Improving Methane Production through Co-Digestion of Canola Straw and Buffalo Dung by H 2 O 2 Pretreatment

In this study an effect of acidic pretreatment on the CS (Canola Straw) and BD (Buffalo Dung) by anaerobic co-digestion was investigated. H2O2 (Hydrogen Peroxide) is a mainly accustomed reagent, used as a bleaching agent in the different industries such as paper and wood. In the present study, it was used as a pretreatment chemical at varying concentrations in batch reactors. The co-digestion of CS and BD was carried out in SAMPTS (Semi-Automatic Methane Potential Test System) at mesophilic (37±1oC) conditions. The CS was pretreated in glass bottles with different concentrations of the H2O2 for seven days. The inoculum used in the present study was an effluent of the CSTR (Continuous Stirred Tank Reactor), which was treating BD at mesophilic conditions. The specific methane production from the codigestion of canola straw and BD, by the pretreatment of H2O2 at concentrations of 0.5, 1.0, and 1.5% were 530.8, 544.5, and 510.3 NmL CH4 g/VS, respectively. The significant reduction in the volatile solids of CS was observed at the optimum pretreatment of 1.0% H2O2.


INTRODUCTION
including the crop residues.In order to improve the potential process, the digester use the co-digestion process by adding them two or more types of feedstock.
The animal waste (BD) and crop residue using as codigestion for renewable energy has tremendous advantages such as greenhouse neutral fuel, alternative of fossil fuels, and applicable for cooking, heating and generation of electricity.Moreover, it represents a feasible and effective waste-stabilization method to convert the undiluted solid bio-waste into nutrient rich organic fertilizer [5].An important cause for the two or more digestion to substrate is the adjustment of C/N (Carbon A D (Anaerobic Digestion) process plays a significant role in the degradation of the organic material in absence of oxygen.
The biogas includes a variety of gases, from them predominantly methane and carbon dioxide takes leading position and among the few trace gases [3].The AD process generally describes as four stages, namely hydrolysis, acidogenesis, acetogenesis and lastly methanagesis [4].Initially, the AD technology was started for sewage sludge and animal waste.Later on it is being used for treating the variety of the organic materials to Nitrogen) ratio [6].Animal manure, especially BD is a low-cost substrate having various carbohydrates, a very good ratio of C/N, excellent microbial flora, and become a useful source of biogas [7].The C/N of BD is reasonable as compared to crop residues, while the co-digestion stabilize the C/N ratio and thus reduces the threat of ammonia inhibition [1].Generally, crops are lignocellulosic substance and composed of three dissimilar polymers such as lignin, cellulose and hemicellulose as shown in Fig. 1.
The lignin is very difficult to degrade in the AD process.
It is a shield to protect cellulose and hemicellulose, and thus improves the mechanical strength of cell wall [9].
The lignin present in the organic material can be breakdown by using different pretreatments.
Pretreatments may be physical, chemical, thermal, biological or the combination of more than one [10].The H 2 O 2 is an acidic reagent used as bleaching agent in the different industries such as paper and wood.Numerous fact finders recently highlighted that acidic pretreatment, especially H 2 O 2 could be used as for the AD process because of its vigorous oxidizing ability [5].Beside this, H 2 O 2 is also cheap acidic chemical in comparison to H 2 SO 4 and HCl and can be used to improve the degradation of the organic process [11].
A number of researchers highlighted that the AD applied in a different range of temperatures from 5-60 o C. Generally three common names are as follows psychrophilic (<20 o C), mesophilic (>20 o C to >40 o C) and last thermophilic (>60 o C) [12].Most microbes are active in the last two categories of temperature ranges, and thus are important regarding the fermentation time period [13].The mesophilic temperature comes in ideal because of maximum biogas production, especially when the temperature is maintained around 37 o C [14].
Literature finds that the methane production from wheat straw, rice straw, corn straw and cotton stalks can be improved by using acidic and alkaline concentrations through pretreatments.Pakistan is an agricultural country and every year it generates different types of crop in huge amount it includes canola, rice, cotton, banana and wheat, etc.These crops produce bulk quantities of field residues annually.Most of the field residues are wasted.
One of the solution is to utilize these crop residues with animal dung as co-digestion substrate not to produce the energy, but also to overcome the environmental problems [15].

Raw Material and Inoculum
Fresh BD was collected near the Sindh University Railway Station, Jamshoro, and CS were obtained canola field from the Union Council Hatri, District Hyderabad.The size of

FIG. 1. STRUCTURE OF LIGNOCELLULOSE COMPLEX IN PLANT CELL WALLS [8]
Improving

Experimental Setup of Pretreatments
In order to get better methane potential from H 2 O 2 pretreatment, the different 0.5, 1.0 and 1.5% concentrations were used and the experiment was conducted according to Song et.al. [5].On the basis of the VS, the CS was kept in glass bottles with H 2 O 2 chemical for seven days for enhancing the methane production.After this the fresh buffalo dung was added in glass bottles without any pretreatment.To measure methane production, the SAMPTS was used which is lab experimental setup.

Preparation and Operation of Batch Test
The 500mL borosilicate glass working bottles were used as reactors and the BMP assays were prepared in duplicates, which was operated at the temperature of 37±1°C.All reactor bottles were load to 5g of VS, i.e.
mixture of CS and BD with 0.5, 1.0 and 1.5% respectively whereas last two were the control.The pH was adjusted to 7.0 ± 0.1 by neutralizing reagents and the inoculum 50mL was also add in co-digested reactors then all were filled up to 400mL of volume and were hermetically sealed with rubber stoppers [9].With the help of electric motors attached with mechanically bent stir rod the substrate were intermittently mixed set a speed of 70 rpm which run for 1 minute after every 30 minutes [17].Before start the batch, in each reactor bottle nitrogen was purged up to 5 minutes to remove oxygen and create the full anaerobic condition in all reactors [18].

