Study of Biogas Production Rate from Water Hyacinth by Hydrothermal Pretreatment with Buffalo Dung as a Starter

In this paper, the effects of hydrothermal pretreatment on biogas enhancement production rates from water hyacinth mixed with buffalo dung was investigated.The focus of the experiment was on thetime of hydrothermal pretreatment and the ratio of water hyacinth with buffalo dung. The hydrothermal pretreatedsubstrates were characterized by TDS, BOD and pH.The hydrothermal pretreatment of 60 minutes with the ratio of water hyacinth to buffalo dung 1:2 showed the highest biogas production rateat 7889 ml/day. However, the highest methane composition was 52.82% which resulted on the hydrothermal treatment of 30 minutes with equal ratio of water hyacinth and buffalo dung. Thus, the optimum of methane yield obtained at hydrothermal pretreatment for 30 minutes with equal ratio of water hyacinth to buffalo dung is 2856 ml/day.The hydrothermal pretreatment increases the rate production of biogas 102% and the methane yield51% relative to untreated water hyacinth.The ratio of water hyacinth and buffalo dung has a great impact on biogas productionrateand compositions for hydrothermal pretreated substrates.


Introduction
In the last few decades research on biomasshas become the trending topic due to the depletion of fossil fuel and its environmental issues.As a tropical country, Indonesia has a big opportunity to develop the biomass based fuel originate from waste agricultural cellulose as well as nonagricultural cellulose.Twocommon routes to exploit biomass for energy purpose are thermal and fermentation processes.The anaerobic digestion for producing biogas is one of the promise and simple way to harvest the renewable energy.The first generation process generates biogas from livestock dung.Next, second generation of biogas generated from cellulose plant also attracted since its abundant availability and low-cost raw materials.
One of water plant that becomes a problem on river is water hyacinth due to its fasted growing which implicate to theeutrophication.On the other hand, the major component of water hyacinth is cellulose which is the basic substrate for fermentation.Thus, water hyacinth has a high potency as a raw material for biogas fermentation due to its cellulose high content [1].However, water hyacinth containslignin which is a disadvantage of using water hyacinth in the biogas production.Pretreatment throughphysical and chemical routes are reported effectively breakdown the lignin [2,3,4].
According to Mosier et al. [5] pretreatment by steaming, the addition of lime and hydrothermal are some of the methods that can improve significantly the action of hydrolysis enzyme.The main effect is to dissolve hemicellulose and lignin structural which increases the probability of accessing the cellulose by hydrolysis enzyme.Walch et al. [6] showed that hydrothermal treatment can be applied to remove hemicellulose from lignocellulose material through combination of dissolution and auto hydrolysis effects on the temperature of 120 o C to 200 o C.The hydrothermal pretreatmentmake the differences in the size of the raw materials used in the fermentation process become homogeneous [7].This led to the exposed of the surface area and causes the cellulose more accessible to enzymes.
According to Ferrer [8] hydrothermal pretreatment at a temperature of 80 o C for 30 minutes rises the water hyacinth hydrolysis process by triggering dissolution of water hyacinth from 4 to 10-12%.It hasshown that the pretreatment by boiling and steaming make the Waste Technology, Vol.2(2), October 2014 -ISSN : 2338-6207 higheraccess for bacteria through enzymatic hydrolysis process of lignocellulosic biomass.As the result,the glucose as the hydrolysis product increased considerably.Thisglucose will then be used by bacteria and transformed into anacetic acid which has an important stepas a reactant for the production of biogas by methanogenic bacteria.Thus, an increase in the hydrolysis process will increase the activity of methanogenic bacteria and in turn will increase biogas production and methane.
Qiao [9] reported thatafter hydrothermal pretreatment 170 o C/h, biogas production from lignocellulosic biomass increased from 210 ml/g to 238 ml/g of raw material.Hydrothermal pretreated substrate had resulted into an increase of 9.2% in biogas production and 20 % in methane production compared to that of untreated wheat straw substrate [10].Another study suggested that the hydrothermal pretreated substrate had resulted into an increase of 225.6% in biogas production and 222% in methane production relative to untreated rice straw substrate [3].
Shankar et al. [1] stated that water hyacinth has no microbes essential to initiate the process of biogas production.Kalle&Menon [11] reported that buffalo dung mixture can be used as a substrate for biogas production.Each 1 g of fresh buffalo dung containing 104 bacteria from rumen fluid.El-AzeemHadi [12] showed that the production of biogas from buffalo dung ranged from 104.7 to 468.1 L/kg of total organic solids.
Hartono and Kurniawan [13] states that the maximum biogas production rate occurred in the digester with ratio composition of 75% rice straw and 25% buffalo dung with production rate 6.5 ml/h and methane concentration 59.6%.Putra [14] reported that the highest biogas production of buffalo dung occurs at of agitation 50 rpm with a volume of 120.8 ml cumulative biogas and methane 20.19 ml.The average flow rate is 0.31 cm 3 /h of biogas and 0.053 cm 3 /h of methane gas.Quantitative variation associated with biogas production ratio C/N, the concentration of organic solids, as well as the content of nitrogen and carbon compounds.The increase in C/N ratio led to a decrease in the anaerobic decomposition process.Increased maximum biogas production correlated with a decrease in the OTS and C/N ratio.Moorhead and Nordstedt) [15] have used a batch-type anaerobic digestion to produce biogas from water hyacinth on incubation temperature of 35 o C.
To the best of our knowledge the study of effects of hydrothermal pretreatment on the biogas production and methane from water hyacinth with a combination of buffalo dung has never been conducted.

