Patent ID: 8759424

Claim:
A building article composed of a biodegradable composite structural building material coated with a layer of anaerobically biodegradable composite material; wherein the layer of anaerobically biodegradable composite coating material is composed of a polyhydroxyalkanoate (PHA) polymer matrix, and a filler composed of particles dispersed in the PHA polymer matrix; wherein the particles have pores with diameters less than 2 nm, wherein the particles have diameters within the range 0.1 mm to 1.0 mm, and wherein the particles have a hygroscopic expansion of at most 2%; wherein the hygroscopic expansion of at most 2% is defined to mean that a fractional amount of linear expansion the particles experience as a result of being saturated by moisture is at most 2%; wherein the particles dispersed in the PHA polymer matrix are composed of ground bone meal.