The debate is not whether natgas can "play all parts". That is a straw man argument anyway. The debate you generated was whether NGVs were a viable direction and you claim that it is not. I disagree.

Your argument about "energy security" and being able to forecast beyond 10-15 years out is nonsense. We have NEVER been able to forecast ANYTHING that far out with any degree of accuracy. You pointed out that EIA projections change every year. ... Well, of course they do. The futures markets change every day. New information continually comes to light that changes our view of the future.

You also need to define what you mean by "cleaner". SO2 and NOX emissions from natgas are pretty much negligible.

James Carson

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I think this author is mistaken on several points, and I am in broad agreement with Mr. James Carson (who'd a thunk it?).

Let's address a few of them:

NG is not clean:

This is wrong and misleading. While it is not perhaps the cleanest fuel in theory (H2 might be cleaner) it is mostly clearly the cleanest fuel in practical use today. The fuel burns a little cooler, which allows NG vehicles like the Honda GX to get great emissions ratings; the GX is one of the only cars to have the AT-PZEV, and it's not even a hybrid. NG vehicles generally have very low NOx ratings, even lower than cars that burn H2.

Every hydrocarbon fuel emits CO2, so you can't do much about that. Methane (CH4) has the most chemical bonds per carbon atom, so it is the cleanest hydrocarbon fuel available. Any other one is dirtier.

NG cars are an interim solution Again, I disagree. I think they could become part of a final solution for vehicles. NG (methane) can be the third fuel of vehicles powered also by electricity (low cost, expensive storage) and synthetic liquid fuels (like ethanol, high cost, low cost storage). Renewable methane (which can dovetail nicely with our extant NG infrastructure, as well as any more of it we decide to build) is moderate in cost and moderate in storage cost. In a nutshell, you car of the future uses low cost electricity for the first 10-20 miles, methane for the next 40-100 miles, and expensive ethanol or gasoline for the rare trips the require long range. That provides the range that consumers demand at lowest overall cost. Maybe a miracle battery will come along, but that's unlikely. Maybe a miracle fuel will come along, but that's even MORE unlikely. As oil dries up, methane will become more attractive as a vehicle fuel because it's not THAT bad and we have an infrastructure in place. One could argue for methanol as well, but its bulky (for a liquid fuel) dirty to burn, and poisonous.

Methane is difficult to store in vehicles Somewhat true. But still easier than hydrogen. And probably it will always be cheaper than batteries. Recent advances in charcoal-like materials have promise in greatly increasing the density of methane storage systems. This is definitely a tractable problem.

We will run out of NG Could be. But NG vehicles can run on renewable methane. Either created viable biomass sources, or synthetically via electrolyzed hydrogen, some CO2 (plenty of that around) and a Sabatier reactor. Unlike gasoline, or even batteries, methane is a fuel source that one could have explicit local control over. Methane generators are not hard to build. India has been building them for 100 years.

NG or methane is tied to the IC Engine Also not true. SOFCs (Solid Oxide Fuel Cells) run great on methane. For stationary and perhaps mobile applications. With efficiencies double that of IC engines.

NG or methane is the fuel that hydrogen was supposed to be. It has all the benefits of hydrogen in terms of synthesis from renewable sources (via the Sabatier reactor) and the additional benefits of having an extant infrastructure and a viable technology to use it (IC engines as well as turbines).

Jim Beyer

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Barring some miracle battery development, all-electric vehicles will NEVER be competitive with a hybrid fuel strategy that includes methane or liquid fuel; even synthetic (e.g. expensive) liquid fuel.

Why is this the case? This is because batteries are so expensive. So the marginal cost to double the range of an all-electric vehicle is to double the size (and cost) of the battery pack. This is despite the fact that the marginal value to the consumer (of the increased range) is fairly small. But the consumer WANTS the range because occasionally they drive 300 miles in a day.

But with a hybrid vehicle (burning ethanol or methane) the marginal cost of the increased range is tiny (just a bigger tank). When those rare long-distance trips are actually driven the cost may be high because of the fuel purchased; but the overall cost to the driver is lower and the value is higher.

Getting a cost-effective plug-in hybrid vehicle (PHEV) on the road won't be super easy, but definitely possible. It notable that the main issue effecting costs remains the batteries, and not the extra IC engine that needs to be carried around. I guess something that's been optimized for 100 years might still have some retained value after all.

Jim Beyer

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Electricity markets are my thing at RisQuant Energy. Natgas is central to my work as a fuel particularly as it is the fuel most often on the margin in the power markets, at least during on peak periods. My conclusion is that there is more than enough methane in the US and worldwide at current $/mmBtu to supply our needs for a very long time. As an important bonus, it helps reduce real pollution in addition to CO2.

