**4. Biodiesel production from used cooking oils**

According to table 5, the catalyst with higher industrial scaling, economic cost, high yields and short reaction time, is the alternative of basic catalysis, using sodium hydroxide. Although soap can be formed using sodium hydroxide in the transesterification reaction, this occurs if the content of free fatty acids is greater than 1% and the type of oil collected from the hotel sector has a percentage of acidity of 0.54%, so it is not problem to use this type of catalyst for the biodiesel production.


Table 5. Comparison of alternatives for the biodiesel production.

Acidity (%) 0.56 Moisture 0.25 Viscosity at 37ºC (centistokes) 44.78 Iodine index (Cgl2/g) 108.22 Peroxide index (meq. Oxygen active/Kg of sample) 16.61 Unsaponifiable material (%) 1.70 Saponification index (mg KOH/g) 195.87 Ash (%) 0.030 Refractive index 25°C 1.4700 Density 15°C ( g/mL) 0.9216

Table 4. Characterization of cooking oil collected by the hotel sector (Source: Avalquímico

According to table 5, the catalyst with higher industrial scaling, economic cost, high yields and short reaction time, is the alternative of basic catalysis, using sodium hydroxide. Although soap can be formed using sodium hydroxide in the transesterification reaction, this occurs if the content of free fatty acids is greater than 1% and the type of oil collected from the hotel sector has a percentage of acidity of 0.54%, so it is not problem to use this

> Catalyst NaOH CaO H2SO4 Alcohol Methanol Methanol Methanol Scaling High Low Low Catalyst separation Low High Low

Cost Economic High Moderate Availability Medium Low Medium

Soap, pasty

Catalyst concentration (%w/w) Low Medium High Molar ratio alcohol/oil Medium Low High Temperature (°C) Low High Medium Yield High Low Medium

Environmental impact High Low High

Reaction time (hours) Low Low High Safety level High Low High

**SELECTION PARAMETERS Comparison of alternatives** 

**FEATURES OIL COLLECTED BY THE** 

**Alkaline Heterogeneous Acid** 

Glycerin Glycerin

**HOTEL SECTOR** 

**3.1.3.2 Chemical characteristics of the used oil** 

Ltda.2010)

Chemical characterization of the used oil, is presented in table 4

**4. Biodiesel production from used cooking oils** 

By-products formation Glycerin

Table 5. Comparison of alternatives for the biodiesel production.

type of catalyst for the biodiesel production.


To select the best alternative for the biodiesel production are defined three ranges for the operation conditions to be used in the transesterification reaction (table 6).

Table 6. Ranges established for the operation conditions of the transesterification reaction (Rojas & Torres. 2009. pp 18).

#### **4.1 Experimental design**

It is a key to make a design from which the most appropriate values for each of the design factors can be established. The selected factors were: molar ratio alcohol/oil, percentage of catalyst, temperature and washing agent, where the first three are design variables and the latter is a design condition. Before starting the design is important defines the ranges and levels for these factors, for this reason, we search the experimental phase in scientific articles related to the project (table 7).


Table 7. Ranges for the design factors

Based on the ranges set out in table 7, we provide that the factorial design appropriate for the process is the factorial design 2k, which can be solved by the technique of Yate contrasts which establish two levels for each of the design factors, these levels are high (+) and low (-) (see table 8)


Table 8. Levels for each design factor

For the molar ratio alcohol/oil is found a ratio of 6: 1 that is optimum for achieving high conversions, some articles display that lower ratio not is possible to reach a complete transesterification reaction. There are also good results with ratios ranging between 9:1 and 12:1, while if we use higher than 15:1 molar ratio there are difficulties in the separation of glycerin and methyl esters.

Biodiesel Production from Waste Cooking Oil 37

To determine that interactions are significant an f for each source of variation is calculated and compared to f0,05 (1,16) = 4,49, with this we can determine in which region (probable region RP or critical region RC) is each treatment and thus be able to establish that treatment

Table 10, shows the quantities determined at the laboratory level for each compound that is

**AMOUNT OF REAGENTS**  Waste cooking oil (mL) 150 Amount of methanol (6:1) (mL) 40.63 Amount of methanol (9:1) (mL) 60.95 Amount of NaOH grams (0.5%p/p) 0.823 Amount of NaOH grams (0.7%p/p) 1.105 Amount of HCl grams (0.5% p/p) 1.466 Amount of HCl grams (0.7% p/p) 2.053

