New technologies based on the anaerobic digestion process make it possible to manage problematic waste. Methane efficiency depends largely on the level of the hydration of the substrates used for biogas production and their ability to decompose easily. The aim of this study was to present the current state of knowledge and practices in substrate hydration characteristics, focusing on pretreatment methods as the preferred method for improving efficiency. The paper discusses issues related to the degree of hydration of substrates in the context of their use in biogas plants. Reference was also made to topics related to the transportation and logistics of raw material supply regarding environmental impact. Biogas plant projects should be expanded to include an element related to assessing the impact of raw material deliveries on the immediate environment. Previous papers have not sufficiently analyzed the aspect related to the hydration of substrates used in anaerobic digestion processes. The presented and discussed research results can be implemented to optimize biogas plant water management processes. By replacing standard feedstock transportation methods with a pipeline, the environmental impact can be reduced by nearly ten times.

The management of biodegradable waste from various sectors of economy is an essential element in terms of environmental protection. The paper discusses issues related to the possibility of bio-waste treatment using anaerobic digestion technologies and composting processes, highlighting the conditions for the processes and their advantages and disadvantages. The challenges of overproduction of bio-waste faced by highly developed countries around the world are also presented. Research showed that the anaerobic digestion of this waste combines both biofuel production and a circular economy. The popularity of this method is linked, among others to a low cost of raw materials and wide range of possible uses for biogas (i.e. electricity, heat, or biomethane). In addition, an alternative bio-waste management option, compost production, was discussed. The study aimed to compare anaerobic and aerobic bio-waste management processes.

The implementation of forest management generates logging residue which can be used in several ways. One of the option is to use of logging residue in the composting process. Therefore, this study determined the possibility of producing compost based on logging residue and the produced fertilizer used to fertilize forest nurseries. Pine chips and sewage sludge were used for carrying out the study. The compost, as well as the leachate produced during composting, were characterized by high NPK content. The leachate collected at the end of the experiment was characterized by nitrogen content of approximately 6500 mg‧dm^-3, phosphorus of approximately 450 mg‧dm^-3, and potassium of approximately 500-700 mg‧dm^-3. In contrast, the compost produced contained approximately 0.57 g‧kg^-1 nitrogen, approximately 0.39 g‧kg^-1 phosphorus, and approximately 0.24 g‧kg^-1 potassium. The disadvantage in terms of the usefulness of the resulting fertilizer in forest nurseries is its pH, which exceeded 9.0.

The aim of this study was to conduct a comprehensive economic and energy efficiency analysis of selected digestate management methods, considering their implications on operational costs and resource management. To achieve this aim, the study focuses on a comparative assessment of different digestate management methods, including land application, mechanical separation, the composting process and pellet production. The economic analysis involves the evaluation of the initial investment, operational expenses, and potential revenue streams associated with each method. The most economical and popular solution of digestate management is direct use as fertilizer, with total costs of 1.98 EUR·Mg⁻¹. All of the other methods involve higher digestate management costs, respectively; for separation it is 2.42 EUR·Mg⁻¹, for composting it is 2.81 EUR·Mg⁻¹. The process that is the most energy-intensive, but profitable, is the production of pellets from digestate, resulting in profits of 334,926 EUR·year⁻¹. It should be noted that the other analyzed methods of digestate management also bring many environmental benefits, affecting sustainability and reducing emissions. The results of this research will contribute unique data on the feasibility of managing the digestate and its fractions. The calculations of economic and energy values for different strategies will allow for the optimization of the overall performance of the biogas plant, thus promoting a circular economy.

Digestate is a product with valuable fertilizing properties, remaining after the anaerobic fermentation process. An essential feature of the substance in question is its high water content of up to 97%. To improve the fertilizer value of the digestate, it is necessary to dehydrate it to produce a concentrated product. This paper determined the possibility of dewatering the digestate using an innovative reactor design. The study, conducted on a laboratory scale, used digestate from a Polish biogas plant. The dewatering technique described in the paper is based on the evaporation and condensation of water vapor on the inner surface of the reactor dome. The condensate accumulated on the leach trough and was directed to a storage tank. During the weeks of testing, 11.5 kg of condensate was separated from the initial weight of the digestate (32 kg), with a dry weight of 6.11%. The resulting condensate from dehydration had an average pH value of 9.0 and an average ammonium nitrogen content of 2.07 g∙kg⁻¹. The economic calculations made in the paper allowed for estimating the expected savings associated with the management of digestate in Poland. The research showed the proposed technology’s high potential for dewatering digestate under laboratory conditions.

Approximately 30% of the food produced worldwide is wasted, and a substantial share of municipal food waste still contains non-biodegradable packaging material after sorting. This study investigated an aerobic biodrying process for reducing the moisture content of mixed food-waste fractions, containing varying proportions of green biomass, vegetables, kitchen waste, and packaging-derived plastics, in order to increase their calorific value and obtain a refuse-derived fuel (RDF). Four substrate variants (K1–K4, including a control without added plastics) were biodried in laboratory-scale bioreactors. Process temperatures exceeded 70 °C in all variants, and the addition of plastics increased both the cumulative and the average temperature relative to the control. The plastic fraction recovered after biodrying showed the largest increase in calorific value, reaching over 15 MJ∙kg⁻¹, while the AT4 respiration activity of the separated compost fraction decreased to around 10 mg O₂ g⁻¹ DM in all variants, indicating good storage stability. The results suggest that pre-treated plastics did not adversely affect the biodrying process and, owing to their structuring properties, may support biological decomposition of the remaining biomass; these preliminary, single-run findings should be confirmed in replicated trials.