How our raw material is produced (one of the primary methods)...

Crude oil is processed in a refinery, where it is separated into different components (fractions) to produce; gasoline, kerosine, diesel and lubricating oil, then you end up with naphtha and a residue that is used to make bitumen for surfacing roads. Most plastics are developed from naphtha. In total, less than 4% of all crude oil is used to make all plastics (from naptha). Less that 1% is used to make EPS.

Polystyrene is extracted from oil during the refining process. Yes, that means EPS is an oil byproduct. Crude oil is not extracted or refined to produce EPS (or other plastics). 

Thousands of small units of styrene, called monomers, link together to form large molecules of polystyrene by a process called polymerization.

Expanded polystyrene starts as small spherical beads with a typical diameter of 0.5-1.5mm. They contain an expanding agent; a pure hydrocarbon, which does not contain any CFC's or halogens and does not damage the earth's protective ozone layer.