SEARCH · Search NASA
Results for “DIGESTION”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Anaerobic digestion of solid agroindustrial waste in semi-continuous mode: Evaluation of mono-digestion and co-digestion systems
Highlights: • Agroindustrial waste were co-digested with an artificial organic fraction. • Variations in organic loading rate and hydraulic retention time were studied. • Sequential feeding of the substrates based on their seasonality was investigated. • Co-digestion resulted in higher methane yields compared with mono-digestion. • Applying sequential feeding led to a more equilibrated system operation. - Abstract: The present study aimed at investigating the anaerobic digestion of four agroindustrial waste, namely cotton gin waste, winery waste, olive pomace and juice industry waste, in semi-continuous mode, conducting mono-digestion and co-digestion assays, using an artificial organic fraction sample as co-substrate. These assays were divided into two groups, in which different conditions were applied. Group I investigated the variation in two operational parameters, i.e. the organic loading rate (OLR) and the hydraulic retention time (HRT), while in Group II, the assays were fed with different substrates in a sequential order. Results showed more elevated specific methane yields for co-digestion assays compared with mono-digestion assays. Maximum yields were achieved at an OLR of 1.0 gVS/(L·d) and a HRT reduced to half of the initial. Further reduction of the HRT coupled to an increase of the OLR generally caused a significant decrease of specific methane yields, as well as one case of severe overloading, i.e. the mono-digestion of juice industry waste, which resulted in instability and ultimately system failure. Sequential feeding with different substrates led to a more equilibrated operation, especially for co-digestion systems, with higher specific methane yields being observed during the phases corresponding to winery waste and juice industry waste substrates. Overall more positive results were obtained in the cases in which the latter substrates were fed to the reactors at process startup.
Genetic determinants for enzymatic digestion of lignocellulosic biomass are independent of those for lignin abundance in a maize recombinant inbred population
Explore the source record for details and available documents.
Effect of digestate and digestate supplemented with biochar on switchgrass growth and chemical composition
Digestate, a by-product of anaerobic digestion, can be an excellent source of nutrients for bioenergy crop production, while biochar, resulting from pyrolyzing biomass, can valorize the nutrients of digestate. The objective of this study was to evaluate the nutritional value of digestate and digestate + biochar for switchgrass production. The greenhouse experiment was conducted to determine the effects of a nitrogen (N) source including 0 N (control), urea (nutrient control), sewage sludge digestate, and sewage sludge digestate + corn stover biochar on switchgrass growth and feedstock composition. Nitrogen sources were observed to significantly increase plant weight at the 32-week harvest, with weight ranging from 94.2 to 125.2 g plant -1 , depending on the N source, compared to 70.7 g plant -1 from the negative control. Moreover, switchgrass treated with digestate + biochar showed higher plant weight than samples treated only with digestate. Nitrogen application of urea, digestate, and digestate + biochar had positive effects on plant height and total leaf area in the 32-week harvests and chlorophyll content in the 8-week harvests. Feedstock quality traits including hemicellulose, cellulose, and lignin content were not affected by N sources in either the 8 or 32-week harvests with the exception of ash concentration in the 32-week harvests. Our results indicate that digestate and digestate + biochar can be a potential substitute for chemical fertilizer, resulting in increased biomass yield.
