Comparison of Operating Methods in Cartridge Anaerobic Digestion of Corn Stover.

Anaerobic digestion of lignocellulosic biomass faces changes such as biomass floating and effluent discharge. To overcome these challenges, a unique removable cartridge anaerobic digester was built and tested using corn stover as the feedstock. Three operating methods differing in the number of cartridges and days of rotation were tested. The first method used three cartridges, with each cartridge being rotated every 7 days. The second and third methods employed four cartridges, with cartridges being rotated every 7 and 9-10 days, respectively. The retention time for methods 1, 2, and 3 was 21, 28, and 38 days, respectively. After observation spanning 1 year, it was found that the cartridge digester was capable of generating a stable amount of biogas for energy without biomass floating or effluent discharging issues. The average daily methane yield from each method was 7.57, 7.11, and 6.82 L/day/kg-VS, and the cumulative methane yield was 158.95, 199.04, and 259.00 L/kg-VS, respectively. Ammonium nitrogen and pH values were in normal ranges throughout the experiment. This study provided new knowledge in operating and optimizing this cartridge digester, which may be broadly used for the anaerobic digestion of lignocellulosic biomass in the near future. Supplementary Information: The online version contains supplementary material available at 10.1007/s12155-021-10252-w.

A narrative review on environmental impacts of cannabis cultivation.

Interest in growing cannabis for medical and recreational purposes is increasing worldwide. This study reviews the environmental impacts of cannabis cultivation. Results show that both indoor and outdoor cannabis growing is water-intensive. The high water demand leads to water pollution and diversion, which could negatively affect the ecosystem. Studies found out that cannabis plants emit a significant amount of biogenic volatile organic compounds, which could cause indoor air quality issues. Indoor cannabis cultivation is energy-consuming, mainly due to heating, ventilation, air conditioning, and lighting. Energy consumption leads to greenhouse gas emissions. Cannabis cultivation could directly contribute to soil erosion. Meanwhile, cannabis plants have the ability to absorb and store heavy metals. It is envisioned that technologies such as precision irrigation could reduce water use, and application of tools such as life cycle analysis would advance understanding of the environmental impacts of cannabis cultivation.

Usos y limitaciones de la lámpara ultravioleta germicida portátil para la desinfección de superficies.

RESUMENLa morbimortalidad causada por infecciones vinculadas a la atención sanatoria ha llevado a cuestionar si los métodos de desinfección convencionales son inadecuados y se requieren métodos complementarios, como la fumigación de la habitación y la irradiación ultravioleta. Ello ha dado lugar a la preocupación por que estos métodos alternativos puedan poner en riesgo al personal sanitario y a los pacientes.Objetivos. (1) Determinar la eficacia de la lámpara ultravioleta C germicida portátil para la desinfección de superficies, (2) evaluar el cambio de la humedad relativa (HR) y las distintas distancias específicas en las tasas de letalidad bacteriana, y (3) evaluar los posibles problemas a que conlleva la exposición.Métodos. En el presente estudio se investiga si una lámpara germicida portátil puede desinfectar de forma eficaz superficies tratadas con esporulación o germinación bacteriana y se evalúa el efecto de condiciones ambientales cambiantes, como la humedad relativa (HR), la posición y las distancias específicas, en las tasas de letalidad germicida.Resultados. Se constató una mejor tasa de letalidad con una HR de 40-65% y en un rango de temperatura de 21-24°C. Tanto la HR alta como la HR baja interfirieron con la capacidad de la radiación UV-C para inactivar la germinación microbiana. En el caso de la esporulación bacteriana, el aumento del secado de la superficie fue el factor de mayor importancia para aumentar la tasa de letalidad.Conclusiones. En esta investigación se demostró la eficacia de la radiación UV-C bajo condiciones óptimas, irradiación directa y una distancia específica corta (12.7 cm). Sin embargo, cuando es utilizada en condiciones que no son óptimas existen limitaciones. El aumento de la distancia y los ángulos de irradiación indirecta resultaron en tasas de letalidad más bajas. Cabe señalar que durante su uso es importante minimizar la exposición innecesaria de pacientes y personal sanitario.

Reactor performance and economic evaluation of singular, binary, and ternary mixing of feedstocks for anaerobic digestion.

