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Getting over recalcitrance of lignocellulose is effective way to fuel production from lignocellulosic biomass. In current work, different pretreatments were applied to enhance the digestibility of corn stover (CS). Results showed that steam explosion (SE)-treated CS produced maximal methane yield (223.2 mL/g vs ) at 1.2 MPa for 10 min, which was 55.2% more than untreated (143.8 mL/g vs ). Whereas 1.5% KOH-treated CS produced maximum methane yield of 208.6 mL/g vs , and significantly ( α < 0.05) improved 45.1% with respect to untreated. Sequent pretreatment of potassium hydroxide and steam explosion (SPPE) (1.5% KOH-1.2 MPa, 10 min) achieved a very significant ( α < 0.01) improvement (80.0%) of methane yield (258.8 mL/g vs ) compared with untreated CS. Methane production could be well explained by the first-order and modified Gompertz models. Besides, SEM, FTIR, and XRD analyses validated structural changes of CS after SPPE. SPPE might be a promising method to pretreat CS in the future AD industry. [ABSTRACT FROM AUTHOR]

Highlights: [•] Co-digestion of CM and CS were investigated under batch and continuous conditions. [•] CSTR showed stable methane yield of 223±7mL/gVSadded at OLR of 4gVS/L/d. [•] Post-digestion of digestate gave extra energy yield up to 2.6MJ/kgVSadded. [•] Pyrolysis of digestate could produce valuable pyrolysis gas with LCV of 10.9MJ/m3. [ABSTRACT FROM AUTHOR]

Highlights: [•] Methane production potential, BD, and kinetics of various substrates were compared. [•] Both of elemental and organic analysis could be used to calculate the TMY and BD. [•] 15% VS of lignin was a critical point in AD of lignocellulosic and manure wastes. [ABSTRACT FROM AUTHOR]

Highlights: [•] Synergistic effects were found in CS:CM ratios of 3:1 and 1:1. [•] In W-AD and HSS-AD, highest methane yields were obtained at CS:CM ratio of 3:1. [•] Highest volumetric productivity of 14.2L/L was found in SS-AD at CS:CM of 1:1. [•] VFA/TA value of 0.4 was a more important criterion than NH3-N or FA concentration. [ABSTRACT FROM AUTHOR]

Abstract: This research was conducted to develop an integrated rotary drum reactor (RDR)-anaerobic-phased solids (APS) digester system for the treatment of municipal solid waste (MSW) to produce biogas energy and achieve waste reduction. A commercial RDR facility was used to provide a 3-d pretreatment and sufficient separation of the organics from MSW and then the organics were digested in a laboratory APS-digester system for biogas production. The organics generated from the RDR contained 50% total solids (TS) and 36% volatile solids (VS) on wet basis. The APS-digester was started at an organic loading rate (OLR) of 3.1gVSL−1 d−1 and operated at three higher OLRs of 4.6, 7.7 and 9.2gVSL−1 d−1. At the OLR of 9.2gVSL−1 d−1 the system biogas production rate was 3.5LL−1 d−1 and the biogas and methane yields were 0.38 and 0.19LgVS−1, respectively. Anaerobic digestion resulted in 38% TS reduction and 53% VS reduction in the organic solids. It was found that the total VFA concentration reached a peak value of 15,000mgL−1 as acetic acid in the first 3d of batch digestion and later decreased to about 500mgL−1. The APS-digester system remained stable at each OLRs for over 100d with the pH in the hydrolysis reactors in the range of 7.3–7.8 and the pH in the biogasification reactor in 7.9–8.1. The residual solids after the digestion had a high heating value of 14.7kJgTS−1. [Copyright &y& Elsevier]

Abstract: The effect of manure-screening on the biogas yield of dairy manure was evaluated in batch digesters under mesophilic conditions (35°C). Moreover, the study determined the biogas production potential of different mixtures of unscreened dairy manure and food waste and compared them with the yield from manure or food waste alone. A first-order kinetics model was developed to calculate the methane yield from different mixtures of food waste and unscreened dairy manure. The methane yields of fine and coarse fractions of screened manure and unscreened manure after 30days were 302, 228, and 241L/kgVS, respectively. Approximately 93%, 87%, and 90% of the biogas yields could be obtained, respectively, after 20days of digestion. Average methane content of the biogas was 69%, 57%, and 66%, respectively. Based on mass balance calculations, separation of the coarse fraction of manure would sacrifice about 32% of the energy potential. The methane yield of the food waste was 353L/kgVS after 30days of digestion. Two mixtures of unscreened manure and food waste, 68/32% and 52/48%, produced methane yields of 282 and 311L/kgVS, respectively after 30days of digestion. After 20days, approximately 90% and 95% of the final biogas yield could be obtained, respectively. Therefore, a hydraulic retention time (HRT) of 20days could be recommended for a continuous digester. The average methane content was 62% and 59% for the first and second mixtures, respectively. The predicted results from the model showed that adding the food waste into a manure digester at levels up to 60% of the initial volatile solids significantly increased the methane yield for 20days of digestion. [Copyright &y& Elsevier]

