Cutting Fluids Usage and Impacts in Metal Workshops in Ibadan, Southwestern Nigeria

3.1 Identification of cutting fluids users/ suppliers/ producers in Ibadan

There are no metal cutting workshops in Ido, Ona Ara, Ibadan Southeast, and Ibadan Northwest local governments. Table 1 shows the details of the visited metal workshops.

3.2 Mode of ownership of metal workshops

The 103 metal workshops visited have different modes of ownership i.e., Governmental/Institutional based workshops, privately owned workshops, and industrial-owned workshops. Figure 1 represents the percentage of the mode of ownership of various metal workshops in Ibadan. Among the industrial-owned metal workshops (2.91% representing 3 workshops) are manufacturing, construction, and automobile-based companies. Government-owned metal workshops (7 workshops altogether) are institutionally based workshops that are provided to expose students to practices that embody production, automobile, and metallurgical engineering. There are 93 privately owned metal cutting workshops altogether. As earlier mentioned, there are majorly three types of metal cutting operations being carried out in Ibadan, Oyo State, Nigeria. They include (i) Fabrication, which entails machining operations such as turning, milling, grinding, drilling, threading, facing, and boring. It is the most practiced metal cutting operation in the city (ii) Crankshaft machining; operations carried out include turn-turn broaching, spigot flange and journal machining, end hole and counter boring, external milling, internal milling, turning, and broaching of thrust wall, broaching, end hole and counter boring, and cutting to length and centering. (iii) Block boring operations conducted among metal workshops in Ibadan are engine block boring, engine block surfacing, spot facing, bearing cap conversion, blind hole operations, cylinder chamfering, thread milling freeze plug holes, block lighting, centering, and block engraving. In the case of the crankshaft and block boring operations, not all the workshops perform the whole operations listed above but a larger percentage of the workshops perform all the activities. This is due to a lack of necessary facilities and technicalities.

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Figure 1. Mode of ownership of machining workshops in Ibadan

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Figure 2. Analysis of coolants/lubricants used in the workshops

Table 2 shows the number of each metal cutting workshops by their respective local governments. In every local government, fabrication workshops greatly outnumbered the crankshaft and block boring workshops. From the chart, Akinyele, Oluyole, and Ibadan North local governments have an equal number of the crankshaft and block boring workshops. This is because most of the workshops that fall into the local government areas carry out these two operations. Virtually all the crankshaft operators perform block boring work since they are automobile-related operations. Out of the 103 metal cutting workshops, 63 carry out fabrication operations only, 5 perform crankshaft operations, crankshaft, and block boring operations (13 workshops), fabrication and block boring (1 workshop), fabrication and crankshaft operations (3 workshops), and 18 of the workshops do the three operations. None of the workshops does block boring operations alone. Ibadan Southwest has the highest number of workshops for all three operations. Ogunpa, Oke-Bola, and Idikan areas are popularly known to have the best metal working operators in Ibadan. They are highly rated by most vehicle and truck mechanics in the city when repair work is to be carried out, especially on the crankshaft and block boring works. However, they fabricate different things such as local grinding machining, pelletizing machines, extruders, and prototypes of machine components.

3.3 Types of cutting fluids used for metal cutting operations and their management

Research visits to the 103 metal workshops in Ibadan showed that machine operators do not use the commonly used cutting fluids designed for machining purpose alone. They also make use of other fluids, and these fluids pose serious threats to human health and the environment after disposal. Various types of cooling/ lubricating fluids that are been used in the visited metal workshops in Ibadan include soluble oil (mineral oil-based cutting fluid), kerosene, used engine oil, water and detergent, vehicle radiator coolant, palm oil (food cooking oil), diesel, compressed air, and water only. Table 3 shows the number/percentage of the users of the cooling/lubricating fluids listed earlier.

