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Comparative Study on Pretreatment Processes for Different Utilization Purposes of Switchgrass.

ABSTRACT: Switchgrass (Panicum virgatum, L., Poaceae) with the advantages of high cellulose yield, and high growth even under low input and poor soil quality, has been identified as a promising candidate for production of low-cost biofuels, papermaking, and nanocellulose. In this study, 12 chemical pretreatments on a laboratory scale were compared for different utilization purposes of switchgrass. It was found that the pretreated switchgrass with sodium hydroxide showed considerable potential for providing mixed sugars for fermentation with 11.10% of residual lignin, 53.85% of residual cellulose, and 22.06% of residual hemicellulose. The pretreatment with 2.00% (v/v) nitric acid was the best method to remove 78.37% of hemicellulose and 39.82% of lignin under a low temperature (125 °C, 30 min), which can be used in the production of nanocellulose. Besides, a completely randomized design analysis of switchgrass pretreatments provided the alternative ethanol organosolv delignification of switchgrass for the papermaking industry with a high residual cellulose of 58.56%. Finally, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FT-IR) were carried out to confirm the changes in functional groups, crystallinity, and thermal behavior of the three materials, respectively, from the optimal pretreatments.

SUBMITTER: Wang F

PROVIDER: S-EPMC7482092 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature

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Comparative Study on Pretreatment Processes for Different Utilization Purposes of Switchgrass.

Wang Fan F Shi Dongxiang D Han Ju J Zhang Ge G Jiang Xinglin X Yang Mingjun M Wu Zhenying Z Fu Chunxiang C Li Zhihao Z Xian Mo M Zhang Haibo H

ACS omega 20200827 35

Switchgrass (<i>Panicum virgatum</i>, L., Poaceae) with the advantages of high cellulose yield, and high growth even under low input and poor soil quality, has been identified as a promising candidate for production of low-cost biofuels, papermaking, and nanocellulose. In this study, 12 chemical pretreatments on a laboratory scale were compared for different utilization purposes of switchgrass. It was found that the pretreated switchgrass with sodium hydroxide showed considerable potential for p ...[more]

PMID: 32923758

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Project description:BACKGROUND:Fine milling of dry lignocellulosic biomass, without prior chemical pretreatment, can produce a high percent theoretical yield of sugars during subsequent enzymatic saccharification. However, the high sugar yields, necessary for a commercial biofuels process, are costly, with the milling energy input, necessary to achieve such yields even exceeding the energy content of the biomass. In this study, we show that low moisture gaseous ammonia pretreatment of switchgrass, in advance of the milling step, significantly reduces the milling energy required to give high sugar titers. RESULTS:We have found that the increase in monomeric sugar yields upon enzymatic saccharification of ball-milled, but not chemically treated switchgrass, is more closely tied to the formation of crystallites of cellulose with a negative linear dependence on the coherent domain size than to a decrease in particle size or to an increase in surface area of the biomass. The milling energy required to reach ~80 % of theoretical yield of glucose under these conditions is intolerably high, however, approximating two times the energy content of the biomass. Two different low moisture content ammonia pretreatments, prior to milling, significantly reduce the required milling energy (four to eightfold, depending on the pretreatment). These involve either heating the biomass at 150-160 °C for 1 h at 10 wt% gaseous ammonia or incubating at room temperature for 9 days at 20 wt% gaseous ammonia, the latter mimicking potential treatment during biomass storage. We have tested this combination of pretreatment and milling on switchgrass using a variety of milling methods, but mostly using ball and attritor milling. In the case of the high-temperature gaseous ammonia treatment followed by attritor milling, the increase in the monomeric sugar yield upon saccharification shows a negative linear dependence on the second or third power of the cellulose crystalline coherent domain size, implying that the surfaces as well as the ends of the cellulose fibrils are accessible to cellulolytic enzymes. CONCLUSIONS:The combination of knife milling, low moisture gaseous ammonia pretreatment followed by attritor milling that costs only ~5 % of the energy content of the biomass for a total energy input of ~11 % of the biomass energy content, is capable of delivering high sugar titers upon enzymatic saccharification. These results show, therefore, how to better integrate a mechanochemical step into the pretreatment of switchgrass in a commercial biomass to biofuels conversion process.

Project description:BackgroundHospital readmissions is an increasingly serious international problem, associated with higher risks of adverse events, especially in elderly patients. There can be many causes and influential factors leading to hospital readmissions, but they are often closely related, making hospital readmissions an overall complex area. In addition, a comprehensive coordination reform was introduced into the Norwegian healthcare system in 2012. The reform changed the premises for readmissions with economic incentives enhancing early transfer from secondary to primary care, making research on readmissions in the municipalities more urgent than ever. General practitioners (GPs) and nursing home physicians, have traditionally held a gatekeepers function in hospital readmissions from the municipal healthcare service, as they are the main decision-makers in questions of hospital readmissions. Still, the GPs' gatekeeper function is an under-investigated area in hospital readmission research. The aim of the study was to increase knowledge about factors that lead to hospital readmissions among elderly in municipal healthcare, with special attention to GPs' and nursing home physicians' decision making.MethodThe study was conducted as a comparative case study. Two municipalities affiliated with the same hospital, but with different readmission rates were recruited. Twenty GPs and nursing home physicians from each municipality were recruited and interviewed. Forty hours of observation were conducted during the huddles in one long-term and one short-term nursing home in each municipality.ResultsSeven themes describing how different factors influence physicians' decision-making in the hospital readmission process in two municipalities were identified. Poor communication, continuity and information flow account for hospital readmissions in both municipalities. Several factors, including nurse staffing and competence, patients and their families, time constraints and experience affected physicians' decision-making.ConclusionCommunication, continuity and information flow contributed to hospital readmissions in both municipalities. The cross-case analysis revealed slight differences between municipalities. More research focusing on GPs' and nursing home physicians' decision-making, nursing home nurses and home care nurses' experience of hospital readmissions and discharges is needed.

Dataset Information

Comparative Study on Pretreatment Processes for Different Utilization Purposes of Switchgrass.

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Comparative Study on Pretreatment Processes for Different Utilization Purposes of Switchgrass.

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