Energy-efficient methane production from macroalgal biomass through chemo disperser liquefaction

A review on current advances in the energy and cost effective pretreatments of algal biomass: Enhancement in liquefaction and biofuel recovery

The main downside of utilizing algal biomass for biofuel production is the rigid cell wall which confines the availability of soluble organics to hydrolytic microbes during biofuel conversion. This constraint reduces the biofuel production efficiency of algal biomass. On the other hand, presenting various pretreatment methods before biofuel production affords cell wall disintegration and enhancement in biofuel generation. The potential of pretreatment methods chiefly relies on the extent of biomass liquefaction, energy, and cost demand. In this review, different pretreatments employed to disintegrate algal biomass were conferred in depth with detailed information on their efficiency in enhancing liquefaction and biofuel yield for pilot-scale implementation. Based on this review, it has been concluded that combinative and phase-separated pretreatments provide virtual input in enhancing the biofuel generation based on liquefaction potential, energy, and cost. Future studies should focus on decrement in cost and energy requirement of pretreatment in depth.

Amelioration of Biogas Production from Waste-Activated Sludge through Surfactant-Coupled Mechanical Disintegration

The current study intended to improve the disintegration potential of paper mill sludge through alkyl polyglycoside-coupled disperser disintegration. The sludge biomass was fed to the disperser disintegration and a maximum solubilization of 6% was attained at the specific energy input of 4729.24 kJ/kg TS. Solubilization was further enhanced by coupling the optimum disperser condition with varying dosage of alkyl polyglycoside. The maximum solubilization of 11% and suspended solid (SS) reduction of 8.42% were achieved at the disperser rpm, time, and surfactant dosage of 12,000, 30 min, and 12 μL. The alkyl polyglycoside-coupled disperser disintegration showed a higher biogas production of 125.1 mL/gCOD, compared to the disperser-alone disintegration (70.1 mL/gCOD) and control (36.1 mL/gCOD).

A novel conversion of marine macroalgal biomass to biofuel (biohydrogen) via calcium hypochlorite induced dispersion

Environmental pollution due to the consumption of non-renewable energy lead the search for alternative eco-friendly renewable fuel. The study details the biohydrogen production efficiency by potential macroalgal (Ulva reticulata) biomass improved by a disperser combined with calcium hypochlorite pretreatment technology. Calcium hypochlorite was added to decrease the surface energy of the medium induced by sole disperser pretreatment. Optimum condition for algal disperser treatment was 10,000 rpm with 30 min as dispersion time. The specific energy spent for the disintegration of the macroalgal biomass was 1231.58 kJ/kg TS. COD solubilization rate of 11.79% was attained with mechanical pretreatment whereas increased to 20.23% with combined pretreatment. Combination of disperser with calcium hypochlorite significantly reduced the specific energy input spent to 500 kJ/kg TS. The amount of organic materials such as carbohydrates, proteins and lipids released were 680 mg/L, 283 mg/L and 136 mg/L respectively. Thus, the combinative pretreatment with disperser rotor speed (10,000 rpm) for pretreatment time (12 min) and calcium hypochlorite dosage (0.1 g/g) derived as optimum condition for effective solubilization of macroalgal biomass. Biohydrogen production potential was maximum in the macroalgae pretreated with both disperser and calcium hypochlorite recorded highest yield (54.6 mL H₂/g COD) compared to the macroalgae pretreated with disperser alone (31.7 mL H₂/g COD) and untreated macroalgae (11.5 mL H₂/g COD).

Mild hydrogen peroxide interceded bacterial disintegration of waste activated sludge for efficient biomethane production