Most of the workshops make use of soluble oil as cutting fluids due to its long-term use [9]. Despite the complaints of its high cost of purchase, they still prefer it to other fluids because it gives a good surface finish, longer tool life, corrosion reduction, etc. Several respondents admit that they consider alternative fluids when customers are not ready to pay for a good work forgetting the consequences of these fluids on their health, environment, cutting tools, and workpiece materials. Some machine operators use more than one fluid for cutting operations. A respondent from Ibadan North local government reported that cooling/lubricating fluid is workpiece and cutting operation dependent. He emphasized that during tapping and die operations, used engine oil is applied to lubricate since he cannot afford to buy straight cutting oil for a small pay job. Another respondent at a workshop in Akinyele local government said he does not see the need for using soluble oil for every machining operation. In his words, 'Any lubricating oil is metalworking oil'. He explained that he has used engine oil and palm oil for tapping operations severally, kerosene for machining cast iron, and vehicle radiator coolant in situations where other lubricating oils are not readily available. He confessed that in some machining works with little payment, he uses water as a coolant even though it rusts both the workpiece and the machine tool being used. The analysis of lubricants/cooling agents used is shown in Figure 2. From the analysis, the fabrication workshops have the chance of using more fluids than crankshaft and block boring workshops. The most used fluid in fabrication workshops is soluble oil. Over 72 percent of the machine shops use soluble oil for machining to reduce the cost of tooling and meet the life expectancy of their machine tools. During the field visits, quite some machine tools are aged due to machine operators' improper selection of cutting fluids. Diesel and soluble oil have equally been used in crankshaft operations. In the interviews with a few crankshaft operators that use diesel for machining, they explained that diesel is preferable to soluble oil for two reasons; first, soluble oil is more expensive than diesel. A liter of soluble oil costs ₦2,400.00 (5.72 US dollars) while diesel on the other hand is ₦800.00 (1.91 US dollars) per liter. It was reported that machining with soluble oil makes the workpiece dull after machining. Moreover, if such a crankshaft is not being used for its purpose immediately, rusts begin to occur. In block boring workshops, used engine oil is more frequently applied for cutting operations. Soluble oil and kerosene are used as a substitute if used engine oil is not available. From their views, used engine oil is the best for block boring operations.

3.4 Mode of application of cutting fluids

The majority (59%) of the workshops use the automated (flooding method) mode of application of fluids. 34 percent of the total workshops adopt the manual mode of the application using bottles for fluid storage. The remaining workshops take both manual and automated modes of application. Most of the operators practice the manual method when the in-built pumps of their machines stop working. Another reason pointed out was that the application of cutting fluid manually is more economical in the sense that a lesser volume of cutting fluid is required for machining. A sump tank can contain about fifty litres of emulsified fluid at a time. If a machine shop is to consider the automated way of application, the minimum quantity of soluble oil that can be used for the concentration is one liter. Only a few drops of soluble oil are needed for a manual method with bottles. Therefore, some people count the flooding method as a waste of resources. None of the machine workshops practice the minimal delivery mode of fluid application popularly known as minimum quantity lubrication (MQL). MQL refers to total use without residue, applying lubricants between 10 to 100 ml/h [10, 11].

3.5 Management practices of soluble oil

The study has focused mainly on the management practices of soluble oil as a cutting fluid. The set of questionnaires used for this survey work was prepared for the assessment of cutting fluids designed for machining purposes. Diesel, kerosene, used engine oil, etc. are not designed for machining. Diesel serves other purposes like fueling cars, trucks, and generators. Kerosene on the other hand is an important household fuel for stoves, lanterns, and furnaces [12]. The management practices involve the consumption of soluble oil, monitoring of soluble oil, disposal methods of soluble oil, how long soluble oil takes before disposal, and treatment of spent soluble oil before disposal [13]. All information collected on management practices of soluble oil are provided in Tables 4-10.

Table 1. Distribution of machining workshops in Ibadan by Local Government

Table 2. Types of machining workshops in Ibadan by Local Government

Table 3. Cutting fluids used according to the number of workshops

Table 4. Soluble oil management in Ibadan Southwest Local Government

Table 5. Soluble oil management in Egbeda Local Government

Table 6. Soluble oil management in Lagelu Local Government

Table 7. Soluble oil management in Oluyole Local Government

Table 8. Soluble oil management in Akinyele Local Government

Table 9. Soluble oil management in Ibadan Northeast Local Government

Table 10. Soluble oil management in Ibadan North Local Government

By comparison, using Figure 3, Ibadan Southwest (IBSW) has the highest volume of consumption of soluble oil. This is because it is the center for machining activities in Ibadan. However, it has the largest number of workshops with a total of 37 metal workshops. Results have proved that the number of workshops does not guarantee the amount of soluble oil consumed by some local governments. Lagelu local government has four workshops, and it consumes more soluble oil than Egbeda and Oluyole local governments. Lagelu local government has an automobile company that consumes a large quantity of soluble oil in her cutting operations. The total average volume of soluble oil consumed monthly in Ibadan; Nigeria is 402 litres.

