The oil can subsequently be gasified to produce the syngas. The coal was gasified by heating the coal in enclosed ovens with an oxygen-poor atmosphere. Historically, coal was gasified to produce coal gas, also known as "town gas". Similarly to combined-cycle plants, the intended fuel is natural gas or gasified coal. Starting from coal, it is gasified. Rice hulls are easily gasified in top-lit updraft gasifiers. With the correct technology it can be gasified and converted to a viable fuel source.