An exhaustive experimental evaluation on the effects of using Jatropha biodiesel as an admixture in a DI diesel engine powered by waste plastic fuel

ABSTRACT

Incorporating jatropha biodiesel into discarded plastic oil and diesel on diesel engines and analysis of six fuel samples, three diesel types and two waste plastic diesel and jatropha biodiesel combinations. Following characterisation, a one-cylinder, DI diesel engine underwent comprehensive performance and emissions testing, involving spectroscopy. Addition of jatropha biodiesel led to reduced viscosity and density of the waste plastic-diesel blend, a 20% decrease in flash point, and 10% reductions in BSEC and BSFC, while lowering the engine's thermal efficiency by 5%. Jatropha biodiesel increased HC by 30%, reduced CO and NOx emissions by 20% and 5%. Both diesel and WPF20D60JB20 exhibited a of 36.45%, with BSEC values at full load of 9.91 and 9.84 MJ/kW-hr. WPF20D60JB20 demonstrated the best performance.

KEYWORDS:

• Engine efficiency
• alternative fuel
• exhaust emissions
• diesel fuel
• biofuel
• recycled plastic fuel

Nomenclature

BSEC	=	Brake specific energy consumption
BSFC	=	Brake specific fuel consumption
BTE	=	Brake thermal efficiency
CFPP	=	Cold filter plugging point
CHNS	=	Carbon Hydrogen Nitrogen Sulphur
CO	=	Carbon monoxide
CO2	=	Carbon dioxide
CN	=	Cetane number
EGT	=	Exhaust gas temperature
FTIR	=	Fourier transforms infrared spectroscopy
GC-MS	=	Gas chromatography mass Spectrometer
HC	=	Hydrocarbon
NOx	=	Nitrogen oxide
PM	=	Particulate matter
PP	=	Pour point
PPM	=	Parts per million
D 100	=	100% Diesel
WPF20D80	=	20% waste plastic fuel and 80% diesel
WPF30D70	=	30% waste plastic fuel 70% diesel
WPF20D70JB10	=	20% waste plastic fuel, 70% diesel and10% Jatropha biodiesel
WPF20D60JB20	=	20% waste plastic fuel, 60% diesel and 20% jatropha biodiesel
WPF30D40JB30	=	30% waste plastic fuel, 40% diesel and 30% Jatropha biodiesel

1. Introduction

The urgent need to find viable alternatives is driven by the rise in global temperatures and the scarcity of easily accessible fossil fuels (Uyumaz 2018). In the realm of readily available alternatives, both biodiesel and recycled plastic-derived fuel belong to the cohort of feasible options.

Biodiesel, a renewable energy source resembling conventional diesel, presents multiple advantages over fossil fuel alternatives. Due to its inherent oxygen content, biodiesel yields lower exhaust emissions, enhanced lubrication properties, and a non-toxic composition (Shekofteh et al. 2020; Yasasr 2020). Cutting-edge research has investigated the potential of ternary mixtures consisting of diesel, discarded plastic-derived biodiesel, and 1-pentanol as feasible alternatives (Yilmaz et al. 2022), demonstrating promising outcomes. Numerous studies have explored the effects of bio-diesel, diversely sourced vegetable oils, and biodiesel blends with other fuels in relation to efficiency and ignition properties in case of CI engines (Cihan 2021). Numerous researchers (Atmanli et al. 2015) have did trials on a 4-cycle, 4-cylinder turbocharged CI engine utilising a ternary mixture composed of diesel, vegetable oil, and n-butanol in ratio of 7:2:1. Their findings demonstrated a decline in several brake output parameters, including thermal efficiency, torque, and mean effective pressure, while fuel consumption increased. Canakci (2007) observed the effectiveness of bio-diesel obtained from soyabean oil in a 4-cylinder turbocharge CI engine. Their results revealed reductions in particulate matter, CO, & HC releases, but a 11.2% increase in nitrous oxide releases. Furthermore, because of the diminished heating value, BSFC experienced a 13.8% rise. A researcher (Atmanli 2016) explored ternary blends by combining diesel, waste biodiesel, and three distinct higher alcohols, discovering that the mixture led to increased carbon monoxide emissions and decreased nitric oxide emissions. In their study, Senatore et al. (2001) conducted an experiment using rapeseed methyl ester and diesel fuel blends, finding that these mixtures resulted in significantly decreased CO as well as smoke emission, while concurrently yielding high levels of NOx emission. Schumacher et al. Schumacher et al. (1996) examined soybean and diesel fuel blends, incorporating 10, 20, 30, and 40 percent soybean, in a 6V921A diesel engine. Their research findings uncovered fall in PM, hydrocarbon, carbon monoxide emissions, and an enhanced nitrous oxide emission. In their investigation of compression-ignition engines fuelled by isopropyl ester derived from soybean oil-diesel, Chang et al. (1996) reported a 2.5% reduction in particulate matter emissions, while nitrous oxide emissions increased by 12%. Moreover, researchers Atmanli and Yilmaz (2021) blended 1-pentanol with diesel fuel and conducted tests on conventional diesel engines, observing a fall in NOx emission with rise in hydrocarbon and carbon monoxide emission. Conversely, some studies demonstrated a different trend. Rakopoulos et al. (2006) and Knothe and Steidley (2005) found a fall in NOx emission while utilising ethyl alcohol and bioethanol blends in diesel engines. By making use of four-cylinder, 4-stroke CI engine, several quaternary fuel mixtures consisting of diesel, bio-diesel, vegetable-based bio-diesel, and higher alcohol were assessed (Yilmaz et al. 2018). In certain instances, the mean brake fuel consumption increased, while in others, NOx emissions decreased.