The quantity of soluble oil given is the quantity of soluble oil before emulsification i.e., before mixing with water at different ratios. The quantity after concentration cannot be feasible if this study should cover that. Virtually all the workshop operators do not take an accurate measurement of their concentration when preparing their cutting fluids. Assuming water to concentrate (soluble oil) in a ratio of 20 to 1 [14]. Now, from one gallon (4 litres) of concentrate, you have 20 gallons (80 litres) of the emulsified compound to dispose of. With this assumption and ignoring cutting fluids lost during operations due to splashes. Table 11 shows the average volume of soluble oil consumed before machining and the average volume of spent cutting fluids generated by local governments. The volume of consumption varied from as little as 1 liter to as high as 25 litres monthly. Soluble oils are sold in different packages such as gallons (4 litres), Jerry cans (20 litres), and drums (200 litres). Soluble oil in a gallon is the most purchased among the three packages. Drums are used mostly by the industrial sectors. From the survey, it was found that price of 20 litres of soluble oil is 48,000 naira (114.42 US dollars).

3.7 Mode of disposal of spent cutting fluids in Ibadan

Machine operators in Ibadan have seven (7) ways of disposing of spent cutting fluids as shown in Figure 4. This includes pouring in the river, ground, storm drainage (gutter), in a dung hole, highway, environmental agency, and bushes. Among the 79 metal workshops that use soluble oil, 3 workshops pay to environmental agencies for disposal, 36 disposed of on the ground, 12 pour spent fluids in the river or stream, 4 dispose of in the bush, 22 use storm drainage, 2 workshops dispose on the highway, 1 workshop prefers pouring in a dung hole. Only 7 workshops responded to not changing their used cutting fluids, they top when there is a reduction of fluid in their sump tanks.

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Figure 3. Amount of soluble oil consumed monthly at each local government

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Figure 4. Number of workshops adopting various modes of disposal

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Figure 5. Percentage number of workshops responses to treatment of spent cutting fluids before disposal

Table 11. Estimated quantity of cutting fluids consumed monthly in each Local Government area

3.8 Treatment of spent cutting fluids before disposal

Out of 79 metal workshops using soluble oil for machining, 71 responded to not treating spent cutting fluids before disposal, 3 workshops do the treatment while 5 workshops do not dispose of spent cutting fluids at all. Figure 5 shows the percentage number of workshops that responded to YES, NO, and category of workshops that do not dispose of cutting fluids (no replacement). Those in this category top the fluids in their tanks when there is a need to. 

3.9 Monitoring checks/ length of emulsion cutting fluids in Ibadan

The workshop operators have adopted two means of monitoring emulsified oil before disposal: visual and odor monitoring. Visual monitoring is a situation whereby the color of the emulsion cutting fluids changes from white to brown and is observed manually by the sighting. On the other hand, staled emulsion cutting fluids smell irritating like a rotten egg smell. None of the workshop operators responded to the refractive index test, pH test, and bacterial test. It was found that 55% (44 workshops) monitor their emulsion fluids visually, 15% (12 workshops) do odor monitoring, 16% (13 workshops) use both visual and odor monitoring while the remaining 14% (10 workshops) either dispose of spent cutting fluids immediately after machining or top the tank for next operation. The average length/duration of emulsion cutting fluids before disposal ranges from one day to 4 weeks as summarized in Table 12.

