The Effect of Types of Organic Materials on the Production of Ethanol

Author: Allyson Wang

Peer Reviewer: Tanya Singh

Professional Reviewer: Levente Pap

Abstract

Currently, burning fossil fuels and their released greenhouse gases are contributing to global warming. Because fossil fuels are running out quickly, alternative energy sources such as biofuels are emerging because of their renewability and abundance. The purpose of this experiment was to observe the effects of different organic materials on the production of ethanol. It was hypothesized that if orange peels were fermented for eight days, then they would have the highest potential of producing ethanol. There was no control because there is no “typical” organic material. To start the experiment, the same amount of each organic material (orange peels, pistachio shells, cornstalk, and Switchgrass) was boiled for an hour. The four organic materials were each placed into twenty jars, and after fermenting for two, four, and eight days, refractometers are used to measure the refraction index/specific gravity. The results determined that orange peels had an average specific gravity of 1.011 on Day 8, higher than the values for pistachio shells, cornstalk, and Switchgrass: 1.002, 1.004, and 1.003 respectively. A t-test was performed which showed that all data was significant, rejecting the null hypotheses. The results did not support the research hypothesis (peels produced more ethanol on Day 4 than Day 8), but supported that orange peels overall produce more ethanol than other organic materials on Day 8. Because orange peels produced the most ethanol, it was found that the peels have a high content of cellulose which can be converted into ethanol. Further research can include longer boiling time and using a variety of other organic materials.

Introduction

Technology is advancing rapidly, and the world’s population is constantly growing. Worldwide, 78% of the energy comes from fossil fuels, 3% is from nuclear energy, and 19% is from renewable energy sources like biomass (Balan, 2014). The current energy source is dependent on fossil fuels like petroleum and coal which are nonrenewable and causing global warming with their greenhouse gases. Because of their high production of air pollution and countries’ increasing demand for oil, researchers and scientists around the world are looking for alternatives like renewable biomass fuels (Islam et al., 2015). 

Using biomass for fuels is a stable option because of its renewability, abundance, and benefits to society (Demiral et al., 2009). In addition, biofuels bring energy security to countries dependent on oil and increase job opportunities for fermentation specialists and scientists (Balan, 2014). These agricultural wastes can help the world by reducing greenhouse gases to slow global warming. It is predicted that by 2050, around 27% of the total transportation fuel consumption will be biofuels (Islam et al., 2015). Fuels are used to heat homes, for transportation, and other essential uses, making it a huge necessity (Demiral et al., 2009).

Organic material, also known as biomass, can be converted into energy sources and be used alternatively in industries. Biomass includes agricultural wastes like corn stalks and nutshells; wood materials such as sawdust and bark; aquatic plants and algae; municipal waste consisting of wastepaper and yard clippings; and energy crops like Switchgrass and willows. Biomass contains a complex pattern of molecules of mostly carbohydrates and lignin. The carbohydrates are primarily composed of cellulose, or hemicellulose fibers that strengthen the plant’s structure. The cellulose are homopolymers of glucose; this is what most living organisms use as a main source of sugar for biochemical energy.

Around 140 billion metric tons of biomass are produced every year. The combustion used to convert carbon dioxide into biomass is called the carbon cycle. Biomass also fixes carbon dioxide balance in the atmosphere using photosynthesis. Currently, 7% of energy comes from biomass each year. Biomass can potentially create 2.89 x 10⁴ exajoules of energy, around eight times the world’s energy consumption from all sources (Tao, 2002). 

Orange peels, pistachio shells, cornstalk, and Switchgrass are being thrown away in landfills as food and agricultural wastes, creating unwanted greenhouse gas emissions. Orange peels from Florida alone can generate an estimated 200 million gallons of ethanol annually (Casey, 2010). Fifteen point six million tons of orange peels globally could be used to make other beneficial materials like fuels. According to the Orange Peel Exploitation Company (OPEC), the cellulose in the orange peels can be made into biofuels (Oranges.com, n.d.). Orange peels can also produce large amounts of citric acid, suggesting its high content of cellulose (Torrado et al., 2011).

Pistachio shells are one of the world’s favorite nuts and, annually, more than 65,000 tons of pistachios are produced. Turkey has begun to use pistachio shells as fuel. Few studies have shown that there is cellulose in the shells (Demiral et al., 2009). Additionally, corn stalks are agricultural wastes, and it has been hypothesized that they contain cellulose to produce ethanol (Steil, 2013). Moreover, energy crops, specifically Switchgrass, are labeled as cellulosic biomass and will greatly increase in production in the next 30 years (400 to 700 million dry tons). Research has revealed that Switchgrass produces more ethanol than corn (Biello, 2008).

