Od kave do biodizela: primjena ekološki prihvatljivih otapala

Biodizel je smjesa alkilnih estera masnih kiselina i najčešće se proizvodi iz jestivih biljnih ulja ili životinjskih masti. Smatra se čistom, biorazgradivom i netoksičnom alternativom za dizelsko gorivo. Da bi njegova proizvodnja i upotreba bila održivi, potrebno ga je sintetizirati iz nejestivih otpadnih sirovina. Time se smanjuje problem odlaganja otpada i izbjegavaju etički konflikti povezani s korištenjem prehrambenih namirnica u svrhu proizvodnje energenata. Obzirom na veliku globalnu proizvodnju i potrošnju kave, njezin otpadni talog smatra se potencijalnom sirovinom za proizvodnju biodizela zbog visokog udjela ulja te velike dostupnosti u cijelom svijetu. Tema ovog rada je sinteza biodizela iz otpadnog taloga kave. Ulje koje je sirovina za proizvodnju biodizela, dobiveno je procesom ekstrakcije iz kave Soxhlet metodom te ga je bilo potrebno pročistiti kapljevinskom ekstrakcijom s niskotemperaturnim eutektičkim otapalom kako bi se smanjio udio slobodnih masnih kiselina u samom ulju. Biodizel je proizveden iz ekstrahiranog ulja procesom transesterifikacije uz lužnati katalizator. Dobiveni biodizel pročišćen je kapljevinskom ekstrakcijom kojom je uklonjen sav zaostali glicerol u biodizelu. Tijekom rada istražen je utjecaj reakcijskih uvjeta na učinkovitost procesa te mogućnost primjene ekološki prihvatljivih otapala u procesu proizvodnje biodizela. Dobiveni biodizel namješan je s dizelskim gorivom te je odrađena fizikalno-kemijska karakterizacija uzorka. Biodiesel is a mixture of fatty acid alkyl esters and is most commonly produced from edible vegetable oils or animal fats. It is considered a clean, biodegradable and non-toxic alternative to diesel fuel. For its production and use to be sustainable, it needs to be synthesized from inedible waste feedstocks. This reduces the problem of waste disposal and avoids ethical conflicts associated with the use of food for energy purposes. Considering the large global production and consumption of coffee, its waste residue is considered a potential raw material for the production of biodiesel due to its high oil content and high availability worldwide. The topic of this paper is the production of biodiesel from waste coffee grounds. Oil was obtained from waste coffee grounds using the Soxhlet extraction method. It was purified by liquid-liquid extraction with a deep eutectic solvent in order to reduce the amount of free fatty acids in the oil itself. Biodiesel was produced from the extracted oil via the transesterification process with an alkaline catalyst. Crude biodiesel was then purified by liquid-liquid extraction, which removed all residual glycerol in the biodiesel. This paper explored the influence of reaction conditions on the process efficiency and the applicability of deep eutectic solvents in the process of biodiesel production from waste coffee grounds. Produced biodiesel was mixed with diesel fuel and the obtained mixture was physically and chemically characterized.