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Topping-out ceremony for the Audi e-gas plant; synthetic methane production to begin in early 2013

Components of the e-gas plant. Click to enlarge.

Audi is celebrating progress on its e-gas plant under construction in Werlte, Germany with a topping-out ceremony. End products from the plant will be hydrogen and synthetic methane (Audi e-gas), to be used as fuel for vehicles such as the new Audi A3 Sportback TCNG. (Earlier post.)

The Audi e-gas plant, which can convert six megawatts of input power, will utilize renewable electricity for electrolysis, producing oxygen and hydrogen, the latter which could one day power fuel-cell vehicles. Because there is not yet a widespread hydrogen infrastructure, however, the hydrogen is reacted with CO2 in a methanation unit to generate renewable synthetic methane, or Audi e-gas. Chemically speaking, this e-gas is nearly identical to fossil-based natural gas. As such, it can be distributed to CNG stations via the natural gas network and will power vehicles starting in 2013.

This power-to-gas technology opens up new possibilities for sustainable mobility and tomorrow’s energy industry. The e-gas project marks a transition toward alternative forms of energy for automobiles.

—Reiner Mangold, Head of Sustainable Product Development at Audi AG

The CO2 used in Audi’s e-gas plant is a waste product from a nearby biogas plant, operated by energy provider EWE. The e-gas plant will annually produce about 1,000 metric tons (1,102 US tons) of e-gas and will chemically bind some 2,800 metric tons (3,086 US tons) of CO2. (This corresponds to the amount of CO₂ that 224,000 beech trees absorb in a year, according to Audi.)

The Werlte facility will generate enough CO2-neutral synthetic methane to power 1,500 new Audi A3 Sportback TCNG vehicles 15,000 km (9,320 miles) every year. This compact five-door car will arrive at dealerships in late 2013. Audi plans to launch a second TCNG model, based on the A4, in 2015.

A special certification procedure will verify that the same amount of e-gas that owners purchase for their Audi TCNG vehicles is fed into the network by the e-gas plant. A similar balanced-cycle method is used to verify procurement of green power.

The ability to store large quantities of wind or solar energy via the dual electricity/gas principle could significantly foster the expansion of renewable energies, Audi suggests. The Audi e-gas project can be easily replicated in any country with a natural-gas network.

The Audi e-gas plant in Werlte is being built on a site owned by energy provider EWE AG measuring 4,100 m2 (44,132 sq ft) overall. Ground was broken in September 2012. As owner, Audi is constructing the plant in cooperation with equipment manufacturer SolarFuel GmbH. They have prioritized the optimization of energy flows. Waste heat generated during electrolysis and methanation, for example, is used in the adjacent facility.

Once the electrolysis units have been installed, the methanation reactor will be supplied and connected. This specialized unit some 16 meters (52 ft) in height will be provided by MAN, a sister company in the VW Group. e-gas production will begin in early 2013 and feeding into the public natural-gas network in summer 2013.



I make that about 250 metric tons of hydrogen produced a year at 25% by weight of the 1000 tons of methane:
For 6MW, that is about 41,666kgs/MW
Per day, that comes to 114kg, or per hour 4.8kg
At 33kwh/kg that is 158.4kwh per MW

That is only around 15.85 efficient, so I don't understand that as electrolysis is way more efficient than that.

Are there big losses in combining the hydrogen with carbon to make methane?


I do not understand Audi decision makers and rational behind. What is driving them making such crap and scraping good things like Audi A1 Etron.


They are hedging their bets in case hydrogen Fuel cell EVs become widespread.

Bob Wallace

If they can produce at a decent price then there are other uses for their product. Deep backup for the grid is likely to be done with gas turbines. Demand for gas for cooking and heating will likely continue.

A price on carbon could swing costs in their favor.


Germany has been injecting small amounts of H2 into the natural gas pipeline system, but at roughly 1/3 the volumetric energy density it will eventually cause problems for equipment expecting a certain amount of energy in each scm.

The paper I found on storing renewable energy claims that renewable methane from this very process costs about 8¢/kWh(th), while fossil methane is about 2¢.  I doubt that German consumers would tolerate, nor German industry withstand, a quadrupling of the cost of fuel for electric generation.



Bob Wallace

The price of imported natural gas into Europe is currently 4¢.

Germans are willing to pay more to protect the environment, if necessary. Like I said, a price on carbon can change price relationships.

If they need a modest amount of methane for deep backup they might pay something more.

And the cost of this technology could well decrease, especially as more and more cheap electricity becomes available. Add into that the fact that gas imports come from Russia which brings another set of interesting variables.

Thomas Lankester

From a straight energy efficiency point of view this does seem bonkers but maybe this would work in Germany where solar and wind supply are increasingly likely to swamp the grid a times.Even at a 15% efficiency, rather than dumping excess power this might make economic sense if the fuel is sold at a premium for transport usage (rather then power generation of cooking).

Bob Wallace

I'm working my way through a paper that determines the least expensive way to operate a grid based on wind, solar and storage. (For simplicity they leave out other sources.)

They used real world data in one minute blocks for a four year period. Data from the largest commercial grid in the world. They matched minute to minute demand to wind and solar availability.