Table 12. Duration of emulsified oil before disposal

According to some of the operators, the length of emulsified oil depends on the frequency of time the machine tool runs. The more the machine tool runs, the longer the life of the emulsion cutting fluids. When the machine tool is idle for a few days, it affects the emulsion cutting fluids in the sump tank, thereby resulting in a rotten egg odor. It was also reported that the color of the cutting fluids changes mostly when there is a mix-up with leakage of tramp oils (oils used for lubrication of the machine components such as gearbox oil and machine ways oil). The emulsion cutting fluids can stay longer than one month provided machine operators can carry out some monitoring tests on their oils. From research observations, factors leading to early disposal of emulsified oil include but are not limited to contact of the emulsion cutting fluids with microbial organisms e.g., bacterial and fungi, exposure of oil sump tanks to atmospheric impurities and workshop residue e.g., chips and filings, mixing of soluble oil with filthy water, and non-adherence to best practices governing workshop management. These factors can be caused by using unclean water for fluid mixture and dilution, dipping of hands into fluids during fluid preparation, chips that come off the machine when a metal is being machined, tramp oils, and full/partial exposure of sump tanks of machine tools. Almost 100% of the machine operators responded positively to dipping hands into the solution during the fluid mixture. If at the time of mixture, the operator's hands are dirty, it will bring bacteria into the emulsion cutting fluids. An investigation of machine tool sump tanks condition shows that many of the machines are old, and their sump tanks are either partially covered or exposed. Exposure of soluble oil to air is an opportunity for bacteria to enter and multiply in millions. Figure 6 shows exposed sump tanks of two workshop lathe machines. As the sump tanks are exposed, excessive bacteria, tramp oil, chips, or wastes can seep into and contaminate the cutting fluids easily. Contaminated cutting fluids lead to terrible damage to the machine tools which often have dire financial implications for machines. Contaminated machine coolant eats rubber, plastic, Plexiglas, insulation, and human flesh.

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Figure 6. (a) Exposed machine sump with three weeks emulsion cutting fluid (b) Exposed machine sump with five months emulsion cutting fluid

3.10 Awareness of safety and occupational hazards

This study determined the perception of occupational hazards and health problems among the 343 machine operators that were interviewed. Cutting fluids are complex in their compositions so therefore they may be irritant and allergic to the users [15-17]. The majority (268 operators) were not aware that machining with cutting fluids has serious health concerns. The lack of awareness of this danger has resulted in health problems in different parts of their bodies. This low awareness results in exposure of operators to potentially dangerous chlorinated paraffin compounds, inhalation of mist or aerosol without nose covers, wearing of cutting fluids-soaked clothes, manual mixing of cutting fluids, and cleaning of machines sump tanks with bare hands. Table 13 shows awareness of hazards and safety measures in the workshops among respondents.

Table 13. Awareness of hazards and safety measures in the workshops among respondents

Data analysis of the awareness of safety and occupational hazards revealed that 78.13% of the operators were unaware of the dangers involved in the use of cutting fluids while 21.86 (75 operators) were aware of it. The operators in the industrial and academic sectors are the ones who often use protective devices, as they regard safety first in their organizations. Likewise, some privately owned operators with previous working experiences in industries still engage in the frequent use of safety devices. A larger number of the operators have never used safety devices before as they see no reason for using them. Some of their excuses for not using safety devices are: (i) Devices are not provided by their workshop operators (employers) - They claim that in most organizations, it is the employers that provide safety devices. (ii) Devices are not convenient – They complained that a lot of heat is generated when machining and the poor ventilation causes some discomfort to them. Only a few of the workshop operators use fans. (iii) Devices not necessary – 78 operators responded that the use of safety devices is not needed in the workplace. The operators were without clothes in Figure 7 as they complain of harsh weather. Workshop buildings with no artificial cooling systems have hot conditions in the summer season and some operators may start to experience some degree of discomfort.

