Organic Fraction Of Municipal Solid Waste Research Articles

Enzymatic pre-hydrolysis of organic fraction of municipal solid waste to enhance anaerobic digestion

Enzymatic pretreatment was proposed to enhance the anaerobic digestion of Organic Fraction of Municipal Solid Waste (OFMSW). Enzyme cocktails were produced at laboratory scale from Aspergillus niger fermentation on wheat bran (WB) and OFMSW. The effect of enzyme load, reaction time and agitation speed on OFMSW hydrolysis was determined. Results showed that enzymatic hydrolysis of OFMSW improved organic matter solubilisation. Indeed, pretreatment of OFMSW using WB and OFMSW cocktails resulted respectively in 37.1 and 34.6% change of the soluble chemical oxygen demand and 50 and 40.6% change of the reducing sugars.Anaerobic digestion tests showed that enzyme-treated OFMSW yielded higher biomethane production than raw OFMSW. After hydrolysis by WB and OFMSW cocktails, methane potential of OFMSW increased from 189.2 mL gVS−1 to around 607 and 672 mL gVS−1, respectively. The result confirmed that the use of enzyme cocktails derived from raw waste bioconversion could be a valuable approach to improve biomethane potential of organic wastes.

Enhancement of biogas production from organic fraction of municipal solid waste using hydrothermal pretreatment

Anaerobic digestion is a pragmatic approach to recover energy and treat organic fraction of municipal solid waste (OFMSW). This study employs hydrothermal pretreatment to enhance biogas generation during anaerobic digestion of OFMSW in India. OFMSW was pretreated at 80, 100, 120, 140 and 160 °C over heating durations of 0, 15, 30, 60 and 120 min each. Thereafter, batch anaerobic digestion assays of untreated and pretreated OFMSW were carried out using cow excrement as inoculum. The results show that hydrothermal pretreatment is beneficial in improving biodegradability; thereby increasing methane yield and reducing digestion time. Increase in cumulative methane generation ranged between 3% and 32%. Pretreatment at 140 °C for 30 min resulted in highest cumulative methane generation of 200 ml/gVS, with methane content of 68.6% after 18 days; whereas the same for untreated OFMSW was 152 ml/gVS with a methane content of 50.3%, after a digestion period of 28 days. Effect of hydrothermal pretreatment on characteristics of OFMSW and energy required for each pretreatment step were also analysed.

Co-biodrying of sewage sludge and organic fraction of municipal solid waste: A thermogravimetric assessment of the blends

This study investigated the thermogravimetric properties of sewage sludge and organic fraction of municipal solid waste (OFMSW) during their co-biodrying at different fractions. Sewage sludge and OFMSW were co-biodried at the mass proportion of 0%, 42.5% and 85% (of the total wet weight), respectively, with 15% cornstalk as the bulking agent. Results show that of these three raw materials, OFMSW exhibited the lowest ignition temperature and the highest burnout temperature. Moreover, OFMSW had a better comprehensive combustion performance (S) than sewage sludge. Blending OFMSW, sewage sludge and cornstalk showed the highest S value (4.0 × 10−7%2 min−2 °C−3). In addition, there existed certain interactions between the co-combustion process, especially at high temperature stage. The burning characteristics, including ignition performance, burnout efficiency, DTGmax and S increased with fluctuations in the first 6–9 days of co-biodrying process, and then declined in all treatments. Hence, 15-day of biodrying made the product with poor burning behavior (S value of 1.0 × 10−7–1.4 × 10−7%2 min−2 °C−3). More importantly, the optimal combustion performance was observed when co-biodrying the same amount (42.5%) of sewage sludge and OFMSW with the peak of 8.3 × 10−7%2 min−2 °C−3 achieved on day 9. In addition, the blends were easier to burn after the biodrying process.

Study of biological and thermo-chemical pretreatment of organic fraction of municipal solid waste for enhanced biogas yield.

