Environmental concerns are associated with the production of cement specifically the hardening and binding element of concrete. The cement industry is one of the highest producers of CO₂ emissions, producing about 7% of emissions globally. The sintering of limestone in the rotary kilns is the primary source of industry emissions. The quarrying of raw materials cuts away 9 billion tons of earth per year. The heavy use of concrete in urban areas creates excess surface run off and flooding. This can cause massive soil erosion and carries contaminates to major waterways. Demolition of concrete structures introduces fine toxic particles like crystalline silica into the atmosphere. The concrete industry uses incredible amounts of energy to transport and manufacture goods. There are currently many programs being supported and funded by the concrete industry. These programs aim to produce new methods and compounds of concrete that are similar in durability, while being more eco-friendly.