Digestion Of Solid Waste Research Articles

The new strategies of using nitrogen and iron modified hydrochar to enhance methane production during co-anaerobic digestion of cow manure and corn straw

The traditional hydrochar shows limited ability to promote methane production during anaerobic digestion of organic solid waste. This study explored the effect of hydrochar modified using nitrogen and iron on methane production and microbial communities during the co-anaerobic digestion (co-AD) of cow manure and corn straw. Compared with unmodified hydrochar prepared from biogas residue (BHC), iron and nitrogen-iron modified hydrochar (BHC-Fe and BHC-N) improved the specific surface area (SSA) and proportion of oxygen-containing functional groups (OCFGs) related to direct interspecies electron transfer. The results showed that, compared to the control group (without hydrochar addition), the total methane production increased by 30 %, 36 %, and 46 % in the BHC, BHC-Fe, and BHC-N groups, respectively. The addition of modified hydrochar improved the microbial diversity and enrichment of Methanobacterium, Methanobrevibacter, and Methanosarcina spp., with BHC-N being the most effective. COD and Methanobrevibacter showed the highest explanation for methane production in AD performance indexes and archaeal genera (66.4 % and 29.3 %). Surface OCFGs of hydrochar had a more significant and direct effect on methane production than the SSA and archaeal genera. Therefore, the addition of BHC-N contributes more to promote methane production during the co-AD of cow manure and corn straw. This study could provide the new strategies for improving the co-AD of cow manure and corn straw performance, further promoting the resourcing and disposal of cow manure and corn straw.

Identifying reliable microbial indicators in anaerobic digestion of organic solid waste: Insights from a meta-analysis

The identification of microbial indicators holds significant promise for detecting key challenges of anaerobic digestion, driving microbial management. In order to be considered reliable, microbial indicators must possess certain features, such as universality, significant abundance changes under stressful conditions, and the ability to predict CH4 yield. To investigate the performance of microbial indicators, a meta-analysis was conducted on 178 publicly available 16 S rRNA gene sequences from 12 studies that examined the anaerobic digestion process of organic solid wastes. The analysis identified key taxa that achieved microbial indicator features through two different approaches: whole community and core microbiome analysis. The alpha diversity analysis indicated that a specialized genus-level microbial community with a high number of sOTUs was crucial for achieving high CH4 yield. Aminobacterium, Clostridium, HA73, T78, Corynebacterium, Lactobacillus, and Prevotella exhibited a higher number of microbial indicators attributes, including a significant response in their abundance and predictive capability for CH4 yield, along with relevant metabolic roles associated with inhibitory compounds. Among them, Corynebacterium, Lactobacillus, and Prevotella demonstrated robust fold-change features to increase the likelihood of successful categorization and, Aminobacterium, Clostridium, HA73, and T78 showed universality, suggesting easy detection across various anaerobic digestion processes. Understanding the advantages and drawbacks of reliable microbial indicators and considering their features will aid in the selection of appropriate detection techniques, offering valuable insights for future validation and implementation for AD processes improvement or control.

Anaerobic digestion of winery solid waste in a two-stage membrane process: Effect of loading rate on biomethane production

The wine industry causes a high amount of solid waste with high organic content at different parts of the production line. One of the best strategies to overcome organic solid waste management problem is anaerobic digestion, as It allows renewable energy production and waste reduction together. The OLR is considered one of the most important operating parameters in continuous or semi-continuous anaerobic operations, as it affects the overall performance of anaerobic digestion systems. Therefore, appropriate OLR determination plays a crucial role in anaerobic digestion. This study investigated the effect of OLR on the performance of a TAnMBR treating (winery solid waste) WSW in terms of biogas and biomethane production. To this end, the production of biogas and biomethane from WSW via a TAnMBR at four different OLRs (0.5 0.75 1.0 1.5 gVS/Lreac d) was investigated. Biogas production rates were 677, 850, 1265, and 566 ml/gVS and biomethane production rates were 352, 450, 679, and 251 ml/gVS respectively, during 0.5 0.75 1.0 1.5 gVS/Lreac d OLR operating conditions. Results revealed that proper biogas and biomethane production can continue until the OLR is 1.5. VFA accumulation can be considered as the main inhibition reason, at 1.5 OLR VFA/Alk ratio increased up to 1.6 with 1864 mgHAc/L VFA concentration. Additionally, phenol and sulfate concentrations were below 45 and 48 mg/L during operation, respectively, therefore it is considered that no inhibition occurred due to these parameters.