First is the filtration of used oil, then mixing alcohol/catalyst to add it to the reactor which contains the oil at the temperature of the transesterification reaction, then is the separation of biodiesel and glycerin, washes the biodiesel and finally is the distillation of the biodiesel. "The dissolution is agitated at low rpm because that at high revolutions sodium hydroxide can be oxidized" (Arbeláez & Rivera, 2007. pp45), should also be covered because amount of methanol due to its volatility can be lost. For the transesterification reaction are used reactors of four mouths with capacity of 500 mL and 1000 mL, magnetic stirrers, plates of agitation, spiral capacitors, mercury thermometers, thermostat bath and temperature controller. Figure 7, shows the setup for the biodiesel

*i*: is any combination of treatment

Fig. 6. Function f

2 *<sup>o</sup> Nlevels* , because we have a high level and one low

**4.2 Experimental development at the laboratory level** 

involved in the biodiesel production.

Table 10. Amount of reagents

production.

is accepted or rejected with the help of figure 6.

For the catalyst concentration the values vary in a range of 0.4 - 2% being the concentration 1% better but the reaction yield is not very high.

For the design factorial mentioned we can set the number of trials, having clear that 2 is the number of levels and k is the number of factors, i.e. which has a total of 24 treatments and is carried out a duplicated for each one, as should be taken into account the time limit and the project costs, which in total we have 16 experiments. Then is defined the signs matrix (table 9), where it is necessary to enumerate the trials and then is assigned a combination of treatments that aims to relate the design factors.

Consecutively is assigned the level for each combination, positive for the design factor that is being evaluated in the trial and negative for whose are not related. For this type of design the first trial has low levels and the final test has the higher levels.


Table 9. Matrix of signs

Performance is evaluated according to the treatments combination, considering that a duplicated is made by treatment. With data from the response variable, which is the yield, we carry out a statistical analysis by means of the ANOVA table or analysis of variance for data, which gives the more appropriate conditions for each factors of design and allows establishing that trials were the best.

For each main effect and interaction effect we have associated a single degree of freedom, so this is calculated using the following expression:

$$GL\_i = \mathcal{N}^0\_{\text{wives}} - \mathbf{1} \tag{1}$$

Where:

*i*: is any combination of treatment

36 Biodiesel – Feedstocks and Processing Technologies

For the catalyst concentration the values vary in a range of 0.4 - 2% being the concentration

For the design factorial mentioned we can set the number of trials, having clear that 2 is the number of levels and k is the number of factors, i.e. which has a total of 24 treatments and is carried out a duplicated for each one, as should be taken into account the time limit and the project costs, which in total we have 16 experiments. Then is defined the signs matrix (table 9), where it is necessary to enumerate the trials and then is assigned a combination of

Consecutively is assigned the level for each combination, positive for the design factor that is being evaluated in the trial and negative for whose are not related. For this type of design

1 1 - - - - 2 A + - - - 3 B - + - - 4 C - - + - 5 D - - - + 6 AB + + - - 7 AC + - + - 8 AD + - - + 9 BC - + + - 10 BD - + - + 11 CD - - + + 12 ABC + + + - 13 ABD + + - + 14 ACD + - + + 15 BCD - + + + 16 ABCD + + + +

Performance is evaluated according to the treatments combination, considering that a duplicated is made by treatment. With data from the response variable, which is the yield, we carry out a statistical analysis by means of the ANOVA table or analysis of variance for data, which gives the more appropriate conditions for each factors of design and allows

For each main effect and interaction effect we have associated a single degree of freedom, so

<sup>0</sup> 1 *GL N i niveles* (1)

**A B C D** 

**Trial Combination of Treatments Design Factors** 

1% better but the reaction yield is not very high.

treatments that aims to relate the design factors.

Table 9. Matrix of signs

Where:

establishing that trials were the best.

this is calculated using the following expression:

the first trial has low levels and the final test has the higher levels.

2 *<sup>o</sup> Nlevels* , because we have a high level and one low

To determine that interactions are significant an f for each source of variation is calculated and compared to f0,05 (1,16) = 4,49, with this we can determine in which region (probable region RP or critical region RC) is each treatment and thus be able to establish that treatment is accepted or rejected with the help of figure 6.

