In the handling and usage processes, sufficient density and durability of biomass (straw, read) briquettes should be provided. For the briquettes density standards determined the value ρ > 1.0 g cm-3. In ? the densification process usually fine grinded particles are used, what significantly increases energy consumption for stalk material cutting. Calculated energy consumption for common reed cutting to sizes less than 3 mm was > 7 kJ kg-1 but for size 20 mm it was approximately 1 kJ kg-1. The goal of the investigation was to obtain the necessary density and durability of briquettes of larger biomass particles by arranging them. The orientation of straw or reed stalks had to promote binding by the pressing operation. The long stalk linking, in the picture of coloured stalk briquettes sections, is good visible. Crushing force dependence on particle size for arranged structure briquettes is stated in laboratory experiments. The specific splitting force of arranged structure coarse chopped wheat straw and reed briquettes reaches value 35 N mm-1. It is approximately the same as industrially produced wood briquettes. Splitting force of the hemp stalk briquettes reaches 115 N·mm-1.

Carbon and hydrogen are the main burning elements of biomass fuel that affect the calorific value of fuel. Combustion heat of hydrogen significantly exceeds the heat of carbon combustion, so biomass with higher hydrogen content has a relatively higher calorific value. The study found that the carbon content of various grass species (reed canary grass, festulolium, timothy, meadow fescue, and tall fescue) varied from 42.00 % formeadow fescue to48.97 % fortimothy. Hydrogen content in the samples analysed was, however, between 5.48 % (for timothy) and 5.93 % (for reed canary grass). The hydrogen-to-carbon (H/C) ratio for grasses variedfrom 1.45 for timothy to 1.52 for reed canary grass. The calculation of the H/C ratio for grass biomass as well as the effect of the nitrogen fertilizer dose on the hydrogen and carbon content of biomass are described in the present article. A conclusion is drawn that the calorific value of biomass fuel is significantly affected by the carbon content. In contrast, the increased lignin content against cellulose and hemicellulose increases the calorific value of the fuel at the same carbon content. The increase in hydrogen-carbon ratio reduces the gross calorific value.

The main resources for biomass agro-ecotechnologies are cereal straw residues, energy crops and emergent vegetation from wetlands. The herbaceous biomass is a material of low density (20 – 60kg/m3) therefore new mobile equipment and technologies for biomass comminution and densification have to be worked out. To guarantee the quality of biomass briquettes in the handling and usage process, sufficient durability of briquettes should be provided. National Standards of biomass briquettes should be worked out in accordance with the requirements of International Standards. Dependence of Ultimate shear stress on wheat stalk material particle size in biomass briquettes was investigated. It was stated that ultimate shear stress increases for particle size in briquettes less than 0.5mm. Peat additive improves the density and ultimate shear strength of briquettes, but peat in combustion process increases the ash content. Therefore it is not necessary to add peat more than 50% in briquetting composition. Durability of reed stalk briquettes ~1.7 times exceeds durability of wheat stalk briquettes. Maximal values of ultimate shear stress (1,5 MPa) and density (1,2 g/cm3) for pure peat (100%) briquettes was obtained.

In practice for material pressing mechanisms are used that provide synchronous motion of components. Gears can satisfy this design specification accurately, but they are more expensive and difficult to manufacture than linkages, and not convenient to transmit the motion between two parallel axis with large center distance. Thus, when a quasi-constant transmission ratio within a wide range of driving link rotation is allowed, four-bar linkages are suitable to replace gears. The possibility of using a four-bar linkage mechanism to ensure opposite rotation of double cranks is analysed. A planar four-bar linkage is characterized by having four revolute joints with parallel axis. The synthesis of four-bar linkages will yield an approximation of transmission ratio between the input and output crank rotation. Crank displacement equations for antiparallelogram and similar forbar linkage mechanisms depending on the sizes of the links are presented. Antiparallelogram mechanism with ratios j = 30 between the center-distance and the crank length provide a transmission ratio u 13 = 1 ± 5 % for driving the crank angle in range 40-140 deg. The Matlab simulation showed quasi-constant transmission ratio u = 1 ± 2 % for the four-bar mechanisms with coupler length not equal with fixed center distance.

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