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Reducing the phenomenon of food waste and effective management of already wasted food in the form of post-consumer waste, included in the source-separated organic fraction of municipal solid waste (SS-OFMSW) from households and catering facilities, are some of the key challenges of the circular economy (CE), in particular in highly urbanized areas. The basis for the effective use of this waste is the knowledge of its physical and chemical properties. The main objective of the paper is to identify the key technological and organizational parameters for selective collection determining the characteristics of the SS-OFMSW and, consequently, the optimal path for its management. This paper presents the results of qualitative research of SS-OFMSW generated in the capital of Poland—Warsaw—coming from three sources: multi- and single-family housing and catering facilities. The collection efficiency of this waste was determined in the form of quality in container rate (QCR = 92–97%) and variability in terms of impurities and admixtures present in it (CV = 56–87%). High variability indicates that the system of selective waste collection in Warsaw is immature, which may hinder undertaking activities in the field of waste management planning. The study confirmed the suitability of the tested SS-OFMSW for organic recycling, especially using anaerobic digestion (AD), to which it is predisposed by water content, C/N, and biomethane potential (BMP). All tested food waste is characterized by a high yield of biogas in the range of 384–426 m3/Mg VS and an average share of methane in biogas at the level of 52–61%. Fertilizer properties, moisture, and its gas potential show little variability (CV ≤ 16%), which means that these data can be treated as stable data. The obtained results indicate the optimal direction for the collection and processing of SS-OFMSW based on post-consumer food waste in urbanized areas. [ABSTRACT FROM AUTHOR]

As the global demand for renewable energy continues to rise, biogas production has emerged as a promising solution for sustainable energy generation. This review article presents the advantages of biogas technologies (mainly agricultural, based on waste of animal and plant origin) and extensively discusses the main principles of biogas production in the anaerobic digestion (AD). In this respect, the main parameters of the process, which require monitoring and decisive for its efficiency are described, therefore: temperature, pH value, retention time and organic loading rate (OLR). The principles of substrate selection are also discussed and the necessity and advantages of the use of organic waste according to the model of a circular economy and the concept of sustainable development, are indicated. It is emphasized that according to the new European regulations, the crops classified as food cannot be considered energy crops. The part on biogas production is summarised with an explanation of the necessity to treat and purify biogas. Biogas purification is important from the point of view of the efficiency of its conversion into electricity. A special place in this paper is devoted to the design, construction, functioning and operation of biogas plants, based on both scientific and practical aspects. In conclusion of this chapter, the economic aspects and profitability of operating biogas plants are discussed. Cost and benefit analyses are the major tool used for the systematic evaluation of the financial costs and potential benefits associated with the operation of biogas plants. The important fact is that the return on investment can be achieved within a few years, provided the activities are well-planned and executed. In addition to the fundamental issues of the operation of biogas plants, this article presents the global situation regarding the development of biogas plants, discussing in detail the specific needs and limitations on different continents. It is a interesting and extensive part of this article. The global agricultural biogas market is at very different levels of development. Most such installations are located in Asia and Europe. China has the highest number of biogas plants, with more than 100,000 biogas plants, followed by Germany with over 10,000 plants. In addition to the 100,000 biogas plants, China also has a large number of household biogas units, which gives a total of approx. 40 million operating units. The article concludes with a discussion of opportunities and barriers to the development of biogas plants, pointing to: financial issues, access to feedstock, political regulations, public awareness and the geopolitical situation. The most frequently cited reasons for investment failure include economic problems, lack of professional knowledge. [ABSTRACT FROM AUTHOR]

Hydrogen is widely considered as the fuel of the future. Due to the challenges present during hydrogen production using conventional processes and technologies, additional methods must be considered, like the use of microorganisms. One of the most promising technologies is dark fermentation, a process where microorganisms are utilized to produce hydrogen from biomass. The paper provides a comprehensive overview of the biological processes of hydrogen production, specifically emphasizing the dark fermentation process. This kind of fermentation involves bacteria, such as Clostridium and Enterobacterium, to produce hydrogen from organic waste. Synthetic microbial consortia are also discussed for hydrogen production from different types of biomasses, including lignocellulosic biomass, which includes all biomass composed of lignin and (hemi)cellulose, sugar-rich waste waters, and others. The use of genetic engineering to improve the fermentation properties of selected microorganisms is also considered. Finally, the paper covers the important aspect of hydrogen management, including storage, transport, and economics. [ABSTRACT FROM AUTHOR]

