Market Research on Waste Biomass Material for Combined Energy Production in Bulgaria: A Path Toward Enhanced Energy Efficiency ^†

Abstract

Using waste biomass as a raw material for the combined production of electricity and heat offers corresponding energy, economic, environmental and resource efficiency benefits. The study examines both the performance of a system for combined energy production based on the Organic Rankine Cycle (ORC) utilizing wood biomass and the market interest in its deployment within Bulgaria. Its objective is to propose a technically and economically viable solution for the recovery of waste biomass through the combined production of electricity and heat while simultaneously assessing the readiness of industrial and municipal sectors to adopt such systems. The cogeneration plant incorporates an ORC module enhanced with three additional economizers that capture residual heat from flue gases. Operating on 2 t/h of biomass, the system delivers 1156 kW of electric power and 3660 kW of thermal energy, recovering an additional 2664 kW of heat. The overall energy efficiency reaches 85%, with projected annual revenues exceeding EUR 600,000 and a reduction in carbon dioxide emissions of over 5800 t/yr. These indicators can be achieved through optimal installation and operation. When operating at a reduced load, however, the specific fuel consumption increases and the overall efficiency of the installation decreases. The marketing survey results indicate that 75% of respondents express interest in adopting such technologies, contingent upon the availability of financial incentives. The strongest demand is observed for systems with capacities up to 1000 kW. However, significant barriers remain, including high initial investment costs and uneven access to raw materials. The findings confirm that the developed system offers a technologically robust, environmentally efficient and market-relevant solution, aligned with the goals of energy independence, sustainability and the transition to a low-carbon economy.

1. Introduction

With the increasing demand for sustainable development and the optimal use of energy resources, cogeneration systems based on waste biomass are establishing themselves as an effective and sustainable solution both in the scientific community and in industrial practice [1]. The analyses of the studies in [2] show how biotechnology can support the transformation of developing countries through the development of bio-based industries, sustainable agribusiness and the reduction of environmental impacts. The authors in [3] trace the development of the European Union Bioeconomy Strategy, based on key research and biotechnology programs, highlighting the impact of public–private partnerships for bio-based industries. Additional insights in [4] and [5] further emphasize the role of collaborative frameworks and innovation platforms in implementing the strategy. A broader policy perspective is also presented in [6], which discusses institutional and regulatory aspects. Biomass, which is waste raw materials from agricultural and industrial processes, reveals untapped energy potential that can be transformed into valuable energy products. Research by the authors in [7] underscores the importance of converting waste biomass into resources for achieving a circular bioeconomy. It summarizes scientific advancements from the 1970s to the present, addressing technological challenges and their analysis. This is a key element of the circular economy, where waste is transformed into a resource, contributing to the reduction in environmental problems associated with its accumulation or uncontrolled burning. Studies in [8] examine the impact of the Kyoto Protocol on the agricultural and forestry sectors, emphasizing the importance of technological innovation. Further discussions in [9] highlight the optimal use of databases to reduce emissions, while [10] explores how these strategies contribute to effectively combatting global warming.

According to the authors in [11], the implementation of cogeneration systems is based on their capability to simultaneously produce thermal and electrical energy, which significantly improves energy efficiency. The study [12] reveals that CHP could be financially feasible for household heating and cooling when the processed area exceeds 500–600 m². The application of micro cogeneration installations (ranging from 4 kW to 10 MW) is discussed in [13,14], where the heat-to-power ratio appears to be a critical factor for these facilities. When the electrical energy requirement exceeds the heat energy requirement, motors are favored. Unlike gas turbines and internal combustion engines, which produce electricity as a by-product of heat (steam), steam turbines produce heat (steam) as a by-product of electricity production. Another notable feature of steam turbines is that fuel is not converted into energy directly within the turbine itself. Instead, a boiler is typically employed to generate high-pressure steam, which subsequently drives the turbine and generator. This separation of functions enables steam turbine cogeneration plants to utilize a variety of fuels, including pure liquefied gas, solid fuels and waste biomass [15]. Traditional energy systems typically achieve an efficiency of around 30%, as discussed in [16]. In some cases, this can improve to approximately 35% [17], and in optimized conditions, this can improve up to 40% [18]. In contrast, co-generation technologies have demonstrated the ability to reach efficiencies as high as 85%, according to the findings in [19]. One of the key features of these technologies is their use of waste biomass generated during forest clearing, as outlined in [20]. Additional studies in [21] and [22] confirm the sustainability of this biomass sourcing method. This approach contributes to a reduction in the consumption of conventional fuels. For example, ref. [23] highlights the decreased reliance on coal, ref. [24] addresses the lower usage of natural gas and [25] focuses on minimizing oil consumption. The process also enables the possibility of carbon-neutral combustion. According to [26], this is achieved when the carbon released during biomass combustion is balanced by the carbon absorbed during plant growth. The study [27] supports this by emphasizing the role of closed carbon cycles in biomass systems. In addition, ref. [28] presents data on net-zero emissions in well-managed biomass supply chains. The findings in [29] highlight the importance of sustainable land use in maintaining this balance. Finally, ref. [30] discusses the long-term climate benefits of carbon-neutral biomass applications.