Abstract: Biogas and methane yields of food and green wastes and their mixture were determined using batch anaerobic digesters at mesophilic (35±2°C) and thermophilic (50±2°C) temperatures. The mixture was composed of 50% food waste and 50% green waste, based on the volatile solids (VS) initially added to the reactors. The thermophilic digestion tests were performed with four different feed to inoculum (F/I) ratios (i.e., 1.6, 3.1, 4.0 and 5.0) and the mesophilic digestion was conducted at one F/I (3.1). The results showed that the F/I significantly affected the biogas production rate. At four F/Is tested, after 25days of thermophilic digestion, the biogas yield was determined to be 778, 742, 784 and 396mL/g VS for food waste, respectively; 631, 529, 524 and 407mL/g VS for green waste, respectively; and 716, 613, 671 and 555mL/g VS for the mixture, respectively. About 80% of the biogas production was obtained during the first 10days of digestion. At the F/I of 3.1, the biogas and methane yields from mesophilic digestion of food waste, green waste and their mixture were lower than the yields obtained at thermophilic temperature. The biogas yields were 430, 372 and 358mL/g VS, respectively, and the methane yields were 245, 206, and 185mL/g VS, respectively. [Copyright &y& Elsevier]

Abstract: The effects of the addition of enzyme products containing cellulase, hemicellulase, and β-glucosidase to anaerobic digestion systems were studied using Jose Tall Wheat Grass (wheat grass) as a model substrate. Anaerobic digestion tests were performed using batch reactors operated at 50°C. The application of enzyme products in three digestion configurations were simulated and investigated: (1) enzyme addition to a single-stage digester, (2) pre-treatment of wheat grass with enzymes followed by a single-stage anaerobic digestion, and (3) enzyme addition to the first stage (hydrolysis and acidification) of a two-stage digestion system. The enzyme products showed positive effects on the solubilization of wheat grass when used alone to treat the wheat grass. However, no significant differences in biogas and methane yields, and volatile solids reduction resulted when the enzyme products were tested in the anaerobic digestion systems. This reveals that the microorganisms present in the inoculum were effective in carrying out the digestion of wheat grass. The types of microorganisms present in the inoculum were identified using 16S rRNA sequence analysis. A comparison of the sequences between the different inocula revealed that the prevalent operational taxonomic units were similar, but that the acidified inoculum contained a higher percentage of the species Thermotogae. [Copyright &y& Elsevier]

Abstract: The co-digestion of onion juice and aerobic wastewater sludge produced from an onion processor using an anaerobic mixed biofilm reactor (AMBR) was investigated for biogas energy production potential and waste treatment. Two experiments were conducted to study the performance of an AMBR at different organic loading rates (OLRs) using different mixtures of onion juice and aerobic sludge. In the first experiment, the OLR was increased from 1.24 to 4.37gVS/L/d by increasing the amount of onion juice in the feed mixture while maintaining a constant amount of aerobic sludge. When the OLR reached 4.37gVS/L/d, the AMBR failed as indicated by decreased biogas production and pH. Increase of carbon to nitrogen ratio (C/N) from 13.7 to 20.3 and lack of proper alkalinity were suspected to be the causes for the failure. In the second experiment, the C/N of the feed mixture was maintained at about 15 while the OLR was increased from 1.40 to 3.60gVS/L/d. The digester showed stable performance. The average biogas and methane yields of the two experiments were 0.62±0.05L/gVS and 0.37±0.08L/gVS, respectively. It was concluded that the C/N of about 15 was recommended for treating the mixture of onion juice and aerobic sludge. [Copyright &y& Elsevier]

