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The organic loading rate (OLR) is an essential parameter that controls the anaerobic digestion process. This work investigated the performance of immersed membrane bioreactors operated at high OLRs of 4, 6, 8 and 10 g volatile solids (VS)/L/d regarding the fermentation behavior, product recovery and microbial dynamics during the acidogenic fermentation of food waste to volatile fatty acids (VFAs) and hydrogen. The highest yield of 0.52 g VFA/gVSadded was attained at 6 g VS/L/d, while an optimal hydrogen yield of 14.7 NmL/gVSadded was obtained at 8 g VS/L/d. The bacterial populations, analyzed using 16S rRNA gene amplicon sequencing, consisted mainly of Firmicutes and Actinobacteria at OLRs 4 and 8 g VS/L/d while Firmicutes, Actinobacteria and Proteobacteria phyla dominated at 6 and 10 g VS/L/d. Moreover, the presence of Clostridium and Lactobacillus genera correlated with the acetate, butyrate, caproate and lactate production.

Agricultural residues are constantly increasing with increased farming processes, and improper disposal is detrimental to the environment. Majority of these waste residues are rich in lignocellulose, which makes them suitable substrate for bacterial fermentation in the production of value-added products. In this study, bacterial cellulose (BC), a purer and better form of cellulose, was produced by two

Effects of antimicrobial compounds on dry anaerobic digestion (dry-AD) processes were investigated. Four compounds with known inhibition effects on traditional wet digestion, i.e. car-3-ene, hexanal, 1-octanol and phenol were selected and investigated at concentrations of 0.005%, 0.05% and 0.5%. Food waste (FW) and Paper waste (PW) were used as model substrates, all assays were running with the substrate to inoculum ratio of 1:1 (VS basis) corresponding to 15% TS in reactors. Generally, increasing concentrations of inhibitors resulted in decreasing methane yields with a few exceptions; in all these specific cases, long, lag phase periods (60 days) were observed. These adaptation periods made possible for the microbial systems to acclimatize to otherwise not preferred conditions leading to higher methane yields. Comparing the effects of the four different groups, phenols had the highest inhibitory effects, with no methane production at the highest amount added, while the lowest effects were obtained in cases of car-3-ene. Furthermore, the results showed that adding inhibitors up to a certain concentrations can repair the balance in AD process, slowing down the degradation steps, hence making it possible for the methanogens to produce a higher amount of methane. This phenomenon was not observed in case of PW, which is already a slow degradable substrate in its nature.

The majority of municipal Wastewater Treatment Plants (WWTPs) in Sweden produce biogas from sewage sludge. In order to increase the methane production, co-digestion of internal sludge with Organic Fraction of Municipal Solid Waste (OFMSW) might be feasible in the future. The objective of this study was therefore to find a beneficial solution for the utilization of OFMSW at the WWTP in Varberg, Sweden. The effects of co-digesting primary sludge (PS) and OFMSW collected in the municipality, in different mixing ratios, were investigated by semi-continuous anaerobic digestion assays. Furthermore, the effects of the addition of a commercial trace elements mixture solution (CTES), available on the market in Sweden, were also examined. Co-digestion of OFMSW and PS resulted in specific methane yields of 404, 392, and 375 Nml CH4/g volatile solids (VS), obtained during semi-continuous operations of 301, 357 and 385 days, for the reactors fed with OMFSW:PS ratio of 4:1, 3:1, and 1:1, and at maximum organic loading rates (OLRs) achieved of 4.0, 4.0 and 5.0 gVS/L/d, respectively. Furthermore, mono-digestion of OFMSW failed already at OLR of 1.0 gVS/L/d, however, an OLR of 4.0 gVS/L/d could be achieved with addition of 14 &micro, L/g VS Commercial Trace Element Solutions (CTES) leading to 363 mL CH4/g VS methane production. These experiments were running during 411 days. Hence, higher process efficiency was obtained when using co-digestion of OFMSW and PS compared to that of OFMSW in mono-digestion. Co-digestion is a more feasible option where a balanced Carbon/Nitrogen (C/N) ratio and nutrient supply can be maintained.

