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Biomass is the renewable energy resource that contributes to the energy balance by conversion into heat, by combustion in specialized facilities, conversion into electricity based on steam or gas obtained that drives turbines and electric generators or in both cases combined, through the cogeneration process. However, in order to be collected from nature, it must be optimally organized so that the effects on the environment are not harmful. Also, in the conversion processes, polluting emissions must be as low as possible, for this reason the combustion plants must be gasified and equipped with particulate filters on the exhaust circuit of gases, smoke and ash treatment. The contribution of urban biomass, plant or animal, is significant and the collection must be selective. These are basic aspects dealt with in the work and through the use and therefore the optimal management of biomass, ecological energy objectives can be achieved. Biomass is a renewable energy resource that contributes to the energy balance through conversion into heat, through combustion in specialized installations, conversion into electricity based on steam or gases obtained that drive turbines and electric generators or in both cases combined, through the cogeneration process. However, in order to be collected from nature, it must be optimally organized so that the effects on the environment are not harmful. Also in the conversion processes, polluting emissions must be reduced as much as possible, for this reason the combustion installations must be with gasification and equipped with particle filters on the gas, smoke and ash exhaust circuit. The contribution of urban biomass, whether vegetable or animal, is significant and the collection must be selective. These are basic aspects treated in the paper and through the use and therefore optimal management of biomass, ecological energy objectives can be achieved.
ABSTRACT
Biomass is the renewable energy resource that contributes to the energy balance by conversion into heat, by combustion in specialized facilities, conversion into electricity based on steam or gas obtained that drives turbines and electric generators or in both cases combined, through the cogeneration process. However, in order to be collected from nature, it must be optimally organized so that the effects on the environment are not harmful. Also, in the conversion processes, polluting emissions must be as low as possible, for this reason the combustion plants must be gasified and equipped with particulate filters on the exhaust circuit of gases, smoke and ash treatment. The contribution of urban biomass, plant or animal, is significant and the collection must be selective. These are basic aspects dealt with in the work and through the use and therefore the optimal management of biomass, ecological energy objectives can be achieved.
Biomass is a renewable energy resource that contributes to the energy balance through conversion into heat, through combustion in specialized installations, conversion into electricity based on steam or gases obtained that drive turbines and electric generators or in both cases combined, through the cogeneration process. However, in order to be collected from nature, it must be optimally organized so that the effects on the environment are not harmful. Also in the conversion processes, polluting emissions must be reduced as much as possible, for this reason the combustion installations must be with gasification and equipped with particle filters on the gas, smoke and ash exhaust circuit. The contribution of urban biomass, whether vegetable or animal, is significant and the collection must be selective. These are basic aspects treated in the paper and through the use and therefore optimal management of biomass, ecological energy objectives can be achieved.
Keywords: biomass, urban waste, selective collection, energy conversion.
INTRODUCTION
Biomass is the first and most important form of energy used by man since the discovery of fire. It is the most abundant renewable resource on the planet, a fuel derived from plants and animals. It is used for both heat and electricity production or converted into biofuels (biodiesel and biogas)[1][3].
Bioenergy plays a central role in national action plans in European countries: it is estimated that more than half of the energy targets (energy produced from renewable sources) set more recently by the 2030 Strategy with a 2050 perspective can be provided by bioenergy; however, the real benefits on environmental factors can only be highlighted through the sustainable use of existing sources, the use of appropriate technologies and the development of new systems, adapted to local conditions. Biomass 1s obtained from waste and residues from agriculture, forestry and related industries, as well as from industrial and urban waste, or from specially intended energy crops, but in order to be a source of energy, it must go through a series of transformations. They are distributed throughout the chain: extraction-collection - transport - selection - treatment, storage - use.
The paper has two representative case studies that took place over several months. Two situations were followed through these studies. The first refers to the way of selective waste collection in several territorial units with the collection and selection center in the municipality of Beius in Bihor County. The second situation refers to the monitoring of the consumption of vegetable wood waste for a wood pellet factory and the performance of its energy balance . The factory is also located in the vicinity of the city of Beius, namely in the town of loanis. The factory is a prosumer because it also owns a gas turbine generator that produces electricity for its own consumption and the supply is transferred to the public electricity network and therefore it can be said that it is a local energy objective, following both directions pursued in the work on biomass management: selective collection and energy recovery. The factory also produces thermal energy necessary for heating and treatment-drying of biomass. The results will be presented synthetically in the paper due to lack of graphic space.
About biomass management
One of the aspects worth taking into account in optimizing waste management is the selective collection of waste within localities or where, in external industrial areas, quantities worthy of consideration are produced, due to anthropogenic activities. Imposed as mandatory by OG 74/2018, this activity leads, in the context of the work, to the easy selection in order to recover organic waste from food and paper and cardboard. Many local or county public administrations in the country have gone so far as to carefully select household waste into four categories. For example, in the city of Oradea, it is collected in dedicated containers, as follows: plastic/metal in yellow containers; paper/cardboard - blue; glass - green; residual waste - black; However, there are also situations with collection on five levels (fractions).
