Center for the Technology Research and Training on Household Waste in Small Towns and Rural Area

China

Center for the Technology Research and Training on Household Waste in Small Towns and Rural Area

China
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Lu F.,Tongji University | Chai L.,Tongji University | Shao L.,Tongji University | He P.,Tongji University | He P.,Center for the Technology Research and Training on Household Waste in Small Towns and Rural Area
Biotechnology for Biofuels | Year: 2017

Background: Pretreatment is a crucial step for valorization of lignocellulosic biomass into valuable products such as H2, ethanol, acids, and methane. As pretreatment can change several decisive factors concurrently, it is difficult to predict its effectiveness. Furthermore, the effectiveness of pretreatments is usually assessed by enzymatic digestibility or merely according to the yield of the target fermentation products. The present study proposed the concept of "precise pretreatment," distinguished the major decisive factors of lignocellulosic materials by precise pretreatment, and evaluated the complete profile of all fermentation products and by-products. In brief, hemicellulose and lignin were selectively removed from dewaxed rice straw, and the cellulose was further modified to alter the crystalline allomorphs. The subsequent fermentation performance of the selectively pretreated lignocellulose was assessed using the cellulolytic, ethanologenic, and hydrogenetic Clostridium thermocellum through a holistic characterization of the liquid, solid, and gaseous products and residues. Results: The transformation of crystalline cellulose forms from I to II and from I α to I β improved the production of H2 and ethanol by 65 and 29%, respectively. At the same time, the hydrolysis efficiency was merely improved by 10%, revealing that the crystalline forms not only influenced the accessibility of cellulose but also affected the metabolic preferences and flux of the system. The fermentation efficiency was independent of the specific surface area and degree of polymerization. Furthermore, the pretreatments resulted in 43-45% of the carbon in the liquid hydrolysates unexplainable by forming ethanol and acetate products. A tandem pretreatment with peracetic acid and alkali improved ethanol production by 45.5%, but also increased the production of non-ethanolic low-value by-products by 136%, resulting in a huge burden on wastewater treatment requirements. Conclusion: Cellulose allomorphs significantly affected fermentation metabolic pathway, except for hydrolysis efficiency. Furthermore, with the increasing effectiveness of the pretreatment for ethanol production, more non-ethanolic low-value by-products or contaminants were produced, intensifying environmental burden. Therefore, the effectiveness of the pretreatment should not only be determined on the basis of energy auditing and inhibitors generated, but should also be assessed in terms of the environmental benefits of the whole integrated system from a holistic view. © 2017 The Author(s).


Lu F.,Tongji University | Luo C.,Tongji University | Shao L.,Tongji University | Shao L.,Center for the Technology Research and Training on Household Waste in Small Towns and Rural Area | And 2 more authors.
Water Research | Year: 2016

This investigation evaluated the effectiveness of biochar of different particle sizes in alleviating ammonium (NH4+) inhibition (up to 7 g-N/L) during anaerobic digestion of 6 g/L glucose. Compared to the control treatment without biochar addition, treatments that included biochar particles 2-5 mm, 0.5-1 mm and 75-150 μm in size reduced the methanization lag phase by 23.9%, 23.8% and 5.9%, respectively, and increased the maximum methane production rate by 47.1%, 23.5% and 44.1%, respectively. These results confirmed that biochar accelerated the initiation of methanization during anaerobic digestion under double inhibition risk from both ammonium and acids. Furthermore, fine biochar significantly promoted the production of volatile fatty acids (VFAs). Comparative analysis on the archaeal and bacterial diversity at the early and later stages of digestion, and in the suspended, biochar loosely bound, and biochar tightly bound fractions suggested that, in suspended fractions, hydrogenotrophic Methanobacterium was actively resistant to ammonium. However, acetoclastic Methanosaeta can survive at VFAs concentrations up to 60-80 mmol-C/L by improved affinity to conductive biochar, resulting in the accelerated initiation of acetate degradation. Improved methanogenesis was followed by the colonization of the biochar tightly bound fractions by Methanosarcina. The selection of appropriate biochar particles sizes was important in facilitating the initial colonization of microbial cells. © 2015 Elsevier Ltd.


Lin Y.,Tongji University | Lu F.,Tongji University | Shao L.,Center for the Technology Research and Training on Household Waste in Small Towns and Rural Area | He P.,Tongji University
Bioresource Technology | Year: 2013

To investigate the influence of bicarbonate on the metabolic pathway of methanogenesis, different concentrations of bicarbonate (0-0.2mol/L) were applied during thermophilic anaerobic digestion of 2.5 and 5g/L glucose. The stable carbon isotopic results demonstrated that, as the bicarbonate concentration increased, the proportion of total CH4 generated from hydrogenotrophic methanogenesis generally increased. Furthermore, methane production rates and acetate degradation rates were seriously reduced under high levels of bicarbonate (0.15 and 0.2mol/L). Meanwhile, carbon isotope fractionation was more prominent in treatments with 5g/L glucose than that of 2.5g/L glucose. Increased concentrations of bicarbonate altered the dominant methanogens and bacteria and increased the microbial diversity. The inhibitory effects of high concentrations of bicarbonate suggested that bicarbonate should be used cautiously as a buffer salt in anaerobic processes, especially when methanogenetic pathways were studied. © 2013 Elsevier Ltd.