Effluent of biogas digestate, a waste stream with serious environmental problems, was used to pretreat rice straw in order to improve biofuel production. To investigate the effect of components presented in this waste stream and compare the results, water was also applied at the same conditions for the pretreatment. The straw was pretreated at 130, 160, and 190 °C for 30 and 60 min and subjected to enzymatic hydrolysis, simultaneous saccharification and fermentation (SSF), liquid anaerobic digestion (L-AD), and dry anaerobic digestion (D-AD). The highest improvements in hydrolysis and ethanol yield were 100 and 125%, achieved from the straw pretreated with effluent of biogas digestate at 190 °C for 60 min. The best methane yield was obtained through L-AD and D-AD of straw pretreated at 190 °C and 30 min with effluent of biogas digestate, resulting in 24 and 26% enhancements in produced methane. However, treatment with water had no significant effect on methane yield. Compositional and FTIR analyses indicated hemicellulose omission through the treatment under severe conditions. Furthermore, SEM images showed major enhancement in straw porosity by the pretreatment.

Anaerobic digestion (AD) of the organic fraction of municipal solid waste (OFMSW), leading to renewable energy production in the form of methane, is a preferable method for dealing with the increasing amount of waste. Food waste is separated at the source in many countries for anaerobic digestion. However, the presence of plastic bags is a major challenge for such processes. This study investigated the anaerobic degradability of different bioplastics, aiming at potential use as collecting bags for the OFMSW. The chemical composition of the bioplastics and the microbial community structure in the AD process affected the biodegradation of the bioplastics. Some biopolymers can be degraded at hydraulic retention times usually applied at the biogas plants, such as poly(hydroxyalkanoate)s, starch, cellulose and pectin, so no possible contamination would occur. In the future, updated standardization of collecting bags for the OFMSW will be required to meet the requirements of effective operation of a biogas plant.

Dry anaerobic co-digestion of citrus wastes (CW) with chicken feather (CF), wheat straw (WS) and manure bedded with straw (MS) was investigated in batch and continuous processes. Experiments were designed with different mixing ratios considering the inhibitory effect of CW, C/N ratio, and total solid content of individual feedstocks. Best mixing ratio (CF:CW:WS:MS) of 1:1:6:0, enhanced methane yield by 14% compared to the expected yield calculated according to the methane yields obtained from the individual fractions. The process performance of this mixture was then investigated in continuous plug flow reactors at different organic loading rates (OLR) with feedstock total solid contents of 21% TS (RTS21) and 32% TS (RTS32). At OLR of 2 gVS/L/d, a methane yield of 362 NmlCH4/gVSadded was obtained from RTS21, which is 13.5% higher than the yield obtained from RTS32 (319 NmlCH4/gVSadded). However, it was not possible to achieve a stable process when the OLR was further increased to 3.8 gVS/L/d; there were increased total VFAs concentrations and a decline in the biogas production.

The use of consecutive feeding was applied to investigate the response of the microbial biomass to a second addition of substrates in terms of biodegradation using batch tests as a promising alternative to predict the behavior of the process. Anaerobic digestion (AD) of the slaughterhouse waste (SB) and its co-digestion with manure (M), various crops (VC), and municipal solid waste were evaluated. The results were then correlated to previous findings obtained by the authors for similar mixtures in batch and semi-continuous operation modes. AD of the SB failed showing total inhibition after a second feeding. Co-digestion of the SB+M showed a significant improvement for all of the response variables investigated after the second feeding, while co-digestion of the SB+VC resulted in a decline in all of these response variables. Similar patterns were previously detected, during both the batch and the semi-continuous modes.

Anaerobic mono- and co-digestion of two municipal sludge wastes (A and C), grease trap waste (B), and meat processing waste (D) were investigated under mesophilic temperature conditions by biochemical methane potential (BMP) assays and kinetic modeling. Wastes ratios in the mixtures were systematically selected based on Simplex Lattice mixture design, and statistical analyses were performed to elucidate possible synergetic and antagonistic effects of wastes interactions on the kinetics and ultimate methane potentials of wastes co-digestion. The mixture of 1/8A + 1/8B + 1/8C + 5/8D (VS basis) showed the highest COD and VS removals of 35.0% and 33.8%, respectively. Substrates B and D with 980 and 641 mL/g-VS methane yields, respectively, had the highest BMP. However, with reaction rate constants of 0.047 and 0.070 d−1, their methane production was very slow. It was observed that diluting these organic-rich but complex substrates with readily soluble wastes (A and C) enhanced their biogas production rate markedly. Statistical analysis showed that the interactions among the substrates in co-digestion did not have a significant impact on the ultimate cumulative methane yields. Nevertheless, these interactions proved to have synergic and antagonistic effects on the reaction rates, leading to accelerated or hindered methane production rates. As a result, while the methane yield of wastes co-digestion could be predicted by proportional summation of methane yields obtained in mono-digestions of these waste fractions, such linear regressions were unable to provide a good estimation of the rate constants. Quadratic equations, however, were found to estimate the rate constants of the co-digestion process with good accuracy.

