Startup process, safety and risk assessment of biomass gasification for off-grid rural electrification.

Biomass gasification has significantly advanced in terms of performance and is increasingly used in rural off-grid electricity applications. The downdraft gasifier is primarily used in biomass gasification applications, in which it functions as a reactor into which biomass and gasifying air are introduced to generate producer gas that is then used in an engine generator to produce electricity. However, the safety and stability of biomass gasification remain challenging and depend on several factors, such as the startup heating process, which can affect risks of fire, explosion, and toxic gas emissions. As the biomass gasification is associated with high temperatures and demands safety measures, its startup process should follow a rigorous procedure that ensures reliable operation and minimizes the risk of hazard issues. This study presents a gasifier startup heating process based on a proposed safety protocols hazard analysis. The study indicates that the heating temperature in startup processes has been identified as a critical factor due to its role in impacting safety. The findings indicate that the biomass gasification process has significant risks, including the potential for fire, explosion, and release of environmental emissions via multiple pathways. The methods proposed here could lead to reduced risk from the abovementioned issues.

Recycled PMMA prepared directly from crude MMA obtained from thermal depolymerization of mixed PMMA waste.

Recycled PMMA was prepared by directly polymerizing crude pyrolysis oils from lab-scale pyrolysis of collected industrial waste PMMA. The pyrolysis oils consisted mainly of methyl methacrylate (MMA, >85%), while the type and number of by-products from the thermal process were assigned through GC-MS analysis showing a clear correlation to the pyrolysis temperature. By-products can be removed by distillation; however, directly employing the crude oils to prepare PMMA through solution, suspension, emulsion, or casting polymerization was investigated to assess the potential for omitting this costly step. It was found that the crude pyrolysis oils could be polymerized efficiently via solution, emulsion, and casting polymerization to produce a polymer similar to the PMMA prepared from a pristine monomer. The impurities in the PMMAs prepared from the crude mixtures were investigated by extraction analyses followed by screening by GC-MS. In the case of casting polymerization, the GC-MS analysis, as expected, revealed various residual by-products, while solution and emulsion polymerization showed only very few impurities, mainly originating from the polymerization and not the feed material. Additional purification of the crude pyrolysis oils would be required for applications in casting polymerization. In contrast, direct polymerization by emulsion or solution polymerization is considered applicable for producing pristine PMMA from crude waste PMMA pyrolysis oil.

Effects of different treatments of manure on mitigating methane emissions during storage and preserving the methane potential for anaerobic digestion.

Current agricultural practices in regards to storage of manure come with a significant GHG contribution, due, to a big extent, to CH4 emissions. For example, in Denmark, the agricultural sector is responsible for about 11.1 metric tons of CO2 equivalents; only about 0.2 metric tons come directly from CO2, while 6.0 tons come from CH4. The present study aims at evaluating and comparing two methods based on their effect on suppressing CH4 emissions during storage as well as on preserving and enhancing CH4 yield in a subsequent anaerobic digestion step: the commonly applied acidification with H2SO4 as acidifying agent and thermal treatment at the mild temperatures of 70 and 90 °C (pasteurization). Although both treatments effectively suppressed CH4 emissions during storage, they exhibited a significant difference in preserving and/or enhancing the CH4 potential of manure. Specifically, thermal treatment resulted in 16-35% enhancement of CH4 potential, while acidification resulted in decreasing the CH4 yield by 6-23% compared to non-treated manure. Further investigation showed that storage itself positively affected the CH4 potential of treated manure in a subsequent anaerobic digestion step; this was attributed to microbial activity other than biomethanation during storage. In overall and based on the results obtained regarding suppression of CH4 emissions during storage as well as CH4 potential enhancement, pasteurization at the temperatures tested is a promising alternative to the broadly applied acidification of manure.

Regulation of integrin α6A by lactogenic hormones in rat pancreatic ß-cells: Implications for the physiological adaptation to pregnancy.