Analysis on carbon dioxide emission reduction during the anaerobic synergetic digestion technology of sludge and kitchen waste: Taking kitchen waste synergetic digestion project in Zhenjiang as an example
Highlights: • Reduce CO{sub 2} emission is a referential index for future sludge disposal. • Synergetic digestion technology of kitchen waste and sludge contributes to the CO{sub 2} reduction. • Synergetic digestion technology reduced more CO{sub 2} emission than sludge landfill. • Synergetic digestion technology should be effectively promoted and applied. - Abstract: With the popularization of municipal sewage treatment facilities, the improvement of sewage treatment efficiency and the deepening degree of sewage treatment, the sludge production of sewage plant has been sharply increased. Carbon emission during the process of municipal sewage treatment and disposal has become one of the important sources of greenhouse gases that cause greenhouse effect. How to reduce carbon dioxide emissions during sewage treatment and disposal process is of great significance for reducing air pollution. Kitchen waste and excess sludge, as two important organic wastes, once uses anaerobic synergetic digestion technology in the treatment process can on the one hand, avoid instability of sludge individual anaerobic digestion, improve sludge degradation rate and marsh gas production rate, and on the other hand, help increase the reduction of carbon dioxide emissions to a great extent. The paper uses material balance method, analyzes and calculates the carbon dioxide emissions from kitchen waste and sludge disposed by the anaerobic synergetic digestion technology, compares the anaerobic synergetic digestion technology with traditional sludge sanitary landfill technology and works out the carbon dioxide emission reductions after synergetic digestion. It takes the kitchen waste and sludge synergetic digestion engineering project of Zhenjiang city in Jiangsu province as an example, makes material balance analysis using concrete data and works out the carbon dioxide daily emission reductions. The paper analyzes the actual situation of emission reduction by comparing the data, and found that the synergetic digestion of kitchen waste and sludge can effectively reduce the carbon dioxide emission, and the reduction is obvious especially compared with that of sludge sanitary landfill, which has a certain effect on whether to promote the use of the technology.
Optimization of solid state anaerobic digestion of the OFMSW by digestate recirculation: A new approach
Highlights: • Solid State Anaerobic Digestion (SSAD) of OFMSW can be optimized by irrigation with digestate. • Digestate spreading allows keeping optimal process parameters and high hydrolysis rate. • The 18.4% of CH{sub 4} was produced in the reactor, leaving the 49.7% in the percolate. • Successive CSTR feed with percolate shows a biogas enriched in methane (more than 80%). • The proposed process allow producing the 68% of OFMSW potential CH{sub 4}, getting high quality organic amendment. - Abstract: Dry anaerobic digestion (AD) of OFMSW was optimized in order to produce biogas avoiding the use of solid inoculum. Doing so the dry AD was performed irrigating the solid waste with liquid digestate (flow rate of 1:1.18–1:0.9 w/w waste/digestate; 21 d of hydraulic retention time – HRT) in order to remove fermentation products inhibiting AD process. Results indicated that a high hydrolysis rate of organic matter (OM) and partial biogas production were obtained directly during the dry AD. Hydrolysate OM was removed from digester by the percolate flow and it was subsequently used to feed a liquid anaerobic digester. During dry AD a total loss of 36.9% of total solids was recorded. Methane balance indicated that 18.4% of potential methane can be produced during dry AD and 49.7% by the percolate. Nevertheless results obtained for liquid AD digestion indicated that only 20.4% and 25.7% of potential producible methane was generated by adopting 15 and 20 days of HRT, probably due to the AD inhibition due to high presence of toxic ammonia forms in the liquid medium.
Evaluation of Nanaerobic Digestion as a Mechanism to Explain Surplus Methane Production in Animal Rumina and Engineered Digesters
Nanaerobes are a newly described class of microorganisms that use a unique cytochrome bd oxidase to achieve nanaerobic respiration at <2 μM dissolved oxygen (~1% of atmospheric oxygen) but are not viable above this value due to the lack of other terminal oxidases. Although sharing an overlapping ecological niche with methanogenic archaea, the role of nanaerobes in methanogenic systems has not been studied so far. To explore their occurrence and significance, we re-analyzed published meta-omic datasets from animal rumina and waste-to-energy digesters, including conventional anaerobic digesters and anaerobic digesters with ultra-low oxygenation. Results show that animal rumina share broad similarities in the microbial community and system performance with oxygenated digesters, rather than with conventional anaerobic digesters, implying that trace levels of oxygen drive the efficient digestion in ruminants. The rumen system serves as an ideal model for the newly named nanaerobic digestion, as it relies on the synergistic co-occurrence of nanaerobes and methanogens for methane yield enhancement. The most abundant ruminal bacterial family Prevotellaceae contains many nanaerobes, which perform not only anaerobic fermentation but also nanaerobic respiration using cytochrome bd oxidase. These nanaerobes generally accompany hydrogenotrophic methanogens to constitute a thermodynamically and physiologically consistent framework for efficient methane generation. Our findings provide new insights into ruminal methane emissions and strategies to enhance methane generation from biomass.
