Shan-Fei Fu

The thermophilic (55 °C) microaerobic pretreatment of corn straw for anaerobic digestion

Microaerobic process has been proven to be an alternative pretreatment for the anaerobic digestion (AD) process in several studies. In this study, the effect of thermophilic microaerobic pretreatment (TMP) on the AD of corn straw was investigated. Results indicated that TMP process obviously improved the methane yield. The maximum methane yield was obtained at the oxygen loads of 5ml/g VSsubstrate, which was 16.24% higher than that of untreated group. The modified first order equation analysis showed the TMP process not only accelerated the hydrolysis rates but also reduced the lag-phase time of AD process. The structural characterization analysis showed cellulosic structures of corn straw were partly disrupted during TMP process. The crystallinity indexes were also decreased. In addition, large or destroyed pores and substantial structural disruption were observed after pretreatment. The results showed that TMP is an efficient pretreatment method for the AD of corn straw.

Methane hydrate formation with surfactants fixed on the surface of polystyrene nanospheres

To improve the application of surfactants in methane hydrate formation, sodium dodecyl sulfate (SDS) was fixed on the surface of polystyrene nanospheres (named as SDS@PSNS). SDS@PSNS resulted in a shorter induction period of hydrate formation compared to SDS. With SDS@PSNS as a promoter, hydrates formed mainly at the bottom of the reactor with a much higher apparent density and higher methane consumption, and during the hydrate dissociation period, less foam was generated. In addition, the recycling experiments showed high stability and good recycling performance of SDS@PSNS in seven methane hydrate formation–dissociation cycles.

The chemical properties and microbial community characterization of the thermophilic microaerobic pretreatment process

Thermophilic microaerobic pretreatment (TMP) was recently reported as an efficient pretreatment method of anaerobic digestion (AD). In this study, the chemical properties and microbial community were characterized to reveal how TMP working. Compared with thermophilic treatment under anaerobic condition (TMP0), cellulase activity obviously improved under microaerobic condition (TMP1), which was 10.9-49.0% higher than that of TMP0. Reducing sugar, SCOD and VFAs concentrations of TMP1 were 2.6-8.9%, 1.8-4.8% and 13.8-24% higher than those of TMP0, respectively. TMP gave obvious rise to phylum Firmicutes, which associated with extracellular enzymes production. The proportion of class Bacilli (belongs to phylum Firmicutes and mainly acts during hydrolysis) in TMP1 was 124.89% higher than that of TMP0, which reflected the greater hydrolytic ability under microaerobic condition. The improved abundance of phylum Firmicutes (especially class Bacilli, order Bacillales) under microaerobic condition could be the fundamental reason for the improved AD performance of thermophilic microaerobic pretreated corn straw.

Secondary thermophilic microaerobic treatment in the anaerobic digestion of corn straw

Thermophilic microaerobic pretreatment (TMP) has been proved to be an alternative pretreatment method during anaerobic digestion (AD) of corn straw. In this study, in order to improve the fermentation efficiency during late AD stage, improve the methane yield and volatile solid (VS) removal efficiency, a secondary thermophilic microaerobic treatment (STMT) was applied in the late AD stage of corn straw. Results showed STMT obviously improved the fermentation efficiency, methane yield and VS removal efficiency. The maximum methane yield and maximum VS removal efficiency were simultaneously obtained when the oxygen loads during STMT was 10 ml/g VS (VS of residual substrate). The maximum methane yield was 380.6 ml/g VS(substrate), which was 28.45% and 10.61% higher than those of untreated and once thermophilic microaerobic pretreated samples, respectively. The maximum VS removal efficiency was 81.85%, which was 29.43% and 17.23% higher than those of untreated and once thermophilic microaerobic pretreated samples, respectively.

Elimination of methane in exhaust gas from biogas upgrading process by immobilized methane-oxidizing bacteria

Biogas upgrading is essential for the comprehensive utilization of biogas as substitute of natural gas. However, the methane in the biogas can be fully recovered during the upgrading process of biogas, and the exhaust gas produced during biogas upgrading may contain a very low concentration of methane. If the exhaust gas with low concentration methane releases to atmosphere, it will be harmful to environment. In addition, the utilization of large amounts of digestate produced from biogas plant is another important issue for the development of biogas industry. In this study, solid digestate was used to produce active carbon, which was subsequently used as immobilized material for methane-oxidizing bacteria (MOB) in biofilter. Biofilter with MOB immobilized on active carbon was used to eliminate the methane in exhaust gas from biogas upgrading process. Results showed porous active carbon was successfully made from solid digestate. The final methane elimination capacity of immobilized MOB reached about 0.13molh-1m-3, which was more 4 times higher than that of MOB without immobilization.