Fig. 6. Function f

#### **4.2 Experimental development at the laboratory level**

Table 10, shows the quantities determined at the laboratory level for each compound that is involved in the biodiesel production.


Table 10. Amount of reagents

First is the filtration of used oil, then mixing alcohol/catalyst to add it to the reactor which contains the oil at the temperature of the transesterification reaction, then is the separation of biodiesel and glycerin, washes the biodiesel and finally is the distillation of the biodiesel. "The dissolution is agitated at low rpm because that at high revolutions sodium hydroxide can be oxidized" (Arbeláez & Rivera, 2007. pp45), should also be covered because amount of methanol due to its volatility can be lost. For the transesterification reaction are used reactors of four mouths with capacity of 500 mL and 1000 mL, magnetic stirrers, plates of agitation, spiral capacitors, mercury thermometers, thermostat bath and temperature controller. Figure 7, shows the setup for the biodiesel production.

Biodiesel Production from Waste Cooking Oil 39

The distillation is carried out at 40 °C, temperature which is below the boiling point of methanol. The vacuum pump is used in order to minimize the time of distillation and

Fig. 10. Biodiesel distillation (a) Mounting: i. vacuum pump ii. Vacuum trap iii. Hot plate iv.

We show the results and analysis of tests conducted at the laboratory level, as its density and the analysis of variance. According to the literature retrieved biodiesel is "liquid, transparent and reddish color without any content of solids or gels" (Arbeláez & Rivera,

Taking into account the results of the biodiesel appearance, it can be concluded that the catalyst percentage influences in the biodiesel stability because that similar conditions were equal in appearance. The majority of samples that had contained solids, gels and their

Opaque samples as the 3, 4 and 7 are because have much water content, this might be for the washes with water at 40 °C and its water content was increased. Opacity is an indicator that

appearance was opaque, were the samples where used 0.5% NaOH.

Fig. 9. First biodiesel wash: (a) Water at 40 °C (b) acetic acid solution

vacuum trap is used to prevent waste of alcohol and water to the pump.

Thermometer (b) Distilled biodiesel

the methyl esters have presence of water.

**4.3 Results and analysis** 

2007. pp37).

Fig. 7. Biodiesel production assembly: a) Reactor of 500 mL b) Reactor of 1L.

To carry out the transesterification reaction is loaded oil at the reactors and heated up to reaction temperature, while it reaches the temperature is made the mixture of the catalyst with alcohol, then it is added to the reactor. At the end of the reaction time is added HCl to 37 per cent in order to neutralize the reaction.

Completed reaction, the product is poured into the separation funnels and let a minimum time of 8 hours, to ensure good separation of the phases (Figure 8). Separation times were not equal for all runs varied between 10-24 hours.

Fig. 8. Biodiesel-Glycerin separation

Once separate the glycerin from biodiesel, it is carried out the washing on the funnels. Separate the glycerin, the biodiesel must be washed because that may contain residues of catalyst, methanol, soaps and glycerides without reacting. Two types of washings are established according to the experimental design.

In one of the washing, water at 40 °C is used for three washes. Other tests of washing have been conducted with acetic acid 10% wt, where is used the same amount of used cooking oil; two washes are carried out with acid solution and the third is done with deionized water.

Fig. 7. Biodiesel production assembly: a) Reactor of 500 mL b) Reactor of 1L.

37 per cent in order to neutralize the reaction.

Fig. 8. Biodiesel-Glycerin separation

water.

established according to the experimental design.

not equal for all runs varied between 10-24 hours.

To carry out the transesterification reaction is loaded oil at the reactors and heated up to reaction temperature, while it reaches the temperature is made the mixture of the catalyst with alcohol, then it is added to the reactor. At the end of the reaction time is added HCl to

Completed reaction, the product is poured into the separation funnels and let a minimum time of 8 hours, to ensure good separation of the phases (Figure 8). Separation times were

Once separate the glycerin from biodiesel, it is carried out the washing on the funnels. Separate the glycerin, the biodiesel must be washed because that may contain residues of catalyst, methanol, soaps and glycerides without reacting. Two types of washings are

In one of the washing, water at 40 °C is used for three washes. Other tests of washing have been conducted with acetic acid 10% wt, where is used the same amount of used cooking oil; two washes are carried out with acid solution and the third is done with deionized

Fig. 9. First biodiesel wash: (a) Water at 40 °C (b) acetic acid solution

The distillation is carried out at 40 °C, temperature which is below the boiling point of methanol. The vacuum pump is used in order to minimize the time of distillation and vacuum trap is used to prevent waste of alcohol and water to the pump.