Biogas production from organic fraction of municipal solid waste (OFMSW) not only helps in solid waste management but also combat the food vs fuel dilemma. The presence of lignocellulosic material and other complex compounds in OFMSW hinder biogas production. Therefore, pretreatment is an essential step to increase the hydrolysis rate by converting complex compounds to simpler ones. This work was aimed at effective pretreatment of OFMSW by biological and thermo-chemical means. For biological pretreatment lignin degrading fungal strains, Phanerochaete chrysosporium and Pleurotus ostreatus were employed. Thermo-chemical treatment resulted in higher solubilisation yield in terms of sCOD and VFA making it a more effective method as compared with biological pretreatment. The optimisation of thermo-chemical pretreatment was done by the Box-Behnken design of response surface methodology (RSM). The interactive effect of influencing factors NaOH dose, temperature and time were studied on the response of sCOD, VFA and phenolic content. The sCOD and VFA values were significantly increased by increasing the NaOH concentration, temperature and time to a certain limit. The optimised condition from RSM for maximum solubilisation yield in terms of sCOD, VFA and phenolic content was found to be NaOH dose of 4.72 g/L, temperature 180 °C and time 30.3 min. Biogas production was increased by 169.5% after pretreatment at RSM optimised conditions as compared with untreated OFMSW.

Effect of substituting organic fraction of municipal solid waste with fruit and vegetable wastes on anaerobic digestion

The potential of replacing fruit and vegetable wastes (FVW) as remarkable sources of environmentally offensive biomass in metropolises with organic fraction of municipal solid waste (OFMSW) on biogas production was investigated. Components of OFMSW as a source separated MSW were prepared in 5 categories of fat and protein, starch, cellulose, fruit, and vegetable waste. Experiments were carried out in four FVW/OFMSW replacement ratios (wet basis) of 0, 15, 30 and 45% at two total solid (TS) concentrations of 8% and 15% at 37 °C. Main results indicated that co-digestion is favorable at lower TS content (8% TS) and higher FVW/OFMSW ratios up to 30%. Although methane yield did not improve significantly for these substitution ratios, the concentration of methane in the biogas enhanced up to 68% and about 92% of volatile solids’ removal achieved. Kinetics study, based on lag phase of Gompetz model, indicated process rapidity increased proportionally to the FVW replacement ratios. Dedication up to 30% of feedstock capacity of ongoing OFMSW biogas plants in metropolises with FVW can suggest more revenue for plants through lowering HRT, increasing biodegradability of substrate, removing undesirable gas and supplying water needed for anaerobic digestion.

Anaerobic co-digestion of municipal solid wastes with giant reed under mesophilic conditions

Anaerobic co-digestion of mixed feedstocks improves the biogas yields due to a better balance of nutrients in the digestion medium. A suitable choice for improving biogas yields from the anaerobic digestion of municipal solid wastes is the co-digestion with lignocellulosic materials. The growing exploitation of the giant reed in several industrial fields motivated a preliminary investigation on the anaerobic co-digestion of steam-exploded giant reed and the organic fraction of municipal solid wastes (OFMSW).The anaerobic digestion was carried out at 37 °C, in batch operation mode. Biogas volumes produced and the concentration–time profiles of volatile fatty acids were analysed for different initial ratios of the mixed feedstock. All the mixtures performed better than the single feedstock. The optimal biogas yield was obtained with the co-digestion of a mixture containing 75% OFMSW and 25% giant reed, which produced 236 mL CH4/g VS with a 1.5-fold increase respect to the digestion of OFMSW alone.