The use of liquid fraction of biogas digestate (LFBD) instead of fresh water (hydrothermal) for the pretreatment of wheat straw was evaluated to improve the yield of released sugars during the following hydrolysis step. The pretreatments were conducted at temperatures of 130, 160, and 190 °C for 30 and 60 min. In most of the cases, pretreatment using LFBD led to higher glucose yields and higher total sugars concentrations, compared to those obtained after applying hydrothermal pretreatments. The increase of temperature resulted in an increase in sugars during the enzymatic hydrolysis. The highest yields of glucose (about 59%) were observed after treatments at 190 °C for 60 min, independently of which type of pretreatment was applied and at 190 °C for 30 min using LFBD. Treatment, with LFBD at 190 °C and for 60 min, resulted in glucose and xylose concentrations of 7.36 g L

Biogas or biomethane is traditionally produced via anaerobic digestion, or recently by thermochemical or a combination of thermochemical and biological processes via syngas (CO and H2) fermentation. However, many of the feedstocks have recalcitrant structure and are difficult to digest (e.g., lignocelluloses or keratins), or they have toxic compounds (such as fruit flavors or high ammonia content), or not digestible at all (e.g., plastics). To overcome these challenges, innovative strategies for enhanced and economically favorable biogas production were proposed in this review. The strategies considered are commonly known physical pretreatment, rapid decompression, autohydrolysis, acid- or alkali pretreatments, solvents (e.g. for lignin or cellulose) pretreatments or leaching, supercritical, oxidative or biological pretreatments, as well as combined gasification and fermentation, integrated biogas production and pretreatment, innovative biogas digester design, co-digestion, and bio-augmentation.

Safflower straw, an agricultural lignocellulosic waste, was used for biogas and bioethanol production. Prior to bioconversion, the straw was pretreated with 0.5 and 1 mol/L sodium carbonate (Na2CO3) at 120, 150, and 180 °C for 1–5 h, resulting in a liquid fraction containing hemicellulosic sugars and a solid fraction mainly containing cellulose. Two scenarios were followed: (I) subjecting both solid and liquid fractions to biogas production and (II) subjecting the solid fraction to bioethanol production and the liquid fraction to biogas production. The highest yield of glucose was 91.4%, achieved after pretreatment at 180 °C with 0.5 mol/L Na2CO3 for 5 h, as compared to that of 22.1% for the untreated substrate. The ethanol yield of untreated straw was 11.1%, and it was improved to 58.1% after alkali pretreatment at 180 °C with 1 mol/L Na2CO3 for 2 h. The highest methane yield obtained was 139.6 N mL/g of volatile solids (VS) after pretreatment at 120 °C with 0.5 mol/L Na2CO3 for 1 h, while that from the ...

Chicken feathers are available in large quantities around the world causing environmental challenges. The feathers are composed of keratin that is a recalcitrant protein and is hard to degrade. In this work, chicken feathers were aerobically pretreated for 2–8 days at total solid concentrations of 5, 10, and 20 % by Bacillus sp. C4, a bacterium that produces both α- and β-keratinases. Then, the liquid fraction (feather hydrolysate) as well as the total broth (liquid and solid fraction of pretreated feathers) was used as substrates for biogas production using anaerobic sludge or bacteria granules as inoculum. The biological pretreatment of feather waste was productive; about 75 % of feather was converted to soluble crude protein after 8 days of degradation at initial feather concentration of 5 %. Bacteria granules performed better during anaerobic digestion of untreated feathers, resulting in approximately two times more methane yield (i.e., 199 mlCH4/gVS compared to 105 mlCH4/gVS when sludge was used). Pretreatment improved methane yield by 292 and 105 % when sludge and granules were used on the hydrolysate. Bacteria granules worked effectively on the total broth, yielded 445 mlCH4/gVS methane, which is 124 % more than that obtained with the same type of inoculum from untreated feather.