Analysis and Calculations
The pH, MC (Moisture Content), TS (Total Solids), VS, TA (Total Alkalinity), and VFA (Volatile Fatty Acid) were determined according to the APHA (American Public Health Association) Standard Methods [5].The VFA determined by distillation, whereas the TA was titration methods respectively [1].The volume of methane produced from each digester was recorded daily and each batch experiment were performed 40 days.The entire setup of the SAMPTS is shown in Fig. 2.

Effect of Different Concentrations on Feedstock
The

FIG. 2. SEMI-AUTOMATIC METHANE POTENTIAL TEST SYSTEM (SAMPTS)
because of the accumulation of the ammonia [20].The alkalinity range of 1800-2000 mg CaCO 3 /L indicates the process of digestion is stable.When the ratio of VFA to TA is 0.5 then AD system is reliable, but if the ratio exceeds the limit of 0.5 it considered the indication of instability of digester [21].
At the end of 40 days of batch digestion, samples were analyzed for TA, VFA and pH.In these results pH samples were within the range except

Ultimate Cumulative Methane Production of H 2 O 2 Pretreatment
The ultimate cumulative methane production from the codigestion of CS along with the BD was 530.8, 544.544.5 NmLCH 4 /gVS than the other concentrations.These results were observed 68.9% more than from the results of Sahito, et.al. [8].Moreover, these results are higher than the results of Song, et.al. [18] for digesting the corn straw after pretreatment with the H 2 O 2 .The results of the present study are in agreement with Song, et.al, [5] and shows that on an increase the acidic doze, the pretreatment was harmful for methanogens in respect of toxicity.Thus, 1.0% H 2 O 2 was designated that the most suitable concentration of CS and BD for enhancing the methane production.optimal organic acid for the methanogen, which helps the growth of methanogen and resulted in an enhanced methane production [5].

Effect of Different Concentrations on VS Reduction
Methane yield can be obtained from the conversion of feedstock and mostly determined by reductions in the VS.In the present study, acidic pretreatment 56.67 and 57.53% VS reduction was acquired than the single control samples.This result was in agreement with findings of Song,et. al. [19].Moreover, the CS obtained a higher VS reduction than the control.The VS reductions in the CS and BD was calculated by using Equation (1).
In order to compare the eûectiveness of acid pretreatment, the efficiency of a pretreatment is not only based on the production of methane, but also based on the other parameters.The H 2 O 2 pretreatment was more effective and easier to use because of solubilizing in water and a less effort for the adjustment of the pH.It was also cheaper than the other acidic chemicals like H 2 SO 4 , HCl, etc.

CONCLUSIONS
In the present study, the concentration of H In order to improve the efficiency of AD, the effect of alkaline pretreatment at different concentrations may be carried out in future.
The prime aim of the present study was to improve methane production through co-digestion of CS and BD using co-digestion in mesophilic condition by anaerobically under batch experiments.In the present work, optimum CS to BD ratio on the basis of VS (Volatile Solids) (40:60) and optimum particle size of CS (4mm) was considered as an output from the previous study of Sahito, et.al.[9].
Methane Production through Co-Digestion of Canola Straw and Buffalo Dung by H 2 O 2 Pretreatment Mehran University Research Journal of Engineering & Technology, Volume 36, No. 1, January, 2017 [p-ISSN: 0254-7821, e-ISSN: 2413-7219] 195 CS was reduced up to 4mm by using hammer mill, which was fitted with the desired 4mm perforated plate.The prepared sample was kept in nylon bags at room temperature until use of pretreatment to BMP (Biochemical Methane Potential) test.In the present study, an effluent from CSTR treating BD was used as the inoculum.The CSTR was operating at 37±1 o C, whereas the initial pH of the inoculum was 7.0 ± 0.1.
main objective of the present study was to enhance the methane production and change the substrate's properties of co-digestion through pretreatments.After 40 days of batch digestion, the results of chemical analysis, i.e.MC, TS and VS were calculated as per standard methods on dry weight basis and are given in Table 1.CS was pretreated with different concentrations in H 2 O 2 similar to Song, et.al. [19].In AD reactor, the TA, pH and VFA are the main parameters for determination of inhibition.The role of TA is to avoid the pH variation, which decreases due to accumulation of VFA and increase

5 , and 510. 3
NmL on the pretreated of H 2 O 2 0.5, 1.0, and 1.5%, respectively.Besides, the control BD yields only 480.1 NmL as shown in Fig.3.In batch reactor, the methane generation was started from day one and was fluctuating due to the interaction of different phases of the AD Process.The H 2 O 2 pretreatment having 1.0% concentration resulted highest methane production, i.e.

2 O 2
was optimized for the maximum production of the methane from the co-digestion of CS and BD.CS, which was difficult to biodegrade by AD because of high lignin content, degrades well with the chemical pretreatment.The results yield that co-digestion pretreated with 1.0% H 2 O 2 generate the highest methane yield of 544.5 NmL CH 4 g/VS.

TABLE 1 . CHEMICAL ANALYSIS OF CO-DIGESTION AFTER PRETREATMENT (DRY BASIS)TABLE 2 . RESULTS OF TA AND VFA OF CO-DIGESTION AFTER PRETREATMENT Improving Methane Production through Co-Digestion of Canola Straw and Buffalo Dung by H 2 O 2 Pretreatment Mehran University Research Journal of Engineering & Technology, Volume 36, No. 1, January, 2017 [p-ISSN: 0254-7821, e-ISSN: 2413-7219] 197
Several pretreatment studies are available in the literature, which are related to different kinds of organic materials.