This study compared the performance of singular, binary, and ternary mixing of feedstocks for anaerobic digestion. Three wastes, including organic fraction of municipal solid waste (OFMSW), dairy manure, and corn stover, were tested under the mesophilic condition. Results showed that the binary and ternary mixing stabilised digesters while solely processing OFMSW resulted in pH drop and over accumulation of volatile fatty acids. The highest methane yield of 302.3 L/kg-VS was achieved with 50% OFMSW, 33% corn stover, and 17% dairy manure, which was about 5 times of that obtained from digesting OFMSW alone. The binary and ternary mixing led to multiple peaks in daily methane production, which evened out methane production throughout the 50-day digestion process. Economic analysis showed that solid digestate price, direct fixed capital cost, and labour cost significantly affected net present value (NPV). Ternary mixtures had the highest NPV and internal rate of return and were financially attractive under analysis conditions.

Microbial and isotopomer analysis of N2O generation pathways in ammonia removal biofilters.

Ammonia removal biofilters can be a potential source of nitrous oxide (N2O) production as a result of microbial nitrification and denitrification. In this study, these two N2O generation pathways was quantified using isotopic site preference values (SP, 33‰ for nitrification and 0‰ for denitrification) in a 204-d operation. Tests with two moisture conditions (45% and 55%) and three inlet NH3 concentrations (35, 18 and 0 ppmv) were performed. A 55+% NH3 removal efficiency was achieved in biofilters with 35 and 18 ppmv ammonia supply, but no significant difference (p > 0.05) was found between the moisture treatments. Results showed that biofilters were clearly net sources of N2O, and biofilters with higher moisture content generated significantly (p < 0.05) higher N2O concentration. The N2O generation did not stop even after the biofilters were terminated. The percentage of inlet NH3-N converted into N2O-N were 5.2%, 8.5% for biofilters with 45% moisture content, and 14.8%, 10.8% for those with 55% moisture content. Gene abundance of amoA and nosZ in packing materials (taken on days 64, 107, 140, 180 and 204) increased due to NH3 input reaching the highest on day 140 and then decreased in response to reduced NH3 supply on day 180 and 204. The changes of SP values suggested a shift between nitrification and denitrification with regard to N2O generation. Overall, the nitrification was the dominant pathway for N2O generation, but uncertainty exits as well. This study confirmed that NH3-loaded biofilters were net sources of N2O, and use of SP-N2O may be helpful in better understanding the processes responsible for such emissions.

A Case Study on Converting Organic Farm Waste Vegetables to Biogas Using a Cartridge Design Anaerobic Digester.

Anaerobic digestion of multiple waste vegetables collected from an organic farm in Central Illinois was carried out using a new cartridge design anaerobic digestion system. Waste vegetables, including carrot, cucumber, bell pepper, onion, lettuce, and potato, were chopped and then mixed together to be used as the digestion feedstock. Three cartridges in the digestion chamber were rotated every week. Results showed that the system was stable, in terms of biogas and methane yields, ammonium-nitrogen concentration, and pH value, throughout the 90-day operation. On average, the daily and accumulative methane yield were 23.38 L/day/kg-VS and 490.98 L/kg-VS (21-day retention time), respectively. Rotation of cartridge significantly affected methane yield, methane concentration in biogas, and hydrogen sulfide concentration in biogas. Especially, the average hydrogen sulfide concentration decreased from 1145 ppm, to 695 ppm, and then to 539 ppm, in biogas samples taken on 2 days, 4 days, and 7 days after rotation. No liquid waste was generated throughout the test. A rough estimate of the potential biogas yield shows that if all the waste vegetables and crop residues collected from this farm were used in this new anaerobic digestion system, US$4711 in energy can be saved in a year.

Anaerobic digestion of food waste - Challenges and opportunities.

The disposal of large amounts of food waste has caused significant environmental pollution and financial costs globally. Compared with traditional disposal methods (i.e., landfilling, incineration, and composting), anaerobic digestion (AD) is a promising technology for food waste management, but has not yet been fully applied due to a few technical and social challenges. This paper summarizes the quantity, composition, and methane potential of various types of food waste. Recent research on different strategies to enhance AD of food waste, including co-digestion, addition of micronutrients, control of foaming, and process design, is discussed. It is envisaged that AD of food waste could be combined with an existing AD facility or be integrated with the production of value-added products to reduce costs and increase revenue. Further understanding of the fundamental biological and physicochemical processes in AD is required to improve the technology.

