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In this study, levulinic acid (LA) was produced from rice straw biomass in co-solvent biphasic reactor system consisting of hydrochloric acid and dichloromethane organic solvent. The modified protocol achieved a 15% wt LA yield through the synergistic effect of acid and acidic products (auto-catalysis) and the designed system allowed facile recovery of LA to the organic phase. Further purification of the resulting extractant was achieved through traditional column chromatography, which yielded a high purity LA product while recovering ∼85% wt. Upon charcoal treatment of the resultant fraction generated an industrial grade target molecule of ∼99% purity with ∼95% wt recovery. The system allows the solvent to be easily recovered, in excess of 90%, which was shown to be able to be recycled up to 5 runs without significant loss of final product concentrations. Overall, this system points to a method to significantly reduce manufacturing cost during large-scale LA preparation.

To find an appropriate method for sulfate-rich wastewater containing ethanol and acetate with COD/sulfate ratio of 1, a UASB reactor was operated for more than 180 days. The influences of HRT (hydraulic retention time) and OLR (organic loading rate) on organics and sulfate removal, gas production, and electrons utilization were investigated. The sludge activity and microorganism composition were also determined. The results indicated that this system removed more than 80% of COD and 30% of sulfate with HRT above 6h and OLR below 12.3 gCOD/L d. Further HRT decrease caused volatile fatty acids accumulation and performance deterioration. Except at HRT of 2h, COD and electron flow were mostly utilized by methane-producing archaea (MPA), and methane yield remained in the range of 0.18-0.24 LCH4/gCOD. Methane was mainly generated by Methanosaeta concilii GP6 with acetate as substrate, whereas sulfate was mainly reduced by incomplete-oxidizing Desulfovibrio species with ethanol as substrate.

To fix CO2 emissions efficiently from flue gas of coal-fired power plants, the culture medium, light intensity and bioreactors were comprehensively optimized in the process of CO2 fixation by Chlorella PY-ZU1. To make up for relative insufficiency of nutrients (except for the carbon source) resulting from continuous bubbling of 15% CO2, three chemicals were added into the culture to optimize the molar ratios of nitrogen to carbon, phosphorus to carbon, and magnesium to carbon in culture from 0.17 to 0.69, from 0.093 to 0.096, and from 0.018 to 0.030, respectively. Such adjustments led to a 1.25-fold increase in biomass (from 2.41 to 5.42 g L(-1)). By enhancing light intensity from 4500 to 6000 lux, the peak growth rate of Chlorella PY-ZU1 increased by 99% and reached to 0.95 g L(-1) day(-1). Use of a multi-stage sequential bioreactor notably improved the peak CO2 fixation efficiency to 85.6%.

The rapidly evolving global warming is triggering all levels of actions to reduce industrial carbon emissions, while capturing carbon dioxide of industrial origin via microalgae has attracted increasing attention. This article attempted to offer preliminary analysis on the carbon capture potential of microalgal cultivation. It was shown that the energy consumption-associated with operation and nutrient input could significantly contribute to indirect carbon emissions, making the microalgal capture of carbon dioxide much less effective. In fact, the current microalgae processes may not be environmentally sustainable and economically viable in the scenario where the carbon footprints of both upstream and downstream processing are considered. To address these challenging issues, renewable energy (e.g., solar energy) and cheap nutrient source (e.g., municipal wastewater) should be explored to cut off the indirect carbon emissions of microalgae cultivation, meanwhile produced microalgae, without further processing, should be ideally used as biofertilizer or aquafeeds for realizing complete nutrients recycling.

Increasing energy demand and depleting fossil fuel sources have intensified the focus on biofuel production. Microalgae have emerged as a desirable source for biofuel production because of high biomass and lipid production from waste water source. In this study, five microalgae were isolated from effluents of Nisargruna biogas plants. These isolates were identified based on morphology and partial 18S and 23S rRNA gene sequences. Growth and lipid accumulation potential of these microalgae were investigated. One isolate, Chlorella sp. KMN3, accumulated high biomass (1.59 ± 0.05 g L(-1)) with moderate lipid content (20%), while another isolate Monoraphidium sp. KMN5 showed moderate biomass accumulation of 0.65 ± 0.05 g L(-1) with a very high (35%) lipid content. The fatty acid methyl esters mainly composed of C-16:0, C-18:0, C-18:1 and C-18:2. This observation makes these microalgae immensely potential candidate for biodiesel production using the effluent of a biogas plant as feed stock.

