Codigestion of Press Mud and Distillery Waste Water with Sugarcane

Bagasse for Enhanced Biogas Production

Michelle C. Almendrala

Ralph Carlo T. Evidente

, Jasmine Marjorie C. Legarde

, and Kristopher

Ray S. Pamintuan

1,2,*

School of Chemical, Biological, and Materials Engineering and Sciences, Mapua University, Muralla St., Intramuros,

Manila, Philippines 1002

Center for Renewable Bioenergy Research, Mapua University, Muralla St., Intramuros, Manila, Philippines 1002

Keywords: biogas, methane, anaerobic digestion, distillery wastewater, codigestion

Abstract. Anaerobic co-digestion was carried out at mesophilic condition (37°C) in 1-L media bottles with a working

volume of 800 mL consisting of different dilution ratio of distillery wastewater (DWW), press mud,

bagasse, and inoculum. Distillery waste water was diluted with tap water at two different ratios (2:3 and 3:2)

and in two sample bottles, micronutrients were added. Batch test results showed that press mud mixed with

diluted distillery wastewater with and without additional micronutrients gave the highest methane yield of

61.3% and 78.23% (v/v), respectively. Methane yield is affected by the sensitivity of microorganisms to pH

variations. In this study, optimum pH was found out to be 5.0 to maximize methane yield. COD/BOD ratio

was also evaluated and the optimum initial COD to BOD ratio of the sample that yields higher methane

yield ranged from 1.8 to 2.6 which indicate that it is amenable to biological treatment. Meanwhile, the

optimum C/N ratio is found to be in the range of 72:1 and 78:1. For the effect of dilution, higher methane

yield occurred at higher dilution ratio. Moreover, anaerobic co-digestion of organic sugar waste was more

favorable in biogas production compared to mono-digestion of a single biomass. Lastly, effect of

micronutrients to the digestion and heterotrophic plate count were evaluated in this study.

1 INTRODUCTION

Biogas, the gas produced when organic matter of

animal or plant ferments in an oxygen-free

environment, occurs naturally in swamps and

spontaneously in landfills containing organic waste.

It can also be induced artificially in digestion tanks

to treat sludge, industrial organic waste, and farm

waste (Igoni and Jha Zhao, 2008). Biogas primarily

consists of methane (CH

) and carbon dioxide

(CO

), with varying amounts of water, hydrogen

sulfide (H

S), oxygen gas, and other compounds.

Millions of cubic meters of methane in the form of

swamp gas or biogas are produced every year by the

decomposition of organic matter, from both animals

and plants. A growing concern nowadays is the

increasing amount of sludge produced from

wastewater treatment (Yan and Wolf, 2015). At this

time, the costs connected with sludge treatment and

disposal may account for up to 60% of total

operation cost of wastewater treatment. Treating

various organic wastes, anaerobic digestion is used

to transform organic substrates and wastes into

energy (biogas) and a stabilized fertilizer (digestate).

For anaerobic digestion (AD) to be economically

viable, a continuous supply of homogeneous

feedstock is required, which is not always possible

in some regions due to increased demand for waste

and varying waste composition. Consequently, there

is a need for feedstock co-digestion, in order to

avoid fluctuations in feedstock composition balance

and availability (Lindorfer, Ahring and Verstraete,

2003). The anaerobic co-treatment of organic

wastes, known as co-digestion, is not normally

found in sugar plants, although it is a common

practice with agro-industrial wastes (Mata-Alvarez

and Rajoka, 2014).

Several research studies have been conducted to

study the efficiency of the anaerobic digestion of

sugar waste mixture. In one experiment (Agrawal

and Barrington, 2016), the sample filter mud from

the sugar mill which had a dry matter content of 315

C. Almendrala, M., Carlo T. Evidente, R., Marjorie C. Legarde, J. and Ray S. Pamintuan, K.

Codigestion of Pressmud and Distillery Wastewater with Sugarcane Bagasse for Enhanced Biogas Production.

