USE OF BIOMAGNETISM FOR BIOGAS PRODUCTION

Abstract

A method for improving a biogas production is provided in which an organic substrate is pretreated by various methods. In particular, the method includes a combination of a magnetic and an enzymatic pretreatment of the substrate with an attractive specific energy gain. The application of a magnetic field induces changes in biological systems

Claims

1. A method to produce biogas from organic substrates comprising: providing an organic substrate; mixing the organic substrate with an enzyme to form an enzyme-substrate complex; exposing the enzyme-substrate complex to an induced magnetic field as magnetic pretreatment; exposing said magnetically treated enzyme-substrate complex to a first temperature T.sub.1 for a first time t.sub.1; and initiating an anaerobe digestion.

2. The method according to claim 1 characterized in that the exposing said magnetically treated enzyme-substrate complex to a first temperature T.sub.1 for a first time t.sub.1 is followed by (i) providing an additive; (ii) mixing said enzyme-substrate complex with said additive to form a fermentation broth; and (iii) introducing said fermentation broth into a bioreactor to produce biogas, resulting in initiating an anaerobe digestion.

3. The method according to claim 2 characterized in that the additive is a sewage sludge.

4. The method according to claim 1 characterized in that a sonication pretreatment is performed before the mixing step.

5. The method according to claim 1 characterized in that said step of the exposing said magnetically treated enzyme-substrate complex to a first temperature T.sub.1 for a first time t.sub.1 comprises placing the enzyme-substrate complex in an incubator, wherein the time t.sub.1 is in a range of 10 to 56 h and/or the temperature T.sub.1 is between 35° C.-60° C.

6. The method according to claim 1 characterized in that said mixing step comprises: (i) providing an enzyme solution, wherein an enzyme in the form of a powder is mixed with ultrapure water; (ii) mixing the enzyme solution with the organic substrate to form the enzyme-substrate complex; wherein the organic substrate is ground and mixed with the enzyme solution by a magnetic stirrer for a time t.sub.2 and/or the enzyme is pectinase from Aspergillus niger.

7. The method according to claim 6 characterized in that the time t.sub.2 is in a range of 2-20 min.

8. The method according to claim 1 characterized in that the magnetic pretreatment comprises: (i) providing a magnetic field; and (ii) influencing the enzyme-substrate complex by the magnetic field for a time t.sub.3.

9. The method according to claim 8 characterized in that the magnetic field has a magnetic flux density of a range smaller than 1 mT and/or the time t.sub.3 is in a range of 2-6 h.

10. The method according to claim 4 characterized in that the sonication pretreatment comprises: (i) affecting the organic substrate by ultrasound; and (ii) cooling the organic substrate with iced water during the sonication pretreatment.

11. The method according to claim 1 characterized in that the organic substrate is sugar beet pulp.

12. The method according to claim 2 characterized in that the fermentation broth is operated for a time t.sub.4 at a mesophilic temperature T.sub.2 in the bioreactor and/or Calcium carbonate is dissolved as an additive in the fermentation broth.

13. The method according to claim 12 characterized in that the time t.sub.4 is in a range of 15-30 days and/or the temperature T.sub.2 is between 20° C.-45° C.

14. The method according to claim 1 characterized in that the bioreactor is a stainless-steel bioreactor and/or comprises a mixing system which is composed of two 45° pitched blade turbine and/or Sodium bicarbonate is added to the bioreactor prior to the production of biogas and/or Nitrogen is purged in the bioreactor for a time t.sub.5 prior to the production of biogas, wherein the time t.sub.5 is in a range of 20-40 min.

15. The method according to claim 1 characterized in that the sewage sludge is in anaerobic condition at temperature t.sub.6, wherein the temperature t.sub.6 is room temperature.

16. The method according to claim 1 wherein the time t.sub.1 is in a range of 24-48 h and/or the temperature T.sub.1 is between 45° C.-55° C.

17. The method according to claim 6 characterized in that the time t.sub.2 is 5-15 min.

18. The method according to claim 8 characterized in that the magnetic flux density is 0.2 mT and/or the time t.sub.3 is in a range 3-5 h.

19. The method according to claim 12 characterized in that the time t.sub.4 is in a range of 19-23 days and/or the temperature T.sub.2 is between 30° C.-39° C.