The objective is to investigate the release characteristics of potassium (K) and chlorine (Cl) for torrefied wheat straw during a combined pyrolysis-combustion system. Powder and flake wheat straw samples were torrefied at different temperature of 200-300 ℃. The basic characteristics of torrefied samples and the K and Cl release rates of torrefied samples and their char samples derived from pyrolysis at 400-800 ℃ were analyzed and characterized. The results indicated that release rate of Cl was significantly higher than that of K under the same torrefaction conditions. In order to keep most of K and Cl remaining in biochar as well as the volatiles were completely released, the pyrolysis temperature of 700 ℃ for pyrolysis-combustion system was suitable. The total release rate of K and Cl at the pyrolysis temperature of 700 ℃ both exhibited a change trend of decreasing first and then increasing with the increase of torrefaction severity.

The aim of this work was to study the responses of aerobic granulation process to antibiotics and investigate the antibiotics and antibiotic-resistant bacteria (ARB) removal and transport. Results showed that aerobic granular sludge (AGS) was dominant in the bioreactor at day 45, and the relatively high protein content from tightly bound extracellular polymeric substances (TB-EPS) facilitated aerobic granulation and maintained biomass stabilization. The protein contents in EPS and TB-EPS were positively correlated with relative hydrophobicity, thereby improving the adsorption capacity among hydrophobic particles. The chemical oxygen demand (COD), NH3-N, and total N removal efficiencies were 98.0%, 97.0%, and 92.4%, respectively. Five antibiotics, including kanamycin, tetracycline, ciprofloxacin, ampicillin, and erythromycin, were examined in piggery wastewater, with concentrations up to the concentration range of 29.4-44.1 µg/l, and the total antibiotics removal rate reached up to 88.4% ± 4.5%. A total of 5.2% of the total antibiotics were discharged from bioreactor, and 62.5% of the total antibiotics were degraded, and 32.3% of total antibiotics were adsorbed by aerobic granules. The presence of antibiotics rarely exhibited an influence on AGS formation, and the relatively high microbial activity of aerobic granules was beneficial to antibiotics removal. The ARB removal rate increased up to 89.4% ± 3.3%, but a large amount of ARB was enriched in aerobic granules.

Recently, upflow microaerobic sludge blanket (UMSB) system has been developed to remove ammonium and organic matter simultaneously. This study aims to establish influent and operational conditions promoting anammox-based nitrogen removal process in the UMSB reactor by using a modified Activated Sludge Model. Experiments were performed on a laboratory-scale UMSB reactor treated piggery wastewater for over two years. With the experimentally determined model parameters, the established model well simulated the UMSB reactor performance. The maximum anammox growth rate was calibrated to be 0.41 d-1 at 35 °C. Further simulations showed that UMSB reactor operated with high influent organics or nitrogen loading rates at temperature above 15 °C can achieve efficient nitrogen removal (>70%). The nitrogen loading over 0.6 kg N/(m3·d)) significantly favors anammox activity. UMSB could also be a promising system for nitrogen removal from low-strength ammonium wastewater with fluctuated COD influence. These results provide support to UMSB design and operational optimization.

This study reports the effects of polar (acetone/methanol) and non-polar (chloroform/hexane) solvents on lipid yield, fatty acids methyl esters (FAMEs) composition, and biodiesel properties of microalgae. The lipids yield extracted by hexane and chloroform (100.01 and 94.33 mg/g) were higher than by methanol and acetone (40.12 and 86.91 mg/g). The polarity of solvents also affected FAMEs composition of microalgal lipids. Total saturated fatty acids and unsaturated fatty acids of extracted lipids were 61.53% and 38.47% by chloroform and 38.85% and 61.15% by methanol. Moreover, polar and non-polar solvents affected the biodiesel properties such as cetane number and oxidative stability. In addition, higher ratio of chloroform to methanol and higher temperature increased the lipid yield and saturation degree of lipids, through ultrasound-assisted lipid extraction method. Overall, the results revealed that the lipids yield, FAMEs composition, and biodiesel quality of microalgal biomass can be significantly affected by solvents polarity and extraction conditions.