Influence of fertilizers on chemical content in grass biomass.

Abstract

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.

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“…The main combustible elemental component of biomass is C and this is followed by H, which has more calorific value than C, though [ 16 , 47 ]. N does not support combustion; O reduces the energy content of biomass while S and N are associated with formation of SO x and NO x during combustion [ 16 , 48 , 49 ].…”

“…N does not support combustion; O reduces the energy content of biomass while S and N are associated with formation of SO x and NO x during combustion [ 16 , 48 , 49 ]. Increase in the energy indices of C and H lowers the calorific potential of O [ 47 ], and such lowering causes increase in calorific value of biomass [ 50 ]. Energy content of solid fuel is therefore generally related to the atomic hydrogen to carbon (H:C) and the atomic oxygen to carbon (O:C) ratios, with high H:C ratio corresponding to high energy content and high O:C ratio meaning low energy content.…”