DOI: 10.5220/0008692000460051

In Proceedings of the International Conference on Future Environment Pollution and Prevention (ICFEPP 2019), pages 46-51

ISBN: 978-989-758-394-0

g per kg produced a methane content of 51.7% from

162.5 L of biogas sample. In the study conducted by

(Budde et al., 2014), the highest increase in methane

yield (up to 63%) compared to the untreated press

mud was found at a pre-treatment of 20 minutes in

liquid hot water. In the study about reaction

kinetics, about 160 mL of SMMW loadings with a

substrate concentration of 48.3 g COD/L were

carried out in a 1-L anaerobic digester wherein the

specific rate constant was observed to be decreasing

from 1.76 day-1 to 0.05 day-1 when the loading is

increased from 40 to 140 mL, indicating an

inhibition phenomenon (López González, Pereda

Reyes and Romero Romero, 2017). Hence, co-

digestion process is kinetically much faster than sole

press mud or distillery waste water digestion.

Different research studies have shown that

mixtures of agricultural, municipal and industrial

wastes can be digested successfully and efficiently

together. This is due to the directive of minimization

of landfill and calling for reuse and recycle of

various wastes by the new waste management

policies, and the eagerness for extraction energy

from waste including sewage wastewater to ease up

the dependence on energy from fossil fuels

(Chynoweth and Kim, 2009). However, no study in

the writings was found on co-digestion of press mud

with molasses-based distillery wastewater with

bagasse. No articles have studied the dilution of

distillery wastewater as co-substrate in anaerobic

digestion of pre-treated press-mud. Effect of

micronutrients and immobilization on methane yield

were not also discussed in several literatures.

The main objective of this study is to determine

the effects of co-digestion of hot alkali pre-treated

sugarcane press-mud and distillery wastewater

solution with bagasse on methane yield. The specific

objectives are: (1) to compare the methane yield of

diluted distillery wastewater co-digested with press-

mud to that of pure distillery wastewater, (2) to

determine the physico-chemical characteristics of

the final digestate (pH, TSS, COD, BOD, and its

microbial characteristics), and (3) to determine the

effect of added nutrients to anaerobic digestion. It is

hoped that the findings will contribute to the

understanding of the factors that affect the full

exploitation to produce high yield of biogas. It is

also intended that the findings will be used to

enhance large scale biogas production from co-

digestion of press mud, distillery waste water and

bagasse which in turn can be used to generate energy

for combined heat and power.

2 METHODOLOGY

2.1 Materials

Molasses-based distillery wastewater (DWW), press

mud, bagasse, and yeast were collected from Central

Azucarera de Tarlac, in San Miguel, Tarlac City,

Philippines. All reagents, which mostly served as the

micronutrients for the substrate, were obtained from

the Chemistry Laboratory Office of Mapua

University. Distilled water was used to dissolve

glucose, yeast, and micronutrients. Fresh cow

manure which was gathered from a farm in

YGGACC HAI Farms in San Pedro, Laguna,

Philippines served as the inoculum and was stored in

plastic bags. Cow manure was incubated in

anaerobic condition for one week before use.

2.2 Pre-treatment

The press mud was pre-treated by two-step

hydrolysis before mixing with the distillery

wastewater solution. For the experiment,

approximately 1108.8 g of press mud was soaked in

1.0 L of low concentration of alkali solution, 62.0

mEq of Ca(OH)

/L, for 15 hours. The alkali

hydrolysate was then heated up to the boiling point

for about 20 minutes, followed by the addition of

distillery wastewater solution (pre-heated to ~100)

and about 100 cm

of chopped sugarcane bagasse.