Regardless of the issue of sludge management all over the world, the role of phase separated pretreatment prior to anaerobic digestion are more promising in terms of energy efficient biomethane production. However, the effect of phase separated pretreatment (dissociation of extracellular polymeric substances (EPS) followed by biological pretreatment in a two-step process) must be sensibly evaluated from various perceptions to consolidate its effectiveness in sludge management and bioenergy recovery. In this study, mild hydrogen peroxide induced bacterial pretreatment (H₂O₂-BP) was employed as phase separated pretreatment to investigate the effectiveness of EPS dissociation prior to biological pretreatment on sludge solubilization and biomethanation. The novelty of this study is the application of mild dosage of hydrogen peroxide at sludge pH for the removal of EPS layer with lesser formation of recalcitrant substances which thereby enhances the disintegration by enzyme secreting bacterial and methane generation. The outcome confirmed that the higher EPS dissociation was achieved at H₂O₂ dosage of 8 μL per 100 mL of sludge with negligible cell lysis. An extractable EPS of 172.8 mg/L was obtained after H₂O₂ treatment. The higher sCOD solubilization of 22% and the suspended solid reduction of 17.14% were achieved in hydrogen peroxide followed by bacterial pretreatment (H₂O₂-BP) as compared to of bacterial pretreatment alone (BP) (solubilization-11% and suspended solids reduction-9.3%) and control (C) sludges (solubilization-5% and suspended solids reduction-4.3%). The methane generation for H₂O₂-BP sludge is 0.174 L/gCOD which is higher than BP (0.078 L/gCOD,) and C sludge (0.02175 L/gCOD). A higher biomass solubilization and increased biomethanation in H₂O₂-BP revealed that dissociation of EPS prior to bacterial pretreatment increases the surface area for bacterial pretreatment facilitating easier accessibility of substrate and enhanced biomethanation.

Surfactant induced microwave disintegration for enhanced biohydrogen production from macroalgae biomass: Thermodynamics and energetics

This research work aimed about the enhanced bio-hydrogen production from marine macro algal biomass (Ulva reticulate) through surfactant induced microwave disintegration (SIMD). Microwave disintegration (MD) was performed by varying the power from 90 to 630 W and time from 0 to 40 min. The maximum chemical oxygen demand (COD) solubilisation of 27.9% was achieved for MD at the optimal power (40%). A surfactant, ammonium dodecyl sulphate (ADS) is introduced in optimal power of MD which enhanced the solubilisation to 34.2% at 0.0035 g ADS/g TS dosage. The combined SIMD pretreatment significantly reduce the treatment time and increases the COD solubilisation when compared to MD. Maximum hydrogen yield of 54.9 mL H₂ /g COD was observed for SIMD than other samples. In energy analysis, it was identified that SIMD was energy efficient process compared to others since SIMD achieved energy ratio of 1.04 which is higher than MD (0.38).

Macroalgae (Ulva reticulata) derived biohydrogen recovery through mild surfactant induced energy and cost efficient dispersion pretreatment technology

Currently identification of alternate fuel is the key area of research under progress to overcome the depletion of fossil fuels, meet the domestic and industrial requirements. Generation of hydrogen, which is a clean fuel gas can solve various environmental related problems. Extensive research is being carried out to increase production of hydrogen through different substrates. This study aims to increase the production of hydrogen from Ulva reticulata (a macroalgal biomass). Initially, the biomass is pretreated mechanically with disperser and a biosurfactant, namely rhamnolipid in order to increase the solubilization of the biomass. The rate of COD liquefaction increased from 14% to 25% with the addition of biosurfactant to the macroalgal biomass, which is further treated mechanically using a disperser. The disperser rotor speed of 12,000 rpm and the specific energy input of 1175 kJ/kg TS (Total Solids) with the disintegration time of 30 min and biosurfactant dosage of 0.075 g/g TS were considered as the optimum parameters for the effective liquefaction of the macroalgal biomass. Approximately 3500 mg/L of the biopolymers were released after the combinative pretreatment (using disperser and biosurfactant). About 80 mL biohydrogen/g COD (Chemical Oxygen Demand) was generated when the biomass was pretreated with both the disperser and biosurfactant while the biomass pretreated with the disperser alone generated just 30 mL biohydrogen/g COD and the untreated biomass generated 5 mL biohydrogen/g COD. Thus, it can be concluded that Ulva reticulata can be utilized effectively to generate biohydrogen.

Impact of novel deflocculant ZnO/Chitosan nanocomposite film in disperser pretreatment enhancing energy efficient anaerobic digestion: Parameter assessment and cost exploration

This paper proposed to interpret the novel method of extracellular polymeric substance (EPS) removal in advance to sludge disintegration to enrich bioenergy generation. The sludge has been subjected to deflocculation using Zinc oxide/Chitosan nanocomposite film (ZCNF) and achieved 98.97% of solubilization which enhance the solubilization of organics. The obtained result revealed that higher solubilization efficiency of 23.3% was attained at an optimal specific energy of 2186 kJ/kg TS and disintegration duration of 30 min. The deflocculated sludge showed 8.2% higher solubilization than the flocculated sludge emancipates organics in the form of 1.64 g/L of SCOD thereby enhancing the methane generation. The deflocculated sludge produces methane of 230 mL/g COD attained overall solid reduction of 55.5% however, flocculated and control sludge produces only 182.25 mL/g COD and 142.8 mL/g COD of methane. Based on the energy, mass and cost analysis, the deflocculated sludge saved 94.1% of energy than the control and obtained the net cost of 5.59 $/t which is comparatively higher than the flocculated and control sludge.

