Kg Of Volatile Solids Research Articles

Performance evaluation of various bioreactors for methane fermentation of pretreated wheat straw with cattle manure

AbstractThis paper examines the performance results of configured semi-continuous mesophilic bioreactors for methane fermentation of pretreated wheat straw co-digested with cattle manure. The semi-continuous process was carried out in three different types of bioreactors, i.e. continuous stirred tank reactor (CSTR), fixed film reactor (FFR), and conventional floating drum reactor (CR), with an organic loading rate of 2.2 kg of volatile solids (VS)/day. The observed results revealed that the configuration of the FFR increased the methane production yield by 41.1%. However, the configuration of the CSTR had only a marginal effect on enhancement of methane production yield (yield increased only by 10.6%) compared to the CR. The VS removal for digesters did not vary much at the same organic loading rate. The study revealed that the pretreated wheat straw with the FFR had yield methane production of 0.342 m

Cooked and uncooked food waste: A viable feedstock for generation of value added products through biorefinery approach

In the municipal solid waste, both cooked food waste (CFW) and uncooked food waste (UFW) are present, which need stabilization. In the proposed process, simultaneous generation of biogas, biomanure and a mixture of volatile fatty acids (VFA's) through anaerobic biorefinery approach were examined. The experimentations divulged that CFW having an average total solids (TS) and volatile solids (VS) in the range of 23% and 17%, yielded biogas of 0.47m3/(kg VS reduced) and biomanure of 0.29kg/(kg CFW) in single stage biomethanation process, whereas when the same waste was subjected to two stage process (acidogenic followed by methanogenic), it resulted in getting VFA's of 0.44kg/(kg VS reduced), biogas of 0.18m3/(kg VS reduced) and biomanure of 0.27kg/(kg CFW). Similarly, UFW having average TS and VS in the range of 10% and 9%, yielded biogas of 0.38m3/(kg VS reduced), biomanure of 0.13kg/(kg UFW) and VFA's of 0.31kg/(kg VS reduced), biogas of 0.14m3/(kg of VS reduced), biomanure of 0.12kg/(kg UFW) in single and two stage processes, respectively. The study disclosed that two stage process was preferred over single stage for obtaining VFA, biogas and biomanure that are known as value added products.

Enhancement of biogas production at the municipal wastewater treatment plant by co-digestion with poultry industry waste

Municipal wastewater treatment plants (WWTPs) are energy-intensive and thus cost-intensive facilities; therefore, it is crucial to increase energy production directly at the WWTP. Enhancement of biogas production by addition of external substrates is one of the solutions to increase energy self-sufficiency of the WWTPs with an additional benefit of cutting down the greenhouse gas emission. The main aim of the work was to investigate full utilization of the capacity of full-scale digesters at the municipal WWTP by addition of poultry industry waste. At first, laboratory trials were conducted in order to identify the most suitable dose for co-digestion with primary and waste activated sludge and finally, based on the achieved laboratory results, full-scale trials were carried out directly at the municipal WWTP. Poultry industrial waste yielded between 0.39 and 0.88m3 of methane per kg of volatile solids during laboratory trials, depending on the added concentration. During full-scale investigation yield of 0.81m3/kgVS was achieved. Enhanced biogas production improved WWTP energy self-sufficiency bringing closer to the aim of increasing the share of self-produced energy up to 80%.

Recent Patents and Research Studies on Biogas Production from Bioresources and Wastes

In this review paper, recent research and developments studies dealing with the bioconversion of bioresources and biowastes into biogas will be studied and discussed. Several kinds of natural feedstocks were analysed for their aptitude to produce gaseous biofuels such as woods, grasses, algae, agricultural residues, industrial by-products and household wastes. The related research studies revealed promising production yields including 400 L of methane (CH4) per Kg of volatile solids (VS) for Willow shoots, 270 L CH4/Kg VS for macro alga Ulva lactuca and 493 L CH4/Kg VS for paper wastes. Overall, the main objective is to present the research undertakings and findings in the scientific and industrial communities on biogas production procedure, its influencing factors and upgrading into biomethane.