The viscosity of biodiesel is influenced by its molecular structure, which encompasses factors viz. the position, number, chain size, with shape of the double bond, as well as the composition of oxygenated mixtures (Knote 2005). As the chain length of unsaturated fatty compounds increases, an inverse relationship is observed, with viscosity, melting point, heat of combustion, and cetane number decreasing. Enhanced lubricity is not attributed to structural species but rather to unsaturated acids (Waynick 1997). Experimental results (Atmanli and Yilmaz 2020) obtained under varying loading situations and at a fixed speed using discarded oil methyl ester combined with higher alcohols, such as propanol, butanol, and pentol, revealed a fall in ‘brake thermal efficiency’ alongside lower carbon monoxide and NOx emissions. Furthermore, ethyl esters exhibit superior lubricity compared to methyl esters (Ladommatos, Parsi, and Knoweles 1996).

In a study by Damodharan et al. (2017) on diesel engines utilising fatty acid alkyl esters, it was observed that nitrogen oxide releases escalated with a shrinkage in chain length & unsaturation. A slight upsurge of NOx releases Ellapan and Pappula (2019) is noted if CI engine operates using bio-diesel, even though free fatty compounds possess a high cetane number. Investigations (Atmanli 2020) focused on biodiesel extraction from microalgal sources, using both freshwater and seawater, yielded promising outcomes at the laboratory scale.

Consequently, the primary disadvantages of biodiesel, despite its numerous advantages, lies in elevated viscosity & increased NOx emissions. Also, configuration of branched ester, the span of the chain, and their positioning significantly influence the physicochemical attributes of biodiesel, which subsequently affect its performance and emission features.

Plastics have become prevalent in both residential and industrial settings due to their affordability and adaptability (Sunaryo et al. 2021). This extensive usage has resulted in a rapid increase in plastic production and, consequently, a significant accumulation of plastic waste (Sunaryo et al. 2021). Researchers worldwide are now focusing on fuels derived from the depolymerisation of plastic waste. Fuel produced from recycled plastics exhibits numerous diesel-like properties, positioning it as a promising substitute for traditional diesel fuel (Karisathan Sundararajan and Ramachandran Bhagavathi 2016). Waste plastic fuel comprises 55% aromatic compounds, and it has been demonstrated that initiating an engine with pure waste plastic fuel generates a higher quantity of soot (Mani and Nagarajan 2009; Kumar, Mishra, and Roy 2022a, 2022b; Mani, Nagrajan, and Sampath 2010). Moreover, it has been suggested that waste plastic fuel enhances engine performance by reducing viscosity when combined with heavy oil (Mani and Nagarajan 2009).

A review of the literature indicates that both discarded plastic diesel and bio-diesel can be utilised as fuel in CI engine without necessitating modifications; however, each presents its own advantages and disadvantages. The present study explores the performance of diesel fuel blends containing jatropha biodiesel derived from recycled plastic. The investigation assesses blends of discarded plastic fuel & diesel, comparing their features, performance, and emission to those of traditional diesel fuel. It is worth mentioning here that the present work is an extension of the work performed earlier (Kumar, Mishra, and Roy 2022a, 2022b) by the authors.

2. Procedures and materials

2.1. Discarded plastic-derived fuel

The waste plastic-derived fuel comes from a company called ‘Sustainable Technologies & Environmental Projects Private Limited, Vasai, Mumbai’ (WPF). It’s a byproduct of depolymerising used plastic in a dedicated reactor and has additional value. Using a special catalyst and a small amount of oxygen, the reaction is conducted at a maximum temperature of 350 degrees Celsius.

At the current facility, batch sizes ranged from 25 to 50 kg of waste plastic. The condenser is cooled by circulating water. Materials processing results in the production of gases, which are then burned close to the vent pipe.

Weighing and loading the organic waste into the facility, then using the thermostat, the slow heating process may be initiated. As the temperature reaches above 150 degrees Celsius, the produced gases are allowed to break as they flow through a catalyst. After passing through the vent line, the gases go through the condenser, at which point the water and molten fuel undergo partition. The combustion of the gas is subsequently sparked by lighting the vent pipe. The condenser’s accumulated liquid is emptied. It takes 4 h and 30 min to turn plastic trash into usable liquid fuel. At the end of each cycle, the leftovers are collected, sorted, and quantified.

The conversion rates for High-density polyethylene, low-density polyethylene, and polypropylene are optimal, producing approximately one litre from one kilogramme of discards, but the conversion ratio for other plastics is 800 millilitres per kilogramme.

The energy that is produced at the plant is about eight times less than what is required for the conversion that takes place there. The plant is self-sufficient and does not need any additional power sources; rather, the exhaust gases produced during the process power the plant.

2.2. Jatropha bio-diesel

Jatropha bio-diesel is a kind of renewable fuels that is made by the seeds of the jatropha plant. In this instance, the jatropha biodiesel was acquired or obtained from a company named ‘Southern Online Bio Technologies Limited.’ This company is in the city of Hyderabad, which is situated in the southern part of India.

2.3. Preparation of fuel specimen

Employing a magnetic mixer, multiple blends of discarded plastic-derived fuel, jatropha bio-diesel, along-with diesel were mixed to estimate their impact on characteristic, efficiency, and the emission attributes of the assorted mixtures. The temperature for this method of mixing is 35 degrees Celsius. Each sample was three litres in volume and was subjected to vigorous shaking for one hour. The first set of samples has a mixture of old diesel and waste plastic fuel as its component parts. Between twenty and thirty percent of the total volume of the fuel is comprised of recycled plastic trash. The second collection of specimens being prepared consists of blends involving discarded plastic-derived fuel, diesel, and jatropha bio-diesel in the following proportions: 20:70:10, 20:60:10, and 30:40:30. This is being done so that the impact of jatropha biodiesel as an addition may be studied. Moreover, a specimen of standard diesel is gathered to serve as a basis for comparing the results of the other fuel samples. After being kept at room temperature for twenty-one days, every fuel sample was put through a stability test to see whether or not it would remain stable. Ultimately, the fuel specimens are categorised and labelled in accordance with the pertinent criteria.

