Investigation of Dynamic Viscosity and Calorific Value of Algae Biodiesel Blend with n-Butanol Additive

The transport sector primarily utilizes diesel fuel, which is a prominent energy source for various industries and applications. However, due to population growth, the increasing demand for diesel fuel leads to its depletion. This topic attracts many researchers looking for a solution through fuel alternatives, including the fuel properties of algae oil and its compatibility with diesel engines when combined with diesel fuel. To further understand the related topic, the study aims to explore the fuel properties, focusing on the viscosity and calorific value of Biodiesel Algae oil (BD) with n-butanol (nB). The Alge oil was prepared on the lab scale before blending to produce 4 different mixtures of Biodiesel. The results indicate that the blend 93BD7nB, which contained 93% of Algae biodiesel and 7% of n-butanol, obtained 0.168 Pa/s, which is in the required range in the standard limit ASTM D6751 whereas the calorific values for all samples above the standard limit EN 14214 indicate a good efficiency. In conclusion, this fuel blend exhibits promising potential for future utilization in diesel engine operations and provides an alternative solution for energy depletion.


Introduction
Energy is essential to our daily lives and is a basic human need.Energy is significant for humanity and is vital and plays an important role in facilitating sustainable economic growth.The energy crisis has emerged as a prominent and concerning threat worldwide.Fuels, one type of available energy, hold significant value to be combusted and generate substantial amounts to power the machine.Numerous aspects of our daily lives, especially transporting goods and individuals, heavily rely on fuel.Awareness regarding the depletion of fossil fuel resources and environmental concerns, Biodiesel gained attention in recent years.Biodiesel production is a promising alternative and rising in importance solution due to ever-increasing oil prices and environmental advantages [1].
Non-renewable fuels, including petroleum, have been extensively utilized for centuries, and their usage continues to escalate with each passing day.However, this reliance on non-renewable fuels leads to environmental issues like global warming.There is a pressing need for renewable and carbon-neutral transportation fuels to achieve environmental sustainability.In meeting these demands, microalgae serve as the primary source for biodiesel production as it can produce oil through photosynthesis.This represents a significantly more efficient approach to renewable resources and offers numerous environmental benefits [2].One of the remarkable qualities of algae is its ability to thrive without significant reliance on scarce nutrients, making it an optimal choice for biodiesel production.In contrast, other potential sources of biofuels, such as food crops, can pose challenges related to food availability due to their primary use as a food source [3].Algae has appeared as the sole sustainable source of Biodiesel, demonstrating compliance with international transport fuel requirements to fully replace fossil fuels and traditional Biodiesel in the future [4].
Meeting the strict emission regulations for diesel engines is a significant challenge due to the inherent trade-off between soot and NOx emissions [5].It is found in the previous study that n-butanol can be utilized as a fuel additive in diesel fuel and diesel-biodiesel blends without requiring any engine modifications.The studies also demonstrated that higher alcohols, including n-butanol, exhibit greater efficiency than lower alcohols in enhancing the characteristics of biodiesel fuel.Consequently, they hold significant potential for developing next-generation biofuels [6].The comprehensive investigations using standardized methods have examined fundamental biodiesel properties, including calorific value and viscosity [7].Recent studies have highlighted the significance of accurately representing viscosity under realistic mechanical conditions in engines, as it strongly correlates with fuel consumption.Various procedures outlined in three different standards can be employed [8].The higher the calorific value (CV) of fuel, the more significant its role in generating increased power output for an engine to operate efficiently [7].Calorific value, also known as a heating value, represents the energy released when a specific quantity of fuel is consumed.In an internal combustion engine, powers with higher CV are preferable.Diesel fuel possesses a higher CV compared to biodiesel fuel.The high oxygen content in biodiesel fuel contributes to its lower energy content than diesel oil.Consequently, an increase in the blending volume of biodiesel mixtures reduces energy output [7].
To understand the mentioned items, the study was carried out to examine the fuel properties of blended Biodiesel Algae Oil (BD) with n-butanol (nB) per the ASTM D6751 standard.The study focused on the Algae oil preparation on the lab scale and then proceeded to blend the prepared Algae oil with the fuel.Improved performance was expected for this Biodiesel as a fuel alternative.

The preparation of Algae Oil
The preparation of algae oil involved a two-stage process, beginning with the separation of algae from the water, followed by algae oil extraction.The process involved two main materials; 1) Algae and 2) Ethanol.Algae was collected as in Figure 1(a), and a separate process was carried out as in Figure 1 (b).

