Sustainability and Closing the Loop - The Basis for Design of Lubricants
Lubricants have been extensively used since time immemorial and since the beginning of the industrial revolution. The basic aim of these lubricants has been to reduce friction and wear. Metalworking fluids (MWF) also, thus, fall in this category. All these lubricants and MWFs need to meet certain crucial primary functions and expectations, which include reduction of friction, prevention of corrosion, flushing away the tribo-generated particles, and removal of heat. And among the secondary functions, they should have good anti-foaming, residue formation characteristics and good environmental acceptability.
Environmental acceptability is becoming increasingly important and, without a doubt, rightly so. The question that needs to be asked is, what are the criteria by which a lubricant of MWF becomes environmentally acceptable? Is it just that the product should not be harmful to life? What is it that makes any product, in general, and a lubricant or MWF, in particular, sustainable?
To understand this, the "closing the loop" concept is useful. In the concept of "closing the loop" one needs to clearly trace the path of the product and the components that go into making the product, right from "cradle to grave" and ensure that it does not harm the environment even after going to its grave. The steps in a general product life cycle are extraction, manufacture, use, and disposal of the materials that go into making the product. Such a cycle is called an "open loop" or the "cradle to grave" loop. Many-at-times we use the "closed cycle" or the "cradle to cradle" concept, where after use the materials that go into making the product are recycled and used again. When is it that we should go for recycling?
Materials are of two kinds; materials that can be replenished by nature and materials that cannot be replenished by nature. A simple look at the materials that go into making of lubricants and MWFs clearly shows that many of these products use materials that cannot be replenished. Here it is important to note that what constitutes "materials that can be replenished" is with regard to time scale. Even the base stock made from mineral oil is something that is replenished. The only problem being that we are using these at a much faster rate than what nature can replenish. And materials that cannot be replenished should be completely recycled. The analysis of the concept of "open loop" and "closed loop" should also include the energy and source of energy that goes into making, using, and disposing the product. It is important that the source of energy and not just the materials that go into making the product should also be sustainable. Even if we dispose off the product safely, after its useful life, the energy consumed should also be from a "renewable" source.
Unfortunately this is not the case with most lubricants and MWFs, and, possibly for almost all the products today. Here one should add that what is "safe" in developed countries is not safe in developing countries due to the lax environmental laws, and the final step of proper disposal in making a lubricant or MWF safe before disposal is never carried out. And many of the lubricants, especially greases, are used in total loss applications. The only way out is to develop products that follow the "open loop" using raw materials that can be replenished and using renewable energy sources. Such a cycle achieved with an "open loop", where the rate of consumption is equal to the rate of replenishment and the energy used is also from sustainable sources, can be called the "sustainable open loop". Needless to say, mineral oil based lubricants and MWF, at the present rate of consumption and nature of additives, do not fall in the "sustainable open loop" category. The only way out is to use natural oils (vegetable oils) and additives, produced using techniques that are sustainable. There is no point in producing these vegetable oils using chemical fertilizers and pesticides, both of which are unsustainable. Ideally, the additives that go into making these lubricants and MWFs should also be from natural sources.
Towards this end, we need to start with a philosophy that is different from what is done today; making an unsustainable non-eco friendly product more sustainable and eco friendly, to making a product that is sustainable and eco-friendly to begin with. The challenge, possibly the ultimate challenge, would be to make a lubricant that one can use as a moisturizer, a cutting oil emulsion that one can drink, a grease that one can use as peanut butter, and a hydraulic oil that one can cook with.
This article was authored by Satish V. Kailas.
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