Improve Biogas Production Research Articles

Pretreatment of Rice Straw for the Improvement of Biogas Production

Improvement of biogas production by pretreatment of rice straw with 0.25 and 0.5 M sodium carbonate at 90, 110, and 130 °C and for 1, 2, and 3 h was investigated, and promising results were obtained. All treated and untreated rice straws were digested under mesophilic conditions (37 °C). Increasing the concentration of sodium carbonate showed significant improving effects, whereas the treatment time showed less impact. The best results, obtained by pretreatment with 0.5 M sodium carbonate at 110 °C for 2 h, resulted in the production of 292 mL of CH4 per gram of VS, whereas untreated rice straw produced 130 mL of CH4 per gram of VS. Compositional, SEM, and FTIR analyses confirmed that structural modification, lignin removal, and cellulose crystalline reduction are responsible for the improvement.

Screening of Factors Affecting Pre-Treatment by Ammonia-N Removal from Poultry Manure Wastewater by Using Soil Water to Improve Biogas Production

In this study, best pre-treatment condition of poultry manure wastewater (PMW) was determined from factorial analysis for the purpose of improving biogas production. Five factors were chosen for factorial screening namely: agitation (0 or 200 rpm), reaction time (2 to 5 hours), type of soil (peat soil or poultry farm soil), soil to water ratio (1:1 or 1:4) and PMW to soil water (SW) ratio (1:4 or 2:3). Based on the result, agitation gave highest contribution in pre-treatment of PMW at 38.36% followed by PMW to SW ratio at 29.76% contribution. In term of interaction, agitation and reaction gave the highest contribution to pre-treatment of PMW at 3.33% contribution. The best pre-treatment condition suggested by Design Expert software was using peat soil as source of soil at SW ratio of 1:6, and mixed with PMW at 1:4 ratio without agitation for 5 hours reaction time. Application of this best pre-treatment condition showed improvement in biogas yield by 82 % from 0.0045 L/g COD using untreated PMW to 0.0248 L/g COD using treated PMW.

A novel one-stage cultivation/fermentation strategy for improved biogas production with microalgal biomass

The use of alga biomass for biogas generation has been studied for over fifty years but until today, several distinct features, like inefficient degradation and low C/N ratios, limit the applicability of algal biomass for biogas production in larger scale. In this work we investigated a novel, one-stage combined cultivation/fermentation strategy including inherently progressing nitrogen starvation conditions to generate improved microalgal biomass substrates. For this strategy, comparable low amounts of nitrogen fertilizers were applied during cultivation and no additional enzymatic, chemical or physical pretreatments had to be performed. The results of this study demonstrate that progressing nitrogen limitation leads to continuously increasing C/N ratios of the biomass up to levels of 24–26 for all three tested alga strains (Chlamydomonas reinhardtii, Parachlorella kessleri and Scenedesmus obliquus). Importantly, the degradation efficiency of the algal cells increased with progressing starvation, leading to strain-specific cell disintegration efficiencies of 35%–100% during the fermentation process. Nitrogen limitation treatment resulted in a 65% increase of biogas yields for C. reinhardtii biomass (max. 698±23mL biogas g−1 VS) when compared to replete conditions. For P. kessleri and S. obliquus, yields increased by 94% and 106% (max. 706±39mL and 586±36mL biogas g−1 VS, respectively).From these results we conclude that this novel one-stage cultivation strategy with inherent nitrogen limitation can be used as a pretreatment for microalgal biomass generation, in order to produce accessible substrates with optimized C/N ratios for the subsequent anaerobic fermentation process, thus increasing methane production and avoiding the risk of ammonia inhibition effects within the fermenter.

Identifying proper agitation interval to prevent floating layers formation of corn stover and improve biogas production in anaerobic digestion

Floating tests were conducted in anaerobic digestion with different OLR of corn stover to investigate formation of floating layers and to find proper agitation interval for preventing floating layer formation. Floating layers were formed in the early stage of no-agitation period. The daily biogas production was decreased by 81.87–87.90% in digesters with no agitation and feeding compared with digesters having agitation. Reduction of biogas production was mainly attributed to poor contact of substrate-microorganisms. Agitation intervals of 10h, 6h, and 2h were found to be proper for eliminating floating layer at OLR of 1.44, 1.78 and 2.11g(TS)L−1d−1, respectively. The proper agitation interval was further validated by anaerobic experiments. It showed that proper agitation interval could not only prevent floating layer formation and achieve high biogas production but also increase energy efficiency of anaerobic digestion. The finding is useful for operating anaerobic digester with corn stover in a cost-effective way.