20. The method according to claim 1 characterized in that the time t.sub.5 is in a range of 25-35 min.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0093] FIG. 1 Diagram of accumulated biogas production in standard liters (comparison of different pretreatment methods)

[0094] FIG. 2 Diagram of accumulated methane production in standard liters (comparison of different pretreatment methods)

[0095] FIG. 3 Diagram of specific energy gain for batch experiments

DETAILED DESCRIPTION OF THE FIGURES

[0096] FIG. 1 illustrates a diagram of accumulated biogas production in standard liters, comparing substrates with different pretreatment methods. (Error bars calculated from the duplicate of various pretreatments and the control batch [21 days; 37.1° C.])

[0097] The different comparison variants are designated as follows in FIG. 1:

TABLE-US-00001 Pretreatment Nomenclature Enzyme E Magnetic field MF Enzyme + Magnetic field E-MF Ultrasound + Enzyme US-E Ultrasound + Enzyme + Magnetic field US-E-MF

[0098] Biogas production presented a clear tendency in the batch tests (FIG. 1). The biogas production increases as more pretreatments are applied. The biogas volume increased by 26±4.4%, for the combination of three pretreatments (US-E-MF) in comparison to the control batch. Data analysis shows that a statistical test was performed and indicates that the pretreatments E-MF, US-E and US-E-MF presented statistical differences in comparison with the control, which was not the case for E and MF when applied alone. Analyzing all experiments involving enzymes, i.e., comparing the enzymatic pretreatment to its combination with MF, US and both together, E-MF and US-E-MF presented statistical difference, but for US-E the null hypothesis could not be rejected, i.e., there is no significant difference between the mean value of the enzymatic pretreatment batch (E) and the mean value of US-E.

[0099] FIG. 2 illustrates a diagram of accumulated methane production in standard liters, comparing substrates with different pretreatment methods. (Error bars calculated from the duplicate of various pretreatments and the control batch [21 days; 37.1° C.])

[0100] The conversion of 100% of the substrate COD (chemical oxygen demand) to methane, was calculated based on the assumption that, in standard conditions (0° C.; 1 atm) 1 g of COD yields 354 mL of methane.

TABLE-US-00002 TABLE 3 Maximum theoretical methane potential. Maximum COD.sub.batch theoretical COD.sub.measured [gCOD] potential [L.sub.CH4] SBP (220 g) 1.121 [gCOD/gVS.sub.SBP] 284.02 100.54 SS (11 L) 40 [mg/mL] 4.4 1.5 Σ 288.42 102.1

[0101] The different comparison variants are designated as follows in FIG. 2:

TABLE-US-00003 Pretreatment Nomenclature Enzyme E Magnetic field MF Enzyme + Magnetic field E-MF Ultrasound + Enzyme US-E Ultrasound + Enzyme + Magnetic field US-E-MF

[0102] The methane production also increased in comparison to the control batch. Methane production from the combination of three pretreatments (US-E-MF) was 79±3.2% (244.6 NL/kgVS) greater than the control batch measurement, followed by E-MF (62±5.08%) (221.7 NL/kgVS) (FIG. 2). The control batch yielded 136 NL/kgVS; the enzymatic pretreatment (E) yielded 171.1 NL/kgVS; MF (180.7 NL/kgVS); and US-E (210.1 NL/kgVS). Data analysis for methane production followed a similar tendency compared to the biogas production. The pretreatments E-MF, US-E and US-E-MF presented significant difference in comparison with the control batch while MF and E did not. The pretreatments with enzymes, i.e., comparing the enzymatic pretreatment to its combination with MF, US and both together, did not present significant differences, i.e., there is no significant difference between the enzymatic pretreatment and its variation with MF, US and both together.

[0103] FIG. 3 illustrate a diagram of specific energy gain for batch experiments

[0104] The energy balance of the batch experiments compares the energy from the methane content produced by the pretreatment subtracted from the energy consumed to perform the same pretreatment. The energy net (FIG. 3) indicates that the magnetization of the enzyme-substrate mixture (E-MF) exhibit the greatest balance. The energy consumed to perform the E-MF pretreatment accounted for 0.15% of the energy produced for the same pretreatment, while its variation with sonication (US-E-MF) accounted for 27.53%. Hence, the method according to the invention is able to use a negligible energy input and achieve the high level of biogas/biomethane. The magnetic field pretreatment (MF) accounted for 0.19% of its energy production and the sonication pretreatment followed by enzymatic pretreatment (US-E) accounted for 31.89% of its energy production. In the present case, the application of sonication before E-MF increased biogas and methane production. However, sonication demands a higher energy input than the magnetic field facility resulting in a lower specific energy gain.