Search Results (19)

To achieve the required recycling rates, organic recycling via composting should be widely introduced in Poland for selectively collected biowaste. However, this process not only produces compost but also leachate (L_CB), a nitrogen- and organics-rich liquid by-product. So far there has been limited information on the application of anaerobic digestion (AD) for treating L_CB, which has fermentative potential. However, for effective methane production (MP) via AD, the ratio of chemical oxygen demand to total Kjeldahl nitrogen (COD/TKN) and pH of L_CB are too low; thus, it should be co-digested with other organics-rich waste, e.g., glycerine (G). The present study tested the effect of G content in feedstock (in the range of 3–5% (v/v)) on the effectiveness of co-digestion with L_CB, based on MP and the removal of COD. MP was accessed by using an automatic methane potential test system (AMPTS). Regardless of the feedstock composition (L_CB, or L_CB with G), the efficiency of COD removal was over 91%. Co-digestion not only increased MP by 6–15%, but also the methane content in the biogas by 4–14% compared to L_CB only (353 NL/kg COD_added, 55%). MP and COD removal proceeded in two phases. During co-digestion in the 1st phase, volatile fatty acids (VFA) accumulated up to 2800 mg/L and the pH decreased below 6.8. The presence of G altered the shares of individual VFA and promoted the accumulation of propionic acid in contrast to L_CB only, where caproic acid predominated. An initial accumulation of propionic acid and acidification in the mixtures decreased the kinetic constants of MP (from 0.79 to 0.54 d⁻¹) and the rate of COD removal (from 2193 to 1603 mg/(L·d)). In the 2nd phase, the pH recovered, VFA concentrations decreased, and MP was no longer limited by these factors. However, it should be noted that excessive amounts of G, especially in reactors with constant feeding, may cause VFA accumulation to a greater extent and create a toxic environment for methanogens, inhibiting biogas production. In contrast, digestion of L_CB only may lead to ammonium buildup if the COD/TKN ratio of the feedstock is too low. Despite these limitations, the use of AD in the treatment of L_CB as a sustainable “closed-loop nutrient” technology closes the loop in composting of biowaste. Full article

Population growth, urbanization, and changing consumption patterns are contributing to an increase in household waste production, particularly in sub-Saharan Africa. Composting of biowaste presents a sustainable solution by reducing the volume of waste sent to landfills while enriching the soil. The main objective of this study was to evaluate the suitability of solid household biowaste for composting in market garden crops in Dolisie (the Republic of Congo). Specifically, the study aimed to (i) assess the production and management practices of solid household waste in relation to socio-economic factors, (ii) analyze the chemical composition of solid household biowaste and its concentration of trace elements (TEs), and (iii) determine the potential phytotoxicity of solid household biowaste across different production seasons. In this study, wastes were collected from 40 households over a 60-day period, with daily sorting conducted during both the dry and wet seasons. Using a completely randomized design, various compost application rates were incorporated into the soil to conduct a germination test. The quality of the biowaste and compost was evaluated through physicochemical analyses. Results showed that approximately 90% of high-income households received regular waste collection services and practiced waste separation in contrast to middle- and low-income households. The composition of the biowaste was primarily composed of fruit and vegetable scraps, with slight contamination by chromium and cadmium. Temperature, pH, and humidity levels showed similar trends during compost formation in both the rainy and dry seasons. Germination rates were above 80% in all treatments across both seasons, indicating that the compost was mature. Overall, all physicochemical parameters of the compost met established quality standards, and trace element concentrations were below the recommended thresholds. The study concluded that biowaste, once converted into compost, can be safely applied to agricultural soils without posing any risk of phytotoxicity or contamination to crops. Full article

This paper presents a proposed circular economy (CE) model for hospital bio-waste management, using Athens as a case study to demonstrate its applicability in urban environments. The model incorporates waste segregation at the source, resource recovery methods such as composting and anaerobic digestion, and data-driven tools to enhance the efficiency and sustainability of healthcare waste management. The study investigates the transition from linear to CE practices, focusing on structured collection strategies, collaborative efforts between hospitals and municipal authorities, and continuous tracking of waste flows. A comprehensive analysis of bio-waste volumes from participating hospitals over a three-year period is conducted, utilizing multi-criteria decision-making (MCDM) tools such as TOPSIS to evaluate the system’s effectiveness. The results indicate a significant increase in hospital participation, improved waste separation, and optimized resource recovery, offering a scalable framework for other municipalities seeking to implement CE-based waste management practices in healthcare settings. Full article