Treatment of natural rubber latex serum waste by co-digestion with macroalgae, Chaetomorpha sp. and Ulva intestinalis, for sustainable production of biogas

AbstractBiogas production is proposed as an alternative approach to using natural rubber Hevea brasiliensis latex serum, a major waste product from the production of concentrated latex. To make the most efficient use of the reactor size, the addition of macroalgal biomass as a co-substrate to the fermentation system was investigated. The biogas yield of latex serum as a single substrate was (398 ± 14) L per kg of volatile solids added (VSA). For the co-digestion system, algae mixed with serum were investigated at wet mass ratios of Chaetomorpha sp. to Ulva intestinalis to serum at 3 : 0 : 1, 2 : 0 : 2, 1 : 0 : 3, 0 : 1 : 3, 0 : 2 : 2 and 0 : 3 : 1. The co-digestion system with latex serum at 2 to 3 out of 4 parts produced the highest biogas yields within the range of 422-460 L kg

Operation and Performance of a Farm-Scale Anaerobic Sequencing Batch Reactor Treating Dilute Swine Manure

Abstract. A 400 m3 anaerobic sequencing batch reactor (ASBR) treating dilute (0.30% to 1.0% total solids) swine manure produced by a 120-sow farrow-to-finish farm was monitored for one calendar year. The digester was operated at full reactor volume (20-day hydraulic retention time, HRT) and at conditions considered optimal for biogas production (5-day HRT). Reactor temperature during 20-day HRT operation ranged between 22°C and 32°C, and solids retention time (SRT) averaged 51 days. During 5-day HRT operation, reactor temperature was 22°C to 24°C and SRT averaged 26 days. Organic matter removal efficiency, measured as the difference between daily mass of chemical oxygen demand (COD) entering the reactor and COD leaving with decanted liquids, was 73% during 20-day HRT operation and 57% during 5-day HRT operation. Methane yield was 0.55 m3 CH4 kg-1 volatile solids (VS) during 20-day HRT and 0.38 m3 CH4 kg-1 VS during 5-day operation. In general, organic matter removal was lower and methane yield was higher than results using similar manure in laboratory-scale reactors. Volumetric reactor efficiency (VRE) was 0.18 m3 CH4 m-3 reactor d-1 under both operating conditions. Flushed manure was diluted 30:70 with recycled aerobic lagoon effluent to provide sufficient volume to achieve 5-day HRT operation. The VRE of an ASBR treating flushed manure without lagoon effluent dilution at 5-day HRT was estimated to be greater than 0.70 m3 CH4 m-3 reactor d-1 based on microbial kinetic models.

Comparative study of methanogens in one- and two-stage anaerobic digester treating food waste

AbstractChanges in methanogenic archaea were investigated in pilot-scale experiments during one- and two-stage mesophilic anaerobic digestion (AD) of food waste. Methane yields were 379.7±75.3 liters of methane per kg of volatile solids [L-CH4(kg-VS)−1] added to the system, during one-stage operation, and 446±922 L-CH4(kg-VS)−1added during two-stage operation. Populations of methanogenic archaea were monitored quantitatively by targeting the functional gene for methyl-coenzyme-M reductase (mcrA) using real-time quantitative polymerase chain reaction techniques. During one-stage operation, meanmcrAgene concentrations were 2.48×109±2.7×109copies ml−1. Two-stage operation yielded meanmcrAgene concentrations of 9.85×108±8.2×108copies ml−1in the fermentation and 1.76×1010±8.5×109copies ml−1in the methanogenesis reactors, respectively. Diversity of archaea in the methanogenic reactors was investigated by denaturing gradient gel electrophoresis targeting the V3 region of 16S rRNA of archaea. The Shannon index (H) was 2.98 for one-stage operation and 7.29 for two-stage operation, suggesting greater archaeal diversity in the two-stage AD. The fivefold increase in methanogenic archaea populations during the two-stage operation, as indicated bymcrAgene concentration, corresponded to an increase in methane production rates. While the diversity may also be related to the stability of the microbial bioprocesses and improved methane production rates, the correlation between diversity and production rates should be studied further.

Thermophilic two-phase anaerobic digestion of source-sorted organic fraction of municipal solid waste for bio-hythane production: effect of recirculation sludge on process stability and microbiology over a long-term pilot-scale experience.

A two-stage thermophilic anaerobic digestion process for the concurrent production of hydrogen and methane through the treatment of the source-sorted organic fraction of municipal solid waste was carried out over a long-term pilot scale experience. Two continuously stirred tank reactors were operated for about 1 year. The results showed that stable production of bio-hythane without inoculum treatment could be obtained. The pH of the dark fermentation reactor was maintained in the optimal range for hydrogen-producing bacteria activity through sludge recirculation from a methanogenic reactor. An average specific bio-hythane production of 0.65 m(3) per kg of volatile solids fed was achieved when the recirculation flow was controlled through an evaporation unit in order to avoid inhibition problems for both microbial communities. Microbial analysis indicated that dominant bacterial species in the dark fermentation reactor are related to the Lactobacillus family, while the population of the methanogenic reactor was mainly composed of Defluviitoga tunisiensis. The archaeal community of the methanogenic reactor shifted, moving from Methanothermobacter-like to Methanobacteriales and Methanosarcinales, the latter found also in the dark fermentation reactor when a considerable methane production was detected.

