Exploded biomass based slow-release fertilizer
A fertilizer product comprising an acid-carbonized microporous matrix derived from expanded biomass and a fertilizer reaction product of residual acid from the carbonizing process and at least one added fertilizer precursor. The biomass may include steam exploded wood powder. The expanded biomass may be carbonized with a combination of sulphuric and phosphoric acids, followed by ammoniation to produce ammonium sulphate and mono- or diammonium phosphate. The fertilizer reaction product adsorbs onto the carbon matrix, which results in a slow-release when the material is applied to the soil.
1. A method of forming a fertilizer product, comprising the steps of:
(a) carbonizing an expanded biomass material with an acid to form a microporous carbon matrix, leaving residual acid in the pore volume of the microporous carbon matrix, wherein the biomass is expanded by steam explosion, prior to carbonization to have an exposed ruptured cell pore volume, wherein the expanded biomass material saturated with steam at about 120° C. to 200° C., as produced by the steam explosion, is quenched with the acid at a lower temperature than the temperature of the expanded biomass material; and
(b) adding a fertilizer precursor to react with the residual acid to form a fertilizer in the pore volume of the microporous carbon matrix.
2. The method of claim 1 wherein a mechanical defibrillation method is used as a pre-treatment step for steam explosion.
3. The method of claim 1 wherein the biomass is expanded by steam explosion having a severity index of greater than about 2.0.
4. The method of claim 1 wherein the expanded biomass material is carbonized with a quantity of acid less than or equal to 93% ratio of acid to biomass by weight.
5. The method of claim 4 wherein the expanded biomass material is carbonized with a quantity of acid greater than about 25% and less than or equal to 93% ratio of acid to biomass by weight.
6. The method of claim 4 wherein the acid comprises sulphuric acid.
7. The method of claim 1 , wherein the amount of acid used leaves open pore volume and the fertilizer precursor is added to the open pore volume.
8. The method of claim 1 wherein the acid comprises one or a combination of sulphuric acid, phosphoric acid or nitric acid.
9. The method of claim 1 wherein lignin of the biomass is exposed by the steam explosion, and the acid comprising sulphuric acid reacts with the exposed lignin to form a lignosulphonate reaction product.