The study in [31] highlights that waste biomass cogeneration can increase energy efficiency by up to 80%, making it a crucial element in achieving sustainable energy production. Similarly, ref. [32] confirms this finding and emphasizes the growing relevance of such systems in modern energy strategies. In addition, ref. [31] points out the significant role of these technologies in reducing greenhouse gas emissions. The study [32] further notes that this impact is especially pronounced in regions where waste raw materials are readily available. The author in [33] confirms the importance of cogeneration technologies in the decarbonization process. Likewise, ref. [34] emphasizes their key role in regions with a high concentration of forest resources, where biomass availability is high. Bulgaria, with its well-developed forestry and wood-processing sectors, has significant potential for utilizing waste biomass. Residual materials such as branches, bark, sawdust and agricultural plant residues often remain unused, despite being a valuable resource for efficient energy production through cogeneration. The research in [35] highlights that wood residues constitute approximately 45% of the available raw materials for energy production in the country, demonstrating strong potential for the adoption of cogeneration technologies. Furthermore, the authors in [36] note that the return on investment for cogeneration systems ranges between 5 and 7 years, making them an economically viable choice for long-term operation.

The design of waste biomass cogeneration systems requires a holistic approach, including raw material analysis, an assessment of technological requirements and the selection of optimal combustion and energy conversion solutions [37]. The research by [38] shows that such systems can create new jobs in rural areas while supporting the local economy and reducing dependence on imported fuels.

The financial analysis of the implementation of a combined energy production system usually only considers revenues from sold electricity and thermal energy. Good practices in the implementation of ORC power plants in Europe are discussed in detail in [39]. The methodology of environmental pricing in terms of emissions, concentrations and endpoints is well analyzed and discussed.

The financial profitability of ORC power plant projects would be significantly improved by the use of appropriate financial mechanisms (grant schemes). These mechanisms were developed based on a preliminary study of the potential of waste biomass in Europe. The European Council and the European Commission have developed various guidelines and energy certification schemes to support the development of smart, eco-friendly technologies for processing waste biomass. Direct subsidies covering part of the initial investment, green certificate schemes and tax incentives for enterprises investing in high-efficiency cogeneration installations are particularly suitable. These approaches have been successfully implemented in several European countries, demonstrating their effectiveness in overcoming financial barriers and stimulating investment in renewable energy and cogeneration technologies [40,41,42]. The incentive grant mechanism is currently applied to biomass systems in Bulgaria for combined energy production, where it is stated that the produced electricity is purchased at a preferential feed-in tariff of EUR 146.9/MWh.

It should be mentioned that facilities of this type, which produce electricity and thermal energy from waste biomass, have a 20-year contract for the purchase of electricity at a preferential feed-in tariff, which is currently quite high and attractive (applicable to the territory of Bulgaria) [43]. The project only became financially feasible through the sale of the facility’s thermal needs, which are covered by thermal energy, with the remainder being used to supply greenhouses. With current technology, some of the thermal energy can be converted into electricity, which is sold at the preferential price, making the project even more attractive.

Marketing research also plays an essential role in the process of implementing cogeneration systems. It allows for the identification of target groups, understanding the barriers to the adoption of the technology and the development of financial mechanisms that promote the sustainable use of these innovations [44,45]. The authors in [46,47] note that the market interest in cogeneration technologies is significantly increasing in regions with available waste biomass resources, which highlights their economic and environmental sustainability.

This study presents an integrated approach to the design and construction of waste biomass cogeneration systems, combining technical analysis and market research (

Table 1. Reasons for conducting the study.

Reason	Justification
High potential of waste raw materials in Bulgaria	Wood and agricultural waste provide a significant base for energy production in Bulgaria.
Need to increase energy efficiency	Cogeneration systems reduce energy losses by over 30% compared to conventional technologies.
Achieving environmental goals	Reducing the carbon footprint and utilizing waste raw materials.
Lack of sufficient awareness and market implementation.	The goal is to overcome acceptance barriers through market analysis and demonstration projects.
Opportunities for economic return	Green certificates and subsidies significantly reduce the financial risk for investors.

). It aims to assess the deployment potential, technological capabilities and market interest, providing a comprehensive solution for sustainable and efficient energy production.

The aim of the study is to provide precise data to support the analysis and comparison of cogeneration technologies. Through statistical analysis of the information collected from 143 surveyed participants, including representatives of industry, municipalities and small businesses, the main trends, preferences and motivations of organizations for implementing these technologies are investigated. The participant’s distribution is as follows:

• 39% representatives of municipal authorities;
• 34% from small and medium enterprises;
• 27% from industrial sectors.

