Ecological Engineering and Environment Protection

Abstract: Lactic acid wort-based beverages are functional, non-alcoholic, with low pH value and produced by the fermentation of wort by lactic acid bacteria. They are not well accepted by consumers because of their poor sensory characteristics. Therefore, 0.025 and 0.05 % (v/v) mint (Mentha piperita) essential oil was used as a tool for improvement of lactic acid wort-based beverages organoleptic profile. Wort was produced by 60% Pilsen malt, 20% Vienna malt, and 20% Caramel Munich ІІ malt. It was inoculated with probiotic lactic acid bacteria Lactobacillus casei ssp. rhamnosus LBRC11 at a concentration of 10⁷ cells/ml and fermentation was carried out at constant temperature of 25°C. The dynamics of pH, concentration of viable cells, phenolic compounds and antioxidant activity were monitored and the beverages obtained were evaluated by a tasting panel. The results showed that addition of mint essential oil in concentration of 0.025 and 0.05 % (v/v) inhibited lactic acid fermentation but improved the sensory profile of the beverage obtained only when 0.025% mint essential oil was added. Mint essential oil addition led to an increase in the total phenolic compounds concentration, phenolic acids and flavonoid phenolic compounds, measured by Folin–Ciocalteu and modified Glories method but resulted in a decrease in the antioxidant activity, measured by the DPPH radical scavenging assay, cupric reducing antioxidant power (CUPRAC) and ferric reducing antioxidant power (FRAP). The antioxidant activity measured by the ABTS radical scavenging assay was almost equal for the beverages with and without mint essential oil addition. The results obtained will be used for modelling of lactic acids fermentation with addition of mint essential oil for the production of functional wort-based beverages.
Keywords: lactic acid fermentation, wort, mint essential oil, phenolic compounds, antioxidant activity

EXTREMUM SEEKING CONTROL OF TWO-STAGE ANAEROBIC DIGESTION SYSTEM: A MINI REVIEW

Nicolai Christov, Haoping Wang and Ivan Simeonov

Abstract. Anaerobic digestion (AD) is a biotechnological process, in which the microorganisms degrade the complex organic matter to simpler components under anaerobic conditions to produce biogas and fertilizer. It has long been known that the two main species (acidogenic and methanogenic) in the community of microorganisms in AD differ in many aspects and the optimal conditions for their growth and development are different. Therefore, in AD in a single bioreactor (BR) (single-phase process), the optimal conditions are selected taking into account the slow-growing methanogens at the expense of fast-growing acidogens, which affects the efficiency of the whole process. This has led in recent years to the development of two-stage AD (TSAD), in which processes are divided into a cascade of two separate BRs. It is known that this division of the processes into two consecutive BRs leads to significantly higher energy yields for the two-phase system (H₂ + CH₄), compared to the traditional single-stage CH₄ production process.
In our previous studies different mathematical models of the TSAD have been developed. It was shown that in both BRs the input-output characteristics have a clear maximum, which allows the yields to increase significantly if operations are provided around the maximum points. However, in order to maintain the sustainability of the biogas plants work, it is necessary to introduce automatic control with sophisticated extremum seeking control (ESC) algorithms.
This paper presents the pioneering research on ESC of AD process with production of hydrogen and methane. This research has been jointly realized by the Department of Biotechnology at The Stephan Angeloff Institute of Microbiology (SAIM), Bulgarian Academy of Sciences, and the French-Chinese Laboratory on Automatic Control and Signal Processing (LaFCAS), Nanjing University of Science and Technology, in collaboration with the Laboratory of Signals and Systems (L2S) at the French National Center of Scientific Research (CNRS).
Keywords: two-stage anaerobic digestion, organic waste, hydrogen, methane, mathematical models, extremum seeking control, maximal energy production

IMPROVEMENT OF BIOGAS PRODUCTION IN ANAEROBIC DIGESTION PROCESS

Abdelhani Chaabna, Samia Semcheddine

Abstract: The production of biogas enables environmental preservation and sustainable development of rural areas and landlocked regions, as well as diversification of renewable energy resources. This paper is a contribution to improving the production of biogas by Sliding Mode Control (SMC).

