Solvent extraction of products from algae

Abstract

Processes for extracting product molecules from an algae feed are provided. The algae feed represents an input stream, batch sample, or other algae portion suitable for use in product extraction. The product extraction is typically performed at pressures greater than ambient pressure. This allows for improved extraction, including the potential for use of extraction solvents at temperatures greater than the boiling point for the solvent.

1 . A method for recovering products from algae, comprising:
 mixing an algae feed with particulate solids, the algae feed comprising from 0.1 wt % to about 30 wt % algae in water, the particulate solids having an average particle size between about 1 μm and about 200 μm, the weight of the particulate solids being at least about 10% of the weight of the algae feed, to product a mixed particulate-algae product;   performing a washing step on the mixed particulate-algae product to produce a washed mixed particulate-algae product and a wash effluent, wherein the washing step comprises exposing the mixed particulate-algae product to an amount of water corresponding to at least the dry weight of the algae feed at a temperature of about 25° C. to about 100° C. and at a pressure of about 100 psig (0.7 MPag) to about 2500 psig (17.2 MPag);   exposing the washed mixed particulate-algae product to a solvent under effective solvent extraction conditions, wherein the solvent is water-miscible and wherein the effective solvent extraction conditions include a temperature greater than the boiling point of the solvent and a pressure greater than the vapor pressure of the solvent at the extraction temperature, to form an extraction mixture comprising the particulate solids, residual algae solids, the solvent, water, and extracted products; and   recovering at least a portion of the extracted products from the extraction mixture.   
     
     
         2 . A method according to  claim 1 , wherein the extracted products comprise lipids or oils. 
     
     
         3 . A method according to  claim 1 , wherein the particulate solids comprise diatomaceous earth. 
     
     
         4 . A method according to  claim 1 , wherein the solvent comprises an alcohol containing four carbons or less, a ketone containing four carbons or less, dioxane, tetrahydrofuran, or acetonitrile. 
     
     
         5 . A method according to  claim 1 , wherein the solvent is selected from the group consisting of ethanol, methanol, propanol, and isopropanol. 
     
     
         6 . A method according to  claim 1 , wherein the effective solvent extraction conditions comprise a temperature of at least about 40° C. and a pressure of about 100 psig (0.7 MPag) to about 2500 psig (17.2 MPag). 
     
     
         7 . The method of  claim 6 , wherein the effective solvent extraction conditions comprise a pressure of about 300 psig (2.1 MPag) to about 2000 psig (13.8 MPag). 
     
     
         8 . The method of  claim 1 , wherein the effective solvent extraction conditions comprise a temperature of about 80° C. to about 200° C. 
     
     
         9 . The method of  claim 1 , wherein recovering at least a portion of the extracted products comprises a filtering step, wherein the filtering step is used to separate liquids comprising extracted products from the particulate solids and residual algal solids. 
     
     
         10 . A method according to  claim 1 , wherein the washing step comprises exposing the algae feed mixed with particulate solids to water for about 1 minute to about 20 minutes. 
     
     
         11 . The method of  claim 1 , wherein the effective washing conditions comprise exposing the mixed particulate-algae product to a pressure of about 300 psig (2.1 MPag) to about 2000 psig (13.8 MPag). 
     
     
         12 . The method of  claim 1 , wherein at least a portion of the wash effluent is recycled to an algae growth environment. 
     
     
         13 . The method of  claim 12 , wherein recycling at least a portion of the wash effluent comprises:
 separating metal salts, water-soluble proteins, water-soluble carbohydrates, or a combination thereof from water in the wash effluent; and   recycling at least a portion of the separated metal salts, water-soluble proteins, water-soluble carbohydrates, or combination thereof.   
     
     
         14 . The method of  claim 1 , wherein recovering at least a portion of the extracted products further comprises recovering at least a portion of the solvent, and wherein the algae feed is exposed to a solvent comprising at least a portion of the recovered solvent. 
     
     
         15 . The method of  claim 1 , further comprising;
 recovering at least a portion of the particulate solids and residual algae solids; and   regenerating the recovered particulate solids by digesting the residual algae solids,   wherein the algae feed is mixed with particulate solids comprising at least a portion of the regenerated, recovered particulate solids.   
     
     
         16 . A method for recovering products from algae, comprising:
 mixing an algae feed comprising from about 5 wt % to about 30 wt % algae in water with diatomaceous earth to product a mixed diatomaceous earth-algae product;   washing the mixed diatomaceous earth-algae product with water at a temperature of from about 25° C. and about 100° C. under pressure of from about 300 psi (2.1 MPag) to about 2000 psi (13.8 MPag) to produce a washed mixed diatomaceous earth-algae product and a wash effluent;   exposing the washed mixed diatomaceous earth-algae product to a water-miscible solvent under effective solvent extraction conditions, the effective solvent extraction conditions including a temperature of at least about 80° C. and a pressure of about 100 psig (0.7 MPag) to about 2500 psig (17.2 MPag), the temperature being greater than the standard boiling point of the water-miscible solvent and the pressure being greater than a vapor pressure of the water-miscible solvent at the temperature, to form an extraction mixture comprising the water-miscible solvent, water, extracted products, diatomaceous earth, and residual algae solids;   separating the water-miscible solvent, water, and extracted products from the diatomaceous earth and residual algae solids by passing water-miscible solvent, water, and extracted products through a filter; and   recovering at least a portion of the extracted products from the water-miscible solvent, water, and extracted products.   
     
     
         17 . A method according to  claim 16 , wherein the extracted products comprise lipids or oils. 
     
     
         18 . A method according to  claim 16 , wherein washing the algae feed mixed with diatomaceous earth comprises exposing the algae feed mixed with diatomaceous earth to water for about 1 minute to about 20 minutes. 
     
     
         19 . The method of  claim 16 , wherein the water-miscible solvent comprises ethanol. 
     
     
         20 . The method of  claim 16 , wherein the effective solvent extraction conditions comprise a pressure of about 300 psig (2.1 MPag) to about 2000 psig (13.8 MPag).