There is a general consensus that bio-waste is a suitable material for valorization by means of the fermentation process with the production of biogas. The success of a bio-waste closed-loop economy will ultimately be determined by the demand for the products made from it. Poor-quality composts and fermentation products will not be allowed on the market in the long term. This means that not only final products but also bio-waste from separate collections must also meet the quality requirements. The aim of this 12-month study was a monthly analysis determining the level of contaminants in bio-waste collected from rural communities, single-family neighborhoods in urban areas, and multi-family neighborhoods in urban areas. The share of contaminants in bio-waste from rural areas and single-family urban housing averaged 8.2% and 7.2%, respectively, while multi-family urban housing had a significantly higher average of 16.6%. The primary contaminants identified were treated wood, plastics, mineral wastes, paper, and glass in rural areas and plastics, paper, treated wood, glass, and textiles in urban areas. The close positive correlation found between the total content of pollutants and, in particular, with plastics and kitchen waste in bio-waste collected in rural communities and from multi-family housing in cities indicates that they are likely the main source of the origin of these pollutants. Full article

Municipal biowaste management is at the core of the transition towards a circular bioeconomy in the EU. However, most urban systems are still far from being aligned with these principles. This paper addresses the case of the Metropolitan Area of Barcelona. The current system of biowaste management is compared with a more sustainable alternative scenario. Regulatory and non-regulatory drivers and barriers for the transition from the current state to the alternative scenario are identified and later transformed into policy recommendations using a multi-stakeholder approach. This paper focuses on the separate collection of biowaste and the production of biomethane. Increasing the quantity and quality of separate biowaste collection is a prerequisite for the market-relevant production of biogas from anaerobic digestion that can be converted into biomethane. The results show that more efficient collection systems such as door-to-door or smart bins together with tax incentives such as the pay-as-you-throw principle are key to increasing the amount of collected biowaste, while targeted communication combined with controls and penalties are key to minimizing impurities. In addition to financial incentives for the construction of new anaerobic digestion plants, financial incentive systems are also required for the biomethane sector to ensure competitiveness with fossil fuels. Full article

Recent years have observed a reconstruction of the waste management system from a linear resource flow economy to a circular economy. This approach is reflected in the provisions of the Waste Framework Directive (2018), which introduces, among others, new recycling targets for municipal waste which require, by 2025, 55% of the municipal waste to be recycled, in 2030—60%, and in 2035—65%. The ambitious targets adopted for preparing for the reuse and recycling of municipal waste will not be achieved without a high level of the recycling of bio-waste. This paper studies the quantification of municipal waste and nitrogen in a circular municipal waste management system (MWM) implemented for a city of 100,000. It was assumed that MWM would meet the requirements in terms of EU and Polish circular waste management goal legislation for the years 2025, 2030 and 2035. The research results showed that the development of a separate waste collection will reduce the waste delivered to MBT. The required MBT capacity will decrease by almost 2.4 times. Moreover, it has been shown that the introduction of a closed-loop MWM will result in an almost two-fold reduction in the amount of nitrogen going to the landfill and an increase in the mass of nitrogen that can be used to fertilize the soil (by approximately 22%). Furthermore, it has been shown that the most favorable option for an organic waste treatment is the anaerobic–aerobic process. This solution provides the highest biogas production and the lowest nitrogen gas emissions to air. Full article

