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Biogas Plant Operation: Digestate as the Valuable Product
Fertilization is an essential element in plant cultivation. Supplying the right amounts of nutrients allows plants to grow and develop. Due to the rising price of mineral fertilizers, other fertilizers and soil conditioners are growing in importance. One of these is the digestate produced in agricultural biogas plants. Due to its properties, the digestate can be used directly as a fertilizer. In this case, the effects of application can both change the soil environment and directly affect plant growth. Physical, biological, and thermal transformations can also produce products based on the digestate or its fractions, which can be successfully used for fertilizer purposes. Among other things, this paper discusses the production and use of composts, biocarbon, and/or fertilizer granules from the solid fraction of the digestate. Numerous scientific studies, including the authorsâ own research in this article, indicate that digestate can be successfully used as fertilizer, both without processing and with selected methods of treatment. However, further research is neededâespecially on the diversity of raw materials used for biogas production and their effects on the composition and performance of the digestate. In addition, research should continue on the processing of digestate into specific products, depending on the needs of soils and plants.
Modern Technologies for Waste Management: A Review
Facing the problem of increasing waste, scientists, foundations, and companies around the globe resulted in ideas and invented technologies to slow down the process. Sources of waste range from industrial waste (e.g., construction and demolition materials, hazardous wastes, ashes) to municipal solid waste (e.g., food wastes, paper, cardboard, plastics, textiles). Modern solutions do not focus only on technological aspects of waste management but also on sociological ones. Thanks to the Internet and social media platforms, scientists can influence ecological consciousness and awareness on a much larger scale. This research was conducted using the search keywords related to modern technologies for waste management. This paper presents a spectrum of selected modern solutions that changed in recent years and how they have impacted waste management. It also discusses challenges and future directions of waste management in the context of the circular economy. The use of modern solutions in waste management allows to achieve selected goals of sustainable development.
Waste as substrates for agricultural biogas plants: A case study from Poland
Energy production from renewable sources is one of the main ways to fight against global warming. Anaerobic digestion process can be used to produce biogas containing methane. In the light of the growing demand for substrates, a variety of raw materials are required. These substrates should be suitable for anaerobic digestion, and processing them need to provide the desired amount of energy. This paper aims to discuss the agricultural biogas market in Poland, its current state, and the possibility of development during energy transformation, in particular in terms of using waste as a substrate for energy production. In February 2022, there were 130 agricultural biogas plants registered in Poland. On the other hand, in 2020, 4,409,054.898 Mg of raw materials were used to produce agricultural biogas in Poland. Among all the substrates used, waste played a special role. With the right amount of raw materials and proper management of a biogas plant, it is possible to produce electricity and provide stable and predictable heat supply. Bearing in mind the development of the Polish and European biogas markets, attention should be paid to ensure access to raw materials from which chemical energy in the form of biogas can be generated. Due to limited access to farmland and the increasing demand for food production, one should expect that waste will be increasingly often used for biogas production, especially that with high energy potential, such as waste related to animal production and the meat industry.
Sustainable Use of Digestate from Biogas Plants: Separation of Raw Digestate and Liquid Fraction Processing
This review provides an overview of the various aspects involved in the digestate separation process with a focus on the best solution. The paper discusses the possibility of processing the liquid fraction using membrane separation processes and evaporation. Despite the identical goal of digestate separation, the solutions presented have many differences. These differences affect each processâs capital, operating costs, efficiency, and complexity. Among the selected solutions, the most popular technology for separating digestate is a screw press. Its advantage is the simplicity of its design compared to the centrifuges or filter presses used. In addition to the economic aspect, a definite advantage of mechanical separation is the possibility of using the liquid fraction to reduce the dry matter of the feedstock for biogas plants. Regardless of the chosen technology, striving for the closed-cycle operation of biogas plants and optimizing production processes is now becoming necessary. Proper management of the digestate is a crucial element of the operational efficiency of any biogas plant in case of the sustainable energy. The prepared article will fill some gaps in knowledge and indicate further directions of action. It is necessary to further develop research on methods of digestate separation.
Selective Collection and Management of Biowaste from the Municipal Sector in Poland: A Review
Municipal waste management is an important aspect in the context of the environmental protection of any country. Biowaste is the dominant stream among all municipal waste in Poland (32.4% in 2020). It can be processed through recycling and recovery processes. It is also possible to dispose of it, although according to the waste hierarchy, such action should be the last option. For biowaste to be recycled, e.g., through anaerobic digestion or composting, it must have suitable properties to be processed through the processes mentioned above. This study aims to discuss the selective collection and management of biowaste from Polandâs municipal sector and identify limiting factors. The paper also indicates selected aspects of possible changes in the waste management sector, considering the role of society and waste management companies. The factors limiting the collection and further use of biowaste from the municipal sector in Poland can be divided into economic, social, technical, and technological. This article refers to the situation in Poland, but some problems occur analogously in other countries. This is because the barriers limiting the selective collection and management of biowaste in many countries are similar and differ mainly in the degree of intensity and the scope they cover. Given the increasingly stringent requirements for waste management, measures must be taken to achieve the legally required levels of recycling of biowaste and to recycle it as well as possible. The development of installations for biological waste management will be crucial.
