Stak Blocks, not yet in production, are approximately twice the density of straw bales, and the molded bumps and dimples allow the blocks to be stacked like Legos.
For those who loved playing with Lego blocks as kids, Stak Block, from the Goleta, California, company Oryzatech, may be a dream come true. The company is still looking for funding to build a factory but has developed and tested its product: a straw-composite, structural building block made from 96% rice straw. An underutilized waste agricultural product, rice straw has become a disposal problem since burning straw in fields was banned in California and elsewhere. According to the October 2006 issue of
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
)—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.