Biofuel production from Macroalgae: present scenario and future scope

The current fossil fuel reserves are not sufficient to meet the increasing demand and very soon will become exhausted. Pollution, global warming, and inflated oil prices have led the quest for renewable energy sources. Macroalgae (green, brown, and red marine seaweed) is gaining popularity as a viable and promising renewable source for biofuels production. Numerous researches have been conducted to access the potential of macroalgae for generating diverse bioproducts such as biofuels. The existence of components such as carbohydrates and lipids, and the lack or deficiency of lignin, create macroalgae an enviable feedstock for biofuels generation. This review briefly covers the potential macroalgal species promoting the production of biofuels and their cultivation methods. It also illustrates the biofuel generation pathway and its efficiency along with the recent techniques to accelerate the product yield. In addition, the current analysis focuses on a cost-effective sustainable generation of biofuel along with commercialization and scaleup.

Recent advances on food waste pretreatment technology via microalgae for source of polyhydroxyalkanoates

Polyhydroxyalkanoates (PHAs) are biodegradable and biocompatible polyester which are biosynthesized from the intracellular cells of microalgae through the cultivation of organic food waste medium. Before cultivation process, food waste must undergo several pre-treatment techniques such as chemical, biological, physical or mechanical in order to solubilize complex food waste matter into simpler micro- and macronutrients in which allow bio-valorisation of microalgae and food waste compound during the cultivation process. This work reviews four microalgae genera namely Chlamydomonas, Chlorella, Spirulina, and Botryococcus, are selected as suitable species due to rapid growth rate, minimal nutrient requirement, greater adaptability and flexibility prior to lower the overall production cost and maximized the production of PHAs. This study also focuses on the different mode of cultivation for the accumulation of PHAs followed by cell wall destabilization, extraction, and purification. Nonetheless, this review provides future insights into enhancing the productivity of bioplastic derived from microalgae towards low-cost, large-scale, and higher productivity of PHAs.

Quantitative analysis of methane and glycolate production from microalgae using undiluted wastewater obtained from chicken-manure biogas digester

Microalgal biomass is often used as a raw material in methane production. Some microalgae possess a complex cell-wall structure which has a low degradability of microorganisms in anaerobic digestion. However, some microalgae produce glycolate, which is excreted outside the cell and can be used to produce methane under anaerobic condition. This research aims to investigate microalgal cultivation using wastewater to reduce nutrients and efficiently create glycolate. Two strains of microalgae (Acutodesmus sp. AARL G023, Chlorella sp. AARL G049) and two microalgal consortia were cultivated at dilutions of 0.5-fold (W50), 0.75-fold (W75) and undiluted wastewater (W100). The results showed that the microalgal consortium with undiluted wastewater (WCW100) consisted of Leptolyngbya sp. (30.4%), Chlorella sp. (16.1%) and Chlamydomonas sp. (52.2%), revealed the highest biomass productivity at 64.38 ± 14.54 mg·L^-1·d^-1 and the highest glycolate productivity at 5.12 ± 0.48 mmol·L^-1·d^-1. The cultivation of microalgae effectively reduced ammonium‑nitrogen (NH₄⁺-N) and soluble reactive phosphorus (SRP) levels in the wastewater at 43.5 ± 1.3% and 49.6 ± 6.9%. Furthermore, WCW100 showed the highest biogas productivity at 1.44 ± 0.07 mL·g^-1·d^-1 and the highest methane content at 58.3 ± 6.0% v/v. This study indicates that there is a definite potential of using undiluted wastewater for microalgal biomass production and glycolate production that can reduce the wastewater volume and be applied as a raw material for methane production.