The mixture was allowed to cool below 50 before

adding the micronutrients solution containing

glucose (30 g/L), dry yeast (5 g/L), NH

Cl (2g/L),

(0.5 g/L), MgSO

O (0.3 g/L),

MnSO

O (0.02 g/L), FeSO

O (0.02 g/L),

NaCl (0.02 g/L), CuSO

O (0.02 g/L),

CoCl

O (0.02 g/L), and ZnSO

O (0.02 g/L).

2.3 Experimental Design

Anaerobic digestion batch experiments were

conducted in 1-L media bottles. All batches were

prepared using 300 mL of pre-treated press mud

mixed with 200 mL of distillery wastewater solution

and 100 cm

of bagasse. The control batch (A) was

prepared using pure distillery wastewater. Distillery

wastewater was diluted with tap water in 3:2 and 2:3

volume ratio for the batch experiments with and

without micronutrients. Macronutrients were added

in batches B and C: 30 g/L glucose and 5 g/L dry

Codigestion of Pressmud and Distillery Wastewater with Sugarcane Bagasse for Enhanced Biogas Production

yeast. In each batch, 200 cm

of cow manure was

added in the prepared media. Details of each batch

composition is shown in Table 2. To ensure

anaerobic condition, the system was purged with

nitrogen gas (Figure 1) for 15 minutes. For the gas

collection, a 2-L urine bag was connected to each

media bottle (Figure 1). All experiments were

carried out at room temperature for a digestion

period of 30 days.

2.4 Measurement of Physico-chemical

Properties of Digestate and Biogas

Table 1: Composition of experimental batches used

Batch

Distillery

wastewater

(mL)

Nutrients

added

Pre-

treated

press

mud

(mL)

A 200 0 Yes 300

B 120 80 Yes 300

C 80 120 Yes 300

D 120 80 No 300

E 80 120 No 300

Figure 1: Anaerobic digestion set-up

Table 2: Physico-chemical properties measured and

methods used

Parameter Method Units

Biochemical

Oxygen

Demand

5210 B. Azide

Modification Dil.

Technique

mg/L

Chemical

Oxygen

Demand

5220 B. Open

Reflux Method

mg/L

Total nitrogen

4550-N C. Kjeldahl

Method / 4500-NO3

D. Ion Selective

mg/L

Total organic

carbon

5310 C. UV-

Persulfate

mg/L

4500-H B.

Electrometric

Heterotrophic

plate count

9215 B. Plate

Method

CFU/mL

The initial and final values of physico-chemical

characteristics of each batch such as COD, BOD,

and pH values were determined. The methods used

for determination are shown in Table 2. The

methane richness of the biogas will be determined

according to the American Standard Test method

ASTM D2504-88(1998) using a gas chromatograph

thermal conductivity detector (GC-TCD). This was

conducted in an analytical laboratory of the

Department of Energy, Taguig City, Philippines.

3 RESULTS AND DISCUSSION

3.1 Biogas Analysis

Batch test results showed that press-mud mixed with

diluted distillery wastewater with and without

additional micronutrients gave the highest methane

yield of 61.3% and 78.23% (v/v), respectively

(Table 3).

Figure 2: Determined composition of produced biogas

The methane content determines the quality of

the biogas. Higher methane content in the biogas

allows the substrates to be used more efficiently,

thus more energy can be produced. Higher methane

content also implies that smaller digesters are

required, which ultimately results in reduced

investment costs. The methane content of the biogas

ranges between 52 and 82% according to past

studies(Radjaram and Saravanane, 2017). In this

study, the methane content of the biogas produced

was significantly lower, except for the two batches

with dilution ratio of 2:3 (distillery wastewater

diluted with tap water), as seen in Table 4. The

measured methane content ranged between 0.016%

ICFEPP 2019 - International conference on Future Environment Pollution and Prevention

(Batch B) and 78.23% (Batch E). A visualized

comparison is presented in Figure 2.