Ethanol is inexpensive and easily produced by fermenting organic matter (Watts, 2012). Bio-ethanol is a biofuel used mainly as a substitute for gasoline as well as for transportation and heaters (Markov, 2012a). Edible foods produce first generation bio-ethanol which contains high sugar content and can be easily converted into fuel. Because first generation feedstock comes from edible foods; however, it could come into competition with food industries, land, and water. Second generation biofuels are based on non-edible lignocellulosic biomass like agricultural and municipal wastes. The residues contain high sugars of polysaccharides which can be processed into second-generation biofuels. Some major advantages of the non-edible feedstock include its low cost, high availability, and is noncompetitive with land, water, and food sources (Islam et al., 2015).

To obtain fuels, pretreatment is performed where the sugars are extracted from the materials. Before pretreatment, the lignin encloses and organizes the cellulose within the cell. After the material undergoes high temperature and pressures, the lignin in the cells ruptures and scatters the sugars inside (Liu & Fei, 2013). The biomass sources then convert into fuels under the processes of fermentation, pyrolysis, or chemical modification. Industrial fermentation is the most efficient and popular way biofuels are produced by sugars. The sugar is extracted by enzymes, and the yeast cells convert the sugar into ethanol and carbon dioxide (C₆H₂OH ? 2C₂H₅OH + 2CO₂). The ethanol is then separated from fermentation using distillation (Markov, 2012b).

This experiment will determine if different durations of fermentation and organic materials will affect the amount of ethanol produced and their potential to convert into biofuels. The independent variables in this experiment are different organic materials: orange peels, pistachio shells, cornstalk, and Switchgrass; and different durations of fermentation of two days, four days, and eight days. There is no control because there is no typical organic material. The dependent variable is the production of ethanol which is determined by the specific gravity (no unit). Based on previous studies and research, it is held that if orange peels were fermented for eight days, then it would produce the most ethanol. In a previous experiment, it was shown that orange peels produced high amounts of citric acid from its high cellulose content. Because it contains lots of cellulose, there is more sugar to ferment which potentially means that peels could produce lots of ethanol (Torrado et al., 2011). 

EDD

Title: The Effects of Different Organic Materials on the Production of Ethanol

Hypothesis: If orange peels are fermented for 8 days, then they would have the highest potential of producing ethanol.

Durations of Fermentation: 2, 4, and 8 days

Independent Variable: Organic Materials
Orange Peels	Cornstalk	Switchgrass	Pistachio Shells
20	20	20	20

Dependent Variable: Specific Gravity (no unit) (production of ethanol)

Constants: type of environment (lab temperature), type of water added to cooking pot, amount of grinded material (400 grams), same boiling time (1 hour), type of cooking pot, amount of pressure/boiling temperature, timer, type of jar, type of refractometer, type and amount of yeast, pipette brand

Methods and Materials

Four hundred grams of each organic material (orange peels, pistachio shells, cornstalk, and Switchgrass) were gathered and measured using a gram balance scale. The materials were then crushed, blended, and cut into small pieces. One of the organic materials was separated into one high pressure cooking pot filled with three liters of water. The material was boiled at high pressure for one hour. After an hour, the liquid in the pot was strained to separate from the solid matter. They were cooled down to room temperature (23 degrees Celsius), and measured using a thermometer. A measuring cup was then used to pour 200 milliliters of the boiled liquid in each of the twenty 568 mL (1-pint) jars. Next, 20 grams of the boiled material and five grams of yeast were distributed into each jar. The jars were then sealed with lids and set aside to be fermented at room temperature. The same procedure was repeated for each of the organic materials: orange peels, pistachio shells, cornstalk, and Switchgrass. On days 2, 4, and 8, the specific gravity was measured for all IV levels with a refractometer. A pipette was used to place three drops of the fermented solution on the refractometer slide. White paper towels were used to clean the refractometer. After the data was collected, the supervisor disposed the homemade alcohol by using a 500 mL beaker and cloth to separate the liquid and solid matter. The solid matter was placed in an autoclave bag for safety purposes while the liquid was poured down the drain. The pots and jars were rinsed thoroughly. Additionally, a fire extinguisher was kept in the room in case of a fire from boiling materials, and an apron and gloves were used for safety. A permission form was signed by a parent that indicated that they had read and understood the risks and possible dangers involved in the research and they consented to their child participating in this research.

Results

The effects of different organic materials on the production of ethanol was observed, and the results are shown in Tables 1, 2, 3, 4, 5 and Graph 1 and 2. It was hypothesized that if the orange peels were fermented for eight days, then they would have the greatest potential of producing ethanol. The means were calculated for each of the independent variables. The central tendencies between orange peels (1.011) and pistachio shells (1.002) shows that orange peels have a higher density than pistachio shells, meaning that the peels contain more cellulose that can be made into ethanol and the shells contain the least. The means for pistachio shells (1.002), cornstalk (1.004), and Switchgrass (1.003) were low and remained consistent at all three intervals, which supports that the three materials have very low density, and do not contain as much cellulose compared to orange peels. This also indicates that if the materials were to be fermented for longer than eight days, the production of ethanol would remain consistent. If orange peels were fermented for a longer duration, the data may vary according to the results which can be tested in additional experiments.