A novel energetically efficient combinative microwave pretreatment for achieving profitable hydrogen production from marine macro algae (Ulva reticulate)

This study aims to enhance the hydrogen (H₂) production from marine macro algae (Ulva Reticulate) by microwave combined with hydrogen peroxide (H₂O₂) under alkaline condition. Microwave (domestic type) (M) pretreatment of algal biomass at its optimal power (40%) resulted in 27.9% COD solubilization at 15 min time interval. When this optimal microwave power was combined with H₂O₂ (MH) an increment in COD solubilization was achieved at 24 mg H₂O₂/g macroalgae dosage. Under alkaline condition (pH 7-12), microwave and H₂O₂ combination (MHA) yielded better result than MH. At optimal alkaline condition (pH 10), MHA pretreatment shows a COD solubilization of 34%. Microwave in alkaline condition induces decomposition of H₂O₂ and more OH radical synthesis. This synergistically promotes solubilization. The MHA process considerably diminish time and specific energy required for biomass disintegration. Among the samples, highest H₂ yield of 87.5 mL H₂/g COD was observed for MHA.

Nanoparticle induced biological disintegration: A new phase separated pretreatment strategy on microalgal biomass for profitable biomethane recovery

This study involves the application of new phase separated biological pretreatment (PSBP) strategy on microalgal biomass using the nickel nanoparticle induced cellulase secreting bacterial disintegration. Particularly, interest was focussed on cell wall weakening (CWW) of microalgae biomass besides the cell disintegration (CD) and release of organics. During CWW, protein, carbohydrate, cellulose, hemicellulose and DNA were used as evaluation indexes. Similarly, during CD, soluble chemical oxygen demand was used as evaluation index to assess the disintegration effect. A higher CWW was achieved at nickel nanoparticle (Np) dosage of 0.004 g/g SS. During CD, a clear demarcation in biomass solubilisation was achieved by PSBP (36%) than the sole biological pretreatment -BP (24%). The biomethanogenesis test results showed that enhanced methane production of 411 mL/g COD was achieved by PSBP than BP. Energy analysis showed that a higher net energy production of 6.467 GJ/d was achieved by PSBP.

Feasibility analysis of homogenizer coupled solar photo Fenton process for waste activated sludge reduction

In this study, an attempt has been made to reduce the sludge using novel homogenizer coupled solar photo Fenton (HPF) process. At an optimum pH of 3 and Fe²⁺ to H₂O₂ dosage of 1:6, PF process yielded 63.7% solids reduction at a time interval of 45 min. Coupling of homogenizers with photo Fenton (PF) process effectively enhanced treatment efficiency. When homogenizer (specific energy - 1150.694 kJ/kg TS) was coupled with PF, a sharp increase in solid reduction 73.5% and decrease in reaction time (20 min) were observed. Cost benefit analysis revealed the efficiency of HPF process and achieved a net cost of 15.59 USD whereas PF achieved a negative net cost of -82.69 USD. Based on the above study it can be concluded that coupling of homogenizers with PF not only increased its efficiency but also make it field applicable.

Dispersion aided tenside disintegration of seagrass Syringodium isoetifolium: Towards biomethanation, kinetics, energy exploration and evaluation

In this study, an attempt was made to enhance the biomethanation potential of seagrass (Syringodium isoetifolium) by the aid of disperser-tenside (polysorbate 80) disintegration for the first time in literature. A disperser rpm of 10,000 for 20 min and PS 80 dose of 0.000864 g/g TS were selected as ideal parameters for effectual seagrass biomass disintegration. Dispersion aided tenside disintegration (DTD) with a disperser energy consumption of 349 kJ/kg TS, was observed to be efficacious with a biomass lysis rate of 25.6%. The impact of DTD on bioacidification and biomethanation assay with respect to volatile fatty acids concentration (1100 mg/L) and methane generation (0.256 g/g COD), was greater than dispersion disintegration (DD) (800 mg/L; 0.198 g/g COD). Thus, S. isoetifolium is considered as a promising substrate to attain the third generation biofuel goals in the near future.

