Organic Fraction Of Municipal Solid Waste Research Articles

Estimating Circular Economic Potential of Organic Fraction of Municipal Solid Waste in Small City

The current waste management paradigm leads to a circular economic approach. To implement it, it is necessary to know the potential for resource recovery from waste, including organic fraction of municipal solid waste (OFMSW). This research aims to investigate the potential for resource recovery from OFMSW generated in Buleleng Regency, Bali Province, Indonesia. Five technologies were assessed for their potential to transform OFMSW into resources, namely anaerobic decomposition (AD), densification and drying to produce solid fuel, composting, processing with black soldier fly (BSF), and processing for eco-enzymes production. The potential for resource recovery is estimated using a simple linear relationship mathematical model using data available from the literature and secondary data of waste generation in Buleleng Regency. The study estimated 37,489.08 tons OFMSW is generated in Buleleng in 2023. The estimate shows that revenue potential from densification and drying about 9,336 million IDR, followe by composting about 2,471 million IDR, anaerobic digestion about 1,939 million IDR, BSF about 145 million IDR, and eco-enzyme about 13 million IDR. Finally, by estimating the quantity of resources available in OFMSW and their potential market value, it can be taken into consideration in planning and managing the circularity of OFMSW.

Characteristics of the digestates from OFMSW methane production at psychrophilic, mesophilic, and thermophilic conditions under different organic loading rates

ABSTRACT The anaerobic digestion of the organic fraction of municipal solid waste (OFMSW) has shown to be a viable alternative since it allows energy recovery in the form of methane and generates a residue (digestate) that can be applied effectively as a soil improver or fertiliser. The potential for methane production and the digestates’ characteristics depend on the substrate characteristics and the process variables such as temperature, solids retention time, and organic load. This study dealt with OFMSW anaerobic digestion under different organic loading rates and temperatures and the characteristics of the resulting digestates. Three semi-continuous reactors were operated at 20, 35, and 55°C and fed daily with ground, fresh OFMSW from Mexico City. The inoculum was temperature-adapted UASB granular sludge. The main results indicate that the anaerobic digestion was adequate, as the pH values were slightly alkaline, which is sufficient for methanization, and the alkalinity was not a limiting factor. Potassium and PO4-P increased with the organic load, and Kjeldahl nitrogen decreased. At 20°C, total organic carbon (TOC) increased substantially with the organic load; at 35°C, it remained without significant changes; and at 55°C, TOC slightly decreased with the organic load. The C/N ratio changed accordingly to TOC variations. At 20°C, the residual biogas potential increased with the organic load; at 35 and 55°C, it decreased with increasing organic load; the residual biogas potential increased with residual fatty acids concentrations. To comply with international standards for agricultural use, the digestates need only dewatering and supplementing with PO4-P.

Comparative Study of Hydrogen Production from Organic Fraction of Municipal Solid Waste and Its Challenges: A Review

The growing interest in hydrogen production arises from its higher energy density, making it an attractive option for energy storage and fuel applications. However, hydrogen production relies heavily on fossil fuels, producing substantial CO2 emissions. Meanwhile, the organic fraction of municipal solid waste (OFMSW), which constitutes a significant portion of solid waste, predominantly ends up in landfills, leading to methane emissions. Harnessing hydrogen from OFMSW offers an opportunity to offset methane emissions and promote cleaner hydrogen production compared to conventional methods. Various pretreatment methods and production techniques have been explored for hydrogen production from OFMSW, including bio-photolysis, photo-fermentation, microbial electrolysis, and dark fermentation. This study presents a comparative analysis of these methods, evaluating their efficiency, scalability, and potential challenges for hydrogen fuel production from OFMSW. By exploring these avenues, this study found the current hydrogen fuel production scenarios where OFMSW contributes a small portion due to the limited yield. Microbial electrolysis can help to improve the yield and feedstock quality. This study recommends further investigation into the advancement of sustainable hydrogen production and provides insights into overcoming the obstacles associated with this promising field.