They found that they needed to use natural gas turbines five times in four years for brief periods each time of use. That is not a lot of gas. So if we wanted to get even this last amount of fossil fuel out of our system the higher cost of manufactured gas might not do much to change the cost of electricity.

(Of course if they added in geothermal, hydro and tidal the amount of gas would drop. And by letting a lot of EVs skip a couple of charging days gas demand should produce a further cut.)


This shows the versatility of methane as it can be blended from natural gas, scrubbed biogas and synthetic sources. Unlike gas-to-liquids via Fischer Tropsch most of the starting thermal energy is retained.

So far there doesn't seem to be a fugitive emissions problem as we see with fracked gas; think kitchen taps catching on fire in farms near shale gas drilling. In this case the methane could leak from the methanation plant or the garage pumps.

If e-gas becomes popular for vehicles the CO2 source may not keep up. More and more original natgas will be used for vehicles. I wonder if this will drive up the price of grid gas. A fourfold increase will be too steep for home use, factories, power stations and so on.


@ Davemart,
you need more than 2H2 for one CH4, because you don't only have to reduce the carbon, but also the oxygen.

CO2 + 4H2 --> CH4 + 2H2O
(you get the extra energy back when burning the CH4 not only to CO2 but also to 2H2O)
The price of the H2 depends on the price of the electricity. Because windenergy (and solar) is becomming cheaper and cheaper, they will build windmills(and solar) in order to produce enough renewable electricity even when there is low wind and sun. Consequently, there will be an overproduction when there is a lot wind and sun. This strategy is much cheaper than building huge batteries. At the moment of overproduction, they can do two things : shut down the windmills, or use the 'completely free' electricity for other things, such as H2 production. This H2 is a free waste-product !

In addition, macro-economically, there is a huge difference between paying 4c for a home-made unit of CH4 versus paying 4c for imported CH4.

The economical cost for the US for their oil consumption is not the fact that they burn billions of $ (that's only positive for the GDP) , the problem is that it is imported.

Even more, H2 can be used for much more than CH4. Also for fertiliser production and conventional oil refining, enormous amounts of H2 are used now. At this moment, they are produced from natural gas, but they will obviously have to produced renewably somehow.

The price of the H2 depends on the price of the electricity. Because windenergy (and solar) is becomming cheaper and cheaper, they will build windmills(and solar) in order to produce enough renewable electricity even when there is low wind and sun.
The objection to nuclear power is that its capital cost is excessive (the "danger" objection is nonsense).  If you have to overbuild wind to 5x average demand to deal with low capacity factor and high storage losses, aren't you better off sticking with nuclear?

It probably makes no sense to build storage systems able to absorb the full difference between production of 3x nominal demand and off-peak consumption of 0.6 of that, but even at 1.5x average demand and €1000/kW(e) (see page 131 of reference below) you're talking another €1500 per kW of average demand just to get the excess energy into storable form as methane.  Getting it out again costs more yet.

there is a huge difference between paying 4c for a home-made unit of CH4 versus paying 4c for imported CH4.
The figure claimed is 8¢/kWh(th), not 4¢, and the fuel and O&M costs of nuclear are about 1.7¢/kWh.

There really needs to be a comparison of "RPM" (renewable power methane) as proposed in the paper and H2 and/or methane made from off-peak nuclear electricity.  I suspect that the economics of nuclear are much better because all the equipment gets used more and the capital costs are amoritized over several times as much production, plus you need much less of it because nuclear doesn't need to be overbuilt to nearly the same degree and there would never be the same level of excess requiring storage.

Kit P

The first line of the abstract for the link provided by E-P is BS.

“The two major challenges in global energy systems are to reduce energy-related greenhouse gas emissions and to maintain energy supply security.”

Actually it is not much of a challenge at all. We do it everyday. Of course if you reject nuclear power I have to conclude that you are not the least bit serious about AGW.

The last line is also wrong.

“Finally, the role of such a transformation in global climate protection is analyzed. It has to take place until 2050 in order to limit global warming to 2°C.
Therefore, there is not much time left for the transformation to start.”

France transformed their grid 30 years ago. There are lots of interesting paper written by grad students but they have not practical value.

“I'm working my way through a paper ...”

BS Bob does not stop to ask himself if his source of information is BS.

“aren't you better off sticking with nuclear? ”

That is correct. In France the nuke plants load follow except during very demands. This results in a lower capacity factor of 10%. Essentially France is storing uranium inside the reactor at a small cost penalty.


Okay, back-of-the-envelope calculation.  Assume:

  • Nuclear electricity available off-peak at 1.3¢/kWh over the F,O&M cost, or 3¢/kWh.
  • Assume electricity-to-methane plants cost $1000/kW(e) and operating at 62% efficiency.
  • E2M plants must be rated at 30% of nameplate nuclear plant output and operate at 30% capacity factor.
  • O&M is 2% of investment per year.
  • CO2 is free (from landfill gas, etc.)
Amortizing over 20 years at 5% ROI requires an annual payment of 8% of the investment; adding O&M, and we're up to 10%.

