---

The production of bioethanol from lignocellulosic biomass could be considered as an appropriate and economic option to remove environmental disasters and improve energy security. In fact, lignocellulosic material is mainly composed of cellulose, hemicellulose and lignin. Lignin works as the adhering prevents the bioconversion of cellulose into sugars and ultimately to ethanol. To address the problem, various chemical, physical, physicochemical and biological methods have been suggested. Enjoying convenient operating conditions, production of non-hazardous wastes, and having no harmful side effects, make the biological methods a potentially proper option. Unfortunately, the biological methods are slower and less efficient in comparison with the other processes. In the present study, an attempt is made to resolve this problem in an enzymatic degradation of lignin of a rice straw sample. Several peroxidase enzymes were produced by a white rot fungus, and their effects on lignin removal from the biomass samples were investigated in shaking flasks. Lignin concentration and enzymes' activity were measured by the acetyl bromide-soluble lignin spectrophotometric method and optical density method using special reagents, respectively. The results revealed that the enzymatic treatment could remove at least 30% of the lignin content of the lignocellulosic biomass. To achieve the maximum activity of the enzymes, The chemical composition of the culturing medium was optimized for the concentration of important metal ions including Cu2+, Mn2+ and Zn2+ through Box Behnken response surface methodology. The enzymes' activity at the obtained optimal conditions increased four times for Manganese peroxidase, and lignin peroxidase.

---

Ethanol as a renewable biofule is an appropriate and viable alternative to the challenging fossil fuels. Bacillus subtilis, a gram positive bacterium, seems to be a promising choice since it has many useful features. For example B.subtilis ferments broad range of sugars derived from lignocellulosic hydrolysis. Transformation of this cellulytic bacterium to an ethanologenic one was accomplished via metabolic engineering techniques and Ethanol production operon of Z.mobilis was introduced to the B.subtilis. SR1 and SR21 strains expressed plasmid-borne ethanologenic genes of Z.mobilis but the genes had been integrated into the SR22 genomic DNA. Also lactate dehydrogenase gene had been knocked-out in SR21 and SR22 strains. Defect of cell growth in SR21 and SR22, suggests that NAD+ oxidation by lactate dehydrogenase is important for anaerobic growth. Considering the impact of Fe2+ ion on alcohol dehydrogenase II activity, in further experiments Fe2+ was added to the culture media and improvement in growth rates was seen. Final yield of ethanol production of SR1, SR21, and SR22 strains were 53.8%, 86.7%, and 83.9% respectively.

---

Biofuels are the main substitute to fossil fuels. These fuels are less polluting in compari-son to fossil fuels and can be produced from agricultural material residues for use in die-sel engines. In this research work bioethanol was produced from potato waste. It was de-hydrated in a vapor phase using 3A zeolite and was used in combination with sunflower methyl ester oil and diesel fuel blending which was evaluated thereafter. The sunflower methyl ester was also produced using a transesterification method. Considering the labo-ratory conditions and fuel stability limits to be used, the suitable blending proportion of bioethanol and diesel fuel was determined to be 12 to 88 and then, for maintaining fuel stability at temperatures lower than 15oC, the sunflower methyl ester was added to the mixture. The pour point of the fuel and different fuel blends, the viscosity, cetane number, flash point, amount of fuel ash, sulfur content and copper corrosion were determined in the laboratory. Experiments show that ethanol plays an important role on the flash point of the blends. With the addition of 3% bioethanol to diesel and sunflower methyl ester, the flash point was reduced to 16oC. The viscosity of the blends was reduced with the in-crease in the amount of ethanol. The sulfur content of bioethanol and sunflower methyl ester is very low compared with that of diesel fuel. The sulfur content of diesel is 500 ppm whereas that for ethanol and sunflower methyl ester is 0 and 15 ppm, respectively. The lower amount of sulfur content facilitates the use of fuel blends in diesel engines. For the ethanol and sunflower methyl ester combination, this amount is less than 20 ppm.

