Digestion Of Solid Waste Research Articles

Review on Anaerobic Digestion and Disposal Technology of Solid Waste

This paper reviews the solid waste disposal technologies at home and abroad. Solid waste is rich in a large amount of organic matter. If discarded or landfilled, it will cause serious environmental problems such as greenhouse gas emissions, landfill leachate emissions, pathogen transmission and groundwater pollution. Common disposal methods of solid waste include sanitary landfill, incineration, compost fermentation, anaerobic digestion, etc. Among them, anaerobic digestion technology is an economical and efficient solid biological treatment technology, which can not only realize the degradation of organic matter components in solid waste and the removal of toxic and harmful pollutants, but also obtain biogas to realize energy recovery.

Review on solid-state anaerobic digestion of lignocellulosic biomass and organic solid waste.

Sustainable management of organic solid wastes especially the municipal solid waste (MSW) is essential for the realization of various sustainable development goals (SDGs). Resource recovery centric waste processing technologies generate valorizable products to meet the operations and maintenance (O&M) costs while reducing the GHG emissions. Solid-state anaerobic digestion (SSAD) of organic solid wastes is a biomethanation process performed at a relatively higher total solids (TS) loading in the range of 10-45%. SSAD overcomes various limitations posed by conventional anaerobic slurry digesters such as higher degradable matter per unit volume of the bioreactor resulting in a smaller footprint, low freshwater consumption, low wastewater generation, simple upstream and downstream processes, relatively lower operation, and maintenance costs. This review elucidates the recent developments and critical assessment of different aspects of SSAD, such as bioreactor design, operational strategy, process performances, mass balance, microbial ecology, applications, and mathematical models. A critical assessment revealed that the operating scale of SSAD varies between 1000 and 100,000 ts/year at organic loading rate (OLR) of 2-15g volatile solids (VS)/L·day. The SSAD experiences process failures due to the formation of volatile fatty acids (VFAs), biogas pockets and clogging of the digestate outlet. Acclimatization of microbes accelerates the startup phase, steady-state performances, and the enrichment of syntrophic microbes with 10-50 times greater population of cellulolytic and xylanolytic microbes in thermophilic SSAD over mesophilic SSAD. Experimental limitations in the accurate determination of rate constants and the oversimplification of biochemical reactions result in an inaccurate prediction by the models.

Effect of the mixing ratio on the composting of OFMSW digestate: assessment of compost quality

This study presents the results obtained in compostability tests of organic fraction of municipal solid waste (OFMSW) digestate. The final aim was to obtain mature compost without phytotoxic effects. For the evaluation of the composting process, a novel parameter describing the performance of the composting process, the relative heat generation standardized with the initial volatile solid content (RHGVS0), was defined and evaluated at laboratory-scale. From these laboratory-scale test, the optimum operational conditions were obtained, a mixing ratio (v/v) of 1:1:0 (bulking agent:digestate:co-substrate) and with 15% of mature compost as inoculum. Subsequently, these optimum operational conditions were applied in the active phase of the composting pilot-scale reactor. The active composting stage took 7 days, subsequently a curing phase of 60 days was carried out at ambient conditions. After 30 days of curing, the mature compost showed a specific oxygen uptake rate (SOUR) of 0.14 mg O2/g VS·h, a germination index (GI) of 99.63% and a low volatile fatty acids (VFA) concentration (41.3 AcH mg/kgdm), being indicative of the good compost stability and maturity of the compost. The very good quality of the final compost obtained indicated that the RHGVS0 accurately describes the performance of the composting process.

Determining the appropriate mixing ratio in a multi-substrate anaerobic digestion of organic solid wastes employing Taguchi method.

The current research proposed a method for optimally combining feed input ratios in order to improve the quantity and quality of daily biogas production through optimizing the variable response level in the Taguchi method. The anaerobic digestion (AD) process of an existing plant in Iran was simulated through a set of two-stage pilot reactors under mesophilic temperature conditions in order to achieve optimal operational performance. Three common substrates (organic fraction of municipal solid wastes, fruit and vegetable wastes, and horse manure) along with two recirculated materials; the post-digestion sludge and the secondary digester slurry, were investigated in 16 experimental runs based on four different pre-surface hypotheses. Comparison of the results of daily biogas energy (J/d/g-VS) in Run#9, to which the actual yield of hydrogen sulfide was minimal in parallel to a methane yield above 100 mL/g-VS, with the result of the optimal run with the ratios provided by the model, showed that the daily biogas energy was improved by 50% comparing to the control Run that had similar conditions to which was being applied in the full-scale existing AD plant.

