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Food Waste to Energy through Innovative Coupling of CHP and Heat Pump
Jan Drofenik, Danijela Urbancl, Darko Goričanec, Zdravko Kravanja, Zorka Novak-Pintarič, 2023, original scientific article

Abstract: This paper presents the conceptual design of a technological solution for the efficient conversion of food waste into heat and power. The distribution and composition of food loss and waste at different stages of the food supply chain in Slovenia and their potential for biogas production were determined. It was found that more than 50% of food waste comes from households. Therefore, a small plant was designed to convert food waste into biogas, which was innovatively coupled with a combined heat and power (CHP) unit and a heat pump. This doubles the amount of heat generated compared to conventional cogeneration. Based on the capacity of a micro commercial CHP unit, 3330 households (about 8000 residents) would supply food waste. The heat generated could replace 5% of the natural gas used for domestic water heating. The payback period would be 7.2 years at a heat price of about 80 EUR/MWh, however, for municipalities with more than 40,000 inhabitants the payback period would be reduced to less than 3 years. The cost price of the heat generated by this system would be about 25 EUR/MWh, taking into account the government subsidy for the operation of the CHP unit.
Keywords: food waste to energy, biogas, combined heat and power, CHP, heat pump, efficiency, conceptual design, preliminary economic assessment, sensitivity analysis
Published in DKUM: 16.02.2024; Views: 3184; Downloads: 18
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Investigating Winter Temperatures in Sweden and Norway : Potential Relationships with Climatic Indices and Effects on Electrical Power and Energy Systems
Younes Mohammadi, Aleksey Palstev, Boštjan Polajžer, Seyed Mahdi Miraftabzadeh, Davood Khodadad, 2023, original scientific article

Abstract: This paper presents a comprehensive study of winter temperatures in Norway and northern Sweden, covering a period of 50 to 70 years. The analysis utilizes Singular Spectrum Analysis (SSA) to investigate temperature trends at six selected locations. The results demonstrate an overall long-term rise in temperatures, which can be attributed to global warming. However, when investigating variations in highest, lowest, and average temperatures for December, January, and February, 50% of the cases exhibit a significant decrease in recent years, indicating colder winters, especially in December. The study also explores the variations in Atlantic Meridional Overturning Circulation (AMOC) variations as a crucial climate factor over the last 15 years, estimating a possible 20% decrease/slowdown within the first half of the 21st century. Subsequently, the study investigates potential similarities between winter AMOC and winter temperatures in the mid to high latitudes over the chosen locations. Additionally, the study examines another important climatic index, the North Atlantic Oscillation (NAO), and explores possible similarities between the winter NAO index and winter temperatures. The findings reveal a moderate observed lagged correlation for AMOC-smoothed temperatures, particularly in December, along the coastal areas of Norway. Conversely, a stronger lagged correlation is observed between the winter NAO index and temperatures in northwest Sweden and coastal areas of Norway. Thus, NAO may influence both AMOC and winter temperatures (NAO drives both AMOC and temperatures). Furthermore, the paper investigates the impact of colder winters, whether caused by AMOC, NAO, or other factors like winds or sea ice changes, on electrical power and energy systems, highlighting potential challenges such as reduced electricity generation, increased electricity consumption, and the vulnerability of power grids to winter storms. The study concludes by emphasizing the importance of enhancing the knowledge of electrical engineering researchers regarding important climate indices, AMOC and NAO, the possible associations between them and winter temperatures, and addressing the challenges posed by the likelihood of colder winters in power systems.
Keywords: winter temperatures, biogas, Atlantic Meridional Overturning Circulation, AMOC, weaking, NAO, North Atlantic Oscillation, SSA, Singular Spectrum Analysis, electrical power and energy systems
Published in DKUM: 15.02.2024; Views: 275; Downloads: 18
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Production of biogas by CSF technology
Maša Knez Marevci, Mojca Škerget, Željko Knez, 2016, original scientific article

Abstract: Hydrogen is expected to become an important fuel in the long-term since in combination with fuel cells it offers the opportunity of an intrinsically clean energy supply. By application of supercritical water gasification (SCWG) concept, sustainable hydrogen can be produced from biomass and waste. The paper offers an overview of some recently published papers dealing with SCWG of model compounds and a summary of the investigations on SCWG of real agricultural and food processing wastes. In the frame of our work an intense research was performed to support analyses of SCWG of glycerol and was supported by the investigation of phase equilibrium for the systems gas/water and gas mixtures/water. When glycerol/water solutions were directly injected in the reactor operating at supercritical conditions, gases with high C2+ were obtained by the reforming in supercritical water unit. To reduce the hydrocarbon concentrations and to obtain a syngas with higher CO/CO2 ratios from a mixture of gases (H2, CO, CO2 and CH4), catalytic reactions at high pressure and temperature were introduced reflecting in an increase of the content of H2 and CO. Solubility measurements were conducted for the binary systems of gas and water at elevated pressures and temperatures.
Keywords: biogas, SCF technology, biotechnology
Published in DKUM: 19.07.2017; Views: 1049; Downloads: 198
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Biogas as a renewable energy source
Matjaž Ošlaj, Bogomir Muršec, 2010, review article

