is widely used in the United States and in Brazil. The energy costs for producing bio-ethanol are almost equal to, the energy yields from bio-ethanol. However, according to the European Environment Agency, biofuels do not address global warming concerns. Biodiesel is made from vegetable oils, animal fats or recycled greases. It can be used as a fuel for vehicles in its pure form, or more commonly as a diesel additive to reduce levels of particulates, carbon monoxide, and hydrocarbons from diesel-powered vehicles. Biodiesel is produced from oils or fats using transesterification and is the most common biofuel in Europe. Biofuels provided 2.7% of the world's transport fuel in 2010. Biomass, biogas and biofuels are burned to produce heat/power and in doing so can harm the environment. Pollutants such as sulphurous oxides (SOx), nitrous oxides (NOx), and particulate matter (PM) are produced from the combustion of biomass. With regards to traditional use of biomass for heating and cooking, the World Health Organization estimates that 3.7 million prematurely died from outdoor air pollution in 2012 while indoor pollution from biomass burning effects over 3 billion people worldwide. Geothermal energy High temperature geothermal energy is from thermal energy generated and stored in the Earth. Thermal energy is the energy that determines the temperature of matter. Earth's geothermal energy originates from the original formation of the planet and from radioactive decay of minerals (in currently uncertain but possibly roughly equal proportions). The geothermal gradient, which is the difference in temperature between the core of the planet and its surface, drives a continuous conduction of thermal energy in the form of heat from the core to the surface. The adjective geothermal originates from the Greek roots geo, meaning earth, and thermos, meaning heat. The heat that is used for geothermal energy can be from deep within the Earth, all the way down to Earth's core – down. At the core, temperatures may reach over . Heat conducts from the core to the surrounding rock. Extremely high temperature and pressure cause some rock to melt, which is commonly known as magma. Magma convects upward since it is lighter than the solid rock. This magma then heats rock and water in the crust, sometimes up to . Low temperature geothermal refers to the use of the outer crust of the Earth as a thermal battery to facilitate renewable thermal energy for heating and cooling buildings, and other