Composting food waste or digestate? Characteristics, statistical and life cycle assessment study based on an Italian composting plant

Agricultural use of food waste compost is the natural way to return nutrients to the soil. In application of the European waste hierarchy, the recovery of nutrients from food waste through composting is a more preferable option than incineration or disposal. Two different inputs are generally used for industrial composting processes: food waste as it is or digestate resulting from the anaerobic digestion of food waste. In this study, a life cycle assessment (LCA) analysis was performed for the production of compost from both organic fraction of municipal solid waste (OFMSW) and OFMSW-based digestate, processed by an Italian composting plant. The environmental footprint of the production of the two types of compost was determined by quantifying 19 impact categories. The treatment of OFMSW through anaerobic digestion prior to composting resulted more beneficial to the environment than direct composting of the feedstock. Indeed, OFMSW compost showed greater environmental impacts than digestate compost for 17 out of 19 categories. Savings were measured in 18 and 10 impact categories for digestate and OFMSW compost, respectively. In particular, for the climate change category, a total net saving of −12 kg and −434 kg of CO2 equivalent was measured for the production of 1 Mg of OFMSW and digestate compost, respectively. The reported results were obtained using only real plant data and compared with various literature LCA analyses. The chemical-physical characteristics of the two types of compost were also compared and subjected to principal component analysis.

Digestion and recovery of household waste (food) into biogas: The case study Ouargla city in Sahara- Algeria

The recycling of household waste through the anaerobic digestion of solid household waste into biogas represents one of the current topics that address the issues and environmental sustainability: renewable energy, depollution in urban ecology, methanogens in green chemistry. In this research, this contribution deals with the experimental digestion of household food waste (HFW) and vegetable, fruit and garden waste (VFG), using a chemical reactors, in order to evaluate the effect of temperature in the different phases, of 25oC, 35oC, 45oC, 55oC, and 65oC, at different Dry/humidity ratios: 40%, 50%, and 60%, on the production rate of biogas, in the food waste of the inhabitants of the city of Ouargla in Sahara (Algeria) (presentational sampling in terms of the amount of protein-rich and fatty food waste, and the ambient temperature). The result of research revealed that (under high temperature and wetting conditions) show the impact of the proteins and fats in the food waste on the high amount of biogas emitted (100% augmented) compared to the vegetable, fruit and garden waste.

Energy recovery technologies from municipal solid waste: enhancing solid waste Brazilian policy

Public incentives play an important role in expanding the possibilities of using renewable energies, such as that generated from MSW (municipal solid waste) biomass, not only creating opportunities, but also several challenges. Thus, from the literature review, this paper aims to describe the feasibility (technical, economic, and environmental), potentialities, obstacles and readiness level of the technologies of energy generation from municipal solid waste. These technologies include the use of landfill gas, biogas generated by anaerobic digestion and direct burning of solid waste (incineration). Between the three technologies, landfill gas has greater economic viability, anaerobic digestion is classified as the most environmentally viable energy recovery technology, while incineration has the highest energy recovery potential. Regarding the readiness level of the technologies, incineration and anaerobic digestion are extensively used in Europe, United States and East Asia, while landfill gas is used extensively in the United States, Latin America and India. Moreover, the applicability of a technology should always have a set of factors into consideration (economic, environmental and technical), to be applied to local characteristics, in conjunction to other technologies.

Integration of hydrothermal carbonization treatment for water and energy recovery from organic fraction of municipal solid waste digestate

Anaerobic digestion is an efficient way of using a wet fraction of municipal solid waste (MSW) for energy purposes as it can produce biogas. The moisture content of the digestate after application of mechanical dewatering is still high, and the amount of heat needed for drying is significant. Hydrothermal carbonization (HTC) is a process that can potentially offer great benefits by improved mechanical dewatering and valorization of the digestate into a better quality solid fuel. This study focuses on the determination of the optimum HTC process conditions to recover water from the MSW digestate. Different process conditions as temperature (180, 200, and 230 °C) and residence time (30, 60, and 120 min) were tested. Furthermore, a mass and energy balance was carried out and a process model in Aspen Plus was built. Results showed that HTC treatment increased the water recovery (40–48%) during the dewatering process compared with the original feedstock (18%). The process model showed a positive energy balance of 110 kWh per ton of MSW digestate treated with an electrical efficiency of 23.9%.