Abstract: The aim of this work was to investigate the effects of aeration rate, aeration method, moisture content, and manure age on the characteristics of dairy manure composting with rice straw in terms of composting temperature, oxygen consumption rate, emission of odorous gases, and final compost property. It was found that the aeration rate of 0.25L/min-kg VS was capable of achieving the highest composting temperature, longest retention time of high temperature, and less emission of odor gases. Except for the composting temperature reached, there was no significant difference between bottom-forced and top-diffusion aerations in terms of final compost property. The higher initial moisture content (65%) was more favorable for its higher temperature, longer retention time of high temperature, and more stable end compost obtained. Fresh manure showed better composting performance than the aged manure for its higher temperature reached in less time and less ammonia emission. Oxygen consumption rates were basically similar to those of temperatures. Most emissions of the odorous gases occurred during the first week of composting, therefore, special attention should be paid to this period of time for effective odor control. [Copyright &y& Elsevier]

Abstract: Food waste collected in the City of San Francisco, California, was characterized for its potential for use as a feedstock for anaerobic digestion processes. The daily and weekly variations of food waste composition over a two-month period were measured. The anaerobic digestibility and biogas and methane yields of the food waste were evaluated using batch anaerobic digestion tests performed at 50°C. The daily average moisture content (MC) and the ratio of volatile solids to total solids (VS/TS) determined from a week-long sampling were 70% and 83%, respectively, while the weekly average MC and VS/TS were 74% and 87%, respectively. The nutrient content analysis showed that the food waste contained well balanced nutrients for anaerobic microorganisms. The methane yield was determined to be 348 and 435mL/gVS, respectively, after 10 and 28 days of digestion. The average methane content of biogas was 73%. The average VS destruction was 81% at the end of the 28-day digestion test. The results of this study indicate that the food waste is a highly desirable substrate for anaerobic digesters with regards to its high biodegradability and methane yield. [Copyright &y& Elsevier]

Cultivation of the oyster mushroom, Pleurotus sajor-caju, on rice and wheat straw without nutrient supplementation was investigated. The effects of straw size reduction method and particle size, spawn inoculation level, and type of substrate (rice straw versus wheat straw) on mushroom yield, biological efficiency, bioconversion efficiency, and substrate degradation were determined. Two size reduction methods, grinding and chopping, were compared. The ground straw yielded higher mushroom growth rate and yield than the chopped straw. The growth cycles of mushrooms with the ground substrate were five days shorter than with the chopped straw for a similar particle size. However, it was found that when the straw was ground into particles that were too small, the mushroom yield decreased. With the three spawn levels tested (12%, 16% and 18%), the 12% level resulted in significantly lower mushroom yield than the other two levels. Comparing rice straw with wheat straw, rice straw yielded about 10% more mushrooms than wheat straw under the same cultivation conditions. The dry matter loss of the substrate after mushroom growth varied from 30.1% to 44.3%. The straw fiber remaining after fungal utilization was not as degradable as the original straw fiber, indicating that the fungal fermentation did not improve the feed value of the straw. [Copyright &y& Elsevier]

Anaerobic digestion (AD) of vinegar residue was investigated in continuously stirred tank reactor (CSTR). The influence of organic loading rate (OLR) and effluent recirculation on AD performance of vinegar residue was tested. Five OLRs, 1.0, 1.5, 2.0, 2.5, and 3.0 g vs L −1 d −1 , were used. The highest volumetric methane productivity of 581.88 mL L −1 was achieved at OLR of 2.5 g vs L −1 d −1 . Effluent reflux ratio was set as 50%, the results showed that effluent recirculation could effectively neutralize the acidity of vinegar residue, raise the pH of the feedstock, and enhance the buffering capacity of the AD system. Anaerobic digestion of vinegar residue could be a promising way not only for converting this waste into gas energy but also alleviating environmental pollution which might be useful for future industrial application. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this research was to develop an integrated process to produce biogas and high-quality particleboard using saline creeping wild ryegrass (CWR), Leymus triticoides through anaerobic digestion (AD). Besides producing biogas, AD also serves as a pretreatment method to remove the wax layer of CWR for improving binding capability and then the residue is used to produce high-quality particleboard. CWR was digested for three time periods, 15, 22, and 33 days with the volatile solid (VS) loading of 10g-VS/L-sludge and the food to microorganism (F/M) ratio of 1.41. The highest biogas yield after digestion for 33 days was 251mL/g-VS, which is corresponded to energy of 8419BTU/kg-dry CWR. The highest methane content of biogas was 63%. Compared with particleboards manufactured from urea formaldehyde (UF) and untreated CWR, the mechanical and long-term (24h) water resistance properties of particleboards made from UF and 33-day AD CWR residue were statistically significantly improved, except for modulus of elasticity (MOE). For example, the modulus of rupture (MOR) was increased by 39%. The results indicated that the integrated process could be a cost-effective and environmentally friendly method for producing bioenergy and particleboard with agricultural residues. [Copyright &y& Elsevier]

