MITOR: Jurnal Teknik Elektro Study on the Utilization of Banana Stem and Rice Bran Waste as a Biogas Source for Electric Power Generation I Gusti Komang ApriadiO .
Jumiati Ilham.
Ade Irawaty Tolago.
Taufiq Ismail Yusuf Fakultas Teknik.
Program Teknik Elektro Oe Universitas Negeri Gorontalo Gorontalo.
Indonesia O komangapriadi441@gmail.
Abstract Oe The increasing amount of agricultural waste, especially banana stem and rice bran waste, causes environmental problems due to improper disposal and low utilization.
This study aims to overcome these problems by utilizing these two wastes as alternative raw materials in biogas production through an anaerobic fermentation process for 25 days.
Three variations of substrates were used, namely 100% banana stem, 100% rice bran, and a 50:50 mixture.
The parameters observed included methane gas (CH4 ) content, pH, temperature, biogas pressure, flame quality, and electrical energy The results showed that the 50:50 mixture produced the highest methane content of 101.
07 ppm, a maximum pressure of 104,266.
99 Pa, and a stable blue flame for 16 minutes 25 seconds.
The pH value was in the optimal range of 5Ae7.
1 with a mesophilic temperature of 30Ae36.
5 C.
The highest electrical energy produced reached 0.
112493 kWh.
These results demonstrate that the mixture of banana stem waste and rice bran is more efficient in producing biogas and has the potential to be an environmentally friendly renewable energy source.
Keywords Oe Biogas.
banana stem waste.
rice bran.
anaerobic fermentation.
electricity conversion.
I NTRODUCTION
banana stem waste producing around 30% of the total crop weight.
Similarly, rice production in 2023 will ENEWABLE energy has become a major focus in reach around 53.
98 million tons and 53.
14 million tons global efforts to reduce dependence on fossil fu- in 2024, with rice bran as a byproduct accounting for els and address climate change.
One form of renewable around 10% of the total weight of milled rice .
energy that has great potential is biogas.
Biogas is a Banana stems, which are usually discarded and gas produced from the anaerobic fermentation process left to rot in the field after harvesting the fruit, have a of organic matter by microorganisms .
According structure rich in cellulose and hemicellulose reaching to the latest report from the Ministry of Energy and 19Ae35% and 4.
9Ae18.
7% dry weight, as well as 3Ae9.
Mineral Resources (ESDM) in 2024, the amount of lignin content .
This structure is generally the raw biogas energy consumption in Indonesia reached 0.
70 material needed for biogas production.
Likewise, rice million BOE (Barrel Oil Equivalen.
from the total bran, which is usually used as animal feed, is a byconsumption of 1,237.
43 million BOE, indicating that product of the rice milling process, has a high nutrithere are still many opportunities that can be optimized tional content, including crude fiber of around 29.
in increasing the use of biogas energy .
which can also be further processed into biogas enIndonesia as an agricultural country produces var- ergy .
ious types of agricultural waste in large quantities, inBased on field conditions, this organic waste is cluding banana stem waste and rice bran every year.
usually left to rot or burned around the land along with Based on data from the Central Statistics Agency (BPS), leaf waste and other waste without proper management.
banana production in Indonesia will reach around 9.
34 If this waste is left to rot and burned, it will certainly million tons in 2023 and 9.
26 million tons in 2024, with produce greenhouse gas emissions such as carbon dioxide and methane.
Although methane itself is not a direct The manuscript was received on November 14, 2025, revised on Novem- threat to human health, its accumulation in the atmober 21, 2025, and published online on March 27, 2026.
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Copyright: A 2024 by the authors.
This work is licensed under a Creative Commons AttributionOeNonCommercial 4.
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floods, and infectious diseases.
Therefore, researchers are motivated to conduct research on the use of banana stem waste and rice bran as a source of biogas for power The aim is to reduce this waste and address the problems that arise.
Several previous researchers have reviewed research on the utilization of waste, both agricultural waste, livestock waste, and industrial by-product waste, which the author uses as a source of literature in this Research conducted by .
has reviewed the utilization of banana peel waste and water spinach for biogas using an anaerobic bioreactor, showing that the effect of a 2:1 variable ratio with banana peel waste substrate contains more gas with a total of 119,554 liters and a more homogeneous flame test.
Research .
examines the effect of adding liquid tofu waste and banana peel to cow dung from differences in biogas quality, showing that a mixture of cow dung and water produces 4 liters of biogas in 7 days with a methane content of 48.
Meanwhile, a mixture of cow dung, liquid tofu waste, banana peel waste, and water produces 4 liters of biogas in 4 days with a methane content of 67.
Likewise, research .
, which examines the effect of adding banana stem waste and rice straw on biogas production, shows that the best results according to observations for 7 daysAinamely the addition of 100 grams of rice straw and 100 grams of banana stems for 3 repetitionsAihave an average volume of 2143.
