[Dr. Scott W. Tinker] Birds build houses, monkeys make tools, and ants grow agriculture. You could argue that what separates us from other animals is that we have harnessed energy, starting many thousands of years ago with fire. Burning biomass like wood, straw, or animal dung allowed humans to walk off the savanna, through the Ice Age, and into the modern era. Our relationship with fire is so important that many scientists believe humans could not have evolved without it. Even today, 1/10 of global energy comes from burning biomass. For 2.8 billion people, that's almost 40% of global population, biomass still provides heat and cooking. Without it, they could freeze or starve. Biomass essentially provides them life, but it also produces huge volumes of CO2. Wood is one of the few energy sources that emits more carbon than coal and it can be deadly. Inhaling the smoke of a wood fire in a closed hut for an hour is the equivalent of smoking 400 cigarettes. This this makes biomass our most deadly energy source, killing 2 million people per year, another example of a challenging energy trade-off. The rural poor of Latin America, Africa, India, and Asia need stoves that burn biomass more cleanly and efficiently and they need cleaner cooking fuels. The gradual development of these regions are helping them get there, but it will take time. There are other, cleaner ways to use biomass. In many parts of the world, crop waste is burned to generate power. If the crops are re-planted, then the CO2 emissions are offset by the new crop, making it carbon neutral. This works especially well if the crop or lumber waste can power industrial processes right where it's grown, like in Brazil's cane fields. These processes burn far less biomass than heating and cooking in the developing world, but they're growing. And as other energy sources become more expensive, we'll see more creative and cleaner ways of using our oldest energy source.