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This paper presents the results of research on the preparation and use for energy purposes of three reed herbaceous energy plants: reed (Phragmites australis) and bulrush (Typha); both grown in local vicinities on lakes and riverbanks and reed canary grass (Phalaris arundinacea L.). The physical-mechanical characteristics (density, moisture, and ash content) of chopped and milled reeds were investigated. The investigation of mill fractional compositions determined the largest amount of mill—reed mill, collected on the sieves of 0.63 mm (40.0%). The pellet moisture ranged from 10.79% to 6.32%, while the density was 1178.9 kg m−3 for dry matter (DM) of reed. The ash content of reed, bulrush and reed canary grass pellets was 3.17%, 5.88%, and 7.99%, respectively. The ash melting temperature ranged from 865 to 1411 °C; these temperatures were high enough for ash melting. The determined pellet calorific value varied from 17.4 to 17.9 MJ kg−1 DM. The disintegration force, indicating pellet strength, ranged from 324.25 N for reed canary grass to 549.24 N for reed. The determined emissions of harmful pollutants—CO2, CO, NOx, and unburnt hydrocarbons (CxHy)—did not exceed the maximum permissible levels. The assessment of greenhouse gas emissions (GHG) from technology showed that the CO2 equivalents ranged from 7.3 to 10.1 kg CO2-eq. GJ−1 for reed and reed canary grass, respectively.

Three unconventional herbaceous energy plants -sida (Sida hermaphrodita Rusby), elephant grass (Miscanthus giganteus) and reed canary grass (Phalaris arundinacea) -were grown and investigated in the experimental fields of Aleksandras Stulginskis University, and the technical means of plant preparation and usage for energy purposes were investigated. The physical-mechanical characteristics (moisture content, density, flow angles) of chopped and milled unconventional energy plants were investigated. These characteristics are required to project and choose the supply, transportation and storage equipment. In evaluating the quality of plant chopping and milling, the fractional compositions of reed canary grass, sida and elephant grass chaff as well as the mill were determined. The largest chaff fraction was found in a sieve with 8-mm diameter holes (from 52.0 to 62.7%), and the largest mill fraction was found in a sieve with 0.5-and 0.63-mm diameter holes (from 37.6 to 46.4%). The pellet moisture content was sufficiently low and varied from 6.7% to 9.6%. The highest density was determined in reed canary grass pellets (1035.1±63.9 kg m -3 DM), and the lowest density was in elephant grass pellets (653.6±67.1 kg m -3 DM). The emission of harmful gases was determined when various unconventional energy plants were burned. The highest concentration of carbon monoxide (CO) was observed when burning elephant grass (2294.7 ppm), and the smallest concentration of CO was observed when burning reed canary grass (905.2 ppm). The most carbon dioxide was detected when burning sida (7.9%), and the smallest when burning elephant grass (5.2%). The nitrogen oxide emissions differed only insignificantly; the values ranged from 176.2 ppm (Reed canary grass) to 216.1 ppm (Elephant grass). a prime cost of 0.12 EUR/kg. When energetic grasses were dried using dispergation, the primary cost increases to 0.13 EUR/kg.

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.

Giant knotweed (Fallopia sachalinensis) was chosen as a perspective energy plant because it is not a soil demanding plant and belongs to the most efficient herbs in Central Europe as regards high biomass yield. Miscanthus (Miscanthus sinensis) was chosen as a control one. Knotweeds are comparable to wood briquettes and pellets because of their similarparallel mechanical and thermal features. These plants grow in forest environment with an approximate yield productivity of 15 t ha-1 d.b. (dry basis). Experimental research investigations were performed in the laboratories of Aleksandras Stulginskis University. Giant knotweed and miscanthus biomass was cut, chopped, milled and granulated with a small capacity granulator (250–300 kg h-1). Quality parameters of plant preparative and use for energetical objectives were determined. Plant chaff and mill fraction compositions were determined, and quality indicators of the produced pellets were measured – moisture content, density, resistance to compression, elemental composition, ash content and calorific value, also bulk density, fall and natural slope angles. Moisture content reached 7.8 ± 0.8 %; pellet density was 1227.3 ± 48.6 kg m-3. Resistance to compression of giant knotweed pellet was 850 N. Determined ash content was 4.3 ± 0.01 %, and net calorific value of knotweed dry mass was of sufficient height and reached 18.96 ± 0.28 MJ kg-1. Bulk density reached 509.9 kg m-3, natural slope angle was 31.7 0 and fall angle was 49.3 0.