Lego Blocks from Straw

Ethanol Producer magazine, California produces 1.35 million tons of rice straw annually from the 600,000 acres (240,000 ha) in rice production, and only 3%–4% of that straw is used commercially.

Stak Blocks are 12" x 12" x 24" (305 x 305 x 610 mm) and weigh 30 pounds (14 kg), with a density of 15 lbs/ft3 (240 kg/m3)—about twice that of typical straw bales. The straw fibers are held together with a polyurethane binder (MDI), used at a concentration of about 2% by weight, according to company president Jay Ruskey. The blocks have a high enough density to create load-bearing walls with simple stacking. (With strawbale construction, load-bearing applications require special measures to prevent cracking of plaster as bales compress over time.) Stak Blocks interlock with molded bumps and dimples (think Lego), leaving a channel that is used for a threaded rod to secure the top plate to the foundation. The cavities could also be filled with re-bar and concrete to create a sort of insulated concrete form, though the diameter of the concrete columns would be fairly small.