Biochar from Digestate Pyrolysis as a Filler for Biopolymer Blends: Effect of Blend Composition

Abstract This study investigates the effect of biochar (BC) as a filler for biopolymer blends, with a focus on the effect of the biopolymer weight ratio on the final BC-added blends. The blends studied in this work were obtained by varying the weight ratio of poly-butylene adipate-co-terephthalate (PBAT) and polylactic acid (PLA) due to their great importance in packaging and agricultural fields. BC has been produced in our laboratories by the slow pyrolysis of the digestate obtained from the anaerobic digestion of the organic fraction of municipal solid waste (OFMSW). After pyrolysis, digestate-derived biochar has been milled and sieved to produce a powdery form with diameter of less than 45 μm. In order to better investigate the filler/polymer interactions, biochar particles were dimensionally, morphologically and chemically characterised. The inhomogeneity of the feedstock is responsible for content and high diversity of inorganics in biochar surface. The effect of BC on PBAT and PLA biopolymer matrices is different, and for the blend compositions the relative weight ratio between PBAT and PLA plays an important role. Furthermore, the biocomposite blend has been fully characterised: rheological, morphological, mechanical and dynamic-mechanical characterisations have been carried out, highlighting how the properties results strongly influenced by the presence of BC in the blend. In addition, a study of the viscous molar mass of the two polymer matrices when processed in the presence or absence of BC particless highlighting that a strong chemical interaction occurs between PLA and BC particles, unlike PBAT and BC. Graphical Abstract

Enhancement of methane production by electrohydrolysis pretreatment for anaerobic digestion of OFMSW

Hydrolysis is the most critical rate-limiting step in the anaerobic digestion (AD) process for most types of substrates. The organic fraction of municipal solid waste (OFMSW) is a rich source for the AD process because of its high degradability. In this study, electrohydrolysis pretreatment was investigated for the OFMSW to overcome the rate-limiting step of hydrolysis. Electrohydrolysis pretreatment was applied to the OFMSW for 30 and 60 min in a custom-made reactor. In the untreated, 30-min. treated, and 60-min. treated OFMSW average methane production was observed as 225 ± 2 mL CH4/g VSadded, 231 ± 4 mL CH4/g VSadded, and 248 ± 7 mL CH4/g VSadded, respectively. By increasing the treatment time, the lag phase, during which hydrolysis occurs, was reduced by 40–43%. 3–10% more methane was produced by applying electrohydrolysis pretreatment. These results suggest that electrohydrolysis pretreatment is a promising method to improve the efficiency of AD for the OFMSW by reducing the time required for hydrolysis and increasing methane production. More investigation is required to better comprehend the effects of electrohydrolysis on the OFMSW.

Process optimization for saccharification and fermentation of the Organic Fraction of Municipal Solid Waste (OFMSW) to maximize ethanol production performance

The Organic Fraction of Municipal Solid Waste (OFMSW) contains paper and cardboard, an attractive cellulosic feedstock for bioethanol production. Waste paper/cardboard (WPC) was subjected to mild acid treatment in solids loadings from 20 to 27.5 %. Different doses of commercial enzyme cocktail and various adjuvants facilitating enzymatic saccharification were tested. Enzyme dosing of 3.75 FPU/g fiber with very slow fed-batch saccharification of 27.5 % (w/v) solids from model lignin-free paper pulp resulted in 12.6 % (w/v) total sugar after 74 h. Use of cheap non-catalytic waste protein adjuvants including Soymeal, Protisyr, Feather meal strongly improved enzymatic saccharification and reduced the overall process cost by reducing commercial enzyme dosing. After fermentation with the industrial yeast strain BMD44 (Cellusec® 1.0) an ethanol titer of 5.77 % (v/v) was obtained using a reduced enzyme loading of 2.5 FPU/g of actual industrial WPC fiber. These results show the potential of economically profitable second-generation bioethanol production with WPC fiber.

