Mineral-releasing compost and method of using the same for soil remediation

Abstract

Described herein is a mineral-releasing compost prepared by combining a prebiotic material, a probiotic material, and one or more mineral gluconate salts to form a composting mixture, controlling composting conditions to allow for the composting mixture to decompose, and allowing the composting mixture to fully stabilize and mature, wherein the compost includes one or more minerals as digested products of the respective mineral gluconate salts. The mineral-releasing compost is particularly suitable for remediation of soil contaminated with heavy metals and for amendment of soil deficient of certain minerals.

1 . A compost prepared by:
 combining a prebiotic material, a probiotic material, and one or more mineral gluconate salts to form a composting mixture;   controlling composting conditions to allow for the composting mixture to decompose; and   allowing the composting mixture to fully stabilize and mature, wherein the compost includes one or more minerals as digested products of the respective mineral gluconate salts.   
     
     
         2 . The compost of  claim 1  wherein the prebiotic material comprises one or more cellulosic materials. 
     
     
         3 . The compost of  claim 2  wherein the cellulosic material is grass clippings, leaves or straw. 
     
     
         4 . The compost of  claim 1  wherein the probiotic material comprises  Lactobacillus.    
     
     
         5 . The compost of  claim 1  wherein the mineral gluconate salt is copper gluconate, ferrous gluconate, ferric gluconate, magnesium gluconate, zinc gluconate, cobalt gluconate, or calcium gluconate, potassium gluconate. 
     
     
         6 . The compost of  claim 5  wherein the mineral gluconate salt is ferrous gluconate. 
     
     
         7 . The compost of  claim 1  wherein the one or more minerals are present in the compost at about 1-5% w/w. 
     
     
         8 . A composting mixture comprising:
 a prebiotic material;   a probiotic material; and   one or more mineral gluconate salts.   
     
     
         9 . The composting mixture of  claim 8  wherein the prebiotic material comprises one or more cellulosic materials. 
     
     
         10 . The composting mixture of  claim 9  wherein the cellulosic material is grass clippings, leaves or straw. 
     
     
         11 . The composting mixture of  claim 8  wherein the probiotic material comprises  Lactobacillus.    
     
     
         12 . The composting mixture of  claim 8  wherein the mineral gluconate salt is copper gluconate, ferrous gluconate, ferric gluconate, magnesium gluconate, zinc gluconate, cobalt gluconate, calcium gluconate, or potassium gluconate. 
     
     
         13 . The composting mixture of  claim 8  wherein the mineral gluconate salt is ferrous gluconate. 
     
     
         14 . A method for amending soil comprising:
 contacting the soil with the compost of  claim 1 ; and   allowing the compost to release respective one or more minerals corresponding to the mineral gluconate salt.   
     
     
         15 . The method of  claim 14  wherein the one or more mineral gluconate salts are selected from the group consisting of copper gluconate, ferrous gluconate, ferric gluconate, magnesium gluconate, zinc gluconate, cobalt gluconate, calcium gluconate, and potassium gluconate. 
     
     
         16 . The method of  claim 14  wherein the one or more mineral gluconate salts are selected from the group consisting of magnesium gluconate, calcium gluconate, and potassium gluconate. 
     
     
         17 . The method of  claim 14  wherein the soil contains soil-bound heavy metals and the compost is iron-releasing compost, and wherein amending the soil comprising contacting the iron-containing compost with the soil to bring the soil to an acidic pH of less than 5, whereby at least a portion of the soil-bound heavy metals become bioavailable. 
     
     
         18 . The method of  claim 17 , further comprising washing the soil and extracting at least a portion of the bioavailable heavy metals into a liquid phase. 
     
     
         19 . The method of  claim 18 , further comprising adding an alkaline additive to neutralize the acidic pH to a pH of more than 5, whereby at least a portion of the bioavailable heavy metals are bound to Fe(III), Fe(II) or a combination thereof. 
     
     
         20 . The method of  claim 19 , wherein the alkaline additive is dolomite, sodium hydroxide, or lime. 
     
     
         21 . The method of  claim 17 , wherein the one or more heavy metals are lead, arsenic or a combination thereof. 
     
     
         22 . The method of  claim 14  wherein the soil contains soil-bound phosphorus and the compost is iron-releasing compost, and wherein amending the soil comprises:
 (a) contacting the iron-containing compost with the soil to bring the soil to an acidic pH of less than 5, whereby at least a portion of the soil-bound phosphorus become soluble; 
 (b) extracting the soluble phosphorus into solution phase to provide waste water; and 
 (c) allowing the waste water to filter through an alkaline material layer and an active charcoal layer. 
 
     
     
         23 . The method of  claim 22  wherein the alkaline material layer includes dolomite, sodium hydroxide, lime or a mixture thereof.