3. Experimentation methodology

3.1. Assessment of physical and chemical attributes

Testing procedure as well as the equipment that was used are all described in full in Table 1.

Table 1. Methodology & instrument utilised.

Properties	Testing method	Instrument utilised
Specific Gravity	‘IP 59/82’	‘Westpal Balance’
Viscosity	‘ASTM D2270’	‘Redwood Viscometer’
Flash Point	‘ASTM D93-80’	‘Pensky Martens Apparatus’
Calorific Value	‘ASTM D808/240’	‘Bomb Calorimeter’
Acid Number	‘ASTM D664-09a’	‘REMI Equipments’
Cold Filter Plugging point	‘ASTM D6371’	‘Vibson Scientific’
Pour Point	‘ASTM D97-09’	‘Vibson Scientific’

Analytical results from a ‘CHNS inspection’ of fuel samples were examined on a ‘M/s Elementar’s Vario EL III,’ and the temperature of the combustion was maintained at 950 degrees Celsius throughout the process. Helium was used as the transport gas. IR spectrum of liquid fuel specimens were obtained in the region of 4000–400 cm⁻¹ by using a ‘Shimadzu Company infrared spectrometer.’ During the FTIR procedure, a little drop of the mixed fuel was positioned between two KBr plates for the purpose of identifying and analysing the compounds that were present. In order to differentiate between the various compounds that are present in fuel samples, the analytical method known as ‘gas chromatography-mass spectrometry’ (GC-MS) is used. This method merges the benefits of both liquid and gas chromatography, in addition to mass spectrometry. Fuel specimens were chromatographed employing ‘Jeol, AccuTOF GCV, and NIST software,’ subsequently utilised for scrutinising the peaks of the chromatogram.

3.2. Configuration of an engine for testing

An electrical dynamometer was installed with great skill to measure the engine’s power output under diverse conditions. A U-shaped manometer, precisely affixed to the air intake box, enhanced the precision of measurements by calculating the volume of air flowing into the engine. A cylindrical tank was present, which had a burette firmly attached to one of its sides. The stand on which this tank was placed was constructed out of wood. By shutting off the valve connected to the tank, the fuel blend could be permitted to enter the engine through a calibrated burette filter, which facilitated the precise calculation of fuel consumption. To gauge the speed of the engine, a tachometer was utilised. The amount of fuel being used was monitored with great precision by means of a timer. To determine the level of exhaust production, a state-of-the-art emission analyzer (specifically the HG-540 model) was employed and directed towards a probe for analysis while the engine was kept running steadily at one thousand five hundred revolutions per minute, the maximum RPM recommended by the engine manufacturer. A sequence of tests was carried out, commencing with the engine powered by diesel, then progressing to discarded plastic-derived fuel, bio-diesel diesel, and lastly, bio-diesel diesel once more. The tests were conducted meticulously, and the findings acquired were thoroughly examined to gain an understanding of the engine’s performance under varying fuel circumstances (Figure 1, Table 2).

Figure 1. Experimental set-up. (1) Direct Injection CI engine; (2) Electric-dynamometer; (3) Load control; (4) Air box; (5) U-type manometer; (6) Fuel tank; (7) Burette; (8) Gas analyser.

Table 2. Engine and its specifics.

Make	Kirloskar Diesel Engine
Type	Axially Vertical – one cylinder
Depiction	‘Vertical, natural temperature starting, totally enclosed, watercooled’
Timing, ‘fuel injection’	26^o before ‘Top Dead Centre’
Fuel tank volume	‘1 Gallon (4.6 Litres)’
Injection nozzle	‘Bosch type DLL. 110 S 32’
Fuel Pump	‘Bosch type H-PFR 1A 90/1’
‘No. of strokes’	Four
‘No. of cylinder’	‘Single’
‘Bore diameter’	‘80 mm’
‘Stroke length’	‘110 mm’
‘Rated power’	‘5 HP’
‘Speed’	‘1500 rpm’
‘Cooling’	‘Water’
‘Loading Device’	‘Electrical Swinging field type Dynamometer’

4. Examination of the results

4.1. Fuel characterisation

Table 3 provides a comprehensive list of properties of the fuels used in the experiments. Viscosity, one of the important properties, should be as high as possible to ensure optimal performance. A higher viscosity results in larger droplet size, which leads to reduced energy efficiency, decreased engine performance, and increased soot production. If the viscosity falls below the recommended limit, the sliding components of the fuel injection system may not be adequately lubricated, causing potential damage (Pundir 2010).

Table 3. Properties of specimens.

Properties	WPF20D80	WPF30D70	WPF20D70JB10	WPF20D60JB20	WPF30D40JB30	D100
Viscosity (Poise)	0.052	0.064	0.062	0.0487	0.0520	0.061
Density (g/ml)	0.832	0.815	0.818	0.819	0.812	0.80
Flash Point (^oC)	66	69	64	65	70	61
Calorific value (MJ/kg)	44.39	45.58	44.14	43.12	42.78	45.35
Pour point	3	–	3	–	–	6
CFPP	−3	–	−3	–	–	1
Acid number (mgKOH/g)	1.62	1.89	1.85	1.21	1.98	0.03
Aniline point	48.40	42.20	39.7	45.2	35.1	68.1
Diesel index	46	47	47	47	40	49

The experiment revealed that WPF20D60JB20 possessed the lowest viscosity, whereas WPF30D70 exhibited the highest viscosity among all the tested fuels. Notably, fuel samples containing jatropha biodiesel blended with waste plastic fuel and diesel exhibited lower viscosity than diesel alone. Additionally, it was noted that combining discarded plastic-derived fuel with diesel containing jatropha bio-diesel led to only a slight change in fuel viscosity. These findings have significant implications for fuel efficiency, engine performance, and environmental impact, as viscosity can influence droplet size, combustion efficiency, and emissions production.

