Synergistic Biodegradation of Coal Combined with Corn Straw as a

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Efficiency and Sustainability

Synergistic Biodegradation of Coal Combined with Corn Straw as a Substrate to Methane and the Prospects for its Application Hongyu Guo, Zhiwei Dong, Xianbo Su, Sen Liu, Jianbo Jia, Hongfei Yu, and Daping Xia Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.8b01120 • Publication Date (Web): 04 Jun 2018 Downloaded from http://pubs.acs.org on June 4, 2018

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Synergistic Biodegradation of Coal Combined with Corn straw as a Substrate to Methane and the Prospects for its Application Hongyu Guo1,2,3, Zhiwei Dong1, Xianbo Su1,3, Sen Liu3, Jianbo Jia3, Hongfei Yu3, Daping Xia1,3*

Author Affiliations: 1

School of Energy Science and Engineering (Henan Polytechnic University), Jiaozuo

454000, China; 2

State Key Laboratory Cultivation Base for Gas Geology and Gas Control (Henan

Polytechnic University), Jiaozuo 454000, China; 3

Collaborative Innovation Center of Coalbed Methane and Shale Gas for Central Plains

Economic Region, Jiaozuo 454000, China; *Corresponding author. Tel: 0391-3987981; Email address: [email protected] Hongyu Guo: Email address: [email protected] Zhiwei Dong: Email address: [email protected] Xianbo Su: Email address: [email protected] Sen Liu: Email address: [email protected] Jianbo Jia: Email address: [email protected] Hongfei Yu: Email address: [email protected] Daping Xia: Email address: [email protected]

ACS Paragon Plus Environment

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ABSTRACT: Waste reuse energy generation are encouraged in many countries. A low H/C ratio in coal is a limiting factor that affects biomethanation. However, corn straw has better H/C ratio which is beneficial to methane production. A series of biological gas production experiments were carried out using lignite B, bituminous coal D, bituminous coal C and corn straw to study the effect of synergistic biodegradation of coal combined with corn straw into bio-methane. Methane production was used as an index to analyze the gas production characteristics of single coal, single corn straw and coal and corn straw. The results show that the optimum proportion of the conversion of lignite B and corn straw to bio-methane is 2:1, and the optimum proportion of the conversion of bituminous coal D, bituminous coal C and corn straw into bio-methane is 3:1, and corn straw has a significant enhancement effect on the biological gas production in this experiment. When lignite B, bituminous coal D and bituminous coal C are respectively mixed with corn straw, the highest methane production is 2.05 mmol/g, 2.69 mmol/g and 1.35 mmol/g, indicating that corn straw has different promotion effects on gas production for coals of different rank: bituminous coal D + corn straw > bituminous coal C + corn straw > lignite B + corn straw. The stage change of COD and pH was consistent with that of the total gas production under optimal proportion, and the complementary advantages or mutual inhibition of methanogens was one reason for the differences in gas production between coal combined with corn straw and single coal. Keywords: coal; corn straw; H/C ratio; bio-methane; synergistic biodegradation


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1. INTRODUCTION

Bio-methane is an important constituent of coalbed methane resources. The total amount of coalbed methane developed to date in the Powder River basin is far higher than the total amount of the total resource volume discovered during exploration1, which has drawn the attention of researchers to the importance of bio-methane resources. Researchers at home and abroad have done research on the factors that affect the production and genetic mechanisms of biogenic coalbed methane2-4. Methanogens degrade coal to bio-methane in two ways: the nutritional methylation (mainly to acetic acid) and reduction of carbon dioxide5. Both metabolic pathways involve hydrogen, which is necessary to produce hydrocarbons, but a low H/C ratio of coal is unfavorable for the production of coalbed methane6. However, some biomass resources such as corn straw have a higher H/C ratio7, so the conversion of coal and corn straw into bio-methane has been considered. Statistics indicate that approximately 731 million tons of straw is produced yearly8, and residual coal resources are enormous9, so the full utilization of such resources has become the focus of our research. The technology of combined utilization of coal and straw has been studied extensively at home and abroad10. The combustion and synergistic gasification of coal and straw are affected by many factors, such as temperature, the gasification agent, the ratio of coal to biomass, the mixing proportions, the type of biomass utilized, etc12. Seok-Pyo Yoon et al. conceived the conversion of coal and rice straw into clean bio-methane by microbial fermentation13, and this became a new research direction. Studies have shown extensive populations of methanogens in mine water14. The present study utilizes the parent bacterium to convert coal and corn straw into bio-methane, and the


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potential and advantage of biomethanation in synergetic biodegradation was observed. Engineering applications of this study involve filling the goaf with corn straw and converting the residual coal and corn straw into bio-methane to recycle waste and reduce emissions, and retard surface subsidence.