Comparing the hydrolysis and biogas production performance of alkali and acid pretreatments of rice straw using two-stage anaerobic fermentation

To enhance rice straw degradation and improve biogas production in a two-stage anaerobic system, rice straw was treated with either dilute alkali or acid. Firstly, the effects of NaOH or HCl concentration, temperature and time on glucose conversion, degradation of cellulose and hemi-cellulose were investigated. It was found that glucose conversion rate and the organic matter content were greater with alkali rather than acid pretreatment. Suitable conditions for hydrolysis using NaOH pretreatment were 2% (w/w), 60 h and 60 °C. With these conditions the glucose conversion rate was 55.5%. Secondly, the hydrolysate was used as substrate for batch anaerobic fermentation tests at different organic loadings. The maximum methane yield of hydrolysate from NaOH pretreatment was 193.2 ml g−1 [COD]. For the HCl pretreatment, the maximum methane production rate was 287.0 ml g−1 [COD] which was 43.89% higher than with NaOH. Although the NaOH solution was more efficient in improving rice straw hydrolysis, the hydrolysate from the HCl pretreatment had greater methane production at a similar organic loading.

Valorisation of biodiesel production wastes: Anaerobic digestion of residual Tetraselmis suecica biomass and co-digestion with glycerol.

One of the principal opportunity areas in the development of the microalgal biodiesel industry is the energy recovery from the solid microalgal biomass residues to optimise the fuel production. This work reports the cumulative methane yields reached from the anaerobic digestion of the solid microalgal biomass residues using different types of inocula, reporting also the improvement of biogas production using the co-digestion of microalgal biomass with glycerol. Results demonstrate that the solid microalgal biomass residues showed better biogas production using a mesophilic inoculum, reaching almost two-fold higher methane production than under thermophilic conditions. Furthermore, the solid microalgal biomass residues methane production rate showed an increase from 173.78 ± 9.57 to 438.46 ± 40.50 mL of methane per gram of volatile solids, when the co-digestion with glycerol was performed. These results are crucial to improve the energy balance of the biodiesel production from Tetraselmis suecica, as well as proposing an alternative way to treat the wastes derived from the microalgae biodiesel production.

Biomethane production and physicochemical characterization of anaerobically digested teff (Eragrostis tef) straw pretreated by sodium hydroxide

The biogas production potential and biomethane content of teff straw through pretreatment by NaOH was investigated. Different NaOH concentrations (1%, 2%, 4% and 6%) were used for each four solid loadings (50, 65, 80 and 95g/L). The effects of NaOH as pretreatment factor on the biodegradability of teff straw, changes in main compositions and enhancement of anaerobic digestion were analyzed. The result showed that, using 4% NaOH for pretreatment in 80g/L solid loading produced 40.0% higher total biogas production and 48.1% higher biomethane content than the untreated sample of teff straw. Investigation of changes in chemical compositions and physical microstructure indicated that there was 4.3–22.1% total lignocellulosic compositions removal after three days pretreatment with NaOH. The results further revealed that NaOH pretreatment changed the structural compositions and lignin network, and improved biogas production from teff straw.

Enhancing Biogas Production from Pumpkin (Telfairia occidentalis) Stalk Waste through Its Blending with Cow Dung and Alkaline Sodium Hydroxide Pretreatment

Improvement of biogas production from Pumpkin (Telfairia occidentalis) stalk waste through its blending with cow dung and alkaline sodium hydroxide pretreatment was investigated. Untreated pumpkin stalk waste (Un-PST) acted as the control. Initial verification carried out using this waste led to the present investigation. The batch digestion process anaerobically took place for 30 days under ambient atmospheric conditions. Bio-digesters of 41.00 dm working volume were utilized. Cumulative volume of biogas yield from the cow dung blended with pumpkin stalk (PST-cd) was 3.57 dm/TS.kg and alkaline treated waste (PST-t) gave 4.48 dm/TS.kg, while untreated pumpkin stalk waste (Un-PST), yielded 1.50 dm 3 /TS.kg. Each of these systems also produced flammable gas at different times: the Un-PST -15 th day, PST-cd -5 th day and PST-t-8 th day, respectively. Paired sample T-Test carried out on volume of gas data indicated that t (t statistic) was 5.15 for paired sample Un-PST & PST-cd while 6.51 for Un-PST & PST-t with degree of freedom as 29; at 95% conf. interval. Hence, there was a significant (p0.05) difference in volume of gas production Original Research Article Eunice et al.; JSRR, 5(3): 194-202, 2015; Article no.JSRR.2015.087 195 between the untreated and treated waste systems. Overall, results indicate that the yield of biogas from the waste through the different treatments were significantly (p<0.05) enhanced for renewable energy production, sustainable environment and wealth recovery for urban and rural dwellers of developing countries such as Nigeria, when properly harnessed.