AIM: During pregnancy, the maternal ß-cell mass is increased in order to adapt to the physiological changes in insulin demand. Lactogenic hormones stimulate rodent ß-cell attachment and proliferation in vitro. The aim of this study was to identify adhesion molecules involved in expansion of the ß-cell mass during pregnancy in the rat. METHODS: Quantitative RT-PCR was used to evaluate the expression of several integrins and laminins in isolated neonatal rat islets in response to growth hormone (GH) and prolactin (PRL) treatment. Double-immunofluorescence staining of rat pancreas was used to localize the expression of integrin α6ß1. ß-cell proliferation was evaluated by incorporation of bromodeoxyuridine (BrdU). The role of STAT5 phosphorylation was tested by addition of STAT5 mutants. RESULTS: We found that the mRNA level of integrin-α6A, was upregulated 2.5-fold by PRL or GH. During pregnancy, a biphasic 3.4-4.5-fold increase of integrin-α6A and B mRNA levels was detected. A disintegrin peptide (DP) reduced the hormone-stimulated mitotic activity in neonatal rat ß-cells from 2.9 ± 0.4-fold to 1.3 ± 0.3-fold. The hormone-induced expression of α6ß1 integrin was shown to be mediated via STAT5 as a dominant negative (DN) mutant prevented and a constitutive active (CA) mutant augmented the hGH-stimulated expression. The DP was found to inhibit hGH-induced transactivation of the PRL receptor promoter 1A and reduce the hGH-induced phosphorylation of STAT5. CONCLUSION: These results show that integrin-α6 in ß-cells is upregulated by lactogenic hormones and is required but not sufficient for the expansion of the ß-cell mass in pregnancy in the rat, which may have implications for the understanding and treatment of gestational diabetes mellitus.

Changes imposed by pyrolysis, thermal gasification and incineration on composition and phosphorus fertilizer quality of municipal sewage sludge.

Fertilizer quality of ash and char from incineration, gasification and pyrolysis of a single municipal sewage sludge sample were investigated by comparing composition and phosphorus (P) plant availability. A process for post oxidation of gasification ash and pyrolysis char was developed and the oxidized materials were investigated as well. Sequential extraction with full elemental balances of the extracted pools as well as scanning electron microscopy with energy dispersive X-ray spectroscopy were used to investigate the mechanisms driving the observed differences in composition and P plant availability in a short-term soil incubation study. The compositional changes related mainly to differences in the proximate composition as well as to the release of especially nitrogen, sulfur, cadmium and to some extent, phosphorus (P). The cadmium load per unit of P was reduced with 75-85% in gasification processes and 10-15% in pyrolysis whereas no reduction was observed in incineration processes. The influence on other heavy metals was less pronounced. The plant availability of P in the substrates varied from almost zero to almost 100% of the plant availability of P in the untreated sludge. Post-oxidized slow pyrolysis char was found to be the substrate with the highest P fertilizer value while ash from commercial fluid bed sludge incineration had the lowest P fertilizer quality. The high P fertilizer value in the best substrate is suggested to be a function of several different mechanisms including structural surface changes and improvements in the association of P to especially magnesium, calcium and aluminum.

Low temperature circulating fluidized bed gasification and co-gasification of municipal sewage sludge. Part 2: Evaluation of ash materials as phosphorus fertilizer.

The study is part 2 of 2 in an investigation of gasification and co-gasification of municipal sewage sludge in low temperature gasifiers. In this work, solid residuals from thermal gasification and co-gasification of municipal sewage sludge were investigated for their potential use as fertilizer. Ashes from five different low temperature circulating fluidized bed (LT-CFB) gasification campaigns including two mono-sludge campaigns, two sludge/straw mixed fuels campaigns and a straw reference campaign were compared. Experiments were conducted on two different LT-CFBs with thermal capacities of 100kW and 6MW, respectively. The assessment included: (i) Elemental composition and recovery of key elements and heavy metals; (ii) content of total carbon (C) and total nitrogen (N); (iii) pH; (iv) water extractability of phosphorus after incubation in soil; and (v) plant phosphorus response measured in a pot experiment with the most promising ash material. Co-gasification of straw and sludge in LT-CFB gasifiers produced ashes with a high content of recalcitrant C, phosphorus (P) and potassium (K), a low content of heavy metals (especially cadmium) and an improved plant P availability compared to the mono-sludge ashes, thereby showing the best fertilizer qualities among all assessed materials. It was also found that bottom ashes from the char reactor contained even less heavy metals than cyclone ashes. It is concluded that LT-CFB gasification and co-gasification is a highly effective way to purify and sanitize sewage sludge for subsequent use in agricultural systems.

Low temperature circulating fluidized bed gasification and co-gasification of municipal sewage sludge. Part 1: Process performance and gas product characterization.