The participants were selected based on their energy consumption profiles and prior participation in national sustainability programs.

The obtained results will provide valuable information on the factors that influence decisions to use cogeneration and will support the development of effective strategies for promoting its application.

The present study is a result of the joint effort of university professors and a consulting company, who combined their academic experience and practical knowledge to explore both the potential opportunities and challenges associated with the implementation of biomass cogeneration systems. The main instrument for collecting information is a marketing survey, which aims to provide a detailed and clear analysis of the following aspects:

• the availability of resources and the possibilities for their use for cogeneration;
• the attitudes of organizations and their readiness to invest in such technologies;
• the financial mechanisms for facilitating implementation, as well as the barriers that organizations face;
• the environmental and economic benefits that participants expect from the implementation of cogeneration systems;
• the level of awareness and the attitude of stakeholders towards cogeneration technologies.

The developed methodology provides comprehensive information necessary for an in-depth study of the market, the identification of KPIs (key performance indicators) and revealing the main obstacles hindering the implementation of cogeneration technologies. The survey questions are formulated and structured in accordance with the methodology, arranged in pairs to achieve a detailed comparative analysis, as follows:

• What raw materials could you use for cogeneration?
• How easy is it for you to find the necessary raw materials?

The combination of these questions provides a comprehensive picture of the availability and accessibility of raw materials, which is a key factor for the economic and technical feasibility of cogeneration.

3.

How likely is your organization to invest in a cogeneration system?

4.

What size of cogeneration system would meet your needs?

The combination of these questions allows for a more in-depth analysis of the investment attitudes and needs of organizations, which supports the development of strategies for the promotion and implementation of cogeneration technologies.

5.

What financial mechanisms would facilitate your investment in cogeneration?

6.

What are the main obstacles to the implementation of a cogeneration system?

The combination of these questions provides complete information on the financial incentives and challenges, which is crucial for the development of effective policies and strategies for the promotion of cogeneration technologies.

7.

What environmental benefits do you think cogeneration can provide?

8.

What economic benefits do you expect from a cogeneration system?

The combination of these questions provides a complete picture of the perceived benefits of cogeneration, which is crucial for developing strategies that highlight both the environmental and economic advantages to encourage the wider adoption of these technologies.

9.

How familiar are you with cogeneration systems and their applications?

10.

How important is the environmental aspect when selecting energy technologies for your organization?

The combination of these questions offers a comprehensive view of organizational awareness and environmental priorities, which is essential for designing effective strategies to promote cogeneration systems.

The number and type of questions were determined by a prior marketing campaign directed to all respondents, with a selection of medium and large companies that are significant consumers of electricity and thermal energy. The questions focused on the price of electricity, the price of raw materials and the cost of transportation (if applicable to the site in question). The environmental impact of the production line was also discussed. The use of electrical and thermal energy produced by renewable energy sources allows the company to use a green logo for production.

2. Results

The project’s goal is to build a cogeneration plant based on investment plans that focus on developing an extremely efficient system for producing energy from waste biomass.

The facility is located in a high mountain area with predominantly coniferous tree species—Scots pine, spruce, white fir, etc. The forest clears annually to ensure normal tree growth in accordance with legal requirements. The amount of material is sufficient to meet the needs of the power plant. The facility was set into operation in 2024 as the facility is supplied with forestry residues—primarily Scots pine, spruce and fir—resulting from routine forest maintenance and sanitary harvesting in mountainous regions hereinafter referred to as waste biomass. This mix of products in the mountainous regions is characterized by its low calorific value, which makes it unprofitable to use various methods for the production of combustible gas (gasification, pyrolysis, etc.) and its subsequent combustion in cogeneration installations. The average calorific value of the studied wood waste in the region is estimated from the analysis at 4400 kWh/t (lower heating value). The required humidity of the wood material before the boiler (pre-drying at high input humidity) is achieved by a certain amount of thermal energy during the operation of the installation.

The available deforested wood for remediation purposes in Bulgaria is significant. A previous study by the team found that about 25% of the currently available amount of waste biomass in Bulgaria is being utilized. This indicates a significant resource for future use and possibilities of the implementation of biomass installations.

The main fuel resource is waste wood, which fires a boiler. The raw material is dried and chopped before reaching the boiler. Some of the thermal energy is used to dry waste biomass. The remaining thermal energy is used to supply greenhouses and can also be converted into electricity as required. The generated thermal energy heats thermal oil, which transfers the energy to a module based on Organic Rankine Cycle (ORC) technology. The technology enables the simultaneous production of electricity and thermal energy from renewable sources, ensuring improved energy efficiency and environmental sustainability. Ash is extracted from multiple locations within the boiler and economizers. It is then transported via sealed conveyors and stored in an external tank, all in compliance with environmental standards. The products of the combustion process are stored on site in accordance with local regulations and disposed of accordingly.