Zheng W.,Tongji University | Phoungthong K.,Tongji University | Lu F.,Tongji University | Shao L.-M.,Tongji University | And 3 more authors.
Waste Management | Year: 2013

We studied the biochemical and anaerobic degradation characteristics of 29 types of materials to evaluate the effects of a physical composition classification method for degradable solid waste on the computation of anaerobic degradation parameters, including the methane yield potential (L0), anaerobic decay rate (k), and carbon sequestration factor (CSF). Biochemical methane potential tests were conducted to determine the anaerobic degradation parameters of each material. The results indicated that the anaerobic degradation parameters of nut waste were quite different from those of other food waste and nut waste was classified separately. Paper was subdivided into two categories according to its lignin content: degradable paper with lignin content of <0.05ggVS-1, and refractory paper with lignin content >0.15ggVS-1. The L0, k, and CSF parameters of leaves, a type of garden waste, were similar to those of grass. This classification method for degradable solid waste may provide a theoretical basis that facilitates the more accurate calculation of anaerobic degradation parameters. © 2013 Elsevier Ltd.


Shao L.-M.,Tongji University | Shao L.-M.,Center for the Technology Research and Training on Household Waste in Small Towns and Rural Area | Zhang C.-Y.,Tongji University | Wu D.,Tongji University | And 4 more authors.
Waste Management | Year: 2014

The effects of rice straw addition level on odorous compounds emissions in a pilot-scale organic fraction of municipal solid waste (OFMSW) composting plant were investigated. The cumulative odorous compounds emissions occurred in a descending order of 40.22, 28.71 and 27.83. mg/dry. kg of OFMSW for piles with rice straw addition level at ratio of 1:10, 2:10 and 3:10 (mixing ratio of rice straw to OFMSW on a wet basis), respectively. The mixing ratio of rice straw to OFMSW had a statistically significant effect on the reduction of malodorous sulfur compounds emissions, which had no statistically significant effect on the reduction of VFAs, alcohols, aldehydes, ketones, aromatics and ammonia emissions during composting, respectively. The cumulative emissions of malodorous sulfur compounds from piles with the increasing rice straw addition level were 1.17, 1.08 and 0.88. mg/dry. kg of OFMSW, respectively. The optimal mixing ratio of rice straw to OFMSW was 1:5. Using this addition level, the cumulative malodorous sulfur compounds emissions based on the organic matter degradation were the lowest during composting of OFMSW. © 2014 Elsevier Ltd.


Zhang J.,Tongji University | Lu F.,Tongji University | Shao L.,Tongji University | Shao L.,Center for the Technology Research and Training on Household Waste in Small Towns and Rural Area | And 2 more authors.
Bioresource Technology | Year: 2014

Wood biochar (6%, 12% and 18% of fresh sludge weight) adding to a sludge-and-straw composting system was investigated to assess the potential of biochar as a composting amendment. Organic degradation efficiency, temporal humification profile of the water-extractable organic fraction and solid organic matter, through spectroscopic, microscopic and elementary analysis were monitored. Fluorescent excitation and emission matrix indicated that concentrations of aqueous fulvic-acid-like and humic-acid-like compounds were, respectively, 13-26% and 15-30% higher in the biochar-amended treatments, than those in the control without biochar-amended. On the first day of sludge aerobic incubation, the presence of biochar resulted in increased oxygen uptake rates of 21-37% due to its higher nano-porosity and surface area. SEM indicated that, in the biochar-amended sludge, the dense microstructure on the sludge surface disintegrated into fragments with organic fraction degraded and water lost. Results indicated that 12-18%. w/w addition of wood biochar to sludge composting was recommended. © 2014 Elsevier Ltd.


Lu F.,Tongji University | Ji J.,Tongji University | Shao L.,Center for the Technology Research and Training on Household Waste in Small Towns and Rural Area | He P.,Tongji University | He P.,Center for the Technology Research and Training on Household Waste in Small Towns and Rural Area
Biotechnology for Biofuels | Year: 2013