Environmental life cycle assessment of polyhydroxyalkanoates production by purple phototrophic bacteria mixed cultures

Bioplastics offer a promising sustainable alternative to petroleum-based plastics due to their biodegradability as well as favourable thermal and mechanical properties. Among different types of biobased polymers, the production of polyhydroxyalkanoates (PHA) using purple phototrophic bacteria (PPB) and low-value substrates has gained increasing interest. Despite the momentum, challenges regarding the scalability and environmental feasibility of this biopolymer production pathway remain. In response, this study employs an exploratory LCA approach to quantitatively assesses the potential environmental implications of PHA production in powder form and the joint management of the organic fraction of municipal solid waste (OFMSW) through a novel photobiorefinery system that uses PPB mixed cultures. Environmental impacts were tested under multiple improvement scenarios and benchmarked against the production of conventional fossil-based granulate or unprocessed plastics, including low density polyethylene (LDPE), polyethylene terephthalate (PET) and polyurethane (PU). The photobiorefinery stage was found to have the greatest contribution to the impact categories, particularly due to direct emissions, consumption of electricity and production of extractive chemical agents used. These factors accounted for over 70% of the photobiorefinery impact in all cases. Avoided impacts provided net favourable outcomes in terms of carbon footprint and fossil resources when comparing PHA production to conventional plastics, especially PET and PU, with impact reductions ranging from 30% to 60%, respectively. However, when considering other impact categories like eutrophication, this situation was less favourable. The exploration of alternative scenarios offered significant impact reductions, especially when renewable electricity or an environmentally friendly extraction agent is used. Moreover, minimizing methane losses or co-producing hydrogen in the photobiorefinery had a notably positive effect on the carbon footprint, reducing the impact by more than 2 t of CO2 eq per t of PHA powder compared to the base case. Therefore, the implementation of feasible improvement measures in the short term can position PHA produced by mixed cultures as a sustainable alternative to petroleum-based plastics.

Sorption and economic viability of peat, compost and biochar for zinc-contaminated site

The growing demand for low-cost sorbents, which guarantee eco-efficiency in removing contaminants, has led to numerous studies in recent decades. In this sense, sorbents derived from organic residues have shown promising options; however, the organic fraction of municipal solid waste (OFMSW) has received little attention to date. This study compares the zinc (Zn) sorption performance of a traditional sorbent (peat) with that of materials derived from OFMSW (compost and biochar). According to the Langmuir model, biochar showed the highest sorption capacity (53.494 mg/g), followed by compost (37.569 mg/g) and peat (5.842 mg/g). Although the maximum sorption capacities adjusted by linear and non-linear regressions were close, the values were relevant only when they would have reached the saturation plateau. The cost estimate of the studied sorbents validated their economic viability with that of commercially available ones. The findings provide a theoretical basis for a better understanding of sorption experiments, from the choice of initial concentrations to the isothermal modelling of the results, for comparative evaluation of potential sorbents for the remediation of soils and waters contaminated with potentially toxic metals, such as zinc.

The development of data-intensive techno-economic models for the comparison of renewable natural gas production from six different biomass feedstocks for the decarbonization of energy demand sectors

Renewable natural gas (RNG) from biomass can be used as an alternative to natural gas. However, there is limited understanding of the economic viability of RNG production from a wide range of feedstocks. In this study, a comprehensive comparative techno-economic assessment of RNG production via gasification from six biomass feedstocks with a wide range of moisture contents and characteristics was conducted. The feedstocks studied are corn stover (CS), wheat straw (WS), whole forest (WF), forest residues (FR), cow manure (CM), and the organic fraction of municipal solid waste (OFMSW). The RNG production plants were simulated and the simulation results were used to develop techno-economic models for each feedstock to estimate the production cost of RNG. The pathways were compared in terms of RNG yield, RNG production quantity, electricity generation, as well as RNG production costs and cost components. Sensitivity analyses were conducted on a wide range of factors and effect of including cardon credit on the production cost were studied. RNG production costs from the gasification of the OFMSW and CS were lower than those of other feedstocks at 6.28 $/GJ and 6.32 $/GJ, respectively. If the avoided cost (as a source of revenue) of landfilling of the OFMSW or carbon credit (minimum 90 $/t CO2) is considered, the RNG production cost can be competitive with natural gas price (1.4 $/GJ). The information developed in study is critical for decision makers in policy formulation and investment decisions.