The plant is located on private land, specifically prepared for this purpose. The location is strategically chosen to facilitate access to raw materials and minimize logistics and maintenance costs.

Main Stages of Project Implementation

Preparatory activities: The first stage includes the excavation and leveling of the terrain to provide a stable foundation for the installation of the facilities. In addition, access roads and service areas for loading and unloading activities are performed.

Delivery and installation of the biomass boiler: The boiler, designed to work with waste wood, is delivered and installed on-site. The system is equipped with automated fuel supply mechanisms that ensure uninterrupted operation and high efficiency.

Installation of the ORC module and additional equipment: The module converts the thermal energy transferred by the thermal oil into electrical energy while also delivering additional thermal energy for local heating needs. This technology allows for the effective utilization of low-temperature heat sources, making it a valuable asset in various applications.

Construction of a production hall and auxiliary facilities: The production hall provides protection for the main equipment and includes fuel storage areas. In addition, a water tank required for cooling is constructed, as well as infrastructure for waste management.

Construction of a transformer station and electrical connection: In order to ensure a stable supply of electrical energy to the national grid, a transformer station is constructed. The connection infrastructure is designed with high reliability to minimize energy losses.

The results of the technical and marketing analysis related to the design and construction of the cogeneration system are reviewed. The emphasis is on the energy efficiency, the impact on carbon emissions and the socio-economic feasibility of the project.

2.1. Cogeneration System Overview

2.1.1. Location of the Cogeneration System

The system for the simultaneous production of thermal and electric energy is built in a region characterized by the availability of significant quantities of wood waste in the South-Western part of Bulgaria. It is the largest of a few installations incorporating an ORC module. Due to the well-developed logging and woodworking industries, significant volumes of wood waste materials accumulate in the area, which can be effectively used as raw material for the cogeneration plant. This makes the system environmentally sustainable while simultaneously stimulating the local economy by efficiently utilizing a resource that would otherwise remain unused. For the construction of the biomass cogeneration plant, two plots of land were purchased, both located in close proximity to a main asphalt road. The first plot is designated for the installation itself, while the second is for building a storage facility for biomass waste. To prepare the sites for construction, excavation work is required to level the ground and provide a stable foundation. Once the excavation is completed, the construction of the foundation begins to ensure the stability and durability of the structure. Figure 1 shows the general view of the completed plant after the construction has been finalized.

2.1.2. Description of the Cogeneration Plant with a Thermal Oil Boiler and ORC Module

An overview of the entire installation can be found in [48]. The main elements of the installation include the following important components, each of which contributes to the efficiency and sustainability of the system:

A. 

Fuel flow

Information about the fuel flow path is provided below. The system includes the following main facilities:

A moving plate silo, with the rated capacity of the extractor being 210 m³ per 24 h;

A Fuel Redler conveyor doses the fuel from the silo to the boiler;

Duplo system: The main purpose of Duplo is to move from the outside to the inside of the boiler the solid fuel which is inconsistent and not aggregate by nature. The screws are operated by two speed controllers of wood chips flow, with opposite functioning, complete with manual adjustment control. In the upper part, there is a sash-cutting section in which a piston slides to move a security fire stop shutter. If a wood piece is bigger than the sliding channel dimensions, the piece will be sliced;

Combustion chamber: The combustion is performed on a moving grate through the forced inflow of combustion air, which is mixed with the gases in three different phases: primary air (under-grate), secondary air (over-grate) and tertiary air (post-combustion chamber);

Heat exchanger: The flue gases generated in the combustion chamber are passed through a coil heat exchanger where they heat thermal oil. The nominal final temperature of the oil is 320 °C. The efficiency of the heat exchanger is maintained by a special automatic cleaning system that prevents the increase in thermal resistance due to fouling on the heat exchange surface;

Economizer 1: In order to improve the overall efficiency of the plant and recover the maximum thermal energy from the flue gases, they are passed through a gas/oil economizer to preheat the incoming oil in the main exchanger (Figure 2);

Economizer 2: It is also a gas/oil type and is used for the additional heat utilization of the fumes. This unit preheats the oil in the low-temperature circuit. Each economizer has an automatic cleaning system for its heat exchange surface.

Economizer 3—combustion air preheater: Once the maximum thermal recovery on the oil side is completed, a further recovery is realized by means of a fumes/air recuperative heat exchanger that allows for the pre-heating of the air before bringing it to the boiler as combustion air. This has an important advantage as far as the efficiency of the system is concerned as it enables it to either dry the humid waste biomass in the combustion chamber or raise the temperature of the air in the boiler.

Ash removal: The combustion ashes are collected in different points of the plant: Inside the combustion chamber by a special system in order to prevent the crystallization of the ashes; Under the moving grate; Under the separating chamber in post-combustion sector; Under the entry in the main heat exchanger; Under the Economizer 1; Under the Economizer 2; Under the Economizer—preheater; Under the multi-cyclone; and Under the bag filter.

