Bioethanol fuel obtained from biomass and bioenergy crops has been proclaimed as one of the feasible alternative to gasoline fuel, as it is considered to be clean, renewable and green. In this review, the bioethanol production techniques from different lignocellulosic biomass, and its potential ethanol yield are studied. Moreover, this paper has reviewed the effects of bioethanol fuel blends on spark ignition engine combustion characteristics (i.e. cylinder pressure, cylinder temperature, flame speed, combustion efficiency, combustion duration, heat release rate, knocking and cold start); engine performance parameters (i.e. torque, brake power, brake specific fuel consumption, brake mean effective pressure, brake thermal efficiency and volumetric efficiency); and emission characteristics (i.e. carbon monoxide, oxides of nitrogen, carbon dioxide, unburned hydrocarbon and other unregulated emissions). Recently, many researchers produced bioethanol from herbaceous, industrial and municipal solid wastes (MSW) instead of agriculture and woody biomass. Most of the engine test results showed a remarkable improvement in engine performance and enhanced combustion characteristics for bioethanol fuel. In addition, the carbon monoxide and unburned hydrocarbon emissions decreased. Conversely, carbon dioxide and oxides of nitrogen emissions were not significantly reduced. Furthermore, there was no significant reduction of unregulated emissions, such as aromatics, acetaldehyde, and carbonyls.

h i g h l i g h t sMicrowave hydrothermal hydrolysis with CO 2 was carried out for SPW. Batch fermentation and distillation was carried out. GC and FTIR confirmation of distilled ethanol was done. Maximum of 43.8% glucose and 15.6 g ethanol per 100 g SPW was obtained. Lower energy consumption was observed for combined pretreatment and hydrolysis. a r t i c l e i n f o t r a c tBioethanol production from sago pith waste (SPW) using microwave hydrothermal hydrolysis accelerated by carbon dioxide was studied. The structural change in the SPW after hydrolysis, ethanol purity after fermentation, and distillation were investigated. Energy consumption for microwave hydrothermal hydrolysis was evaluated. A maximum of 43.8% theoretical glucose and 40.5% theoretical ethanol yield were obtained. The ethanol yield coefficient obtained in fermentation was 0.47 (g ethanol per g glucose) which was 15.6 g ethanol per 100 g dry SPW. It was also discovered that the lowest energy consumption occurred when energy input was fixed at 108 kJ (900 W for 2 min), amounting to 33 kJ and 69 kJ to produce one gram glucose after hydrothermal hydrolysis and one gram ethanol after fermentation, respectively. The developed technique for SPW resulted in higher energy saving compared to previous techniques in the absence of enzymes, acid or base catalyst.

a b s t r a c tCorrosive behavior of biodieseledieseleethanol (BDE) fuel blends upon exposure to metals, namely, mild steel, copper and aluminum was studied by static immersion at room temperature and 60 C. The change of fuel properties, i.e., total acid number, density, viscosity, calorific value, flash point, and color changes were investigated. Moreover, fuel compositional changes, such as water content, oxidation product level, and metal elements in the fuel blends were examined. Finally, the effect of fuel blends on corrosion rate (CR), morphology of corrosion products, and chemical structure of metals were studied. Results revealed that the CR of metals in BDE fuels is in the order: aluminum < mild steel < copper at both temperature conditions. The degradation of fuel properties and corrosion rate of metals in BDE fuel blends are lower than neat biodiesel (B100), whereas higher than petroediesel (B0). Corrosiveness of B20D75E5 is lower than B20D70E10 upon exposure to metals.