Volatile fatty acids (VFAs) are the key intermediates from anaerobic digestion (AD) process that can be a platform to synthesize products of higher value than biogas. However, some obstacles still exist that prevent large-scale production and application of VFAs, key among them being the difficulty in recovering the acids from the fermentation medium and low product yields. In this study, a novel anaerobic immersed membrane bioreactor (iMBR) with robust cleaning capabilities, which incorporated frequent backwashing to withstand the complex AD medium, was designed and applied for production and in situ recovery of VFAs. The iMBR was fed with food waste and operated without pH control, achieving a high yield of 0.54 g VFA/g VSadded. The continuous VFA recovery process was investigated for 40 days at OLRs of 2 gVS/L/d and 4 gVS/L/d without significant change in the permeate flux at a maximum suspended solids concentration of 31 g/L.

Utilisation of wheat straw and wool textile waste in dry anaerobic digestion (AD) process was investigated. Dry-AD of the individual substrates as well as co-digestion of those were evaluated using different total solid (TS) contents ranging between 6 to 30%. Additionally, the effects of the addition of nutrients and cellulose- or protein-degrading enzymes on the performance of the AD process were also investigated. Dry-AD of the wheat straw resulted in methane yields of 0.081 – 0.200 Nm3CH4/kgVS with the lowest and highest values obtained at 30 and 21% TS, respectively. The addition of the cellulolytic enzymes could significantly increase the yield in the reactor containing 13% TS (0.231 Nm3CH4/kg VS). Likewise, degradation of wool textile waste was enhanced significantly at TS of 13% with the addition of the protein-degrading enzyme (0.131 Nm3CH4/kg VS). Furthermore, the co-digestion of these two substrates showed higher methane yields compared with the methane potentials calculated for the individual fractions at all the investigated TS contents due to synergetic effects and better nutritional balance.

The performance of the anaerobic co-digestion process is strongly related to the characteristics of the substrates utilized. In this work, the impact of mixture interactions, i.e., synergy and antagonism, previously observed in batch operation mode were evaluated under semi-continuous co-digestion of slaughterhouse waste (SB) and its different combinations with manure (M), various crops (VC), and municipal solid waste (MSW). The effects on the process performance and the microbial community structure were investigated. The digestion of SB failed at an OLR of 0.9 gVS L-1 d(-1). However, stable performance with higher loadings was observed for mixtures that displayed synergy obtained earlier in the batch mode (i.e., SB + M, SB + VC + MSW). Bacterial and Archaeal groups increased for the SB + M and SB + VC + MSW, compared with the digestion of SB alone and that for SB + VC. The combination that showed antagonistic effects (SB + VC) resulted in unstable operation and poor representation of methanogens. It was proved that synergetic or antagonistic effects observed in batch mode due to the different mixture compositions could be correlated to process performance, as well as the development of the microbial community structure during semi-continuous operation.

Anaerobic digestion is a biochemical process where complex organic matter such as carbohydrates, proteins, and lipids degrade in the absence of oxygen and are converted into methane and carbon dioxide by the action of different groups of microorganisms. It is a sustainable waste management technology, which reduces and stabilizes organic wastes, recycles its nutrient and water content, while producing energy. Biogas reduces the demand for fossil fuels, since it can be used for the production of electric power and heat, or converted into vehicle fuel. Currently, methane production via anaerobic digestion is a steadily increasing industry in Europe and all over the world. This chapter focuses on the anaerobic digestion process and the parameters affecting its performance. It also describes briefly the current technologies for anaerobic digestion. Finally, since the degradation of organic material requires a synchronized action of different groups of microorganisms with different metabolic capabilities, this chapter also presents recent developments in molecular biology techniques as valuable tools to obtain in-depth understanding about this complex microbiological system.

The aim of this work was to study dry anaerobic digestion (dry-AD) of manure bedded with straw using textile-based bioreactor in repeated batches. The 90-L reactor filled with the feedstocks (22-30% total solid) and inoculum without any further treatment, while the biogas produced were collected and analyzed. The digestate residue was also analyzed to check its suitability as bio-fertilizer. Methane yield after acclimatization increased from 183 to 290NmlCH4/gVS, degradation time decreased from 136 to 92days and the digestate composition point to suitable bio-fertilizer. The results then used to carry out economical evaluation, which shows dry-AD in textile bioreactors is a profitable method of handling the waste with maximum payback period of 5years, net present value from $7,000 to $9,800,000 (small to large bioreactors) with internal rate of return from 56.6 to 19.3%.