Microorganisms in the typical anaerobic digestion system of organic solid wastes: a review

The facultative anaerobic and strict anaerobic microorganisms enriched and acclimated during the anaerobic digestion process are crucial for the efficiency of the anaerobic digestion system. Most of the problems encountered during running anaerobic digestion processes could be effectively improved via stimulation of microbial metabolic activity. Benefited from the rapid development of microbiome techniques, deeper insights into the microbial diversity in anaerobic digestion systems, e.g. the microbe-microbe interactions and microbe-environment interactions, have been gained. A complex and intricate metabolic network exists in the anaerobic digestion system of solid organic wastes. However, little is known about these interactions and the underlying mechanisms. This review briefly summarized the representative interactions between microbial communities during anaerobic digestion process discovered to date. In addition, typical issues encountered during the anaerobic digestion of solid organic wastes and how microbes can tackle and alleviate these issues were discussed. Finally, future priorities on microbiome research were proposed based on present contribution of microbiome analysis in anaerobic digestion system.

Batch and Semi-Continuous Anaerobic Digestion of Industrial Solid Citrus Waste for the Production of Bioenergy

The aim of this paper is to describe a study of the anaerobic digestion of industrial citrus solid waste (ISCW) in both batch and semi-continuous modes for the production of bioenergy without the elimination of D-limonene. The study was conducted at the pilot plant level in an anaerobic reactor with a working volume of 220 L under mesophilic conditions of 35 ± 2 °C. Cattle manure (CM) was used as the inoculum. Three batches were studied. The first batch had a CM/ISCW ratio of 90/10, and Batches 2 and 3 had CM/ISCW ratios of 80/20 and 70/30, respectively. In the semi-continuous mode an OLR of approximately 8 g total chemical oxygen demand (COD)/Ld (4.43 gVS/Ld) was used. The results showed that 49%, 44%, and 60% of volatile solids were removed in the batch mode, and 35% was removed in the semi-continuous mode. In the batch mode, 0.322, 0.382, and 0.316 LCH4 were obtained at STP/gVSremoved. A total of 24.4 L/d (34% methane) was measured in the semi-continuous mode. Bioenergy potentials of 3.97, 5.66, and 8.79 kWh were obtained for the respective batches, and 0.09 kWh was calculated in the semi-continuous mode. The citrus industry could produce 37 GWh per season. A ton of processed oranges has a bioenergy potential of 162 kWh, which is equivalent to 49 kWh of available electricity ($3.90).

Biochemical potential evaluation and kinetic modeling of methane production from six agro-industrial wastewaters in mixed culture.

Methane (CH4) production from anaerobic digestion of solid and liquid agro-industrial wastes is an attractive strategy to meet the growing need for renewable energy sources and promote environmentally appropriate disposal of organic wastes. This work aimed at determining the CH4 production potential of six agro-industrial wastewaters (AWW), evaluating the most promising for methanization purposes. It also aims to provide kinetic parameters and stoichiometric coefficients of CH4 production and define which kinetic models are most suitable for simulating the CH4 production of the evaluated substrates. The AWW studied were swine wastewater (SW), slaughterhouse wastewater (SHW), dairy wastewater (DW), brewery wastewater (BW), fruit processing wastewater (FPW), and residual glycerol (RG) of biodiesel production. RG was the substrate that showed the highest methanization potential. Exponential kinetic models can be efficiently applied for describing CH4 production of more soluble substrates. On the other hand, logistic models were more suitable to predict the CH4 production of more complex substrates.

Preparation of calcium ferrite by flue gas desulfurization gypsum

At present, the continuous accumulation of the flue gas desulfurization (FGD) gypsum in steel plants leads to the serious environmental issues and resource waste. To achieve green and sustainable development for the steel industry, it is significant to improve the usage of by-product gypsum. Employing the sintering FGD gypsum, ferric oxide, and graphite carbon as raw materials, the effects of the carbon content, reaction time, and molar ratio of CaO to Fe2O3 on the desulfurization rate of gypsum were studied based on the orthogonal experiment. The results show that the order of the three influencing factors on the desulfurization rate of FGD gypsum is: molar ratio of CaO to Fe2O3 > reaction time > carbon content. Under the optimal conditions of 20 wt.% carbon content, 4 h reaction time, and 1:1 molar ratio of CaO to Fe2O3, the desulfurization rate of desulfurization gypsum is 95.79%, and 97.57 wt.% of calcium ferrite appears in the solid product, which can be used as sintering additive to increase the economic benefits of enterprises and realize the green ecological development mode of internal generation and internal digestion of solid waste in iron and steel enterprises.