2. MATERIALS AND METHODS

Experimental samples. Lignite B was selected from Yimin mine in Inner Mongolia, bituminous coal D was selected from Qianqiu mine in Henan Province, bituminous coal C was selected from Quanling mine in Shanxi Province. The fresh lump coal samples (> 8 cm × 8 cm × 8 cm) were collected at the working face, and taken back to the laboratory after a strict sealing in the vacuum packing bag. Then the 2 cm external surface of the coal samples was stripped off in the anaerobic workstation, and corn straw used in this study. The ultimate and proximate analyses of the experimental samples are presented in Table 1. The ultimate analysis was performed by following the Standards ISO 17247-2013 and proximate analysis by following the ISO 17246-2010. Coal mine water was collected and sealed at 4 °C. The particle size of all coal samples was 100–150 mesh, while the corn straw was crushed through a 30 mesh screen.

Table 1. The ultimate and proximate analysis of the samples/% Sample

Mar

Mad

Aad

Vad

Ro.ran

C (dry)

H (dry)

N (dry)

Corn straw 34.53 10.88 10.92 60.78 / 47.05 6.05 0.10 Lignite B 32.76 7.46 10.71 35.08 0.23 75.67 4.76 1.05 Bituminous coal D 14.21 5.22 11.46 40.52 0.56 71.89 4.71 1.02 Bituminous coal C 7.75 2.33 3.33 32.15 0.74 71.13 4.90 0.40 M, moisture; V, volatile matter; A, ash yield; ad, air dry basis; ar, as received; Ro,ran, vitrinite random reflectance; C, carbon; H, hydrogen; N, nitrogen; S, sulfur


S (dry) 0.20 0.27 1.66 0.28

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Enrichment culture of methanogens. Enrichment culture of methanogens: One thousand milliliters of mine water was added to K2HPO4 0.4 g, MgCl2 2.0 g, KH2PO4 0.4 g, Yeast 1.0 g, NH4Cl 1.0 g, resazurin 0.001 g, Cysteine 0.5 g, Na2S 0.2 g, NaHCO3 0.2 g, sodium acetate 2.0 g, KCl 0.2 g, NaCl 2.0 g and 10 mL of trace element solution. Trace element solution: One thousand milliliters of distilled water was added to triglycolamic acid 1.5 g, MnSO4·2H2O 0.5 g, MgSO4·7H2O 3.0 g, FeSO4·7H2O 0.1 g, NaCl 1.0 g, CoCl2·6H2O 0.1 g, CaCl2·2H2O 0.1 g, CuSO4·5H2O 0.01 g, ZnSO4·7H2O 0.1 g, H3BO3 0.01 g, Alk(SO4)2 0.01 g, NiCl2·6H2O 0.02 g, and Na2MoO4 0.01 g. Experimental protocols. Coal and corn straw were mixed together under anaerobic conditions in a 250 mL glass bottle in different proportions (Table 2). At the same time, 200 mL of bacterial fluid enriched for 4 days was injected into the glass bottle, which was brimmed with nitrogen for two to three minutes and connected to a collecting gas bottle filled up with saturated sodium bicarbonate solution, and then the biogas production device was incubated at 35 °C after a strict sealing of Parafilm. The biogas production was measured by the expulsive volume of the saturated sodium bicarbonate solution from the collecting gas bottle. Methane was quantified using a gas chromatograph (Agilent 7890 GC; Agilent Technologies Inc., Santa Clara, CA, USA) equipped with a Carbonplot chromatographic column (60 m × 320 µm × 1.5 µm) and a 200 °C TCD detector. Injection was performed at a flow rate (Helium carrier) of 30 mL/min. Quantitative calculations were made on the basis of chromatogram peak areas by the internal normalization method that used the standard gas including nitrogen (22.10%), hydrogen (17.69%), methane (30.11%) and carbon dioxide (30.10%), which was made in ZeZhong Technologies Inc., Zhengzhou, Henan Province, China. The 0.5 mL injection volume was collected three times with a 1 mL airtight syringe to