Improvement of biogas production from orange peel waste by leaching of limonene.

Limonene is present in orange peel wastes and is known as an antimicrobial agent, which impedes biogas production when digesting the peels. In this work, pretreatment of the peels to remove limonene under mild condition was proposed by leaching of limonene using hexane as solvent. The pretreatments were carried out with homogenized or chopped orange peel at 20–40°C with orange peel waste and hexane ratio (w/v) ranging from 1 : 2 to 1 : 12 for 10 to 300 min. The pretreated peels were then digested in batch reactors for 33 days. The highest biogas production was achieved by treating chopped orange peel waste and hexane ratio of 12 : 1 at 20°C for 10 min corresponding to more than threefold increase of biogas production from 0.061 to 0.217 m3 methane/kg VS. The solvent recovery was 90% using vacuum filtration and needs further separation using evaporation. The hexane residue in the peel had a negative impact on biogas production as shown by 28.6% reduction of methane and lower methane production of pretreated orange peel waste in semicontinuous digestion system compared to that of untreated peel.

Process Improvement of Biogas Production from Anaerobic Co-digestion of Cow Dung and Corn Husk

A study of organic loading rate (OLR) and effect of NaOH concentration on the pretreatment stage of corn husk (CH) was conducted by Face-Centered Central Composite Design (CCF) to improve the biogas production. Three levels of OLR at 25.0g VS · L−1 · d−1 (OLR25), 35.0g VS · L−1 · d−1 (OLR35), and 45.0g VS · L−1 · d−1 (OLR45) were performed with NaOH pretreatment concentration of CH at 25.0% (N25), 35.0% (N35), and 45.0% (N45) (w/w). The optimum production of biogas at 67.6mL · min−1 with methane concentration of 63.4% has been obtained at the application of OLR at 43.6g VS · L−1 · d−1 and NaOH concentration at 33% (w/w).

Anaerobic Fungi and Their Potential for Biogas Production.

Plant biomass is the largest reservoir of environmentally friendly renewable energy on earth. However, the complex and recalcitrant structure of these lignocellulose-rich substrates is a severe limitation for biogas production. Microbial pro-ventricular anaerobic digestion of ruminants can serve as a model for improvement of converting lignocellulosic biomass into energy. Anaerobic fungi are key players in the digestive system of various animals, they produce a plethora of plant carbohydrate hydrolysing enzymes. Combined with the invasive growth of their rhizoid system their contribution to cell wall polysaccharide decomposition may greatly exceed that of bacteria. The cellulolytic arsenal of anaerobic fungi consists of both secreted enzymes, as well as extracellular multi-enzyme complexes called cellulosomes. These complexes are extremely active, can degrade both amorphous and crystalline cellulose and are probably the main reason of cellulolytic efficiency of anaerobic fungi. The synergistic use of mechanical and enzymatic degradation makes anaerobic fungi promising candidates to improve biogas production from recalcitrant biomass. This chapter presents an overview about their biology and their potential for implementation in the biogas process.

Biogas production improvement and C/N control by natural clinoptilolite addition into anaerobic co-digestion of Phragmites australis, feces and kitchen waste

Anaerobic co-digestion (A co-D) performance of Phragmites australis, feces and kitchen waste with addition of clinoptilolite (one main kind of zeolite) was investigated to evaluate the improvement of biogas/methane production and internal mechanism of nitrogen and organics control. A better biogas/methane production was observed by 10% clinoptilolite (v/v) than bentonite and diatomite, with the shortest lag phase of 0.070d−1, the max rate of 15.89L/(kgVSday) and ultimate biogas production of 308.2L/kgVS as the modified Gompertz equation predicted. Accordingly, the content of methane in the biogas was increased from 44.10% to 65.30%. Furthermore, the clinoptilolite inhibited the acidification of digestion liquid (optimum pH 7.0–7.5) and enhanced the VFAs (acetic acid, propionic acid and butyric acid) destruction. Moreover, 10% of clinoptilolite optimally enhanced the microbial utilization of Ca2+/Mg2+, controlled the C/N ratio, and improved the biogas production as well as NH3-N/NO3-N inhibition efficiency.