3.11 Effect of cutting fluids on machine Operators’ health

Cutting fluids are widely employed to carry away the heat in machining, but their usage creates a threat to the health of workers. Regular contact with cutting fluids with the skin may lead to skin dermatitis. Moreover, the inhalation of the mist may cause some respiratory irritations to human health. Soluble oil belongs to a class of oil called mineral oil. There are a group of problematic substances that are included in mineral oil formulations such as nitrosamine, formaldehyde condensate materials, organic chlorine-containing substances, organic phosphorus-containing substances, polycyclic aromatic hydrocarbons (PAH), and others [18]. Soluble oil, diesel, kerosene, and used engine oil are all extracted from crude oil. These cutting fluids have different effects on human health and the environment. Some of the effects are listed in Table 14. The exposure of machine operators to all these fluids has resulted in several health problems. Our findings revealed that 137 operators had dizziness, 22 had got rapid heartbeat rate, 113 had a headache, 135 had the burning skin, 131 had coughing, 172 had itching, 101 had red and watery eyes, 127 had a skin rash, 34 experienced hysteria (confusion), 39 had difficulty in breathing, 139 had a running nose, 130 had a sore throat, 27 had nose bleeds, 324 had cuts on the skin and 169 had electric shocks. There was no record of cancer, asthma, and lung diseases. This might be because; the operators are not informed of these diseases. The percentage breakdown is shown in Figure 8.

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Figure 7. Machine operators at some workplaces without personal protective devices

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Figure 8. Health-related problems among operators

The most common health-related problem operators had was cuts on the skin. Hot flowing chips that come out during the cutting process result in wounds on the operator's skin. The danger with these cuts is that cutting fluid splashes may penetrate the inner flesh and lead to serious skin problems in the long run. Coughing, sore throat, and a running nose can be because by inhalation of cut fluids without the use of nose covers. Itching and skin rash are frequent among all the workers regardless of the cutting fluids (diesel, kerosene, used engine oil, and soluble oil) being used. The problem with most operators is that they do not have sufficient water to clean their bodies after daily activities. The majority had spoken that they only wash their hands after the close of business. Burning of skin is very rampant among the workers as this exists in almost every workshop. Poor ventilation and lack of sufficient water will to some extent increase the burning of skins. Rapid heartbeat rate, hysteria (confusion), and difficulty in breathing mainly exist among the diesel and kerosene users of cutting fluids. These fluids are very harmful as described by a few operators. An apprentice of a workshop using diesel for lubrication reported that once it is 5:30 p.m., his boss discontinues all machining tasks till the following day because the use of diesel as cutting fluid has affected his eyes (he hardly sees clearly in the evening). A different person said that diesel makes the hair on his skin varnish each time he tries using it. Occupational symptoms like red and watery eyes, headache and fatigue, and dizziness have been associated with inhalation of mists/smoke/vapor from machining. 168 (49%) machine operators answered positively about electric shock in the workplace environment. Electric shocks are mostly caused by naked wire lying on the machine components. However, health problems such as cancer, lung diseases, and asthma were nil. The absence of these is probably due to the operators not being well informed. In this study, a larger percentage of the worker spent a maximum of 8 hours at work and some work less than 8 hours which correspond with the normal 8-hour workday standard term exposure limit. Some of the workers spent more than 8 hours/day and work for 6 days a week. Those that spent more than 8 hours per day may experience more stress at the end of the day and this can also increase the risk of health problems at workshops.

3.12 Effects of improper disposal of cutting fluids on the environment

Cutting fluids are an obvious visible form of pollution. It harms plants and animals, destroys aquatic life in rivers and streams, and damages the soil. When machine operators are not cautious in disposing of properly spent cutting fluids, plants and animals are adversely affected. Many animals are poisoned, become ill, and die each year due to machine operators' carelessness with spent cutting fluids and chips. Animals absorb fluids and chips operators’ litter in the environment such as a river, storm drainage, and ground through consumption of polluted plants [19]. Biomagnification (which means progression in the degree of concentration of toxins in organisms along each step of the food chain from plankton to humans) occurs along each step of the food chain posing a great threat to the environment. Most animals accrue chemicals through ingestion, absorption through the skin, and inhalation. If a chemical is not degraded naturally, it can remain in the environment for hundreds of years. Cutting fluids such as diesel, kerosene, used engine oil, and soluble oil, are non-degradable cutting oils. If these substances/fluids are consumed by an organism such as a bacterium or algae, they cannot be broken down or excreted. Further consumption of these harmful fluids accumulates in the organisms' bio-system to the extent that, over time, the level of the toxins in the organism becomes greater than the level in the environment. When the bacterium or algae is then consumed by another organism, the new organism inherits its prey's toxins [20, 21].