Materials and Methods
The raw material of water hyacinth was taken from Ciujungwhile buffalo dung obtained from buffalo ranch in Gempol, Serang.All chemicals,K2Cr2O7, H2SO4, MnSO4, Na2S2O3, using here were pure analytically grade.The hydrothermal pretreatments were examined by using autoclave.This study of fermentationwere using anaerobic batch reactor 20 liter in size.During the fermentation process, the biochemical parameters total solid (TS), COD, BODwere analyzedby standard method (ASTM D6238 -98).Water hyacinth reduced by 6 mm Buffalo dung mixed with water with ratio 1 water hyacinth heated in an autoclave and boiled at selected temperature of 170 o C with variations of 30 minutes, 60 minutes and 90 minutes pretreatment.Then, water hyacinth removed from the autoclave and left open until it reaches room temperature.After reaching room temperature, water hyacinth mi with buffalo dung with ratio 1:2, 2:2 and 2: water hyacinth and buffalo dung was then inserted into the digester.This mixture was incubated temperature for the fermentation process measurement of the biogas production by using salt solution technique.The biogas compositions were analyzedby using gas chromatography type-8A).

The Effects of hydrothermal treatment rates
The hydrothermal pretreatment water hyacinth colorfromgreen to brown disappearance ofchlorophyll during boiling in autoclave.The BOD has surged hydrothermal treatment of 30 minutes 1549.8 (Table 1).However,further hydrothermal treated showed only a slightly difference.The revealed that the microbe have a larger cellulose which the substrate for biogas production.Substrates acidity of hydrothermal treated ranged within 7.9 -8.25.As the fermentation arose the

The Effects of substrates composition
It can be seen from Figure 2a that hyacinth and buffalo dung has no significant effects biogas production ratefor the water hyacinth hydrothermal pretreated.It means that the buffalo dung as The increasing of BOD that the microbe have a larger access to the cellulose which the substrate for biogas Substrates acidity of hydrothermal treated 8.25.As the fermentation arose the acidity was declining which by acidogenic bacteria.The biogas produced is affected by the acidity [16].
The results of the measurement of biogas production without hydrothermal treatment showed low production as in Figure 2. The structure of lignin remains intact thus the microbe has no access to cellulosic materials.This low production biogas for water hyacinth without hydrothermal pretreatment confirms t Ferrer et al (2010).The biogas rate was started to increase while the water hyacinth pretreated for 30 minutes.In addition, it achieved the peak on 60 minutes hydrothermal pretreated.However, the biog decreased after 60 minutes.It is shown that hydrothermal increase significantly the biogas production rates.This probably because of the bacteria activity to produce hydrolysis enzyme increases by the greater access to the cellulosic material after removing the lignin structure during the hydrothermal process [10,11]. of hydrothermal treatment time on the biogas rate

