When people think “sustainable energy,” the energy source that often springs to mind is, naturally, biomass. Humans have been using biomass for energy since the dawn of our time. Not only is it our personal source of energy (as in food), we have also used it to cook our food and heat our homes for millennia. As a potential energy source, biomass is relatively abundant (ranked third, after oil and coal) and has supplied more than 90% of the fuel and energy needs of the United States until the mid-nineteenth century (Champagne 2008). In several European countries, biomass makes a considerable contribution to energy supply and consumption and it is still a signicant source of energy in developing countries (Pereira et al. 2012). Among the various energy solutions presented in this book, biomass-to-energy conversions are arguably the most sustainable and are considerably cleaner than coal, for example, in that biomass-derived energy generates far fewer NOx or SOx emissions. Another advantage of the use of biomass is its amenability to small-scale installations with the concomitant promise of energy availability and economic development in rural and developing areas. Biomass led the way in renewable energy consumption in 2011 in the United States, with 4.4 quadrillion BTU being consumed (hydroelectric power was a distant second with 3.2 quad) (U.S. Energy Information Administration 2012). Given the availability of biomass, its very low levels of pollutants and the wide variety of conversion options for deriving usable energy from biomass, the contributions of biomass to our future energy needs are certain to grow.