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"Singla, Ankit"
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An overview of key pretreatment processes for biological conversion of lignocellulosic biomass to bioethanol
Second-generation bioethanol can be produced from various lignocellulosic biomasses such as wood, agricultural or forest residues. Lignocellulosic biomass is inexpensive, renewable and abundant source for bioethanol production. The conversion of lignocellulosic biomass to bioethanol could be a promising technology though the process has several challenges and limitations such as biomass transport and handling, and efficient pretreatment methods for total delignification of lignocellulosics. Proper pretreatment methods can increase concentrations of fermentable sugars after enzymatic saccharification, thereby improving the efficiency of the whole process. Conversion of glucose as well as xylose to bioethanol needs some new fermentation technologies to make the whole process inexpensive. The main goal of pretreatment is to increase the digestibility of maximum available sugars. Each pretreatment process has a specific effect on the cellulose, hemicellulose and lignin fraction; thus, different pretreatment methods and conditions should be chosen according to the process configuration selected for the subsequent hydrolysis and fermentation steps. The cost of ethanol production from lignocellulosic biomass in current technologies is relatively high. Additionally, low yield still remains as one of the main challenges. This paper reviews the various technologies for maximum conversion of cellulose and hemicelluloses fraction to ethanol, and it point outs several key properties that should be targeted for low cost and maximum yield.
Journal Article
Effect of biogas digested slurry based-biochar and digested liquid on N2O, CO2 flux and crop yield for three continuous cropping cycles of komatsuna (Brassica rapa var. perviridis)
Biogas production generates digested slurry, as a byproduct, which can be used as fertilizer after its conversion into digested liquid and biochar. A microcosm-based study was conducted to evaluate the effects of chemical fertilizer (CF), digested liquid (DL) and varying concentrations of biogas digested slurry based-biochar along with DL on N
2
O flux, CO
2
flux, soil chemical properties and crop yield for three continuous cropping cycles of komatsuna (
Brassica rapa
var. perviridis) from April to July 2013. Analyses revealed that DL-treated soils released almost equal cumulative amounts of N
2
O and CO
2
as soils treated with CF. The soil mineral-N contents were also similar for the DL- and CF-treated soils while DL application increased the soluble organic carbon (SOC) content of the soil compared to CF treatment. The application of slurry-based biochar increased N
2
O and CO
2
flux, which, in turn, appeared to depend upon biochar concentration. The application of biochar probably increased the nitrification rate as biochar-treated soils had higher values of NO
3
−
-N and lower values of NH
4
+
-N compared to soils not treated with biochar at most of the observations. The SOC content was also the highest in biochar-treated soils. The overall crop yield for three cropping cycles was the highest in DL and biochar at low application rate (BL), and it was lower in CF, biochar at medium (BM) and high (BH) application rate. This study indicates that the application of DL could be an effective strategy to minimize the use of CF, without affecting N
2
O flux, CO
2
flux, soil mineral N, and increasing crop productivity. The effects of slurry-based biochar on greenhouse gases flux and crop yield depends on the application rate of biochar.
Journal Article
Effect of slag-type fertilizers on N2O flux from komatsuna vegetated soil and CH4 flux from paddy vegetated soil
Slag-type fertilizer, which is a byproduct of the steel industry, contains high amount of active iron oxide and silica. This byproduct acts as an oxidizing agent in the agricultural soils and may have positive impact on the soil properties and plant growth. It can suppress CH
4
emission, while may also affect N
2
O emission. A pot experiment with komatsuna and a microcosm experiment with rice were conducted to determine the effect of slag-type fertilizers (Agripower and Minekaru) on N
2
O and CH
4
flux, respectively. The application rate of silica was kept similar for both fertilizers which caused four times higher iron application in Minekaru treatment compared to Agripower treatment. The observation results revealed that the Agripower and Minekaru treatment emitted more N
2
O only in the initial stage of the experiment compared to the control soil. The cumulative N
2
O emission over 59 days of the experiment was not significantly different between the various treatments. Minekaru-treated soil significantly decreased seasonal and cumulative CH
4
flux over 112 days of the experiment compared to Agripower and control soil, while Agripower did not affect compared to the control. It was possibly due to higher iron application in Minekaru treatment than Agripower treatment. The application of Agripower and Minekaru increased shoot weight, panicle numbers, and weight of panicles in paddy. This study suggests that the application of slag-type fertilizers neither affect cumulative N
2
O emission nor plant biomass in komatsuna. The application of Minekaru significantly decreased CH
4
evolution; while Agripower and Minekaru increased plant biomass in paddy vegetated soil.
