Application of sewage sludge from wastewater treatmant plant in cultivation of energy crop Virginia Mallow

Porastom svjetske populacije posljedično je povećana potrošnja globalne energije zbog čega se sve više teži korištenju obnovljivih izvora energije. Biomasa kao jedna od glavnih obnovljivih izvora uključuje biomasu energetskih kultura te mulj nastao pročišćavanjem otpadnih voda. Biomasa energetskih kultura, poput virdžinijskog sljeza (Sida hermaphrodita L.), izdvaja se mogućnošću uzgoja na tlima lošije kvalitete uz visok prinos suhe tvari, dok mulj nastao pročišćavanjem otpadnih voda predstavlja gnojivo koje se može koristiti pri uzgoju energetskih kultura bez rizika prodora štetnih tvari u okoliš. Pravilnicima o primjeni mulja iz pročistača otpadnih voda određena je količina otpadnog mulja koja se smije koristiti na jednom hektaru poljoprivrednog zemljišta od 1,66 t/ha suhe tvari. Cilj rada bio je istražiti utjecaj aplikacije različitih količina otpadnog mulja na energetska svojstva virdžinijskog sljeza. Utvrdilo se da primjena većih količina otpadnog mulja od količine propisane Pravilnikom (1,66 t/ha) ne utječe negativno na energetska svojstva virdžinijskog sljeza. Primjenom većih količina otpadnog mulja rješava se problem zbrinjavanja istog te se omogućuje proizvodnja obnovljivog izvora energije.The increase in the world's population has consequently increased the consumption of global energy, which is why there is an increasing tendency to use renewable energy sources. Biomass, as one of the main renewable sources, includes biomass of energy crops and sewage sludge created by wastewater treatment plant. The biomass of energy crops, such as Virginia mallow (Sida hermaphrodita L.), is distinguished by the possibility of cultivation on soils of poorer quality with a high yield of dry matter, while the sewage sludge represents fertilizer for the cultivation of energy crops without the risk of harmful substances affecting the environment. Croatian regulations on the application of sewage sludge set the amount of sewage sludge that may be used on one hectare of agricultural land at 1.66 t/ha of dry matter. The aim of the study was to investigate whether the application of different quantities of sewage sludge affects the energy properties of Virginia mallow. It was found that the application of larger amounts of sewage sludge than the amount allowed by the Regulation (1.66 t/ha) does not have a negative effect on the energy properties of the Virginian mallow. By applying larger amounts of sewage sludge, the problem of its disposal is solved and the production of a renewable energy source is enabled