Optimization of anaerobic fermentation of kitchen waste

Anaerobic fermentation is a suitable method of energetic and material utilisation of waste coming from restaurants and canteens. Laboratory experiments of wet anaerobic fermentation were performed in a continuous reactor and in batch reactors under mesophilic conditions. Effects of hydraulic retention time, organic loading rate, period of feeding and recirculation of digestate were examined in the continuous reactor. Effects of substrate pre-treatment (crushing, heating, freezing) were examined in the batch reactors. Degree of substrate degradation ranged between 83–85% within hydraulic retention time of 2–30 days. Appropriate organic loading rate was found in the range 2–3 kg of volatile solids per m3/day. Recirculation of digestate (both an inoculum for fresh substrate and replacement of fresh water supply) caused an increase in ammonia concentration and led to immediate inhibition of the process. The results further showed a positive effect of substrate pre-treatment in the initial phase of fermentation. However, degree of degradation did not show a significant increase for the period of 20 days of fermentation.    

Biodigestão anaeróbia de dejetos de poedeiras coletados após diferentes períodos de acúmulo

O objetivo do trabalho foi avaliar a interferência do tempo de acúmulo sobre o desempenho do processo de biodigestão anaeróbia de dejetos de aves de postura. O experimento foi conduzido em delineamento inteiramente casualizado com quatro tratamentos que constaram de 1, 8, 15 e 22 dias de acúmulo dos dejetos, efetuando-se cinco repetições por tratamento, totalizando assim 20 biodigestores. Foram utilizados biodigestores do tipo batelada de bancada com capacidade útil para 3 litros de substrato em fermentação. A eficiência do processo de biodigestão foi avaliada pelas reduções de sólidos totais (ST), sólidos voláteis (SV), número mais provável (NMP) de coliformes totais e termotolerantes, além das produções e dos potenciais de produção de biogás. Foram observadas reduções significativas dos conteúdos de SV presentes nos dejetos de aves à medida que se aumentaram os dias de acúmulo, sendo observados teores de SV (em % dos ST) de 97,1 e 75,6% no primeiro e após 22 dias de acúmulo, respectivamente. A redução de SV contribuiu para reduzir a produção e os potenciais de produção do biogás à medida que se aumentaram os dias de acúmulo, sendo observada redução de 37,2% no potencial de produção de biogás kg de SV-1 entre o menor e maior período de acúmulo, ou seja, 6,81 litros de biogás a menos por dia de acúmulo para cada kg de SV adicionado. Também foram observadas reduções de 100% no NMP de coliformes totais e termotolerantes ao final do processo, independente do tratamento testado. O tempo de estocagem contribui para reduzir os potenciais de produção de biogás dos dejetos de aves de postura.

Suitability of Canola Meal forAnaerobic Co-digestion with Dairy Manure

Due to the renewed interest in biogas production, co-digestion of livestock manure, especially dairy manure, and other agro-wastes has emerged as an appropriate practice in enhancing the economic viability of anaerobic digestion. In this study, various ratios of canola meal and dairy manure (100% canola meal, 10% canola meal and 90% manure, 20% canola meal and 80% manure, 40% canola meal and 60% manure, and 100% manure) by volume basis were co-digested in 0.5 L batch bioreactors at a temperature of 35°C ±1°C for 25 days and a loading of 7.5% total solids (TS). Pre- and post-digestion samples were collected and analyzed for TS, volatile solids (VS), nutrients, pH, volatile fatty acids (VFAs), fiber, and chemical oxygen demand (COD). Biogas yield was measured daily using the water displacement method, and gas composition (mainly methane, CH4) was analyzed weekly within 72 h of collection using a gas chromatograph (HP 5890 Series II) equipped with a flame ionization detector (FID). Results indicated that 0% canola meal (100% manure) and 100% canola had specific methane yields of 352 and 83 L CH4 kg-1 VS, respectively. Addition of canola meal in the dairy manure resulted in decreased cumulative biogas and specific methane yield. This is suspected to be caused by the elevated levels of VFAs of more than 4000 mg L-1 in canola meal and dairy manure mixtures. Alternative methods should be explored to alleviate the inhibition in biogas production caused by elevated VFAs.