Vacuum ammonia stripping from liquid digestate: Effects of pH, alkalinity, temperature, negative pressure and process optimization

High ammonia-nitrogen digestate has become a key bottleneck limiting the anaerobic digestion of organic solid waste. Vacuum ammonia stripping can simultaneously remove and recover ammonia nitrogen, which has attracted a lot of attention in recent years. To investigate the parameter effects on the efficiency and mass transfer, five combination conditions (53 °C 15 kPa, 60 °C 20 kPa, 65 °C 25 kPa, 72 °C 35 kPa, and 81 °C 50 kPa) were conducted for ammonia stripping of sludge digestate. The results showed that 80% of ammonia nitrogen was stripped in 45 min for all experimental groups, but the ammonia transfer coefficient varied under different conditions, which increased with the rising of boiling point temperature, and reached the maximum value (39.0 mm/hr) at 81 °C 50 kPa. The ammonia nitrogen removal efficiency was more than 80% for 30 min vacuum stripping after adjusting the initial pH to above 9.5, and adjustment of the initial alkalinity also affects the pH value of liquid digestate. It was found that pH and alkalinity are the key factors influencing the ammonia nitrogen dissociation and removal efficiency, while temperature and vacuum mainly affect the ammonia nitrogen mass transfer and removal velocity. In terms of the mechanism of vacuum ammonia stripping, it underwent alkalinity destruction, pH enhancement, ammonia nitrogen dissociation, and free ammonia removal. In this study, two-stage experiments of alkalinity destruction and ammonia removal were also carried out, which showed that the two-stage configuration was beneficial for ammonia removal. It provides a theoretical basis and practical technology for the vacuum ammonia stripping from liquid digestate of organic solid waste.

Co-digestion of solid-liquid waste from citrus agroindustrial: Effect of hydraulic retention time and organic loading rate on H2 production in a long-term continuous operation leach bed reactor

The Leach Bed Reactor (LBR) application is a promising alternative for the anaerobic digestion of solid waste and wastewater. In this study, the LBR was continuously operated for 160 days in four different phases, for co-fermentation of solid and liquid waste from the citrus agroindustry, at 37 °C, evaluating the effect of hydraulic retention time (HRT) and organic loading rate (OLR). The maximum volumetric hydrogen production (VHPR) was observed at an HRT of 12h (958.3 mLH2.L-1.d-1); however, the highest hydrogen yield (HY) was identified at an HRT of 24h (104.9 mLH2.g-1CHO). Based on the metabolic characteristics of microorganisms identified in higher relative abundance, by 16S rRNA sequencing, such as Lactobacillus, Caproicoproducens, Bifidobacterium, Olsenella, and Solobacterium, an occurrence of chain elongation pathways in the production of butyric and caproic acids was inferred, with hydrogen production resulting from the lactic acid oxidation. The maximum electricity production potential of 16.3 kWh.m-3 liquor was estimated.

Metal mobility in an anaerobic-digestate-amended soil: the role of two bioenergy crop plants and their metal phytoremediation potential

Panicum virgatum and Pennisetum alopecuroides, two non-food bioenergy crops, were evaluated for their capacity to phyto-manage trace metals (Pb, Zn, Ni, Fe, Mn, Co, Cr, and Cu) from municipal solid waste digestate after its application to a marginal soil. For that, 90-day vertical soil column mesocosm (columns with 0.6 × 0.2 m) experiments were carried out to assess 1) the impact of digestate application on the health of marginal soil, 2) plant effect on digestate-borne trace metals’ mobility along the soil profile (measuring total metal levels and fractionation in different soil layers by atomic absorption spectroscopy, and 3) plant growth performance and trace metal (Pb, Zn, and Cu) uptake capacity. The results showed that trace metals were mostly confined in the 0–0.2 m soil horizon over the course of the experimental period, migrating from the digestate-amended soil layer (0–0.1 m) to the layer underneath (0.1–0.2 m) within the first 21 days and remaining stable afterward. No evidence of the trace metals’ mobility to deeper soil layers was detected. Migration of trace metals was reduced in the presence of P. virgatum and P. alopecuroides, suggesting a phytoremediation (phytostabilization) effect. For both plant species, no trace metal accumulation in the roots was observed (bioconcentration factor <1), although both plants showed a potential for Zn translocation for aboveground tissues (translocation factor >1). The growth of both plants was positively affected by municipal solid waste digestate application, which also improved soil quality (increased concentration of total organic carbon and available phosphorus, as well as cation exchange capacity and water holding capacity).

