Pla / pha biodegradable coatings for seeds and fertilizers

A method for making a coated granular composition, comprising the steps of:

• mixing polylactic acid and a polyhydroxyalkanoate, optionally in the presence of a solvent, at a temperature from about 25° C. to about 180° C. to provide a coating mixture;
• applying the coating mixture over outer surfaces of a plurality of granulates;
• and
• solidifying the coating mixture to create a biodegradable coating over the outer surfaces of the plurality of granulates,
• wherein the granulates comprise a material selected from the group consisting of seeds, fertilizers, and pesticides, and
• wherein the biodegradable coating comprises a continuous phase of polylactic acid having globules of the polyhydroxyalkanoates homogeneously dispersed therein, wherein the globules have an average size of from about 2 nm to about 10 micron.

A method for controlled release of a granular material, comprising the steps of:

• providing a granular composition comprising a plurality of granulates having a biodegradable coating applied over the granulates, wherein the granulates comprise a material selected from the group consisting of seeds, fertilizers, and pesticides, and wherein the biodegradable coating comprises from about 10 to about 30 weight percent polylactic acid and from about 70 to about 90 weight percent polyhydroxyalkanoates;
• dispersing the granular composition over a plot of soil;
• dissolving at least the polyhydroxyalkanoates in the biodegradable coating by exposing the plot of soil, and the granular composition dispersed therein, to moisture,
• wherein dissolution of the polyhydroxyalkanoates forms a plurality of channels in the biodegradable coating through which the granulate material may be released into the soil.