Abstract: Renewable energy technology does not simply produce energy, heat and transport fuel, but also offers the opportunity to live in the footsteps of a reasonable future development. In Europe and other industrialized regions, the main reason for the development of renewable energy is the environment, in particular the concern in relation to global climate change and the need to improve security and diversity of energy supply. In the developing countries, they promise a new hope for renewable primary energy supply in regions without conventional energy and provide an opportunity for sustainable development. Productionof "green energy" from biogas, which is among the renewable energy sources, promises an environmentally less damaging way of obtaining energy by reducing CO emissions into the environment and reduces energy dependence on imported energy sources. Biogas production is of major importance for the sustainable use of agrarian biomass as renewable energy source.
Keywords: anaerobic digestion, biogas, manure, renewable energy
Published in DKUM: 11.07.2017; Views: 1696; Downloads: 106
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Process reengineering and innovation of remaking soapsuds
Andreja Verbič, Tomaž Kern, Drago Vuk, 2009, original scientific article

Abstract: This article uses a business process renovation method to address an environmental protection problem. The presented case, studied in factories which remake crude vegetable oil (soapsuds remake), focuses on reengineering one of the business processes which is classified as an obligatory process. This process has to be performed to comply with the requirements of the existing ecology legislation. Therefore, it is reasonable to take a radical approach - business process reengineering. Soapsuds with oil remnants are a secondary product in the vegetable oil refining process. According to the legislation, secondary products as waste are not acceptable for the environment. Soapsuds remake as it is currently carried out produces technical fatty acids and, as a side product, calcium sulphate. Calcium sulphate is listed as special waste; therefore it must be deposited in a special waste landfill site. In the course of searching for a solution to this ecological problem, a new idea came up, namely that soapsuds are taken to the biogas plant. At the biogas plant, they can be decomposed into biogas, which is then used to generate electric energy, for heating or to supplement municipal gas. Thus, the reengineering of the process is upgraded into process innovation and environmental innovation. Using data obtained from the available literature, we managed to prove that process reengineering, which is simultaneously process innovation and ecological innovation, can be applied in practice. Side products resulting from the anaerobic digestion of soapsuds in the biogas plant comply better with the requirements of the Slovenian ecological legislation than those occurring in the process used up to now.
Keywords: business process reengineering, process innovation, soapsuds remake, biogas plant, ecology
Published in DKUM: 10.07.2015; Views: 1385; Downloads: 353
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A Multi-criteria assessment of energy crops for biogas production
Peter Vindiš, Bogomir Muršec, Črtomir Rozman, Franc Čuš, 2010, original scientific article

Abstract: This paper presents the system for the assessment of energy crops for biogas production. The system is based on simulation modelling and multi criteria decision analysis. The deterministic simulation system consists of deterministic production simulation models that enable different types of costs calculations for the production of energy crops, electrical and heat energy in biogas production. Simulation model results were further evaluated using a qualitative multi-attribute modelling methodology (supported by the software tool DEX-i) and quantitative analytical hierarchical process - APH (supported by software toll Expert Choice 2000). The Analysis showed that by using current model the most relevant alternative used for energy crop for biogas production is maize. The maize results in the best multicriteria evaluation EC=0.248 and DEX-i evaluation = appropriate. the best alternative for maize is sorghum with multicriteria evaluation of EC=0.201 and DEX-i evaluation = less appropriate.
Keywords: simulation model, Expert Choice, AHP, DEX-i, energy, crops, biogas
Published in DKUM: 10.07.2015; Views: 1327; Downloads: 41
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Determination of oxygen by means of a biogas and gas - interference study using an optical tris (4,7-diphenyl-1,10-phenanthroline) ruthenium(II) dichloride complex sensor
Polonca Brglez, Andrej Holobar, Aleksandra Pivec, Nataša Belšak, Mitja Kolar, 2012, original scientific article

Abstract: Biogas is a mixture of gases produced by anaerobic fermentation where biomass or animal waste is decomposed and methane and carbon dioxide are mainly released. Biogas also has a very high moisture content (up to 80%), temperatures of around 60 °C, high pressure, and can contain other gases ($N_2$, $H_2S$, $NH_3$ and $H_2$). We searched for an appropriate measuring system for the determining of oxygen in biogas, since the production process of biogas must be run under anaerobic conditions; as the presence of oxygen decreases the quality of the biogas. Ruthenium (II) complexes are by far the most widely-used oxygen dyes within optical oxygen sensors. In general, they have efficient luminescences, relatively long-life metal-ligand charge-transfer excited states, fast response times, strong visible absorptions, large Stokes shifts, and high-photochemical stability. The purpose of this work was to characterise and optimize an optical oxygen sensor using tris (4,7-diphenyl-1,10-phenanthroline) ruthenium(II) dichloride complex for measuring oxygen. Different sensor properties were additionally studied, focusing on the interference of external light, temperature, and various gases. A special gas-mixing chamber was developed for gas interference study, and online experiments are presented for oxygen determination within the pilot biogas reactor.
Keywords: tris(4, 7-diphenyl-1, 10-phenanthroline)ruthenium(II) dichloride complex, oxygen optical sensor, interferences, biogas
Published in DKUM: 01.06.2012; Views: 2233; Downloads: 112
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