Unlike many composites, you won’t find any preservatives or biocides in Terratec Naturals. Composite decking materials can contain 50% wood fiber or more, which makes them susceptible to wood-type problems like; mold, mildew, bugs, rot, staining and significant fading. The common way to prevent this is to use biocides and preservatives. But, this only delays the inevitable. Terratec's solution to this is problem is adding rice hulls to the mix. They are naturally resistant to mold, mildew and insects because they contain virtually no digestible nutrients. They are also moisture resistant and less likely to stain due to their high silica content.