In the literature there are many models describing the behaviour of reactions during anaerobic digestion and used for control design. The AM2 model is one of the simplest models and can be exploited easily for the control design purposes. In this paper, the reduced model AM2 was exploited to develop and testing by simulations the robust control law SMC.
The results obtained have proved the effectiveness of the control method proposed in this paper. A study of the robustness for monitoring and disturbances rejection demonstrated the great interest of this method, which is a non-linear technique and gives very good results in terms of robustness but it presents the problem of chattering. In practice, the chattering of the control action can cause premature wear of the actuators or parts of the system due to heavy oscillations. The chattering phenomenon is caused by the discontinuous term which appears in the control signal. This paper presents a solution to the chattering problem by replacing the discontinuous term with a continuous one. Different Simulations and comparisons are presented and interpreted with satisfactory results.
Keywords: Anaerobic digestion, SMC, chattering, robustness, nonlinear control

FOREST FIRES IN 2020 - ECONOMIC AND SOCIAL CONSEQUENCES

Hristo Tsakov, Alexandar Alexandrov, Dafina Zoteva, Olympia Roeva

Abstract: The continuing climatic anomalies and the changed social realities caused by the global COVID-19 pandemic impose new responsibilities and new solutions for the management and use of forests.

Experts have proved that overexploitation of the forests and the annual burning of huge forest areas seriously jeopardize food security on a regional and global scale, the economic stability of communities reduces, and the environmental degradation increases.

The fiery hell in Australia in 2020 is one of the worst wildlife disasters in modern history. There are more than 115,000 square kilometers of bushes and forests devastated, thousands of homes destroyed, people and over three million wild animals killed.

In 2020, 499 fires were registered in the forest territories of Bulgaria with total area of 52455 dka. Deciduous and coniferous vegetation, grasses, border farmland and infrastructure are affected.

The paper summarizes the financial damage and resources used to extinguish the fires in the forests of Bulgaria in 2020, regardless of their ownership.

Keywords: forest fires, economic consequences, social consequences.

ESTIMATION OF INDUSTRIAL MATERIAL FLOW PRODUCED BY „DEVNYA CEMENT“AD FOR REMEDIATION OF ACID SPILS

Svetla Marinova, Elena Zlatareva

Abstract. The issues of acidity and liming of soils were raised in Bulgaria more than 60-70 years ago. „Devnya Cement“ produces the Restart product, as an integral part of the process in the installation of cement clinker in a dry way and contains a high amount of calcium oxide (lime material). The aim of the study is to establish the effect of the studied product RESTART and possibilities for its use as an ameliorant on acid soils. A vegetation experiment was performed with a test crops of corn with different percentages of ameliorant. The chemical and physico-mechanical parameters of the treated soil were studied and the changes in the degree of soil acidity were established. Preliminary consumption rates of the ameliorant have been determined, when it is used for amelioration of acid soils. The chemical characteristics of the plant samples show, that the values of the chemical elements are in optimal concentrations and cannot have a harmful effect, when used as animal feed. To correct the acidity of soils with similar acidic properties as in the Devnya region, it may be recommended to apply about 1-2t/daa of the studied ameliorant.
Keywords: ameliorant, characteristics, neutralizing ability

ACHIEVEMENTS IN SPACE EXPLORATIONS OF SPACE RESEARCH AND TECHNOLOGY INSTITUTE AT THE BULGARIAN ACADEMY OF SCIENCES

Denitsa Borisova, Georgi Jelev, Georgi Sotirov

Abstract: The paper is devoted to the achievements in space explorations of the Space Research and Technology Institute at the Bulgarian Academy of Sciences. There are considered the research activities and shown the projects and perspective directions for work and their applications.
Keywords: space exploration, environmental monitoring, technology transfer

