It could be Styrofoam, or something that looks like it.
Faswall could look like a Styrofoam product; however, it is cement-bonded wood fiber. It could be Styrofoam, which has the green benefit of being a superior insulator (thus promoting energy efficiency). The Dow company even received Building Products magazine's Most Valuable Product and earned a Green Products Award for its Styrofoam SIS.
Some would argue -- as you do -- that it is not green at all, because it is not a green material. With your question, you have demonstrated the conundrum of building green!
For example, bamboo flooring is considered a green product because it is renewable. However, it is not local (something to factor in when building green), and some bamboo products even contain formaldehyde, which is bad for indoor air quality (another green building concern).
Although fiberglass is considered to be "the asbestos of the 21st century," fiberglass insulation is considered green because it promotes energy efficiency. Recycled cotton insulation is a much greener choice.
The list goes on. There are often tradeoffs with green building, and some green building practices are greener than others as you have observed.
For more information:
Read "Choosing the Best Insulation Delivers Energy Savings" fordetails of each insulation material's pros and cons.