From these results, the data supported the research hypothesis because orange peels had the most amount of cellulose which leads to their high production of ethanol. However, orange peels produced more cellulose on Day 4 compared to Day 8. The variance and standard deviation were determined for each independent variable. Overall, the standard deviations were very low, meaning that the raw data collected for all levels were very clustered and precise. There were outliers for pistachio shells (1.004) since it was outside the SD 2 range (1.0006-1.0034), and there was an outlier for Switchgrass (1.004) that was outside the SD 2 range (1.0024-1.0036). These points could have been caused by error or other factors. Specify these factors.  

A t-test was done at a level of significance of 0.05 with the degrees of freedom of 38. The null hypotheses were that there would be no difference between each of the organic materials (orange peels, pistachio shells, cornstalk, and Switchgrass). All calculated t-values (32.863; 28.577; 34.268; 10.691; 5.822; and 8.305) were greater than the table t-value of 2.024. This implies that the null hypotheses were rejected, and there are significant differences between each organic material. The data collected for this experiment was most likely affected by the independent variables and not by chance. The probability of the results happening by chance is less than 0.05 based on the level of significance. The data for organic materials having an effect on how much ethanol they produce is significant.

Discussion and Conclusions

This experiment was to determine the effects of different organic materials (orange peels, pistachio shells, cornstalk, and Switchgrass) on the production of ethanol. It was hypothesized that if orange peels were fermented for eight days, then they would have the highest potential of producing ethanol. It was found that orange peels had the highest potential of producing ethanol at a specific gravity of 1.012 on Day 4 out of all organic materials. Based on the results, the research hypothesis was not supported, but the data did show that the orange peels produced the most ethanol (of 1.011) overall compared to other materials. A t-test was done for this experiment to observe if the data collected was significant. The data for all the organic materials was statistically significant which shows that the data was due to the independent variable, implying that different types of organic materials have an effect on the production of ethanol.

Other studies and research have shown that orange peels produce a large amount of ethanol and cellulose. According to an article, orange peels can produce almost 200 million gallons of ethanol every year (Casey, 2010). This reveals its high cellulose content which is also supported by a study on citric acid (Torrado et al., 2011). Another study shows that the OPEC have already started to convert orange peels into usable biofuel (Oranges.com, n.d.). A research team in Sweden has successfully produced ethanol from different materials and is diverting their attention towards orange peels (Meade, 2009). As a non-edible feedstock that produces a huge amount of ethanol, it provides many benefits to our society such as transportation fuel and heat for homes (Islam et al., 2015; Demiral et al., 2009).

Florida is taking a huge step towards using orange peels for ethanol. A professor at the University of Central Florida has been working on converting the peels for secondary fuel. Other scientists believe their findings and experiment may turn out satisfactory (Kotala, 2010). In addition, an energy ethanol plant in Florida is planning to convert peels into ethanol that can be sold to Floridians at gas stations (Meade, 2009). Meanwhile, another department in Florida who partnered with other companies are investigating the peels’ potential for ethanol production. The industry has been researching citric energy and performing basic steps in the laboratory (Dunford, 2008).

Overall, there was no significant difference between the data for different durations of fermentation. However, for orange peels, Day 4 had an increase of 0.001 from Day 2, implying that orange peels may produce more ethanol in shorter durations of fermentation. This data also may have been a misreading (specifically because of the minimal increase) since all other materials had a constant value for the three days. For pistachio shells, cornstalk, and Switchgrass, there were no differences between the durations of fermentation in specific gravity which explains that different durations of fermentation do not greatly affect the production of ethanol. 

Based on previous research, orange peels can be converted into biofuel under high temperature. The more cellulose there initially is, the more biofuel is created (Tao, 2002). This research supports Torrado’s study, stating that orange peels have a high cellulose content to produce a high amount of ethanol (Torrado et al., 2011). Studies still support that materials like pistachio shells, cornstalk, and Switchgrass are capable of producing ethanol, but it would take lots of heat and material in order to extract a large amount of ethanol (Tao, 2002). All the results were significant because the amount of ethanol for each organic material had a significant difference which rejects the null hypotheses. The independent variables affected the results which were statistically apparent.

In the experiment, there were a few sources of error. Longer boiling time and a larger amount of materials could be used in order to receive better and more accurate results.                                                    Additionally, more specific measurements of the measuring cup, refractometer, and thermometer could have been used in order for more precise data. When taking measurements for each ferment day, some gas may have leaked into the air which could have prevented the production of ethanol on Days 4 and 8 because of the introduction of oxygen. Also, the refractometer itself may have been the source of error. The standard instruments GC-FID or GC-MS monitor the fermentation and detect a more exact ethanol concentration. However, because the instrument was not available, a refractometer was used instead to track the ethanol concentration. For further experimentation, other organic materials could be tested to observe if they contain cellulose to produce ethanol. An additional experiment could be performed on orange peels specifically with different factors such as amount of peels, boiling time, and amount of water in order to expand the knowledge on this topic.

Literature Cited

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Non-Peer Reviewed

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