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increase the accuracy of methane concentration. The study changed the unit from mL to mmol which is a more standard measurement of methane yield as shown in Equals (1) and (2) by Ideal Gas Law. According to the total biogas production (TBP/mL), coal weight (CW/g) and methane concentration (MC/%), the biogas production (BP/(mmol/g)) and methane production (MP) were calculated, respectively. The purpose of this study was to reuse the residual coal in the abandoned coal mine, however, corn straw was only an external substrate, the biogas production and methane production of unit coal were used as comparison indexes to characterize the synergistic biodegradation potential of coal and corn straw. Also Chemical Oxygen Demand (COD) content, pH and archaeal identification of medium solution were measured. ( ) × . × . × ⁄ × () ( ) × (%) × . × MP (mmol/g) = . × ⁄ × ()

BP (mmol/g) =

(1) (2)

(Absolute 0 °C is precisely equivalent to 273.15 K, so 35 °C is 308.15 K; the volume of any 1 mol ideal gas is about 22.4 L)

Table 2. The proportion of the different coal samples and corn straw Sample number

Coal type

Coal (g)

Corn straw (g)

Proportion of coal and corn straw

HMB-1 YMD-1 YMC-1 HMB-2 YMD-2 YMC-2 HMB-3 YMD-3 YMC-3

lignite B bituminous coal D bituminous coal C lignite B bituminous coal D bituminous coal C lignite B bituminous coal D bituminous coal C

4 4 4 6 6 6 8 8 8

2 2 2 2 2 2 2 2 2

2:1 2:1 2:1 3:1 3:1 3:1 4:1 4:1 4:1


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3. RESULTS AND DISCUSSION

Biogas production characteristics under different proportions. The proportion of the different coal samples and corn straw for the synergistic biodegradation simulation experiment was carried out. The gas production was recorded every 3 days, the experimental duration was 18 days, and the total gas production, gas components and concentration were recorded (Table 3).

Table 3. Test results of biogas production with different proportions of coal and corn straw Sample number

Biogas production /(mmol/g)

Methane concentration /%

Methane production /(mmol/g)


4.07 ± 0.2 1.80 ± 0.1 2.31 ± 0.1 2.58 ± 0.1 3.70 ± 0.2 2.26 ± 0.1 0.99 ± 0.1 1.93 ± 0.1 1.61 ± 0.1

50.32 ± 2.0 52.79 ± 2.0 52.79 ± 2.0 76.08 ± 4.0 72.67 ± 3.0 59.79 ± 2.0 41.05 ± 2.0 58.39 ± 2.0 47.61 ± 1.0

2.05 ± 0.2 0.95 ± 0.1 1.22 ± 0.1 1.96 ± 0.2 2.69 ± 0.3 1.35 ± 0.1 0.41 ± 0.1 1.13 ± 0.1 0.77 ± 0.1

Characteristics of total biogas production with different proportions of coal and corn straw. The peak of biogas production from lignite B and bituminous coal D appears on the 12th day with optimal proportions, and the biogas production of bituminous coal C is stable at various proportions (Figure 1). The cumulative biogas production of HMB-2 is 57.75% lower than that of HMB-1, while the magnitude of HMB-3 reduction is relatively large. The cumulative biogas production of HMB-3 is 160.61% lower than that of HMB-2. Compared


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with YMD-1, the cumulative biogas production of YMD-2 increases by 105.56%, and the cumulative biogas production of YMD-3 is between that of YMD-2 and YMD-1. The cumulative biogas production of YMC-1 and YMC-2 is greater than that of YMC-3, and the gas production characteristics of YMC-1 and YMC-2 are similar. On the whole, when the proportions of the coal and corn straw are the same, but the coal rank is different, the total biogas production and the optimal proportions are different; when the coal rank is same, but the proportions of the coal and corn straw are different, the biogas production is different.