Solid-State Anaerobic Digestion of Corn Stover for Biogas Production

The effects of temperature, feedstock/inoculum (F/I) ratio, and total solid (TS) content on biogas production from corn stover by solid-state anaerobic digestion (SS-AD) were studied. At an F/I ratio of 3.44, polysaccharide conversion under thermophilic conditions (55C) was 32% higher than under mesophilic conditions (37C), resulting in higher biogas yield. SS-AD performed as expected in the TS content range of 22% to 27% at 37C, while an increase in TS content from 22% to 27% resulted in a 29.8% decrease in biogas yield at 55C. Particle size reduction of corn stover from 15 to 5 mm had no significant improvement on biogas yield (p > 0.05). The highest biogas production of 403.7 L kg-1 volatile solids (VS) fed was obtained at 55C with TS content of 22%, F/I ratio of 4.58, and particle size of 5 mm.

A mechanistic model for simulating methane emissions from unstirred liquid manure storages

The objective of the study was to develop a mechanistic model of methane (CH4) producing processes in unstirred conditions with potential application for estimating CH4 emissions from anaerobic manure storage facilities. Although models for describing anaerobic digestion processes are available, they largely relate to anaerobic digesters, and do not directly apply to the prediction of CH4 emissions from liquid manure storage. Based on extant models, six biochemical steps were described: hydrolysis, acetogenesis, hydrogenogenesis, homoacetogenesis, hydrogenous methanogenesis and acetic methanogenesis, performed by five bacterial groups. The model contains six state variables, and mass flow is mostly generated and quantified using bacterial kinetics. The model was coded in acslX and a fourth-order Runge-Kutta method with an integration step size of 0.05 d was used for numerical integration. The time courses of CH4 production and volatile fatty acid (VFA) concentration of two laboratory-scale liquid manure storage tanks, both filled with liquid sow manures and running in unstirred and constant 25°C conditions, were well predicted, with correlation coefficients over 0.90. Discrepancies between predicted and measured CH4 production and VFA concentration were mainly due to random variation of observed data. The model was sensitive to parameters describing hydrolysis and the kinetics of acetogenic and acetate methanogenic bacteria. Simulations based on the Intergovernmental Panel on Climate Change model (Tier II) predicted 260 g CH4 kg-1 volatile solids (VS, assuming maximum CH4 producing capacity of 0.48 and methane conversion factor of 80%), whereas the measured value was 78.3 g CH4 kg-1 VS after 146 d and the mechanistic model predicted 74.8 g CH4 kg-1 VS. The model developed in this study appears to be better suited to batch manure storage than the IPCC model.

Performance of a sisal fibre fixed-bed anaerobic digester for biogas production from sisal pulp waste

A single stage anaerobic digester employing a sisal fibre waste fixed bed was studied for biogas production from sisal pulp waste. The fibre was colonized by microorganisms involved in biogas production. The sisal pulp waste to be digested was fed from the top and was sprinkled intermittently with recirculating leachate from the material. Organic loading rates of 0.1-10 kg volatile solids (VS) m-3d-1 could be applied and methane yields in the range of 0.13-0.48 m3 CH4 kg-1 VS added were obtained. The average methane content in the biogas produced from sisal pulp waste was 55%, and the biogas production rate was 0.15-0.54 m3m-3d-1. The methane yield obtained and the highest organic loading rate that could be sustained by this simple, fixed-bed digester are indications of an attractive system in terms of performance and reliability. It is concluded that the sisal fibre waste fixed bed is a promising carrier for microbes and can be employed for long-term operation without changing the bed.

Effect of phase separation on anaerobic digestion of kitchen waste

The anaerobic digestion of kitchen waste was studied in both batch and continuous modes. The effect of increasing loading rates on pollutant removal and biogas production was investigated for single-phase digestion and two-phase digestion systems. The anaerobic biodegradability of the kitchen waste obtained from the batch study was 83.5%. Single-stage digestion of kitchen waste was subjected to varying organic loading rates (OLR) ranging from 1.5 kg volatile solids (VS) m–3 d–1 to 5.5 kg VS m–3d–1, with a common hydraulic retention time (HRT) of 15 d. The optimum performance of the system was observed at an OLR of 4.5 kg VS m–3 d–1 in terms of pollutant removal efficiency and biogas production. The removal rates for chemical oxygen demand (COD) and VS at this optimal OLR were 81% and 79%, respectively. Maximum production of the methane was 0.288 m3/kg of VS added. Beyond the optimal OLR, the volatile fatty acids concentration increased and reached its maximum value (9.2 g/L) at the higher loading rate tested (5.5 kg VS m–3 d–1). Anaerobic digestion of the kitchen waste was carried out in a two-stage reactor with different loading rates of 4, 6, and 8 kg VS m–3 d–1. The retention time given to both hydrolysis and methanogenesis phases was 5 d, for a total HRT of 10 d. Best performances were observed in the third run with the OLR of 8 kg VS m–3 d–1. High removal efficiencies for COD and VS were found as 92% and 94%, respectively. A total of 0.22 m3 of methane was produced by 1 kg of VS added. Responses to the fluctuations in the loading rates were sudden and many times unfavourable in the single-stage system, while the fluctuations were suppressed or overcome at a faster rate in the two-stage reactor, without creating too many problems. Comparison of the overall performance showed that phase-separated digesters or the two-stage digesters may offer the best choice for high efficiency, concerning pollutant removal.

