Spent mushroom substrate (SMS), often overlooked as waste despite its richness in organic matter and mineral micronutrients, is increasingly recognized as a versatile resource for various applications. This study examines the potential of SMS as a feedstock for biogas production. A periodic mesophilic fermentation regime at 36.0 ± 0.1 °C was selected to conduct the experiments, after mixing the substrate with the inoculum, over a period of 38 days. The experimental results showed an average biogas yield of 292.7 Nm³/t of fresh SMS, with a methane concentration of 66.2%, making SMS a competitive resource for renewable energy production. This approach not only offers economic benefits for agricultural and energy sectors, but also supports environmental sustainability by promoting waste reduction and resource valorization.

The study aims to define the potential and technological aspects of the digestate treatment for its application as a biofertilizer. Life cycle assessment methodology was used in terms of digestate quality management. The potential of nutrients, organic carbon, and useful microelements in the digestate allows for its consideration as a mineral fertilizer substitute and soil improver. The valorization of digestate as fertilizer requires quality management and quality control. Based on the research focus, the successful soil application of digestate post-treatment technologies was analyzed. Among the different commercial options for digestate treatment and nutrient recovery, the most relevant are drying, struvite precipitation, stripping, evaporation, and membranes technology. Comparing the physical and chemical properties of the whole digestate, separated liquid, and solid liquor fractions showed that in the case of soil application of granular fertilizer, nutrients from the digestate are released more slowly than digestate application without granulation. However, realizing this potential in an economically feasible way requires improving the quality of digestate products through appropriate technologies and quality control of digestate products. To support the manufacture of quality digestate across Europe, the European Compost Network developed a concept for a pan-European quality assurance scheme.

Perspective directions for the development of motor biofuels market in Ukraine are considered. It is shown that Ukraine has a significant potential for the production of liquid biofuels for the transport sector. Today, it is mainly biodiesel and bioethanol of the first generation, since the technologies for obtaining advanced biofuels from lignocellulosic feedstocks are not yet sufficiently developed in the country. However, as these technologies improve, one of directions for the development of motor biofuels market will be the expansion of production opportunities for second generation (advanced) biofuels with a significant share of their export to EU countries. Directive (EU) 2018/2001 on renewable energy sources (RED II) limits the share of 1st generation biofuels in achieving the goals for the consumption of renewable energy in transport. The share of such biofuels in a certain EU country can be no more than 1 % higher than the share of these biofuels in the gross final energy consumption of road and rail transport of that country in 2020, but no more than 7 %. For Ukraine, this means that the share of 1st generation biofuels in the final energy consumption in transport in 2030 cannot exceed 1.85 %, since in 2020 this indicator was 0.85 %. A possible option for solving this problem is to coordinate with the European Commission the issue of increasing the quota of 1st generation biofuels for Ukraine to 7 % in 2030, which is equivalent to the consumption of 503 ktoe/y. In the future, it seems appropriate to develop the production of advanced bioethanol from byproducts of grain corn cultivation as well as advanced biodiesel from oilseed energy crops grown on unused agricultural land. According to RED II, such biodiesel is not subject to restrictions on biofuels produced from food or feed crops. Production and consumption of biomethane is also a promising direction for the introduction of renewable energy in transport. It is shown that the total potential of biogas production in Ukraine is currently 8.16 Mtoe/y, of which a quarter can be allocated for the transport needs. By 2050, the production potential of biogas as a motor fuel may increase to 4.7 Mtoe/y, mainly due to the use of cover crops as feedstock to obtain biogas. Bibl. 21, Tab. 4.

The purpose of the publication is a comprehensive analysis of biomass as a renewable energy source, a review of modern technologies for the production of heat and power from biomass, as well as solid, liquid and gaseous biofuels. Currently, biomass ranks fourth in the world in terms of the use for energy. Sustainable development of bioenergy makes it possible to reduce Ukraine′s dependence on expensive imported energy carriers and to ensure the efficient use of local resource potential.

The purpose of the work is a comprehensive assessment of Ukraine’s bioenergy potential. The task of the work is to develop recommendations for the practical implementation of promising directions for the potential utilisation. The research methods include calculations, study and analysis of literature, statistics and other data. The availability of considerable biomass potential for the production of various types of biofuel and energy is one of the main prerequisites for the successful development of bioenergy in Ukraine. Results of the assessment based on 2021 data show that the potential of biomass for energy in the country amounts to nearly 26 Mtoe/year. A comprehensive assessment of the potential was carried out for such components as solid biomass, biofuelі and biogas. Sources of solid biomass are various agricultural residues, various types of wood biomass and energy crops (provided they are grown on unused agricultural land). Solid biomass in the amount of more than 16 Mtoe/year is the largest component of the country's biomass energy potential accounting for 62% of the total. Expert assessments indicate the possibility of increasing this potential to about 44 Mtoe/year in the period until 2050. A scenario for the long-term use of the biomass potential for energy and biofuel production has been developed taking into account sustainability issues. To implement this scenario, it is necessary to overcome a number of barriers existing in the bioenergy sector, primarily the main ones. It also seems necessary to temporarily liberalize for Ukraine the strict sustainability criteria established by the EU RED II. This mitigation should include postponing the requirement to reduce greenhouse gas emissions (65% for biofuels and biogas for transport produced in installations that started operation from 01.01.2021); establishing a special limit for Ukraine until 2030 on the use of energy from first-generation biofuels in transport (up to 7%); expanding for Ukraine the list of feedstock for the production of advanced biofuels, including regulation of possibility to obtain raw material for biofuel production on polluted, unused, low-productivity and degraded lands.

The purpose of the work is to review technologies and analyze the possibility of introducing microalgae cultivation at biogas/biomethane plants while simultaneously obtaining of additional biomethane yield and utilization of the liquid fraction of the digestate. Modern technologies, types and equipment for growing microalgae on the liquid fraction of digestate of biogas plants were considered and analyzed. The current situation of biogas/biomethane production in Ukraine and disposal of the liquid digestate fraction is presented. The chemical composition of the digestate and the methods of its preparation for the cultivation of microalgae were analyzed. Recommendations and a block scheme for technology implementation at a biogas/biomethane plant have been developed. Today, one of the most economically profitable options for Ukraine is the production of biomethane. On the other hand, there is a clear need for innovative, low-cost, safe production of biomethane using alternative, high-yield biomass that can utilize waste feedstock and also sequester carbon. Microalgae is a promising biomass that can convert nutrient-rich digestate into valuable biomass for biofuel and biodiesel production and is considered as a double-counting feedstock (RED II Directive, Annex 9). Microalgae demonstrate high photosynthetic efficiency and productivity (almost twice that of terrestrial plants) and are promising for advanced biomethane production. Integrating microalgae harvesting into an anaerobic digestion plan is the most efficient and promising way to harvest microalgae, as most of the components required for microalgae harvesting are almost free under the following conditions: process heat, CO₂, nutrients, water, transport of microalgae to end use. Electricity alone for lighting is not free, but can be minimized by using solar energy, energy storage and biogas electricity. Algae biomass can potentially increase the annual production of biomethane at an existing plant by 9.4%, as was achieved for a similar project in Sweden [33].