Fig. 10. Biodiesel distillation (a) Mounting: i. vacuum pump ii. Vacuum trap iii. Hot plate iv. Thermometer (b) Distilled biodiesel

#### **4.3 Results and analysis**

We show the results and analysis of tests conducted at the laboratory level, as its density and the analysis of variance. According to the literature retrieved biodiesel is "liquid, transparent and reddish color without any content of solids or gels" (Arbeláez & Rivera, 2007. pp37).

Taking into account the results of the biodiesel appearance, it can be concluded that the catalyst percentage influences in the biodiesel stability because that similar conditions were equal in appearance. The majority of samples that had contained solids, gels and their appearance was opaque, were the samples where used 0.5% NaOH.

Opaque samples as the 3, 4 and 7 are because have much water content, this might be for the washes with water at 40 °C and its water content was increased. Opacity is an indicator that the methyl esters have presence of water.

Biodiesel Production from Waste Cooking Oil 41

1 1 6:1 0,5 50 Water (40°C) 2 A 9:1 0,5 50 Water (40°C) 3 B 6:1 0,7 50 Water (40°C) 4 AB 9:1 0,7 50 Water (40°C) 5 C 6:1 0,5 60 Water (40°C) 6 AC 9:1 0,5 60 Water (40°C) 7 BC 6:1 0,7 60 Water (40°C) 8 ABC 9:1 0,7 60 Water (40°C) 9 D 6:1 0,5 50 Acetic Acid (T amb) 10 AD 9:1 0,5 50 Acetic Acid (T amb) 11 BD 6:1 0,7 50 Acetic Acid (T amb) 12 ABD 9:1 0,7 50 Acetic Acid (T amb) 13 CD 6:1 0,5 60 Acetic Acid (T amb) 14 ACD 9:1 0,5 60 Acetic Acid (T amb) 15 BCD 6:1 0,7 60 Acetic Acid (T amb) 16 ABCD 9:1 0,7 60 Acetic Acid (T amb)

**DESIGN FACTORS A B C D** 

> **PRODUCTIVITY (%) DUPLICATE 1 DUPLICATE 2**

**TEST COMBINATION OF** 

Table 12. Rearranged experimental matrix

Table 13. Reaction productivity

**TEST COMBINATION OF** 

**TREATMENTS** 

1 1 70 44,9 2 A 79,5 74,3 3 B 85,6 84,5 4 AB 93,7 93,9 5 C 69,4 68,4 6 AC 62,3 88,2 7 BC 64,5 62,6 8 ABC 88,7 85,5 9 D 62,1 63,1 10 AD 89,5 60,7 11 BD 76,2 80,7 12 ABD 88,9 88,5 13 CD 61,3 57,5 14 ACD 81,2 80,3 15 BCD 74,8 71,8 16 ABCD 86,2 81,8

We carry out the ANOVA statistical analysis (table 14) and the test of hypothesis (table 15).

**TREATMENTS** 


The table 11 shows the densities for each test sample.

Table 11. Density for each sample

The biodiesel density according to standard ASTM D-1298 must be in a range of (0.86 - 0.90 g/ml), the density does not guarantee that retrieved biodiesel is of good quality, but is taken to compare samples with each other, due there is evidence that satisfy with the provided density but its appearance is not adequate or are samples which do not comply with the permitted density value but its appearance is appropriated. As for example, the duplicate 2 from sample 1 exceeds the density range allowed for biodiesel, but the appearance fulfill with the stipulated features. For the sample 11, both the duplicate 1 and the 2 exceed the density level and its appearance is a little opaque.

Samples 11 and 12 are in the density range allowed but the appearance does not meet any features because have high solids content and are highly opaque.

Some samples contain solids and do not fulfill with the physical characteristics of biodiesel, have a density within the level agreed by the ASTM D-1298 standard for a biodiesel of good quality, which must be due to that the solids are smaller proportion than the liquid phase that is rich in methyl esters.

It can be concluded that the density and appearance analysis are not reliable parameters to determine the biodiesel quality. For this reason, based on the order of the table 12, we can determine the variable response (table 13), which is expressed as the ratio between the mass of the biodiesel produced and the mass of oil used for the production (productivity per cent).

