vol3_no.5

APEC Youth Scientist Journal Vol. 3

49

THE HIDDEN POWER OF TOFU

∗Avip Noor Yulian1, Yuda Setiabudi1

1SMA 2 Kudus, Jalan Ganesha, Kudus, Jawa Tengah, Indonesia

ABSTRACT

This research aimed to determine the potential of tofu waste into ethanol and biogas

production as non-food biofuels. Tofu waste is a byproduct of soybean processing to tofu. The

process of making ethanol from tofu waste is ferment glucose inside tofu waste by

Saccharomyces cerevisieae. Distillate it, and we can get the ethanol. Besides ethanol, tofu

waste also can be converted into biogas. The process to make biogas is using anaerobic

degradation method. The result of this research shows that ethanol and biogas from tofu

waste can be used as alternative energy. The application of ethanol is for additive to gasoline,

and also biogas can be used for heating, cooking, and produce electricity.

Key words : Pollution, Tofu Solid Waste, Tofu Liquid Waste, Ethanol, Biogas

1. INTRODUCTION

1.1. Background

The existence of tofu industries in Java especially Kudus always coupled by waste. This

waste that known as tofu waste become a problem to people arround these tofu industries.

Tofu waste devided into tofu solid and liquid waste. The people arround the industries

complain about its bad smell and also if their skin get contact with tofu waste, it will damage

their skin. Tofu waste itself included as a pollutant. Beside that, these industries do not take

care about their waste, so they just throw them to the river. It will cause damage for the river

∗ Correspondence to : Avip Noor Yulian ([email protected])


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itself. But in fact these wastes can be used for another thing. For example, we can use tofu

solid waste as food for our pet, and also we can use Rhizopus oligosporus to make Tempe

Gembus. Beside that, both of tofu solid and liquid waste also can be used as alternative

energy. However, many people do not know how to turn this waste into alternative energy.

1.2. Purpose of the Study

1. To change tofu solid waste into ethanol by fermentation and destillation process

and use it as additive to gasoline

2. To change tofu liquid waste into biogas by anaerobic degradation and utilize it for

daily needs

2. METHODOLOGY

2.1. Collecting Materials

2.1.1. Collecting Tofu Solid Waste

First, we need to collect tofu solid waste from tofu industry. This tofu solid waste is

residual from the process of squeezing soybean pulp. This waste has characteristic

that is quickly decay and cause bad smell if not treated quickly.

Figure 1. Tofu Solid Waste


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2.1.2. Collecting Tofu Liquid Waste

The way to collect tofu liquid waste is the same with collecting tofu solid waste. We

can get them from tofu industry. This waste also has characteristic that is cause bad

smell, although it is recently produced.

Figure 2. Tofu Liquid Waste

Preparing Tools and Materials

2.1.3. Materials to Make Ethanol

The main material that used in this research to make ethanol is solid waste of tofu

and yeast (saccharomyces cereviseae). Also additional important material is pure

water.

2.1.4. Tools to Make Ethanol

The tools needed in this research are :

1) 1 unit closed bucket. Bucket that used is a bucket that has diameter 30 cm and height

of 35 cm

2) Playdough to cover the cavity between the hose and bucket cap

3) Distillation tool


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4) Closed glass to keep ethanol

2.1.5. Materials to Make Biogas

The main material needed to make biogas from tofu is liquid waste of tofu. There is

no addition material in this point.

2.1.6. Tools to Make Biogas

Tools needed in this research are :

1) 6 unit digesters. 2 digesters with diameter of 2 meters, 4 digesters with diameter of

1,2 m

2) Plastic pipe

2.2. Steps of Research

2.2.1. Making Ethanol

The first thing we need to do is collecting tofu solid waste as the main material. And

here are the following steps to do :

1. Fermentation

a.Washing the tofu solid waste using clean and flow water.We do this to clean

the dirt and microbes that contained in tofu solid waste

b. Cooking tofu solid waste using a pan for about 30 minutes

c.Draining it until it is going to dry

d. Putting it together with saccharomyces cereviseae into the closed bucket and close

tightly using playdough. This is to avoid leakage of air inside the bucket

e.Waiting and observing it for 7 days

f. Taking out the waste from the fermentation

g. Squeezing it to get the liquid until the waste become dry

h. Pouring the liquid into distillation tool to begin the distillation process

2. Distillation


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a.Lighting on the fire using a stove heat the liquid

b. Checking termometer so the temperature is not more than 80o C (ethanol point

vapor)

c.Waiting and observing the process until getting the ethanol out from the distillation

process

d. Placing ethanol into closed glass and close tightly

e.

