Ethanol production from biological wastes
The invention provides methods, apparatuses, and kits for producing ethanol and other alcohols. The methods involve fermenting organic material in a fermentation mixture to a biogas comprising methane; converting at least a portion of the biogas to synthesis gas comprising CO and H 2 ; and contacting at least a portion of the synthesis gas with a catalyst to produce alcohol. In some embodiments, a microorganism that reduces ferric iron to ferrous iron is included in the fermentation mixture to enhance the efficiency of the fermentation and the yield of alcohol. The invention also provides a method of producing alcohol involving fermenting organic material to a biogas comprising methane; removing sulfhydryls from the biogas; converting at least a portion of the biogas to synthesis gas comprising CO and H 2 ; contacting at least a portion of the synthesis gas with a sulfur-free catalyst to produce a substantially sulfur-free alcohol; and purifying the alcohol wherein the purified alcohol is substantially sulfur-free and comprises less than 5% methanol and at least 70% C 2 + alcohols by weight.
1. A method of producing alcohol comprising:
fermenting organic material in a fermentation mixture to a biogas comprising methane, wherein the fermentation mixture comprises a microorganism that reduces Fe 3+ and produces at least one volatile organic acid from organic substrates;
converting at least a portion of the biogas to synthesis gas comprising CO and H 2 ; and
contacting at least a portion of the synthesis gas with a catalyst to produce alcohol.
2. The method of claim 1 wherein the microorganism that reduces Fe 3+ is derived from ATCC 55339.
3. The method of claim 1 wherein the fermentation mixture further comprises an iron source.
4. The method of claim 3 wherein the iron source is magnetite.
5. The method of claim 1 wherein the step of converting at least a portion of the biogas to synthesis gas comprises partially oxidizing at least a portion of the biogas.
6. The method of claim 1 further comprising purifying the alcohol, wherein the purified alcohol comprises less than 0.5% by weight methanol.
7. The method of claim 6 wherein the step of purifying the alcohol comprises fractionating the alcohol into a C 2 +-rich fraction and a methanol-rich fraction, wherein the method further comprises recirculating the methanol-rich fraction into the synthesis gas for contact with the catalyst.
8. The method of claim 1 further comprising purifying the alcohol wherein the purified alcohol comprises at least 60% by weight ethanol.
9. The method of claim 1 wherein the contacting step produces heat that is used to heat the fermentation mixture.
10. The method of claim 1 wherein the iron-reducing microorganism produces Fe 2+ that binds sulfhydryls in the fermentation mixture.
11. The method of claim 1 wherein the step of fermenting organic material to a biogas comprises the steps of feeding the organic material into a vessel, fermenting and mixing the organic material in anaerobic conditions in the vessel to form the biogas, discontinuing the mixing to allow particulate unfermented organic material to settle in the vessel resulting in the formation of a low-suspended-solid supernatant, decanting the supernatant from the vessel, and repeating at least the feeding and fermenting steps.
12. The method of claim 11 further comprising withdrawing at least a portion of the biogas from the vessel immediately before the settling.
13. The method of claim 1 wherein the organic material comprises dairy manure.
14. The method of claim 1 wherein the organic material comprises hog manure, turkey manure, chicken manure, slaughterhouse waste, municipal sewage, or crop waste.
15. The method of claim 14 wherein the organic material comprises crop waste, wherein the crop waste is sugar beet waste.
16. The method of claim 1 wherein the organic material comprises forest products waste.
17. The method of claim 1 wherein the alcohol comprises C 2 + alcohols, the yield of C 2 + alcohols is at least 6 gallons per 1000 cubic feet of methane in the biogas, and the conversion of volatile organics in the fermentation mixture to biogas is at least 65% efficient.
18. The method of claim 10 wherein the catalyst is sulfur-free and the alcohol comprises less than 10 ppm sulfur atoms.
19. The method of claim 18 wherein the alcohol comprises less than 1 ppm sulfur atoms.
20. The method of claim 18 wherein the method further comprises contacting the biogas with a sulfur scrubber separate from the Fe 2+ produced by the iron-reducing microorganism.