[Degradation Characteristics of Spectral Analysis of Straw Nursery Containers in Situ Soil Culture].

This paper aimed to reveal the degradation behavior of a new type of biodegradable containers. The biodegradable containers, which was made of modified soybean adhesive and straw, was processed in situ biodegradation under natural condition. The physicochemical property and microstructure of straw nursery containers treated and untreated were characterized with Cellulose Tester, Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope - Energy Dispersive X-ray Spectroscopy (SEM-EDS), and Thermo-gravimetry Analysis (TGA), respectively. The results indicated that the content of cellulose, hemicellulose and lignin of treated specimen decreased to 21.43%, 21.41% and 9.54% from 29.03%, 30.44% and 12.52%, respectively, comparing with those of untreated straw nursery container. FTIR analysis revealed that the ester and fat bond have been ruptured, and the aromatic characteristic peak became weakened. SEM-EDS spectrum showed the microfibril chain in the container has been fragmentation, and the soybean adhesive was also degradation. The surface of container appeared oxidization degradation. TGA analysis showed that a large number of small molecules have been produced in the process of degradation and the thermo-stability of treated samples improved.

Biochar increases arsenic release from an anaerobic paddy soil due to enhanced microbial reduction of iron and arsenic.

Previous studies have shown that biochar enhances microbial reduction of iron (Fe) oxyhydroxide under anaerobic incubation. However, there is a lack of data on its influence on arsenic (As) release from As-contaminated paddy soils. In this study, paddy soil slurries (120 mg As kg-1) were incubated under anaerobic conditions for 60 days with and without the addition of biochar (3%, w/w) prepared from rice straw at 500 °C. Arsenic release, Fe reduction, and As fractionation were determined at 1, 10, 20, 30, and 60 d, while Illumina sequencing and real-time PCR were used to characterize changes in soil microbial community structure and As transformation function genes. During the first month of incubation, As released into soil solution increased sharply from 27.9 and 55.9 to 486 and 630 µg kg-1 in unamended and biochar amended slurries, with inorganic trivalent As (AsIII) being the dominant specie (52.7-91.0% of total As). Compared to unamended slurries, biochar addition increased As and ferrous ion (Fe2+) concentrations in soil solution but decreased soil As concentration in the amorphous Fe/Al oxide fraction (F3). Difference in released As between biochar and unamended treatments (ΔAs) increased with incubation time, showing strong linear relationships (R2 = 0.23-0.33) with ΔFe2+ and ΔF3, confirming increased As release due to enhanced Fe reduction. Biochar addition increased the abundance of Fe reducing bacteria such as Clostridum (27.3% vs. 22.7%), Bacillus (3.34% vs. 2.39%), and Caloramator (4.46% vs. 3.88%). In addition, copy numbers in biochar amended slurries of respiratory As reducing (arrA) and detoxifying reducing genes (arsC) increased 19.0 and 1.70 fold, suggesting microbial reduction of pentavalent As (AsV) adsorbed on Fe oxides to AsIII, further contributing to increased As release.

Biochar decreases nitrogen oxide and enhances methane emissions via altering microbial community composition of anaerobic paddy soil.