Table 3: Methane content of biogas obtained from

batch digesters

Batch Composition

Methane

content (wt%)

Pure Distillery Waste

Water (DWW)

3.45

Diluted DWW (3:2,

DWW:H

O) with nutrients

0.0160

Diluted DWW (2:3,

DWW:H

O) with nutrients

61.3

Diluted DWW (3:2,

DWW:H

1.36

Diluted DWW (2:3,

DWW:H

78.23

From Figure 2, it can be noticed that hydrogen

was detected in Batch C and Batch E with low yields

of 7.70 and 1.46 %v/v, respectively. Hydrogen

production was relatively low at mesophilic range

(30-40°C) but higher at thermophilic range (50-

55°C). The thermophilic condition reduces the

solubility of hydrogen and thereby alleviates

inhibition from hydrogen partial pressure (Radjaram

and Saravanane, 2017). Batches A, B and D have

higher composition in N

, indicating that lower

biodegradation occurred due to toxicity.

The AD of distillery wastewater alone is quite

challenging since it is considered as a sulfur-rich

substrate, and using these substrates results to

undesirable effects: (a) sulfate reducing bacteria

(SRB) outcompete methanogens for hydrogen and

acetate due to thermodynamic advantages, resulting

in sulfides and less methane production; (b) high

sulfide concentrations has a direct toxic effect on

certain anaerobic microorganisms; and (c) sulfide

production and metal-sulfide precipitation is known

as one of the most important processes limiting the

availability of trace metals for microbial uptake, thus

negatively affecting the efficiency and stability of

the AD process (Radjaram and Saravanane, 2017).

3.2 Substrate Analysis

3.2.1 Change in pH

The percent decrease in pH for all batches is shown

on Table 4. The pH of all samples decreased after

the AD process because the digestion produces

acetic and fatty acids which tend to lower the

substrate pH. Most microorganisms grow best under

neutral pH conditions, since other pH values may

adversely affect metabolism by altering the chemical

equilibrium of enzymatic reactions, or by actually

destroying the enzymes. The methanogenic group of

organisms is the most pH sensitive. Low pH or

extreme pH changes can cause the chain of

biological reactions in digestion to cease (Fisgativa,

Tremier and Dabert, 2016). Thus, the minimal pH

swing observed on batch E supported the discussion

and produced the highest methane content.

3.2.2 Change in BOD and COD

The values of initial and final BOD and COD are

shown on Table 5. Chemical oxygen demand (COD)

is considered the most important parameter for the

anaerobic digestion process. A possible reason for

the observed higher COD values of the digestate is

the performed alkaline pre-treatment which causes

hemicelluloses and parts of lignin to solubilize and

subsequently signify higher organic degradation

(Fisgativa, Tremier and Dabert, 2016). The results

showed that pre-treatment was more efficient with

respect to promoting hydrolysis and increasing COD

concentration. The highest COD solubilizations

were achieved in batch E, followed by batch C.

These two samples have produced higher methane

yields compared to the other samples. This points

out that solubilization is important as increasing the

soluble organic matter content of samples will

theoretically increase the easily biodegradable

content of the waste and thus will lead to an

improved performance of the anaerobic digestion

(AD) process. Overall, however, there is no clear

relationship between BOD, COD, percent change,

and even BOD/COD ratio to the methane content of

biogas produced and further studies are

recommended.

Table 4: Effect of pH change on CH4 richness

Batch Initial

Final

decrease

in pH

CH4

content

A 5.13 3.79 26.12% 3.45%

B 4.50 3.78 16.00% 0.0160%

C 4.97 3.78 23.94% 61.3%

D 4.80 3.85 19.79% 1.36%

E 5.11 4.55 10.96% 78.2%

According to past studies, the optimum initial

BOD to COD ratio of the sugar waste products

Codigestion of Pressmud and Distillery Wastewater with Sugarcane Bagasse for Enhanced Biogas Production

ranges from 0.38 to 0.56 which indicate that it is

amenable to biological treatment. From the results,

batches A, C, and E fit in the range and thus were

able to produce methane. The wastewater containing

high BOD, above 10,000 mg/L is generally

considered suitable for anaerobic treatment. The

chemical composition of the sugar waste products

mainly contains carbohydrates and some protein and

therefore it is suitable for anaerobic decomposition.