An effective method for the production of value-added chemicals from food waste and lignocellulosic materials is a hybrid thermal-biological process, which involves gasification of the solid materials to syngas (primarily CO and H2) followed by fermentation. This paper reviews the recent advances in this process. The special focus is on the cultivation methods that involve the use of single strains, defined mixed cultures and undefined mixed cultures for production of carboxylic acids and higher alcohols. A rate limiting step in these processes is the low mass transfer between the gas and the liquid phases. Therefore, novel techniques that can enhance the gas-liquid mass transfer including membrane- and trickle-bed bioreactors were discussed. Such bioreactors have shown promising results in increasing the volumetric mass transfer coefficient (kLa). High gas pressure also influences the mass transfer in certain batch processes, although the presence of impurities in the gas would impede the process.

Integration of wheat straw for a biorefinery-based energy generation process by producing ethanol and biogas together with the production of high-protein fungal biomass (suitable for feed application) was the main focus of the present study. An edible ascomycete fungal strain Neurospora intermedia was used for the ethanol fermentation and subsequent biomass production from dilute phosphoric acid (0.7 to 1.2% w/v) pretreated wheat straw. At optimum pretreatment conditions, an ethanol yield of 84 to 90% of the theoretical maximum, based on glucan content of substrate straw, was observed from fungal fermentation post the enzymatic hydrolysis process. The biogas production from the pretreated straw slurry showed an improved methane yield potential up to 162% increase, as compared to that of the untreated straw. Additional biogas production, using the syrup, a waste stream obtained post the ethanol fermentation, resulted in a combined total energy output of 15.8 MJ/kg wheat straw. Moreover, using thin stillage (a waste stream from the first-generation wheat-based ethanol process) as a co-substrate to the biogas process resulted in an additional increase by about 14 to 27% in the total energy output as compared to using only wheat straw-based substrates.

Different mixture ratios of solid cattle slaughterhouse wastes (SB), manure (M), various crops (VC), and municipal solid wastes (MSW) were investigated for biogas production. The objective was to explore possible significant synergistic effects obtained from the combination of these different substrates. The performance of the process was assessed in thermophilic anaerobic batch co-digestion assays, using a four factor mixture design and methane yield (Y-CH4) and specific methane production rate (r(scH4)) as response variables. The highest methane yield, 655 NmL CH4/g VS was obtained when equal parts (ww) of SB, M, VC, and MSW were combined, while the combination of SB, M, and MSW resulted in the highest specific methane production rate (43 NmL CH4/g VS/d). A mixture design model was fitted to data in order to appraise synergistic and antagonistic interactions. Mixing all four substrates resulted in a 31% increase of the expected yield which was calculated from the methane potential of the individual fractions, clearly demonstrating a synergistic effect due to more balanced nutrient composition enhancing the anaerobic digestion process. However, no significant antagonistic effects were observed. In order to maximize both response variables simultaneously, a response surface method was employed to establish the optimal combination of substrate mixtures. The statistical results and analysis of the biological process gave a coherent picture of the results. (C) 2014 Elsevier B.V. All rights reserved.

The effects of N-methylmorpholine-N-oxide (NMMO) pretreatment on barley straw and forest residues were investigated for biogas production. The pretreatments were performed at 90 degrees C with 85% NMMO for 3-30 h. The best pretreatment conditions resulted in 100% improvement in methane yield during the subsequent digestion compared to that of the untreated lignocelluloses. Methane yields of 0.23 and 0.15 Nm(3) CH4/kg VS were obtained from barley straw and forest residues, respectively, corresponding to 88% and 83% of the theoretical yields. In addition, the effects of the pretreatment with recovered and reused NMMO was also studied over the course of five cycles. Pretreatment with recycled NMMO showed the same performance as the fresh NMMO on barley straw. However, pretreatment of forest residues with recycled NMMO resulted in 55% reduction in methane yield.