Open‐Source Anaerobic Digestion Modeling Platform, Anaerobic Digestion Model No. 1 Fast (ADM1F)
An open‐source modeling platform, called Anaerobic Digestion Model No. 1 Fast (ADM1F), is introduced to achieve fast and numerically stable simulations of anaerobic digestion processes. ADM1F is compatible with an iPython interface to facilitate model configuration, simulation, data analysis, and visualization. Faster simulations and more stable results are accomplished by implementing an advanced open‐source library of numerical methods called Portable Extensive Toolkit for Scientific Computation (PETSc) to solve the ADM1 system of equations. Leveraging PETSc, ADM1F can consistently complete a steady‐state simulation under 0.2 s, over 99% faster than a benchmark ADM1 model implemented with MATLAB while achieving agreement of model outputs within 1% of those obtained with the benchmark model. For dynamic simulations, however, ADM1F has a computational speed advantage only when the influent characteristics update more frequently than every 4 h. The ability of ADM1F to be useful as a tool to study anaerobic digestion systems is demonstrated through two example implementations of ADM1F: (1) a two‐phase co‐digestion scenario evaluating the impact of the organic loading rate and the substrate composition on reactor performance and stability, and (2) a conventional digester scenario assessing the effectiveness of recovery strategies after disruptions that led to instability. These examples demonstrate how the high simulation speed and the convenience of the iPython interface allow ADM1F to complete complex analyses within minutes, much faster than computational strategies currently reported in the literature.
Recycled wastewater from anaerobic digestion of lipid extracted algae as a source of nutrients
Not provided.
Comparison of different liquid anaerobic digestion effluents as inocula and nitrogen sources for solid-state batch anaerobic digestion of corn stover
Highlights: Black-Right-Pointing-Pointer Compared methane production of solid AD inoculated with different effluents. Black-Right-Pointing-Pointer Food waste effluent (FWE) had the largest population of acetoclastic methanogens. Black-Right-Pointing-Pointer Solid AD inoculated with FWE produced the highest methane yield at F/E ratio of 4. Black-Right-Pointing-Pointer Dairy waste effluent (DWE) was rich of cellulolytic and xylanolytic bacteria. Black-Right-Pointing-Pointer Solid AD inoculated with DWE produced the highest methane yield at F/E ratio of 2. - Abstract: Effluents from three liquid anaerobic digesters, fed with municipal sewage sludge, food waste, or dairy waste, were evaluated as inocula and nitrogen sources for solid-state batch anaerobic digestion of corn stover in mesophilic reactors. Three feedstock-to-effluent (F/E) ratios (i.e., 2, 4, and 6) were tested for each effluent. At an F/E ratio of 2, the reactor inoculated by dairy waste effluent achieved the highest methane yield of 238.5 L/kgVS{sub feed}, while at an F/E ratio of 4, the reactor inoculated by food waste effluent achieved the highest methane yield of 199.6 L/kgVS{sub feed}. The microbial population and chemical composition of the three effluents were substantially different. Food waste effluent had the largest population of acetoclastic methanogens, while dairy waste effluent had the largest populations of cellulolytic and xylanolytic bacteria. Dairy waste also had the highest C/N ratio of 8.5 and the highest alkalinity of 19.3 g CaCO{sub 3}/kg. The performance of solid-state batch anaerobic digestion reactors was closely related to the microbial status in the liquid anaerobic digestion effluents.
