Hydrothermal carbonization of algal feedstocks and fuels produced thereby

Abstract

In one embodiment, the present disclosure provides a method for producing a solid fuel. A feedstock that includes algae or delipidized algal residue and a liquid carrier is heated to a suitable temperature, at a suitable pressure, and for a suitable amount of time to form a desired amount of solid hydrochar. The hydrochar is collected and compressed into a compressed solid.

We claim: 
     
         1 . A method for producing solid fuel comprising:
 providing a feedstock comprising algae or delipidized algal residue and a liquid carrier;   heating the feedstock at a temperature of between about 120° C. and about 250° C., and a pressure of between about 2 bar and about 40 bar for a period of between about 5 minutes and about 16 hours, thereby forming an amount of a solid hydrochar;   collecting the hydrochar; and   compressing the hydrochar into a compressed solid.   
     
     
         2 . The method of  claim 1 , wherein the feedstock comprises between about 2% and about 10% by weight algae or delipidized algal residue. 
     
     
         3 . The method of  claim 1 , wherein the feedstock comprises less than about 20% by weight of algae or delipidized algal residue. 
     
     
         4 . The method of  claim 1 , wherein the hydrochar is compressed at a temperature of between about 25° C. and about 200° C. 
     
     
         5 . The method of  claim 1 , wherein the hydrochar is compressed at a temperature of between about 100° C. and about 160° C. 
     
     
         6 . The method of  claim 1 , wherein the hydrochar is compressed at a temperature of between about 120° C. and about 180° C. 
     
     
         7 . The method of  claim 1 , wherein the hydrochar is compressed at a temperature of between about 140° C. and about 160° C. 
     
     
         8 . The method of  claim 1 , wherein the hydrochar is compressed at a temperature of less than about 200° C. 
     
     
         9 . The method of  claim 1 , wherein the hydrochar is compressed at a temperature less than a temperature typically used to compress hydrochar produced from the hydrothermal carbonization of lignocellulosic biomass. 
     
     
         10 . The method of  claim 1 , wherein the hydrochar is compressed without the addition of an external binder. 
     
     
         11 . The method of  claim 1 , wherein the hydrochar is capable of being compressed without the addition of an external binder. 
     
     
         12 . The method of  claim 1 , wherein the hydrochar is compressed essentially without the addition of an external binder. 
     
     
         13 . The method of  claim 1 , wherein the hydrochar is compressed with less than about 10% by weight of an external binder. 
     
     
         14 . The method of  claim 1 , wherein the hydrochar is compressed with less than about 5% by weight of an external binder. 
     
     
         15 . The method of  claim 1 , wherein the hydrochar is mixed with hydrochar produced from hydrothermal carbonization of a lignocellulosic feedstock and the mixture is compressed. 
     
     
         16 . The method of  claim 1 , wherein the temperature is between about 150° C. and about 250° C. and the pressure is between about 5 bar and about 40 bar, and the reaction time is between about 5 minutes and about 2 hours. 
     
     
         17 . The method of  claim 1 , wherein the temperature is between about 180° C. and about 250° C., the pressure is between about 5 bar and about 40 bar, and the reaction time is between about 5 minutes and about 1 hour. 
     
     
         18 . The method of  claim 1 , wherein the feedstock comprises delipidized algal residue. 
     
     
         19 . The method of  claim 1 , wherein the feedstock comprises whole algae. 
     
     
         20 . The method of  claim 1 , wherein the feedstock consists essentially of delipidized algal residue and/or algae and the liquid carrier.