Biogas production is an important component of sustainable energy management. In addition to energy-rich biogas, this process also generates solid waste in the form of digestate. The management of this stream has been problematic for many years. One promising method of utilizing this fraction seems to be incineration under controlled conditions. This paper presents an analysis of mixtures of different digestates to assess their suitability for incineration. Four digestates based on corn silage CS and apple pomace AP were used as test fuel. The ultimate and proximate analysis showed that this fuel deviates from the standards accepted for pure biomass, but was found in other fuels, especially those treated as waste. This materials can be a valuable source of energy, but combustion needs be undertaken in special units. Moisture content of investigated digestate-type ranges from 11.9–12.2% and ash content ranges from 8.2% to 11.6%. This could lead to ash sintering and slugging problems, which are problematic, especially because it is not designed for such types of fuel boilers. The study showed correlations between the elemental composition and the course of basic combustion processes. The ultimate analysis of all mixtures shows that the shares of major elements looks similar. These results are connected with the thermogravimetric analysis TGA, which shows similar thermal decomposition for all four mixtures. It is valuable information because, in this special case, when we have mixtures of corn silage and apple pomace originated digestates, the changes in the ratio CS:AP will not affect combustion significantly.

The priority task of the milk processing industry is in reducing the specific energy consumption of milk fat dispersion while simultaneously ensuring a high dispersion of milk emulsion. One of the possible ways to solve this problem is by developing and implementing a little-studied jet milk homogenizer of the slot type. In it, homogenization occurs by implementing the method of the separate feeding of cream, which allows creating the maximum difference between the speeds of skim milk and cream, which is a necessary condition for effective dispersion. Analytical dependences have been found that relate power and specific energy consumption to the performance of a milk homogenizer with the separate cream supply, the diameter of the annular gap, the fat content of normalized milk and cream, and the cream supply speed. The rational value of the fat content of the cream used for homogenization is analytically substantiated; in order to reduce the specific energy consumption of the process, their fat content should be higher than 20%. The most significant increase in the energy costs of dispersion is observed when processing milk with a fat content of less than 3–4%, while the use of cream with a fat content of less than 20% leads to a multiple increase in the energy costs of the process. The research results indicate the hyperbolic nature of the dependence of the homogenizer power on its productivity. Supplying the cream through an annular gap of small diameter allows reducing the main component of dispersion energy costs by eight times. The obtained data indicate the existence of a deviation within 5–10% of the experimental power values from the analytical ones, which is explained by the influence of the efficiency of pumps, drives, and losses in the connecting fittings.

The combustion of waste biomass is becoming a key challenge for the energy sector, especially in times of growing energy demand and increasing environmental awareness of society. Processing such fuels is usually demanding. Mathematical modeling makes it possible to adapt the course of the process. The best option is to use appropriate fuel mixtures. The aim of this work was to develop a simple model that would allow the pre-selection of the mixture of two types of digestate. Residues from methane fermentation of maize and apple pomace were used in the study. The paper presents both a mathematical model and laboratory tests. The practical part was to check the validity of the model estimates. The model works on the basic data from physicochemical analysis. Laboratory tests included combustion of the samples of different mixtures. We used image analysis of thermograms to determine changes during combustion, which allowed us to determine when and where the main combustion occurs. Results show that a simple mathematical model is able to estimate the course of the combustion of a fuel particle.