The effect of substrate/inoculum ratio on the kinetics of methane production in swine wastewater anaerobic digestion

Methane production from swine wastewater was evaluated by using sewage sludge as inoculum in three substrate to inoculum ratios (SIRs) named A (1:1), B (3:1) and C (6:1), with the objective to identify the proportion that optimizes the performance of the process. Duplicated batch bioreactors of 1 L capacity under mesophilic conditions were used to carry out the experiment. The highest biogas yield was observed in A treatment (554 ± 75 mL/g volatile solid (VS)). Cumulative methane production decreased from 382 ± 22 to 232 ± 5 mL/g VS when SIR increased from 1:1 to 6:1. The first-order model and the modified Gompertz equation were used to model the experimental cumulative methane yield giving adjustments with coefficients of determination of 96 and 99% respectively. The effect of the SIR was analysed based on the kinetic parameters of the Gompertz equation, which are methane production potential, maximum methane production rate and lag-phase time. The best performance in terms of the kinetic parameters was obtained for treatment A; however, treatment B could still ensure a stable process. The use of higher inoculum concentration generated 463.1% higher methane production rate and required 77.3% shorter adaptation time (lag phase) in the SIR range studied. When higher SIR was used (e.g. 14:1, previous work), it could be observed that the Gompertz equation also adjusted adequately the experimental data (R ² > 0.99) although the lag-phase time did not remain in a linear relationship with SIR but exponentially above SIR = 6:1. These results demonstrated that when a low amount of inoculum was used, the adaptation time of microorganisms resulted much higher than expected delaying the methane production and extending the time needed to achieve adequate performance of the process.

A critical review on anaerobic digestion of microalgae and macroalgae and co-digestion of biomass for enhanced methane generation

Biogas production using algal resources has been widely studied as a green and alternative renewable technology. This review provides an extended overview of recent advances in biomethane production via direct anaerobic digestion (AD) of microalgae, macroalgae and co-digestion mechanism on biomethane production and future challenges and prospects for its scaled-up applications. The effects of pretreatment in the preparation of algal feedstock for methane generation are discussed briefly. The role of different operational and environmental parameters for instance pH, temperature, nutrients, organic loading rate (OLR) and hydraulic retention time (HRT) on sustainable methane generation are also reviewed. Finally, an outlook on the possible options towards the scale up and enhancement strategies has been provided. This review could encourage further studies in this area, to intend and operate continuous mode by designing stable and reliable bioreactor systems and to analyze the possibilities and potential of co-digestion for the promotion of algal-biomethane technology.

Marsilea spp.-A novel source of lignocellulosic biomass: Effect of solubilized lignin on anaerobic biodegradability and cost of energy products

The present study concerns the liquefying potential of an unusual source of lignocellulosic biomass (Marsilea spp., water clover, an aquatic fern) during combinative pretreatment. The focus was on how the pretreatment affects the biodegradability, methane production, and profitability of thermochemical dispersion disintegration (TCDD) based on liquefaction and soluble lignin. The TCDD process was effective at 12,000 rpm and 11 min under the optimized thermochemical conditions (80 °C and pH 11). The results from biodegradability tests imply that 30% liquefaction was sufficient to achieve enhanced biodegradability of about 0.280 g-COD/g-COD. When biodegradability was >30% inhibition was observed (0.267 and 0.264 g-COD/g-COD at 35-40% liquefaction) due to higher soluble lignin release (4.53-4.95 g/L). Scalable studies revealed that achievement of 30% liquefaction was beneficial in terms of the energy and cost benefit ratios (0.956 and 1.02), when compared to other choices.

Surfactant assisted disperser pretreatment on the liquefaction of Ulva reticulata and evaluation of biodegradability for energy efficient biofuel production through nonlinear regression modelling

The present study aimed to increase the disintegration potential of marine macroalgae, (Ulva reticulata) through chemo mechanical pretreatment (CMP) in an energy efficient manner. By combining surfactant with disperser, the specific energy input was considerably reduced from 437.1 kJ/kg TS to 264.9 kJ/kg TS to achieve 10.7% liquefaction. A disperser rpm (10,000), pretreatment time (30 min) and tween 80 dosage (21.6 mg/L) were considered as an optimum for effective liquefaction of algal biomass. CMP was designated as an appropriate pretreatment resulting in a higher soluble organic release 1250 mg/L, respectively. Anaerobic fermentation results revealed that the volatile fatty acid (VFA) concentration was doubled (782 mg/L) in CMP when compared to mechanical pretreatment (MP) (345 mg/L). CMP pretreated algal biomass was considered as the suitable for biohydrogen production with highest H₂ yield of about 63 mL H₂/g COD than (MP) (45 mL H₂/g COD) and control (10 mL H₂/g COD).

