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Between 1906 and 2005, records show that global average air temperature near the earth's surface increased by 0.74 ± 0.18°C. If emissions of greenhouse gases, and in particular CO 2 , continue unabated the enhanced greenhouse effect may alter the world's climate system irreversibly. Total emissions of greenhouse gases, across all sectors, were 42.4 gigatonnes (Gt) of CO 2 -eq in 2005. Energy sector, accounts for 84% of global CO 2 emissions and 64% of the world's greenhouse-gas emissions. Energy-related CO 2 emissions rise from 28.8 Gt in 2007 to 34.5 Gt in 2020 and 40.2 Gt in 2030. Global percapita emissions of energy-related CO 2 in 2007 was 4.4 tonnes. Higher growth of automobiles and consumption of petroleum products is invariably attended by concerns of pollution and climate changes. Global fleet of passenger light-duty vehicles (PLDVs) is estimated to increase from 770 million in 2007 to 1.4 billion in 2030. Among all sectors that emit CO 2 , the transport sector is the fastest growing, representing from 22% to 24% of global GHG emissions from fossil fuel sources, second only to the industrial sector. World emissions of NOx were 82 Mt in 2007, of which Road transport was responsible for about one-third of NOx emissions. Only Road transport related CO 2 emission is estimated to increase from 4.8 Gt in 2007 to 6.9 Gt in 2030. The increase in CO 2 emissions is largely a result of increasing demand for individual mobility in developing countries. There are strong efforts and renewed investments by manufacturers and suppliers in providing solutions to the CO 2 reduction challenge. Low-carbon vehicles, such as hybrid cars, plug-in hybrids and electric cars, have received widespread public attention recently. It is estimated that share of hybrids in the global fleet will reach about 5% by 2020 and almost 8% by 2030, up from just 0.15% in 2007. Plug-in hybrids and electric cars will constitute only 0.2% of the global fleet in 2030. But increase in electricity consumption in road transport in future due to increased penetration of plug-in hybrids and electric vehicles, sees transport sector CO 2 savings partially offset by power generation emissions. An estimated increase of 880 TWh of

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Due to gradual depletion of world petroleum reserves and the impact of environmental pollution of increasing exhaust emissions, there is an urgent need for suitable alternative fuels for use in engines. The heightened awareness of green house gas emissions and global warming compels introduction of more stringent environmental regulations worldwide. Renewable biofuels are considered potential solution for these problems. But use of biofuel is creating tribology related new challenges world over. In this paper a critical analysis of tribology related issue of three main biofuels, namely Straight Vegetable Oil (SVO), biodiesel and alcohols are discussed. Many issues like lubricity of blends, carbon deposit, viscosity, corrosion of engine components, etc are discussed in detail. Quality control of biofuels, identified as a key factor for sustainable market growth of these fuels and can lead to many tribological issues. In this regard a dire need for global harmonized standards is also discussed. Different solutions for alcohol fuel related engine problems are discussed. Critical discussion in relation to the problems due to the use of SVO in engine, like engine performance decrease, injector choking, oil ring sticking, etc took place in this paper. Potential solutions to these problems found by academia as well as industry are discussed here.

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