Anaerobic co-digestion of food waste with MSW incineration plant fresh leachate: process performance and synergistic effects

Abstract The objectives of this study were to examine the feasibility of improving biogas production and process stability of anaerobic mono-digestion of food waste by co-digesting with MSW incineration plant fresh leachate, and to identify the key factors governing performance and stability of anaerobic digestion. For this purpose, a series of semi-continuous experiments were carried out. During a long-term operation period, contrary to the failure of mono-digestion of food waste, anaerobic co-digestion with fresh leachate exhibited a much better performance and stability in terms of high CH 4 yields (375.9–506.3 mL/g VS added ), high VS removals (66.9–81.7%), no VFA inhibition, and stable pH (7.2–7.8). The unstable mono-digestion of food waste was recovered from process imbalance by supplementing trace metal elements (Fe, Co, Mo, Ni), as indicated by the increased CH 4 yields (from 384.1 to 456.5 mL/g VS added ), the decreased propionate concentration (from 899.0 to 10.0 mg/L), and the increased pH (from 6.9 to 7.4). These results were in line with our analytical results that the food waste was deficient in trace metal elements, and fresh leachate was rich in them. Co-digestion strategy provided abundant trace elements for anaerobic process. Our results clearly demonstrated that the deficiency of metal elements was the reason causing the unstable performance of anaerobic mono-digestion of food waste, which was corrected by co-digesting with fresh leachate. This research provides a more technically and economically feasible approach to co-treating and co-utilizing food waste and fresh leachate from MSW incineration plant.

Enhancing biogas production from anaerobic biodegradation of the organic fraction of municipal solid waste through leachate blending and recirculation.

Leachate recirculation has a profound advantage on biodegradation of the organic fraction of municipal solid waste in landfills. Mature leachate from older sections of landfills (>10 years) and young leachate were blended and added to organic fraction of municipal solid waste in a series of biomethane potential assay experiments with different mixing ratios of mature and young leachate and their effect on biogas production was monitored. The improvement in biogas production was in the range of 19%-41% depending on the ratio of mixing old and new leachate. The results are conclusive that the biogas generation could be improved by blending the old and new leachate in a bioreactor landfill system as compared with a conventional system employed in bioreactor landfills today for recirculating the same age leachate.

2단 혐기성소화조의 슬러지 반송율 변화를 통한 Bio-Gas 생산 증대

This study has cross checked the change of internal sludge-recycle in Anaerobic-Digestion, and researched about not only the improvement of Bio-gas production from the digested sludge but also the efficient method of sludge minimization. Ultimate object of the study is to reduce the amount of sludge by the improved efficiency of contact with the organic-matter and the microbes in Anaerobic-Digestion. The sludge-recycle fluidized sludge layer and raised the activity of the sludge, the optimal sludge-recycle ratio, VS and COD removal ratio were 1,000%, 28.2% and 27.7%, respectively. Through these results of this study, it may be of use to treat waste sludge by the sludge-recycle ratio in terms of minimization and circulation of resources.

Feasibility of NaOH-treatment for improving biogas production of digested Spartina alterniflora

In order to improve the biotransformation rate of Spartina alterniflora (SA) and evaluate the feasibility of NaOH-treatment as a pretreatment of digested SA (DSA) for advanced anaerobic biogasification, two experiments were conducted under lab-scale conditions. First, SA was directly digested under 35 ± 1 °C with initial total solid (TS) loading of 20% (the first stage). After 90 day's reaction, cumulative biogas yield of SA and average methane content were 388 ± 22 ml g−1 TSadded and 59.62 ± 1.88%, respectively. Then the DSA was treated with 5% NaOH solution and was used for advanced biogasification (the second stage). The cumulative biogas yield of NaOH-treatment and control were 210 ± 11 ml g−1 TSadded and 103 ± 16 ml g−1 TSadded, respectively, with 70.78 ± 2.11% and 76.92 ± 1.94% of average methane content. The total cumulative biogas yield (sum of the first stage and the second stage of NaOH-treatment) and TS removal rate of SA were 495 ± 24 ml g−1 TSadded and 76.85 ± 1.94%. After NaOH treatment, surface lignin and some carbohydrate of DSA were destructed into lignin fragment, organic acids, and some other small molecular organic matter; while the skeleton structure of lignin and cellulose were not destructed significantly. The results of 13C NMR showed that methyl and carboxylic C groups of DSA were decomposed significantly. The results indicated that NaOH-treatment was a good pretreatment for DSA.