Synergistic impact of sonic-tenside on biomass disintegration potential: Acidogenic and methane potential studies, kinetics and cost analytics

An exploration into the symbiotic impact of sonic-tenside (SDBS - sodium dodecyl benzene sulfonate) on biomass disintegration potential and to reduce the energy consumption was studied. At optimized condition (specific energy input 9600 kJ/kg TS; SDBS dosage 0.07 g/g SS), higher percentage of biomass lysis and solids reduction (23.9% and 19.8%) was obtained in blended sonic-tenside disintegration (STD), than sonic disintegration (SD) (17.6% and 9.8%). The bioacidogenic potential (BAP) assay in terms of volatile fatty acids (VFA) production (722 mg/L) was found to be higher for STD, in comparison to SD (350 mg/L). The impact of STD on anaerobic digestion was evident from its methane yield (0.239 g/g COD), higher than SD (0.182 g/g COD). A monetary evaluation of the present study provides a net gain of 2 USD/ton for STD, indicating the profitability of the technique.

Functionality of surfactants in waste-activated sludge treatment: A review

Proper treatment of waste-activated sludge (WAS) involves three pivotal processes, dewatering, anaerobic digestion, and pollutants removal, which need to be re-assessed urgently. Although many traditional sludge treatments have been developed, it is prudent to enhance the efficiency of sludge treatment using multifunctional, flexible, and environmentally friendly surfactants. With regard to sludge dewatering, surfactants can weaken the binding interaction between sludge flocs and promote the dissolution of extracellular polymeric substances (EPSs), resulting in the release of bound water. Using surfactants in anaerobic digestion promotes the release of enzymes trapped in sludge and improves the activity of enzymes during hydrolysis. Owing to their characteristic encapsulation of hydrophobes into self-assembled aggregates (micelles), surfactants can form host-guest complexes with polycyclic aromatic hydrocarbons (PAHs). Additionally, surfactants can enhance the desorption of heavy metals and prevent the emergence of heavy metal residue. This review summarizes the current surfactant-based sludge treatment technologies according to their roles in sludge disposal solutions. Then, possible mechanisms of surfactants in sludge dewatering, anaerobic digestion, and the removal of organic pollutants and heavy metals are analysed systemically. Finally, changes to sludge treatment via the aid of surfactants are highlighted. This review presents the comprehensive advances in the use of surfactants in WAS reduction, recycling, and risk relief, underscoring their roles in increasing economic efficiency and ensuring environmental quality.

Impact of mild alkali dosage on immobilized Exiguobacterium spp. mediated cost and energy efficient sludge disintegration

Approaches to (extracellular polymeric substance) EPS removal were studied with major aim to enhance the biodegradability and sludge solubilization. In this study, a novel approach of entrapment of bacterial strain was carried out to achieve long term activity of protease secreting bacteria Exiguobacterium sp. A mild treatment of potassium hydroxide (KOH) was applied to remove EPS which was followed by entrapment under the biological pretreatment. The efficiency of Exiguobacterium was predicted through dissolvable organic and suspended solids (SS) reduction. The maximum dissolvable organic matter released was 2300mg/L with the solubilization of 23% which was obtained for sludge without EPS (SWOE). For dissolvable organic release, SWOE showed higher final methane production of 232mL/g COD at the production rate of 16.2mL/g COD.d. The SWOE pretreatment was found to be cost effective and less energy intensive beneficial in terms of energy and cost (43.9KWh and -8.2USD) when compared to sludge with EPS (SWE) pretreatment (-177.6KWh and -91.23USD).

Combined pretreatment of electrolysis and ultra-sonication towards enhancing solubilization and methane production from mixed microalgae biomass

This study investigated the effect of combination of pretreatment methods such as ultra-sonication and electrolysis for the minimum energy input to recover the maximal carbohydrate and solubilization (in terms of sCOD) from mixed microalgae biomass. The composition of the soluble chemical oxygen demand (COD), protein, carbohydrate revealed that the hydrolysis method had showed positive impact on the increasing quantity and thus enhanced methane yields. As a result, the combination of these 2 pretreatments showed the greatest yield of soluble protein and carbohydrate as 279 and 309mg/L, which is the recovery of nearly 85 and 90% in terms of total content of them. BMP tests showed peak methane production yield of 257mL/gVS_added, for the hydrolysate of combined pretreatment as compared to the control experiment of 138mL/gVS added.