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Emerging Trends and Benefits of Biolubricants
Dr Rahul Gokhale, A S Karmarkar Biolubricants offer various advantages over mineral/ petroleum-based lubricants. Escalating costs of vegetable oils and its derivatives are making commercial scale production of biodiesel non-economical. Making lubricating base oil from biodiesel can become an attractive option to utilise biodiesel manufacturing setup and to produce value-added products.

Lubricant is a substance - either fluid, semi fluid or solid - introduced between two moving surfaces to reduce friction. The primary purpose of any lubricant is to reduce wear and heat between the contacting surfaces in relative motion. While wear and heat cannot be eliminated completely, they can be reduced to negligible or acceptable levels by reducing the coefficient of friction between the contacting surfaces.

Current lubricants mainly fall into two categories: petroleum derived or synthetic. Although, the vegetable oils and animal fats were the first lubricants used by humans.Since the 19th century, they were replaced gradually by the hydrocarbonbased lubricants derived from petroleum mainly due to its ample availability and low cost. The petroleum derived products did not always meet the stringent technical requirements. Moreover, the lubricity of the petroleum-based lubricants is achieved by additives mainly based on sulphur or chlorine. The special technical requirements depending on the applications, triggered the development of the synthetic lubricants. For instance, the extreme high or low temperature operations or fire resistance or non toxicity for food grade application requirements could not be met by the conventional petroleum-derived lubricants. The synthetic lubricants played a vital role in these areas. However the synthetic based lubricants also suffer a drawback of not being necessarily biodegradable.

There are increasing concerns and growing regulations over contamination and environmental pollution, while in use or disposal after use. One of the major concerns is pollution caused by mineral oils. As the world oil reserves are dwindling, the efforts for finding alternative replacements are increasing. Vegetable oils are a biodegradable and renewable source of lubricants. Thus, they seem to be attractive candidates for the replacement of mineral oils. The use of animal fat or vegetable oils for lubricating the wheels of carts and carriages has been known.

Development of Biolubricants
Biolubricants thus propose a reliable alternative to address the increasing concerns in respect for the environment and for the sustainable development, and still giving better performance over conventional lubricants.

Over the past two decades, a renewed interest in vegetable oil-based lubricants has occurred as environmental interest has increased. The development of biobased lubricants is now on. In the developed world, the use of biobased lubricants is made either mandatory or preferential depending on the area of application. In Europe during the 1980s, various mandates and regulations were placed on petroleum products necessitating the use of biodegradable lubricants. In several German Lšnder, in Austria and Switzerland regulations are in place which forbid the use of mineral oil based lubricants around inland waterways and in forest areas. Similarly, in USA, USDA Bio-preferred programme is implemented to promote the increased purchase and use of biobased products. The programme is expected to promote economic development, creating new jobs and providing new markets for farm commodities.

The increased use of biobased products will also be expected to reduce petroleum consumption, increase the use of renewable resources, better manage the carbon cycle, and may contribute to reducing adverse environmental and health impacts.

Specialties of Biolubricants
The term biolubricants applies to all lubricants which are both rapidly biodegradable and nontoxic for humans and aquatic environments. The criteria for a biolubricant are that it should be vegetable oil based or animal product based, the end product should be non toxic and should be biodegradable. The biolubricants offer the advantage of biodegradability without compromising any performance characteristics. On the contrary, the benefits offered by biolubricants give them an edge over the conventional lubricants. The major salient features of the biobased

lubricants are as follows:

1. Excellent Lubricity and Improved Coefficient of Friction: The lubricity of the biobased lubricants is about 2 to 4 times their petroleum based corresponding lubr icants. This is enhanced with of the polar nature of the lubricants and also enhances the affinity towards the metal surface resulting in substantially increased thin film strength. This wetting tendency helps in reduction in friction and hence often higher tool life. This reflects in the reduced mechanical losses and thus considerable energy saving of the equipment operation.

2. Higher Viscosity Index: The viscosity of biolubricants does not vary with temperature as much as the petroleum-based lubricants. This is an advantage for designing of lubricants for use over a wide range of temperature. This can also result in lower viscosity classes for same applications with easier heat transfer.

3. Lower Volatility and High Flash/Fire
Points: Biolubricants have a very good record in applications like grinding, where there is a known fire hazard. This also helps in oil mist reduction and hence the inhalation of the oil mist or vapours. The use is also safe due to higher flash points.

4. Better Skin Compatibility and Less Dermatological Problems

5. Biodegradability and Non-Water
Polluting: These characteristics reduce the costs of disposal in addition to making them eco-friendly. Vegetable oils are in general considered biodegradable and meet the biodegradability standards of the American Standard for Testing and Materials (ASTM) and the Organization for Economic Cooperation and Development (OECD). Biodegradability of lubricant products refers to the bacterial breakdown of the oil and its additives over a period of time as measured in standard test methods. In the environment and exposed to the elements, all materials eventually break down and degrade into benign byproducts. Tests of biodegradability are used to determine the speed and degree of degradation under standard conditions. The European countries established the Ecolabel through the European Commission in 2005 using a standard logo for identification.

6. Minimise Cost: Cost saving on account of less maintenance, due to possible longer intervals between relubrication.

Application Areas of Biolubricants
Biolubricants can be applied in any application areas, the more prominent being the hydraulic oils, chain saw oils, spindle oils, metal working fluids, industrial gear oils, wire rope lubricants and greases. The improved lubricity provides better tool life and surface finish. Especially in case of coolants used in machining, increased feeds are often possible, as biobased coolants reduce friction and heat. Excellent sump stability and reduced toxicity make biobased coolants easy to maintain. One significant application area is the wheel bearing and the chassis grease for the automotives. Case studies have displayed the benefits of biobased greases including the gear boxes greases, wire rope lubricants and greases for bearings. The prime advantage of the superior lubricity of bio based lubricants is the reduction in the energy consumption by about 7 to 15 per cent. Reduction in wear and friction results in obvious increased life of the equipment.

Costing and Economics of Biolubricants
The costs of the biolubricants are marginally expensive than mineral oil-based lubricants, but are comparable or less than synthetic lubricants. The salient advantages such as energy saving, high viscosity index, biodegradability and non-toxic nature can provide excellent justification for the cost of biolubricants. In food and Pharma grade as well as wherever the operations are coming in contact with water, earth (mining and farming) or forest, it is becoming mandatory to use biodegradable, non-toxic lubricants, in view of overall acceptance to be eco-friendly.

Manufacturing of Biolubricants
Veg oil or biodiesel produced from veg oil forms base oil for biolubricants. The biodiesel is further transesterified using suitable chemicals and in presence of catalyst to produce biolubricants. The reaction is under high vacuum and at moderate temperature. The reactor is developed to carry out reaction without use of agitator. Hence this is absolutely maintenance free. Methanol is a byproduct. The process developed for methanol recovery will provide high purity methanol. After the reaction, the mass is washed with hot water and then dried and filtered. The lubricant oil is fed to high shear mixture and is blended with special additives to get the desired biolubricant. The existing biodiesel manufacturer can add this plant set-up to get value added product as a forward integration.

High demand for bio-based lubricants is expected in lubricants sector over next few years. Due to their advantages of excellent lubricity, non toxicity and biodegradability, they are bound to be used in all fields of industry. The right choice of lubricant will, however, always depend on the operating conditions and hence, the formulation of the lubricant will be a key to providing the best of the biolubricants.