Influence on anaerobic digestion by intermediate thermal hydrolysis of waste activated sludge and co-digested wheat straw
Highlights: • Intermediate thermal hydrolysis mediates further energy recovery. • Straw for co-digestion boosts methane production. • Thermal hydrolysis increases VFA concentration but lowers pH. • Thermal hydrolysis without flash has optimum at 170 °C and 30 min. - Abstract: This paper analyses time (30 and 60 min) and temperature (120–190 °C) effects of intermediate thermal hydrolysis (ITHP) in a two-step anaerobic digestion of waste activated sludge (WAS) with and without wheat straw as a co-substrate. Effects were analyzed by measuring biochemical methane potential for 60 days and assessing associated kinetic and chemical data. Compared to non-treatment, ITHP increased the secondary step methane yield from 52 to 222 L CH{sub 4} kg VS{sup −1} and from 147 to 224 L CH{sub 4} kg VS{sup −1} for pre-digested WAS and pre-co-digested WAS respectively at an optimum of 170 °C and 30 min. The hydrolysis coefficients (k{sub hyd}) increased by up to 127% following treatment. Increasing ITHP time from 30 to 60 min showed ambiguous results regarding methane yields, whilst temperature had a clear and proportional effect on the concentrations of acetic acid. The energy balances were found to be poor and dewatering to increase total solids above the values tested here is necessary for this process to be energetically feasible.
Mercury adsorption kinetics on sulfurized biochar and solid-phase digestion using aqua regia: A sync
Explore the source record for details and available documents.
Application of Anaerobic Digestion Model No. 1 for simulating anaerobic mesophilic sludge digestion
Highlights: • The behavior of a anaerobic reactor was evaluated through modeling. • Parametric sensitivity analysis was used to select most sensitive of the ADM1. • The results indicate that the ADM1 was able to predict the experimental results. • Organic load rate above of 35 kg/m{sup 3} day affects the performance of the process. - Abstract: Improving anaerobic digestion of sewage sludge by monitoring common indicators such as volatile fatty acids (VFAs), gas composition and pH is a suitable solution for better sludge management. Modeling is an important tool to assess and to predict process performance. The present study focuses on the application of the Anaerobic Digestion Model No. 1 (ADM1) to simulate the dynamic behavior of a reactor fed with sewage sludge under mesophilic conditions. Parametric sensitivity analysis is used to select the most sensitive ADM1 parameters for estimation using a numerical procedure while other parameters are applied without any modification to the original values presented in the ADM1 report. The results indicate that the ADM1 model after parameter estimation was able to predict the experimental results of effluent acetate, propionate, composites and biogas flows and pH with reasonable accuracy. The simulation of the effect of organic shock loading clearly showed that an organic shock loading rate above of 35 kg/m{sup 3} day affects the performance of the reactor. The results demonstrate that simulations can be helpful to support decisions on predicting the anaerobic digestion process of sewage sludge.
Optimisation of sewage sludge anaerobic digestion through co-digestion with OFMSW: Effect of collection system and particle size
Highlights: • Methane production rate increased between 56% and 208% during OFMSW–SS codigestion. • The OFMSW particle size reduction from 20 to 8 mm did not affect the methane yield. • OFMSW–SS codigestion promoted β-oxidation and acetoclastic methanogenic activity. • The evolution of specific activity was a feasible tool to control the process. - Abstract: The effect of organic fraction of municipal solid waste (OFMSW) loading rate and particulate size on the sewage sludge (SS) mesophilic anaerobic co-digestion was assessed in continuous stirred tank reactor at hydraulic retention time of 20 days. The SS–OFMSW mixture composed by 54% of the volatile solids fed (inlet-VS), at OLR of 3.1 kg{sub COD} m{sup −3} d{sup −1} (1.9 kg{sub VS} m{sup −3} d{sup −1}), showed the highest increment on the volumetric methane production and yield of +200% and +59% respectively, under stable conditions. The effect of particulate size was assessed with the same mixture and same operational conditions but reducing the OFMSW particulate size from 20 mm to 8 mm with the aim to improve the hydrolysis step, but the results showed any influence in the OFMSW particulate size range analysed. In addition, specific biomass activity was assessed at the end of each co-digestion period. Results showed that OFMSW promoted β-oxidation syntrophic acetogens and the acetoclastic methanogens activity; although the last increase of the OFMSW percentage (from 47% to 54% inlet-VS) affected negatively the specific substrate activity, but not inhibitory effect was observed. Therefore, the results obtained in the continuous experiment could be related with some inhibitory or toxic effect and not due to hydrolysis limitation. The specific biomass activity test was demonstrated to be an interesting tool to evaluate and control the co-digestion process, especially when conventional parameters did not explain the behaviour of the biological system.