Effects of organic loading rate on biogas production from macroalgae: Performance and microbial community structure

Macroalgae biomass has been considered as a promising feedstock for biogas production. In order to improve the efficiency of anaerobic digestion (AD) of macroalgae, semi-continuous fermentation was conducted to examine the effects of organic loading rate (OLR) on biogas production from Macrocystis pyrifer. Results showed that, under OLRs of 1.37, 2.74, 4.12 and 6.85kgVSsubstrate/(m3·d), the average unit biogas yields were 438.9, 477.3, 480.1 and 188.7mL/(gVSsubstrated), respectively. It indicated that biogas production was promoted by the increased OLR in an appropriate range while inhibited by the OLR beyond the appropriate range. The investigation on physical-chemical parameters revealed that unfavorable VFAs concentration, pH and salinity might be the main causes for system failure due to the overrange OLR, while the total phenols failed to reach the inhibitory concentration. Microbial community analysis demonstrated that several bacterial and archaeal phyla altered with increase in OLR apparently.

Comparison of thermophilic microaerobic and alkali pretreatment of sugarcane bagasse for anaerobic digestion

In this study, the effects of thermophilic microaerobic pretreatment (TMP) and alkali pretreatment (AP) on anaerobic digestion (AD) of sugarcane bagasse were investigated. Results showed TMP was efficient at crystallinity disruption and AP was efficient at lignin removal. The maximum methane yield was obtained when the oxygen loads during TMP was 10 ml g−1 VSsubstrate (TMP2), which was 15.7% and 29.3% higher than those of AP and the sample without pretreatment (WP), respectively. Accordingly, the VS removal efficiency of TMP2 was 5.4% and 17.4% higher than those of AP and WP, respectively. In addition, lag-phase time of TMP2 was 1.55 and 3.82 days shorter than those of AP and WP, respectively. Technical digestion time (T90) of AP was 49 days, which was 10 and 7 days less than those of TMP2 and WP, respectively. In addition to AP, TMP is an alternative and efficient pretreatment method in the AD of sugarcane bagasse.

Contamination Status of Hexachlorobenzene (HCB) in Sandstorm Depositions from Beijing and the Origination Region

In China, sandstorms play an important role in the long-range atmospheric transport and deposition of hexachlorobenzene (HCB). Concentrations of HCB in sandstorm depositions sampled from Beijing and the origination region were measured to reveal HCB levels during atmospheric transport. The results suggested a constant level of HCB during atmospheric transport. The values were close to environmental background values indicating that no potential source of HCB existed along the transport route. A tendency for HCB levels in Beijing to increase from north to east was also observed, which was probably due to the influence of wind speed and industrial zone distribution.

Improved methane removal in exhaust gas from biogas upgrading process using immobilized methane-oxidizing bacteria

Methane in exhaust gas from biogas upgrading process, which is a greenhouse gas, could cause global warming. The biofilter with immobilized methane-oxidizing bacteria (MOB) is a promising approach for methane removal, and the selections of inoculated MOB culture and support material are vital for the biofilter. In this work, five MOB consortia were enriched at different methane concentrations. The MOB-20 consortium enriched at the methane concentration of 20.0% (v/v) was then immobilized on sponge and two particle sizes of volcanic rock in biofilters to remove methane in exhaust gas from biogas upgrading process. Results showed that the immobilized MOB performed more admirable methane removal capacity than suspended cells. The immobilized MOB on sponge reached the highest methane removal efficiency (RE) of 35%. The rough surface, preferable hydroscopicity, appropriate pore size and particle size of support material might favor the MOB immobilization and accordingly methane removal.

The thermophilic (55 degrees C) microaerobic pretreatment of corn straw for anaerobic digestion (vol 175, pg 203, 2015)

Chinese Acad Sci, Qingdao Inst Bioenergy & Bioproc Technol, 189 Songling Rd, Qingdao 266101, Shandong, Peoples R China