The ashes collected at these points are unloaded by airtight valves on a special double-chain conveyor that, in its turn, conveys them to a tank placed outside the thermal-electric power station for the ashes’ collection.

B. 

Fume gases flow

In order to meet the current regulatory requirements, the exhaust gases are cleaned before being released into the atmosphere. The pathflow of the fume gases is presented below:

Fume gases purifier—multi-cyclone: The first dust precipitation takes place in the multi-cyclone. It is a filter consisting of different cyclones. An inversion of the inertial velocity occurs in each of these cyclones, and this allows for the low-speed collection of the combustion residual gaseous bodies. The collected particulates fall into a “V”-shaped hopper for the deposit and will be subsequently managed by the “Ashes flow” line.

Smoke connections: The exchangers’ outlet smoke is transported through flues made of stainless steel with high-level insulation. The flues are fully inspectable.

Induced draft fan: The smoke line operates under depression owing to the forced draught caused by the induced draft fan, which is installed at the end of the smokes line before the chimney. The fan also provides the smokes ejection through the chimney. The chimney is used to transport the completely cleaned flue gases to the atmosphere (see Figure 3).

C. 

Heat transmission and electrical power production

To ensure the system operates safely and optimally, cooling systems are used, which utilize waste heat, thereby increasing the installation’s overall efficiency. The summarized information on the relevant systems is provided below:

Thermal oil circuits: The thermal oil, heated up to the two requested temperatures (high temperature and low temperature), is conveyed by two separate lines to the flanges of the ORG generator. The transmission lines are carried out by circulation pumps, emergency motor pumps, safety exchangers, etc.

ORC module: The functioning of the Turboden generator is based on the ORC, a cycle that is similar to the one used by a traditional steam turbine, except for the operating fluid that, in this case, is an organic fluid with a high molecular mass. This plant is based on a Rankine closed cycle, realized by using an appropriate organic fluid as an operating fluid.

2.1.3. Technical Data About the System’s Components. Principle of Operation

The system includes a new biomass boiler of the Global/G 500 OD type, which is connected to an ORC module Turboden 12-HRS Split W.A. for the combined production of electrical and thermal energy (Figure 4).

The main equipment is shown in Figure 5 and Figure 6, which illustrate the overall architecture of the installation and the connections between the primary components.

The boiler and the ORC module are optimized for biomass operation, ensuring maximum fuel utilization and high energy efficiency.

The principle of operation of the biomass boiler is as follows (Figure 2). All thermal calculations are based on the parameters specified on Figure 2 and commented on in [48].

A screenshot from the power plant SCADA system is provided in Figure 7.

Some of the main technical advantages of the entire system are as follows: the high efficiency of the cycle; the high efficiency of the ORC electric generator—between 95.5 and 96.5% based on the generator load (manufacturer technical data sheet); the efficiency of the ORC module, of more than 25% (thermal oil input power at a nominal load—4425 kW and gross electricity power output at q nominal load—1156 kW); the low mechanical stress of the turbine, due to the low peripheral speed; the low rotation speed of the turbine that allows for the direct drive of the electric generator without a reduction in revolutions; the absence of erosion on the blades due to the absence of droplets in the steam; the long life of the operation; and the functioning not being guarded by an operator.

The proposed system allows for the use of heated oil from a biomass boiler in an ORC module to produce electricity and heat in a combined manner. The high efficiency of the system is achieved by the use of three additional economizers for heating the oil and by the high efficiency of the ORC module (25%). The boiler is fed with waste biomass at a rate of 2 t/h, and according to the estimated average calorific value of 4400 kWh/t, the input power of the system is 8800 kW. The electric power produced by the module is 1156 kW, and the thermal power amounts to 3660 kW. Additionally, three installed economizers recover the heat from flue gases to heat up the oil. The additional amount of captured power is 2664 kW. Based on the technical specification provided by the manufacturer, the total heat loss of the proposed system amounts to 8% (704 kW). The system’s total output is 7480 kW (including electric and thermal outputs, as well as three economiser heat recoveries). With an input power of 8800 kW the installation’s efficiency is estimated at 85%.

The system also presents practical advantages, such as simple procedures of start–stop, noiseless operation, minimum maintenance requirements and good performance at a partial load.

The biomass boiler and ORC module are the main components of the system, but for the effective operation of the installation, additional equipment and supporting machinery are required, as described below. A specialized building (industrial hall) has been constructed for fuel storage. Wood waste is loaded, unloaded and transported using a new front loader, and for this purpose, a trailer and a transport vehicle have also been purchased. Control over the amount of waste biomass delivered is carried out using a newly installed industrial scale, which measures the weight of the arriving trucks with trailers at the entrance to the site. A water reservoir for cooling water has been built to meet the system’s requirements. A backup power generator has also been installed to provide electricity in case of a failure or interruption in the power supply to the facility. In compliance with legal requirements, the physical equipment for mutual connection to the electrical grid must meet industrial standards. This equipment includes control distribution blocks, cables, three three-phase current transformer modules, three three-phase voltage transformer modules and four electricity meters. The system is connected to the electrical transmission grid through a new 20 kV power line and a 270 m long cable. The proximity of the connection point to the power plant reduces costs, and the losses over the 270 m line are minimal. The plant uses a step-up transformer with a power rating of 0.4/20 kV and a nominal capacity of 1600 kVA, designed with reduced losses. The nominal frequency of the supplied electricity is 50 Hz, and the power factor of the generators must be cos φ = 1. This ensures sufficient capacity for the transmission of all the electricity generated by the biomass power plant.