Results from five experimental campaigns with Low Temperature Circulating Fluidized Bed (LT-CFB) gasification of straw and/or municipal sewage sludge (MSS) from three different Danish municipal waste water treatment plants in pilot and demonstration scale are analyzed and compared. The gasification process is characterized with respect to process stability, process performance and gas product characteristics. All experimental campaigns were conducted at maximum temperatures below 750°C, with air equivalence ratios around 0.12 and with pure silica sand as start-up bed material. A total of 8600kg of MSS dry matter was gasified during 133h of operation. The average thermal loads during the five experiments were 62-100% of nominal capacity. The short term stability of all campaigns was excellent, but gasification of dry MSS lead to substantial accumulation of coarse and rigid, but un-sintered, ash particles in the system. Co-gasification of MSS with sufficient amounts of cereal straw was found to be an effective way to mitigate these issues as well as eliminate thermal MSS drying requirements. Characterization of gas products and process performance showed that even though gas composition varied substantially, hot gas efficiencies of around 90% could be achieved for all MSS fuel types.

Disturbed mitochondrial function restricts glutamate uptake in the human Müller glia cell line, MIO-M1.

Using the human Müller cell line, MIO-M1, the aim was to study the impact of mitochondrial inhibition in Müller glia through antimycin A treatment. MIO-M1 cell survival, levels of released lactate, mitochondrial function, and glutamate uptake were studied in response to mitochondrial inhibition and glucose restriction. Lactate release decreased in response to glucose restriction. Combined glucose restriction and blocked mitochondrial activity decreased survival and caused collapse of the respiratory chain measured by oxygen consumption rate and extracellular acidification rate. Mitochondrial inhibition caused impaired glutamate uptake and decreased mRNA expression of the glutamate transporter, EAAT1. Over all, we show important roles of mitochondrial activity in MIO-M1 cell function and survival.

Gamma-variate plasma clearance versus urinary plasma clearance of 51 Cr-EDTA in patients with cirrhosis with and without fluid retention.

In patients with fluid retention, the plasma clearance of 51 Cr-EDTA (Clexp obtained by multiexponential fit) may overestimate the glomerular filtration rate (GFR). The present study was undertaken to compare a gamma-variate plasma clearance (Clgv) with the urinary plasma clearance of 51 Cr-EDTA (Clu ) in patients with cirrhosis with and without fluid retention. A total of 81 patients with cirrhosis (22 without fluid retention, 59 with ascites) received a quantitative intravenous injection of 51 Cr-EDTA followed by plasma and quantitative urinary samples for 5 h. Clgv was determined from the injected dose relative to the plasma concentration-time area, obtained by a gamma-variate iterative fit. Clexp and Clu were determined by standard technique. In patients without fluid retention, Clgv , Clexp and Clu were closely similar. The difference between Clgv and Clu (Clgv - Clu  = ΔCl) was mean -0·6 ml min-1  1·73 m-2 . In patients with ascites, ΔCl was significantly higher (11·8 ml min-1  1·73 m-2 , P<0·0001), but this value was lower than Clexp - Clu (17·5 mL min-1  1·73 m-2 , P<0·01). ΔCl increased with lower values of GFR (P<0·001). In conclusion, in patients with fluid retention and ascites Clgv and Clexp overestimates GFR substantially, but the overestimation is smaller with Clgv . Although Clu may underestimate GFR slightly, patients with ascites should collect urine quantitatively to obtain a reliable measurement of GFR.

Lactate Transport and Receptor Actions in Retina: Potential Roles in Retinal Function and Disease.

In retina, like in brain, lactate equilibrates across cell membranes via monocarboxylate transporters and in the extracellular space by diffusion, forming a basis for the action of lactate as a transmitter of metabolic signals. In the present paper, we argue that the lactate receptor GPR81, also known as HCAR1, may contribute importantly to the control of retinal cell functions in health and disease. GPR81, a G-protein coupled receptor, is known to downregulate cAMP both in adipose and nervous tissue. The receptor also acts through other down-stream mechanisms to control functions, such as excitability, metabolism and inflammation. Recent publications predict effects of the lactate receptor on neurodegeneration. Neurodegenerative diseases in retina, where the retinal ganglion cells die, notably glaucoma and diabetic retinopathy, may be linked to disturbed lactate homeostasis. Pilot studies reveal high GPR81 mRNA in retina and indicate GPR81 localization in Müller cells and retinal ganglion cells. Moreover, monocarboxylate transporters are expressed in retinal cells. We envision that lactate receptors and transporters could be useful future targets of novel therapeutic strategies to protect neurons and prevent or counteract glaucoma as well as other retinal diseases.