Our country's approach to waste management is in line with the European Union's policy and is based on three major principles[6][7]:
* Waste prevention - a factor considered extremely important within the original waste management strategy, directly related to the improvement of production methods as well as to the determination of consumers to change their demand for products (orientation towards organic products) and to approach a lifestyle that generates reduced quantities of waste
* Selective collection, recycling and reuse - where waste is generated, encouraging a high level of recovery of component materials. In this regard, several waste streams are identified for which material recycling is proritory: packaging, end-of-life vehicles, used batteries, waste from electrical and electronic equipment;
* Improved final waste disposal and monitoring - if waste cannot be recovered, it must be disposed of in a safe environment and human health, with a strict control programme
At the level of Bihor County, the Project "Integrated waste management system in Bihor County" was adopted, initiated by the Bihor County Council and implemented by the Intercommunity Development Association Ecolect Group, which carries out waste management throughout the territory.
From the point of view of energy recovery, biomass is used in the final inheritance processes, in boiler fires or by farming, transforming into biofuels. As the latter form of recovery consists of gaseous and liquid states of aggregation, it follows that biomass is used in all three states.
The potential of biomass
Romania has a rich potential for biomass in its solid natural state, such as forests and agricultural crops. There are also crops specially used for energy purposes, consisting mainly of herbaceous or woody plants with a high degree of regeneration.
This is the case with Sudan grass, elephant grass or energy willow species[4][5]. The biomass potential by sorts, regions and total is presented in Table 1[11]. The evaluation of the potential of some energy resources is a prerequisite in making the decision on the development of a project in the field. Information about the potential can be obtained either through direct investigation and measurements of those involved, or through the study of the results and databases published by other specialists who do not participate directly in the implementation of the project.
For Romania, data on the potential of biomass can be obtained by consulting maps published in various reports or books, but also the online platforms of institutions involved in the evaluation of renewable energy sources.
For the case of Bihor County, data on the potential and type of biomass were extracted and processed, from maps and records of the National Institute of Statistics. The results are shown in the following figure:
Directions of biomass energy recovery
The sections of greatest interest at present are:
* Direct combustion in boilers.
* Advanced thermal conversion of biomass into a secondary fuel, by thermal gasification or pyrolysis, followed by the use of the fuel in an engine or turbine.
* Biological conversion to methane through aerobic bacterial digestion.
* Chemical and biochemical conversion of organic matter into hydrogen, methanol, ethanol or diesel fuel.
Boiler combustion is the most widespread biomass energy use technology. The types of boilers for burning wood biomass are very varied and could be
but the most common are boilers with grated fireboxes and boilers with push-in fires underneath. Biomass gasification is a process of complete conversion into gas, using air, oxygen or steam as the gasification medium. Biomass gasification is carried out by two main methods: thermal gasification using air, oxygen, steam or their mixture at temperatures of about 700% biochemical gasification using micro-organisms at room temperature and under anaerobic conditions. For the gasification of wood, three main types of gasification reactors have been developed and applied: fixed bed gas generators, fluidized bed gas generators and upward current gas generators. Systems for the production of electricity based on biomass conversion are achieved through the following technologies: steam turbine, gas turbines, internal combustion engine and Stirling engine.
Biomass waste management. Case study
In the current chapter, a case analysis is made regarding the selective collection, selection and storage of household waste, as part of biomass management in localities. The study was carried out following the data of the collection company from household consumption and sociomunicipal institutions for several localities in the vicinity of Beius municipality (10667 inhabitants) and including this one. The localities in question form a local administration association and belong to the following communes: Drägänesti (2967 inhabitants), Tárcaia (1969 inhabitants), Finis (3680 inhabitants), Pocola (1571 inhabitants), Remetea (3153 inhabitants), Curatele (2509 inhabitants). The final selection, packaging and intermediate storage is done in the sorting station in Beius. Images from inside the station are shown in Figure 2. The collection in the localities is done by the AVE company, with its own logistics. Each locality has established a time interval and a day in which the inhabitants must evacuate the waste generated, by assortment so that the sanitation company.
For the analyzed localities, four periods of analysis of waste production were established at the beginning, each period comprising three months, broken down as follows: period 1: June, July, August 2020, period 2: September, October, November 2020; Period 3:
December 2020, January, February 2021; Period 4: March, April, May 2021. The results obtained are highlighted, for two localities, in the following figures: collect them optimally.
Another part of the analysis is the identification of the quantities of biodegradable waste collected by the AVE Beius division from the total forms of waste sorted. In this regard, statistical processing has been drawn up, which is partially presented in figures 4-7. The graphs show the proportions of various types of waste for the period September 2020= May 2021.
Energy analysis of biomass conversion
From the analyzed region, the study was carried out at the Ioanis Sawmill, Pellets and Briquettes belonging to the Ecoforest S.A. holding, which has a national expansion. The factory is located on the administrative territory of Finis commune, in the vicinity of the village of loanis, Bihor County.