If the spent cutting fluid drains into a water body e.g., a stream, it precipitates down to the bottom and along the channel of the water body polluting and infiltrating the bio-systems of living organisms along its path. Bioaccumulation and bio-mutation often arise leading to deformity of fish species and other aquatic life leading eventually to death. Most of what runs off into our streams and rivers originate from the surrounding layers of the earth. Disposal of spent cutting fluids on the ground will eventually end up in our rivers, drinking water, or probably in our foods. Plants can take up toxic chemicals from soil contamination. These toxins then bioaccumulate through humans eating the plants directly or consuming another animal that has eaten the plants. In one way or the other, we all have consumed certain toxic substances. Some are broken down and excreted while others bio-accumulates [20, 22]. Up till now, the results of bioaccumulation are not well understood in humans. It is suspected to cause various cancer, low sperm counts, immune system problems, learning disabilities, and birth defects. However, everything that goes into the storm drainage goes into a river and eventually the ocean. As the toxins in our environments continue to accumulate, more problems are likely to develop in the future. Quite a several machine operators in Ibadan disposed directly of their spent soluble oil, diesel, kerosene, used engine oil, and chips into the river. This has affected the aquatic life in some major rivers in Ibadan e.g., the Ogunpa river. During the survey, ten workshop operators in IBSW local government said they dispose of fluids in the Ogunpa river. This river flows continuously until it flows as a tributary into another river which flows into the ocean. Presently, the river is a polluted murky poignant river, and machine operators have contributed immensely to its state through fluids and chips disposal. Figure 9 shows some of the disposal sites where cutting fluids are disposed of by machine operators (in the river, stream, and ground). The spent cutting fluids that is been discharged on the ground in the figure below had spent eight months in the machine sump before final disposal. Long storage of cutting fluid in the machine sumps leads to nitrosamine [23]. Nitrosamines are carcinogens (cancer-causing agents). Many of the workshops are in the wrong places since there are no restrictions on their locations. They are located near rivers, living environments, shopping complexes, and even close to some restaurants. Some are also located close to people's farms. In Ibadan, a couple of fish farmers use some of these rivers and streams as the source of livelihood for their fish. Greater complications are envisaged in the nearest future for the lives of aquatic animals if inappropriate disposal of spent cutting fluids into streams and rivers persists. For example, some years ago, about 74 percent of the squawfish in the Willamette River had deformities [20, 24]. These deformities are believed to be caused by exposure to toxic chemicals.

3.13 Evaluation of metal workshops coordinates using ArcGIS platform

The coordinates of all-metal workshops were collected with a GIS device as earlier discussed. Those coordinate points (longitude and latitude) were carefully fixed in an excel sheet and subsequently fixed on the drainage map of Ibadan using ArcGIS software. The drainage map showing the location of the 103 visited metal-cutting workshops in Ibadan is given in Figure 10. Not all the locations of the workshops eventually showed in the drainage map due to overlapping of some points. Some workshops are very close to each other during the survey. Their closeness results in overlapping on the drainage map.

To gain a full understanding of the map, the legend in the lower part explains better. The red stars show the location of the workshops that fall outside the buffer, the black dot shows the location of the settlement in which the workshop belongs, and the green dot represents the workshops that fall within the 40 meters, 80 meters, and 120 meters buffer while the green line represents the river. After the analysis, the workshops that fall within the 40, 80, and 120 meters to the river are summarized in Table 15. There are thirty-nine (39) workshops within the buffer of which seventeen (17) are within 40 meters from the river/stream, also (17) are found at 80 meters and the remaining (5) are 120 meters away from the river. The 39 workshops are situated around fifteen (15) rivers such that 5 workshops are close to Agodi river, Ogunpa (11), Omituntun (2), Popoyemoja (1), Olosun (2), Sango (2), Odo-ona (1), Alalubosa (1), Oke bola (1), Idi kan (6), Akilapa (2), Podo (1), Oke seni (1), Oluyole (1) and Barika River (1). Some of these rivers are linked to each other. For example, Ogunpa, Oke seni, Oke bola, Idi-kan, Akilapa Rivers are linked together by river basins. Similarly, there is a link between Odo-Ona, Oluyole, and Podo Rivers. The more the linkages of these rivers, the more the toxicity of the spent cutting fluids will surround the rivers and the more contamination the rivers to aquatic animals.