Figure 1. Plot of total biogas production with different proportions of coal and corn straw (a) Lignite B from the Yimin mine; (b) Bituminous coal D from the Qianqiu mine; (c) Bituminous coal C from the Quanling mine


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The relationship between different proportions of coal and corn straw and biological methane. The synergistic effect of coal and corn straw in different proportions was characterized by CH4 production and concentration (Figure 2). The methane production of HMB-1 is the highest, and the CH4 production of HMB-3 is lower than that of HMB-2. Bituminous coal has the same characteristics in that all YMD-2 and YMC-2 are the highest. As the coal content increases, the methane concentration shows a trend of low-high-low. The optimum proportion for the conversion of lignite B and corn straw into bio-methane is 2:1, and the optimum proportion for the conversion of bituminous coal D and bituminous coal C and corn straw into bio-methane is 3:1.

Figure 2. The CH4 production and concentration of the differently ranked coals combined with corn straw (2:1, 3:1 or 4:1 is the proportion of coal and corn straw) (a) CH4 concentration; (b) CH4 production


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Characteristics of Synergistic Gas Production under Optimal Proportion. The experiment results of single coal and single corn straw gas production in the optimum proportion are showed in Table 4.

Table 4. Production of biogas from single coal and single corn straw Sample number

Sample type

Sample weight /(g)

Biogas production /(mmol)

JG HMB YMD YMC

corn straw lignite B bituminous coal D bituminous coal C

2 4 6 6

3.29 ± 0.1 4.04 ± 0.1 5.50 ± 0.1 1.94 ± 0.1


Methane production /(mmol)

45.31 ± 2.0 45.85 ± 2.0 53.71 ± 3.0 56.24 ± 3.0

1.49 ± 0.1 1.85 ± 0.1 2.95 ± 0.2 1.09 ± 0.1

The total biological methane production of coal combined with corn straw and the sum of single coal and single corn straw can be seen in Figure 3. The synergistic effect of coal and corn straw is clearly visible. Lignite B: the sum of HMB and JG was 3.34 mmol, which was 145.50% lower than that of HMB-1; Bituminous coal D: the sum of YMD and JG was 4.44 mmol, which was 263.51% lower than that of YMD-1; and Bituminous coal C: the sum of YMC and JG was 2.58 mmol, which was 213.95% lower than that of YMC-2. From the methane production effect of Fig. 3, the effect of corn straw on the methane production of different coal rank is different: bituminous coal D + corn straw > bituminous coal C + corn straw > lignite B + corn straw, which achieves the purpose of ‘1+1 bituminous coal C + corn straw > lignite B + corn straw. The changes of COD and pH were consistent with those of the total gas production. The results of the archaeal identification showed that the complementary advantages or mutual inhibition of methanogens was one reason for the differences in gas production between coal combined with corn straw and single coal. These findings has good prospects for application by filling the goaf with corn straw, which is converted to biological methane along with the residual coal by the indigenous bacteria. Meanwhile, technical problems such as the adequate anaerobic environment and the full contact of corn straw and residual coal of in situ biomethane production should be considered in the field studies.

ACKNOWLEDGMENTS This study was funded by the National Science Foundation of China (Grant no. 41472127, 41472129, 41502158 and 21646006), Program for Innovative Research Team in University of Ministry of Education of China (IRT_16R22), Shanxi Provincial Program for Tackling Key Problems of Coal-based Science and Technology (Grant no. MQ2014-01), Shanxi Province Joint Research Fund of Coalbed Methane (Grant no. 2013012004), and Scientific and


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Technological Research Projects of Henan Province (Grant no. 172102310717). Moreover, the authors are grateful to the editor and anonymous reviewers of this paper.