An Analysis of the Physicochemical and Energy Parameters of Briquettes Manufactured from Sewage Sludge Mixtures and Selected Organic Additives
As a by-product of wastewater treatment, sewage sludge can be used for natural, agricultural, or energy purposes. One method of preparing sludge for management and use is solar drying. To intensify the drying process, natural additives can be used to alter the structure of the sludge and accelerate the evaporation of water. This research aimed to evaluate the influences of different organic additives in sewage sludge mixtures on the physicochemical and energy parameters of briquettes. This research was carried out without thermal boosting in a 4 Ă 2.5 Ă 2 m plastic tunnel. The tunnel was equipped with three drying stations and control and measuring equipment. In two test series, sludge additives in the form of straw and lignocellulosic materials, sawdust, bark, woodchips, and walnut shells, were used. Briquettes were made from the resulting mixtures and then subjected to physical and chemical analyses. This research showed high variability in the contents of trace elements, nitrogen, and sulphur in relation to an increase in the amount of sludge in the briquettes, which, for the briquettes made from sewage sludge, was nearly twice as high as for the briquettes made from the mixtures. The results of the flue gas analysis for the briquettes with sawdust and wood chip additives were very similar. The briquettes made from sewage sludge with lignocellulosic materials (bark and wood chips) had fuel properties similar to woody biomass, with a calorific value and heat of combustion of 15â16 MJ/kg. Fibrous additives (straw) significantly increased the strength parameters of the briquettes, by more than 50% of the value. The compositions and properties of the mixtures affected the following briquetting parameters: temperature and compressive force. The briquettes made from sewage sludge and additives can be classified according to ISO 21640 as SRFs (solid recovered fuels). In most of the results, the net calorific value (NCV) was 3 to 4; the chlorine content (CL) was 2 to 1; and the mercury content (Hg) was 1. The sewage sludge mixtures facilitated the agricultural and energy use of the briquettes.
Application of Post-Flotation Dairy Sludge in the Production of Wood Pellets: Pelletization and Combustion Analysis
The amount and variety of waste increases every year. One of the places where biodegradable waste is generated is the agri-food industry, where it is possible to utilize it for the purpose of energy production. The aim of this research was to determine the possibility of using post-floatation dairy sludge as a raw material for co-pelletization with sawdust. The scope of this work included physical and chemical characterizations of the feedstock, the co-pelletization process, and the combustion of the produced pellets, combined with an exhaust analysis. The obtained values of the pelletsâ density at each level of sludge addition allowed us to conclude that the obtained pellets had a good market quality and constituted a full-fledged, innovative solid fuel, in accordance with the guidelines of the latest, currently applicable ISO 17225 standard. Furthermore, adding ca. 20%wt of sludge to sawdust resulted in a 30% decrease in the pelletization power demand, and still, the combustion characteristics of the pellets met the European Ecodesign emission limitations in terms of the CO and NOx content in the exhaust. The addition of post-flotation dairy sludge to sawdust has a beneficial influence on the production of fuel pellets by decreasing the energy consumption of the pelletization process and improving the pelletsâ kinetic durability. Due to legal requirements and the pursuit of the circular economy principle, one should expect an increased interest in the use of agri-food waste for the production of biofuels.
Anaerobic Digestion and Composting as Methods of Bio-Waste Management
Abstract The management of biodegradable waste from various sectors of economy is an essential element in terms of environmental protection. The paper discusses issues related to the possibility of bio-waste treatment using anaerobic digestion technologies and composting processes, highlighting the conditions for the processes and their advantages and disadvantages. The challenges of overproduction of bio-waste faced by highly developed countries around the world are also presented. Research showed that the anaerobic digestion of this waste combines both biofuel production and a circular economy. The popularity of this method is linked, among others to a low cost of raw materials and wide range of possible uses for biogas (i.e. electricity, heat, or biomethane). In addition, an alternative bio-waste management option, compost production, was discussed. The study aimed to compare anaerobic and aerobic bio-waste management processes.
Profitability of the agricultural biogas plants operation in Poland, depending on the substrate use model
Hemp Biomass as a Raw Material for Sustainable Development
Hemp cultivation is becoming increasingly common worldwide, although it still raises many concerns. These plants are gaining popularity due to their versatility and the ability to use virtually every part of them in almost all economic branches. Hemp products are sought after and appreciated by consumers. The cultivation of hemp does not place a large burden on the environment. All this makes hemp an ideal plant in terms of land use, which is closely related to the idea of sustainable development. This paper describes the legal aspects of hemp cultivation in Europe and briefly presents its breeding and cultivation. The possibilities of their versatile use are presented, with particular reference to biofuel production. Moreover, the suitability for ecological cultivation, description of the economic and social aspects of industrial hemp cultivation, as well as future outlooks, are also described.
Digestate as a Source of Nutrients: Nitrogen and Its Fractions
Due to fossil-fuel-limitation constraints, new energy sources are being sought. On the other hand, organic fertilizers that can be used in agriculture are increasingly being sought. One of the renewable energy sources is biogas produced from substrates large in organic matter. Apart from biogas, the product of the anaerobic digestion process is digestate. Due to the high content of nutrients, mainly nitrogen, this product can be successfully used as a fertilizer. This study aims to determine the content of total nitrogen (Ntot) and its selected fractions in the raw and processed digestate from agricultural biogas plants. The nitrogen fractions included N-NH4, N-NO3, and Norganic. The total nitrogen content (Ntot) and its fraction in raw digestate were determined. Samples used for the research came from five agricultural biogas plants. Separation into liquid and solid fractions is one of the methods for digestate management. The nitrogen content in selected samples obtained after separation of digestate in a biogas plant and on a laboratory scale was also checked. The obtained results show that digestate from agricultural biogas plants is a nitrogen-rich fertilizer. The content of Ntot in the tested samples ranged from 1.63 gâkgâ1 to 13.22 gâkgâ1 FM. The N-NH4 content in the analyzed material ranged from 0.75 to 4.75 gâkgâ1 FM. The determined physical and chemical properties confirm that the raw and processed digestate is characterized by appropriate fertilization properties, with particular emphasis on the content of Ntot and the share of its mineral forms. Based on the chemical composition, digestate from agricultural biogas plants can be considered a multi-component fertilizer.