2.2.2. Making Biogas

The steps of making this biogas from tofu liquid waste are :

1. Preparing 6 digesters and construct them underground. Just like shown in the figure

below

Stove

tofu waste from tofu industry

Figure 3. Digester Structure for Biogas

2. Collecting tofu liquid waste into the collector

3. Letting the liquid waste flow from the first digester until the third one

4. When the liquid gets into the third digester, the liquid will automatically evaporate

and begin to produce biogas

3

2

1

4

5

6

Tofu Liquid Waste Collector


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5. The gas will go to the fourth digester until the sixth

6. Connecting the sixth digester with stove

3. RESULTS AND DISCUSSION

3.1. Content of Tofu Solid Waste

Based on research, if we look from its chemical composition, tofu waste can be used as

carbohydrate source. Tofu solid waste also can be utilized to get its starch, this starch is

similar to starch from sago flour or tapioka flour. Contents of tofu waste (100 gr) are

protein 34.9 grams, fat 18.1 grams, carbohydrate 34.8 grams, calcium 227 mg, phosphor

585 mg, iron 8 mg, vitamin A 110 SI, vitamin B1 1.07 mg and water 7.5 grams. Based

on this data, tofu waste has content that can be used as alternative energy that is ethanol.

3.2. Process of Ethanol

Ethanol obtained from glucose inside tofu solid waste, then the glucose converted into

ethanol using microorganisms Saccharomyces cereviseae. Reaction is shown below :

(C6H10O5) + H2O C6H12O6

Starch Glucose

C6H12O6 2 C2H5OH + 2 CO2

Glucose Ethanol

During the fermentation process, the bucket must be sealed to prevent contamination and

maintain Saccharomyces to work optimally. Fermentation lasts in anaerobic conditions or

do not require oxygen at a temperature of 28° – 32° C.

The most optimal time for fementation process is 7 days, because it produces the biggest

yield than 5 days fermentation, that is about 10 % of volume. Meanwhile on 5th day,


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produced ethanol content is not maximized because of the growth of yeast

Saccharomyces cerevisiae isn’t optimal, so there are many substrates that have not been

fermented. After researched, if we use 1 kg of tofu solid waste fermented, it will produce

500 ml liquid of ethanol and water. And then after 8 hours of distillation process, we

could get that ethanol produced is about 2 ml.

Average octane value of this ethanol is about 118. As with ethanol in general, it can be

used as an additive to gasoline. In Indonesia, the octane value for gasoline is 88. With the

addition of 20% ethanol with 80 gasoline will be produced gasoline that have a high

octane. Mathematical calculation is shown below :

3.3 Results of Biogas

The amount of biogas produced from anaerobic degradation process of tofu liquid waste

can be estimated from the data of the value of COD and levels of degradation. Each kg of

COD degraded in anaerobic conditions to produce as much as 0.39 m3 CH4 at temperature of

35o C. Based on results of the research, known that the burden of the liquid waste of the

tofu industry is around 110 g COD/kg the soybean.

In the process of the tofu production, every time 1 kg the soybean that processed will be

produced by the liquid waste with the burden 110 g COD. With the level of the

degradation 90% and the value of the conversion 0,39 m3 methane l kg COD degraded,

then will be produced about 0,063 m3 biogas or equal to 0,032 L diesel oil (diesel fuel).

Tofu industry with the capacity 100 kg the soybean / day can produce 4 m3 methane or 6

m3 biogas. This biogas has methane concentrations around 50%. Advanced waste

treatment technologies can produce biogas with 55–75% CH4.


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Biogas can be utilized for electricity production on sewage works, in a CHP gas engine,

where the waste heat from the engine is conveniently used for heating the digester,

cooking, space heating, water heating, and process heating. If compressed, it can replace

compressed natural gas for use in vehicles, where it can fuel an internal combustion

engine or fuel cells and is a much more effective displacer of carbon dioxide than the

normal use in on-site CHP plants.

4. CONCLUSION

Besides being used as food, tofu waste still can be converted into two kinds of alternative

energy, those are ethanol and biogas. Ethannol derived from tofu solid waste with octane

average of 118 can be used as and additive to gasoline, which gasoline octane in

Indonesia is 88. So, it will raise the octane value of gasoline. Then biogas derived from

tofu liquid waste processed with anaerobic degradation can be used for cooking, produce

electricity, heating and replace compressed natural gas for use in vehicles after

compressed.

5. ACKNOWLEDGEMENTS

I would like to say thanks to my mentor, Mr. Yuda Setiabudi and my teachers from SMA

2 Kudus who helped and gave me inspiration for this journal. I also appreciate Mrs.

Jenny Kaligis, Mr. Mahfud, Mrs. Nyoman and Mr. Dolly who guide me. And also my

parents who always support me.


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6. REFERENCES

1. Muhammad Romli, Suprihatin (2009) The Pollution Load of Tofu Industry and Analysis

of Alternative Management Strategy. Department of Agro industrial Technology, Faculty

of Agricultural Technology IPB

2. Suryanto (2006) Biogas Tofu Industry at Kampong Sumber Mulyo Kepek Wonosari

Gunung Kidul. C-BETech LPTP Yogyakarta

3. Trubus, 2nd of January 2007

4. La Ode M. Abdul Wahid. Pemanfaatan Bio-ethanol sebagai Bahan Bakar Kendaraan

Berbahan Bakar.

5. Ir. M. Lies Suprapti (2005) Teknologi Pengolahan Pangan Pembuatan Tahu. Kanisius

Yogyakarta

6. Sunardi. Influence of Fermentation Time on Ethanol Content in Ethanol Production from

Tofu Waste. Universitas Setia Budi, Surakarta

7. Tensiska, Marsetio (2007) The Influence of Type of Organic Solvent on the Antioxidant

Activity of Okara.

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