Three coarse herbaceous energy plants—such as Miscanthus (Miscanthus sinensis), sida (Sida hermaphrodita Rusby) and cup plant (Silphium perfoliatum L.)—were grown and investigated in the experimental fields of Vytautas Magnus University Agriculture Academy, and the technical means of plant processing and utilization for solid biofuel were investigated. The physical–mechanical properties and quality indicators (moisture content, biometrical properties, density, and resistance to compression) of coarse stem herbaceous plants milled and compressed into 6 mm diameter pellets were investigated. The moisture content of the tested pellets was sufficiently low and ranged from 8.7% to 9.6%. The highest density was that of sida pellets (1072.3 ± 43.4 kg m⁻³ DM), and the lowest density was that of Miscanthus pellets (713.5 ± 67.1 kg m⁻³ DM). In order to evaluate the influence of moisture content on the properties of biofuel pressed into pellets, the density and the destructive compressive force of the different-moisture pellets were investigated and their change in the range of 5–15% pellet moisture content was evaluated. Criterion k was calculated to determine the effect of moisture on the pellet quality indicators (density, destructive compressive force, and lower heating value), and the following results were obtained: the highest influence of moisture on density was observed in sida (k = 34.280), on destructive compressive force in Miscanthus (k = 14.5), and on the lower heating value, also in Miscanthus (k = 0.198). After a comprehensive investigation and evaluation of these properties, an empirical model suitable for practical use was developed and prepared. Emissions of harmful gases, such as carbon monoxide, carbon dioxide, and nitrogen oxides, were determined when various coarse stem herbaceous energy plants were burned. The determined emissions of harmful gases into the environment did not exceed the permissible values.

Multi-crop plants (fibrous hemp, maize, and faba bean) can potentially be an alternative to wood biomass pellets, but there is no detailed knowledge to support the suitability of this biomass for solid biofuel production. The aim of this study is to analyze and justify the suitability of multi-crop plant biomass for the production of biofuel pellets and to assess the environmental impact of burning them. This paper presents studies of physical-mechanical, thermal, and chemical characteristics of biofuel pellets from multi-crop plants and emissions during their combustion under laboratory conditions. The main parameters of the produced pellets were determined according to international standards, which are detailed in the methodology part. The length of the produced pellets ranged from 17.6 to 26.6 mm, and the diameter was about 6 mm. The density of wet pellets varied from 1077.67 to 1249.78 kg m⁻³. The amount of ash in the pellets varied from 5.75% to 8.02%. Determined lower calorific value of all pellets was close to 17.1 MJ kg⁻¹. The lowest CO and C_xH_y emissions were determined when burning MIX2-1 pellets (biomass of the binary crop); their values were 572 and 29 ppm, respectively. The lowest content of CO₂ was determined when burning S-Mz pellets (mono crop biomass), and it was 3.5%. The lowest NO_x emissions were also determined when burning the pellets of this sample, with a value of 124 ppm. Research results show that multi-crop plants are a suitable raw material for the production of solid biofuel, the burning of which does not cause negative consequences for the environment.

Harvesting of high-moisture corn ears poses a challenge due to the high level of grain damage. In the present study, a series of concaves adapted to moist corn ears threshing was developed and evaluated. The key improvements include a concave arc shape and oblique crossbars to reduce corn grain damage and threshing losses. Results show that the geometrical shape of the concave arc and its crossbars have a significant influence on the grain detachment from the ears, grain separation through the concave, and grain damage during the threshing process of moist ears of corn. Studies show that replacing the concave rounded crossbars with oblique ones can increase threshing performance of moist corn ears. A concave with an Archimedes’ spiral arc and oblique concave crossbars is an effective approach to improve corn grain quality and reduce harvest losses due to grain damage. We identify the optimal design for threshing corn ears as an experimental concave with an Archimedes’ spiral arc of 8 mm height, with 19 mm wide crossbars of the concave with an oblique working plane (tilt angle 25°). This design achieves minimal threshing grain losses (0.03%) when threshing moist ears (grain moisture content ~35%), and damaged grain in the threshing apparatus does not exceed the permissible limit of 3% at an ear feed rate of 16.8 kg s⁻¹.

