Biopolymer-based growth media, and methods of making and using same

Abstract

Compositions and methods that relate to a biopolymer medium for growing plants. In certain embodiments, the biopolymer growth medium comprises or consists essentially of polylactic acid (PLA), polyhydroxyalkanoate (PHA) or a mixture of them. Another aspect of the invention relates to a method of producing a biopolymer growth medium.

I claim: 
     
       1. A method for producing a biodegradable, plant growth medium comprising the steps of:
 a. providing a biopolymer; 
 b. melt processing the biopolymer into fibers; and 
 c. dispensing the fibers into a shaped cavity mold, thereby forming a growth medium; 
 d. wherein the fibers are in a melted or semi-melted state after the melt processing step, the fibers fuse directly together one to another at a plurality of contact points once dispensed, and the dispensed fibers conform to the shape of the cavity mold. 
 
     
     
       2. The method of  claim 1 , wherein the biopolymer is selected from the group consisting of polylactic acid and polyhydroxyalkanoates. 
     
     
       3. The method of  claim 1 , further comprising the step of adding a surfactant to the biopolymer. 
     
     
       4. The method of  claim 3 , wherein the surfactant is selected from the group consisting of ethylene oxide/propylene oxide block copolymers, glycerol, and lecithin. 
     
     
       5. The method of  claim 1 , further comprising the step of adding a wetting agent to the biopolymer. 
     
     
       6. The method of  claim 5 , wherein the wetting agent is selected from the group consisting of dialkyl sulfosuccinates, anionic sulfonated aliphatic esters or polyoxyethylene esters. 
     
     
       7. The method of  claim 1 , further comprising the steps of forming a channel for seed placement and root growth or dibbling the growth medium; and planting a seed within the growth medium. 
     
     
       8. The method of  claim 1 , further comprising the steps of slicing the growth medium; and planting a plantlet within the growth medium. 
     
     
       9. The method of  claim 1 , further comprising the step of introducing a gas during the melt processing. 
     
     
       10. The method of  claim 9 , wherein the gas is nitrogen. 
     
     
       11. The method of  claim 1 , further comprising the step of adding a chemical blowing agent to the biopolymer before the melt processing. 
     
     
       12. The method of  claim 11 , wherein the chemical blowing agent comprises citric acid and sodium bicarbonate. 
     
     
       13. The method of  claim 1 , wherein the growth medium has an at least partially reticulated, open cell structure. 
     
     
       14. The method of  claim 1 , wherein the shaped cavity mold is a propagating tray on a moving flat belt. 
     
     
       15. A plant growth medium prepared by a method comprising the steps of:
 a. providing a biopolymer; 
 b. melt processing the biopolymer into fibers; and 
 c. dispensing the fibers into a shaped cavity mold, thereby forming the growth medium; 
 d. wherein the fibers are in a melted or semi-melted state after the melt processing step, the fibers fuse directly together one to another at a plurality of contact points once dispensed, and the dispensed fibers conform to the shape of the cavity mold. 
 
     
     
       16. The method of claim 1, wherein the growth medium is further formed in the shape of a slab. 
     
     
       17. The method of claim 1, wherein the growth medium is further formed in the shape of a mat. 
     
     
       18. The method of claim 1, wherein the growth medium is further formed in the shape of a free standing block. 
     
     
       19. The method of claim 1, wherein the growth medium is further formed in the shape of a substrate containing multiple layers. 
     
     
       20. The method of claim 1, further comprising the step of introducing a gas during the melt processing and wherein the growth medium is further formed as a foamed structure. 
     
     
       21. The method of claim 20, wherein the foamed structure is further formed formed as a sheet and then die cut. 
     
     
       22. The method of claim 1, wherein the growth medium includes a vertical grain such that the fibers therein are substantially in a plane perpendicular to the ground when the growth medium is laid flat. 
     
     
       23. The plant growth medium of claim 15, wherein the growth medium is in the shape of a slab. 
     
     
       24. The plant growth medium of claim 15, wherein the growth medium is in the shape of a mat. 
     
     
       25. The plant growth medium of claim 15, wherein the growth medium is in the shape of a free standing block. 
     
     
       26. The plant growth medium of claim 15, wherein the growth medium is a substrate containing multiple layers. 
     
     
       27. The plant growth medium of claim 15, further comprising the step of introducing a gas during the melt processing and the growth medium is a foamed structure. 
     
     
       28. The plant growth medium of claim 27, wherein the foamed structure is formed as a sheet and then die cut. 
     
     
       29. The plant growth medium of claim 27, wherein the foamed structure is dispensed into the mold to create a shape. 
     
     
       30. The plant growth medium of claim 15, wherein the growth medium includes a vertical grain such that the fibers therein are substantially in a plane perpendicular to the ground when the growth medium is laid flat.