To regulate the amount of fuel injected into a diesel engine, a volume metering system is employed in its fuel injector system. As the density of the fuel increases, the amount of energy that can be stored in a given volume also increases. As a result, the rate of fuel mass entering the engine escalates in tandem with the rising density of the fuel. Under full load, the exhaust volume increases due to the higher density and richer mixture (Van Basshuysen and Schaefer 2016). WPF20D80 exhibited the greatest density, whereas incorporating jatropha bio-diesel into discarded plastic fuel and diesel blends led to a reduction in density.

When it comes to ensuring safety measures for fuel transportation and storage, the flash point is a crucial parameter that cannot be overlooked. It provides insights into the possible fire hazards associated with the fuel. The flash point signifies the lowest temperature at which fuel vapours can combust when subjected to an external source of ignition. Thus, a thorough understanding of the flash point is essential to prevent any untoward incidents.

In the quest for the perfect fuel, a blend of discarded plastic fuel with diesel has proved itself a safer option with a higher ignition temperature than diesel on its own. However, introducing jatropha biodiesel to the blend can be a bit tricky as it may lead to a slight decrease or a significant increase in the flash point depending on the percentage used. Furthermore, the calorific value (C.V.), which indicates how much heat a fuel can produce relative to its mass, is at its lowest in the case of WPF30D40JB30, a blend of discarded plastic fuel-diesel and jatropha bio-diesel. It appears that fuel blending is a delicate balancing act that requires a careful consideration of various properties to achieve the desired results.

The ‘Cold Filter Plugging Point (CFPP)’ and ‘pour point’ represent critical parameters in evaluating fuel quality under low-temperature conditions. In frigid operational environments, the efficacy of fuel pump, pipe, and injector could be hindered because of limited fuel flow. The pour point is defined as the minimum temperature at which oil retains its fluidity, whereas the Critical Failure Point (CFP) refers to the lowest temperature at which a fuel system can function without experiencing malfunctions. Among the analyzed fuels, diesel demonstrates the highest pour point and CFPP values, thus highlighting its susceptibility to performance issues in cold weather conditions.

The acid number of a fuel serves as an indicator of its acidic components, which may be present as additives or degradation products in various petroleum and biodiesel blends. A high acid number is associated with increased corrosion of rubber components coupled with accumulation of deposits inside engine. Among the different fuels, diesel exhibits the lowest acid value, signifying a reduced propensity for such deleterious effects. In comparison, the acid value of WPF20 D60JB20, a blended fuel, is the lowest within its category, thereby suggesting its potential to minimise engine damage caused by acidic constituents.

Given the time-consuming and costly nature of calculating an ‘cetane number (CN),’ a novel relationship, also referred as ‘Diesel Index,’ has been developed as an alternative. This index is associated with the fuel’s hydrocarbon content and density. N-paraffin exhibits superior ignition quality, while aromatics possess a lower ignition quality. The Diesel Index is intrinsically linked to the aniline point, which is defined as the least warmth where equal volumes of gasoline and aniline can be mixed, serving as a metric for the fuel’s aromatic content. As the aromatic concentration of a fuel escalates, the aniline point declines accordingly. A higher cetane number in diesel oil contributes to its enhanced ignitability and rapid heat generation. For any given engine, the peak combustion pressure and temperature are influenced by the ignition delay, which is, in turn, contingent upon the fuel’s cetane number. This relationship underscores the significance of cetane number in understanding fuel performance and engine combustion characteristics.

Experimental findings reveal that the Diesel Index remained relatively stable upon the incorporation of 10% or 20% jatropha biodiesel into waste plastic fuel-diesel blends. Nonetheless, a notable decrease in the Diesel Index was observed when 30% jatropha biodiesel was added to these blends, suggesting a significant influence on fuel properties at higher jatropha biodiesel concentrations.

Investigations of fuel samples employing Fourier Transform Infrared (FTIR) spectroscopy have yielded insightful results. Figures 2–7 present the FTIR spectra for diverse oil blends, while Table 4 delineates the FTIR analysis of various oil blends combined with diesel, focusing on distinct moieties. The findings suggest that an assortment of mixtures, encompassing discarded plastic oil with diesel, discarded plastic oil with diesel-jatropha bio-diesel, as well as diesel, exhibit certain commonalities. Notably, these fuels comprise both sizeable C-CH₃ clusters along-with more dense constituents such as CH₂, CH₃ groups, and C=CH₂.

Figure 2. D100 – Fourier transform infrared (FTIR) spectroscopy.

Figure 3. WPF20D80 – Fourier transform infrared (FTIR) spectroscopy.

Figure 4. WPF30D70 – Fourier transform infrared (FTIR) spectroscopy.

Figure 5. WPF20D70JB10 – Fourier transform infrared (FTIR) spectroscopy.

Figure 6. WPF20D60JB20 – Fourier transform infrared (FTIR) spectroscopy.

Figure 7. WPF30D40JB30 – Fourier transform infrared (FTIR) spectroscopy.

Table 4. Fourier transform infrared spectroscopy of fuel.

