| Sažetak | Fosilna goriva trenutačno zadovoljavaju glavninu energetskih potreba u svijetu. Međutim, sukladno ciljevima modernog društva da postane nisko-ugljično i ekološki prihvatljivo „zeleno gospodarstvo“ definira obnovljive izvore energije kao važan segment za ostvarivanje navedenih ciljeva. Pod klasifikacijom obnovljivih izvora energije, ubraja se i poljoprivredna biomasa, a samim time i biomasa dobivena uzgojem višegodišnjih energetskih kultura poljoprivrednog podrijetla. Divlje proso (Panicum virgatum L.), kao energetsku kulturu, definiraju niska ulaganja u agrotehniku, visoka otpornost na bolesti i štetočine, kao i potencijalno visoki prinosi. Biomasa divljeg prosa može se konvertirati u različite oblike energije, odnosno biogoriva, a jedan od načina pretvorbe je i proizvodnja energije putem termokemijskih procesa pretvorbe. Cilj ovog rada bio je utvrditi energetske karakteristike (gorive i negorive tvari, ogrjevne vrijednosti, mikro i makro elemente) biomase trave divljeg prosa s obzirom na različite rokove žetve (jesenski i proljetni). U odnosu na istraživane rokove žetve utvrđena je signifikantna razlika u udjelima vode, pepela, dušika, ugljika, sumpora i kisika. Nasuprot, signifikantne razlike nisu utvrđena u udjelima vodika, koksa, fiksiranog ugljika i hlapivih tvari kao ni kod ogrjevnih vrijednosti. Rokovi žetve najviše su imali utjecaja na istraživane udjele mikro i makro elemenata jer su kod svih utvrđene signifikantne razlike. Prosječne vrijednosti udjela vode, pepela i donje ogrjevne vrijednosti, kao jednih od važnijih istraživanih parametara, u prvom i drugom roku bile su 33,88% i 10,95% za vodu, 4,59% i 3,71% za pepeo te 17,29 MJ kg-1 i 17,42 MJ kg-1 za donju ogrjevnu vrijednost. Podatci dobiveni ovim istraživanjem definiraju biomasu divljeg prosa, uzgojenu u istraživanim agroekološkim uvjetima Hrvatske, sirovinom zadovoljavajućih energetskih karakteristika. Odgađanje roka žetve od jeseni do proljeća rezultiralo je postizanjem kvalitetnije biomase, kao ulazne sirovine u procesu neposrednog izgaranja. |
| Sažetak (engleski) | Fossil fuels currently meet most of the energy needs in the world. However, according to the goals of modern society to become low-carbon and environmentally-friendly "green economy" defines renewable energy sources as an important segment for achieving the stated goals. Under the classification of renewable energy sources, agricultural biomass is also included, and thus the biomass obtained from the cultivation of perennial energy crops of agricultural origin. Switchgrass (Panicum virgatum L), as an energy crop, is defined by low investment in agricultural technology, high resistance to disease and pests, as well as potentially high yields. Switchgrass biomass can be converted into different forms of energy or biofuels, and one of the ways of conversion is energy production through thermochemical conversion processes. The aim of this study was to determine the energetic characteristics of switchgrass biomass in relation to two different harvesting periods (autumn and spring). Significant differences in the proportions of water, ash, nitrogen, carbon, sulfur and oxygen were found in relation to the research periods of harvest. In contrast, no significant differences were found in the proportions of hydrogen, coke, fixed carbon, and volatile matter as well as in the heating values. Harvest periods had the greatest impact on the research of micro and macro elements, since significant differences were found in all of them. The average values of water, ash and lower heating values as one of the most important researched parameters in autumn and spring harvest were 33,88% and 10,95% for water, 4,59% and 3,71% for ash and 17,29 mg kg-1 and 17,42 mg kg-1 for the lower heating value. The data obtained from this research define the biomass of switchgrass, grown in the investigated agro-ecological conditions of Croatia, as the raw material of satisfactory energy characteristics. Delaying the harvest period from autumn to spring has resulted in the achievement of higher quality biomass as input material in the direct combustion process. |