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Steckel, S.; Bhattacharyya. A.; Lykidis. A.; Overbeek, R.; Klenk, H. P.; Gunsalus, R. P.; Fritz, H. J.; Gottschalk, G. J. Mol. Microbiol. Biotechnol. 2002, 4(4), 453. (18) Ma, K.; Liu X. L.; Dong, X. Z. Int. J. Syst. Evol. Microbiol. 2005, 55, 325–329. (19) Ni, S. S.; Boone, D. R. Int. J. Syst. Bacteriol. 1991, 41(3), 410. (20) Parshina, S. N.; Ermakova, A. V.; Bomberg, M.; Detkova, E. N. Int. J. Syst. Evol. Microbiol. 2014, 64, 180–186. (21) Dridi, B.; Fardeau, M. L.; Ollivier, B.; Raoult, D.; Drancourt, M. Int. J. Syst. Evol. Micr. 2012, 62(8), 1902. (22) Bräuer, S. L.; Cadillo-Quiroz, H.; Ward, R. J.; Yavitt, J. B.; Zinderet, S. H. Int. J. Syst. Evol. Micr. 2011, 61(1), 45. (23) Demirel, B.; Scherer, P. Rev. Environ. Sci. Bio/Technol. 2008, 7(2), 173–190. (24) Karakashev, D.; Batstone, D. J.; Angelidaki, I. Appl. Environ. Microbiol. 2005, 71, 331.


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Table 1. The ultimate and proximate analysis of the samples/% Table 2. The proportion of the different coal samples and corn straw Table 3. Test results of biogas production with different proportions of coal and corn straw Table 4. Production of biogas from single coal and single corn straw Figure 1. Plot of total biogas production with different proportions of coal and corn straw (a) Lignite B from the Yimin mine; (b) Bituminous coal D from the Qianqiu mine; (c) Bituminous coal C from the Quanling mine Figure 2. The CH4 production and concentration of the differently ranked coals combined with corn straw (2:1, 3:1 or 4:1 is the proportion of coal and corn straw). (a) CH4 concentration; (b) CH4 production Figure 3. Characteristics of the synergistic gas production from coal combined with corn straw at optimal proportions Figure 4. The change characteristics of the solution at optimal proportion Figure 5. The archaeal content in the fermentation solution of samples Figure 6. Synergistic biogas production system of corn straw filled with residual coal into a coal mine goaf


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Table 1. The ultimate and proximate analysis of the samples/% Sample

Mar

Mad

Aad

Vad

Ro.ran

C (dry)

H (dry)

N (dry)

Corn straw 34.53 10.88 10.92 60.78 / 47.05 6.05 0.10 Lignite B 32.76 7.46 10.71 35.08 0.23 75.67 4.76 1.05 Bituminous coal D 14.21 5.22 11.46 40.52 0.56 71.89 4.71 1.02 Bituminous coal C 7.75 2.33 3.33 32.15 0.74 71.13 4.90 0.40 M, moisture; V, volatile matter; A, ash yield; ad, air dry basis; ar, as received; Ro,ran, vitrinite random reflectance; C, carbon; H, hydrogen; N, nitrogen; S, sulfur


S (dry) 0.20 0.27 1.66 0.28

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Table 2. The proportion of the different coal samples and corn straw Sample number

Coal type

Coal (g)

Corn straw (g)

Proportion of coal and corn straw


lignite B bituminous coal D bituminous coal C lignite B bituminous coal D bituminous coal C lignite B bituminous coal D bituminous coal C

4 4 4 6 6 6 8 8 8

2 2 2 2 2 2 2 2 2

2:1 2:1 2:1 3:1 3:1 3:1 4:1 4:1 4:1


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Table 3. Test results of biogas production with different proportions of coal and corn straw Sample number

Biogas production /(mmol/g)


Methane production /(mmol/g)


4.07  0.2 1.80  0.1 2.31  0.1 2.58  0.1 3.70  0.2 2.26  0.1 0.99  0.1 1.93  0.1 1.61  0.1

50.32  2.0 52.79  2.0 52.79  2.0 76.08  4.0 72.67  3.0 59.79  2.0 41.05  2.0 58.39  2.0 47.61  1.0

2.05  0.2 0.95  0.1 1.22  0.1 1.96  0.2 2.69  0.3 1.35  0.1 0.41  0.1 1.13  0.1 0.77  0.1


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Table 4. Production of biogas from single coal and single corn straw Sample number

Sample type

Sample weight /(g)

JG HMB YMD YMC

corn straw lignite B bituminous coal D bituminous coal C

2 4 6 6

Biogas production /(mmol) 3.29 4.04 5.50 1.94

0.1 0.1 0.1 0.1


Methane production /(mmol)

45.31 45.85 53.71 56.24

1.49 1.85 2.95 1.09


2.0 2.0 3.0 3.0

0.1 0.1 0.2 0.1

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Synergistic Biodegradation of Coal Combined with Corn Straw as a

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