Red blood cell sodium transport in patients with cirrhosis.

Patients with advanced cirrhosis have abnormal sodium homoeostasis. The study was undertaken to quantify the sodium transport across the plasma membrane of red blood cells (RBC) in patients with cirrhosis. RBC efflux and influx of sodium were studied in vitro with tracer (22) Na(+) according to linear kinetics in 24 patients with cirrhosis and 14 healthy controls. The sodium efflux was modified by ouabain (O), furosemide (F) and a combination of O and F (O + F). RBC sodium was significantly decreased (4·6 versus control 6·3 mmol l(-1) , P<0·001) and directly related to serum sodium (r = 0·57, P<0·05). The RBC fractional sodium efflux was higher in patients with cirrhosis (+46%, P<0·01) compared to controls. Inhibition in both high (145 mmol l(-1) )- and low (120 mmol l(-1) )-sodium buffers showed that the F-insensitive sodium efflux was twice as high in cirrhosis as in controls (P = 0·03-0·007), especially the O-sensitive, F-insensitive efflux was increased (+ 225%, P = 0·01-0·006). Fractional F-sensitive transport was normal in cirrhosis. RBC sodium influx was largely normal in cirrhosis. In conclusion, RBC sodium content is reduced in patients with cirrhosis with a direct relation to serum sodium. Increased RBC sodium efflux is especially related to ouabain-sensitive, furosemide-insensitive transport and thus most likely due to upregulated activity of the sodium-potassium pump. The study gives no evidence to an altered intracellular/extracellular sodium ratio or to a reduced fractional furosemide-sensitive sodium transport in cirrhosis.

Total plasma clearance versus urinary plasma clearance of (51)Cr-EDTA in patients with cirrhosis with and without fluid retention.

BACKGROUND AND AIM: In patients with fluid retention, the total plasma clearance of (51)Cr-EDTA (ClP) may overestimate the glomerular filtration rate (GFR). The present study was therefore undertaken in order to compare ClP with the urinary plasma clearance of (51)Cr-EDTA (ClU) in patients with cirrhosis with and without fluid retention. MATERIAL AND METHODS: A total of 136 patients with cirrhosis (24 without fluid retention, 112 with ascites) received a quantitative intravenous injection of (51)Cr-EDTA followed by plasma and quantitative urinary samples for 5 hours. ClP was determined from the injected dose relative to the plasma concentration-time area, extrapolated to infinity. ClU was determined as urinary excretion relative to the plasma concentration-time area up to voiding. RESULTS: In patients without fluid retention, the difference between ClP and ClU (ClP - ClU = ClΔ) was mean 4.5 mL/min/1.73 m(2). In patients with ascites, ClΔ was significantly higher (17.6 mL/min/1.73 m(2), p < 0.0001). ClΔ increased with lower values of GFR (r = - 0.458, p < 0.001). Repeated measurements of ClU in a subgroup of patients with fluid retention (n = 25) gave almost identical values. Different types of corrections of one-pool clearance were almost identical with ClP, except for higher clearance values, which were somewhat underestimated by the former. CONCLUSION: In patients with fluid retention and ascites ClP and corrected one-pool clearance overestimates GFR substantially. Although ClU may underestimate GFR slightly, patients with ascites should collect urine quantitatively in order to obtain a reliable measurement of GFR.

The clearance concept with special reference to determination of glomerular filtration rate in patients with fluid retention.

In subjects without fluid retention, the total plasma clearance of a renal filtration indicator (inulin, (99m) Tc-DTPA, (51) Cr-EDTA) is close to the urinary plasma clearance. Conversely, in patients with fluid retention (oedema, pleural effusions, ascites), there is a substantial discrepancy between the total plasma clearance and the urinary plasma clearance. This is owing to delayed indicator distribution to smaller or larger parts of the interstitial space, which in patients with ascites may simulate a peritoneal dialysator. In patients with fluid retention, urinary plasma clearance should be assessed to obtain a correct measurement of the glomerular filtration rate (GFR). In theory, total plasma clearance with late samples (24-h, 48-h) may be applied in patients with fluid retention, but validation hereof has not been performed. Until such studies are completed, it is recommended that patients with fluid retention have their GFR measured by a urinary plasma clearance technique with controlled quantitative urinary sampling within a few hours after indicator injection.

