I came across an article in the online publication Product Design & Development in which Associate Editor Katie Mohr profiled a bicycle helmet that uses wood for the shell as well as an alternative to Styrofoam for the protective inner liner. Mohr was enthused about this wood alternative to Styrofoam, called Cellufoam, because of Styrofoam's pariah status in many cities. She cites the "growing list of cities" that are banning the substance, noting also that "[expanded] polystyrene foam—despite the fact that it's a dangerous, non-recyclable pollutant—is widely used in everything from take-out containers to bicycle helmets."
The idea for Cellufoam came out of a research group within Sweden's Wallenberg Wood Science Center (WWSC; Stockholm) and has been further developed by Cellutech, also based in Stockholm. Cellufoam "is made of nanocellulose produced from wood pulp and is, therefore, both renewable and biodegradable," said Cellutech's information. The wooden bicycle helmet, which has a "durable" paper strap, is the first example of how Cellufoam can be used, said the company, but work is in progress to find other applications that can replace EPS.