Surrogate based Global Sensitivity Analysis of ADM1-based Anaerobic Digestion Model

In order to calibrate the model parameters, Sensitivity Analysis routines are mandatory to rank the parameters by their relevance and fix to nominal values the least influential factors. Despite the high number of works based on ADM1, very few are related to sensitivity analysis. In this study Global Sensitivity Analysis (GSA) and Uncertainty Quantification (UQ) for an ADM1-based Anaerobic Digestion Model have been performed. The modified version of ADM-based model selected in this study was presented by Esposito and co-authors in 2013. Unlike the first version of ADM1, focused on sewage sludge degradation, the model of Esposito is focused on organic fraction of municipal solid waste digestion. It his recalled that in many applications the hydrolysis is considered the bottleneck of the overall anaerobic digestion process when the input substrate is constituted of complex organic matter. In Esposito's model a surfaced based kinetic approach for the disintegration of complex organic matter is introduced. This approach allows to better model the disintegration step taking into account the effect of particle size distribution on the digestion process. This model needs thus GSA and UQ to pave the way for further improvements and reach a deep understanding of the main processes and leading input factors. Due to the large number of parameters to be analyzed a first preliminary screening analysis, with the Morris' Method, has been conducted. Since two quantities of interest (QoI) have been considered, the initial screening has been performed twice, obtaining two set of parameters containing the most influential factors in determining the value of each QoI. A surrogate of ADM1 model has been defined making use of the two defined quantities of interest. The output results from the surrogate model have been analyzed with Sobol’ indices for the quantitative GSA. Finally, uncertainty quantification has been performed. By adopting kernel smoothing techniques, the Probability Density Functions of each quantity of interest have been defined.

Performance of Semi-dry Anaerobic Digestion of Organic Solid Waste in Mesophilic Continuous Operation

Performance of Semi-dry Anaerobic Digestion of Organic Solid Waste in Mesophilic Continuous Operation

Thermal pre-treatment as a tool for energy recovery from food waste through anaerobic digestion. Effect on kinetic and physicochemical characteristics of the substrate

Hydrolysis is the rate limiting stage in the anaerobic digestion (AD) of solid waste, such as food waste (FW), due to the presence of lignocellulosic material, which affects methane production. Mitigation strategies, such as thermal pre-treatment of the substrate, can be used to accelerate hydrolysis. In this study, the influence of temperature (72–128 °C) and exposure time (15–33 min) on the physicochemical properties of the substrate, biochemical methane potential (BMP) hydrolysis, the balance of organic matter (as measured by the chemical oxygen demand (COD)), and net energy production were determined. In terms of the substrate, positive results were obtained: a 50% reduction in lignin; up to a 34% increase in hemicellulose; up to a 99% reduction in Fe, Mn, Cu and Zn; an 83% decrease in Mg; and a 150% increase in K. In addition, methane production was higher than for the untreated substrate (120 vs 90 mLCH 4 ⋅ gVS −1 ). The modified first-order kinetic model and adjusted Gompertz model, showed that the pre-treatment reduced the lag-phase (by less than 1 d), and increased the hydrolysis constant to above 40%. The optimal pre-treatment condition was approximately 72 °C-22 min, promoted hydrolysis, increased the COD soluble and produced a positive energy balance (7821.07 kJ). • Trace elements present in FW are reduced by over 50% since these are transition metals. • Lignin and hemicellulose are either reduced or increased according to the pre-treatment. • The Maillard reaction can both, consume alkalinity and inhibit AD. • The thermal pre-treatment presents a positive balance of 2.2 kWh⋅kgVS substrate -1 .

Evolution of control parameters in biochemical methane potential tests of olive mill solid waste (OMSW), thermal pre-treated OMSW, and its co-digestion with Dunaliella salina

The aim of the present work was to compare the mesophilic anaerobic digestion of untreated olive mill solid waste (OMSW), soft hydrothermal pre-treated OMSW (SHP OMSW), and a co-digestion mixture of 95% OMSW and 5% microalga Dunaliella salina (co-OMSW). During the co-digestion experiment, the volatile fatty acid accumulation decreased in comparison with that obtained for OMSW and SHP OMSW, reducing the slight inhibition observed during the OMSW and SHP OMSW experiments. Final values of methane yield of 380 ± 1 mL CH4 g−1 VSadded for the OMSW, 424 ± 2 mL CH4 g−1 VSadded for the SHP OMSW, and 491 ± 1 mL CH4 g−1 VSadded for the co-OMSW were determined. Two mathematical models, first-order kinetics and modified Gompertz model, were employed to fit the experimental data with the aim of elucidating the anaerobic biodegradation and obtain the kinetic constants. Both models allowed for adequately fitting the experimental results of methane production with time. The kinetic constant, k, of the first-order model increased by 12% for the co-OMSW compared with the values achieved for OMSW and SHP OMSW. The modified Gompertz model revealed that the maximum methane production rate, Rm, for the co-OMSW and SHP OMSW increased by 34.7% and 10.3% compared with the value obtained for OMSW.

