## 1 Introduction
The steam cycle involves generating steam by burning biomass in a boiler and then using the steam to drive a steam turbine. The steam used to drive the turbine condenses and is directed back to the heat exchanger located in the boiler. The ORC has two cycles: one for the thermal oil and the other for the organic fluid. The heat released during biomass combustion is transferred through the oil circuit via an exchanger to an organic fluid that evaporates at high temperatures and pressures. The ORC system consists of four main components, namely the pump, evaporator, turbine and condenser. The superheated organic vapor is expanded in the turbine, then condensed in the condenser and returned to the circulation pump to start a new cycle. The condenser can function as a heat exchanger or for remote heat transfer at low temperatures. The condensed organic liquid is pumped through the regenerator to the evaporator. Heat in such installations is usually supplied at a temperature of about 300 \({}^{\circ}\)C, and condensation occurs at a temperature of about 90 \({}^{\circ}\)C.  
Stirling and Ericsson engines are heat engines. They differ primarily in their working fluids. In the Stirling engine, it is a liquid, and in the Ericsson engine, it is air. Over the course of the analyses carried out by [PERSON] et al. [10], information was obtained that, among the mentioned technical solutions, the steam cycle using a steam turbine is particularly suitable for use in high-power installations, preferably above 2000 kW. In turn, ORC systems are most recommended, according to the authors, for systems with medium power, i.e., from 200 to 2000 kW. The reason is the significant cost of this type of installation and the degree of expansion and current technological maturity of these systems, which were usually not designed above a power of 2000 kW. In turn, solutions based on heat engines (Stirling, Ericsson) are recommended by the authors for micro-cogeneration. The reason is the simplicity and familiarity of these systems. In the case of micro-cogeneration, ease of servicing and low installation costs are crucial [10]. The agricultural industry's interest in small-scale biogas production allowed design companies to develop concepts for mobile installations, often with a simple container structure, that are ready to be utilized in the economic infrastructure. Micro-biogas plants most often include the following elements [11]:  
1. Point of acceptance of solid and liquid substrates;
2. A set of pumps mixing and dosing substrates;
3. Fermentation chambers equipped with a heating system, mixing and removing post-fermentation waste;
4. Biogas tank;
5. Desulfhurizer;
6. Instrumentation for controlling the process and the control system;
7. Pipe and cable installations;
8. Cogeneration engine;
9. A torch burning excess biogas;
10. Technical building. Designing a specific micro-biogas plant is basically carried out individually for each farm. According to one of the variants, meeting the demand for substrates for a 50 kW micro-biogas plant requires sowing approximately 30 ha of land with plants intended for biogas production. The use of waste substrates reduces the required area accordingly. The post-fermentation residue is used to fertilize land on one's own farm. The biogas plants implemented so far are characterized by great diversity, both in terms of the devices installed, the amount of biogas produced and the energy obtained from it. The very principle and method of obtaining agricultural biogas allow for such differentiation. The main idea behind the creators of the agricultural micro-biogas plant container, version number 7 (KMR 7) (Figure 1a), was to adapt its structure to the realities of Polish agriculture [12]. The micro-biogas plant has been adapted to handle residues from agricultural and livestock production, as well as silage from energy crops grown for specific purposes.