Biodiesel Oil and Butanol Blending Preparation
The blending of the samples followed the guidelines outlined by the American Society of Materials (ASTM) standard of ASTM D6751.Four blending samples were prepared, as summarized in Table 1.
The preparation of the blends involved several steps; 1) Biodiesel Algae Oil (BD) and n-butanol (nB) were separately measured using graduated cylinders to determine the appropriate volumes for each of the four samples.
2) The measured samples were combined in a small beaker and placed on a magnetic stirrer.
3) The mixture was stirred at a speed of 500 rpm for 15 minutes at room temperature until the mixture solution achieved the designated standard.

Biodiesel Properties Measurement
For the calculation of the calorific value of the blended oil consisting of BD and nB, the C200 Bomb Calorific instrument was used as in Figure 3 (a) and 3(b).The BD-nB blend mixtures were carefully weighed (0.5 -1.0 g) using a Digital Precision Balance, placed into a crucible, and then positioned on the holder.An ignition wire with a cotton thread attached to it was introduced into the crucible and brought into contact with the sample.The thread was ignited while the machine operated.Subsequently, the crucible holder was placed in the decomposition vessel, and distilled water was added to the vessel to reduce the pressure while the bomb calorimeter calculated the calorific values.This process was run for 10 to 20 minutes to obtain the calorific value.The same procedure was repeated for the four samples The blends were carefully poured into the viscometer tube, then inserted into the designated hole in the viscometer apparatus, as in Figure 4(a).The power supply was activated, and the spindle was installed correctly.Once the Viscometer reached a stable condition, the spindle was lowered into the viscometer tube containing the blends Figure 4(b).This procedure was repeated four times to account for the four sample blends.Upon completion of the process, the viscosity values were displayed on the control panel.Likewise, the fuel mixture sample was filled into the tube for viscosity determination, and the viscometer temperature was set to adhere to the ASTM standard of 40°C.Table 2 shows the manufacturers of equipment employed in this research.

Physiochemical properties of Algae and diesel blends
Table 3 evaluates the physicochemical properties of Algae oil and Diesel oil.Viscosity and calorific value are crucial properties for Biodiesel to ensure that it meets the operational requirements of diesel engines.These two factors significantly influence fuel injection spray characteristics, including fuel atomization efficiency, spray tip penetration, spray cone angle, spray wall interaction, and spray growth.These spray characteristics can impact the performance and emissions of diesel engines [9].In general, the combustion of biodiesel fuel in compression-ignition (CI) engines results in reduced smoke, particulate matter, carbon monoxide, and hydrocarbon emissions.Achieving such improvements involves various factors, including lower heating value, enhanced viscosity, higher density, lower calorific value, and the oxygen content of Biodiesel, which aim to enhance viscosity, minimize fuel consumption, and prevent adverse effects.Some researchers have explored incorporating different blending components such as methanol [10].

The effects of various blends on physiochemical properties
The measured properties, including dynamic viscosity and calorific value (CV), of neat Diesel Oil and blends of Algae Oil and n-butanol are presented in Table 4.In order to meet the ASTM D6751 standard, the viscosity value at 40°C should fall within the range of 0.1672-0.528Pa s.Based on the results, blend 93BD7nB, consisting of 93% Algae biodiesel and 7% n-butanol, exhibited a viscosity value of 0.168 Pa/s, which falls within the required standard range.This is clearly illustrated in the corresponding Figure 5. Additionally, it is evident from the experiment that higher percentages of n-butanol result in higher calorific values as shown in Figure 6.Comparison with the EN 14214 standard shows that all the values above the standard and indicates a good efficiency.

Conclusion
The varying proportions of Biodiesel Algae Oil and n-butanol influence the properties of the blends.Fuel properties are crucial in determining the quality of fuel mixing and combustion processes.The prepared blends must adhere to the standard, ensuring their quality.Viscosity significantly impacts engine performance, as higher viscosity can result in increased engine power.Similarly, a higher calorific value of the fuel leads to greater power output in the engine.Fuels with lower calorific values tend to burn inefficiently, increasing waste and air pollution.The optimum blend's viscosity and calorific value meet the standard requirements.As long as the properties of the blended oil fall within the standard range, it can be effectively utilized.

Figure 1 .
Figure 1.(a) Open Pond at Sekolah Menengah Tun Syed Sheh Shahabudin where Alge was collected (b) Algae after separating from water

Figure 5 .
Figure 5.Comparison of Viscosity with the ASTM D6751

Table 1 .
The percentage of the blend sample mixture

Table 2 :
Manufacturers of equipment

Table 3 .
The comparison of various properties of Algae Oil and Diesel Oil

Table 4 :
Various blends on Physiochemical properties

Table 5 :
Comparison of Calorific Value with EN 14214 StandardAll the measured data for both dynamic viscosity dan calorific value is in mean values and the summary of ANOVA were shown in Table5.Summary of ANOVA for viscosity and calorific value