I just saw a news article about this chinese company, Jiangsu Jinghe Hi-Tech, which has developed a PLA alternative out of straw. That is dried crop straw, combined with a plastic formulation that actually prints.

It has been created because there is always an abundance of this straw material left over from farmers crops. Instead of having to burn it they can now use it to make 3D printer filament apparently. It supposedly has an earthly wood feel and is pretty cheap.