15 mm3 .
Research .
examines the utilization of water hyacinth biomass from Limboto Lake using a TAK reactor (Without Acidification with Cow Dung Biostarte.
and a TAB reactor (Without Acidification with Bakicot Intestine Biostarte.
as biogas producers, showing that the TAK reactor produces 50 mL of biogas while the TAB reactor also produces 50 mL of biogas.
Meanwhile, in the advanced stage with the addition of acid and the addition of 1:1 biostarter, the results obtained were 102 mL in the KS reactor (Cow Dun.
and 5 mL in the SD reactor (Substrate Without Addition of 1:1 Cow Dun.
Research .
, which examined the potential for electrical energy from biogas mixed with ketapang leaf waste and buffalo feces, found that the biogas produced from a mixture of non-starter materials was 0.
00465 m3 , while biogas with a starter was 0028 m3 .
The potential for electrical energy produced from non-starter biogas production was 0.
022 kWh and with a starter was 0.
013 kWh.
Biogas formation occurs through several stages, starting from hydrolysis, which is the breakdown of complex organic elements such as carbohydrates, proteins, and fats into simple molecules.
This is followed by acidogenesis and acetogenesis, which is the con- Emitor: Vol 26.
No 1: March 2026 version of simple molecules into organic acids, hydrogen, and CO2 .
then complex organic acids such as propionate and butyrate are converted into acetic acid as the main substrate for the next stage.
Then the final stage .
is the conversion of acetic acid into CH4 by methanogenic bacteria and CO2 which is formed due to the reaction of hydrogen with CO2 .
, .
This process is highly dependent on the balance of hydrolytic, acidogenic, and methanogenic bacteria, as well as optimum conditions such as a temperature of 25Ae35 C and a pH of 6.
8Ae7.
5 to maintain the stability of biogas production which generally contains 54Ae70% CH4 and 27Ae45% CO2 .
This research differs from previous studies that often use materials such as banana peels, straw, water hyacinth, tofu waste, or ketapang leaves without considering the balance of the mixture ratio of the materials Meanwhile, this study combines banana stem waste and rice bran, which are chemically complementary.
Banana stems are high in cellulose, while rice bran is rich in protein and fat, resulting in a more optimal fermentation substrate in producing methane gas (CH4 ).
In addition, this study uses Arduino-based MQ9 and MQ-135 digital gas sensors and a U-manometer to measure gas levels and pressure more accurately, which differs from previous studies that were still manual.
II.
R ESEARCH M ETHODS
This research used an experimental method and tool design with a descriptive quantitative approach.
The objectives of this study were to determine the methane gas value, pH value, and temperature produced from the biogas production process using banana stem waste and rice bran.
to determine the effect of HRT (Hydraulic Retention Tim.
on biogas pressure and flame test resulting from the anaerobic process.
and to determine the electrical energy that can be generated from the pressure of the fermented biogas.
This research was conducted in Tumbihe Village.
Kabila District.
Bone Bolango Regency.
Gorontalo Province.
The study period was from September 2024 to May 2025, from the design stage to the analysis of fermentation results.
Materials and Tools The main materials used in this study were finely chopped banana stem waste for easy decomposition, rice bran as organic material with high carbohydrate and protein content, starter in the form of cow dung mixed with EM4 as a source of methanogenic bacteria, and water which functions to dissolve organic materials and maintain fermentation humidity.
All materials were DOI:10.
23917/emitor.
obtained from the environment around the research location.
The tools used in this research included: a fixeddome type biogas digester made of fiberglass with a total capacity of 120 liters .
128 m3 ).
a U-manometer for measuring gas pressure produced in the digester.
MQ-9 and MQ-135 gas sensors connected to an Arduino Uno microcontroller for detecting CH4 .
CO, and CO2 .
a digital pH meter.
a digital thermometer.
digital scales.
a banana stem shredder.
and a gas storage balloon used to store gas before the flame quality test.
Reactor Design and Preparation The reactor was constructed from a 120 L fiberglass drum and equipped with three main valves: an inlet valve for feeding materials, an outlet valve for removing residue, and a gas valve for conveying gas to the storage balloon.
The reactor was also equipped with a chopper connected to the inlet, gas sensors, a U-shaped manometer, a digital pH meter, and a digital thermometer to monitor fermentation parameters in real time.
Preparation and Determination of Material Composition Data Collection The data collection process was carried out daily using the following procedures:
Gas content (CH4 .
CO2 .
CO) was measured using MQ-9 and MQ-135 sensors connected to an Arduino Uno microcontroller.
The measurement results were monitored through the Arduino IDE Serial Monitor.