The combine harvester (CH) is one of the most important machines with the most powerful engine used in the agricultural sector. It consumes significant amounts of diesel fuel and harms ambient air by releasing emissions. This study examines the telematics data of CHs (models with axial threshing apparatus) collected between 2017 and 2020. The time spent in various operating modes of CH, the fuel consumption, and the negative impact on the ambient air (expressed in global warming potential–(GWP)) were calculated. Field tests using the same CH model were also performed to confirm the collected telematics data’s values. Possibilities to minimize fuel consumption and air pollution by selecting the correct use of technological operations are evaluated. Telematics data analysis results showed that the CH spends ~18% and ~13% of the time in the idle and transport modes, respectively. It was also found that ~12% of diesel fuel was consumed outside the direct harvesting mode, amounting to 4.7 t year⁻¹ of GWP per machine. Dual telematics/field studies showed that the optimal use of the CH in idle and transport modes could reduce the amount of pollutants released into the environment in terms of GWP by 1.3 t year⁻¹ for one machine. Field tests have also shown that the GWP per ton of wheat harvest highly depended on the CH driving speed during harvesting. The optimum speed was determined as 4 km h⁻¹, and the wheat grain and straw feed rate was determined as 24 kg s⁻¹.

Application of hydroponic systems in feed production has not been extensively studied. Therefore, there is insufficient data on the effect of the slope of hydroponic growing trays used in the nutrient film technique on wheat fodder yield and its qualitative parameters. The slope of the trays has only been studied for food crops. This study conducted experimental research using a nutrient film technique hydroponic fodder growing device to evaluate the impact of growing tray slope angle on hydroponic wheat fodder production. The slope angle of the growing trays was changed from 2.0% (1.15°) to 8.0% (4.57°) with increments of 1.5% (0.86°). This research used two different light sources for wheat sprout illumination: indoor lighting (fluorescent lamps) and light-emitting diode illumination. In addition, two nutrient solutions were used for sprout irrigation: tap water and a solution enriched with macro- and microelements. Experimental studies confirmed the hypothesis that the slope angle of growing trays significantly affects the yield of wheat fodder grown for seven days. Analyzing the results, we found that the highest yield of wheat fodder after seven days of cultivation was achieved with growing trays sloped by 6.5% and using indoor lighting. In addition, we achieved the highest wheat fodder dry matter content using a 6.5% slope angle. Experimental studies also confirmed the hypothesis that using macro- and micronutrients in the nutrient solution does not significantly affect the yield of wheat fodder grown hydroponically for seven days.

The article presents the results of a study on the preparation and use of faba bean waste and potato peel pellets for energy purposes. Physical and mechanical characteristics (moisture, density, ash content) of faba bean waste and potato peel pellets were investigated. The largest fraction of flour was formed on a sieve with 1 mm holes: faba bean waste—28.2 ± 2.02 g, potato peels—29.09 ± 0.73 g. For this experiment, samples were taken by mixing faba bean waste (four variants) and potato peel in the ratio of 1:1; 1:2; 1:3; 1:4 by volume (12 samples). It was found in this study that the density of pellets (DM) ranged from 1226.22 ± 13.88 kgm⁻³ to 1349.79 ± 6.79 kgm⁻³. The pellet moisture ranged from 6.70 ± 0.04% to 3.64 ± 0.13%. The lower calorific value of dry fuel pellets ranged from 15.27 ± 0.43 MJkg⁻¹ to 16.02 ± 0.50 MJkg⁻¹. The ash content of the pellets ranged from 8.05 ± 0.57% to 14.21 ± 0.05%. The ST temperature of the experimentally measured mixture of faba bean waste and potato peel pellets ranged from 924 to 969 °C; the DT temperature ranged from 944 to 983 °C; the HT temperature ranged from 1073 to 1202 °C, and a change in FT temperature from 1174 to 1234 °C was observed. The temperatures were sufficiently high to melt the ash. Specific emissions of CO₂, CO, NO_x and C_xH_y did not exceed the maximum levels allowed. In summary, from the results of the study of the physical properties, combustion, and emissions of waste beans and potato peel pellets (all samples), it is evident that they are used for biofuels. The combustion process of this type of pellet is characterized by efficient combustion and minimal emissions to the atmosphere.