Microbial Profile of the Leachate from Mexico City’s Bordo Poniente Composting Plant: An Inoculum to Digest Organic Waste

In recent years, municipal solid waste (MSW) management has become a complex problem worldwide. Similarly, Mexico City is facing such a situation for the management and treatment of organic fraction of municipal solid waste (OFMSW). Therefore, in this work, we investigated whether leachate from the composting plant, Bordo Poniente, located in Mexico City can be used as an inoculum for the treatment of OFMSW using thermophilic anaerobic digestion (AD) with a hydraulic retention time of 30 days. We analyzed the physicochemical properties of the leachate and performed a biochemical methane potential test. Archaeal and bacterial diversity was also identified using high throughput DNA sequencing of 16S rDNA libraries. Methane yield was 0.29 m3 CH4/kg VSadded in the positive control and 0.16 m3 CH4/kg VSadded in the treatment group. The phylum, Bacteroidetes, and genus, Methanosarcina, prevailed in the leachate. However, in thermophilic conditions, the microbial communities changed, and the phylum, Firmicutes, genera, Methanoculleus, and candidate genus, vadinCA11, were dominant in the treatment group. We concluded that the leachate contains a suitable initial charge of many active bacteria and methanogenic archaea which contribute to the AD process, hence it can be used as an inoculum for the treatment of OFMSW.

Reactor performance and economic evaluation of singular, binary, and ternary mixing of feedstocks for anaerobic digestion

ABSTRACT This study compared the performance of singular, binary, and ternary mixing of feedstocks for anaerobic digestion. Three wastes, including organic fraction of municipal solid waste (OFMSW), dairy manure, and corn stover, were tested under the mesophilic condition. Results showed that the binary and ternary mixing stabilised digesters while solely processing OFMSW resulted in pH drop and over accumulation of volatile fatty acids. The highest methane yield of 302.3 L/kg-VS was achieved with 50% OFMSW, 33% corn stover, and 17% dairy manure, which was about 5 times of that obtained from digesting OFMSW alone. The binary and ternary mixing led to multiple peaks in daily methane production, which evened out methane production throughout the 50-day digestion process. Economic analysis showed that solid digestate price, direct fixed capital cost, and labour cost significantly affected net present value (NPV). Ternary mixtures had the highest NPV and internal rate of return and were financially attractive under analysis conditions.

Pilot-Scale Polyhydroxyalkanoate Production from Combined Treatment of Organic Fraction of Municipal Solid Waste and Sewage Sludge

Although the organic fraction of municipal solid waste (OFMSW) and sewage sludge (SS) originate from the same urban area and contain similar organic matter, they are collected separately and handle...

Assessing the organic fraction of municipal solid wastes for the production of lactic acid

With an estimated yearly production of about 140 Mt in the EU, conventionally, the organic fraction of municipal solid wastes (OFMSW) has been disposed in landfills with negative environmental effects. Nonetheless, the chemical composition of this residue make it a substrate with great bioconversion potential. In this study, OFMSW from Spanish municipal treatment plants, were evaluated for the production of LA. Samples were identified according to the sorting mechanisms employed for their collection in: (A) separately collected, (B) non-separately collected and (C) separately collected+paper/cardboard. Enzymatic hydrolysis was used to produce hydrolysates A, B and C accordingly. Hydrolysate A showed the highest total sugars and glucose content with values of 70 and 55 g·L−1, respectively. Following the characterisation, a screening showed that growth of B. coagulans was possible in all three hydrolysates. Furthermore, lab scale fermentations showed that LA final concentrations could reach around 60 g·L−1, with yields from total sugars of above 0.60 g·g−1. A technical scale fermentation of the hydrolysate A resulted in a final LA concentration of 60.7 g·L−1, a yield of 0.71 g·g−1 with a productivity of 2.68 g·L−1·h−1. Overall, it was estimated that 0.23 g of LA could be produced from one g of dry OFMSW.

