Municipal Sewage Sludge to Biodiesel as a Promising Renewable Fuel for the Future of Energy

Due to the global energy crisis caused by the rapid urbanization and industrialization along with a steady increase in energy demand, non-renewable energy sources are becoming increasingly scarce, and petroleum prices are rising. It is expected that the consumption of liquid fuels in the world increases from 87 million barrels per day in 2010 to 122 million barrels per day in 2040 1. On the other hand, the environmental considerations of fossil fuels such as air pollutants and excessive emission of greenhouse gases has increased concerns on environmental pollution. Utilizing clean renewable fuel is one convenient way to overcome both problems simultaneously.In recent years, biodiesel as a renewable and environmentally friendly energy has been introduced to replace conventional fossil fuels. Biodiesel is biodegradable and non-toxic which compared to diesel has three technical (more fluidity, decrease the sediment in the fuel tank), environmental (absence of sulfur and aromatic compounds, fewer emissions of hydrocarbons, CO, particulate matter) and economical (more energy intensity, fuel import costs) advantages. Over the past decade, biodiesel production in the United States increased from 700 to 2,890 million gallons per year