Carbon-neutral fuel the carbon dioxide in flue gas emissions from power plants would eliminate their greenhouse gas emissions, although burning the fuel in vehicles would release that carbon because there is no economical way to capture those emissions. This approach would reduce net carbon dioxide emission by about 50% if it were used on all fossil fuel power plants. Most coal and natural gas power plants have been predicted to be economically retrofittable with carbon dioxide scrubbers for carbon capture to recycle flue exhaust or for carbon sequestration. Such recycling is expected to not only cost less than the excess economic impacts
Fuel gas. Biofuel can be broadly defined as solid, liquid, or gas fuel consisting of, or derived from biomass. Biomass can also be used directly for heating or power—known as "biomass fuel". Biofuel can be produced from any carbon source that can be replenished rapidly e.g. plants. Many different plants and plant-derived materials are used for biofuel manufacture. Perhaps the earliest fuel employed by humans is wood. Evidence shows controlled fire was used up to 1.5 million years ago at Swartkrans, South Africa. It is unknown which hominid species first used fire, as both "Australopithecus" and an early species of "Homo"