Technological Prospection and Flowchart for Production of Biogas Enriched with Hydrogen: A Proposal for Renewable Energy Sources

Over time, environmental issues have taken on significant proportions worldwide, making using renewable energy sources increasingly trivial, notorious, and indispensable. Projects focused on sustainability enable the expansion and diversification of current energy matrices, such as the potential use of biogas as an alternative source. Therefore, the project aimed to develop a flowchart proposal through technological prospection, given the production of biogas enriched with hydrogen through anaerobic digestion of solid waste. Thus, a technological prospecting of patents and quantitative analysis of scientific articles was carried out to show an overview of the production of biogas associated with hydrogen from 2012 to 2022, based on the studies that analyzed the viability and efficiency of the use of hydrogen for biogas production.

Meso- and thermophilic posttreatment of press water coming from a thermophilic municipal solid waste digester.

An efficient biogas production out of organic (waste) materials is important to contribute to a carbon-neutral future. In this study, thermophilic press water (PW) coming from an organic fraction of the municipal solid waste digester was further digested in a thermo- and mesophilic posttreatment approach using two semicontinuous 14 L digesters. The results showed that the PW can still have considerable high biogas potential-at least during the touristic high season in central Europe. The change in temperature led to an increase in volatile fatty acid concentrations and a decrease in biogas production in the mesophilic approach in the first days. However, the losses in biogas production at the beginning could be compensated thus there were no considerable differences in biogas production between thermo- and mesophilic posttreatment at the end of incubation. This can most probably be contributed to a change in the microbial community, and potentially problematic intermediates like valerate could be better degraded in the mesophilic reactor. Especially the abundanceof representatives of the phylum Bacteroidota, like Fermentimonas spp., increased during mesophilic anaerobic digestion.

Changes in the prokaryotic communities occurring along a two-stage anaerobic digestion system treating the organic fraction of solid waste

Two-stage anaerobic digestion is useful for recycling of the organic fraction of municipal solid waste and wastewater; the prokaryotic communities involved in this process were characterized using massive sequencing of 16S rRNA gene amplicons. During the 60-day study the prokaryotic communities were stable in time but were affected by their position in the system. The first stage of solid waste digestion was operated in an anaerobic-hydrolytic leach bead reactor with high organic solids content, the microbial communities were dominated by members of the orders Bacteroidales (62%), Selenomonadales (15%), Lactobacillales (13%), Clostridiales (4%) and Rhodospirillales (1%). At this stage, a vertical stratification acted as a transition zone from aerobic to anaerobic environments modifying significantly the composition and structure of bacterial communities.The second stage occurred in an up-flow anaerobic sludge bed reactor specialized in acidogenesis-methanogenesis, where the leachate of the first stage was co-fed with municipal wastewater. In this stage, the bacterial community was dominated by members of the orders Pseudomonadales, Clostridiales, Burkholderiales, Bacteroidales and Syntrophobacterales (accounting for 52%), while the most abundant orders of the archaeal community corresponded to Methanosarcinales (72%) and Methanobacteriales (13%), both of them with methanogenic capacity.

