Growing awareness of global citizenship and social responsibility, it is no surprise that "voluntourism" is booming. There are increasing concerns about global warming and the effects of carbon dioxide produced from flights, road trips, and other fossil-fuel based recreation. Air transportation alone is believed to produce between 4%-10% of greenhouse gases worldwide. A range of businesses are taking responsibility for reducing their "carbon footprint" by decreasing emissions and donating to tree planting, forest protection, and solar, wind and other renewable energy projects. The aim of this book is to present a core of this subject knowledge that is desirable for students. Every attempt has been made to keep abreast of the advances in the subject and at the same time to include the fundamentals.