Based on the results of this study, the BOD value

decreases while COD increases during digestion.

To determine the effect of AD to the

biodegradability of the samples, evaluation of

BOD/COD ratio is necessary. All samples showed

decreased BOD/COD ratios after digestion. Batch E

has the lowest BOD/COD ratio, which in effect has

the highest methane yield, meaning it already

reached its peak state where biodegradation no

longer occurs.

Table 5. Effect of changes in COD and BOD on CH

richness

Batch

Initial

BOD

Final

BOD

Initial COD Final COD

Initial

BOD/COD

Final

BOD/COD

content

33779 11012 143416 112684 0.2355 0.09772 3.45%

34004 9612 28683 133172 1.1855 0.07217 0.0160%

33859 10992 63513 143416 0.5331 0.07664 61.3%

34004 11012 28683 133172 1.1855 0.08269 1.36%

33859 10992 63513 245856 0.5331 0.04470 78.2%

3.2.3. Change in Carbon-to-nitrogen (C/N)

Ratio

Nitrogen present in the feedstock has two benefits:

(a) it provides an essential element for synthesis of

amino acids, proteins and nucleic acids; and (b) it is

converted to ammonia which, as a weak base,

neutralizes the volatile acids produced by

fermentative bacteria, and thus helps maintain

neutral pH conditions essential for cell growth

(Radjaram and Saravanane, 2017). An

overabundance of nitrogen in the substrate (low C/N

ratio) can lead to excessive ammonia formation,

resulting in toxic effects. Thus, it is important that

the proper amount of nitrogen be in the feedstock, to

avoid either nutrient limitation (too little nitrogen) or

ammonia toxicity (too much nitrogen). The

composition of the organic matter added to a

digestion system has an important role on the growth

rate of the anaerobic bacteria and the production of

biogas. The obtained C/N ratios are shown in Table

6. It should be noted, however, that there is no clear

relationship between C/N ratios and methane content

of biogas.

Table 6: Effect of C/N ratios on methane content of

biogas

Batch C/N ratio CH

content

12.1362 3.45%

66.0087 0.016%

77.8372 61.3%

153.072 1.36%

72.3635 78.2%

For all the samples, bagasse and press mud were

used as co-substrates, while batches B and C have

added micronutrients. Batches C and E have a C/N

ratio of 78:1 and 72:1, respectively. Their methane

yields are 61.3% and 78.2%, respectively. Hence, in

this study, the optimum C/N ratio is found to be in

the range of 72:1 and 78:1. This shows that

anaerobes utilize carbon 72 or 78 times faster than

the nitrogen for optimum methane generation.

3.2.4 Changes in Microbial Community

All batches showed a final HPC of 57000 CFU/mL.

This shows that the concentration of microorganisms

does not directly correlate to methane generation.

The compounding of several factors aside from HPC

are the ones affecting the concentration of methane

in the biogas.

3.2.5. Effect of Micronutrient Addition

Micronutrients are trace elements that are necessary

to microbial nutrition. Deficiency of these elements

reduces the methane yield but becomes toxic when

used excessively. It is found that the addition of Mg,

Fe, Co and Zn is favorable in methane production.

Magnesium is recognized as a stimulator for single

cell production responsible in limiting the

aceticlastic activity loss of the process. Iron and zinc

are essential cofactors that act as regulators in the

methanogenesis phase of the digestion. Cobalt also

plays a significant role in the formation of methane

from acetate. Based on a previous study, adding

ICFEPP 2019 - International conference on Future Environment Pollution and Prevention

micronutrients will increase the yield of methane

production (Menon, Wang and Giannis, 2017).