The expected benefits after the project completion are the following: The annual consumption of wood waste will be 15,000 t, at a cost of EUR 268,428. The sale of electricity to the power company will provide 6686 MWh annually, generating income of EUR 982,204. A transmission fee of EUR 9812 per year will be paid for the sold electricity. The annual operation and maintenance costs are expected to be EUR 53,000. The total annual income after project implementation is expected to be EUR 650,964, demonstrating significant financial sustainability and investment efficiency.

The cost of the boiler systems with an ORC module came to EUR 2,970,000, including the design of the facility. The total construction work is divided into two stages: stage 1 involves on-site preparation activities (EUR 63,000), while stage 2 involves the construction of the machinery room, offices and utility room (EUR 302,000). Salaries and taxes amounted to EUR 210,000. The total project costs are EUR 3,545,000. Based on the calculated annual income of EUR 650,964, the simple payback period is 5.45 years.

2.2. Greenhouse Emissions Reductions Against the Baseline

Emission reduction projects above a certain size (variable depending on the type of technology) can generate carbon credits that can be monetized.

The savings in primary energy resources resulting from the implementation of a single measure or a package of measures lead to a reduction in the generated carbon emissions (CO₂) [49].

The environmental equivalent of the caused carbon emissions is determined based on the required energy, according to Annex No. 1 of the “National Methodology for Calculating the Energy Characteristics of Buildings,” in [50] on the technical requirements for the energy characteristics of buildings.

The biomass power plant is intended to replace the current energy source used for producing electricity and thermal energy. Clearly, the plant operates for 5784 h per year, producing 6686 MWh of electricity and 21,168 MWh of thermal energy. The implementation of a biomass power plant will displace grid electricity consumption from the national distribution company amounting to 6686 MWh of electricity, as the emission factor for electricity consumption is 486 gCO₂/kWh according to the regulations. Replacing thermal energy from gaseous fossil fuels, which amounts to 21,168 MWh, leads to emission savings, whereas the emission factor for gaseous fossil fuels is 220 gCO₂/kWh. Based on these assumptions, the estimated emissions are 7906 tCO₂/year. With the implementation of the biomass power plant, about 11,567 t/year (equivalent to 50,897 MWh/year) of waste biomass is consumed. Using a value of 40 gCO₂/kWh for solid fuel (to operational emissions (transportation, fuel processing)), the amount of CO₂ emissions released was found to be 2036 tCO₂/year. Implementing the biomass power plant leads to savings of 5871 tCO₂/year.

2.3. Survey Results

Figure 8, Figure 9, Figure 10, Figure 11 and Figure 12 present the results regarding consumer attitudes towards resource accessibility, investments in cogeneration, financial mechanisms, expected benefits and the environmental aspects based on the questions adopted in Section 2.2. The results highlight the interests, barriers and consumer expectations related to the implementation of these systems.

The results indicate that most respondents consider waste biomass to be the main source for cogeneration. Approximately half of those surveyed have full access to the required materials, while 35% have limited access and only 15% lack access to suitable raw materials (Figure 8). This points to a reliable yet regionally imbalanced supply base, highlighting the need for improved logistics solutions.

The results, shown in Figure 9, indicate that 75% of the participants state that they would invest in combined energy production technologies if financial incentives were available. The greatest interest is in small- (up to 500 kW_e—47%) and medium-sized (500–1000 kW_e—48%) systems, while only 21% show interest in large installations. This emphasizes the demand for more flexible and scalable solutions that are better suited to local needs and offer shorter payback periods. The study also found that facilities with a capacity of up to 1000 kW_e are more desirable because they are easier to manage and balance. On the other hand, the size of the installation (1156 kW_e) outlined in the manuscript was suggested because of the available grid capacity in this rural area, considering the presence of biomass.

The survey results indicated in Figure 10 reveal important insights into both the financial mechanisms that could support cogeneration investments and the main barriers to implementation. Subsidies are seen as the most effective financial incentive (35%), followed by green certificates and tax incentives (both around 28%). However, limited resource availability (42%) and high initial costs (35%) emerge as the primary obstacles, alongside a lack of information (25%). These findings underscore the need for comprehensive support measures—particularly logistical, financial and informational—to facilitate the wider adoption of cogeneration technologies.