Specimen Id	D100	WPF20D80	WPF30D70	WPF20D70JB10	WPF20D60JB20	WPF30D40JB30
C-CH3	2964 2663	2962 2954	2964 2870	2996	2927	2929
Non-conjugated	1850 1739	1699	1938 1857	1882 1754	1743	1743
Conjugated	–	1600	1705 1597	–	1600	1600
CH2	1469	1453	1469	1471	1452	1452
CH3	1379	1375	1379	1382	1375	1375
C-O	–	1172	–	–	1170	1170
Acetate	–	1028	–	–	1022	1022
CH = CH (trans)	948	964	956	–	–	–
C = CH2	–	812	896	–	–	–
CH = CH (cis)	709	696	704	696	698	698

Table 5 meticulously documents the outcomes derived from the comprehensive CHNS (Carbon, Hydrogen, Nitrogen, and Sulphur) analysis of an array of fuel samples, encompassing the quantification of their elemental composition. This tabulated representation provides an in-depth understanding of the fundamental characteristics of the investigated oil samples, enabling a thorough evaluation of their performance, combustion behaviour, and potential environmental impact in relation to their elemental constituents.

Table 5. ‘CHNS’ analysis information for specimens.

Specimen	Carbon (%)	Hydrogen (%)	Nitrogen (%)	Sulphur (%)	Oxygen (%)
D100	84.7	13.6	1.14	0.44	0.03
WPF20D80	82.9	11.9	1.82	0.45	2.76
WPF30D70	82.63	11.1	1.98	0.46	3.79
WPF20D70JB10	84.10	12.71	1.013	0.655	1.52
WPF20D60 JB20	82.36	11.88	2.039	0.518	3.70
WPF30D40 JB30	81.98	11.13	1.751	0.853	4.25

The study revealed that blending waste plastic fuel with diesel resulted in a reduction of carbon content, while the oxygen levels experienced an upsurge, attributable to the incorporation of jatropha biodiesel. The cetane number of a hydrocarbon molecule serves as an indicator of the number of carbon atoms present within the molecular chain (Sahoo and Das 2009). Notably, biodiesel blends exhibit a substantially higher oxygen content compared to diesel. Consequently, fuels with elevated oxygen percentages yield a diminished production of dry soot, particularly under high-load conditions (Wu et al. 2009).

4.2. Oil sample ‘GC-MS’ analysis

The ‘Gas Chromatography-Mass Spectrometry (GC-MS)’ chromatograms of the oil samples are meticulously illustrated in Figures 8–11, providing a comprehensive visual representation of the sample constituents. Concurrently, the quantitative data associated with these oil samples are systematically compiled in Tables 6–9, facilitating an in-depth analysis and comparison of the fuel properties and their underlying chemical composition.

Figure 8. GCMS WPF20D80.

Figure 9. GCMS WPF30D70.

Figure 10. GCMS WPF20D70JB10.

Figure 11. GCMS D100.

Table 6. ‘GC-MS’ information of WPF20D80.

Peak	Hold-up time (mins)	Content (%)	Compound designation (Variety)	Chemical compound
1	8.4	2.13	Tridecane	C13 H28
2	14.6	2.09	Pentadecane-2,6,10,14-tetramethyl-	C19 H40
3	21.0	2.76	Heptacosane	C27 H56
4	21.0	2.76	Ethanol-2-(octadecyloxy)-	C20 H42 O2
5	21.5	1.64	Octadecanoic acid, methyl ester	C19 H38 O2

Table 7. ‘GC-MS’ details of WPF30D70.

Peak	Hold-up time (mins)	Content (%)	Compound designation (Variety)	Chemical compound
1	7.2	–	Phenol-3-(1-methylethyl)-	C9 H12O
2	7.2	–	Phenol-4-(1-methylethyl)-	C9 H12O
3	8.4	1.70	Tridecane	C13 H28
4	10	13.8	Tetradecane	C14 H30
5	11.6	1.19	Pentadecane	C15 H32

Table 8. ‘GC-MS’ information of D100.

Peak	Hold-up time (mins)	Content (%)	Compound designation (variety)	Chemical compound
1	3.1	0.75	Cyclohexane-1,1,2,3-tetramethyl-	C10 H20
2	3.1	0.75	Cyclooctane-1,4-dimethyl-trans-	C10 H20
3	3.3	1.22	Benzene acetic acid-6-ethyl-3-octyl ester	C18 H28 O2
4	3.3	2.16	Benzene acetic acid-2-tetradecyl ester	C22 H36 O2
5	3.4	0.94	Benzene-1,2,3-trimethyl	C9 H12
6.	5.8	2.36	Naphthalene decahydro-2-methyl-	C11 H2 O
7.	21.2	3.31	7-octadecanoic acid methyl ester	C19 H36 O2
8	25.4	2.72	Tetra cosane	C24 H50

Table 9. ‘GC-MS’ information of WPF20D70JB10.

Peak	Hold-up time (mins)	Content (%)	Compound designation (Variety)	Chemical compound
1	14.5	0.99	Heptadecane	C17 H36
2	21.1	3.64	9-octadecenoic acid, methyl ester	C19 H36 O2
3	21.1	3.64	11-octadecenoic acid, methyl ester	C19 H36 O2
4	21.5	2.79	Octadecanoic acid, methyl ester	C17 H38 O2

‘Gas Chromatography-Mass Spectrometry (GC-MS)’ method often acknowledged as the exact as well as precise analytical method aimed at detecting possible substances in a wide variety of organic liquids. The peaks observed in the GC-MS chromatogram are meticulously analyzed utilising software developed by the ‘National Institute of Standards and Technology (NIST).’ The identified compounds are systematically cataloged in Tables 6–9, accompanied by the coverage area with respect to total chromatogram area. This comparative assessment provides valuable insights into the relative concentrations of distinct compounds within the various samples, facilitating a thorough understanding of their chemical composition and characteristics.