The Adrar region (Algeria) has a total of 397,800 date palm trees (Phoenix dactylifera L.). Due to annual palm cleaning, large quantities of lignocellulosic biomass are produced. Depending on the variety, an average of 65 kg of biowaste is obtained per palm tree. Since the value of this biowaste is underrated, most of the palms are burned outdoors, causing air and visual pollution. This work explores the gasification potential of lignocellulosic waste from date palms (Phoenix dactylifera L. Takarbouche variety) into useful energy. The technology investigated is air updraft fixed-bed gasification, thanks to an originally designed and built reactor, with the capability to process 1 kg of feedstock. Four types of palm waste—namely, palms, petioles, bunch, and bunch peduncles—are first characterized (bulk density, proximate analysis, fixed carbon, elemental composition, and calorific value) and then used as feedstock for two gasification tests each. The syngas produced for the four date palm wastes is combustible, with an outlet temperature between 200 and 400 °C. The operating temperature inside the gasifier varies according to the feature of the biomass cuts (from 174 °C for the peduncles to 557 °C for palms). The experimental setup is also equipped with a cyclone, allowing for the recovery of some of the tar produced during the tests. Finally, the results show that the residence time has a positive effect on the conversion rate of date palm waste, which can significantly increase it to values of around 95%. [ABSTRACT FROM AUTHOR]

Energy and environmental issues are of great importance in the present era. The transition to renewable energy sources necessitates technological, political, and behavioral transformations. Hydrogen is a promising solution, and many countries are investing in the hydrogen economy. Global demand for hydrogen is expected to reach 120 million tonnes by 2024. The incorporation of hydrogen for efficient energy transport and storage and its integration into the transport sector are crucial measures. However, to fully develop a hydrogen-based economy, the sustainability and safety of hydrogen in all its applications must be ensured. This work describes and compares different technologies for hydrogen production, storage, and utilization (especially in fuel cell applications), with focus on the research activities under study at SaRAH group of the University of Naples Federico II. More precisely, the focus is on the production of hydrogen from bio-alcohols and its storage in formate solutions produced from renewable sources such as biomass or carbon dioxide. In addition, the use of materials inspired by nature, including biowaste, as feedstock to produce porous electrodes for fuel cell applications is presented. We hope that this review can be useful to stimulate more focused and fruitful research in this area and that it can open new avenues for the development of sustainable hydrogen technologies. [ABSTRACT FROM AUTHOR]

Industrial human activity has led to the release of substantial amounts of heavy metals into the environment. Contamination of water with heavy metals such as lead, cadmium, copper, zinc, chromium, or nickel represents a serious problem. As part of the circular economy, it is appropriate to use biowaste from agriculture, fisheries, and the timber industry as biosorbents. In this literature review, the potential of using these biowaste groups as biosorbents for metal removal is presented. This biowaste is characterized by the presence of carboxyl, hydroxyl, carbonyl, amide, amine, sulfydryl, and other groups on their surface, which form complexes and chelates with metals present in water. Biosorption seems to be a potential alternative to conventional technologies for removing or recovering heavy metals from water or wastewater, which are uneconomical and generate additional waste. The paper demonstrates that harnessing the potential of biowaste to remove metals is beneficial to the environment as they can solve the problem of incineration and realise recycling that meets the circular economy. Although the choice of a suitable biosorbent for the removal of a particular metal involves a lot of research, the high biosorption efficiency, low cost, and renewability justify their use. [ABSTRACT FROM AUTHOR]

Biowaste management is at the center of attention in recent years due to the increased focus on Circular Economy practices. Lesvos has numerous food processing facilities and olive mills, and therefore Olive Mill Wastewater (OMWW) is a wastewater stream that requires attention. In this study, a holistic experimental set-up that combines aerobic and anaerobic treatment strategies was developed taking into consideration the hydrothermal carbonization of AD digestate along with locally available OMWW. The study focuses on the hydrothermal carbonization (HTC) of anaerobic residues from biogas production, and food waste was co-utilized with spent coffee grounds (SCG). The reduced volatile solids of SCG have some effects on the final products. AD produced methane yields of 54.7% for the food waste and 52.4%. for the feedstock with added SCG. At the same time, the feedstock that contained SCG produced more hydrochar that reached up to 50% of the yield. Hydrothermal carbonization in a water medium produced liquids with basic pH values around 8 and conductivities of 4–5 mS/cm, while the samples that were treated in OMWW medium had pH values close to 5.5 and conductivities of around 12 mS/cm. The produced hydrochars have significant calorific values that exceeded 20 MJ/kg for almost all the samples. Overall, HTC with OMWW as a medium was able significantly reduce the COD of OMWW while resulting in hydrochars with increased heating values. [ABSTRACT FROM AUTHOR]