The uses and limitations of a hand-held germicidal ultraviolet wand for surface disinfection.

The morbidity and mortality from healthcare associated infections has raised concern that conventional disinfection methods are inadequate and that other adjunct methods such as room fumigation and ultraviolet irradiation may be needed. There is also concern that these alternative methods may pose a risk to workers and patients. OBJECTIVES: (1) Determine the efficacy of a germicidal UV-C wand for surface disinfection, (2) evaluate changing relative humidity (RH) and different target distances on bacteria kill rates, and (3) assess potential exposure concerns. METHODS: This study investigates whether a hand-held germicidal wand can efficaciously disinfect surfaces treated with either a vegetative or spore forming bacterium and to evaluate the effect of changing environmental conditions such as relative humidity (RH), target position, and target distances on microbial kill rates. RESULTS: Kill rate was best at 40-65% RH at a temperature range of 21-24°C. Both high and low RH interfered with the ability of UV-C to kill the vegetative microbe. In the case of the spore forming bacterium, increased surface drying time was the most significant factor increasing kill rate. CONCLUSIONS: This research demonstrates that UV-C was efficacious under optimal conditions, a direct beam exposure, and a short target distance (12.7 cm). However, there are limitations when used in non-optimal conditions. Increased distance and indirect beam angles resulted in lower kill rates. It is also important to minimize unnecessary patient and worker exposure during its use.

Recovery of failed solid-state anaerobic digesters.

This study examined the performance of three methods for recovering failed solid-state anaerobic digesters. The 9-L digesters, which were fed with corn stover, failed at a feedstock/inoculum (F/I) ratio of 10 with negligible methane yields. To recover the systems, inoculum was added to bring the F/I ratio to 4. Inoculum was either added to the top of a failed digester, injected into it, or well-mixed with the existing feedstock. Digesters using top-addition and injection methods quickly resumed and achieved peak yields in 10days, while digesters using well-mixed method recovered slowly but showed 50% higher peak yields. Overall, these methods recovered 30-40% methane from failed digesters. The well-mixed method showed the highest methane yield, followed by the injection and top-addition methods. Recovered digesters outperformed digesters had a constant F/I ratio of 4. Slow mass transfer and slow growth of microbes were believed to be the major limiting factors for recovery.

Beyond land application: Emerging technologies for the treatment and reuse of anaerobically digested agricultural and food waste.

Effective treatment and reuse of the massive quantities of agricultural and food wastes generated daily has the potential to improve the sustainability of food production systems. Anaerobic digestion (AD) is used throughout the world as a waste treatment process to convert organic waste into two main products: biogas and nutrient-rich digestate, called AD effluent. Biogas can be used as a source of renewable energy or transportation fuels, while AD effluent is traditionally applied to land as a soil amendment. However, there are economic and environmental concerns that limit widespread land application, which may lead to underutilization of AD for the treatment of agricultural and food wastes. To combat these constraints, existing and novel methods have emerged to treat or reuse AD effluent. The objective of this review is to analyze several emerging methods used for efficient treatment and reuse of AD effluent. Overall, the application of emerging technologies is limited by AD effluent composition, especially the total solid content. Some technologies, such as composting, use the solid fraction of AD effluent, while most other technologies, such as algae culture and struvite crystallization, use the liquid fraction. Therefore, dewatering of AD effluent, reuse of the liquid and solid fractions, and land application could all be combined to sustainably manage the large quantities of AD effluent produced. Issues such as pathogen regrowth and prevalence of emerging organic micro-pollutants are also discussed.

Concentration, size, and density of total suspended particulates at the air exhaust of concentrated animal feeding operations.