Life Cycle Assessment of sewage sludge mono-digestion and co-digestion with the organic fraction of municipal solid waste at a wastewater treatment plant

Wastewater treatment plants (WWTPs) aim to increase energy independence by intensifying biogas production. The study involved Life Cycle Assessment (LCA) comparing sewage sludge (SS) anaerobic co-digestion (AcD) with the organic fraction of municipal solid waste (OFMSW) at WWTP against SS anaerobic mono-digestion (AD). The LCA was based on the authors' research showing that methane production related to wet mass in AcD was higher than in AD by 86.4, 225.8, and 354.3 % for SS:OFMSW mixing ratios of 75:25, 50:50, and 25:75, respectively. The LCA was conducted for 1 kWh of biogas energy produced at a WWTP and included two subsystems: energy production (AD/AcD and CHP) and associated digestate management (drying, incineration with energy reuse, residual landfilling). CML-IA baseline 2013 and Recipe 2016 Midpoint (H) LCIA methodologies indicated the environmental impacts on abiotic depletion - fossil fuels (fossil resource scarcity), global warming, human toxicity (non-carcinogenic), freshwater, and marine aquatic ecotoxicity. AD of SS in all categories was characterized by the highest impact. The impact decreased with an increase in the OFMSW rate. Both methodologies showed a significant impact of AD and AcD on global warming, which indicated the need for the determination of the carbon footprint (CF) of 1kWh biogas energy production (gCO2 kWh−1) at WWTP, using IPCC 2021 GWP100 (incl. CO2 uptake). The CF was the highest for biogas energy production in SS AD (1509 gCO2 kWh−1) and it decreased with the increase of OFMSW content in AcD (872–481 gCO2 kWh−1). This was also observed for the management of associated digestate. CF changed from 1508 gCO2 kWh−1 for SS AD to 396 gCO2 kWh−1 for SS: OFMSW mixing ratio of 25: 75 in AcD. The environmental burdens associated with biogas energy production and digestate management were equally significant. Finally, the formula for economic and ecological comparison of SS AD and AcD with OFMSW was proposed.

Operational performance of organic fraction of municipal solid waste discarded from communities, using an in-vessel hyperthermophilic composting technology

There is a great need of in-situ Organic Fraction of Municipal Solid Waste (OFMSW) disposal inside community in most countries due to less transportation cost and secondary environmental while a shorter maturation period and less odor is required. In-vessel hyperthermophilic composting could probably address these issues. In this work, we reported the physicochemical parameters and corresponding microbial dynamics of a pilot-scale in-vessel Thermophilic Compost (HTC) and compared with Traditional Compost (TC). Results demonstrated that HTC effectively accelerated the maturation period of composting compared to TC, which shorten the whole compost cycle to 25 days. And the hyperthermophilic and thermophilic phases maintained more than one third of the whole period of HTC, which exhibiting superior or comparable key evaluation indexes than TC. Besides, the maximum N2O emission rate for TC is 10.2 times that of HTC. It was obviously due to extreme temperature as a result of inhibition of denitrifying bacteria for the HTC. Results of microbials analysis showed that during the thermophilic and hyperthermophilic period, mainly six strains of thermophilic bacteria including Bacillus (39.88%), Calditerricola (8.92%), Lactobacillus (8.76%), Oceanobacillus (5.4%), Planifilum (4.83%), and Ureibacillus (4.42%) were observed in HTC. It has been revealed that physico-chemical parameters can be regulated to optimize microbial composition for the purpose of enhancing hyperthermophilic composting, promoting organic matter degradation, and facilitating the recombination of middle-hyperthermophilic community OFMSW composting.

Use of a biogas-specific e-nose with machine learning to identify biogas pattern changes linked to hydraulic retention times in an anaerobic digester: A case study

Anaerobic digestion via biogas digesters is the most environmentally friendly solution to recycling degradable organic waste into organic fertilizer and energy. The organic fraction of municipal solid waste (OFMSW) is one of the main organic waste sources for biogas plants. The variations in characteristics of OFMSW as a main challenge lead to fluctuating organic loading rates and hydraulic retention time (HRT), which can adversely affect the performance of biogas plants. This study focused on the gaseous headspace of a biogas digester to assess a reliable monitoring method. An e-nose was applied to extract biogas patterns from a mesophilic digester, which operated at HRT of 30, 25, 20, and 15 days to treat OFMSW. The biogas samples were significantly classified based on their HRTs by the support vectors machine (SVM) and the random forest (RF). Finally, the results presented a promising method for monitoring the performance of the biogas digester.