Organic fraction of municipal solid waste conversion into polyhydroxyalkanoates (PHA) in a pilot scale anaerobic/aerobic process

In recent years, the attention to organic wastes as a new feedstock for the production of PHA is increased based on the idea that this is the only way to reduce their high cost and to increase their sustainability. For this reason, a pilot platform has been designed to produce PHA from the source-sorted organic fraction of municipal solid waste (OFMSW). The cost-effective system consists in the three-steps anaerobic-aerobic process: the fermentation step was performed in a 200 L CSTR (OLR 20.0 kgVS/m3.d, HRT 3.3 d) in thermophilic conditions (55°C). The VFA-rich mixture was used for the two following aerobic steps: a first sequencing batch reactor (SBR, 100 L) for the production of functionalized PHA-producing biomass (mixed consortium, MMC), and a second batch reactor (50 L) for production of PHA and its maximization inside cell walls. The SBR was operated at 1.2-2.5 kgCOD/m3.d as OLR, and HRT of 1 d (equal to SRT); dynamic feeding regime (feast-famine) was used for consortium selection.The fermentation conditions allowed obtaining a significant COD conversion into VFA. Acetic, propionic and butyric acids accounted for more than 80% of total VFA and the relative yield was 0.45 ± 0.03 CODVFA/VS. The necessary buffering capacity was provided by anaerobic digestate addition, which increased the system alkalinity (2.8 ± 0.2 gCaCO3/L at pH 5.75). In SBR, a strong selective pressure favouring PHA-accumulating organisms was easily reached, as demonstrated by the short feast-to-cycle length ratio (often below 0.12). In the second aerobic accumulation reactor, the biomass was able to accumulate up to 49% gPHA/gVSS. Both aerobic steps were performed without temperature (T) control, avoiding additional consumption of energy; the applied OLR was chosen based on biomass kinetic in order to have a constantly short feast phase and a stable selection/enrichment of PHA-accumulating consortium.

Perfluoroalkyl Acid Characterization in U.S. Municipal Organic Solid Waste Composts

Composting the organic fraction of municipal solid waste (OFMSW) creates a nutrient rich soil amendment and reduces the amounts of wastes going to landfills or incineration. However, the occurrence...

Waste-to-Resource Transformation: Gradient Boosting Modeling for Organic Fraction Municipal Solid Waste Projection

Food and garden waste are important components of organic fraction municipal solid waste (OFMSW), representing carbon and nutrient rich resources composed of carbohydrates, lipid, protein, cellulos...

Volatile fatty acid production from mesophilic acidogenic fermentation of organic fraction of municipal solid waste and food waste under acidic and alkaline pH

This study is focused on the effects of pH on the production of volatile fatty acids (VFAs) and their distribution through the acidogenic fermentation of source-sorted organic fraction of municipal solid waste (OFMSW) from a mechanical-biological treatment (MBT) plant, and food waste (FW) from a university canteen. In semi-continuous lab-scale digesters using OFMSW at a hydraulic retention time (HRT) of 3.5 days under acidic conditions (pH 6.0), the VFA concentration in the effluent increased to 9.8–11.5 g L−1 (VS content of the feedstock between 4.2 and 5.2% w/w), while its individual VFA profiling was similar to the influent which was already pre-fermented (namely, C2 35–41%, C3 18–22%, C4 17–21%, and C5 9–12%). When working with the same conditions but using FW as feedstock, an effluent with a VFA concentration up to 11.5 g VFA L−1 (FW with a VS content of 5.5% w/w) and a stable distribution of C2 and C4 acids (up to 60.3% and 12.9%, respectively) but with very low quantities of C3 and C5 acids (lower than 1.8 and 2.7%, respectively) was obtained. Anaerobic batch tests using FW revealed that alkaline pH near 9 could lead to higher VFA production with high acetic acid content when compared to pH 6. In the semi-continuous fermenters working at alkaline conditions (pH 9.5–10) using OFMSW and FW, an enhanced solubilization of organic matter was registered with respect to the fermenters working under acidic conditions. This fact was not reflected in a higher VFA production when using OFMSW as feedstock, probably due to free ammonia inhibition, since OFMSW was mixed in the MBT plant with supernatant from anaerobic digestion of this biowaste. However, when using FW, alkaline conditions lead to an enhanced VFA production with respect to the reactor working under acidic conditions, being acetic acid the predominant product, which represented up to 91% of the VFA spectrum obtained.

