Processes of bioethanol production currently applied all over the world are reviewed in this paper. Attention is focused on potentially cheap biomass sources, as well as the most important operating factors controlling the progress and result of saccharification and fermentation reactions and affecting the yield of fermentable sugars and ethanol, respectively, such as: the type and concentration of acid, the type of enzyme, the type of working microorganism, operating temperature, duration time and pH. The hydrolysis conditions, namely duration time, temperature and sulfuric acid concentration, were combined in a single parameter, known as the "combined severity" (CS), in order to estimate the efficiency of bioethanol production from biomass. When the CS increases, the yield of fermentable sugars also increases. The decrease in the yield of monosaccharides coincides with the maximum concentrations of by-products, such as furfural and 5-hydroxymethylfurfural, which are well-known as yeast inhibitors. The highest ethanol yields has been obtained using the yeast Saccharomyces cerevisiae. With low oil prices and political reluctance to implement carbon taxes, fuel-ethanol production will remain uncompetitive unless some other form of cost reduction can be made, such as feedstock preparation costs

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The cultivation of non-edible oil-bearing plants as feedstocks for the biodiesel production can aggressively take advantage of natural environments. Herbaceous non-edible oil-bearing plants have been significantly favored as an ideal feedstock for biodiesel fuel, though little is known about its industrial feasibility and environmental impact. The items with the greatest sensitivity in capital and ecology are land acquisition, plant life cycle, mechanical harvesting, fertilizer, control of weed, pests and diseases, seed yield and oil content. This study aims at analyzing the disadvantages of herbaceous non-edible oil-bearing plants and suggests impeding their industrial cultivation for the biodiesel production. The source of information for the proper selection of non-edible oil-bearing plants suitable as biodiesel feed-stocks has been the recent relevant literature. Herbaceous non-edible oil-bearing plants have a low phytoremediation potential and oil yield, but high weed potential. They occupy a large arable area while demand harder cultivation conditions and mechanical harvesting. Non-edible oils from woody plants are promising biodiesel feedstock. However, the weed potential of woody oil-bearing plants must also be considered to prevent their invasiveness.