Bioethanol Production from Renewable Raw Materials and Its Separation and Purification: A Review

Proizvodnja biogoriva iz obnovljivih sirovina privukla je pažnju znanstvenika jer može poslužiti za opskrbu energijom i alternativnim gorivima. Bioetanol je jedno od najzanimljivijih biogoriva zbog njegovog pozitivnog utjecaja na okoliš. Najčešće se proizvodi iz sirovina koje sadržavaju šećer i škrob. Međutim, razni izvori lignocelulozne biomase, kao što su poljoprivredni i šumski ostaci te zeljasti energetski usjevi, također mogu poslužiti kao sirovine za proizvodnju bioetanola, energije, topline i kemikalija s dodanom vrijednošću. Lignoceluloza je složena mješavina ugljikohidrata, koju treba učinkovito prethodno obraditi da bi se oslobodili biotransformacijski putevi u kojima enzimi proizvode fermentabilne šećere što nakon hidrolize fermentiraju u etanol. Unatoč tehničkim i ekonomskim poteškoćama, obnovljive lignocelulozne sirovine imaju nisku cijenu te ne utječu na hranu i prehrambeni lanac, čime potiču održivost. Za proizvodnju bioetanola iz obnovljivih sirovina razvijeni su različiti načini rada bioprocesora. Osim toga, intenzivno se razvijaju i alternativni postupci odvajanja i pročišćavanja bioetanola. Ovaj rad daje pregled novih trendova u proizvodnji bioetanola iz različitih obnovljivih sirovina, te postupaka njegovog odvajanja i pročišćavanja.
Production of biofuels from renewable feedstocks has captured considerable scientific attention since they could be used to supply energy and alternative fuels. Bioethanol is one of the most interesting biofuels due to its positive impact on the environment. Currently, it is mostly produced from sugar- and starch-containing raw materials. However, various available types of lignocellulosic biomass such as agricultural and forestry residues, and herbaceous energy crops could serve as feedstocks for the production of bioethanol, energy, heat and value-added chemicals. Lignocellulose is a complex mixture of carbohydrates that needs an efficient pretreatment to make accessible pathways to enzymes for the production of fermentable sugars, which after hydrolysis are fermented into ethanol. Despite technical and economic difficulties, renewable lignocellulosic raw materials represent low-cost feedstocks that do not compete with the food and feed chain, thereby stimulating the sustainability. Different bioprocess operational modes were developed for bioethanol production from renewable raw materials. Furthermore, alternative bioethanol separation and purification processes have also been intensively developed. This paper deals with recent trends in the bioethanol production as a fuel from different renewable raw materials as well as with its separation and purification processes.