspective roles in future energy systems.

Two-stage anaerobic digestion (TSAD) systems have been studied on a laboratory scale for about 50 years. However, they have not yet reached industrial scale despite their potential for future energy systems. This review provides an analysis of the TSAD technology, including the influence of process parameters on biomass conversion rates. The most common substrate (35.2% of the 38 selected studies) used in the analysed data was in the category of rapidly hydrolysable industrial waste with an average dry matter content of 7.24%. The highest methane content of 85% was reached when digesting food waste in a combination of two mesophilic continuously stirred tank reactors with an acidic (pH 5.5) first stage and alkaline (pH 7) second stage. Therefore, the review shows the limitations of the TSAD technology, future research directions, and the effect of integration of TSAD systems into the current strategy to reduce greenhouse gas emissions.

Infants and Newborns with Atypical Teratoid Rhabdoid Tumors (ATRT) and Extracranial Malignant Rhabdoid Tumors (eMRT) in the EU-RHAB Registry: A Unique and Challenging Population.

Introduction: Malignant rhabdoid tumors (MRT) predominantly affect infants and young children. Patients below six months of age represent a particularly therapeutically challenging group. Toxicity to developing organ sites limits intensity of treatment. Information on prognostic factors, genetics, toxicity of treatment and long-term outcomes is sparse. Methods: Clinical, genetic, and treatment data of 100 patients (aged below 6 months at diagnosis) from 13 European countries were analyzed (2005-2020). Tumors and matching blood samples were examined for SMARCB1 mutations using FISH, MLPA and Sanger sequencing. DNA methylation subgroups (ATRT-TYR, ATRT-SHH, and ATRT-MYC) were determined using 450 k / 850 k-profiling. Results: A total of 45 patients presented with ATRT, 29 with extracranial, extrarenal (eMRT) and 9 with renal rhabdoid tumors (RTK). Seventeen patients demonstrated synchronous tumors (SYN). Metastases (M+) were present in 27% (26/97) at diagnosis. A germline mutation (GLM) was detected in 55% (47/86). DNA methylation subgrouping was available in 50% (31 / 62) with ATRT or SYN; for eMRT, methylation-based subgrouping was not performed. The 5-year overall (OS) and event free survival (EFS) rates were 23.5 ± 4.6% and 19 ± 4.1%, respectively. Male sex (11 ± 5% vs. 35.8 ± 7.4%), M+ stage (6.1 ± 5.4% vs. 36.2 ± 7.4%), presence of SYN (7.1 ± 6.9% vs. 26.6 ± 5.3%) and GLM (7.7 ± 4.2% vs. 45.7 ± 8.6%) were significant prognostic factors for 5-year OS. Molecular subgrouping and survival analyses confirm a previously described survival advantage for ATRT-TYR. In an adjusted multivariate model, clinical factors that favorably influence the prognosis were female sex, localized stage, absence of a GLM and maintenance therapy. Conclusions: In this cohort of homogenously treated infants with MRT, significant predictors of outcome were sex, M-stage, GLM and maintenance therapy. We confirm the need to stratify which patient groups benefit from multimodal treatment, and which need novel therapeutic strategies. Biomarker-driven tailored trials may be a key option.

Demand-oriented biogas production and biogas storage in digestate by flexibly feeding a full-scale biogas plant.

This work studied the demand-oriented biogas production and the biogas storage in digestate by flexibly feeding a full-scale research biogas plant. The investigated continuous stirred tank reactor (CSTR) was equipped with a fast-moving submersible motor mixer and a slow-moving inclined shaft agitator. A model for the biogas storage in digestate was introduced and tested in full scale using temporally highly resolved volume flow measurements. An increase in mixing time led to a faster biogas production: A two to five hours reduction of the time to reach the maximum biogas production after feeding occurred in our experiments. However, no influence of the rheology and of the mixing regime on the methane yield could be derived from the measurements. Further, a 30% reduction of the stored biogas in the digestate occurred when the viscosity was lowered by 66%. This knowledge can be used to enhance the existing biogas formation models.

Modeling and Simulation of Biogas Production in Full Scale with Time Series Analysis.

Future biogas plants must be able to produce biogas according to demand, which requires proactive feeding management. Therefore, the simulation of biogas production depending on the substrate supply is assumed. Most simulation models are based on the complex Anaerobic Digestion Model No. 1 (ADM1). The ADM1 includes a large number of parameters for all biochemical and physicochemical process steps, which have to be carefully adjusted to represent the conditions of a respective full-scale biogas plant. Due to a deficiency of reliable measurement technology and process monitoring, nearly none of these parameters are available for full-scale plants. The present research investigation shows a simulation model, which is based on the principle of time series analysis and uses only historical data of biogas formation and solid substrate supply, without differentiation of individual substrates. The results of an extensive evaluation of the model over 366 simulations with 48-h horizon show a mean absolute percentage error (MAPE) of 14-18%. The evaluation is based on two different digesters and demonstrated that the model is self-learning and automatically adaptable to the respective application, independent of the substrate's composition.

Optimal conditions for high solid co-digestion of organic fraction of municipal solid wastes in a leach-bed reactor.