Lignocellulosic biomass represents a great potential for biogas production. However, a suitable pretreatment is needed to improve their digestibility. This study investigates the effects of an organic solvent, N-Methylmorpholine-N-oxide (NMMO) at temperatures of 120 and 90 °C, NMMO concentrations of 75 and 85 % and treatment times of 3 and 15 h on the methane yield. The long-term effects of the treatment were determined by a semicontinuous experiment. The best results were obtained using 75 % NMMO at 120 °C for 15 h, resulting in 141 % increase in the methane production. These conditions led to a decrease by 9 % and an increase by 8 % in the lignin and in the carbohydrate content, respectively. During the continuous digestion experiments, a specific biogas production rate of 92 NmL/gVS/day was achieved while the corresponding rate from the untreated sample was 53 NmL/gVS/day. The operation conditions were set at 4.4 gVS/L/day organic loading rate (OLR) and hydraulic retention time (HRT) of 20 days in both cases. NMMO pretreatment has substantially improved the digestibility of forest residues. The present study shows the possibilities of this pretreatment method; however, an economic and technical assessment of its industrial use needs to be performed in the future.

La producción de aceite de la palma Elaeis guineensis aporta residuales orgánicos como los racimos sin frutos (RSF) que representan un 7%. Actualmente los RSF no se aprovechan en su totalidad constituyendo un problema medioambiental. Se estudia el empleo de RSF pretratados con NaOH para la producción de biogás. El tiempo de pretratamiento (TP) de los RSF influye directamente sobre la cantidad de biogás producida logrando conversiones de sólidos volátiles a biogás de 96%, para TP = 60 min y 29 días de reacción. La producción de biogás se ajusta a una ley cinética de orden 1 obteniéndose las constantes cinéticas de la generación de CH4 (0,108 d-1) y CO2 (0,107 d-1) a la temperatura de operación del reactor (55°C). Se presenta un modelo generalizador que permite estimar la conversión de sólidos volátiles a biogás en función del tiempo de pretratamiento y del tiempo de permanencia en el reactor. The production process of oil from Elaeis guineensis palm produces an organic residual. Oil palm empty fruit bunches (OPEFB) are one of the main waste products, representing 7%. Up to now, OPEFB aren't totally used, being an environmental problem. In this paper, the employment of OPEFB pretreated with NaOH is studied as a raw material for biogas production. The pretreatment time (PT) of the OPEFB influences directly on biogas production achieving conversions of volatile solids to biogas of 96% for PT=60 min and 29 days of reaction. Biogas production is adjusted to a first order kinetic law, with kinetic constants for the generation of CH4 (0,108 d-1) and CO2 (0,107 d-1) at the reactor operating temperature (55°C). Finally, a general model is obtained to estimate volatile solids conversion to biogas as a function of pretreatment time and of the residence time inside the reactor.

Economic feasibility of steam explosion pretreatment for improvement of biogas production from wheat straw and paper tube residuals was investigated. The process was simulated by Aspen plus ®, and the economical feasibility of five different plant capacities was studied by Aspen Process Economic Analyzer. Total project investment of a plant using paper tube residuals or wheat straw was 63.9 or 61.8 million Euros, respectively. The manufacturing cost of raw biogas for these two feedstocks was calculated to 0.36 or 0.48 €/m(3) of methane, respectively. Applying steam explosion pretreatment resulted in 13% higher total capital investment while significantly improved the economy of the biogas plant and decreased the manufacturing cost of methane by 36%. The sensitivity analysis showed that 5% improvement in the methane yield and 20% decrease in the raw material price resulted in 5.5% and 8% decrease in the manufacturing cost of methane, respectively.

Methane production from two types of wool textile wastes (TW1 and TW2) was investigated. To improve the digestibility of these textiles, different pretreatments were applied, and comprised thermal treatment (at 120 C for 10 min), enzymatic hydrolysis (using an alkaline endopeptidase at different levels of enzymatic loading, at 55 C for 0, 2, and 8 h), and a combination of these two treatments. Soluble protein concentration and sCOD (soluble chemical oxygen demand) were measured to evaluate the effectivity of the different pretreatment conditions to degrade wool keratin. The sCOD as well as the soluble protein content had increased in both textile samples in comparison to untreated samples, as a response to the different pretreatments indicating breakdown of the wool keratin structure. The combined treatments and the thermal treatments were further evaluated by anaerobic batch digestion assays at 55 C. Combined thermal and enzymatic treatment of TW1 and TW2 resulted in methane productions of 0.43 N m(3)/kg VS and 0.27 N m(3)/kg VS, i.e., 20 and 10 times higher yields, respectively, than that gained from untreated samples. The application of thermal treatment by itself was less effective and resulted in increasing the methane production by 10-fold for TW1 and showing no significant improvement for TW2.