Biochar application to agricultural soil is an appealing approach to mitigate nitrous oxide (N2O) and methane (CH4) emissions. However, the underlying microbial mechanisms are unclear. In this study, a paddy soil slurry was incubated anaerobically for 14d with biochar amendments produced from rice straw at 300, 500, or 700°C (B300, B500, and B700) to study their influences on greenhouse gas emissions. Illumina sequencing was used to characterize shift of soil bacterial and archaeal community composition. After peaking at day 1, N2O emission then sharply decreased to low levels while CH4 started to emit at day 3 then continually increased with incubation. Compared to control soil (57.9mgkg-1 soil), B300, B500, and B700 amendments decreased N2O peak emission to 17.9, 1.28, and 0.59mgkg-1, mainly due to increased soil pH. In contrast, the amendments enhanced CH4 production from 58.2 to 93.4, 62.6, and 63.4mgkg-1 at day 14 due to increased soil dissolved organic carbon. Abundance of denitrifying bacteria (e.g., Bacilli, 7.07-13.6 vs. 16.9%) was reduced with biochar amendments, especially with B500 and B700, contributing to the decreased N2O emissions. However, larger pore size of B500 and B700 (surface area of 68.1 and 161m2g-1) than B300 (4.40m2g-1) favored electron transfer between bacteria and iron minerals, leading to increased abundance of iron-reducing bacteria, (e.g., Clostridia, 48.2-50.6 vs. 33.3%), which competed with methanogens to produce CH4, thereby leading to lower increase in CH4 emission. Biochar amendments with high pH and surface area might be effective to mitigate emission of both N2O and CH4 from paddy soil.

[Effect of pretreatment on storage and biogas production of baling wheat straw].

Long-term storage of crop straw is very important for biogas plant while pretreatment is always used to improve biogas production of crop straw. Feasibility of integrating the storage with pretreatment of baling wheat straw was studied. Changes of physicochemical properties and the biogas productivity of wheat straw obtained before and after 120 days storage were analyzed. The results showed that it was feasible to directly bale wheat straw for storage (control) and storage treatment had little effect on the physicochemical properties, structure and biogas productivity of wheat straw. After 120 day's storage, biogas production potential of the surface wheat straw of pile was decreased by 7.40%. Integrating NaOH pretreatment with straw storage was good for biogas production of wheat straw and the total solid (TS) biogas yield was increased by 7.02%-8.31% (compared to that of wheat straw without storage) and 5.68% -16.96% (compared to that of storage without alkaline pretreatment), respectively. Storage with urea treatment was adverse to biogas production of wheat straw and the contents of cellulose and hemicellulose of wheat straw were decreased by 18.25%-27.22% and 5.31%-16.15% and the TS biogas yield was decreased by 2.80%-7.71% after 120 day's storage. Exposing wheat straw to the air during the storage process was adverse to the conserving of organic matter and biogas utilization of wheat straw, but the influence was very slight and the TS biogas yield of wheat straw obtained from pile surface of control and urea treatment was decreased by 7.40% and 4.25%, respectively.

[Effect of alkaline post-treatment on physicochemical property of digested Spartina alterniflora].

Alkaline treatment is widely used for improving biogas production for lignocellulosic materials. This study was conducted to investigate the effect of alkaline treatment on physicochemical property of digested Spartina alterniflora (DSA). Fourier Transform Infrared Spectroscopy (FTIR), X-Ray diffraction patterns, proton Nuclear Magnetic Resonance Spectroscopy (1H-NMR), solid-state 13C-NMR Spectroscopy and some general indicators were used to analyze changes of the lignocellulosic structure and composition of NaOH-treated digested Spartina alterniflora. The results showed that, after NaOH treatment, surface lignin and some carbohydrate were destructed into lignin fragment, organic acids and some other small molecular organic matter, but the skeleton structure of lignin and cellulose of DSA were not destructed significantly. The crystalline of cellulose of DSA was transferred into biodegradable forms and content of crystalline of DSA and cellulose were increased after NaOH treatment. The results of 13C-NMR showed that methyl (CH3) and carboxylic C(COOH) groups of DSA were decomposed significantly.

[Methane production by anaerobic co-digestion of chicken manure and Spartina alterniflora residue after producing methane].