---

In the production of fuel briquettes, different additives are used in order to improve the technical parameters. In the present study, two types of lignocellulosic binders including nanocellulose and lignin have been used. Due to the different chemical structure and difference in calorific value of each of these two materials (lignin and nanocellulose) and the difference in their mechanism of action on improving the thermal properties of fuel briquettes, in order to evaluate the final product of thermal analysis using calorific value and TGA and DTA diagrams were used. The results show the positive effects of the use of cellulosic binders in improving the thermal behavior of biofuel briquettes. Thermal analysis showed that 9% nanocellulose and 9% lignin treatments with 19.85 MJ / Kg and 25.75 MJ / Kg had the highest calorific value compared to the control sample, respectively. The diagram obtained from thermal analysis (TGA) of the control sample and the samples treated with lignin and nanocellulose show that the treated samples have lower weight loss rate, higher burning rate and higher burning temperature.

---

 Microbial oil has high similarity to the oil obtained from plants and animals. They are renewable sources that can be used for different purposes such as production of biofuels. Biofuels are renewable, biodegradable, and nontoxic, which makes them highly environmentally friendly. Producing oil from yeasts has more advantages than that from plants. Accordingly, isolation of oleaginous yeasts with high ability of lipid production is highly valuable. A total of 138 yeasts were isolated for the purpose of this study. From this amount, 35 were capable of producing lipid. After extracting lipid, the best strain was selected and, by using PCR method, identified as Rhodotorula mucilaginosa. Optimization was done using the design of experiments; Qualitek-4 (W32b) software was used for analyzing the experimental data. According to the results, Rhodotorula mucilaginosa proved to comprise lipid, dry biomass, and lipid productivity at levels of 10.97 g L ^-1, 18.84 g L^-1, and 58.2% in optimized conditions, respectively. Lipid content on corn stalk and wheat straw hydrolysate was 36.9 and 41.8%, respectively. The extracted lipid was analyzed by FTIR spectroscopy and gas chromatography-mass spectrometry (GC-MS). The study showed high potential of lipid production in Rhodotorula mucilaginosa and also high efficiency of using Taguchi design in optimization of medium condition; therefore, by using this method, the optimization process can be done as best as possible. The economic values of microbial lipid production become more favorable when waste materials with zero or negative economic value are utilized as carbon source. Using bioprocesses such as microbial lipid production from waste materials, the problem of shortage of energy resources, and also air pollutions caused by fossil fuels, could be eliminated. 

---

In this study, a numerical investigation of using Rapeseed Oil in National Diesel Engine has been developed and validated against the experimental data. By using validated model, the effect of injection timing, exhaust gas recirculation and initial pressure on performance and emissions of this engine with three different range of using diesel and biodiesel fuels have been investigated. Biodiesel fuel has two significant characteristics, existing Oxygen Atom in its structure and low lower heating value comparing diesel fuel. The results show by increasing biodiesel fuel, better combustion process has been achieved and consequently, increasing in thermal efficiency and reducing carbon monoxide emission have been observed. Because of different characteristics of biodiesel fuel, increasing and decreasing in the amount of this fuel can effect differently on engine power and producing nitrogen oxide emission.

---

In many European countries, residues from agricultural products represent a considerable potential for development of bio-energy industry. A significant part of these biomass materials come from the fruit-growing business, i.e., primary fruit production and fruit processing plants. The EU directives require that the disposal of such residues should be environmentally sustainable. The objective of this study was to determine proximate (moisture content, ash, fixed carbon, volatile matter), ultimate (carbon, hydrogen, nitrogen and sulphur) and energy values (higher, lower) of biomass, as well as the Croatian total energy potential generated after the pruning (pruned residues) and processing of plum fruit (stone). Five different plum varieties (Bistrica, Cacanska ljepotica, Cacanska rodna, President, and Stanley), most commonly grown in the territory of Croatia, were analyzed and compared. The analyzed data were compared with the norm CEN/TS 14961 (2005) for solid biofuels and the data from the relevant literature. Both types of investigated biomass proved to be highly valuable sources of energy; and no significant difference between investigated plum varieties were found. Lower heating value, as one of the fundamental parameters of the biomass energy efficiency, averaged in the studied samples: 15.2 MJ kg^-1 for plum pits and 17.12 MJ kg^-1 for pruned biomass, which classifies plum biomass as a valuable energy raw material. Also, the calculations show that the potential production of the biomass available in Croatia could reach up to 292.13 MJ of renewable "green" energy annually.