Digester pressure was measured using a Umanometer by calculating the difference in water height (OI.
between the two columns, which was then converted into absolute pressure (Pabs ) in Pascal units.
The pH value was measured using a digital pH meter calibrated with standard buffer solutions .
H 4, 6, and .
Fermentation temperature (AC) was monitored using a digital thermometer mounted at the upper section of the digester.
The collected data were then analyzed to observe the relationship between fermentation parameters and to compare outcomes among the different material variations.
Data Analysis The operating volume of the digester was set to 60% of the total capacity .
128 m3 ).
Three material composi- The analysis was conducted descriptively and quantion variations were used as shown in Table 1.
titatively, focusing on the changes in each parameter during the fermentation process and on comparing reTable 1: Variations in Material Composition sults across treatments.
Methane Gas Analysis (CH4 ) Variation Banana Stem Rice Bran Starter .
ow manure EM.
CH4 data obtained from the sensors were analyzed to observe the pattern of daily gas concentration increase and to determine which substrate variation produced the highest methane levels.
The total material entering the digester was ap- 2.
pH and Temperature Analysis proximately 77 L, consisting of 20 kg of organic maThe pH and temperature values were examined terial, 52 L of water, and 5 kg of starter, using a ratio to determine the optimal fermentation phase for of 1:2 between organic material and water.
The banana each substrate and to assess process stability under stem waste was chopped using a shredder to accelerate mesophilic conditions .
Ae44AC).
the decomposition process.
Pressure Analysis and HRT Gas pressure measured from the U-manometer was converted into absolute pressure using the following Digester Filling and Fermentation Process After all ingredients were mixed homogeneously, the mixture was fed into the digester until it reached 60% Pabs = Patm AH2 O y g y OIh of total capacity.
Initial pH and temperature values were measured before sealing the digester to create 4.
Flame Test Analysis anaerobic conditions.
The fermentation process lasted The biogas flame test was carried out by igniting for 25 days (HRT = 25 day.
with daily monitoring the gas and observing the flame color and duration of the following parameters: fermentation temperature as indicators of gas quality.
According to .
, a (AC), substrate pH, gas pressure .
, and CH4 .
CO2 , blue flame indicates a higher CH4 content, while a and CO concentrations.
yellow flame indicates a higher CO2 concentration.
Emitor: Vol 26.
No 1: March 2026 Energy Conversion to Electrical from Biogas 37 ppm on day 25, with the highest daily increase of The potential electrical energy was calculated based 14.
8 ppm on day 24 and the largest decrease of -8.
on the volume of biogas produced during fermenta- ppm on day 7.
The 100% rice bran treatment produced tion using the following equation:
the highest methane content of 85.
01 ppm on day 23, with a daily increase of 10.
92 ppm on day 16 and a Eelect.
= V2 y Energy proportionality y gen .
decrease of -11.
23 ppm on day 7.
Before calculating electrical energy, the pressure .
n Pasca.
must first be converted into gas volume Pabs yVrg
V2 =
After the volume for each sample was obtained, the potential electrical energy could be determined using Equation .
Based on .
, the efficiency of converting biogas to electrical energy using a generator ranges between 0.
30Ae0.
40, or approximately 30Ae40% for small-scale biogas power plants.
R ESULTS AND D ISCUSSION
This research began with the design and manufacture of a biogas reactor equipped with a chopping machine and an Arduino-based gas measuring instrument using MQ-9.
MQ-135 sensors, and a U-manometer, as shown in Figure 1.
Figure 2: Development of Methane Gas (CH4 ) The 50%:50% mixture treatment produced the highest methane content overall, reaching 101.
07 ppm on day 25, with the largest daily increase of 9.
5 ppm on day 19 and the biggest decrease of -14.
72 ppm on The decrease in all treatments on day 7 occurred because gases collected on the previous day still contained oxygen, requiring venting to maintain anaerobic These results indicate that the combined substrate provides the highest and most stable methane production, in line with findings from .
, which state that substrate combinations increase fermentation efficiency and methane output.
Figure 1: Reactor equipped with a chopping machine and measuring instruments Methane Gas (CH4 ) Analysis Observations on methane gas (CH4 ) content during the fermentation process for three treatments .
% banana stems, 100% rice bran, and a 50%:50% mixtur.
showed significant variations in both total gas produced and the daily rate of increase.
The development of methane gas for each treatment is presented in Figure 2.
Based on Figure 2, the 100% banana stem treatment produced the highest methane concentration of pH Analysis of Each Sample pH analysis was carried out to determine the acidity or alkalinity of each sample throughout the fermentation pH is a critical parameter because it affects microorganism activity and the stability of fermentation.
The recorded pH values for 25 days are presented in Figure 3.
Based on Figure 3, initial pH values were slightly different across treatments: 6.
anana stem.
, 6.
ice bra.
, and 6.