In this study, twice the recommended amount of

micronutrients was used to test for its impact on

yield. Some might be adsorbed by the solid

components of press mud or may be entrapped in the

suspended particle of distillery wastewater. It is

found that doubling the concentration of these

micronutrients made the mixture toxic. Samples

without micronutrients (Batches A, C and E)

appeared to have higher methane yield compared to

samples that have excessive amounts of

micronutrients.

4 CONCLUSIONS

Overall, the main goal of this study which was to

determine the effects of co-digestion of press mud

and distillery waste water with the addition of

bagasse for enhanced biogas production was

achieved. Some important parameters were

evaluated such as pH, BOD, COD, total carbon, and

total nitrogen. Methane yield is affected by the

sensitivity of microorganisms to pH variations.

Optimum pH to have a higher methane yield has

been found out to be 5.0. Also, COD/BOD ratio was

evaluated and it was found out that the optimum

initial COD to BOD ratio of the sample that yields

higher methane yield ranged from 1.8 to 2.6 which

indicate that it is amenable to biological treatment.

Meanwhile, the optimum C/N ratio is found to be in

the range of 72:1 and 78:1 which indicates that

anaerobes utilize carbon 72 or 78 times faster than

the nitrogen. Lastly, although micronutrients are

necessary to microbial nutrition, this study shows

that toxicity will occur if the concentration goes

beyond the necessary.

REFERENCES

Agrawal, O. and Barrington, D. (2016) ‘Co-

digestion of industrial sludge with municipal solid

wastes in anaerobic simulated landfilling reactors’,

Process Biochemistry, 40(5), pp. 1871–1879.

Budde, J. et al. (2014) ‘Effects of thermobarical

pretreatment of cattle waste as feedstock for

anaerobic digestion’, Waste Management, 34(2), pp.

522–529.

Chynoweth, K. and Kim, H. (2009) ‘Fungal

diversity in composting process of pig manure and

mushroom cultural waste based on partial sequence

of large subunit rRNA’, Journal of Microbiology

and Biotechnology, 8, pp. 743–748.

Fisgativa, H., Tremier, A. and Dabert, P. (2016)

‘Characterizing the variability of food waste quality:

A need for efficient valorisation through anaerobic

digestion’, Waste Management, 50, pp. 264–274.

Igoni, J. and Jha Zhao, B. (2008) Enhancement

of Methane Production from Solid-state Anaerobic

Digestion of Yard Trimmings by Biological

Pretreatment. The Ohio State University.

Lindorfer, G., Ahring, B. and Verstraete, W.

(2003) ‘Pre-treatment technologies for enhanced

energy and material recovery of agricultural and

municipal organic wastes in anaerobic digestion’, in

Future of Biogas in Europe II, European Biogas

Workshop, pp. 79–85.

López González, L., Pereda Reyes, I. and

Romero Romero, O. (2017) ‘Anaerobic co-digestion

of sugarcane press mud with vinasse on methane

yield’, Waste Management, 68, pp. 139–145.

Mata-Alvarez and Rajoka, M. I. (2014)

‘Cellulolytic soil mycoflora of rice growing areas of

Punjab’, Biologia, 19, pp. 109–117.

Menon, A., Wang, J. and Giannis, A. (2017)

‘Optimization of micronutrient supplement for

enhancing biogas production from food waste in

two-phase thermophilic anaerobic digestion’, Waste

Management, 59, pp. 465–475.

Radjaram, B. and Saravanane, R. (2017)

‘Assessment of optimum dilution ratio for

biohydrogen production by anaerobic co-digestion

of press mud with sewage and water’, Bioresource

Technology, 102(3), pp. 2773–2780.

Yan, Y. and Wolf, R. (2015) ‘Microbial

biochemistry of methane-a study in contrasts. Part 1.

Methanogenesis’, International Review of

Biochemistry, 21.

Codigestion of Pressmud and Distillery Wastewater with Sugarcane Bagasse for Enhanced Biogas Production