19 Mar 2020 19:52 IST

Tapping into the DME promise of a clean drive

Researchers are studying how di-methyl ether can be used as an efficient and renewable vehicle fuel

The research has begun. If it ends the way they intend it to, you will be seeing and hearing a lot of it.

It is called DME – short for di-methyl ether. It is a gas. It’s been knocking around on the fringes of fueldom for a very long time. But now it seems that its knock has been heard, and doors are being opened for it.

Those who read Business Line today may have chanced upon my story that speaks of TAFE, the company that makes tractors, tying up with IIT Kanpur to develop an engine that runs on DME, rather than on diesel. IIT Kanpur has begun the research, TAFE is behind the researchers, lending support as the ‘industrial partner’. The idea is to study DME as a fuel that can run tractors, develop a kit to retrofit existing tractors so that they can convert to DME and train a fleet DME engine mechanics.

There have been many DME-run vehicles elsewhere in the world for long. But the TAFE-IIT Kanpur research is, by far, the first one to look seriously at DME as a vehicle fuel in India. In a year we will know how far they succeed, though there is no doubt today that they will. Of course, getting it to the market is another matter — which we will worry about another time. Cutting-edge technologies will have to cross the ‘valley of death’, where the well-entrenched incumbents try to drive out the new technology. But that, as we just said, is a concern for later. Right now, the point is that the latest research has put DME in the discussion spotlight.

An edge in storage, transportation

In many parts of the world, they make DME from natural gas. However, natural gas itself is a good fuel, so what’s the big deal? True, but where DME scores over its parent is in its ability to be bottled and moved around. Unlike natural gas, DME can be liquefied and stored in containers under little pressure in ambient conditions. What this means is, if suppose you find a large deposit of NG near the Andaman islands (and, indeed, there is), you would have to chill it to liquid and bring it home under extremely cold conditions, using cryogenic containers, and then re-gasify it. The cheaper option is to covert it to DME and ship it to the mainland.

However, that is not even the main advantage — if it were, it wouldn’t have motivated IIT-Kanpur to take up this project. The bigger advantage, from India’s point of view, is that DME can also be produced from agricultural wastes. Fantastic. Millions of tonnes of agricultural residues are generated every day. If you put them in, say, a buried tank along with some water, you’d get methane gas (which is essentially what natural gas is). This is, as we know, biogas. It is not being done today because the process of producing biogas from agri wastes is quite expensive, and usually, there isn’t much of a market near the villages where it could be sold. If you want to move biogas to the consumption points — cities — you only add to the costs. Not good.

Enter DME. Produce biogas, make DME from it and you are in business. Or, that is the hope.

No emissions

Now, there is plenty of scientific material on DME, extolling its valuable properties. They say, for instance, that it has a “high cetane value”, which means it ignites when you compress it. This makes it an excellent candidate to replace diesel with. Diesel is the same — you compress it, it catches fire on its own — which is why there is no spark plug in diesel engines. Another attractive aspect of DME’s composition is that it burns completely, leaving no particulate emissions. So you won’t need the costly diesel particulate filters. So, why not replace diesel with its twin, DME? That is what Dr Avinash Kumar Agarwal and Prof Tarun Gupta, of IIT Kanpur, are trying to do.

The scientific world will be looking at the work of the two researchers keenly. Many institutions and companies are working on mainstreaming DME. For instance, there is a company in California called Oberon Fuels which has vowed to commercialise DME. Look up their website. It says, “we are working toward the day when every city has DME production facilities, providing fleets with clean, high-performing fuel. And the US Environmental Protection Agency has approved DME as a ‘renewable fuel’. Furthermore, the International Organisation for Standardisation (ISO) has issued standards for DME — as the gas is in use today in other, non-fuel applications, such as manufacture of aerosols.

It must be mentioned that DME too has a darker side. Its ‘energy density’ is half that of diesel, which means that you’d need twice the amount of DME as diesel for the same work. But then, what is one bad quality in a sea of good qualities? I’m reminded of the words of poet Kalidasa:

Ekopi dosho guna sannipaathey (one negative in a bunch of positives) nimajjati (disappears) indoho kiraneshvivankaha (like the scar on the face of the moon).


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