Biomethanization of mixtures of fruits and vegetables solid wastes and sludge from a municipal wastewater treatment plant

The possible management of Fruit and Vegetable Solid Wastes (FVSWs) through their simultaneous digestion with the primary sludge of Municipal Wastewater Treatment plants is investigated. This alternative allows the recovery of energy and a solid product that can be used as an amendment for soils that generated the residue, while is not expensive. Results indicate that the ratio of FVSWs to sludge and the pH control are the main variables determining the methane production and concentration. NaHCO3 was selected to achieve the pH control. The results for a ratio of 50% sludge together with 10 g NaHCO3/kg of residue are among the best obtained, with a methane yield of about 90 L per kg of volatile solids, and a methane concentration of 40% (v/v) of the biogas. A 50% reduction of the total solids; 21% reduction of the volatile solids (in terms of total solids); and a pH value of the sludge, which is 6.9 indicate that the digested sludge can be a good material for soil amendment.

Production of biogas from municipal solid waste with domestic sewage

In this study, experiments were conducted to investigate the production of biogas from municipal solid waste (MSW) and domestic sewage by using anaerobic digestion process. The batch type of reactor was operated at room temperature varying from 26 to 36 °C with a fixed hydraulic retention time (HRT) of 25 days. The digester was operated at different organic feeding rates of 0.5, 1.0, 2.3, 2.9, 3.5 and 4.3 kg of volatile solids (VS)/m 3 of digester slurry per day. Biogas generation was enhanced by the addition of domestic sewage to MSW. The maximum biogas production of 0.36 m 3/kg of VS added per day occurred at the optimum organic feeding rate of 2.9 kg of VS/m 3/day. The maximum reduction of total solids (TS) (87.6%), VS (88.1%) and chemical oxygen demand (COD) (89.3%) occurred at the optimum organic loading rate of 2.9 kg of VS/m 3/day. The quality of biogas produced during anaerobic digestion process was 68–72%.

Thermophilic Anaerobic Digestion of the Organic Fraction of Municipal Solid Waste: Start-Up with Digested Material from a Mesophilic Process

The start-up of two thermophilic (55°C) semi-continuously fed, continuously stirred tank reactors for the treatment of the organic fraction of municipal solid waste (OFMSW) was studied using small amounts of inoculum from a full-scale mesophilic reactor treating a mixture of OFMSW and sewage sludge. The inoculum was added into both thermophilic reactors daily for five consecutive days to simulate conditions in which the daily removal of inoculum from the mesophilic process is limited. One reactor also received small amounts of OFMSW together with the inoculum. The feeding of the reactors with loadings of 6.8 kg of volatile solids (VS) m−3 d−1 was started two weeks after the first addition of the inoculum. Stable OFMSW methanation and process performance were soon achieved in both reactors. The performed bioassays also showed that the mesophilic inoculum may start methane production at 55°C and that methane production from added substrates is enhanced if the inoculum is preincubated prior to the substrate additions. Consequently, thermophilic OFMSW treating processes can be started with mesophilic inoculum. The timing of the initiation of the OFMSW feeding should be considered separately.

Anaerobic digestion of poultry manure at high ammonium nitrogen concentrations

Methanogenic fermentation of poultry manure was studied on a laboratory scale at mesophilic temperatures. At average concentrations of Total Solids between 11·3% and 14·1% in the influent (Volatile Solids from 7·8% to 9·7%) and average retention times from 27 to 58 days, no adverse effect on biogas production was observed, despite mean ammonia nitrogen concentrations in the effluent of 4·07 to 5·85 g liter −1 , with extreme values reached as high as 7·5 g liter −1 . With only one exception, in five fermentors of different construction no significant negative correlation between ammonia nitrogen concentration and biogas production, or fermentor productivity, was found. Ammonia nitrogen concentration increased with the increased Volatile Solids loading rate, and, in agreement with data in the literature, the direct dependence of productivity on loading rate was confirmed in the range from approximately 1·2 to 4·0 kg of Volatile Solids per cubic metre per day. The digester construction did not seem to be critical.