METHODS FOR IDENTIFICATION AND VISUALIZATION OF MUNICIPAL WASTE DISPOSAL SITES USING AEROSPACE DATA
Adlin Dancheva
Abstract: With the increase of temperatures in the summer, the danger of self-ignition of landfills for household waste increases, because of the biochemical processes that take place inside them. The most recent example is the municipal landfill for non-hazardous waste near the town of Dupnitsa. The self-ignition started on July 23, 2021 and continued to smolder for almost a week, which led to a great danger of burning the area around it or poisoning the population. It is believed that one of the main reasons is the great depth of the accumulated waste. There is an urgent need to do quality control of most of the landfills for municipal waste in our country. Some of them are located next to major river arteries or international roads. Non-compliance with the requirements for maintenance, management and operation hides a serious potential for an ecological catastrophe. It is essential that stricter measures are taken and that these landfills are monitored. The aim of the present work is to reveal the possibilities and potential of aerospace data and to show different methods for processing, interpretation, and visualization. They can easily identify, map, and survey a waste disposal site. Optical images of the multispectral instrument (MSI) of the Sentinel 2 platform and radar (SAR) data from the Sentinel 1 platform of the Copernicus program of the European Space Agency were used. Thermal bands from the Landsat 5 - 7 (ETM) and Landsat 8 (OLI / TIRS) sensors of the Landsat program were used to calculate the land surface temperature. Satellite images have been orthogonized, and composite images between optical and radar data have been created for better visualization.
Keywords: Land surface temperature, landfills, monitoring, aerospace data

RADIATION SHIELDING AND DOSE ASSESSMENT OF THE CYCLOTRON FACILITY AT INRNE-BAS
A. Demerdjiev, D. Tonev, N. Goutev
Abstract. The Institute for Nuclear Research and Nuclear Energy at the Bulgarian Academy of Sciences is working on the construction of a cyclotron centre. The facility is on a design level. At this stage of the project, an important task is the radiation shielding assessment of the facility. Nowadays, the Monte Carlo transport codes have become the tool of choice for solving this type of problems. In the current paper, the transport code FLUKA is used for the calculations. It is widely applied for shielding design and analysis of accelerators and their components. The distributions of the radiation fields inside and outside the cyclotron bunker are presented in this paper. Two different irradiation scenarios and bunker configurations are considered in the conducted Monte Carlo simulations. These results will be used as a guidance in site planning.
Keywords: TR-24 cyclotron, Radiation protection, Monte Carlo simulations, FLUKA

PROBLEMS AND PERSPECTIVES IN ORGANIC CULTIVATION OF CEREALS - OVERVIEW
Milen Chanev

Abstract: In this study, an overview is made and a comparative analysis of articles, reports and materials dealing with organic farming of LWC, in the period 1970 to 2021 is performed. After analysing the literature, the following conclusions are made:

Cereals occupy a particularly important place in organic farming, the main advantages of their cultivation are easy farming techniques, relatively easy mechanical weed control, disease control through rational crop rotation, opportunities for biological control of major pests

The soils in organic farming are better structured than those in conventional agriculture. Organic farming practices are related to improving soil properties, including the addition of organic matter to the soil, increasing the population of earthworms, biodiversity, soil fertility and more. Biological management provides a more stable soil structure. The larger pores observed in biological management have a beneficial effect on the physical properties of the soil, such as water flow and water capacity. The greater porosity of the soil provides a good habitat for soil microorganisms. Organic farming contributes to creating a better soil structure.

Organic farming systems have traditionally been based on crop rotation. The aim of organic farming is to achieve a balance between crops that reduce soil fertility and crops that restore fertility. Crop rotation is the main tool that integrates the maintenance and development of soil fertility with various aspects of plant production in biological systems.

Specialised selection programmes for creating varieties suitable for organic farming are too few due to the small number of users and high costs. The most common practise includes testing the suitability of conventional varieties in biological conditions, propagation and distribution of the best in the biological sector.

Sowing norms directly control the sowing density, as well as the nutrient area of each plant. Changing sowing rates is also an excellent method for controlling weeding in biological fields.

Concerning yields from organic and conventional agriculture, organic farms are less productive than conventional ones and their productivity is lower. But if environmental variables are taken into account, organic farms show the same or higher efficiency.

A major problem facing organic farming in the future is the protection of fields from pollution by genetically modified organisms. An option for protecting biological fields is to maintain a buffer zone between the farm and the neighbouring conventional fields to prevent accidental contamination with GMOs.

Keywords: organic farming; cereals, sustainable agriculture.

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