# US 10,370,681 B2 · Methods of anaerobic digestion of biomass to produce biogas

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- Number: US 10,370,681 B2
- Document ID: US10370681B2
- Status: Granted
- Kind: B2
- Application number: 15/338,417
- Filed: 2016-10-30
- Published: 2017-02-16
- Granted: 2019-08-06
- Earliest claimed: 2012-09-13
- Assignees: Viresco AD, LLC
- Applicants: Novus Energy, LLC
- Inventors: Surya Raja Pidaparti; Jeffrey Ray Zierdt; Joseph Philip Burke
- Web page: https://patentgrep.com/patent/US10370681B2

## CPC

- C12P 5/023: {Methane}
- C12M 21/04: {for producing gas, e.g. biogas (digesters for manure with production of biogas A01C3/028, biological treatment of water, waste water or sewage C02F3/00, C02F11/02, preparation of natural gas or syngas C10L3/06, C10L3/10)}
- C12M 23/36: {Means for collection or storage of gas; Gas holders}
- C12M 23/52: {Mobile; Means for transporting the apparatus (transportable laboratories B01L1/52)}
- C12M 25/16: {Particles; Beads; Granular material; Encapsulation (chemical or physical processes conducted in the presence of fluids and solid particles B01J8/00)}
- C12M 29/00: {Means for introduction, extraction or recirculation of materials, e.g. pumps (pumps per se F04B)}
- C12M 41/00: {Means for regulation, monitoring, measurement or control, e.g. flow regulation (controlling or regulating chemical, physical or physicochemical processes B01J19/0006; heating or cooling apparatus for laboratory use B01L7/00; electro optical investigation of individual particles, flow cytometers G01N15/14; automatic analysis G01N35/00; controlling or regulating in general G06N)}
- C12M 41/28: {of redox potential}
- C12M 41/48: {Automatic or computerized control (automatic analysis G01N35/00)}
- C12M 45/02: {by mechanical forces; Stirring; Trituration; Comminuting (crushing, pulverizing, disintegrating in general B02C)}
- C12M 45/04: {Phase separators; Separation of non fermentable material; Fractionation}
- C12M 45/06: {by chemical means or hydrolysis}
- Y02E 50/30: Fuel from waste, e.g. synthetic alcohol or diesel
- C12P: FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE {(brewing of beer C12C; producing vinegar C12J; producing specific peptides or proteins C07K; producing enzymes C12N9/00; DNA or RNA concerning genetic engineering, vectors, e.g. plasmids, or their isolation, preparation or purification C12N15/00; measuring or testing processes involving enzymes or microorganisms C12Q; measuring or testing processes involving nucleic acid amplification reactions C12Q1/6844; fermentation processes to form a food composition, A21 or A23; compounds in general, see the relevant compound class, e.g. C01, C07)}
- C12M: APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; {APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS}
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

Improved methods for anaerobic digestion of organic matter to produce biogas. Among the improvements given are including ferric iron in a hydrolysis reactor to increase the rate and efficiency of anaerobic hydrolysis to provide substrates for methanogenesis. A solids separation step is added after hydrolysis and before methanogenesis to improve the efficiency of the methanogenesis step. Other improvements involve using separate tanks for the hydrolysis and methanogenesis stages and using two (or more) methanogenesis tanks in sequence, and switching the order of the two (or more) methanogenesis tanks periodically.

## Claims

### Claim 1

A method of producing biogas comprising:
(a)(i) transferring an organic substrate to a hydrolysis tank;
(a)(ii) hydrolyzing the substrate in anaerobic conditions in the hydrolysis tank to produce a hydrolysis liquid effluent;
(b)(i) transferring the hydrolysis liquid effluent for a period of time 1 to a methanogenesis tank 1 comprising fixed film methanogens or granular methanogens and producing biogas and methanogenesis tank 1 liquid effluent;
(b)(ii) transferring the methanogenesis tank 1 liquid effluent to a methanogenesis tank 2 comprising fixed film methanogens or granular methanogens during period of time 1 and producing biogas and methanogenesis tank 2 liquid effluent in methanogenesis tank 2;
(b)(iii) discharging methanogenesis tank 2 liquid effluent during period of time 1;
and then switching the order of methanogenesis tanks 1 and 2 and
(c)(i) transferring the liquid hydrolysis effluent for a period of time 2 to said methanogenesis tank 2 and producing biogas and methanogenesis tank 2 liquid effluent in methanogenesis tank 2;
(c)(ii) transferring the methanogenesis tank 2 liquid effluent to said methanogenesis tank 1 during period of time 2 and producing biogas and methanogenesis tank 1 liquid effluent in methanogenesis tank 1;
(c)(iii) discharging methanogenesis tank 1 liquid effluent during period of time 2.

### Claim 2 (depends on 1)

The method of claim 1, wherein the organic substrate comprises solids, and further comprises before step (a)(i)
(a)(i) grinding the organic substrate comprising solids to produce smaller solids.

### Claim 3 (depends on 1)

The method of claim 1 further comprising after step (a)(ii):
(a)(iii) transferring effluent from the hydrolysis tank to a solids separator; and
(a)(iv) separating solids from the hydrolysis effluent to produce a solids fraction and a screened hydrolysis effluent, wherein the screened hydrolysis effluent is then the hydrolysis liquid effluent in steps (b) and (c).

### Claim 4 (depends on 1)

The method of claim 1 wherein step a(ii) comprises hydrolyzing the substrate in anaerobic condition in a hydrolysis tank comprising Fe3+ particles.

### Claim 5 (depends on 1)

The method of claim 1 further comprising:
(d) switching the order of methanogenesis tanks 1 and 2 and repeating steps (b)(i), (b)(ii), and (b)(iii).

### Claim 6 (depends on 5)

The method of claim 5 wherein time period 1 and time period 2 are preset time periods.

### Claim 7 (depends on 1)

The method of claim 1 wherein the period of time 1 and the period of time 2 are each between 6 and 24 hours inclusive.

### Claim 8 (depends on 1)

The method of claim 1 wherein the methanogenesis tank 1 and the methanogenesis tank 2 each have a hydraulic retention time of 48 hours or less.

### Claim 9 (depends on 1)

The method of claim 1 further comprising monitoring oxidization-reduction potential (ORP) in methanagenesis tank 1 and/or methanogenesis tank 2, wherein the methanogenesis tank receiving the hydrolysis effluent is the lead methanogenesis tank, and the methanogenesis tank receiving methanogenesis tank liquid effluent from the lead methanogenesis tank, is the lag methanogenesis tank, and wherein the switching step (c) occurs when the ORP in the lead methanogenesis tank rises to a preset value or the ORP in the lag methanogenesis tank falls to a preset value.

### Claim 10 (depends on 9)

The method of claim 9 wherein the switching step (c) occurs when the ORP in the lead methanogenesis tank rises to a preset value between about −400 and −300 mV or the ORP in the lag methanogenesis tank falls to a preset value between about −450 and −550 mV.

### Claim 11 (depends on 1)

The method of claim 1 wherein the sum of the hydraulic retention times for the hydrolysis tank and methanogenesis tank 1 and methanogenesis tank 2 is a total hydraulic retention time, and wherein the total hydraulic retention time is 8 days or less.

### Claim 12 (depends on 1)

The method of claim 1 further comprising:
(d) passing the biogas produced in methanogenesis tanks 1 and 2 through a foam trap to trap foam and separate it from the biogas; and
(e) collecting the biogas downstream of the foam trap.