This paper presents the origins of marine steam turbine application on liquefied natural gas carriers. An analysis of alternative propulsion plant trends has been made. The more efficient ones with marine diesel engines gradually began to replace the less efficient plants. However, because of many advantages of the steam turbine, further development research is in progress in order to achieve comparable thermal efficiency. Research has been carried out in order to achieve higher thermal efficiency throughout increasing operational parameters of superheated steam before the turbine unit; improving its efficiency to bring it nearer to the ideal Carnot cycle by applying a reheating system of steam and multi stage regenerative boiler feed water heating. Furthermore, heat losses of the system are reduced by: improving the design of turbine blades, application of turbine casing and bearing cooling, as well as reduction in steam flow resistance in pipe work and maneuvering valves. The article identifies waste energy sources using the energy balance of a steam turbine propulsion plant applied on the liquefied natural gas carrier which was made out basing on results of a passive operation experiment, using the measured and calculated values from behavioral equations for the zero-dimensional model. Thermodynamic functions of state of waste heat fluxes have been identified in terms of their capability to be converted into usable energy fluxes. Thus, new ways of increasing the efficiency of energy conversion of a steam turbine propulsion plant have been addressed.

The necessity of developing the production of biogas and digestate at Ukrainian sugar factories focused on the further sale of biomethane in the energy market and for its own needs is substantiated, which will partially ensure the energy security of the state under martial law. The volumes of sugar beet cultivation are determined, and the potential volumes of biogas production from the waste of Ukrainian agro-industrial complexes are investigated. A model of the functioning of a production bioenergy cluster based on a sugar factory has been developed and proposed. As a result of the study, it was found that a tangible way to increase the level of energy autonomy of the processing industry of the agro-industrial complex of Ukraine is the production of biogas by anaerobic digestion and its subsequent purification to the state of biomethane. To produce this type of biofuel, the use by-products of agriculture, agro-industrial processing enterprises, and organic waste from territorial communities where sugar factories are located is advisable. At the same time, as the analysis of resource potential shows, modern methane generation technologies allow using a wide range of biomass as a raw material base, which can be obtained both from production activities (non-core (non-target) products) and from household waste in general, which is one of the methods of solving the problems of their utilization. It has been determined that the use of advanced technologies for the transportation of liquid digestate and its injection will reduce the cost of application, increase the absorption in the soil, and the use of biodiesel will reduce transportation costs.