By the end of 2023, biowaste must be completely separated or recycled at source, based on EU legislation. Separate biowaste collection and valorisation for biofuels could play an essential role in the biobased circular economy. In this context, the principal goal of this paper was to demonstrate on a pilot scale the technological solution of bioethanol production via the utilisation of urban source-separated biowaste within the city context of Athens, Greece. More specifically, the main aim was the demonstration of a pilot system for more than 10 consecutive operating cycles with real feedstock—wet; separately collected biowaste. From the 11 pilot trials performed with wet feedstock, the mean starch and cellulose degradation of the pilot trials amounted to 80.69 ± 16.27% and 79.41 ± 10.37%, respectively, while the bioethanol yield was 74.05 ± 6.82%. The latter was comparable to that of more intensive pretreatment methods. Homogenization and shredding, which were applied in this study, stand as promising pretreatment methods for bioethanol production from wet feedstock. Further research is needed to optimize conditions and evaluate scalability. Nevertheless, pilot-scale testing is a crucial step in the deployment of this technology since it serves as a bridge between laboratory research and full-scale implementation, offering a practical and controlled environment to validate and optimize the technology while minimizing risks and uncertainties. Conclusively, this study could stand as a flagship case study for the implementation of circular and sustainable approaches in the management of organic fractions of source-separated municipal waste, showcasing the technical feasibility of the whole value chain from waste collection to final bioethanol product recovery. Full article

Bioplastics are frequently utilized in daily life, particularly for food packaging and carrier bags. They can be delivered to biogas plants through a separate collection of the organic fraction of municipal waste (OFMSW). The increased demand for and use of bioplastics aimed at mitigating plastic pollution raises significant questions concerning their life cycle and compatibility with waste management units. Anaerobic digestion (AD) in OFMSW is a valuable resource for biogas production. In this work, the valorization of poly-L-lactic acid (PLLA) composed of food waste within the Biowaste to Bioplastic (B2B) Project framework was studied in laboratory and pilot-scale anaerobic liquid conditions. Taking into account that the addition of PLLA to biowaste can increase biogas production, we performed laboratory-scale anaerobic tests on food waste enriched with different molecular-weight PLLAs produced from food waste or commercial PLLA at a mesophilic temperature of 37 °C. PLLA with the highest molecular weight was subjected to AD on the pilot scale to further validate our findings. The addition of PLLA increased biogas production and had no apparent negative impact on the operation of the reactors used in the laboratory or on the pilot scale. Biogas production was higher when using PLLA with the lowest molecular weight. In the pilot-scale experiments, co-digestion of FW with PLLA increased biogas production by 1.1 times. When PLLA was added to the feed, biomethane was 8% higher, while volatile solids (VS) and total chemical oxygen demand (TCOD) removal were almost the same. Importantly, no effect was observed in the operation of the digesters. Full article

The valorization of bio-waste as a resource for green energy production will be beneficial at a social, economic, and environmental level in different regions. The scope of this research is to develop the energetic valorization of the bio-waste fraction from municipal solid waste, to produce biogas from the anaerobic digestion process and electricity in a biogas CHP process, to increase the penetration of renewables in the electricity production system, with an application of these technologies on islands instead of these waste fractions being transported to other regions. The methodologies developed included: 1. Identification and mapping of resources; 2. State-of-the-art of bio-waste parameters and process solutions; 3. Pilot initiative for separation, collection, and analysis of food waste fractions; 4. Development of process solutions according to resources and needs; 5. Determination of investment, production costs, and revenues of the solution created. The case study selected was Porto Santo Island, with the potential to reduce maritime transportation costs of these undifferentiated waste fractions to Madeira Island and contribute to developing an innovative solution for the energetic valorization of bio-waste, including the participation of the local community. The results demonstrated a production of 272,221 m³ of biogas for use as fuel in a cogeneration unit to transform chemical energy into electrical and thermal energies. Furthermore, the self-consumption of the cogeneration unit is 25% of the total electricity produced and 29% of the total thermal energy produced. In conclusion, this research and solution is in compliance with PNEC, the EU Green Deal, and the European Directive 2018/851, which will make mandatory from 2024: the selective collection of bio-waste, 60% by weight of urban waste to be recycled by 2030, and only 10% of waste to be landfilled by 2035. Full article