Total suspended particulate (TSP) samples were seasonally collected at the air exhaust of 15 commercial concentrated animal feeding operations (CAFOs; including swine finishing, swine farrowing, swine gestation, laying hen, and tom turkey) in the U.S. Midwest. The measured TSP concentrations ranged from 0.38 ± 0.04 mg m⁻³ (swine gestation in summer) to 10.9 ± 3.9 mg m⁻³ (tom turkey in winter) and were significantly affected by animal species, housing facility type, feeder type (dry or wet), and season. The average particle size of collected TSP samples in terms of mass median equivalent spherical diameter ranged from 14.8 ± 0.5 µm (swine finishing in winter) to 30.5 ± 2.0 µm (tom turkey in summer) and showed a significant seasonal effect. This finding affirmed that particulate matter (PM) released from CAFOs contains a significant portion of large particles. The measured particle size distribution (PSD) and the density of deposited particles (on average 1.65 ± 0.13 g cm⁻³) were used to estimate the mass fractions of PM10 and PM2.5 (PM ≤ 10 and ≤ 2.5 µm, respectively) in the collected TSP. The results showed that the PM10 fractions ranged from 12.7 ± 5.1% (tom turkey) to 21.1 ± 3.2% (swine finishing), whereas the PM2.5 fractions ranged from 3.4 ± 1.9% (tom turkey) to 5.7 ± 3.2% (swine finishing) and were smaller than 9.0% at all visited CAFOs. This study applied a filter-based method for PSD measurement and deposited particles as a surrogate to estimate the TSP's particle density. The limitations, along with the assumptions adopted during the calculation of PM mass fractions, must be recognized when comparing the findings to other studies.

Comparison of premixing methods for solid-state anaerobic digestion of corn stover.

The development of solid-state anaerobic digestion (SS-AD) has prompted studies to resolve practical challenges such as mixing of feedstock and inoculum. This study compared the performance of SS-AD using three premixing methods. Results showed that at feedstock to inoculum (F/I) ratios of 4 and 6, the two-layer partial premixing method obtained the highest methane yield, followed by one-layer partial premixing and complete premixing methods. Partial premixing methods also showed wider daily methane yield peaks than the complete premixing method. The volatile fatty acid (VFA) concentration was affected by the premixing method, and was highly correlated to methane yield; while the concentration of remaining holocellulose was correlated to pH and alkalinity. SS-AD digesters failed at an F/I ratio of 8, regardless of the premixing method. Adding extra inoculum to the top of failed digesters resulted in recovery of methane production.

Qualitative and quantitative analysis on aroma characteristics of ginseng at different ages using E-nose and GC-MS combined with chemometrics.

Aroma profiles of ginseng samples at different ages were investigated using electronic nose (E-nose) and GC-MS techniques combined with chemometrics analysis. The bioactive ginsenoside and volatile oil content increased with age. E-nose performed well in the qualitative analyses. Both Principal Component Analysis (PCA) and Discriminant Functions Analysis (DFA) performed well when used to analyze ginseng samples, with the first two principal components (PCs) explaining 85.51% and the first two factors explaining 95.51% of the variations. Hierarchical Cluster Analysis (HCA) successfully clustered the different types of ginsengs into four groups. A total of 91 volatile constituents were identified. 50 of them were calculated and compared using GC-MS. The main fragrance ingredients were terpenes and alcohols, followed by aromatics and ester. The changes in terpenes, alcohols, aromatics, esters, and acids during the growth year once again confirmed the dominant role of terpenes. The Partial Least Squares (PLS) loading plot of gas sensors and aroma ingredients indicated that particular sensors were closely related to terpenes. The scores plot indicated that terpenes and its corresponding sensors contributed the most in grouping. As regards to quantitative analyze, 7 constituent of terpenes could be accurately explained and predicted by using gas sensors in PLS models. In predicting ginseng age using Back Propagation-Artificial Neural Networks (BP-ANN), E-nose data was found to predict more accurately than GC-MS data. E-nose measurement may be a potential method for determining ginseng age. The combination of GC-MS can help explain the hidden correlation between sensors and fragrance ingredients from two different viewpoints.

Taste characteristics based quantitative and qualitative evaluation of ginseng adulteration.