The characteristics of Spartina alterniflora residue after producing methane (SAR) digested alone and co-digestion of various proportions of chicken manure and SAR were investigated by batch model at 35 degrees C +/- 1 degrees C. The initial total solid (TS) loading of all treatments was 8.0%. The results indicated that there was still some biogas produced by SAR with TS biogas yield of 107.25 mL x g(-1) and average methane content of 76.92%. The cellulose crystallinity of re-digested SAR was destructed by anaerobic microorganisms, and the destruction rate was 5.55%. Co-digestion meliorated the environment where microorganisms lived in and increased the cumulative biogas yield. When the ratio of chicken manure to SAR was 4 : 1, the cumulative biogas yield was highest while the cumulative biogas yield of T1 (the rate of chicken manure to SAR is 5 : 0 based on TS), T3-T6 (the rate of chicken manure to SAR are 3 : 2, 2 : 3, 1 :4 and 0 : 5 based on TS, respectively) were 61.31%, 62.09%, 52.15%, 39.74% and 31.67% of it. The anaerobic fermentation type of co-digestion is mix acid type fermentation. Co-digested with chicken manure promoted the destruction of cellulous crystallinity by 1.13% - 21.61% and especially when the rate of chicken manure to SAR was 4 : 1.

[Effect of NaOH-treatment on dry-thermophilic anaerobic digestion of Spartina alterniflora].

In order to improve the biotransformation rate of lignocellulosic materials, sodium hydroxide (NaOH) was widely used to pretreat lignocellulosic materials. Effect of NaOH-treatment on dry-thermophilic anaerobic digestion of Spartina alternflora was studied by batch model under the temperature of 55 degrees C +/- 1 degrees C, at the initial total solid loading (TSL) of 20%. The results indicated that biogas production was inhibited by NaOH-treatment and improved by NaOH-treatment with water washed. The cumulative biogas yield of control (CK), NaOH-treated and NaOH-treated with water washed (NaOH + water) were 268.35 mL/g, 205.76 mL/g and 299.97 mL/g, respectively. The methane content of CK and NaOH + water treatments kept stable while fluctuation of NaOH-treated treatment during anaerobic digestion process was observed. Compared with CK and NaOH + water treatments, methane content of NaOH-treated treatment was improved by 5.30%. The content of hemi-cellulose and cellulose of S. alternifora decreased while content of lignin of S. alterniflora increased after 51-day anaerobic digestion. The crystallinity of cellulose of S. alterniflora increased after NaOH-treatment which was consistent to the result of FTIR. The lignocellulosic structure was destroyed and the biodegradability of S. alterniflora was increased by NaOH pretreatment. However, the amount of Na+ was taken into the anaerobic system, besides the high Na+ content in the plant itself which inhibited the anaerobic microorganisms. Therefore, NaOH-treatment is considered to be unsuitable for the anaerobic digestion of S. alterniflora.

[Effect of NaOH-treatment on advanced anaerobic biogasification of Spartina alterniflora].

In order to improve the biotransformation rate of Sparnina alterniflora, effect of NaOH-treatment on anaerobic dry-mesophilic digestion of Spartina alterniflora and feasibility of NaOH-treatment as a pretreatment of biogas residues of Spartina alterniflora for advanced anaerobic biogasification were conducted under lab-scale conditions. The results indicated that there was less improvement to biogas yield with NaOH-treatment and the cumulative biogas yield of Spartina alterniflora was 358.94 mL/g TS which was 92.42% to that of control (CK). However, the average methane content was improved slightly with 1.84% improvement. After solid-state pretreatment with 5% NaOH solution for 48 h, the biogas residue of Spartina alterniflora was used for advanced biogasification. This experiment was conducted under 35 degrees C +/- 1 degrees C with initial total solid loading of 8%. The cumulative biogas yield was 209.73 mL/g TS with 70.78% of average methane content, but the biotransformation rate was only 23.29% which was much lower than that of Spartina alterniflora. The fermentation type was propionic acid type fermentation. After two-phase fermentation treatment, cellulose content was decreased significantly while lignin and hemicellulose content were increased. The crystalinity of cellulose of biogas residue decreased after two-phase anaerobic fermentation which was consistent to result of FTIR. The comprehensive analysis of experiment indicated that biogas residue of Spartina alterniflora was still a good material for biogas production and NaOH-treatment was a good pretreatment for biogas production.