Abstract. Carbon (C), hydrogen (H), and oxygen (O) are the main chemical elements that determine the heating value of fuels. By combustion of biomass, C and H oxidize in an exothermic reaction. The carbon content in biomass is considerably higher (~45 %) than the hydrogen content (~6.5 %). In contrast, the heating value of H is approximately seven times higher than that of C. The more hydrogen per carbon, the lower the oxidation state and the more energy that will be released during the oxidation reaction, which is characterized by C/H ratio. In our study, the highest carbon content was detected in the mixtures (1/3) of tall fescue with osier (46.6 %) and reed canary grass with grey alder (46.9 %), whereas the lowest values were detected in the mixtures (3/1) of tall fescue with hybrid aspen (43.7 %) and reed canary grass with osier (43.4 %). The highest hydrogen content was found in timothy (5.93 %) and birch (6.83 %). In grass biomass, H content was on average 6 % lower than in wood biomass.
Abstract:In the production of granules from plants the cohesive substance lignin has a great importance, as it holds the granule together and does not allow it to disintegrate. The objective of this research was to evaluate the influencing factors of lignin content in reed canarygrass (Phalaris arundinacea L.) crop yield. In this research the varieties of reed canarygrass 'Marathon' and 'Bamse' were analysed for yields of first and second year. The lignin content of the samples was established by Classon's method. Arsenic (As), Cadmium (Cd), and Lead (Pb) and other chemical elements were established in the reed canarygrass samples with the spectrometer Optima 2100DV. The reed canarygrass second year crop yield was 3-4 times greater than the first year crop yield. A significantly correlation (p<0.05) was established in the first crop yield October samples between lignin and natrium (Na). Some correlation relationships are contradictory, which confirms that within the plant growth period the meteorological conditions are of great importance. Analysing the determining factors of lignin content it can be seen that they were influenced by the interaction of various factors -the sowing and growing period, the variety and the N-fertilizer rate application.
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.
Abstract. Perennial grasses are a good option for biofuels because they do not have to be planted annually and do not require application of agricultural chemicals. Since the crop value for bioenergy use is the carbohydrates, not the protein, the grasses can be harvested after they have died back in the fall, i.e., after the nitrogen and other nutrients have been translocated back into the roots and crowns. So late harvesting means that the nutrients remain in the perennial parts of the plants, which, in turn, means that the crop does not need high levels of fertilization each year. The chemical composition of grasses is very dynamic, and it changes significantly during the vegetation period. When using grass biomass for solid fuels, the chemical composition of grasses is of major importance, as alkali metals affect the ash melting temperature. One of the key parameters is nitrogen content in fuel, which affects the formation of NOx emissions. The aim of the research was to assess the effect of nitrogen fertiliser norms on the chemical composition of grass biomass. The research objects were reed canary grass (RCG) (Phalaris arundinacea L.), tall fescue (Festuca arundinacea Schreb.), and timothy (Phleum pratense L.) -the perennial and productive plants of the grass family. Increasing the fertiliser norms from N0 to N90, the content of non-combustible element N in the biomass of all grasses also increased. However, nitrogen fertiliser has little yet significant impact on the content of combustible element C in grass biomass.
For solid fuels ash melting temperature is recommended to be higher than 1000°C, so that it can be used in automated furnaces; therefore-promising energy crops are investigated as renewable energy source. This paper presents the results of tests on melting temperature of different energy crop ashes.The field trial was carried out in the study farm of the Latvia University of Agriculture "Pēterlauki" (56°53'N, 23°71'E) in the sod calcareous soils characterized by pH KCl 6.7, P 52 mg kg-1, K 128 mg kg-1, organic matter content from 21 to 25 g kg-1 in the soil. Energy crops analysed: reed canary grass (Phalaris arundinacea L.), birch (Betula pendula Roth.), osier (Salix spp.), grey alder (Alnus incana (L.) Moench), poplar (Populus tremula L.), hybrid aspen (Populus tremuloides x Populus tremula). Results indicate that the ash melting temperature (D, St, Ht, Ft) for the wood energy crops were higher than for the studied grass energy crops and their mixture. Ash melting temperature in all phases over 1200°C was observed for such poplar and hybrid aspen mixture proportions: 3 parts of wood and 1 part of reed canary grass, or 1 part of wood and 1 part of reed canary grass.
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