Microbial Population Dynamics during Unstable Operation of a Semicontinuous Anaerobic Digester Fed with a Mild-Treated Olive Mill Solid Waste

This research evaluates process instability together with microbial population dynamics of the startup of an anaerobic digestion of a mild pretreated solid olive oil waste. The pretreatment consisted of a mild thermal treatment called thermo-malaxation and a subsequent dephenolized process of the olive mill solid waste. The anaerobic digestion process of the mild pretreated and partially dephenolized biomass was studied for three Hydraulic Retention Times (HRTs), with 21 days each HRT, with an organic load rate of 1 g VS/L d, carried out at mesophilic temperature (35 ± 1 °C). The average value of methane yield decreased from 204 ± 9 mL CH4/g VS d on day 21, the last day of the first HRT, to 87 ± 24 mL CH4/g VS d on day 60, the last day of the third HRT. The alkalinity decreased drastically, indicating instability of the anaerobic digestion process. Although phenolic compounds were partially extracted in the pretreatment, the observed increase in phenolic compounds during reactor operation might be contributed to the methane production decay. Interestingly, volatile fatty acids decreased with time, indicating that not only the methanogenic stage but also the hydrolysis stage was affected. Indeed, the microbial analysis showed that the abundance of hydrolytic bacteria decreased over time. It is also worth noticing that hydrogenotrophic methanogens, while present during the first two HRTs, were not observed at the end of the last HRT. This observation, together with the increase in the relative abundance of acetoclastic methanogens, showed a shift in the methane production pathway from hydrogenotrophic methanogenesis to acetotrophic methanogenesis.

Effect of alkaline pre-treatment on hydrolysis rate and methane production during anaerobic digestion of paunch solid waste

Paunch is comprised of the partially digested feed contained in cattle or sheep and contributes 20–50% of organic waste produced at red meat processing facilities. Anaerobic digestion has been identified as a promising technology for paunch treatment, however treatment times can be long and when combined with the moderate degradability of paunch this results in high treatment costs that need to be improved. Pre-treatment was investigated as a strategy to improve AD of paunch, alkaline treatment (NaOH or KOH) was selected due to the high lignin content. A range of alkaline loadings (1–20 g 100gTS−1) were tested with an equivalent hydroxide molar concentration of 9–250 mM [OH−]. Alkaline pre-treatment improved both the hydrolysis rate and the overall degradability of paunch solid by up to 4.4 times and 60%, respectively. The enhanced hydrolysis rate and methane yield was correlated to changes in material composition during pre-treatment. While alkaline concentration was an important factor, there were no significant improvements at alkaline concentrations above 12 g 100gTS−1 (150 mM [OH−]).

Estimation of biogas generation rate and carbon sequestration potential from two landfill sites in southern India.

Anaerobic digestion of organic solid waste is one of the mechanisms for sustainable development since it permits both the energy-efficient disposal of solid waste and the use of biogas. As a result, this study provides an assessment of the potential energy and emissions saved by using biogas energy generated from the biodegradation of solid waste. For present study two major cities are selected in south India namely Madurai, Tamil Nādu and Hyderabad, Telangana. The LandGEM 3.03 model is used to estimate the concentration of total landfill gases. The landfill in Madurai produced 2.162 × 106 cu. m per year of methane emissions in the year 2013. The production of biogas has increased over time would continue to increase until 2045, when a production rate of 6.32 × 107 cu. m per year was recorded as the largest concentration of biogas ever generated. For the Hyderabad landfill, methane concentrations during the year 2013 was recorded to be 2.5 × 107 cu. m per year and reached a peak in 2046 with a concentration of 3.7 × 108 cu. m per year, was found to have a potential to generate 2.1 × 106 kWh per year. For the Madurai dump site, the energy potential increases gradually and reaches a peak during the year 2047 with a value of 4.54 × 107 kWh per year. Whereas for Hyderabad dump site was found to have an energy equivalent of 2.1 × 108 kWh per year during 2024 and reaches a peak during 2046 with an energy equivalent of 5.1 × 108 kWh per year.