One-sample determination of glomerular filtration rate (GFR) in children. An evaluation based on 75 consecutive patients.

BACKGROUND AND AIM: From a clinical point of view determination of glomerular filtration rate (clearance) is important. The aim of the present study was to compare the one-sample clearance to reference multiple-sample (51)Cr-EDTA clearance in consecutively referred children suspected of or with established nephro-urological disorders. MATERIAL AND METHODS: A total of 75 children, age ½-13 years, received a quantitative intravenous injection of (51)Cr-EDTA followed by six plasma samples 10-120 min after injection. The multiple-sample clearance was measured as injected dose relative to the area under the plasma radioactivity curve. The one-sample clearance was determined from a single plasma sample collected at 60, 90 or 120 min after injection according to the one-pool method. RESULTS: The overall accuracy of one-sample clearance was excellent with mean numeric difference to the reference value of 0.7-1.7 mL/min. In 64 children, the one-sample clearance was within ± 4 mL/min of the multiple-sample value. However, in 11 children the numeric difference exceeded 4 mL/min (4.4-19.5). Analysis of age, body size, distribution volume, indicator retention time, clearance level, curve fitting, and sampling time could not explain the observed large difference between one-sample and multiple-sample clearance in these 15% of the children. CONCLUSION: In the majority of children there is an excellent agreement between one-sample clearance and multiple-sample clearance. However, unexpectedly in a small fraction (15%) larger discrepancies are found. If an accurate clearance value is essential a multiple-sample determination should be performed.

(99m) Tc-labelled human serum albumin cannot replace (125) I-labelled human serum albumin to determine plasma volume in patients with liver disease.

BACKGROUND AND AIMS: Determination of plasma volume (PV) is important in several clinical situations. Thus, patients with liver disease often have augmented PV as part of their sodium-water retention. This study was undertaken to compare PV determination by two indicators: technetium-labelled human serum albumin ((99m) Tc-HSA) and iodine-labelled human serum albumin ((125) I-HSA), as the former may have advantages at repeated measurements and the latter is the classical gold standard. STUDY POPULATION AND METHODS: In 88 patients, (64 with liver disease, mainly cirrhosis, and 24 patients without liver disease), simultaneous measurements of PV were taken with (99m) Tc-HSA and (125) I-HSA after 1 h in the supine position. Blood samples were obtained before and 10 min after quantitative injection of the two indicators. In a subset of patients (n = 32), the measurements were repeated within 1 h. RESULTS: In all patients, a close correlation was present between PV determined by the two indicators (r = 0·89, P<0·0001). In all, but twelve patients, a higher PV was obtained with (99m) Tc-HSA compared with (125) I-HSA (P<0·0001). PV determined with (99m) Tc-HSA exceeded PV determined with (125) I-HSA by 367 ml (5·2 ml kg(-1) ) in liver patients as compared to 260 ml (3·5 ml kg(-1) ) in patients without liver disease (P<0·05). The precision of repeated PV determination was 1·75% (coefficient of variation) with (99m) Tc-HSA and 1·71% with (125) I-HSA (ns), and similar values were found in patients with and without liver disease. CONCLUSION: The study demonstrates that (99m) Tc-HSA has the same precision as that of (125) I-HSA. However, especially in patients with liver disease, (99m) Tc-HSA consistently overestimates the PV, most likely owing to indicator heterogeneity with subsequent fast removal from the circulating medium with a higher volume of distribution as the outcome.

The development of a computer model for a fixed bed gasifier and its use for optimization and control.

The development of a mathematical model of a fixed-bed gasifier is described. The model was used for studies of the stationary performance of the gasifier and the results were compared to experimental results. The model was also used in an effort to identify an efficient control strategy for the operation during load changes. The resulting strategy was very simple and has been implemented in an unmanned, automatically controlled, power plant that was operated for over 3000h. The mathematical model was based on conservation of mass and energy in a simple one-dimensional flow, chemical equilibrium in the gas phase, and a Langmuir-Hinshelwood correlation describing the reaction kinetics in the char. The results of the thermo-gravimetric analysis experiments required to determine the reactivity for char of beech as a function of temperature, gas composition and conversion ratio of the char are presented.