This study investigated the industrial applicationof feather waste as a substrate for anaerobic digestion. Featherwas pretreated with 0–0.2 Ca(OH)2 g/g TSfeather (total solidsof feathers) for 30–120 min at 100–120 C, in order toincrease the digestibility, and to enhance the methane yield ina subsequent digestion at 55 C. Based on the results of thebatch digestion, an industrial process was developed, whichcan achieve 0.40 Nm3/kgVSfeather (volatile solids of feathers)methane yield fromthe pretreated feathers, while it fulfills theanimal by-product hygenization requirements as well. Thisbase case of the industrial pretreatment process was designedusing SuperPro Designer for utilizing 2,500 tons of feathersper year, which is the waste stream from an average slaughterhousewith a capacity of 60,000 broilers per day. Theproduction cost of the methane is estimated to be 0.475 EUR/Nm3, while the investments on the pretreatment unit requires0.97 million EUR as total capital investment, and 0.25 millionEUR/year for operating cost. However, the process issensitive to the plant capacity. Changing the plant capacityfrom 625 to 10,000 tons of feather per year, results inreducing the biogas production cost from 1.177 to0.203 EUR/Nm3. In addition, sensitivity analysis was performedonthe base case to investigate the effect of the value ofthe incoming feather on the overall process profitability. Theresults showed that the proposed investment could be consideredas being financially viable in the case of production of upgraded biomethane even without the current gate feesystem.

The effluent of biogas production plant was used for the pretreatment of rice straw for the improvement of ethanol production. In addition, the organic active ingredients of the effluent, i.e., acetic, butyric, lactic and propionic acids (1–4%), as well as water were employed for the pretreatment at 100 and 140 °C. The results indicated that pretreatment at 100 °C had no significant effect on the performance of subsequent enzymatic hydrolysis and ethanol production by simultaneous saccharification and fermentation (SSF). Among different types of organic acids presented in the effluent, lactic acid showed a better performance. The highest concentration of glucose and ethanol were achieved after 72 h enzymatic hydrolysis and SSF from the straw pretreated at 140 °C with 4% lactic acid. Applying the effluent for the straw pretreatment at 140 °C resulted in an increase in glucose and ethanol concentrations by 42.4 and 47.5%, respectively, compared to those from untreated samples. SEM, FTIR, BET, BJH, and compositional analyses were used to characterize the changes in the structure and composition of rice straw by the pretreatment. Changes in the straw swelling, cellulose crystallinity, pore size distribution, and composition were responsible for the acquired improvements.

This study deals with the utilization of chicken feather waste as a substrate for anaerobic digestion and improving biogas production by degradation of the compact structure of the feather keratin. In order to increase the digestibility of the feather, different pretreatments were investigated, including thermal pretreatment at 120 °C for 10 min, enzymatic hydrolysis with an alkaline endopeptidase [0.53-2.66 mL/g volatile solids (VS) feathers] for 0, 2, or 24 h at 55 °C, as well as a combination of these pretreatments. The effects of the treatments were then evaluated by anaerobic batch digestion assays at 55 °C. The enzymatic pretreatment increased the methane yield to 0.40 Nm(3)/kg VS(added), which is 122 % improvement compared to the yield of the untreated feathers. The other treatment conditions were less effective, increasing the methane yield by 11-50 %. The long-term effects of anaerobic digestion of feathers were examined by co-digestion of the feather with organic fraction of municipal solid waste performed with and without the addition of enzyme. When enzyme was added together with the feed, CH(4) yield of 0.485 Nm(3)/kg VS(-1) d(-1) was achieved together with a stable reactor performance, while in the control reactor, a decrease in methane production, together with accumulation of undegraded feather, was observed.