This study was conducted to determine the characteristics and biogas production potential of organic materials separated from municipal solid wastes using a rotary drum reactor (RDR) process. Four different types of wastes were first pretreated with a commercial RDR system at different retention times (1, 2 and 3 d) and the organic fractions were tested with batch anaerobic digesters with 2.6gVSL−1 initial loading. The four types of waste were: municipal solid waste (MSW), a mixture of MSW and paper waste, a mixture of MSW and biosolids, and a mixture of paper and biosolids. After 20 d of thermophilic digestion (50±1°C), it was found that the biogas yields of the above materials were in the range of 457–557mLgVS−1 and the biogas contained 57.3–60.6% methane. The total solid and volatile solid reductions ranged from 50.2% to 65.0% and 51.8% to 66.8%, respectively. For each material, the change of retention time in the RDR from 1 to 3d did not show significant (α =0.05) influence on the biogas yields of the recovered organic materials. Further studies are needed to determine the minimum retention time requirements in the RDR system to achieve effective separation of organic from inorganic materials and produce suitable feedstock for anaerobic digesters. [Copyright &y& Elsevier]

Abstract: The objective of this research was to characterize the qualities (mechanical properties and water resistance) of particleboard made from saline Jose Tall Wheatgrass (JTW), Agropyron elongatum. For the JTW particleboards made with 4% polymeric methane diphenyl diisocyanate (PMDI), the mechanical properties and water resistance improved with the increase of particleboard density from 0.71 to 0.75g/cm3. The particleboards with density of 0.74g/cm3 had similar mechanical properties of wood-based particleboards, except for lower internal bond strength. Among the particleboards made with particles of different initial moisture contents from 2% to 10%, the particleboard with the particles of 8% initial moisture content had the highest qualities. The pretreatment using NaOH solution to wash the JTW particles reduced the qualities of finished particleboards bonded with both PMDI and urea formaldehyde (UF) resins. Particleboards made with PMDI showed superior qualities than those made with UF, as shown by the measured contact angle results between the adhesives and JTW. [Copyright &y& Elsevier]

Highlights • Swine slaughterhouse waste produced a maximum methane yield of 999.2 mL/g VS. • Lipid hydrolysis led to serious accumulation of linoleic, oleic and palmitic acids. • Increase of palmitic acid produced by degradation of oleic acid was observed. • Predominant microorganisms were Clostridium , Syntrophomonas and Methanospirillum. Abstract This study investigated methane production, long-chain fatty acids (LCFAs) profile, and predominant microorganisms in anaerobic digestion (AD) of lipid-rich swine slaughterhouse waste (SSW). The maximum methane yield was 999.2 mL/g VS. LCFAs, as inhibitory hydrolysis products, accumulated first to 1165 mg/L on day 3, and then decreased sharply to 125.7 mg/L on day 9, and finally were degraded to 20 mg/L on day 27. Linoleic acid (C18:2), oleic acid (C18:1) and palmitic acid (C16:0) were the dominant LCFAs. The easy conversion of C18:1 to C16:0 compared with difficult degradation of C16:0 resulted in an increase of C16:0 on day 4–6. Predominant microorganisms were Clostridium , Syntrophomonas and Methanospirillum. This study proved the high methane potential of lipid-rich SSW and gained insights into the degradation process by analysis of intermediates of LCFAs and predominant microorganisms. The results can provide valuable guidance for efficient utilization of this waste to produce methane in future. [ABSTRACT FROM AUTHOR]

This study systematically investigated the anaerobic digestibility of durian shell and focused on maximizing the methane yield using response surface methodology. Results showed in the feedstock to inoculum (F/I) ratio range of 0.2–2, a lower value was preferred. Meanwhile the methane yield showed a sharp rise first followed by a decline as the organic loading (OL) increased from 3 to 27 g VS/L. The highest experimental methane yield (EMY) was calculated to be 170.6 ml/g VS at F/I ratio of 0.2 and organic loading of 20.45 g VS/L. To make the combination of F/I ratio and OL more practical, 0.5 was set as the optimum F/I ratio, when the highest EMY was obtained to be 165.0 ml/g VS at the OL of 20.45 g VS/L. Characteristics of final effluent implied the anaerobic system was stable. This study is important to promote the application of durian shell into anaerobic digestion from theory to practice. [ABSTRACT FROM AUTHOR]