Design, multi-aspect analyses, and multi-objective optimization of a novel trigeneration system based on geothermal and municipal solid waste energies

The study of multi-source energy systems, due to higher performance and producing various products, is an interesting subject. The current study designs a multi-source system including a gas turbine cycle with CH4 and municipal solid waste digester, a geothermal system with an organic Rankine, organic flash, and a double-effect absorption refrigeration subsystem to produce power, cooling, and heating loads simultaneously. The thermodynamic and economic analyses are utilized to estimate the system’s performance and multi-objective optimization has been applied to define the optimum state of the system concerning two scenarios. The results indicate that the system provides 423.4 kW net power, 384.7 kW heating load, and 106.3 kW cooling load with 39.28% exergetic efficiency and 6.67 years payback period. These values are improved to 664.9 kW net power, 446.5 heating load, 42.01% exergetic efficiency, and 6.05 years payback period at the best optimum scenario. The sensitivity analysis reveals that the air compressor’s pressure ratio mainly impacts the net power, heating load production, and net present value. The cooling load production and exergetic efficiency are mainly affected by the air preheater effectiveness variation.

Insights into the Occurrence, Fate, Impacts, and Control of Food Additives in Food Waste Anaerobic Digestion: A Review.

The recovery of biomass energy from food waste through anaerobic digestion as an alternative to fossil energy is of great significance for the development of environmental sustainability and the circular economy. However, a substantial number of food additives (e.g., salt, allicin, capsaicin, allyl isothiocyanate, monosodium glutamate, and nonnutritive sweeteners) are present in food waste, and their interactions with anaerobic digestion might affect energy recovery, which is typically overlooked. This work describes the current understanding of the occurrence and fate of food additives in anaerobic digestion of food waste. The biotransformation pathways of food additives during anaerobic digestion are well discussed. In addition, important discoveries in the effects and underlying mechanisms of food additives on anaerobic digestion are reviewed. The results showed that most of the food additives had negative effects on anaerobic digestion by deactivating functional enzymes, thus inhibiting methane production. By reviewing the response of microbial communities to food additives, we can further improve our understanding of the impact of food additives on anaerobic digestion. Intriguingly, the possibility that food additives may promote the spread of antibiotic resistance genes, and thus threaten ecology and public health, is highlighted. Furthermore, strategies for mitigating the effects of food additives on anaerobic digestion are outlined in terms of optimal operation conditions, effectiveness, and reaction mechanisms, among which chemical methods have been widely used and are effective in promoting the degradation of food additives and increasing methane production. This review aims to advance our understanding of the fate and impact of food additives in anaerobic digestion and to spark novel research ideas for optimizing anaerobic digestion of organic solid waste.

Improvements in the anaerobic digestion of biological sludge from pulp and paper mills using thermal pretreatment.

The current disposal of biosludge generated in wastewater treatment has high costs and causes environmental problems, anaerobic digestion (AD) of solid waste is a promising alternative. Thermal hydrolysis (TH) is an accepted technology to enhance anaerobic biodegradability of sewage sludge, but this technology has not been developed to be used with biological sludge from industrial wastewater treatment. In this work, the improvements to the AD of biological sludge from cellulose industry when thermal pretreatment is carried out were experimentally determined. The experimental conditions for TH were 140 °C and 165 °C for 45 minutes. Batch tests were carried out to quantify methane production evaluated as biomethane potential (BMP), anaerobic biodegradability according to volatile solids (VS) consumption and kinetic adjustments. An innovative kinetic model based on the serial mechanism of fast and slow biodegradation fractions was tested for untreated waste, and parallel mechanism was also evaluated. Increases in BMP and biodegradability values according to VS consumption were determined with increasing TH temperature. The results of 241 NmL CH4 gVS substrate-1 for BMP and 65% biodegradability are reported for the 165 °C treatment. AD rate increased for the TH waste compared to the untreated biosludge. Improvements of up to 159% for BMP and 260% for biodegradability according to VS consumption were quantified for TH biosludge compared to untreated biosludge.

Comparing VFA Composition, Biomethane Potential, and Methane Production Kinetics of Different Substrates for Anaerobic Fermentation and Digestion

Solid waste is one of the largest sources of greenhouse gases (GHGs) today. The carbon footprint of landfills also has a large impact on global warming. Therefore, it is becoming more urgent to study the possibility of better environmentally friendly approaches for solid waste management and its safe disposal. The digestion of solid waste is a biological process that breaks down the organic content of the solid waste and thus stabilizes it. It also allows the recovery of valuable resources (such as biogas) and the utilization of stabilized waste in various industries. In this study, six substrates were studied to determine their biomethane potential (BMP) in anaerobic digestion. The substrates were fermented and digested anaerobically, and the biogas production was measured. The methane yield of food waste substrates had a higher methane yield between 354 and 347 mL/g-TCOD, and a biodegradability of 89–87%. Wastewater sludge substrates yielded between 324 and 288 mL/g-TCOD with a biodegradability of 81–73%. A kinetics analysis using first-order and Gompertz models was performed for biodegradation and methane production.