Journal Article
Coupled steel slag and biochar amendment correlated with higher methanotrophic abundance and lower CH4 emission in subtropical paddies
Aerobic methanotrophs in paddies serve as methane (CH4) filters and thereby reduce CH4 emissions. Amending soil with waste products can mitigate CH4 emissions in crops, but little is known about the impacts of amendments with steel slag and biochar on the populations and activities of aerobic methanotrophs in rice cropland. We used real-time quantitative PCR detecting system and high-throughput sequencing to determine the effects of slag and biochar amendments on CH4 emission, abundance, and community structure of methanotrophs, and the relationships between soil properties and the abundance and community composition of methanotrophs during the rice growing season in both early and late paddies. Soil salinity and pH were significantly higher for an amendment with both slag and biochar than the control in both the early and late paddies, and pH was significantly higher for a slag amendment in the late paddy. Cumulative CH4 emission was lower for the slag and slag + biochar amendments than the control in early paddy by—34.1%. Methanotrophic abundance was three- and sixfold higher for the slag + biochar amendment than the control in the early and late paddies (p < 0.05), respectively. The abundance of different groups of methanotrophs varied among the treatments. The relative abundance of Methylosarcina was higher for the slag amendment than the control, and the relative abundance of Methylomonas was lower for biochar, and slag + biochar amendments than the control. The relative abundance of Methylocystis was higher for the slag and slag + biochar amendments than the control in the early paddy, and the relative abundance of Methylocystis was higher for the slag, biochar, and slag + biochar amendments in the late paddy. Univariate and multivariate analyses indicated that the higher abundance of methanotrophic bacteria for the slag and slag + biochar amendments was correlated with soil pH, salinity, soil organic carbon, and C/N ratio, and the relative abundances of Methylocystis, Methylomonas, and Methylosarcina were associated with the effective mitigation of CH4 emission in the paddies. A discriminant general analysis indicated that the total population of methanotrophs was larger for the slag + biochar amendment than the control, and that this effect was only weakly correlated with changes in the soil properties, demonstrating that this effect on the size and species composition of methanotrophic soil populations was mostly associated with a direct effect of the slag + biochar amendment.
Journal Article
Methane production potential and methanogenic archaeal community structure in tropical irrigated Indian paddy soils
Soil characteristics regulate various belowground microbial processes including methanogenesis and, consequently, affect the structure and function of methanogenic archaeal communities due to change in soil type which in turn influences the CH₄ production potential of soils. Thus, five different soil orders (Alfisol, Entisol, Inceptisol, Podzol and Vertisol) were studied to assess their CH₄ production potential and also the methanogenic archaeal community structure in dryland irrigated Indian paddy soils. Soil incubation experiments revealed CH₄ production to range from 178.4 to 431.2 μg CH₄ g⁻¹ dws in all soil orders as: Vertisol
Journal Article
Comparison of effects exerted by bio-fertilizers, NPK fertilizers, and cultivation methods on soil respiration in Chernozem soil
Soil respiration is a significant indicator of soil microbial activity; global soil respiration and decomposition processes release yearly to the atmosphere a total of 220 billion tons of carbon dioxide. Therefore, studies on the whole- or one particular aspect of soil carbon cycle aiming at optimizing agricultural carbon dioxide emissions or improving carbon sequestration contribute to a sustainable agriculture practice. In this paper we present the effects of biofertilizer application (Bacillus megaterium, Bacillus circulans, and Pseudomonas putida) on soil respiration in chernozem soil. Experiments were performed at Látókép Experimental Station, belonging to the University of Debrecen, Hungary. Additionally, we compare our results with findings of prior studies related to commercial NPK fertilizer applications (in four doses: N60P45K45; N120P90K90; N180 P135K135; and N240P180K180), and two different cultivation methods (ploughed, loosened, RTK in rows, and RTK between rows); these investigations were conducted at the same experimental station. Our results indicate lower tendency for soil respiration, when biofertilizers are applied as compared to commercialNPK fertilizers, which enables to decrease CO2 emission in the environment.We also discuss a unit change indifferent alkali absorption-based methods (Oxitop and Witkamp) to facilitate comparability of recently acquired data with results of previous long-term fertilization experiments.
