plants have an extra benefit in that they can reduce landfilling. In addition, waste-fired power plants can be equipped with material recovery, which is also beneficial to the environment. In some instances, torrefaction of biomass may benefit the power plant if energy crops/biomass is the material the converted fossil fuel power plant will be using. Also, when using energy crops as the fuel, and if implementing biochar production, the thermal power plant can even become carbon negative rather than just carbon neutral. Improving the energy efficiency of a coal-fired power plant can also reduce emissions. Besides simply converting to run on a different fuel, some companies also offer the possibility to convert existing fossil-fuel power stations to grid energy storage systems which use electric thermal energy storage (ETES) Coal pollution mitigation Coal pollution mitigation is a process whereby coal is chemically washed of minerals and impurities, sometimes gasified, burned and the resulting flue gases treated with steam, with the purpose of removing sulfur dioxide, and reburned so as to make the carbon dioxide in the flue gas economically recoverable, and storable underground (the latter of which is called "carbon capture and storage"). The coal industry uses the term "clean coal" to describe technologies designed to enhance both the efficiency and the environmental acceptability of coal extraction, preparation and use, but has provided no specific quantitative limits on any emissions, particularly carbon dioxide. Whereas contaminants like sulfur or mercury can be removed from coal, carbon cannot be effectively removed while still leaving a usable fuel, and clean coal plants without carbon sequestration and storage do not significantly reduce carbon dioxide emissions. James Hansen in an open letter to then U.S. President Barack Obama advocated a "moratorium and phase-out of coal plants that do not capture and store CO2". In his book Storms of My Grandchildren, similarly, Hansen discusses his Declaration of Stewardship, the first principle of which requires "a moratorium on coal-fired power plants that do not capture and sequester carbon dioxide". Running the power station on hydrogen converted from natural gas Gas-fired power plants can also be modified to run on hydrogen. Hydrogen can at first be created from natural gas through steam reforming, as a step towards a hydrogen economy, thus eventually reducing carbon emissions. Since 2013, the conversion process has been improved by scientists at Karlsruhe Liquid-metal Laboratory (KALLA), using a process called methane pyrolysis. They succeeded in