Ultrasound pretreatment for enhanced biogas production from olive mill wastewater

This study investigates applicability of low frequency ultrasound technology to olive mill wastewaters (OMWs) as a pretreatment step prior to anaerobic batch reactors to improve biogas production and methane yield. OMWs originating from three phase processes are characterized with high organic content and complex nature. The treatment of the wastewater is problematic and alternative treatment options should be investigated. In the first part of the study, OMW samples were subjected to ultrasound at a frequency of 20kHz with applied powers varying between 50 and 100W under temperature controlled conditions for different time periods in order to determine the most effective sonication conditions. The level of organic matter solubilization at ultrasound experiments was assessed by calculating the ratio of soluble chemical oxygen demand/total chemical oxygen demand (SCOD/TCOD). The results revealed that the optimum ultrasonic condition for diluted OMW is 20kHz, 0.4W/mL for 10min. The application of ultrasound to OMW increased SCOD/TCOD ratio from 0.59 to 0.79. Statistical analysis (Friedman’s tests) show that ultrasound was significantly effective on diluted OMW (p<0.05) in terms of SCOD parameter, but not for raw OMW (p>0.05). For raw OMW, this increase has been found to be limited due to high concentration of suspended solids (SS). In the second part of the study, biogas and methane production rates of anaerobic batch reactor fed with the ultrasound pretreated OMW samples were compared with the results of control reactor fed with untreated OMW in order to determine the effect of sonication. A nonparametric statistical procedure, Mann–Whitney U test, was used to compare biogas and methane production from anaerobic batch reactors for control and ultrasound pretreated samples. Results showed that application of low frequency ultrasound to OMW significantly improved both biogas and methane production in anaerobic batch reactor fed with the wastewater (p<0.05). Anaerobic batch reactor fed with ultrasound pretreated diluted OMW produced approximately 20% more biogas and methane compared with the untreated one (control reactor). The overall results indicated that low frequency ultrasound pretreatment increased soluble COD in OMW and subsequently biogas production.

Programmed Iron Oxide Nanoparticles Disintegration in Anaerobic Digesters Boosts Biogas Production

A novel concept of dosing iron ions using Fe3O4 engineered nanoparticles is used to improve biogas production in anaerobic digestion processes. Since small nanoparticles are unstable, they can be designed to provide ions in a controlled manner, and the highest ever reported improvement of biogas production is obtained. The nanoparticles evolution during operation is followed by an array of spectroscopic techniques.

Improved Biogas Production from Chicken Manure Anaerobic Digestion Using Cereal Residues as Co-substrates

Because of the resource abundance and high total nitrogen content, chicken manure (CM) is very suitable for anaerobic digestion (AD). In this study, a set of comparative assays was performed on the AD of CM using three main cereal residues (CRs) as co-substrates under various mixing combinations, with a total solid concentration of 8%. Under mesophilic conditions at 35 ± 1 °C, all combinations of CM and CRs significantly improved biogas and methane yields. Co-digestion of CM and corn stalks (CS) showed higher cumulative biogas productions than that of CM/wheat straw (WS) and CM/rice straw (RS). After 60 days of fermentation, the highest methane contents were produced by CM/WS, CM/CS, and CM/RS at a total solid (TS) ratio of 50:50 of 345, 383, and 378 mL/g of removed volatile solids (VSremoved), respectively. The value between 15 and 25 has been suggested as the optimal range of the C/N ratio for the co-fermentation of CM with CRs. The results of the volatile fatty acid/alkalinity analysis clearly demonstr...

Optimization and fabrication of a portable biogas reactor

The study was conducted to investigate the production of biogas from kitchen waste (KW) with co-digestion of cow manure (CM) by using anaerobic digestion process. The experimental protocol was defined to examine the effect of organic loading rate (OLR), temperature, and NaOH-treatment on the efficiency of the production of biogas. A portable biogas reactor was fabricated for efficient biogas production which included an agitation and a heating system. The KW and CM were co-digested at ratios of 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1 and 8:1 respectively at loading rates of 50, 100,150, 200, 250, 300, 350, and 400 g/L. The highest degradation rate of 7.96 ml/g was obtained from the loading rate of 200 g/L. Furthermore, KW was co-digested at different temperatures 25, 35, 40, 45, and 500C, maintaining the same loading rate of 200 g/L and the highest degradation rate of 7.98 ml/g was inspected at temperature 350C. The alkali (NaOH) was used to treat KW to improve biogas production and four NaOH doses 0.5%, 1.0%, 1.5%, and 2.0% on wet matter basis of KW were applied. The highest degradation rate 13.21ml/g was obtained from 1.5% NaOH which was almost double compared to untreated KW. In addition, 39.74 % more biogas could be produced from 1.5% NaOH-treated KW than untreated KW. The results were further verified by scaling up to a semi-continuously-operating pilot-plant reactor co-digesting KW with CM as bacterial seed and confirmed that no negative impact was imposed at optimized conditions. DOI: http://dx.doi.org/10.3329/jce.v27i2.17799 Journal of Chemical Engineering, IEB Vol. ChE. 27, No. 2, December 2012: 36-40