To produce a valuable final product from anaerobic digestion (AD), one of the preferred methods of organic recycling, high quality feedstock must be ensured. In this study, separately collected real biowaste (B) was used, consisting of 90% food waste and 10% green waste. The priority issues of AD are both high methane production (MP) and high organics removal efficiency (as organic matter, OM and dissolved organics, and D_COD), which may be improved after pre-treatment. In this study, the effect of hydrothermal pre-treatment (B_HT) and enzymatic additives (B_E) on MP and organics removal from biowaste in mesophilic (37 °C) conditions was analyzed. To assess the adequacy of pre-treatment application, biowaste without treatment (B_WT) was used. Pre-treatment of biowaste prior to AD affected the maximal MP, the removal effectiveness of both OM and D_COD, and the kinetic parameters of these processes. For B_WT, the maximal cumulative MP reached 239.40 ± 1.27 NL/kg OM; the kinetic coefficient of MP (k_CH4) and the initial MP rate (r_CH4) were 0.32 ± 0.02 d⁻¹ and 76.80 ± 1.10 NL/(kg OM·d), respectively. After hydrothermal pre-treatment, the MP of B_HT (253.60 ± 1.83 NL/kg OM) was 6.3% higher than B_WT. However, the highest MP was found for B_E, 268.20 ± 1.37 NL/kg OM; to compare, it increased by 12.1% and 5.5% with B_WT and B_HT, respectively. However, the kinetic parameters of MP were highest with B_HT:k_CH4 0.56 ± 0.02 d⁻¹ vs. 0.32 ± 0.02 d⁻¹ (B_WT) and 0.34 ± 0.02 d⁻¹ (B_E); r_CH4 141.80 ± 0.02 NL/(kg OM·d) (B_HT) vs. 76.80 ± 1.10 NL/(kg OM·d) (B_WT) and 89.80 ± 0.50 NL/(kg OM·d) (B_E). The effectiveness of OM removal was highest with B_E, similarly to the MP with the use of an enzymatic additive. The kinetics of OM removal (r_OM, k_OM) were highest with B_HT, similarly to the kinetics of MP (r_CH4, k_CH4). The highest effectiveness of OM and, consequently, its lowest final content obtained with BE means that the organics were used most efficiently, which, in turn, may result in obtaining a more stable digestive system. Full article

The recycling of bio-waste plays an important role in a circular economy as it transforms bio-waste into a valuable resource (organic fertilizer). However, even separately collected bio-waste can contain some plastic waste, which is usually separated after composting and not before it. Primary studies have confirmed the degradation of plastic during composting, but the release of microplastics from them has not been studied. This article presents a quantification and comparison of the release of microplastics from commonly used plastics during green waste composting. Microplastics were identified by Nile red staining and examination under a fluorescent microscope. Plastic degradation was assessed by weight loss calculation, scanning electron microscope (SEM), and Fourier-transform infrared spectroscopy (FTIR) analysis. On average, 17 to 52 microplastics’ are released from 5-by-5 cm pieces of conventional plastics during composting. The control polylactic acid sample showed the smallest amount of released microplastics: four particles on average. The number of released microplastics depended on the polymer type and thickness of the samples. The results of the current article can be further used for the prediction of microplastic generation and setting a limit on the plastic content in bio-waste Full article

A significant issue is reducing the amount of biological waste that is disposed of in landfills, particularly in high-density residential areas. The Wastes Framework Directive (98/2008), in particular, sets forward the legal requirements for source separation in the European Union’s (EU) environmental legislation. The directive sets a target for separate collection of 10% of the organic waste produced in each municipality by 2030, especially with regard to organic waste. The pilot experience of an integrated biowaste management system that supports source separation and urban composting in an Autonomous Composting Unit (ACU) was presented in this study. The Municipality of Rhodes installed five ACUs in various locations. Used food and green waste are the two types of waste that are deposited in the ACUs. The development of a system for the collection of produced biowaste and its treatment at the source, without producing a nuisance, within an urban area, is the goal of this innovation. Since landfilling of mixed municipal solid waste has long been a common practice on the island of Rhodes, as well as in many other locations of insular and mainland Greece, this technique was introduced as a novel implementation and innovation for the region. The results showed that biowaste source separation was successfully carried out by citizens, resulting in high-purity feed. All ACUs produce compost that is of a standard quality. In accordance with the principles of the circular economy, this study showed that ACUs are a sustainable solution for taking a closed unit approach to the biowaste management problem in urban areas. Full article

