Method for converting biomass to methane or ethanol
A method for enhancing the treatment of lignocellulose-containing materials by biotreatment wherein such lignocellulose-containing materials, normally resistant to biotreatment, are first subjected to a low-temperature, long-residence time pyrolysis at about 175° C. to about 325° C. for about 0.1 hour to about 2.0 hours, wherein a substantial portion of the incoming material is distilled into water-soluble compounds amenable to anaerobic biotreatment. Exemplary applications of the method include pyrolytic pre-treatment of wastewater sludges, cellulosic wastes, wood, peat, plant residues, low-grade coal, and the like to enhance methane gas production in anaerobic digestion and/or oxygen-limited or oxygen-starved fermentation to produce ethanol.
1. A method for converting biomass-based ligno-cellulosic materials in a biotreatment process to produce at least one of a methanaceous fuel gas and ethanol, comprising:
subjecting said biomass-based ligno-cellulosic materials to pyrolysis to produce (a) a pyroligneous acid wherein a substantial portion is comprised of wood alcohol and wood vinegar, (b) a pyrogas containing methane, carbon monoxide, hydrogen and water, and (c) pyrosolids including char, ash, and residual lignin-containing materials;
separating pyrosolids from said pyroligneous acid, and pyrogas; and
subjecting said pyroligneous acid to an anaerobic biological treatment step to produce at least one of a methane-bearing biogas and ethanol.
2. A method in accordance with claim 1 , wherein said pyrolysis is conducted at a temperature of between about 175° C. to about 325° C.
3. A method in accordance with claim 1 , wherein said pyrolysis is conducted with a solids residence time of between about 0.1 hour and about 2 hours.
4. A method in accordance with claim 1 , wherein said pyrolysis is conducted with a solids residence time of about 0.1 hour and about 0.5 hour.
5. A method in accordance with claim 1 , wherein said anaerobic biological treatment step is conducted with methanogenic microorganisms.
6. A method in accordance with claim 1 , wherein at least a portion of said separated pyrogas is introduced into said anaerobic biological treatment step.
7. A method in accordance with claim 1 , wherein a major portion of said separated pyrogas is introduced into said anaerobic biological treatment step.
8. A method in accordance with claim 1 , wherein said separated pyrosolids are used as an agronomic soil amendment.
9. A method in accordance with claim 1 , wherein said anaerobic biological treatment step is conducted with ethanol-producing microorganisms.
10. A method in accordance with claim 9 , wherein said microorganisms include yeast.
11. A method in accordance with claim 9 , wherein said method further includes a step of removing toxic substances from said pyroligneous acid before introduction into said treatment step.
12. A method in accordance with claim 9 , wherein said method includes a further step of adding at least one of a sugar and vitamins and minerals to said anaerobic biological treatment step.
13. A method for treating lignocellulose—containing material, comprising the steps of:
introducing a first lignocellulose-containing material to an anaerobic biotreatment step in a digester wherein methanogenic microorganisms produce a methane-containing biogas and an aqueous stream containing residual biosolids;
separating said biogas from said aqueous stream containing biosolids;
dewatering said residual biosolids;
subjecting said residual biosolids to pyrolysis to produce a pyrolysis product comprising a gas;
mixing said gas into a stream drawn from said digester; and,
recycling said stream back to said digester.
14. A claim in accordance with claim 13 , wherein said pyrolysis is conducted at a temperature of about 175° C. to about 325° C.
15. A claim in accordance with claim 13 , wherein said pyrolysis is conducted with a solids residence time of about 0.1 hour to about 2.0 hours.
16. A claim in accordance with claim 13 , wherein said pyrolysis is conducted with a solids residence time of about 0.1 hour to about 0.5 hours.