Effect of forest-based biochar on maturity indices and bio-availability of heavy metals during the composting process of organic fraction of municipal solid waste (OFMSW)

The main objective of this study was to investigate the effect of biochar on the composting process of the organic fraction of municipal solid waste (OFMSW) under real conditions. Different doses of biochar (1%, 3%, and 5%) were mixed with compost piles to evaluate the variation of temperature, moisture content (MC), organic matter (OM), carbon (C), nitrogen (N), C/N ratio, and heavy metal (HM) contents in comparison with the control treatment (with 0% biochar addition). The results of this study showed that the compost piles combined with different doses of biochar had higher MC. The use of biochar as an additive, even at low doses (1%), was able to increase the compost quality through the reduction of N losses during the composting process. The highest reduction of OM during the composting process was observed in the control pile (without biochar addition) by 48.06%, whereas biochar affected the biodegradability of OM and prevented the reduction of nutrients during the composting process under real conditions. The contents of HMs (Pb, Zn, Ni, Cd, and Cu) showed a significant reduction in all of the compost piles combined with biochar in comparison with the control treatment. Considering that in terms of all compost quality indicators, the piles combined with biochar can regarded as high standard product, the composts obtained from combining the OFMSW with different biochar doses have desirable features to be used as an amendment agent to improve agricultural soil quality.

Achieving Discharge Limits in Single-Stage Domestic Wastewater Treatment by Combining Urban Waste Sources and Phototrophic Mixed Cultures.

This work shows the potential of a new way of co-treatment of domestic wastewater (DWW) and a liquid stream coming from the thermal hydrolysis of the organic fraction of municipal solid waste (OFMSW) mediated by a mixed culture of purple phototrophic bacteria (PPB) capable of assimilating carbon and nutrients from the medium. The biological system is an open single-step process operated under microaerophilic conditions at an oxidative reduction potential (ORP) < 0 mV with a photoperiod of 12/24 h and fed during the light stage only so the results can be extrapolated to outdoor open pond operations by monitoring the ORP. The effluent mostly complies with the discharge values of the Spanish legislation in COD and p-values (<125 mg/L; <2 mg/L), respectively, and punctually on values in N (<15 mg/L). Applying an HRT of 3 d and a ratio of 100:7 (COD:N), the presence of PPB in the mixed culture surpassed 50% of 16S rRNA gene copies, removing 78% of COD, 53% of N, and 66% of P. Furthermore, by increasing the HRT to 5 d, removal efficiencies of 83% of COD, 65% of N, and 91% of P were achieved. In addition, the reactors were further operated in a membrane bioreactor, thus separating the HRT from the SRT to increase the specific loading rate. Very satisfactory removal efficiencies were achieved by applying an HRT and SRT of 2.3 and 3 d, respectively: 84% of COD, 49% of N, and 93% of P despite the low presence of PPB due to more oxidative conditions, which step-by-step re-colonized the mixed culture until reaching >20% of 16S rRNA gene copies after 49 d of operation. These results open the door to scaling up the process in open photobioreactors capable of treating urban wastewater and municipal solid waste in a single stage and under microaerophilic conditions by controlling the ORP of the system.

Mass Transfer Enhancement in High-Solids Anaerobic Digestion of Organic Fraction of Municipal Solid Wastes: A Review.

The increasing global population and urbanization have led to a pressing need for effective solutions to manage the organic fraction of municipal solid waste (OFMSW). High-solids anaerobic digestion (HS-AD) has garnered attention as a sustainable technology that offers reduced water demand and energy consumption, and an increased biogas production rate. However, challenges such as rheology complexities and slow mass transfer hinder its widespread application. To address these limitations, this review emphasizes the importance of process optimization and the mass transfer enhancement of HS-AD, and summarizes various strategies for enhancing mass transfer in the field of HS-AD for the OFMSW, including substrate pretreatments, mixing strategies, and the addition of biochar. Additionally, the incorporation of innovative reactor designs, substrate pretreatment, the use of advanced modeling and simulation techniques, and the novel conductive materials need to be investigated in future studies to promote a better coupling between mass transfer and methane production. This review provides support and guidance to promote HS-AD technology as a more viable solution for sustainable waste management and resource recovery.

