The Solvay process or ammonia-soda process is the major industrial process for the production of sodium carbonate (soda ash). The ammonia-soda process was developed into its modern form by Ernest Solvay during the 1860s. The ingredients for this process are readily available and inexpensive: salt brine (from inland sources or from the sea) and limestone (from mines). The worldwide production of soda ash in 2005 has been estimated at 42 million tons (92 billion pounds), which is more than six kilograms per year (13 lb) for each person on Earth. Solvay-based chemical plants now produce roughly three-quarters of this supply, with the remainder being mined from natural deposits.