BACKGROUND: Adulteration of American ginseng with Asian ginseng is common and has caused much damage to customers. Panel evaluation is commonly used to determine their differences, but it is subjective. Chemical instruments are used to identify critical compounds but they are time-consuming and expensive. Therefore, a fast, accurate and convenient method is required. A taste sensing system, combining both advantages of the above two technologies, provides a novel potential technology for determining ginseng adulteration. The aim is to build appropriate models to distinguish and predict ginseng adulteration by using taste characteristics. RESULTS: It was found that ginsenoside contents decreased linearly (R(2) = 0.92) with mixed ratios. A bioplot of principal component analysis showed a good performance in classing samples with the first two principal components reaching 89.7%, and it was noted that it was the bitterness, astringency, aftertaste of bitterness and astringency, and saltiness leading the successful determination. After factor screening, bitterness, astringency, aftertaste of bitterness and saltiness were employed to build latent models. Tastes of bitterness, astringency and aftertaste bitterness were demonstrated to be most effective in predicting adulteration ratio, mean while, bitterness and aftertaste bitterness turned out to be most effective in ginsenoside content prediction. CONCLUSION: Taste characteristics of adulterated ginsengs, considered as taste fingerprint, can provide novel guidance for determining the adulteration of American and Asian ginseng.

Biological conversion of methane to liquid fuels: status and opportunities.

Methane is the main component of natural gas and biogas. As an abundant energy source, methane is crucial not only to meet current energy needs but also to achieve a sustainable energy future. Conversion of methane to liquid fuels provides energy-dense products and therefore reduces costs for storage, transportation, and distribution. Compared to thermochemical processes, biological conversion has advantages such as high conversion efficiency and using environmentally friendly processes. This paper is a comprehensive review of studies on three promising groups of microorganisms (methanotrophs, ammonia-oxidizing bacteria, and acetogens) that hold potential in converting methane to liquid fuels; their habitats, biochemical conversion mechanisms, performance in liquid fuels production, and genetic modification to enhance the conversion are also discussed. To date, methane-to-methanol conversion efficiencies (moles of methanol produced per mole methane consumed) of up to 80% have been reported. A number of issues that impede scale-up of this technology, such as mass transfer limitations of methane, inhibitory effects of H2S in biogas, usage of expensive chemicals as electron donors, and lack of native strains capable of converting methane to liquid fuels other than methanol, are discussed. Future perspectives and strategies in addressing these challenges are also discussed.

Anaerobic digestion of giant reed for methane production.

As a fast growing plant, giant reed has good potential to be used as a feedstock for methane production via anaerobic digestion (AD). The effect of total solids (TS) content, an AD operating parameter, was studied. Results showed that increasing TS from 8% to 38% decreased methane yield, due to the inhibition of volatile fatty acids (VFAs) and total ammonia nitrogen (TAN); while the maximum volumetric methane production was obtained at 20-23% TS. Comparison of solid-state AD (SS-AD) at 20% TS and liquid AD (L-AD) at 8% TS was conducted at feedstock to effluent (F/E) ratios of 2.0, 3.5, and 5.0. The best performance was achieved at an F/E of 2.0, with methane yields of 129.7 and 150.8L-CH4/kg-VS for SS-AD and L-AD, respectively. Overall organic components were degraded by 17.7-28.5% and 24.0-26.6% in SS-AD and L-AD, respectively; among which cellulose showed the highest degradation rate and the highest contribution to methane production.

Comparison of solid-state anaerobic digestion and composting of yard trimmings with effluent from liquid anaerobic digestion.

Solid-state anaerobic digestion (SS-AD) and composting of yard trimmings with effluent from liquid AD were compared under thermophilic condition. Total solids (TS) contents of 22%, 25%, and 30% were studied for SS-AD, and 35%, 45%, and 55% for composting. Feedstock/effluent (F/E) ratios of 2, 3, 4, 5, and 6 were tested. In composting, the greatest carbon loss was obtained at 35% TS, which was 2-3 times of that at 55% TS and was up to 50% higher than that in SS-AD. In SS-AD, over half of the degraded carbon was converted to methane with the greatest methane yield of 121 L/kg VS(feedstock). Methane production from SS-AD was low at F/E ratios of 2 and 3, likely due to the inhibitory effect of high concentrations of ammonia nitrogen (up to 5.6g/kg). The N-P-K values were similar for SS-AD digestate and compost with different dominant nitrogen forms.

Moisture effects on gas-phase biofilter ammonia removal efficiency, nitrous oxide generation, and microbial communities.