Analogous to diesel, which is known to comprise a diverse array of aliphatic and aromatic compounds, in addition to fatty acid methyl ester constituents, diglycerides, and triglycerides (Pauls 2011; Sarker et al. 2012), the analyzed blends have been demonstrated to exhibit a highly intricate composition. This complexity highlights the multifaceted nature of these fuel blends, underscoring the importance of a comprehensive understanding of their chemical characteristics to optimise their performance and assess their environmental impact.

4.3. Measurements of engine’s efficiency and exhaust emissions

The variations in ‘Brake Thermal Efficiency (BTE)’ arising from utilisation of distinct test samples are depicted in Figure 12. The data demonstrates a positive correlation between BTE and the load carried for each fuel type. This phenomenon may be attributed to the enhanced turbulence and improved fuel mixing associated with higher load conditions. The investigation has revealed that the BTE of waste plastic fuel-diesel blend with 20% added jatropha biodiesel surpasses that of diesel itself, accounting for up to 66% of the load when compared across all fuel samples. This outcome may be a consequence of the reduced viscosity and increased oxygen content resulting from the incorporation of 20% jatropha biodiesel into waste plastic fuel-diesel blends (Chauhan et al. 2010). Under peak load conditions, the BTE values for WPF20D60JB20 and diesel were determined to be 36.31% and 36.45%, respectively.

Figure 12. BTE vs. Load.

Figure 13 delineates the influence of load on ‘Brake Specific Fuel Consumption (BSFC)’ for an assortment of distinct fuel samples. The idea behind BSFC refers to the amount of fuel needed to produce one unit of brake power, and it is closely tied to the thermal efficiency of the fuel in question as measured by Brake Thermal Efficiency (BTE) (Mani and Nagarajan 2009). This graphical representation offers valuable insights into the fuel consumption patterns and efficiency of the diverse fuel types under varying load conditions.

Figure 13. BSFC vs. Load.

The study has determined that among all the fuels tested, diesel has the lowermost ‘Brake Specific Fuel Consumption (BSFC)’ value, while the sample WPF30D40JB30 shows the highest BSFC value. Within the blended fuel samples, WPF20D60JB20 demonstrates the lowest BSFC, registering 0.230 kg/kW-hr, which is marginally higher than diesel’s value 0.217 kg/kW-hr. The reduced BSFC in the case of WPF20D60JB20 can be because of the enhanced mixing accompanied with increased load. Consequently, a smaller amount of fuel is necessitated for satisfying the power demand, reflecting the improved efficiency of this particular fuel blend.

Figure 14 presents the responsiveness of ‘Brake-Specific Energy Consumption (BSEC)’ in respect of varying load conditions for an array of fuel specimens. The BSEC serves to be valuable and objective metric employed to compare the energy input required to generate a unitary power for every specimen fuel. It’s noteworthy that BSEC displays a steady decrease with rising load for all the fuels under examination. Owing to unique heating values and specific gravities of each fuel, potential inaccuracies may arise when comparing fuel consumption between two distinct fuels with disparate combustion properties. In such scenarios, BSEC emerges as the most reliable measure for comparative assessments (Bajpai and Das 2010).

Figure 14. BSEC vs. load.

The figure illustrates that the BSEC is elevated for waste plastic fuel-diesel blends, and that the inclusion of jatropha biodiesel in these mixtures results in a reduction of BSEC values. For up to 66% load up condition, BSEC of WPF20D60JB20 is found to be less than diesel’s, and at higher loads, it is marginally greater than diesel, rendering it one of the most efficient blended fuel samples in terms of BSEC. Under full load operation, WPF20D60JB20 and diesel are found to exhibit BSEC values of 9.91 and 9.84 MJ/kW-hr, respectively, highlighting their performance characteristics in energy consumption.

Figure 15 delineates alterations in volumetric efficiency resulting from varying load conditions. When load escalates, ‘volumetric efficiency’ of specimen fuel exhibits a consistent decline. It is noteworthy that the ‘volumetric efficiency’ of the discarded plastic oil-diesel blend closely parallels that of diesel; however, incorporating jatropha biodiesel into the waste plastic fuel-diesel mixture leads to a diminished efficiency in the blend’s volumetric utilisation. This observation underscores the effect of jatropha biodiesel count on the operating properties of the fuel blend under different load scenarios.

Figure 15. Volumetric eff. Vs. load.

Figure 16 presents the fluctuations in heat dissipation with respect to loading. It has been discerned that waste plastic fuel-diesel mixtures exhibit a more rapid heat release rate in comparison to diesel in isolation. Integration of jatropha bio-diesel into the discarded plastic oil-diesel blend significantly mitigates the rate of heat release. Remarkably, the waste plastic fuel-diesel blend comprising 20% jatropha biodiesel demonstrates a heat release rate even lower than that of diesel. Extended ignition delays may have a bearing on the elevated heat release rate observed in the waste plastic fuel-diesel blend, shedding light on the performance dynamics of these fuel mixtures.

Figure 16. Cumulative Gross HRR vs. load.

Figure 17 illustrates the correlation between load and Exhaust Gas Temperature (EGT) for various fuel specimens. As per the observation discarded plastic oil blended with diesel exhibits a lower EGT compared to diesel alone. However, blends containing jatropha biodiesel display an increase in EGT values. Elevated exhaust temperatures can adversely impact an engine’s thermal efficiency (Agarwal and Rajamanoharan 2009), as they result in substantial heat loss, originating in the combustion zone and extending outward. The CHNS analysis, as presented in Table 4, suggests that the heightened oxygen content in the jatropha biodiesel-enhanced fuel sample may be responsible for the increased EGT. Further examination of data in Table 4 shows that greater oxygen content in blends incorporating jatropha biodiesel may account for their higher EGT values when compared to discarded plastic oil-diesel mixtures. Mixing of bio-diesel in diesel augments net oxygen content, consequently facilitating more efficient combustion.