**Biodiesel density (g/ml)** 

1 0,902 0,910 2 0,902 0,877 3 0,867 0,887 4 0,893 0,881 5 0,897 0,903 6 0,885 0,887 7 0,883 0,906 8 0,906 0,860 9 0,871 0,887 10 0,885 0,893 11 0,914 0,906 12 0,897 0,891 13 0,900 0,895 14 0,885 0,875 15 0,883 0,862 16 0,873 0,891

The biodiesel density according to standard ASTM D-1298 must be in a range of (0.86 - 0.90 g/ml), the density does not guarantee that retrieved biodiesel is of good quality, but is taken to compare samples with each other, due there is evidence that satisfy with the provided density but its appearance is not adequate or are samples which do not comply with the permitted density value but its appearance is appropriated. As for example, the duplicate 2 from sample 1 exceeds the density range allowed for biodiesel, but the appearance fulfill with the stipulated features. For the sample 11, both the duplicate 1 and the 2 exceed the

Samples 11 and 12 are in the density range allowed but the appearance does not meet any

Some samples contain solids and do not fulfill with the physical characteristics of biodiesel, have a density within the level agreed by the ASTM D-1298 standard for a biodiesel of good quality, which must be due to that the solids are smaller proportion than the liquid phase

It can be concluded that the density and appearance analysis are not reliable parameters to determine the biodiesel quality. For this reason, based on the order of the table 12, we can determine the variable response (table 13), which is expressed as the ratio between the mass of the biodiesel produced and the mass of oil used for the production (productivity per

**DUPLICATE 1 DUPLICATE 2** 

**Biodiesel density (g/ml)** 

The table 11 shows the densities for each test sample.

**TEST** 

Table 11. Density for each sample

that is rich in methyl esters.

cent).

density level and its appearance is a little opaque.

features because have high solids content and are highly opaque.


Table 12. Rearranged experimental matrix


Table 13. Reaction productivity

We carry out the ANOVA statistical analysis (table 14) and the test of hypothesis (table 15).

Biodiesel Production from Waste Cooking Oil 43

The factor A, the molar ratio alcohol/oil, has a significant effect on the reaction productivity, since the effect is positive by increasing the molar ratio increases productivity, for this

The factor B, the catalyst concentration has a significant effect on the reaction productivity so increasing the catalyst concentration increases the reaction productivity for this reason we select 0.7% w/w. The factor C, the reaction temperature has no significant effect, but is recommended to work with the lowest level, i.e. at a temperature 50 °C to prevent a further loss of methanol due to its volatility. The factor D, the washing agent has no significant

The combination of treatments AB, AC, AD, CD, ABC, ABD, ACD, BCD, ABCD, do not has significant effects on the reaction productivity. The treatment combination BC has significant effects on the reaction productivity, so it is advisable to work with levels higher

Table 16, shows the made characterization of the sample obtained to a molar ratio alcohol/oil 9:1, catalyst concentration 0.7% w/w, reaction temperature of 50 °C and water at

**Properties Unit Results Standard (ASTM D-6751)** 

for each factor, catalyst concentration of 0.7 %p/p and reaction temperature of 50 °C.

Density at 15.6 °C kg/m3 889.9 860- 900 Grades API 27 Minimum 32

Cetane index 48 Minimum 47 Caloric value J/g 40,873.00 37,216.00 Temperature 90% distilled °C 332 Maximum 360

API gravity for the biodiesel retrieved is in a range of 32-34 degrees API, the analyzed sample showed a value below the reported ranges, which indicates that the biodiesel retrieved from this sample has a high density, which as we see in the analysis is of 889.9 kg/m3, taking into account that the API gravity is inversely proportional to the density. As for the other properties analyzed, these can be found within the values reported by the

We can conclude that using acetic acid or water as a washing agent does not affect the reaction productivity, similar to the reaction temperature has no effect on the variable response within the levels used in the research. The unique variables that affect the biodiesel

This research was carried out in the laboratory of the Natural Resources Energetic Exploitation research group of the Chemistry Department's National University of

Cinematic Viscosity at 40°C Cst 5.21 1.9 – 6

effect because the effect is negative, we select the low level (-) water at 40 °C.

40 °C as washing agent that is the biodiesel with a best properties.

Table 16. Properties of the biodiesel sample to the best conditions

production are the catalyst concentration and the molar ratio alcohol/oil.