Experimental approach for catalytic combustion of biogas: Preliminary research

Nowadays, the use for renewable resources comes as a necessity to stringent energetic consumption issues that are related to both economic and energy autonomy (if possible) by using alternative sources of energy. In this context, one possible solution could be the application of anaerobic digestion processes, with a main energy carrier as result in the production of biogas. The focus for the present paper is to analyze the possibility to obtain biogas through anaerobic digestion of solid agricultural wastes (degraded corn and wheat) in municipal waste waters substrate. The biogas production was tested on a self-sustained double biogas reactors and CH4 production obtained presented. Combustion of biogas-like syngas simulating produced biogas was performed in the presence of ZnAl2O4 and CoAl2O4 catalyst, in an experimental combustor. Experiments conducted showed that both corn and wheat blended with municipal waste water produce biogas with up to 80% CH4 concentration and that combustion behavior of biogas is improved in presence of CoAl2O4 catalyst.

Matured Manure and Compost from the Organic Fraction of Solid Waste Digestate Application in Intensive Apple Orchards

In intensive fruit growing systems, the recovery and maintenance of soil fertility play a crucial role in both environmental protection and sustainable support to plant productivity. The circular economy approach adopted at the EU level strongly promotes the use of organic products instead of mineral fertilizers. This work focuses on two different soil improvers, compost from the organic fraction of municipal solid waste digestate (CO) and "matured" manure, produced after a fast and controlled aerobic treatment in an aerated pile (MM), which were applied in three apple orchards with different soil tillage. The soil improvers have been characterized for amendment and fertilizing properties. After the amendment, the soils were sampled twice a year (Spring and Autumn) for three years. Each sample has been characterized for texture, pH, cation exchange capacity, nutrients, soil organic matter, and micronutrients. The amendments obtained differed on C, N, P, and K contents, but had similar biological stability. The main effects on soils were the increasing of N and soil organic matter after compost application, while the use of matured manure mainly act on available P and exchangeable K. The treatments showed significant effects among fields with a linear increasing trend only for compost. Matured manure showed more effects in earlier times. The data collected aim to improve the knowledge about sustainable management of soil organic matter and organic nutrients in intensive fruit-growing agriculture by using local products.

Multiple-Batch Digestion of Community Solid Waste with Recirculated Slurry as Inoculum: Performance and Microbial Community

Multiple-Batch Digestion of Community Solid Waste with Recirculated Slurry as Inoculum: Performance and Microbial Community

Exploring drying kinetics and fate of nutrients in thermal digestion of solid organic waste.

Thermal digestion has emerged as a novel technique for the rapid treatment of solid organic waste (SOW). Dehydration mechanism and fate of nutrients during the thermal digestion of the SOW were explored. A series of experiments were carried out in a specially designed laboratory-scale dehydrator to determine its drying kinetics. The statistical analysis revealed that the diffusion model predicted the dehydration profile most accurately than other models. The effective moisture diffusivity coefficient depended on the temperature and varied from 2.81 × 10-08 m2/s to 8.68 × 10-08 m2/s at the tested temperature range. The activation energy required for complete dehydration was found to be 26.56 kJ/mol. The artificial neural network (ANN) model was found highly efficient (R2 - 0.983) in predicting the total drying time required for attaining equilibrium moisture content. The total N decreased from 2.2% to 1.81% due to evaporation of ammonical nitrogen, while the availability of P and K was increased from 0.38% to 0.43% and 1.47% to 1.75%, respectively when the temperature was increased from 110 °C to 170 °C. The thermal dehydration technique was found effective in digesting the organics and improving the bioavailability of the nutrients, which favours for its re-utilization in agriculture.