Pictures of the factory are shown in Figures 4.7 (exterior) and 4.8 (interior). The factory has 47 employees and the work is carried out on a single standardized shift of 8 hours five days a week. From an electrical point of view, the factory is powered by its own transformer substation , With two transformers with Sn = 2 x 400 КУА, Un = 20/0.4 kV connected to the regional EEA through a 20 kV OHL. The factory produces timber, residual wood pellets and deciduous materials, depending on the season or season, and wooden knives, in mixed composition or by wood categories, of hard wood such as oak, acacia and holm oak or of soft essence such as fir, spruce or poplar. The sawdust from wood cutting is either ground and introduced for processing in briquettes and pellets, or used as such, but after preliminary treatment, in the combustion processes in the boilers of the heating plant and the dryer.
In Figure 9. The connection diagram of the component installations of the biomass thermal power plant within the factory is presented
The installed hot water and steam boiler has a high power of 1 GCal, which operates in automatic mode with mixed supply (sawdust, shredding, solid timber waste). The heating agent supplied is hot water at 100 degrees Celsius or superheated water at 120 degrees Celsius to power timber dryers and steam dryers with indirect release. For the thermal power plant consisting of the combustion boiler, boiler and steam generator, the thermal energy balance will be drawn up. The balance sheet will be drawn up for one day, for an average load of the installations, for a representative work shift. It will be taken into account four categories of biomass, coming from the factory itself. The heat balance diagrams drawn up according to the methodology in the specialized literature [2], for winter and summer days, are presented in the following figure:
The situation of the average hourly biomass consumption by categories 1s as follows: wood pellet consumption 13 kg/h, straw pellets 7 kg/h, briquette consumption 8 kg/h, sawdust consumption 14 kg/h, The consumption curves for combustion biomass are presented according to several criteria and time intervals, in the following graphs:
CONCLUSIONS
At the level of the analyzed region, the high potential of biomass of different types (starting from the woody biomass resulting from the exploitation of forests, the biomass resulting from classic agricultural crops but also the biomass that can be obtained through energy crops that can be established on the available land) must be used on a large scale for the purpose of energy production. For this, combined actions are needed to limit the use of wood biomass for industrial purposes other than energy (areas with negative impact on the environment and even energy intensive), actions to create systems for the collection of agricultural crop waste or biomass resulting from the sustainable exploitation of forests, but also to stimulate the establishment of energy crops on degraded agricultural land or not used for classic agricultural crops. On the other hand, the demand for biomass for energy applications needs to be supported by supporting categories of users who do not currently use biomass or use it in very low energy efficiency installations. The forecast price, which will increase sharply in the coming years, of natural gas, as the main current solution for heating buildings, will orient a large category of consumers towards the use of biomass.
Sustainable biomass energy recovery must comply with a number of principles/ desires such as:
* Increasing the energy efficiency of biomass energy production and use facilities;
* Sustainable management of biomass resources and the use of biomass energy;
* Use of local biomass resources through projects that ensure economic profitability and lead to local social benefits (job creation);
* Increased innovative level of biomass applications;
Analyzing the data on selective collection, it is estimated that the largest share of household waste is the plastic fraction, followed by glass and paper. This succession is especially valid in the administrative center of the area - the city of Beius. It is easy to guess that in the localities of Rurare, paper and cardboard are used in the fire and the metal is recovered separately. Wet products from food residues are used for animal husbandry and are not handed over to the collection company. In schim, where there are numerous public institutions, especially the educational ones, cellulose residues predominate, which are handed over in an organized way to the collector company, and the money obtained is used for the purchase of new teaching materials at school level.
REFERENCES
[1] Arion V., Bordianu С. $. a, Biomass and its use for energy purposes, Technical University of Chisinau Publishing House, Republic of Moldova, 2008.
[2] Badea A, Athanasovici У, Valorificarea resurse energetice secondarie, Editura Tehnicá, Bucharest, 1985. Balan M, Renewable Energies, U.T PRESS Publishing House, Cluj-Napoca, 2007.
[3] Hábásescu I., Cerempei V., Deleu V., Biomass Energy: Technologies and Technical Means, Publishing House of the Technical University of Moldova, Chisinau, 2009.
[4] Maican E, Renewable Energy Systems, Printech Publishing House, Bucharest, 2015.
[5] Rusu, T., Bejan, M., Waste - source of income, Mediamira Publishing House, Cluj Napoca, 2016.
[6] Salaru С, Bahnaru A, s.a. , Biodegradable waste management. Material and energy recovery.
[7] Study for the Association for Waste Recovery, UTM Publishing House, Chisinau, 2013.
[8] Braga 1., Frosin D., Ghincioiu N., Technologies for the energy use of wood biomass. National Conference on Wood Science and Engineering in the Third Millennium, Brasov, 20-21 November, p. 386, 2013.
[9] Berkesy C., Begea M., Berkesy L., Craciun M., Andreica M., Somesan M., Aspects of biomass production from forests. Ecoterra Magazine, Nr. 28, pp.23-30, 2011.
[10] www.ave-bihor.ro
[11] Study on the evaluation of the current energy potential of renewable energy sources in Romania, elaborated by the ICEMENERG Institute for the Ministry of Industries and Trade, Bucharest, 2006.
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