Low-dosage enzymatic hydrolysis of organic municipal waste for sugar and ethanol production

AbstractEnzymatic hydrolysis (EH) of the organic fraction of municipal solid waste (OFMSW) is challenging due to its complexity and heterogeneous character. This study investigated the effects of OFMSW compositional characteristics and pretreatment techniques on the efficiency of EH. The experiments involved varying enzymatic dosages and pretreatment methods, including heat pretreatment and anaerobic incubation of raw OFMSW. Remarkably, after thermal pretreatment, a saccharification yield exceeding 50% was achieved with only 1 filter paper unit (FPU) of Cellic® Ctec3 and 0.5 glucoamylase unit (AGU) of AMG® 300 L BrewQ per g of dry OFMSW. This resulted in the recovery of 239 g of sugar per kilogram of dry OFMSW. The study revealed that the decomposition of OFMSW by enzymes is limited after reaching about 50% of the sugar recovery yield, and high concentrations of inhibitors such as organic acids, alcohols, and potentially other organics and inorganics may contribute to this limitation. These compounds, however, serve as excellent preservatives, achieving contamination control during biological conversion. Sugar-rich hydrolysates were subjected to ethanol fermentation using Saccharomyces cerevisiae, leading to the conversion of most hexose sugars into ethanol, reaching 331 g of ethanol per kilogram of dry OFMSW, and indicating that the limitation of OFMSW saccharification was not due to product inhibition. These findings highlight the need for further investigation of the saccharification process of biowaste to overcome inhibitory effects and subsequently achieve higher efficiency of the following bioprocesses.

Semi-continuous anaerobic co-digestion of thermal and thermal-alkali processed organic fraction of municipal solid waste: Methane yield, energy analysis, anaerobic microbiome

The semi-continuous anaerobic co-digestion (AcoD) of thermal and thermal-alkali pretreated organic fraction of municipal solid waste (OFMSW) and sewage sludge (SS) was studied under varying hydraulic retention times (HRT) and organic loading rates (OLR Three semi-continuous digesters were operated under control (non-pre-treated), thermally pretreated (125 °C), and thermal-alkali pretreated (125°C-3g/L NaOH) conditions at variable OLRs at 2.5, 4.0, 5.1, and 7.6 kgVS/m3.d and corresponding HRTs of 30, 20, 15, and 10 days. The 10 and 43% higher methane yield (0.445 m3/kgVS) and 11 and 57% higher VS removal (52%) was achieved for thermal-alkali pretreated digester at 5.1 kgVS/m3.d OLR over thermally pretreated (0.408 m3/kgVS, 45% VS removal) and control digesters (0.310 m3/kgVS, 33% VS removal), respectively. Thermal and thermal-alkali digesters failed on increasing the OLR to 7.6 kgVS/m3.d, whereas the control digester becomes upset at 5.1 kgVS/m3.d OLR. The metagenomic study revealed that Firmicutes, Bacteroidetes, Chloroflexi, Euryarchaeota, Proteobacteria, and Actinobacteria were the predominant bacterial population, whereas Methanosarcina and Methanothrix dominated the archaeal community. Energy balance analysis revealed that thermal alkali pretreatment showed the highest positive energy balance of 114.6 MJ/ton with an energy ratio of 1.25 compared with thermally pretreated (81.5 MJ/ton) and control samples (−46.9 MJ/ton). This work pave the way for scaleup of both thermal and thermal-alkali pre-treatment at 125 °C to realize the techno-economic and energy potential of the process.

Hybrid Prediction-Driven High-Throughput Sustainability Screening for Advancing Waste-to-Dimethyl Ether Valorization.