Hydrogen and methane production in a two-stage anaerobic digestion system by co-digestion of food waste, sewage sludge and glycerol
Highlights: • H{sub 2} and CH{sub 4} production was assessed in a two-stage acidogenesis-methanogenesis system. • Addition of glycerol to food waste and sewage sludge increased H{sub 2} and CH{sub 4} yields. • Stable H{sub 2} and CH{sub 4} production and higher energy yield were obtained at 1% glycerol. • The use of 3% glycerol led to process instabilities in the methanogenic phase. • Co-digestion of food waste, sewage sludge and glycerol maximizes energy production. - Abstract: In this study, hydrogen and methane production from co-digestion of food waste (FW), sewage sludge (SS) and raw glycerol (GL) was evaluated in a two-stage acidogenesis-methanogenesis anaerobic system under mesophilic conditions (35 °C). The effect of glycerol addition (1 and 3% v/v) as co-substrate was assessed in ternary mixtures (FW + SS + GL), with the concentration of all substrates kept at 10 g VS/L. Besides contributing to reduce the lag phase of the acidogenic bacterial culture, the presence of GL increased the hydrogen production in all tested conditions and the maximum hydrogen yield was obtained for the FW + SS + 3%GL mixture (179.3 mL H{sub 2}/g VS). On the other hand, the highest methane production (342 mL CH{sub 4}/g VS) was achieved in the test supplemented with 1% GL. At 3% GL, abrupt reductions in the biogas CH{sub 4} content and pH values resulting from instability in methanogenesis process were noticed over the experiment. By taking into account the hydrogen and methane production stages, the highest energy yield (i.e., 15.5 kJ/g VS) was obtained with the ternary mixture containing 1% GL. Overall, the results of this study demonstrate the feasibility of using glycerol as co-substrate to increase the H{sub 2} and CH{sub 4} production efficiency in a two-stage anaerobic co-digestion process, allowing simultaneous treatment of three residues (FW, SS and GL) and energy production.
Digestibility of the defatted microalgae Nannochloropsis sp. and Desmodesmus sp. when fed to Atlantic salmon, Salmo salar
The aim of the study was to investigate the apparent digestibility coefficient (ADC) of defatted biomass derived from microalgae Nannochloropsis sp. and Desmodesmus sp. when fed to Atlantic salmon postsmolts in seawater. Two experiments, one employing cold-pelleted and the other employing extruded pellets, were carried out to determine the ADC of dry matter (DM), protein, ash and energy. The test feeds consisted of a fishmeal-based reference feed and the algal biomass, at a ratio of 70:30, and yttrium oxide as the inert marker. The ADC of DM and protein in fish fed microalgae-incorporated cold-pelleted feeds were significantly higher for Nannochloropsis sp. compared with Desmodesmus sp. Here, the Nannochloropsis sp. inclusion in extruded feeds also led to higher ADCs of DM and energy compared with Desmodesmus sp. The extrusion processing significantly increased the ADC of ash in both defatted microalgae biomass, as well as ADCs of DM in Nannochloropsis and protein in Desmodesmus sp. In conclusion, the microalga Nannochloropsis sp. was more digestible than Desmodesmus sp., and extrusion processing can be used as a means to improve digestibility of certain nutrients.