The Sustainable Development Goals along with national policies pave the way to a sustainable, circular, and resource efficient development model. The environmental scenario could change with the promotion of biofuels such as bioethanol. Recent research on bioethanol aspires to reduce the costs production, via the optimization of process variables and the increase in ethanol yields. This study presented a stepwise upscaling of bioethanol production from dried source-separated municipal biowaste. Three different scales (250 mL, 4 L, 100 L) were examined applying advanced ethanol production via simultaneous saccharification and fermentation. The bioprocess runs at each of the three scales and produced very similar ethanol yields, indicating excellent scalability. The validated optimum conditions at the pilot scale were 25% solids loading, Spirizyme 40 μL/g starch, NS87014 175 μL/g cellulose, and 2% S. cerevisiae. The results from the pilot trials were very successful and repeatable. Τhe mean ethanol yield was 86.60 ± 4.91%, while the structural component such as starch and cellulose were efficiently hydrolysed. The produced ethanol was recovered and purified meeting the standards of absolute ethanol, rendering it suitable for industrial uses and for biofuel use as well. Energy consumption aspects were discussed as well. Conclusively, all the stages of the value chain for source-separated biowaste valorisation (collection, treatment, added value product recovery) were successfully showcased. Full article

The main problems of the city of Nitra (Slovak Republic) in the field of municipal waste management include: 1. High production of municipal waste per capita; 2. Low rate of its separation; 3. High landfill rate; 4. No opportunity for composting; 5. Establishment of illegal landfills in the city; 6. Low waste prevention rate. To identify the attitudes and opinions of the respondents, and to evaluate certain behavioural practices of the inhabitants of Nitra in the management of municipal solid waste, we used a structured questionnaire (realized in 2020). The results of the questionnaire correspond to the behaviour of 4911 inhabitants of the city (6.46%). This paper evaluates the respondents’ answers, which could be utilised by the local government—not only for a more appropriate setting of municipal waste management and separation, but also in waste prevention and monitoring changes in the consumer behaviour of city residents. The degree of separation in individual housing construction (IHC) and complex housing construction (CHC) was statistically evaluated and compared separately. For paper and glass, a higher degree of separation was reflected in CHC; while conversely, households living in CHC avoided bio-waste and kitchen waste more than IHC households. The most common reason for not participating in the separate collection was the lack of collection containers, the distance of containers from their households, or the low frequency of their collection. The results of the questionnaire show the need for more rigorous education about waste generation, its proper separation, and its prevention. Full article

This paper assesses the potential environmental effects of the optimization of the kitchen waste management in Opole. The separate collection of kitchen waste is improved by distribution of separate collection kits consisting of an in-home bin and 10 L biodegradable bags. The surplus of collected kitchen waste is diverted from treatment in a mechanical-biological pretreatment (MBP) along with the residual waste to anaerobic digestion (AD) with the biowaste. This has positive effects on European and Polish goals, ambitions, and targets, such as (i) increasing the level of renewables in the primary energy supply, (ii) decreasing the level of greenhouse gas (GHG) emissions, (iii) increasing the level of preparation for reuse and recycling of municipal waste. The environmental effects of 1 ton additionally separately collected and treated kitchen waste are determined by using life cycle assessment. It was shown that in all selected impact categories (global warming potential, marine eutrophication potential, acidification potential, and ozone depletion potential) a clear environmental benefit can be achieved. These benefits are mainly caused by the avoided emissions of electricity and heat from the Polish production mix, which are substituted by energy generation from biogas combustion. Optimization of the waste management system by diversion of kitchen waste from mechanical-biological pretreatment to anaerobic digestion can lead to considerable saving of 448 kg CO₂-eq/t of waste diverted. With an estimated optimization potential for the demonstration site of 40 kg/inh·year for the city of Opole, this would lead to 680,000 t CO₂-eq savings per year for the whole of Poland. The sensitivity analysis showed that with a choice for cleaner energy sources the results would, albeit lower, show a significant savings potential. Full article