The pretreatment of wheat straw with potassium hydroxide (KOH) at ambient temperature (20 °C) was investigated. The pretreatment effects on chemical composition and physical structures, and subsequent enzymatic hydrolysis and anaerobic digestion were evaluated. Wheat straw at 10% total solids (TS) was treated with KOH solution for 24 h at a wide range of KOH loadings from 2% to 50% (w/w dry basis). Higher KOH loading resulted in higher lignin reduction from the straw and chemical oxygen demand (COD) in the resulting black liquor. Maximum lignin reduction of 54.7% was observed at 50% KOH loading. In comparison to untreated straw, specific hydrolysis yields achieved 14.0–92.3% over the range of 2–50% KOH loading, and methane yields increased 16.7–77.5% for KOH loadings of 10–50%, respectively. Accounting for losses during pretreatment, 20% KOH loading resulted in maximum overall reducing sugar yield and methane yield and therefore is the recommended loading for pretreatment under these conditions. [ABSTRACT FROM AUTHOR]

Highlights: [•] Thermogravimetric analysis (TGA) of ionic liquid (IL) pretreated biomass performed. [•] Insight into the IL pretreatment revealed by TGA discussed. [•] Cleavage of side chains and degradation of backbone of xylan detected. [Copyright &y& Elsevier]

Highlights: [•] Interaction of biomass with ionic liquid (IL) pretreatment studied by XRD. [•] Swelling and dissolution of cellulose control the resultant crystalline structure. [•] Proper manipulation of IL’s swelling ability leds to low-order structures. [ABSTRACT FROM AUTHOR]

Abstract: Ensiling was investigated for the long-term storage of Sugar Beet Pulp (SBP). Eight strains of lactic acid bacteria (LAB) and a non-inoculated control were screened based on their ability to rapidly reduce pH, produce a large amount of lactic acid and inhibit undesirable fermentations. Lactobacillus brevis B-1836 (LAB #120), Lactobacillus fermentum NRRL B-4524 (LAB #137) and a non-inoculated control were selected for further research to determine the effects of LAB inoculation level and packing density on SBP silage quality and sugar yield upon enzymatic hydrolysis. Both SBP preservation and prevention of cellulose and hemicellulose loss were better when SBP was treated with LAB #137 compared to LAB #120 and the non-inoculated control. Additionally, the ensiling process was found to significantly improve the enzymatic digestibility of SBP by as much as 35%. The results suggest that ensiling may be a promising technology for SBP stabilization and pretreatment for bioconversion to products. [ABSTRACT FROM AUTHOR]

Abstract: Leaching was studied for its application in extracting inorganic and organic constituents from fresh fermented grape pomace, air-dried fermented grape pomace and air-dried sugar beet pulp. Samples of each feedstock were leached in water at ambient temperature for 30 or 120min at dry solid-to-liquid ratios of 1/20 and 1/50kg/L. Leaching removed 82% of sodium, 86% of potassium, and 76% of chlorine from sugar beet pulp, and reduced total ash concentration in air-dry fermented grape pomace from 8.2% to 2.9% of dry matter, 8.2% to 4.4% in fresh fermented grape pomace, and 12.5% to 5.4% in sugar beet pulp. Glycerol (7–11mg/dry g), ethanol (131–158mg/dry g), and acetic acid (24–31mg/dry g) were also extracted from fermented grape pomace. These results indicate that leaching is a beneficial pretreatment step for improving the quality of food processing residues for thermochemical and biochemical conversion. [Copyright &y& Elsevier]

• The OL and F/I ratio of tobacco stalks for AD were optimized via RSM. • Various pretreatments for improving methane yield from TS 116 were examined. • AHP pretreated TS 116 achieved the highest methane yield. This work firstly investigated the suitable organic loading (OL) and feed to inoculum (F/I) ratio of three kinds of tobacco stalks (TS 116 , TS 99 , and TS 85) during anaerobic digestion (AD) via response surface methodology (RSM). The highest experimental methane yield (EMY) of 148.1 mL/g VS was achieved from TS 116 at OL of 20.2 g VS/L and F/I ratio of 1.1. To further increase EMY, various pretreatments including alkaline hydrogen peroxide (AHP), NaOH, KOH, Ca(OH) 2 , HCl, and oxalic acid (H 2 C 2 O 4) were implemented on TS 116. Results showed that AHP was most effective, and the maximal EMY of 350.7 mL/g VS and biodegradability (B d) of 81.4% were obtained from 7% AHP pretreated TS 116 , which increased by 105.6% than untreated. XRD, FTIR, and SEM analyses evidenced that the structure of AHP pretreated TS 116 was strongly disrupted. This study lays the foundation for applying this waste into AD in future applications. [ABSTRACT FROM AUTHOR]