Fe0 inhibits bio-foam generating in anaerobic digestion reactor under conditions of organic shock loading and re-startup

Bio-foaming during the anaerobic digestion (AD) of the organic fraction of municipal solid waste (OFMSW) is a major cause of unstable reactor operations, especially under high organic loading rates (OLRs). Here, we used two 40-liter anaerobic reactors to deal with the actual organic fraction of municipal solid waste at OLRs of 5 and 7.5 kgVS/m3/d and tried to inhibit bio-foam generation by dosing with Fe0. One of reactors had 400 g of Fe0 added before operation and additional 200 g of Fe0 was added when the operating conditions changed; the other one was the control reactor with no Fe0 dosing. The results show that bio-foam was generated in the control reactor at an organic shock loading of 10 kgVS/m3/d and re-startup at 5 kgVS/m3/d, while the reactor containing Fe0 operated normally. Due to the surfactant attributes of volatile fatty acids (VFAs), the probability of bio-foam generation was positively correlated with the effluent’s degree of surface activity (SA) induced by VFAs, which is a parameter representing the foaming potential. Because VFA biodegradation was enhanced in the reactor with added Fe0, at the position of Fe0 accumulation, the SA was decreased by 49.7–59.2%. Furthermore, the effect of Fe0 dosing on inhibiting bio-foam was evaluated by comparison with traditional commercial anti-foam agents. The results suggest possible reasons for bio-foam generation in OFMSW AD and suggest the reasonable usage of Fe0 to inhibit bio-foam formation.

Liquid biofuels from the organic fraction of municipal solid waste: A review

The valorisation of the organic fraction of municipal solid waste (OFMSW) in the circular economy context is of outmost importance. This review aimed to examine the state-of-the-art valorisation technologies of OFMSW as resource for bioethanol and biodiesel. Firstly, feedstock mapping was performed, where high fluctuation of parameters was revealed. Considering the mean values, the stoichiometries of mechanically and source-sorted OFMSW are C22H44O28N and C20H36O16N, respectively. The substrate's mean carbohydrates (50%) and lipids (13%) contents reflect its potential in bioethanol and biodiesel production, respectively. As far as bioethanol is concerned, this paper critically reviewed the existing variance of second-generation bioethanol production methodologies from OFMSW revealing that high bioethanol yields (over 80%) could be achieved if the treatment steps of pretreatment, enzymatic hydrolysis and fermentation are synergistically compiled. To this end, bioethanol yield could benefit from suitable enzymatic blends. Furthermore, this paper discussed about different ways of oil extraction from OFMSW and various biodiesel production techniques. Soxhlet extraction combined with alkaline transesterification emerged as the most widely applied biodiesel production line from OFMSW. The novelty of this literature review lies in the integration of both bioethanol and biodiesel production processes, in a biorefinery concept that would allow the production of both biofuels along with that of biogas. This integration scenario rendered an energy efficiency expressed as energy content in products per energy in raw materials equal to 68%, proving that OFMSW is a feedstock that could meet the sustainability criteria for biofuels production.

Acclimatization contributes to stable anaerobic digestion of organic fraction of municipal solid waste under extreme ammonia levels: Focusing on microbial community dynamics

The organic fraction of municipal solid waste (OFMSW) is an abundant and sustainable substrate for the anaerobic digestion (AD) process, yet ammonia released during OFMSW hydrolysis could result in suboptimal biogas production. Acclimatized ammonia tolerant microorganisms offer an efficient way to alleviate ammonia inhibition during AD. This study aimed to achieve an efficient AD of OFMSW under extreme ammonia levels and elucidate the dynamics of the acclimatized microbial community. Thus, two mesophilic continuous stirred tank reactors (CSTR), fed only with OFMSW, were successfully acclimatized up to 8.5 g NH4+-N/L, and their methane yields fluctuated <10%, compared to the methane yields without ammonia addition. Microbiological analyses showed that Methanosaeta concilii and Methanosarcina soligelidi were the dominant methanogens at low and high ammonia levels, respectively. Whilst, a unique metabolic pathway shift, from aceticlastic to hydrogenotrophic methanogenesis, of M. soligelidi was identified during the acclimatization process.