We established a four-biofilter setup to examine the effects of moisture content (MC) on biofilter performance, including NH3 removal and N2O generation. We hypothesized that MC increase can improve NH3 removal, stimulate N2O generation and alter the composition and function of microbial communities. We found that NH3 removal efficiency was greatly improved when MC increased from 35 to 55%, but further increasing MC to 63% did not help much; while N2O concentration was low at 35-55% MC, but dramatically increased at 63% MC. Decreasing MC from 63 to 55% restored N2O concentration. Examination of amoA communities using T-RFLP and real-time qPCR showed that the composition and abundance of ammonia oxidizers were not significantly changed in a "moisture disturbance-disturbance relief" process in which MC was increased from 55 to 63% and then reduced to 55%. This observation supported the changes of NH3 removal efficiency. The composition of nosZ community was altered at 63% MC and then was recovered at 55% MC, which indicates resilience to moisture disturbance. The abundance of nosZ community was negatively correlated with moisture content in this process, and the decreased nosZ abundance at 63% MC explained the observation of increased N2O concentration at that condition.

Strong influence of medium pH condition on gas-phase biofilter ammonia removal, nitrous oxide generation and microbial communities.

Effects of pH on gas-phase biofilter performance including NH3 removal efficiency (RE), N2O generation, and microbial communities of ammonia oxidizers and denitrifies, are examined. A two-step experiment was carried out on four biofilters for 130 days. In step 1 with pH 8.0, NH3 REs were 85-95% and N2O concentrations were 0.1-0.4 ppm. In step 2, pH was adjusted to 4.5, 6.0, 8.0, and 9.5 in four biofilters, respectively. The acidified biofilters showed higher NH3 REs than the alkalized biofilters. N2O concentration in biofilters with pH 4.5 and 6.0 was increased to 1.5 and 0.5 ppm, respectively, while no change in the alkalized biofilters. Comparing to communities in step 1, the amoA and nosZ structures were altered when pH was changed to 4.5 and 6.0, but not at 9.5. Abundance of amoA was reduced at pH 4.5, while nosZ abundance was increased with considerably less changes in acidified biofilters compared to alkalized biofilters.

[Effects of extracellular calcium concentration on platelets aggregation, coagulation indices and thromboelastography].

OBJECTIVE: To detect the effect of extracellular Ca2+ concentrations on test results of coagulation-related parameters. METHODS: Blood samples of outpatient medical volunteers were collected and then different doses of calcium chloride added. The rate of platelet aggregation (n = 42), prothrombin time (PT), thrombin time (TT) and activated partial thromboplastin time (APTT) (n = 21) and parameters of thromboelastography (n = 30) were detected according to the standard protocols by plasma turbidimetry, coagulation and recalcification respectively. RESULTS: When the plasma Ca2+ concentration was in the range of 0.1 - 33.7 mmol/L, the rate of platelet aggregation gradually increased with a increasing concentration of Ca2+. And the rates induced by adenosine diphosphate (ADP) and arachidonic acid (AA) were (51.8 +/- 9.6)% - (94.7 +/- 4.8)% and (64.4 +/- 12.2)% - (93.2 +/- 5.5)% respectively. When the Ca2+ concentration was 39.0 mmol/L, the rate decreased markedly [ADP (9.1 +/- 5.3)%, AA (11.1 +/- 4.5)%, both P < 0.01]. When the Ca2+ concentration was in the range of 0.1 - 33.7 mmol/L, the values of PT gradually increased with a increasing concentration of Ca2+. The values of TT changed in "V"-type and became minimum when the calcium concentration was 4.4 mmol/L. The values of APTT decreased with higher calcium concentrations and could not be determined when the concentration increased above 0.5 mmol/L. When the Ca2+ concentration was in the range of 0.4 - 27.3 mmol/L, the values of reaction time and coagulation time of thromboelastography changed in "V"-type and became nearly minimal at the Ca2+ concentration of about 2.1 mmol/L. The values of alpha angle and maximum amplitude changed in "V"-type and became maximal at the Ca2+ concentration of 2.1 mmol/L. CONCLUSIONS: The effect of Ca2+ concentration on the testing results of coagulation-related parameters is significant. A high calcium ( > or = 39 mmol/L) can inhibit the platelet aggregation, coagulation factor activity and blood coagulation. The Ca2+ concentration of 2.1 mmol/L seems to be the optimal concentration for thromboelastography by recalcification method.