Journal Article
Nitrous oxide flux from komatsuna (Brassica rapa) vegetated soil: a comparison between biogas digested liquid and chemical fertilizer
Biogas production generates digested slurry as a by-product. It can be used as fertilizer especially after its conversion into digested liquid. A microcosm-based study was conducted in order to compare the effects of single application of digested liquid or chemical fertilizer on N
2
O flux and crop yield of komatsuna vegetable. Analysis revealed that digested liquid-treated soils released almost equal cumulative N
2
O (0.43 g N m
−2
) compared to chemical fertilizer (0.39 g N m
−2
). The uncropped soils treated with the digested liquid and chemical fertilizer released more N
2
O compared to corresponding cropped soils. The N
2
O emission factor and soil mineral N contents were similar for the digested liquid and chemical fertilizer-treated soils. Plant biomass in the first crop after digested liquid application was significantly higher (5.59 g plant
−1
) than that after applied chemical fertilizer (4.78 g plant
−1
); but there was no significant difference for the second crop. Nitrogen agronomic efficiency was improved by the digested liquid compared to chemical fertilizer. This study indicates that cumulative N
2
O flux was similar after application of the digested liquid and chemical fertilizer, while the overall yield from both croppings was increased in the digested liquid-treated soil compared to chemical fertilizer-treated soil.
Journal Article
Effect of biochar on CH4 and N2O emission from soils vegetated with paddy
Biochar is believed to have positive impact on soil properties and plant yield. Due to the presence of C, it can also enhance CH
4
emission in paddy soils. On the other hand, ammonium sulphate can decrease CH
4
emission due to negative impacts on methanogenesis. Keeping these points in view, a pot experiment was conducted to determine the effect of biochar along with ammonium sulphate on CH
4
and N
2
O emission from paddy soil. Analysis revealed that biochar treated soils released more CH
4
compared to untreated. Ammonium sulphate treated soil emitted the highest N
2
O whereas biochar addition decreased its emission significantly. Further, total emission was found to be higher for CH
4
(16.9–34.7 g/m
2
) in comparison to N
2
O (−0.05 to 0.02 g/m
2
) for all treatments. Biochar application has positive impact on plant variables such as panicle number and weight of panicles. This study suggests that biochar application significantly decrease N
2
O emission and increase CH
4
emission possibly due to affecting the availability of organic C in the soil to microbial activity for methanogenesis. Another possibility for enhancing CH
4
emission by following biochar could be attributed to the increase in plant biomass.
Journal Article
Methane flux from paddy vegetated soil: a comparison between biogas digested liquid and chemical fertilizer
A microcosm-based study was conducted to evaluate the effects of application of biogas digested liquid or chemical fertilizer on CH
4
flux, associated methanogenic archaeal community, soil chemical and microbial properties, and aboveground plant biomass in paddy soil. Our results showed that digested liquid application significantly decreased the seasonal and cumulative CH
4
flux compared to chemical fertilizer treatment. The application of digested liquid treatment significantly decreased NH
4
+
-N and soluble total nitrogen content without affecting NO
3
−
-N and microbial biomass nitrogen. The soluble organic carbon and microbial biomass carbon contents were nearly similar for digested liquid and chemical fertilizer treatments. Paddy plant biomass (shoot weight, panicle numbers and weight of panicles) were found to be lower in the digested liquid treated containers but it did not affect the cumulative CH
4
flux g
−1
yield. Denaturing Gradient Gel Electrophoresis gave similar banding patterns indicating no differences in the methanogenic archaeal diversity among the control, digested liquid and chemical fertilizer treated containers. Thus, the observed decrease in CH
4
flux with the application of digested liquid is possibly due to the variation in the soil variables and aboveground plant biomass without affecting the methanogenic archaeal diversity.
Journal Article
A systematic evaluation of machine learning on serverless infrastructure
Recently, the serverless paradigm of computing has inspired research on its applicability to data-intensive tasks such as ETL, database query processing, and machine learning (ML) model
training
. Recent efforts have proposed multiple systems for training large-scale ML models in a distributed manner on top of serverless infrastructures (e.g., AWS Lambda). Yet, there is so far no consensus on the design space for such systems when compared with systems built on top of classical “serverful” infrastructures. Indeed, a variety of factors could impact the performance of training ML models in a distributed environment, such as the optimization algorithm used and the synchronization protocol followed by parallel executors, which must be carefully considered when designing serverless ML systems. To clarify contradictory observations from previous work, in this paper we present a systematic comparative study of serverless and serverful systems for distributed ML training. We present a
design space
that covers design choices made by previous systems on aspects such as optimization algorithms and synchronization protocols. We then implement a platform,
LambdaML
, that enables a
fair
comparison between serverless and serverful systems by navigating the aforementioned design space. We further improve
LambdaML
toward automatic support by designing a hyper-parameter tuning framework that leverages the ability of serverless infrastructure. We present empirical evaluation results using
LambdaML
on both single training jobs and multi-tenant workloads. Our results reveal that there is no “one size fits all” serverless solution given the current state of the art—one must choose different designs for different ML workloads. We also develop an
analytic model
based on the empirical observations to capture the cost/performance tradeoffs that one has to consider when deciding between serverless and serverful designs for distributed ML training.
Journal Article