Evaluation of Chlorella vulgaris and Scenedesmus obliquus growth on pretreated organic solid waste digestate

In this research Scenedesmus obliquus and Chlorella vulgaris growth was tested on digestate sludge obtained from the anaerobic co-digestion treatment of the organic fraction of municipal solid waste (OFMSW) together with waste activated sludge (WAS). Digestate was diluted 1:10 and tested in three batch experimental conditions: with no pre-treatments (noPT), after centrifugation (AC) and after filtration (AUF), in order to evaluate microalgae limiting growth factors. The best growth was obtained by C. vulgaris on digestate AC compared to S. obliquus, reaching 479 ± 31 cell million ml−1 and 131 ± 12 cell million ml−1 respectively. Ammonia removal evaluated in C. vulgaris and S. obliquus cultures was 99.2% ± 0.3 and 98.146% ± 0.008 in AC condition, respectively. Considering that AUF showed similar microalgae growth values, the digestate pretreatment for microalgae growth, could be limited to centrifugation.

One-step acquirement of superior microbial communities from mesophilic digested sludge to upgrade anaerobic digestion

Anaerobic digestion is a promising waste-to-energy alternative technology. However, the efficiency upgrading for conventional mesophilic digestion of organic solid waste is always indispensable. Employing hyperthermophilic or thermophilic microbial community is one of the viable upgrading alternatives. Given the unavailability of the superior microbial communities, mesophilic digested sludge was used as inoculum, and instantly controlled at 70 °C and 55 °C for acclimation of hyperthermophilic and thermophilic inocula, respectively. Waste activated sludge was continuously and synchronously fed into two digesters. After one round, thermophilic digester achieved stable biogas production rate at 0.22 L L−1 d−1, with a methane proportion over 60%, whereas fluctuation was observed in the hyperthermophilic digester, and approximately triple time was needed to reach a relatively stable biogas production rate 0.12 L L−1 d−1. Nevertheless, higher hydrolysis ratio 24.4% was observed in the hyperthermophilic digester despite the lower biogas production. Therefore, methanogenesis step limited the whole anaerobic process for the hyperthermophilic digestion, and digestion at 70 °C was appropriate as a pre-fermentation stage to enhanced hydrolysis. The genus Methanothrix proportion in the thermophilic digester gradually decreased, while another acetoclastic genus Methanosarcina ultimately was acclimated to the dominant methanogen. In addition to Methanothrix, hydrogenotrophic archaea became competitive in the hyperthermophilic digester, with Methanothermobacter dominant at 22.6%. The genus Psychrobacter, affiliated to the phylum Proteobacteria could survive better than the others at 70 °C, with a final proportion of 62.5%.

Potentiality of municipal sludge for biological gas production at Soba Station South of Khartoum (Sudan)

Potentiality of municipal sludge for biological gas production at Soba Station South of Khartoum (Sudan)

Investigation of Anaerobic Digestion of Organic Solid Waste

The technology of anaerobic digestion of organic solid wastes is, in many aspects, mature. Topics such as fundamentals (kinetics, modeling, etc...) Process aspects performance, two and single phase systems, wet technologies, digestion enhancement of several treatments. Digestion with other substrates and its relation to composting technology are examined in this review. Special attention is paid to the advantages of anaerobic digestion in limiting the emission of greenhouse gases. An overview of industrial achievements and future developments. Municipal solid waste management (MSWM) is one of the major environmental problems of Indian cities. Improper management of municipal solid waste (MSW) causes hazards to inhabitants. Various studies reveal that about 90% of MSW is disposed of unscientifically in open dumps and landfills, creating problems to public health and the environment. In the present study, an attempt has been made to provide a comprehensive review of the characteristics, generation, collection and transportation, disposal and treatment technologies of MSW practiced in India Special attention is paid to the advantages of anaerobic digestion in limiting the emission of greenhouse gases. On overview domestic and organic waste achievement and future development.