Figure 11 shows that, according to the survey results, respondents perceive cogeneration as offering environmental and economic benefits. Environmentally, the most recognized advantages are the reduction in carbon emissions (34%) and waste management improvements (41%).

Economically, key expectations include the reduction in energy costs (up to 34%), the generation of revenue from green certificates (33%) and the improvement of competitiveness (up to 33%). These findings suggest a balanced recognition of cogeneration’s dual role in promoting sustainability and enhancing economic performance, with slightly higher emphasis placed on waste management and cost efficiency.

The responses to questions 9 and 10 (Figure 12) show that there is a strong link between technical awareness and environmental responsibility among those surveyed. A significant portion of the respondents report being well informed about cogeneration systems and their applications, indicating that this is no longer a niche or unfamiliar technology within the sector.

This level of awareness suggests a readiness for adoption and a solid foundation for the further development of cogeneration projects. At the same time, the environmental aspect emerges as a key priority in energy-related decision-making. The combination of high awareness and environmental prioritization reflects a mature and forward-looking attitude toward energy solutions.

These findings underscore a critical opportunity: with appropriate policy frameworks, incentives and logistical support, Bulgaria has the potential to significantly expand its adoption of low-emission, high-efficiency cogeneration technologies in the near future.

3. Discussion

The entire plant (wood-fired boiler coupled with an ORC module) achieved an energy efficiency of up to 85%, which is a significant advantage compared to conventional technologies (conventional thermal power plants), which reach only 30–40%. ORC CHP technology typically has an electrical efficiency of up to 17% and a thermal efficiency of 75%. In contrast, CHP power plants that use wood biomass have an overall efficiency of no more than 80% [51]. This corresponds to the conclusions of the authors in [52], who note that cogeneration systems can double the energy efficiency compared to standard methods for producing electrical and thermal energy. Additionally, the authors in [53] emphasize that combined energy production is most effective when integrated with local resources, which is confirmed in this study. The reduction in CO₂ emissions in about 5800 t highlights the environmental benefits of the proposed system. This result aligns with the research in [54], which found that burning waste biomass is a carbon-neutral process and can reduce carbon emissions by up to 90% compared to fossil fuels. The expected revenue of over EUR 600,000 annually is in line with the study in [55], which highlights that the investments in biomass cogeneration technologies typically achieve a return on investment within 5–7 years. The stability of cash flow and long-term sustainability are also confirmed by the authors in [56]. The implementation of the Organic Rankine Cycle for the efficient conversion of waste heat into electricity aligns with the results in [57], which notes that ORC technology offers more than 10% higher energy efficiency compared to traditional turbines in low-temperature applications.

The main problem with operating such installations is sourcing the raw material (waste biomass). According to an expert report from state forestry companies, the annual amount of utilized waste biomass from forest clearing alone is below 30%, indicating serious potential for utilization. Over the past 5 years, a team has been working on introducing such waste biomass installations with a capacity of 5–10 MW, totaling 50 MW. Three of the facilities have ORC-based CHP power systems. The analysis used a similar approach; of course, the greatest risk lies in the supply of waste biomass, particularly during the winter months when there is heavy snowfall and access is difficult. The probability of a price change based on 10 years of data was also considered, indicating low to medium risk. For this reason, the main goal is to build these energy facilities close to sites where waste biomass is extracted.

The suggested Organic Rankine Cycle (ORC) technology was selected over conventional steam turbines and gas engines due to its superior performance in recovering energy from low-temperature heat sources. These are commonly encountered in biomass-based energy systems. In contradistinction to conventional steam turbines, ORC systems are capable of operating efficiently with lower-grade thermal inputs, rendering them especially well suited for decentralized applications and waste heat recovery. Additionally, ORC units typically have simpler mechanical configurations, lower operational costs and greater reliability. A further pivotal benefit lies in their augmented adaptability to variations in the quality and composition of waste biomass fuels, a prerequisite for ensuring stable and efficient operation in real-world conditions where fuel characteristics may fluctuate over time. These features make ORC technology a strong and efficient choice for sustainable energy conversion in biomass-integrated multi-energy systems.

The present study emphasizes the social and economic benefits, including job creation and the integration of local resources. These aspects are discussed in [58], which notes that local cogeneration systems promote regional development and sustainable resource management. The authors in [46] propose focusing on the development of biomass pre-treatment technologies to improve its calorific value and reduce unwanted side effects during combustion. Additionally, research in [52] highlights the importance of integrating cogeneration systems into smart energy grids, which would enhance their operational flexibility and security.

The results of the present marketing research show a high potential for the implementation of cogeneration systems using waste biomass in Bulgaria, based on strong interest from industrial, municipal and small enterprises. This is supported by 75% of the respondents, who are willing to invest, provided that financial incentives such as subsidies or green certificates are available. The data confirm the importance of financial mechanisms as a key factor in overcoming the barriers to implementation, similar to the studies in [58,59], which emphasize that subsidies and tax incentives are crucial for promoting green investments in the energy sector.

