Straw Changes Research Articles

Chemically and Physically Pretreated Straw in Moderate Conditions: Poor Correlation between Biogas Production and Commonly Used Biomass Characterization

Straw is a substantial agricultural by-product for biogas production. Hydrolysis of straw is found to be a rate-limiting step during its anaerobic digestion and could be enhanced by pretreatment. In this paper, the effect of various combinations of particle size reduction, autoclaving, and low-level Fenton reaction was studied on straw for biogas production. Grinding of straw contributed to the maximum increase in the biomethane potential. Only Fenton or only the autoclave process improves the kinetics slightly but does not considerably improve the biomethane potential. Combining autoclaving and low-concentration Fenton pretreatment considerably improves the BMP values. Lignin content, CHNSO elemental analysis, Scanning Electronic Microscopy (SEM), Simon’s staining, infrared spectroscopy (DRIFT and ATR), Nuclear magnetic resonance spectroscopy, and wide-angle X-ray diffraction analysis (WAXD) were used to characterize the physical and chemical changes of straw due to pretreatment. Results show a poor correlation between biogas production and the different physical and chemical biomass characteristics. It makes it difficult to explain the outcome of various pretreatment methods applied to biomass. Without further improvement and development of analytical techniques, the prediction of the biomethane potential of a feedstock with the aid of pretreatment can only be considered in case-by-case studies.

Thermal induced changes of rice straw phytolith in relation to arsenic release: A perspective of rice straw arsenic under open burning

On-site open burning is a common practice for handling rice straw, but its negative impacts, e.g., biomass loss and air pollution, are largely debated worldwide. To address the negative effects of open burning, many efforts have been made to ‘ignite’ worldwide bans. However, these bans are likely based on a singular view in which some positive aspects of open burning are overlooked. In this study, we aimed to determine the thermal-induced changes of straw and straw arsenic (As) under open burning and heat-treatments (in the temperature range from 300 to 900 °C). It was found that silica phase in rice straw (so-called phytolith) can encapsulate As in its structure. Open burning or heat-treatment of straw resulted in a tighter association of As and phytolith, thereby reducing dissolution of As. We proposed an opinion that open burning causes air pollution, but it can increase the activity of phytolith in sequestrating As, enabling delayed As cycle in rice ecosystems. The combat of on-site open burning of rice straw to reduce air pollution will alter straw handling routines, thereby changing the cycle of straw phytolith and the route of straw As.

Cellulase production by Aspergillus fumigatus MS13.1 mutant generated by heavy ion mutagenesis and its efficient saccharification of pretreated sweet sorghum straw

Abstract Developing a potential strain with high cellulase yield and stable fermenting performance is an imperative way to overcome the enzyme costs limitation. A cellulose degrading fungus was isolated from the agricultural wastes and identified as A. fumigatus MS13.1. For further improving the production capacity of enzyme, the original A. fumigatus MS13.1 was subjected to mutagenesis with heavy-ion beams and mutant MS160.53 was selected. The MS160.53 exhibited higher filter paper (1.81 IU/ml) and β-glucosidase (1.65 IU/ml) activities than parent strain MS13.1, which increased by 40.3% and 15.1%, respectively. Soluble protein concentrations in supernatants from strain MS160.53 were reached 1.497 mg/ml at 240 h which were higher than that in the reported literature of A. fumigatus. In addition, the SDS-PAGE profiles revealed that more enzymes of mutant were secreted during fermentation compared with parent strain MS131.1. The crude enzyme were further applied for saccharification of pretreated sweet sorghum straw, where a dosage of 5 IU/g FPase produced high reducing sugar titers of 789.75 mg/g. SEM images revealed the obviously microstructural changes of straw after the pretreatment and enzymatic hydrolysis. Thus, the enzyme cocktails produced by A. fumigatus MS160.53 has great potential for the saccharification of pretreated biomass and further bioethanol production.

Feasibility of vacuum consolidation in managing dredged slurries with wheat straw as drainage channels

It is suggested to use wheat straw as both vertical and horizontal drainage materials when using vacuum consolidation method to process dredged slurry in this paper. To verify the feasibility of this proposal, compression and hydrulic conductivity test on wheat straw and vacuum consolidation tests on slurry using wheat straw as drainage materials were conducted. The results show that the compression process of wheat straw is composed of instantaneous settlement and creep. The density of wheat straw changes from 20 kg/m3 to 200 kg/m3 as vertical stress varies from 5 kPa to 100 kPa. The creep rate increases to maximum when vertical stress reaches 60 kPa and then decreases with as vertical stress further increases. The hydrulic conductivity coefficient of wheat straw is changed between 104 cm/s and 101 cm/s, which decreases linearly as density increases in semi-logarithmic coordinates (hydraulic conductivity in log scale). In vacuum consolidation tests, the settlement, water content, and undrained shear strength of slurry proceeded by vacuum consolidation with wheat straw as drainage materials are similar to those obtained by using PVD and sand as drainage materials. All the results obtained by this paper show that it is feasibility to use wheat straw as vertical and horizontal drainage materials in vacuum consolidation.