Figure 17. EGT vs. load.

In the case of the jatropha biodiesel fuel sample, the lower diesel index and, subsequently, cetane number, results in an accumulation of greater fuel during the premixing phases of combustion. This accumulation, in turn, contributes to the elevated EGT values observed in the fuel sample. This intricate relationship between oxygen content, diesel index, cetane number, and EGT provides a comprehensive understanding of the performance characteristics of these fuel blends under varying load conditions.

Figure 18 shows the variation air–fuel ratio (A/F) with load in the context of fuel combustion. Within each cylinder of a compression ignition (C.I.) engine, a spatially and temporally varying distribution of fuel persists throughout the entire combustion process. The proportion of oxygen to nitrogen in the air during combustion plays a crucial role in the formation of pollutants, emphasising the significance of the air–fuel ratio in determining the engine’s environmental impact and overall performance characteristics.

Figure 18. A/F ratio vs. load.

4.4. Characteristics of the emission

Figure 19 illustrates the changes in hydrocarbon emissions as a function of load for a diverse range of sample fuels. Hydrocarbons can exist in both gaseous and solid forms, with the former being referred to as gaseous hydrocarbons and the latter as particulate matter (PM) (Mani, Nagrajan, and Sampath 2010). This distinction is crucial for understanding the environmental impact of hydrocarbon emissions under various load conditions and with different fuel compositions.

Figure 19. Alterations of HC emission with load.

Hydrocarbon emissions have been observed to be lower in waste plastic fuel-diesel blends, particularly in WPF30D70, when compared to diesel. However, emissions tend to increase when incorporating 10% or 20% jatropha biodiesel into the mixture. Interestingly, the waste plastic fuel-diesel blend with 30% jatropha biodiesel exhibits the lowest hydrocarbon emissions among all the tested fuels. A plausible explanation for such occurrence may be the heightened oxygen presence within biodiesel–diesel blends facilitates more complete combustion. As noted by Rao et al. (2009), hydrocarbon releases are minimised at fractional loadings while they escalate with increased loadings notwithstanding fuels studied. The above trend can be attributed to the engine operating at a higher equivalence ratio, leading to an oxygen deficiency (Bajpai and Das 2010). Thus, the complex interplay between fuel composition, oxygen content, and engine load contributes to the observed variations in hydrocarbon emissions.

Figure 20 illustrates the variations in carbon monoxide release which is dependent on load for distinct test specimens. Carbon monoxide, an odorless and tasteless gas, poses significant toxicity risks. Regarded as both a tangible emission constituent and an indicator of squandered chemical energy, CO is generated in combustion engines employing fuel with elevated equivalence ratios. The dearth of oxygen precludes comprehensive combustion of the fuel, culminating in the formation of carbon monoxide.

Figure 20. CO emissions vs. load.

An escalation in load across all fuels corresponds to diminished CO emissions. This phenomenon can potentially be attributed to the lower cylinder temperature prevalent under reduced load, which subsequently increases when augmented fuel injection is necessitated to satisfy the burgeoning demand. Enhanced fuel combustion efficiency at elevated temperatures consequently results in decreased carbon monoxide production, thereby contributing to improved engine performance. It is important to note that CO emissions in diesel engines are influenced by the physicochemical characteristics of the fuel, the air-to-fuel (A/F) ratio, and the engine temperature (Puhan et al. 2005; Altun, Bulut, and Oner 2008; Wu et al. 2004).

Experimental findings reveal that blends comprising waste plastic fuel and diesel, along with those incorporating jatropha biodiesel, exhibit reduced carbon monoxide emissions compared to diesel in isolation. The innate presence of oxygen in jatropha biodiesel suggests that substituting a minor proportion of diesel with this biofuel in waste plastic fuel formulations contributes to diminished CO emissions. Blends composed of waste plastic fuel and diesel, with a 30% jatropha biodiesel content, demonstrate the most favourable carbon emissions reduction. Possible explanations for this observation in the case of WPF30D40JB30 encompass enhanced atomisation and mixing processes.

Figure 21 presents the variations in NOx emissions as a function of load. Nitrogen oxides, comprising predominantly nitrogen monoxide (NO) and a minor proportion of nitrogen dioxide (NO2), are discharged in significant quantities by combustion engines, with concentrations reaching up to two thousand parts per million. The NOx family encompasses an array of nitrogen-oxygen compounds. NOx emissions are particularly undesirable due to their propensity to react and generate ozone within the atmosphere, thereby contributing significantly to photochemical smog. This harmful gas, resulting from the interaction between ambient air and automobile exhaust, raises considerable environmental concerns. As NOx decomposes, it releases both nitrogen oxide and elemental oxygen, which subsequently forms ozone. This ground-level ozone proliferation leads to annual crop losses, further emphasising the need for effective mitigation strategies.

Figure 21. NOx emissions vs. load.

Oxygen abundance and elevated temperatures serve as the key catalysts in the birth of nitrogen oxides (NOx) (Venkanna, Venkataramana Reddy, and Wadawadagi 2009). This intriguing phenomenon arises from the propensity of nitrogen and oxygen to engage in a passionate chemical reaction at soaring temperatures, thereby producing the diverse NOx family. NOx emissions are strongly influenced by fuel-dependent factors such as droplet size, penetration rate, spray characteristics, evapouration rate, and the extent of air mixing (Mallikappa, Reddy, and Murthy 2012). Each of these parameters may play a significant role in shaping the production of NOx within combustion processes.