The environmental benefits, such as reducing carbon emissions and waste management, are identified as important by the respondents, which aligns with the results in [60], which note that reducing carbon emissions is a leading motivator for the adoption of cogeneration technologies in Europe. In our study, 85% of the respondents consider the environmental aspect to be “very important” or “important,” which is comparable to the researchers’ studies in [61], who emphasize the growing importance of sustainability for industrial and municipal consumers.

A relatively small part (21%) of the respondents consider investment in large cogeneration systems likely, which indicates that there is greater interest in small and medium installations. This aligns with the authors’ research in [62], who found that small cogeneration systems are more suitable for local applications and have shorter payback periods.

Furthermore, 50% of the participants in the marketing survey report having direct access to the necessary resources, while 35% note partial access. This result corresponds to the studies in [63], which highlight that the availability of raw materials is a key factor for the success of cogeneration technologies. The lack of resources is identified as a significant barrier in 42% of the survey results, which matches the conclusions of the authors in [64], who emphasize the importance of logistical infrastructure for sustainable energy production.

The economic benefits, such as energy cost reduction and revenue generation from green certificates, are also highly rated by the respondents, which is consistent with the studies in [65], which demonstrate that economic advantages are a leading motivator for the implementation of cogeneration.

In the context of multi-energy systems, the benefits of energy and emissions sharing are of significant importance, as they contribute to improved operational efficiency, environmental sustainability and substantial cost savings. Mechanisms such as emission trading schemes and white certificates further enhance the value of such sharing by providing economic incentives for reducing emissions and improving energy efficiency [66]. In a district energy network where several buildings or facilities are connected, waste heat from electricity generation (CHP plants) can be shared with nearby residential or commercial buildings. This sharing improves overall energy efficiency and reduces fuel consumption and emissions. In many EU countries, utilities or companies that exceed mandated energy efficiency improvements can earn white certificates. These can be traded or sold to companies that fall short, encouraging widespread investment in energy-saving technologies. In a local energy community using a microgrid, excess biomass generated energy by one facility can be shared or sold to others within the network. This balances supply and demand locally, improves efficiency and reduces reliance on fossil fuel-based grid electricity.

4. Conclusions

This study presents the results of the comprehensive design of a cogeneration system based on the Organic Rankine Cycle and a marketing survey aimed at assessing the interest in implementing such technologies in Bulgaria. The proposed system combines a wood-fired boiler with an ORC module to produce electricity and heat in a combined manner. The high efficiency of the system is achieved by using three additional economizers for heating the oil and by the high efficiency of the ORC module (25%). The waste biomass consumption amounted to 2 t/h, providing input power of the system of about 8800 kW. The electric power produced by the ORC module is 1156 kW, and the thermal power amounts to 3660 kW. Additionally, economizers were installed to capture the exhaust thermal energy from the flue gases for further heating of the oil. The additional amount of captured energy is 2664 kW [67]. Thus, with losses in the proposed system of 8% (704 kW), the efficiency of the installation is estimated at 85%. The designed system is specifically created to utilize waste raw materials, demonstrating high energy efficiency of up to 85% and economic profitability with projected annual revenues of approximately EUR 650,000. Also, it significantly reduces the carbon footprint, saving over 5800 t of CO₂ yearly. These characteristics position it as a sustainable and innovative alternative to traditional energy technologies.

In parallel with the technical development, the conducted marketing survey reveals a high readiness for investment in cogeneration systems among industrial and municipal enterprises. The results show that 75% of the respondents express interest in such technologies, provided that appropriate financial incentives, such as subsidies or green certificates, are available. The survey also highlights that small- and medium-sized cogeneration systems (with capacities up to 500 kW and 500–1000 kW) are the most preferred, with 47% and 48% of the respondents expressing interest in each, respectively. Large systems (over 1000 kW) have limited applicability, with interest in them being only 21%. Half of the respondents have direct access to the necessary raw materials, while 35% report partial access, indicating the presence of a stable but unevenly distributed resource potential. From an environmental perspective, the cogeneration system offers significant advantages, including a reduction in carbon emissions, efficient waste management and improved energy independence. In total, 85% of the participants in the survey consider the environmental benefits as “very important” or “important”, reflecting the high awareness and commitment of businesses to sustainable solutions. Economic barriers, such as high initial costs (35%) and limited access to resources (42%), remain key challenges. These require targeted efforts to overcome through appropriate financial policies including subsidies, tax incentives and improvements in logistical infrastructure. It should also be noted that the results may overstate market readiness due to the participants being selected from sustainability programs.

In conclusion, the developed cogeneration system and the accompanying marketing study demonstrate significant potential for the implementation of these technologies in Bulgaria. The combination of high energy efficiency, economic profitability and environmental benefits lays the foundation for the future development of cogeneration systems for the utilization of waste raw materials.