LCA-Based Comparison of Two Organic Fraction Municipal Solid Waste Collection Systems in Historical Centres in Spain

Municipal solid waste (MSW) collection is an important issue in the development and management of smart cities, having a significant influence on environmental sustainability. Door-to-door and pneumatic collection are two systems that represent a way of arranging waste collection in city´s historic areas in Spain where conventional street-side container collection is not feasible. Since door-to-door collection generates significant direct greenhouse gas emissions from trucks, pneumatic collection emerges as an alternative to the trucking system. While this technology apparently reduces local direct air emissions, it suffers from a large energy demand derived from vacuum production for waste suction. The introduction of new normative frameworks regarding the selective collection of the biodegradable fraction makes necessary a comprehensive analysis to assess the influence of this fraction collection and its subsequent recycling by anaerobic digestion. As a novelty, this work compares both conventional door-to-door and pneumatic collection systems from a life cycle approach focusing on the biodegradable waste. Results indicate that, in spite of the fact electricity production and consumption have a significant influence on the results, the energy savings from the recycling of the organic fraction are higher than the energy requirements. Therefore, the pneumatic collection could be an environmentally-friendly option for MSW management under a circular economy approach in Spanish city´s historic areas, since wastes could be a material or energy source opportunity.

Integrated anaerobic codigestion system for the organic fraction of municipal solid waste and sewage sludge treatment: an Italian case study

AbstractBackgroundThe production of the organic fraction of municipal solid waste (OFMSW) is growing continuously and is often directed to composting, an energy‐consuming approach. This study evaluates the advantages of an integrated treatment of waste and wastewater with the application of anaerobic codigestion technology.ResultsThe anaerobic codigestion process was monitored for 24 months in a full‐scale plant with a 2000 m3 digester. Steady‐state conditions were reached with an average biogas production of 1629 m3 day−1 and a specific gas production of 0.51 m3 kgVS−1 in mesophilic temperature range (37 °C). Electric energy coverage was equal to 49%, with a specific revenue calculated equal to 81.7 €/tOFMSW.ConclusionsIt was demonstrated that this technology is convenient from environmental, territorial and economic points of view. The territorial approach of organic waste treatment can be directed into more energy or matter recovery. In both cases this process is applicable and can allow waste valorization through energy production without costly investments. © 2019 Society of Chemical Industry

Effect of Leachate Spraying Intensity on High-Solid Anaerobic Digestion of Corn Stover and Organic Fraction of Municipal Solid Waste

The effects of leachate spraying intensity (LSI, the ratio of leachate spraying rate and spraying area) on high-solid anaerobic digestion (HS-AD) of corn stover (CS) and organic fraction of municipal solid waste (OFMSW) were investigated for the first time. Three leach-bed reactors (LBR) with working volume of 48 L were used in this study. Gaseous parameters including CH4, H2 and CO2 concentration, and liquid parameters including pH, volatile fatty acid (VFA) and total inorganic carbon (TIC), were measured. Results found that LSI could significant influence the methane yield from HS-AD of CS and OFMSW. Higher LSI of 88 mL/min dm2 could enhance the degradation rate of feedstocks, with highest VFA concentration of 21273 mg/L using liquid sludge as inoculum. Consequently, the methanogenesis was inhibited. Incubation of solid digestate (50% of solid digestate + 50 of liquid sludge) can be operated stably at higher LSI of 88 mL/min dm2, where highest methane yield of 184.6 mL/g VS was obtained. The finding of this study could provide useful information for the efficient operation of HS-AD.