During the first week, pH decreased due to organic acid formation by acidogenic bacteria.
The lowest pH occurred on day 7: 6.
for banana stems, 4.
79 for rice bran, and 4.
6 for the Following the acidogenesis phase, pH gradually increased until the end of fermentation .
, reaching 6.
anana stem.
, 7.
ice bra.
, and 7.
The rise in pH indicates the onset of the DOI:10.
23917/emitor.
within mesophilic conditions, with peak methane production occurring at 32.
9AC .
, 33.
4AC .
ice bra.
, and 34.
8AC .
anana stem.
Temperature variations were also influenced by environmental conditions surrounding the digester.
Pressure Analysis and HRT Biogas pressure was measured using a U-manometer and converted to Pascal (P.
units using:
Figure 3: pH Development of Each Substrate methanogenesis phase, where organic acids are converted into methane.
According to .
, the optimal pH for biogas production ranges from 6.
5Ae8.
0, while pH below 6.
5 may inhibit methanogenic activity.
This aligns with .
, which states that methane formation is most effective at pH 5.
5Ae8.
Thus, the pH conditions in all treatments were within the ideal range for effective methane Pabs = Patm AH2 O y g y OIh with the following definitions: where Pabs is the absolute pressure (N/m2 ).
AH2 O is the density of water .
0 kg/m3 ), g is the gravitational acceleration .
80665 m/s2 ).
OIh is the height difference of the water column .
, and Patm is the atmospheric pressure .
325 N/m2 ).
The calculated biogas pressure results for the three samples are shown in Figure 5.
Fermentation Temperature Analysis Temperature monitoring during the 25-day fermentation process was conducted using a digital thermometer installed in the digester.
The temperature development for each variation is shown in Figure 4.
Figure 5: Biogas Pressure Comparison (Pascal.
Figure 4: Temperature Development (AC) Based on Figure 4, the banana stem treatment recorded temperatures ranging from 30AC to 34.
8AC.
The rice bran treatment showed wider fluctuations from 30AC to 35.
5AC.
The mixture treatment showed the highest and most varied temperature range of 30AC to 5AC.
Research conducted by .
states that methane production occurs under mesophilic .
Ae44AC) and thermophilic .
Ae65AC) conditions, with most practical biogas systems operating in the mesophilic range.
In this study, temperatures for all treatments remained Based on Figure 5, biogas pressure increased with fermentation time (HRT).
The 50:50 mixture produced the highest pressure of 104266.
99 Pa on day 25, followed by rice bran .
66 P.
and banana stems .
54 P.
This pressure increase reflects the increased gas volume produced by methanogenic microbial activity.
The pressure drop on day 7 occurred because early-stage gas still contained oxygen, which was released to maintain anaerobic conditions.
Afterward, pressure continued to rise, reaching a peak at the end of fermentation.
The 50:50 mixture performed best due to nutrient balance that supported microbial growth.
These findings agree with .
, which stated that mixed substrates produce higher pressure and gas volume than single-material substrates.
Thus, the optimal HRT was achieved on day 25.
Flame Test Analysis Flame tests were used to determine biogas quality based on flame color and burning duration.
The flame test results for each sample are shown in Figure 6.
Emitor: Vol 26.
No 1: March 2026 IV.
Figure 6: Flame Test of Each Sample .
Banana Stem Waste .
Rice Bran .
Mixture .
Based on Figure 6, the banana stem biogas produced a flame lasting 8 minutes 34 seconds, blue in color but easily extinguished under high pressure, indicating that CO2 was still dominant.
Rice bran produced a flame lasting 8 minutes 56 seconds with a less blue color but more stable, influenced by gas humidity and mixed compositions.
The 50:50 mixture produced the best results with a bright blue flame lasting 16 minutes 25 seconds, indicating a higher CH4 content.
These results confirm that substrate combinations provide better methane composition and biogas quality.
C ONCLUSION
The 25-day fermentation process produced methane gas concentrations of 76.
37 ppm .
anana ste.
, 85.
ice bra.
, and 101.
07 ppm .
:50 mixtur.
decreased early and increased toward day 25, indicating optimal fermentation.
Temperatures stayed within 30ACAe36.
5AC .
esophilic zon.
with highest methane production at 32.
9ACAe34.
8AC.
The 50:50 mixture produced the highest biogas pressure .
995 P.
, the longest flame time .
minutes 25 second.
, and the most stable blue flame, indicating superior combustion quality.
Electrical energy production reached 0.
112493 kWh, higher than single-substrate samples.
Overall, the 50:50 mixture proved most effective, showing strong potential as an environmentally friendly renewable energy source.
The author expresses gratitude to all parties involved in this research, including supervisors, family, and colleagues who provided continuous support and assistance throughout the completion of this study.
ACKNOWLEDGMENT