The graphical representation demonstrates a direct proportionality between NOx emissions and engine workload. For diesel, the maximum NOx emissions are observed at both half load and peak load scenarios. The NOx emission outcomes for waste plastic fuel-diesel blends containing 10% and 20% jatropha biodiesel exhibit satisfactory performance. Under full load conditions, NO emissions are quantified at 1313 ppm for diesel and 1260 ppm for the WPF20D60JB20 blend.

Figure 22 illustrates the variation in CO₂ emissions with load for multiple test fuels. As anticipated, a rise in CO₂ emissions was observed with an increase in load across all fuels tested. Carbon dioxide (CO₂), a combustion byproduct, often permeates the atmosphere. Ideally, the combustion of hydrocarbon fuel should yield only carbon dioxide (CO₂) and water vapour (Kumar, Mishra, and Roy 2022a, 2022b; Nabi, Hoque, and Akhter 2009). Among the fuels examined, diesel exhibited the highest CO₂ emissions. The incorporation of jatropha biodiesel into waste plastic fuel-diesel blends does not significantly influence CO₂ emissions, as indicated by the graph. This may be attributable to partial oxidation stemming from the slow combustion of fuel (Mani, Nagrajan, and Sampath 2011).

Figure 22. CO₂ emissions vs. of load.

5. Conclusions

The principal objective of this study was to examine the implications of incorporating jatropha biodiesel into waste plastic fuel-diesel blends. The key findings of this investigation can be succinctly outlined as follows:

1. All fuel samples containing jatropha biodiesel exhibit decreased viscosities compared to diesel, with WPF20D60JB20 demonstrating the lowest viscosity. As reported, the viscosity of WPF20D60JB20 is 25% lower than that of diesel. The integration of jatropha biodiesel into waste plastic fuel-diesel blends reduces the mass flow rate of fuel injected into the cylinder, attributable to the diminished density of the resultant mixture. Incorporating up to 20% jatropha biodiesel diminishes the flash point in comparison to waste plastic fuel-diesel blends; conversely, the inclusion of 30% jatropha biodiesel raises the flash point above that of waste plastic fuel-diesel blends.

2. The investigation of jatropha-blend fuel samples revealed elevated ignition temperatures compared to conventional diesel fuel, indicating that these jatropha-fortified mixtures can be securely transported and stored. Additionally, the incorporation of jatropha biodiesel into waste plastic fuel blends results in a decreased acid value, thereby mitigating the potential for engine corrosion and acidic deposits. A notable observation is that the fuel sample containing a 20% higher proportion of jatropha biodiesel exhibited a 26% reduction in acid levels compared to other waste plastic and biodiesel mixtures. Furthermore, the analysis demonstrates that incorporating up to 20% jatropha biodiesel in waste plastic fuel-diesel blends has a negligible impact on the diesel index, an essential metric for assessing fuel ignition quality. In contrast, blends containing up to 30% jatropha biodiesel exhibit a substantial influence on the diesel index. Consequently, it is advised against utilising more than 20% jatropha biodiesel in these mixtures, as the diesel index is a critical indicator of a fuel’s ignition performance.

3. The Fourier Transform Infrared (FTIR) spectroscopy results of the fuel samples indicate that diesel, biodiesel, and their respective blends can be utilised as high-quality fuels, as they exhibit common functional groups. Furthermore, Gas Chromatography-Mass Spectrometry (GC-MS) analysis of the various fuel samples reveals the presence of diglycerides, triglycerides, and esters, as well as aliphatic and aromatic compounds. This collective evidence underscores the potential for these blends to serve as effective and reliable fuel alternatives.

4. Engine performance tests reveal that waste plastic fuel-diesel blends with 20% additional jatropha biodiesel (WPF20D60JB20) exhibit superior thermal efficiency compared to other fuel samples, with the exception of peak load conditions. WPF20D60JB20 demonstrates a thermal efficiency of 36.31% while diesel yields 36.45%. Additionally, WPF20D60JB20 exhibits the lowest Brake Specific Fuel Consumption (BSFC) among the tested samples and a reduced Brake Specific Energy Consumption (BSEC) compared to diesel at peak load, with values of 9.91 and 9.84°MJ/kW-hr, respectively. However, it is important to note that jatropha biodiesel lowers the volumetric efficiency and heat release rate of waste plastic fuel blends.

5. Fuel blends incorporating jatropha biodiesel have been observed to yield higher hydrocarbon (HC) emissions relative to blends consisting of waste plastic fuel and diesel. The fuel samples investigated in this study comprise mixtures of waste plastic fuel and diesel, as well as jatropha biodiesel and waste plastic fuel. Notably, the blend WPF20D60JB20 has been found to emit 32% more HC compared to diesel under peak load conditions.

6. When jatropha biodiesel is integrated with waste plastic fuel, a reduction in carbon monoxide (CO) emissions is observed. Under full throttle conditions, the blend WPF20D60JB20 emits 20% less CO compared to diesel. Additionally, blends utilising jatropha biodiesel exhibit significantly lower NOx emissions relative to diesel. The incorporation of jatropha biodiesel into the blends does not appear to have a measurable impact on CO₂ emissions, with both blend types demonstrating lower CO₂ emissions than diesel. Furthermore, diesel samples supplemented with jatropha biodiesel, which inherently contains oxygen, exhibit increased exhaust gas temperatures (EGT).

7. Upon thorough analysis of the data gathered from the various tests performed on the fuel samples, the results substantiate that the blend containing 20% higher proportion of biodiesel compared to diesel (WPF20D60JB20) emerges as the most favourable option.

Disclosure statement

No potential conflict of interest was reported by the author(s).