Pretreatment of OPEFB (oil palm empty fruit bunch) by NMMO (N-methylmorpholine-N-oxide) on its subsequent digestions was investigated. The pretreatments were carried out at 90 and 120 degrees C for 1, 3, and 5 h in three different modes of dissolution (by 85% NMMO solution), ballooning (79% NMMO solution), and swelling (73% NMMO solution). The total solid recovery after the pretreatment was 89-94%. The pretreatment process did not have a major impact on the composition of OPEFB, other than a reduction of ash from 5.4% up to 1.3%. The best improvement in biogas production was achieved by a dissolution mode pretreatment of OPEFB, using conditions of 85% NMMO, 3 h, and 120 degrees C. It resulted in 0.408 Nm(3)/kg VS methane yield and 0.032 Nm(3) CH4/kg VS/day initial methane production rate, which correspond in improving by 48% and 167% compared to the untreated OPEFB, respectively.

In this work, a plug flow reactor was developed for continuous dry digestion processes and its efficiency was investigated using untreated manure bedded with straw at 22% total solids content. This newly developed reactor worked successfully for 230days at increasing organic loading rates of 2.8, 4.2 and 6gVS/L/d and retention times of 60, 40 and 28days, respectively. Organic loading rates up to 4.2gVS/L/d gave a better process stability, with methane yields up to 0.163LCH4/gVSadded/d which is 56% of the theoretical yield. Further increase of organic loading rate to 6gVS/L/d caused process instability with lower volatile solid removal efficiency and cellulose degradation.[on SciFinder (R)] MEDLINE AN 2017659917(Journal; Article; (JOURNAL ARTICLE))

8 Páginas, Production of biogas from different organic materials is a most interesting source of renewable energy. The biomethane potential (BMP) of these materials has to be determined to get insight in design parameters for anaerobic digesters. A workshop was held in June 2015 in Leysin Switzerland to agree on common solutions to the conundrum of inconsistent BMP test results. A discussion covers actions and criteria that are considered compulsory ito accept and validate a BMP test result; and recommendations concerning the inoculum substrate test setup and data analysis and reporting ito obtain test results that can be validated and reproduced., The workshop in Leysin, Switzerland, has been financed by the Swiss Federal Office for Energy, and co-sponsored by Bioprocess Control Sweden AB, Lund, Sweden. The authors thank Alexandra Maria Murray for editing the English.

This study deals with the addition of paper tube residuals to a nitrogen-rich mixture of organic waste obtained from industrial and municipal activities. This nitrogen-rich mixture, called buffer tank substrate (BTS) in the following text, is used in a large-scale biogas plant. The effects were investigated in semi-continuous co-digestion processes, and variations in operational conditions were studied. The addition of paper tubes had stabilizing effects, prevented the failure of the process, and made it possible to decrease the hydraulic retention time from 25 to 20 days. Furthermore, synergetic effects were found, with 15-34% higher methane yields, when paper tubes were co-digested with BTS. Moreover, steam explosion pretreatment of the paper tube waste with the addition of 0-2% NaOH was evaluated by batch digestion experiments. Increasing the NaOH concentrations used in the pretreatment resulted in increasing methane yields, with the highest of 403 N mL of CH4 g(-1) of volatile solids (VS) corresponding to an increase by 50% compared to that when untreated paper was digested (268 N mL of CH4 g(-1) of VS). The long-term effects of this best pretreatment were further investigated by continuous co-digestion experiments, leading to a higher methane yield when pretreated paper tubes were used in the co-digestion process compared to untreated.

Softwood spruce (chips and milled), rice straw and triticale (a hybrid of rye and wheat) straw, were pretreated with N-methylmorpholine-N-oxide (NMMO or NMO) prior to anaerobic digestion to produce biogas. The pretreatments were performed at 130 degrees C for 1-15 h, and the digestions continued for six weeks. The digestions of untreated chips (10 mm) and milled (

Oil palm empty fruit bunches (OPEFB), a waste lignocellulosic material, which is the main byproduct of vegetable oil production industries in Indonesia and Malaysia, was utilized as a source for biogas production. Pretreatments using NaOH as well as phosphoric acid were investigated to improve the biogas production. Clear positive effects of the pretreatments on the yield of methane were observed. The best improvement was achieved when 8% NaOH for 60 min was used for the pretreatment, which resulted in 100% improvement in the yield of methane production. In addition, treatment with phosphoric acid resulted in 40% improvement in the methane yield compared with that of the untreated material. The results showed that the carbohydrate content of OPEFB could be efficiently converted to methane under the anaerobic digestion process. 97% of the theoretical value of methane production was achieved after the pretreatment with NaOH for 60 min. Moreover, the initial rate of methane production was also increased by more than 85% after the treatment with NaOH compared with that of the untreated OPEFB.