James Carson

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Methane storage with corn cobs

Methane storage with MOFs

Renewable methane would be any methane created from renewable sources. This could include the creation of methane via the anaerobic digestion of biomass (such as occurs in landfills) or the production of synthetic methane via electrolyzed hydrogen (getting the hydrogen from processing NG would be silly....) and CO2. The reaction in a Sabatier reactor is:

CO2 + 4H2 -> CH4 + 2H2O + heat

Essentially, hydrogen is so reactive it "burns" in a CO2 environment, creating methane and water. Sabatier reactors are a mature technology; the space station even runs one 24/7 to keep the air scrubbed for the astronauts.

Synthetic methane is problematic cost-wise because electrolyzed hydrogen (hydrogen from water) is still quite expensive. But it addresses the storage and end-use problems that have plagued the full-on hydrogen economy. The bond energy loss in creating methane from hydrogen is about 20%. No free lunch. But for that cost, you get a fuel with an extant infrastructure and something 3X denser and much easier to store.

Jim Beyer

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I'm not sure the exact weighting of methane versus carbon dioxide for global warming, but it's not 20 times. The molecule itself is about 20 times more able to grab heat, but it decays to ordinary CO2 after about 90 years, so the overall weighting is more like 7 or 8.

With respect to batteries, I'd have to run my numbers again, but I'm pretty sure even at $300 per kw-hr storage and 3000 charge cycles, PHEVs make more sense than all-electric, and we aren't even close to those numbers yet.

James, as I said earlier, the CNG tank need not hold all 15 GGE of fuel; just a few would be fine to greatly lower the customers' overall fuel cost. A small tank for liquid fuel would allow for greater range and to interact with the extant liquid fueling infrastructure.

Maybe a tri-fuel system seems a bit clunky, but it would work, it would not be unduly expensive, and relies on no miracle technology innovations to occur, which frankly, and unlikely to happen anytime soon.

...

I can see a good deal of anxiety over methane comes from the precarious state of natural supply. That is somewhat beside the point when selecting a fuel that can be synthesized. As I recall, no one lamented the poor state of our hydrogen wells 5-10 years ago.

A single home in a temperate area typically uses far more gas annually than a single car would use. 100 cubic feet is about the same as a gallon of gas. It's not hard for a home to burn through 100 gallon gasoline equivalents in a single month. The pipeline infrastructure will NOT be overwhelmed, especially during the summer months. And yes, I'm sure there will be plenty of STEEL for the drill stems. (Sheesh....) I dunno about Barium. I guess that means fewer enemas...

"If storage problems preclude the widespread adoption of hydrogen..." They do and they will. Along with PEM fuel cells not becoming reliable enough or cheap enough.

Let's put this in crystal clear terms: methane is 3.2 times denser energetically than hydrogen. Hydrogen storage has perhaps been getting a bit better, but so has methane, so they continue to track fairly well. That means even if a fuel cell is 100% efficient (an impossibility) then a methane engine need only be 31.25% efficient (a possibility) to have a greater range for the same tank volume. Hydrogen is hopeless for vehicles.

Reasonable people can argue about the merits of methanol, DME, or Butanol. Or Ethanol, for that matter. My generic answer to all of these is that there is no free lunch with respect to liquid fuels. Liquid fuels are darn convenient; granted. But when it comes to making them from biomass or purely synthetic sources, you PAY for that convenience. Of course, you could make them from coal, but you pay a huge carbon price for that; and one could argue that such coal might be best simply burned for electricity.

And synthetic gasoline IS that much harder to produce, assuming synthetic sources. You are throwing away a lot of hydrogen bonds to get that convenience. That means $$$, unless you are making it out of scoops of coal.

The good and bad of methane is do you want to pay a lot for a tank once or do you want to pay a premium for your fuel every time you gas up? To me, this argues for a small methane tank and a tri-fuel strategy, The point to remember for vehicle fuel storage is that the first gallon equivalent stored is used all the time, so it should be an expensive container using a cheap fuel (e.g., electric battery). Conversely, the last gallon equivalent stored is used quite infrequently, so it should be a cheap container holding an expensive fuel (e.g. plastic tank of gasoline). Methane and it's tankage falls somewhere in between. (H2 falls somewhere between batteries and methane which really means it falls through the crack and makes little practical sense at all. But I've said that already.) Note that this also explains why all-electric vehicles make little sense unless one is comfortable with a very limited range.

In terms of hydrogen in SOFCs, one has to ask: where did the hydrogen come from, and why is it now being used to make electricity? If it was electrolyzed, why not just use THAT electricity in the first place? If it was from NG or coal, why not just burn that? And if it was from electricity generated some time ago (a temporal shift) then one will find that should this duration be longer than about 1-2 weeks, then one is better off making CH4 (via Sabatier reaction) and storing it that way, instead of dealing with H2 storage. Once again, hydrogen is the 'tweener' storage between electricity and methane. Hydrogen probably wouldn't make sense even if we DIDN'T have an NG infrastructure in place. Given that we do, it's hard to believe we still talk about it.

Jim Beyer

This is an excellent article with excellent comments:  followup at:

U.S. Energy Security and Natural Gas Vehicles: A Reality Check

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