The Effects of substrates composition on biogas rate
that the ratio of water dung has no significant effects on the for the water hyacinth with no It means that the buffalo dung as a starter for the fermentation taken place was not effectively used by the anaerobic system access to the cellulosic material hyacinth and buffalo dung become important for the hydrothermal pretreated (figure b,c, 28 6207 acidity was declining which indicatedacetic acid produced The biogas produced is affected by measurement of biogas production without hydrothermal treatment showed low production as in Figure 2. The structure of lignin remains intact thus the microbe has no access to cellulosic materials.This low production biogas for water hyacinth without thermal pretreatment confirms the study obtained by al (2010).The biogas rate was started to increase while the water hyacinth pretreated for 30 minutes.In addition, it achieved the peak on 60 minutes hydrothermal pretreated.However, the biogas production rates slightly decreased after 60 minutes.It is shown that hydrothermal increase significantly the biogas production rates.This probably because of the bacteria activity to produce hydrolysis enzyme increases by the greater access to the llulosic material after removing the lignin structure during the hydrothermal process [10,11].on the biogas rate for ratio 1:2 a starter for the fermentation taken place was not used by the anaerobic system due to the lack of access to the cellulosic material.The ratio of water hyacinth and buffalo dung become important for the hydrothermal pretreated (figure b,c, and d).In fact, the ratio 1:2 shows the highest biogas productio especially for 60 minutes and 90 minutes pretreated.This is probably due to the number of bacteria for fermentation process which was increasing with the amount of buffalo dung in the digester.

The effects of hydrothermal on methane yield
Table 2 shows that hydrothermal pretreatment by 30 minutes increase the methane content from 29.6% up to

The effects of water hyacinth and buffalo dung on methane yield
As we can see from table 3, the substrates affected significantly to the biogas.The analysis showed that the highest methane gas found in hydrothermal treatment 30 minutes with a ratio of 2:2, namely 52.82% (Table 2).This percentage indicates that the quality biogas produced is a c , Yuhelsa Putra et al.
Waste Technology, Vol.2(2), October 2014 -ISSN : 2338-6207 ratio 1:2 shows the highest biogas production rates and 90 minutes hydrothermal This is probably due to the number of bacteria for fermentation process which was increasing with the methane yield Table 2 shows that hydrothermal pretreatment by 30 minutes increase the methane content from 29.6% up to 44.9%.However, the longer the hydrothermal pretreatment have a tendency to decrease the percentage of methane.As we can see from Table percentage of maximum biogas rate achieved at 60 minutes and ratio 1:2 is only 23.85%.Thus, the methane yield for the maximum biogas peak at ml/day.The high biogas production rate did not correspond with the methane yield.hydrothermal pretreatment a).0 minutes, b).30 minutes, c The effects of hydrothermal time on biogas composition

ffects of water hyacinth and buffalo dung ratio
, the composition of significantly to the composition of The analysis showed that the highest percentage of methane gas found in hydrothermal treatment 30 minutes 82% (Table 2).This biogas produced is high which can be used as a source of electrical.percentage as 21.37 % hydrothermal treatment 90 minutes with a ratio of 2: biogas rate for maximum composition reached at 52.89% is 5400 ml/day.Thus, the methane yield is 2856 ml/day.It can be concluded that the optimum of methane y obtained at hydrothermal pretreatment for 30 minutes and equal ratio of water hyacinth to buffalo dung.a source of electrical.The lowest as 21.37 % of methane was occurred in 0 minutes with a ratio of 2:1.The biogas rate for maximum composition reached at 52.89% is 5400 ml/day.Thus, the methane yield is 2856 ml/day.It can be concluded that the optimum of methane yield at hydrothermal pretreatment for 30 minutes and equal ratio of water hyacinth to buffalo dung.Waste Technology, Vol.2(2), October 2014 -ISSN : 2338-6207

Conclusions
The biogas production from hydrothermal pretreated water hyacinth mixed with buffalo dung was examined by a series of batch laboratory testing.The experiments revealed that the highest biogas production was 7889 ml which occurred on hydrothermal treatment of 60 minutes at a ratio of water hyacinth and buffalo dung 1:2.However, the highest methane percentage was 52.82% when the hydrothermal treatment of 30 minutes with the ratio of water hyacinth and buffalo dung 2:2.Thus, the optimum of methane yield obtained at hydrothermal pretreatment for 30 minutes and equal ratio of water hyacinth to buffalo dung is 2856 ml/day.The present study suggested that the hydrothermal pretreatment enhances the production of biogas from water hyacinth significantly.The ratio of water hyacinth and buffalo dung has a significant improvement on biogas production for hydrothermal pretreated substrates.

Figure 1 .
Figure 1.Experimental steps for biogas production with hydrothermal treatment

Table 1 .
Biochemical parameters before the fermentation process.

Table 3 .
The effects of ratio of substrate on biogas compositions