The production of biogas from biodegradable waste generated in all sectors of the economy in Poland is a key issue for the diversification of energy sources and climate neutrality. The biogas balances presented in the literature based on bio-waste often contain overly optimistic data, which in reality only represent the theoretical potential of biogas in Poland. The pragmatic approach presented in this study fills a gap in research by presenting a technical balance of biogas (real potential) that can be realistically achieved. The objective of the work was to perform a biogas balance in the context of electricity and heat generation in cogeneration units. The tests made it possible to estimate the technical potential of biogas, depending on the source of its generation, the possibility of its conversion to biomethane and biohydrogen and the methods of its use. The research results showed a 30% increase in biogas potential on an annual basis compared to the current state, resulting in a 29% increase in electricity production and a 28% increase in heat production. The technical potential of biogas was estimated at 2186.62 million m3, which would allow for the production of 4627.06 GWh of electricity and 1869.64 TG of heat. The technical balance of biogas and the potential energy production can serve as input material for developing plans and strategies for the development of renewable energy sources in Poland. The work is consistent with the issues of balancing the renewable energy resources from biogas and the methods of conversion into other energy carriers using sustainable energy transformations in order to optimise energy production processes. [ABSTRACT FROM AUTHOR]

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 DCOD), which may be improved after pre-treatment. In this study, the effect of hydrothermal pre-treatment (BHT) and enzymatic additives (BE) 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 (BWT) was used. Pre-treatment of biowaste prior to AD affected the maximal MP, the removal effectiveness of both OM and DCOD, and the kinetic parameters of these processes. For BWT, the maximal cumulative MP reached 239.40 ± 1.27 NL/kg OM; the kinetic coefficient of MP (kCH4) and the initial MP rate (rCH4) were 0.32 ± 0.02 d−1 and 76.80 ± 1.10 NL/(kg OM·d), respectively. After hydrothermal pre-treatment, the MP of BHT (253.60 ± 1.83 NL/kg OM) was 6.3% higher than BWT. However, the highest MP was found for BE, 268.20 ± 1.37 NL/kg OM; to compare, it increased by 12.1% and 5.5% with BWT and BHT, respectively. However, the kinetic parameters of MP were highest with BHT:kCH4 0.56 ± 0.02 d−1 vs. 0.32 ± 0.02 d−1 (BWT) and 0.34 ± 0.02 d−1 (BE); rCH4 141.80 ± 0.02 NL/(kg OM·d) (BHT) vs. 76.80 ± 1.10 NL/(kg OM·d) (BWT) and 89.80 ± 0.50 NL/(kg OM·d) (BE). The effectiveness of OM removal was highest with BE, similarly to the MP with the use of an enzymatic additive. The kinetics of OM removal (rOM, kOM) were highest with BHT, similarly to the kinetics of MP (rCH4, kCH4). 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. [ABSTRACT FROM AUTHOR]

The increase in the amount of municipal solid waste (MSW) generated, among other places, in households is a result of the growing population, economic development, as well as the urbanisation of areas with accompanying insufficiently effective measures to minimise waste generation. There are many methods for treating municipal waste, with the common goal of minimising environmental degradation and maximising resource recovery. Biodegradable waste, including selectively collected biowaste (BW), also plays an essential role in the concept of the circular economy (CE), which maximises the proportion of waste that can be returned to the system through organic recycling and energy recovery. Methane fermentation is a waste treatment process that is an excellent fit for the CE, both technically, economically, and environmentally. This study aims to analyse and evaluate the problem of odour nuisance in municipal waste biogas plants (MWBPs) and the impact of the feedstock (organic fraction of MSW-OFMSW and BW) on this nuisance in the context of CE assumptions. A literature review on the subject was carried out, including the results of our own studies, showing the odour nuisance and emissions from MWBPs processing both mixed MSW and selectively collected BW. The odour nuisance of MWBPs varies greatly. Odour problems should be considered regarding particular stages of the technological line. They are especially seen at the stages of waste storage, fermentation preparation, and digestate dewatering. At examined Polish MWBPs cod ranged from 4 to 78 ou/m3 for fermentation preparation and from 8 to 448 ou/m3 for digestate dewatering. The conclusions drawn from the literature review indicate both the difficulties and benefits that can be expected with the change in the operation of MWBPs because of the implementation of CE principles. [ABSTRACT FROM AUTHOR]