Keep Your Eye on DME
Di-methyl-ether (DME) is a fuel that I have been talking about since at least 2006. I have blogged about it, and I have classified it in several of my presentations as a “Sustainable Contender” (including in a slide at last year’s ASPO conference). I want to use this post to explore DME in a little more detail, and explain why I think you should keep an eye on it as an attractive renewable replacement for diesel.
DME is a pretty simple compound. Methane, the least complex hydrocarbon, has the chemical formula CH4. That is one carbon atom bonded to four hydrogen atoms. When methane is burned – which is to say reacted with oxygen – it produces carbon dioxide (CO2) and water (H20).
DME can be thought of as a couple of methane molecules with an oxygen separating them. It looks like this: CH3 – O – CH3. This is an ether; in fact the simplest ether (characterized by the oxygen separating two hydrocarbon groups). Note that each methane (methyl) group is missing one hydrogen, which allows it to form the bond with oxygen. But when DME is burned, you still end up with carbon dioxide and water.
DME is produced from methanol, the simplest (and cheapest) alcohol. The current price for methanol as listed by Methanex is $1.10/gal, compared to a national average rack price of $2.26/gallon for ethanol and a national average spot price of $1.83/gallon for gasoline.
Methanol works fine as a transportation fuel, but has some disadvantages. While methanol is cheaper to produce than ethanol, the energy content per gallon is even lower than for ethanol (and methanol is more toxic). Ethanol has about 2/3rds of the energy content of gasoline, but methanol contains only half the energy content of gasoline. As a transportation fuel, this is a disadvantage (but not a knockout) because it limits the range of your car.
As a fuel, DME can be used in either a gasoline or a diesel engine. That makes the potential market huge. DME is a gas at room temperature, but compresses to a liquid under mild pressures. It is currently used as a propellant in many consumer products, and is classified as non-toxic and non-carcinogenic. (Granted that if you stand around in a room filled with nothing but DME, you will die due to oxygen deprivation. The same is also true of nitrogen, which makes up 79% of our atmosphere).
DME is completely miscible with LPG, and can be used as a supplement/replacement in either transportation or heating applications. When combusted, DME burns very cleanly. There are no associated sulfur or particulate emissions (even in a diesel engine).
DME can be produced from biomass, coal, natural gas, or essentially any source of carbon. Unlike many ‘next generation’ biofuels, production from biomass is a straightforward route and not especially complex. You gasify biomass to produce syngas, react syngas to produce methanol, and then dehydrate the methanol. Each of these steps takes place every day at large scale at chemical companies around the world.
There are some specific disadvantages from DME, but this is true for just about any fuel. First, the fact that it is a gas at room temperature means that if there is a leak, it can form an explosive mixture in the air. The same is true for natural gas or LPG. Second, the energy density of the fuel is lower than for gasoline or diesel. The volumetric energy density lies between that of ethanol and methanol.
So why aren’t we using it in North America? Like many other fuels, it is a chicken and egg problem. We don’t have the infrastructure in place in the U.S. Some vehicle modifications would be required to accommodate it as well. But these are not insurmountable problems, as the continuing roll-out of E85 vehicles and service stations has shown.
The Swedes are also at the forefront of rolling out DME. The Swedish company Chemrec has been converting pulp mills into biorefineries that produce DME. Volvo has announced that they are conducting studies on the performance of DME in 14 of their heavy trucks over the next two years. (Here is another story on that at Green Car Congress).
In North America, I know several people or groups who have expressed interest in, or are dabbling with DME. My expectation has been that at some point there will be an entry into the market here, but it will be slow due to the aforementioned lack of infrastructure. What prompted me to write this essay was I spotted a story yesterday about a Canadian company that is going to give it a shot:
A clean fuel that’s already gaining traction in Asia could be getting a toehold in Canada, just in time to help northwest B.C.’s hard-hit forest industry. Dimethyl ether, or DME, is almost unknown in North America but may soon get a big boost here from new tough emission standards coming to the U.S.
DME is a mixture of hydrogen and carbon monoxide that can be produced from biomass, natural gas or coal. It is now used as a propellant in aerosol spray cans because it is non-toxic and breaks down. But DME also has the potential to replace diesel fuel because it produces 95 per cent fewer greenhouse gases, no soot, low levels of nitrogen oxide and no sulphur dioxide.
Calgary-based GV Energy is proposing to build a biorefinery to produce DME in Terrace, B.C.
While some of those details are slightly inaccurate, the article is a good read on how DME can fit into the fuel mix and add jobs in an area with the right resource base. Especially interesting to me is to view the comments from readers. I find it amazing at times the emotional attachment some people have to trees. I can understand opposition to the conversion of forest to pasture or agricultural land. I can understand the opposition to clear-cutting and not replanting. But it seems that to some people, cutting down a tree is just wrong. Period. This coming from people who are living in houses made from wood.
If we use managed forestry to produce DME, then that has the potential to be an improvement over the status quo. Like anything else, there is a right way and a wrong way. But just because a wrong way exists doesn’t mean that you don’t try at all. We (my company) are not going stop trying to responsibly manage and use forest assets just because some aren’t doing so. We will just continue to do things in the most sustainable way we can, and hope that the proper incentives are in place to make sure others do so as well.
But I digress a bit. To learn more about DME, see this presentation put together by Europe’s BioDME project. Note especially the slide that shows the land usage efficiency of DME relative to competing fuels.
The market for DME is bound to continue growing due to its versatility as a fuel and because it can be produced relatively easily from a wide variety of starting materials. The question is whether North America will continue to watch that growth occur in Europe and China.
Update: I have received a note that another BC company is also working on DME: Blue Fuel Energy.
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