The toxicity of the fluids disposed of in rivers will affect the water bodies (pipe-borne water, bore-hole water, and well) in those environments within the 120 meters buffer. Most fish farmers around Popoyemoja River depend on the water from the river for their fish survival. They explained that they have a great loss every season due to water pollution. The poor water affects the health of their fish thereby taking several months for those that will survive to grow.

Table 14. Effects of cutting fluids on human health [25, 26]

3.14 Possible mitigation against prevalent abuses in metal work operations

According to the conversation from earlier, there are frequent violations in the southwest of Nigeria's metalworking industries. By taking the following actions, these abuses can be lessened:

3.14.1 Adoption of vegetable oil lubricants or cutting fluid emulsion

Scholars both domestically and overseas are attempting to switch to vegetable-based oils that are sustainable and ecofriendly. Vegetable oils are less costly, more natural, non-toxic, and non-polluting. Various plants oils, as compared to MOCFs, have various properties because of their distinct chemical content. According to recent research, bio-based cutting fluids perform better than traditional oil-based cutting fluids at extreme temperatures in terms of lubricity and viscosity reduction. In many machining processes, including grinding, turning, milling, and drilling, vegetable oils have been employed as cutting fluids. Singh et al. [27] conducted studies on the capacity of vegetable and mineral oils to reduce surface roughness during the turning of EN31 steel in dry and MQL conditions. In terms of surface finish, it was discovered that vegetable oil outperformed MOCF. When compared to MOCF, the reduction in surface roughness caused by vegetable oil was roughly 1–10%. The impact of mineral and vegetable oil-in-water emulsion cutting fluids on the cutting force and surface roughness when turning AISI 4340 steel with coated carbide tools was examined by Lawal et al. [28]. In attempt to develop an oil-in-water emulsion using cottonseed oils and palm kernel, the study entailed choosing cutting fluid additives. Likewise, Xavior and Adithan [29] investigated the effect of cutting fluids on surface roughness and tool wear during AISI 304 austenitic stainless-steel turning. They discovered that coconut oil can reduce surface roughness and tool wear during machining operations. Gunerkar and Kuppan [30] investigated two separate vegetable cutting oils derived from refined rapeseed and sunflower oils, as well as a commercial mineral processing fluid, to determine the minimal cutting forces, surface roughness and tool wear when turning SS316. Vegetable oils are mixed with water in a 1:100 oil-to-water ratio. When all yield factors were evaluated, it was determined that vegetable oils were more advantageous than MOCF. Ojolo et al. [31] investigated the impact of certain straight vegetable oils on cutting force when turning round bars comprised of three raw material (aluminum, copper, and mild steel) utilizing tungsten carbide tools. The oils researched included shea butter, palm kernel, coconut, and groundnut oils. The findings demonstrated that bio-oils were appropriate for use as metalworking fluids, however their influence on cutting force were material-specific. The impact of new vegetable oil compositions on part accuracy and surface integrity during tapping and reaming operations with AISI 316L stainless steel were examined by Belluco and De Chiffre [32]. It was discovered that cutting fluid significantly affected component precision, surface integrity, and the thickness of the strain-hardened layer in the sub-surface. Cutting fluids made from vegetable oils outperformed mineral oils in terms of capability. When turning AISI 4340 steel with ceramic tools, Çydaş [33] investigated the impact of dry machining on tool flank wear, surface roughness and temperature. During the processing of AISI 4340 steel using carbide cutting tools, Suresh et al. [34] investigated the impact of dry cutting on machine power, cutting force, tool wear, and surface roughness.

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Figure 9. Contaminated River and land site contaminated with spent cutting fluids

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Figure 10. Drainage map of Ibadan depicting the location of metal workshops

Table 15. Workshops within 40 meters, 80 meters, and 120 meters Buffer