Background: The recalcitrant cell walls of microalgae may limit their digestibility for bioenergy production. Considering that cellulose contributes to the cell wall recalcitrance of the microalgae Chlorella vulgaris, this study investigated bioaugmentation with a cellulolytic and hydrogenogenic bacterium, Clostridium thermocellum, at different inoculum ratios as a possible method to improve CH4 and H2 production of microalgae. Results: Methane production was found to increase by 17?∼?24% with the addition of C. thermocellum, as a result of enhanced cell disruption and excess hydrogen production. Furthermore, addition of C. thermocellum enhanced the bacterial diversity and quantities, leading to higher fermentation efficiency. A two-step process of addition of C. thermocellum first and methanogenic sludge subsequently could recover both hydrogen and methane, with a 9.4% increase in bioenergy yield, when compared with the one-step process of simultaneous addition of C. thermocellum and methanogenic sludge. The fluorescence peaks of excitation-emission matrix spectra associated with chlorophyll can serve as biomarkers for algal cell degradation. Conclusions: Bioaugmentation with C. thermocellum improved the degradation of C. vulgaris biomass, producing higher levels of methane and hydrogen. The two-step process, with methanogenic inoculum added after the hydrogen production reached saturation, was found to be an energy-efficiency method for hydrogen and methane production. © 2013 Lü et al.; licensee BioMed Central Ltd.


Lu F.,Tongji University | Li T.,Tongji University | Wang T.,Tongji University | Shao L.,Center for the Technology Research and Training on Household Waste in Small Towns and Rural Area | He P.,Tongji University
Applied Microbiology and Biotechnology | Year: 2014

The sludge digestate stabilized by mesophilic anaerobic digestion was further degraded through thermophilic anaerobic digestion using 0-10 % (v/v) of thermophilic, proteolytic Coprothermobacter proteolyticus, and/or methanogenic granular sludge. The results demonstrated that the temperature shift to thermophilic condition promoted abiotic solubilization of proteins and reactivated the fermentative bacteria and methanogens indigenous in the sludge digestate, resulting in a final methane yield of 6.25 mmol-CH 4/g-volatile suspended solid (VSS) digestate. The addition of C. proteolyticus accelerated the hydrolysis and fermentation of proteins and polysaccharides in the digestate during the early stage of thermophilic anaerobic digestion and stimulated methane production by syntrophic cooperation with methanogenic granular sludge. In the treatment with granular sludge and inoculated with 10 % (v/v) of C. proteolyticus, a final methane yield of 7 mmol-CH4/g-VSS digestate was obtained, and 48.4 % proteins and 27.0 % polysaccharides were degraded. The dissolved proteins were contributed by abiotic factor, C. proteolyticus, and indigenous digestate bacteria, respectively, by around 16, 28, and 56 %. © 2013 Springer-Verlag Berlin Heidelberg.


Shao L.,Center for the Technology Research and Training on Household Waste in Small Towns and Rural Area | Wang T.,Tongji University | Li T.,Tongji University | Lu F.,Tongji University | And 2 more authors.
Bioresource Technology | Year: 2013

Aerobic and anaerobic digestion are popular methods for the treatment of waste activated sludge. However, the differences in degradation of sludge during aerobic and anaerobic digestion remain unclear. In this study, the sludge degradation during aerobic and anaerobic digestion was investigated at mesophilic temperature, focused on protein based on the degradation efficiency and degree of humification. The duration of aerobic and anaerobic digestion was about 90. days. The final degradation efficiency of volatile solid was 66.1. ±. 1.6% and 66.4. ±. 2.4% under aerobic and anaerobic conditions, respectively. The final degradation efficiency of protein was 67.5. ±. 1.4% and 65.1. ±. 2.6% under aerobic and anaerobic conditions, respectively. The degradation models of volatile solids were consistent with those of protein under both aerobic and anaerobic conditions. The solubility of protein under aerobic digestion was greater than that under anaerobic digestion. Moreover, the humification index of dissolved organic matter of aerobic digestion was greater than that during anaerobic digestion. © 2013 Elsevier Ltd.


Wu D.,Tongji University | Zhang C.,Tongji University | Lu F.,Tongji University | Shao L.,Center for the Technology Research and Training on Household Waste in Small Towns and Rural Area | And 2 more authors.
Waste Management | Year: 2014

The application of on-site waste treatment significantly reduces the need for expensive waste collection and transportation in rural areas; hence, it is considered of fundamental importance in developing countries. In this study, the effects of in-field operation of two types of mini-scale on-site solid waste treatment facilities on de-centralized communities, one using mesophilic two-phase anaerobic digestion combined with composting (TPAD, 50. kg/d) and another using decentralized composting (DC, 0.6-2. t/d), were investigated. Source-separated collection was applied to provide organic waste for combined process, in which the amount of waste showed significant seasonal variation. The highest collection amount was 0.18. kg/capital day and 0.6. kg/household day. Both sites showed good performance after operating for more than 6. months, with peak waste reduction rates of 53.5% in TPAD process and 63.2% in DC process. Additionally, the windrow temperature exceeded 55. °C for > 5. days, indicating that the composting products from both facilities were safe. These results were supported by 4. days aerobic static respiration rate tests. The emissions were low enough to avoid any impact on nearby communities (distance <100. m). Partial energy could be recovered by the combined process but with complicated operation. Hence, the choice of process must be considered in case separately. © 2013 Elsevier Ltd.

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