Assessing the prospective climate preservation potential of novel, innovative, but immature chemical production techniques is limited by the high number of process synthesis options and the lack of reliable, high-throughput quantitative sustainability pre-screening methods. This study presents the sequential use of data-driven hybrid prediction (ANN-RSM-DOM) to streamline waste-to-dimethyl ether (DME) upcycling using a set of sustainability criteria. Artificial neural networks (ANNs) are developed to generate in silico waste valorization experimental results and ex-ante model the operating space of biorefineries applying the organic fraction of municipal solid waste (OFMSW) and sewage sludge (SS). Aspen Plus process flowsheeting and ANN simulations are postprocessed using the response surface methodology (RSM) and desirability optimization method (DOM) to improve the in-depth mechanistic understanding of environmental systems and identify the most benign configurations. The hybrid prediction highlights the importance of targeted waste selection based on elemental composition and the need to design waste-specific DME synthesis to improve techno-economic and environmental performances. The developed framework reveals plant configurations with concurrent climate benefits (-1.241 and -2.128 kg CO2-eq (kg DME)-1) and low DME production costs (0.382 and 0.492 € (kg DME)-1) using OFMSW and SS feedstocks. Overall, the multi-scale explorative hybrid prediction facilitates early stage process synthesis, assists in the design of block units with nonlinear characteristics, resolves the simultaneous analysis of qualitative and quantitative variables, and enables the high-throughput sustainability screening of low technological readiness level processes.

Effect of co-digestion and hydrodynamic disintegration on the methane potential of sewage sludge and organic fraction of municipal solid waste with consideration of the carbon footprint

The study objective was to investigate the applicability of co-digestion and/or hydrodynamic disintegration as potential methods of methane production intensification from sewage sludge (SS) and the organic fraction of municipal solid waste (OFMSW) with consideration of carbon footprint (CF) assessment. Methane production was determined by means of biochemical methane potential tests. For co-digestion, the highest increase in methane production (53.8 %) was observed for the SS:OFMSW mixing ratio 40:60. Hydrodynamic disintegration at all tested energy densities (10, 30 and 60 kJ/L) caused release of soluble organic compounds from both substrates, although accelerated methane production was only observed at 10 kJ/L. An increase in methane potential for substrates disintegrated separately did not imply analogical results for the disintegration of their mixture. Within the assumed limits, CF per 1 Nm3 of produced methane, CF per 1 t of wet feedstock for the digester, and estimated CF per 1 kWh produced were also calculated. Comparable values of all indicators were obtained for monodigestion and co-digestion. The highest CF indices were achieved for monodigestion of disintegrated SS and increased significantly with applied energy density. The obtained results can serve as valuable material for operators of wastewater treatment plants facilitating the selection of sustainable methods of increasing renewable energy production.

Anaerobic Co-digestion of sewage sludge and organic fraction of municipal solid waste: Focus on mix ratio optimization and synergistic effects

The utilization of municipal solid waste (MSW) and sewage sludge (SS) as a source of renewable energy is crucial in achieving sustainable and integrated MSW management. SS and organic fraction of municipal solid waste (OFMSW) can be anaerobically digested to produce methane for energy. However, anaerobic digestion of specific substrates is challenging with respect to substrate characteristics. The problem of mono-digestion can be mitigated by co-digestion of these two major organic wastes because of their complementary characteristics. Moreover, there is a lack of studies on optimization of different mix ratios of organic fraction of municipal solid waste (OFMSW) and sewage sludge (SS) based on total solids (TS). The study aims to optimize the mix ratio for anaerobic co-digestion of OFMSW and SS. The study further elucidates synergistic effects associated with the co-digestion process. Different mix ratios of SS and OFMSW (0:100, 20:80, 40:60, 60:40, 80:20, 100:0) at 5, 7.5 and 10% TS were assessed for biomethane potential assessment. The results showed that with an increase in SS in the mix ratio feed the methane yield increased by 91% and 50% as compared to mono digestion of sewage sludge and OFMSW respectively at TS 7.5%. Based on the kinetic analysis, it was observed that the lag phase reduced for 60:40 mix ratio leading to higher rate of biodegradation. Positive synergistic effects were observed for 40:60, 60:40 and 80:20 mix ratio of SS:OFMSW based on co-digestion impact factor value. Response surface modelling was used to get the optimized mix ratio and TS %. The optimum mix ratio with the highest methane yield (388 ml/gVS added) was 70:30 (SS: OFMSW) at TS 7.5% with a desirability value of 0.98. These findings demonstrate that co-digesting SS and OFMSW is a preferable alternative for harnessing renewable energy and managing organic waste in a sustainable manner.