According with the above, the best conditions of operation are:

literature, which guarantees the quality of biodiesel.

**5. Conclusions** 

 Molar ratio alcohol/aceite: 9:1 Catalyst concentration of: 0.7% w/w

 Reaction temperature: 50 °C Washing agent: water at 40 °C

**6. Acknowledgment** 

reason the highest 9:1 ratio is selected.


Table 14. ANOVA TABLE


Table 15. Hypothesis test

A 14,1125 1593,30 1 1593,30 22,78 B 12,2 1190,72 1 1190,72 17,02 C -3,225 83,205 1 83,21 1,19 D -0,7125 4,06125 1 4,06 0,06

AB -0,8 5,12 1 5,12 0,07 AC 1,375 15,125 1 15,12 0,22 AD -0,4125 1,36125 1 1,36 0,02 BC -6,2875 316,26125 1 316,26 4,52 BD -0,55 2,42 1 2,42 0,03 CD 1,375 15,125 1 15,13 0,22

ABC 2,437500 47,531250 1 47,53 0,68 ABD -2,425000 47,045000 1 47,05 0,67 ACD 0,950000 7,220000 1 7,22 0,10 BCD 3,212500 82,561250 1 82,56 1,1803

ABCD -4,5375 164,71125 1 164,71 2,35

**OF TREATMENTS EFECTS f CALCULATED f alfa DECISION** 

A 14,1125 22,77751271 4,49 NOT ACCEPTED B 12,2 17,02229251 4,49 NOT ACCEPTED C -3,225 1,189481867 4,49 ACCEPTED D -0,7125 0,058058809 4,49 ACCEPTED

AB -0,8 0,073194485 4,49 ACCEPTED AC 1,375 0,216223944 4,49 ACCEPTED AD -0,4125 0,019460155 4,49 ACCEPTED BC -6,2875 4,521206923 4,49 NOT ACCEPTED BD -0,55 0,034595831 4,49 ACCEPTED CD 1,375 0,216223944 4,49 ACCEPTED

ABC 2,437500 0,679497145 4,49 ACCEPTED ABD -2,425000 0,672545814 4,49 ACCEPTED ACD 0,950000 0,103215661 4,49 ACCEPTED BCD 3,212500 1,180278947 4,49 ACCEPTED

ABCD -4,5375 2,354678747 4,49 ACCEPTED

ERROR 1119,21 16 69,950625

TOTAL 4694,97875 31

**FREEDOM DEGREES** 

**MEAN** 

**SQUARE f CALCULATED** 

**SUM** 

**COMBINATION** 

Table 14. ANOVA TABLE

**COMBINATION** 

Table 15. Hypothesis test

**OF TREATMENTS EFECTS SQUARES**

The factor A, the molar ratio alcohol/oil, has a significant effect on the reaction productivity, since the effect is positive by increasing the molar ratio increases productivity, for this reason the highest 9:1 ratio is selected.

The factor B, the catalyst concentration has a significant effect on the reaction productivity so increasing the catalyst concentration increases the reaction productivity for this reason we select 0.7% w/w. The factor C, the reaction temperature has no significant effect, but is recommended to work with the lowest level, i.e. at a temperature 50 °C to prevent a further loss of methanol due to its volatility. The factor D, the washing agent has no significant effect because the effect is negative, we select the low level (-) water at 40 °C.

The combination of treatments AB, AC, AD, CD, ABC, ABD, ACD, BCD, ABCD, do not has significant effects on the reaction productivity. The treatment combination BC has significant effects on the reaction productivity, so it is advisable to work with levels higher for each factor, catalyst concentration of 0.7 %p/p and reaction temperature of 50 °C.

Table 16, shows the made characterization of the sample obtained to a molar ratio alcohol/oil 9:1, catalyst concentration 0.7% w/w, reaction temperature of 50 °C and water at 40 °C as washing agent that is the biodiesel with a best properties.


Table 16. Properties of the biodiesel sample to the best conditions

API gravity for the biodiesel retrieved is in a range of 32-34 degrees API, the analyzed sample showed a value below the reported ranges, which indicates that the biodiesel retrieved from this sample has a high density, which as we see in the analysis is of 889.9 kg/m3, taking into account that the API gravity is inversely proportional to the density. As for the other properties analyzed, these can be found within the values reported by the literature, which guarantees the quality of biodiesel.