Anaerobic co-digestion of organic fraction of municipal solid waste with solid content greater than 20% and chicken manure was investigated using leach-bed reactors in the framework of Middle East and North African countries. The objectives of the experiments were to determine the optimal ratio of organic fraction, chicken manure and solid inoculum, to compare temperature conditions and usage of liquid inoculum or water in percolation process. The highest specific methane yield (SMY) (236 LN ∙ kg-1 VS) was received in the reactors with 20/80 organic fraction/solid inoculum ratio under thermophilic conditions with liquid inoculum percolation. Under the same conditions but mesophilic temperature, SMY dropped by 12%. Replacing liquid inoculum by water led to 172 LN ∙ kg-1 VS. Addition of chicken manure to the substrate mixture positively influences a start-up phase and keeps pH in optimal range 6.5-8, despite the high ammonia concentration.

Biological methanation of injected hydrogen in a two-stage anaerobic digestion process.

In the field of biological hydrogen methanation, ideal process parameters are underexplored for continuous two-stage systems with anaerobic filters. The present study aims at filling this gap for continuous in-situ reactors while applying different hydrogen injection rates. The results of the study demonstrate an almost complete acid degradation on the output side of the anaerobic filter fed by hydrolysate from maize silage and silage effluent. Most of the oxidizable substances were transferred to methane, but hydrogen could not be completely converted. With fully stoichiometric hydrogen addition, a methane production rate of 0.88 ± 0.06 m3d-1 per m3 reactor volume was reached. With half stoichiometric hydrogen addition, a hydrogen conversion rate of 75.53 ± 3.77% was obtained. The present approach proved to be a promising contribution to power-to-gas technology, as a considerable amount of hydrogen had to be converted into methane while carbon dioxide was fixed.

Investigating flexible feeding effects on the biogas quality in full-scale anaerobic digestion by high resolution, photoacoustic-based NDIR sensing.

In future energy systems based on renewable energies, biogas plants can make a significant contribution to stabilizing the electricity grids. However, this requires load-flexible and demand-oriented electricity production by means of flexible feed management. However, these flexible feeding strategies using greatly oscillating, temporally varying high mass loads may lead to critical process failures of the anaerobic digestion process. Currently there is no online, high resolution gas quality measurement technique to detect and prevent biological process failures available. In this contribution, we present a miniaturized, low-cost biogas quality measurement system providing data with high precision and high temporal resolution to overcome this technology gap. To highlight the capabilities of the system we have installed it using a bypass to the main biogas duct after hydrogen sulfide removal at a full-scale research biogas plant. During a three-month field trial, the effect of flexible feeding on the biogas quality has been monitored. The results demonstrate long-term stability of the sensor solution and reveal the effects of changing feeding frequency and composition on gas quantity and quality, which cannot be detected with commercially available state-of-the-art sensing systems.

Integration of membrane filtration in two-stage anaerobic digestion system: Specific methane yield potentials of hydrolysate and permeate.

Two-stage biogas systems consisting of a CSTR-acidification reactor (AR) and an anaerobic filter (AF) were frequently described for microbial conversion of food and agricultural wastes to biogas. The aim of this study is to investigate the integration of a membrane filtration step in two-stage systems to remove inert particles from hydrolysate produced in AR in order to increase the efficiency of the subsequent AF. Hydrolysates from vegetable waste (VW) and grass/maize silage (G/M) were treated in cross-flow ceramic membrane filtration system (pore size 0.2 µm). Organic acids were extracted efficiently through filtration of hydrolysate. For both the substrates, membrane permeability was stable and high (46.6-49.3 L m-2 h-1 bar-1). Filtration process effectively improved the specific methane yield of permeate by 40% (VW) and 24.5% (G/M) compared to hydrolysate. It could be shown that, the filtration-step increased hydrolysate's degradability, which lead to higher conversion efficiency in the following AF.

Intrinsic gas production kinetics of selected intermediates in anaerobic filters for demand-orientated energy supply.

As a consequence of a growing share of solar and wind power, recent research on biogas production highlighted a need for demand-orientated, flexible gas production to provide grid services and enable a decentralized stabilization of the electricity infrastructure. Two-staged anaerobic digestion is particularly suitable for shifting the methane production into times of higher demand due to the spatio-temporal separation of hydrolysis and methanogenesis. To provide a basis for predicting gas production in an anaerobic filter, kinetic parameters of gas production have been determined experimentally in this study. A new methodology is used, enabling their determination during continuous operation. An order in methane production rate could be established by comparing the half lives of methane production. The order was beginning with the fastest: acetic acid>ethanol>butyric acid>iso-butyric acid>valeric acid>propionic acid>1,2propanediol>lactic acid. However, the mixture of a natural hydrolysate from the acidification tank appeared to produce methane faster than all single components tested.

Effects of target pH-value on organic acids and methane production in two-stage anaerobic digestion of vegetable waste.

Vegetable waste is one of the major organic residues available for sustainable bioenergy production. The aim of this work is to study the influence of pH-value on process stability, hydrolysis, degradation degree and methane production in two-stage anaerobic system. A mixture of vegetable wastes with carrot mousse, carrots, celery, cabbage and potatoes was treated in two-stage system at target pH-values 5.5 and 6 in acidification reactor (AR). At pH 6, high concentrations of organic acids were recorded whereas high amount of hydrolysate was produced at pH 5.5. The chemical oxygen demand (COD) concentration in the hydrolysate produced in AR was 21.85% higher at pH 6 compared to pH 5.5, whereas the overall specific methane yield was slightly higher at pH 5.5 (354.35±31.95 and 326.79±41.42Lkg-1 oDMadded, respectively). It could be shown, that the described two-stage system is well suited for manure-free digestion of vegetable waste.