Per 1 kW of nuclear plant:

  • 0.3 kW of E2M plant is required costing $300 requiring $24/kW/yr for amortization.
  • O&M costs 2%/yr of investment or $6/kW, for a total of $30/kW.
  • Running at 30% capacity factor, it absorbs an average of 90 watts and produces an average 56 W(th) of methane.
  • Multiplied by 8766 hr/yr this is a total of 49 kWh(th)/yr of methane.
  • Amortization plus O&M costs almost 60¢/kWh(th).
  • Adding the input energy cost at 3¢/kWh input or about 5¢/kWh of product, you're up to 65¢/kWh(th) of methane.
You are NOT going anywhere with electric-to-methane.  Not even if the electricity is free.


Rather, you're not going anywhere with a unit costing $1000/kW(e) of input.  Get down to $100/kW(e) and minimal maintenance and you're talking.


Another issue to consider is the sunk cost in methane based infrastructure when fossil gas is gone or prohibitive. By fossil gas I mean natgas, shale gas and coal seam gas. My guess is that despite the hype over fracking that fossil gas will be very expensive world wide, perhaps as soon as 2030.

The end of gas scenario kills a lot of essential activities such as convective heating for thermal comfort and process heat, chemical input for Haber Bosch fertilisers that feed the world, fuel for peak power and backup for intermittent wind and solar. If the gas grid is abandoned it is a huge write off. We will still need hydrocarbons for most long haul transport.

I also suggest that by year 2030 we are so freaked out by climate that we cannot use coal for these purposes. Synthetic methane will store better than hydrogen and can fuel engines (albeit inefficient) that can be repaired by backyard mechanics unlike fuel cells. These kinds of issues need to be factored into the case for synthetic methane.


Aussie, I think electrified highways may be a shorter and more-efficient route to displacement of carbon-based fuels than synthetic methane.


I agree completely on nuclear. But whether your elektricity source is wind, sun or nuclear, in all cases it is smart to produce maximal amount of electricity at any moment (so not shutting down when production is higher than direct demand), but use the excess electricity to produce H2.
Of course, full-electric is more efficient than an ICU on renewable methane, but that's not the point here (I think).
As long as there are ICU's, it is useful to burn synthetic fuels instead of fossil fuels.
At the glorious moment when we don't need ICU's anymore, we will still need a lot of chemicals for other uses, which could all be made from excess electricity.

At this moment I would like it to be maximally nuclear. But whatever windmills or solar cells are available, it would be a shame to shut them down because of excess electricity. I wouldn't be surprised if the windmills that are being built now in Germany (that are now said to be intended to replace the nukes) will eventually be used to replace the coal plants. At this moment, sadly there is more democratic rejection of nuclear than of coal. So the only democratic support they have is for more wind and solar. However, within a few years, when the nukes could be shut down because of availability of enough wind, I expect the fossil plants will be shut down instead of the nuclear.

This is not a discussion between nuclear or renewable, but between wasting excess electricity or building a massive synthetic chemicals infrastructure.

Bob Wallace

" in all cases it is smart to produce maximal amount of electricity at any moment (so not shutting down when production is higher than direct demand)"

That seems to make sense, but it does not always hold.

If your choices are, for example, inexpensive wind generation and something more expensive it can make sense to overbuild wind and curtail at times as opposed to choosing a more expensive generation technology.

Installing additional capacity can be cheaper than storage and peaking plants.

If we could find a use for that curtailed production, that would be great. But if over-production occurs too infrequently it won't justify the cost of a "whatever factory" which sits idle much of the time.

it is smart to produce maximal amount of electricity at any moment (so not shutting down when production is higher than direct demand), but use the excess electricity to produce H2.
I am skeptical about hydrogen (Ergosphere post in the pipeline).

What's really needed is something with low capital cost and preferably an energy multiplier; something like a microbial cell that uses the carbon in sewage sludge to turn 1 kWh of electricity into 3 kWh of methane, costing $20/kW(e) and tolerating long periods with minimal input (or running oxidatively).  Hydrogen-based systems at $1000/kW(e) don't look viable; unless I have my numbers completely wrong, they are economically ruinous.  Perhaps direct ammonia synthesis cells are feasible; Hargraves lists a claim of 6800 kWh/ton for direct synthesis of ammonia.  At 17 MJ/kg of product, the efficiency would be 24.5 MJ in for 17 MJ out; about 69%.  What matters is the capital cost, operating duty cycle and O&M.

As long as there are ICU's, it is useful to burn synthetic fuels instead of fossil fuels.
It depends what they cost.  If they are ridiculously expensive compared to fossil fuels, nobody will buy them.
whatever windmills or solar cells are available, it would be a shame to shut them down because of excess electricity.
That peak-to-average ratio is an issue, because it determines the amount of excess generation that the storage systems must be sized to absorb.  The capital and operating cost of those systems are not something I'd bet on to run industrial civilization.

Bob Wallace

The largest wholesale commercial grid in the world is the PJM Interconnection. It covers all or part of 13 states from New Jersey to Illinois and from Pennsylvania dipping down into Tennessee and North Carolina. It serves 60 million customers.

If it could be shown that that big grid could get 99.9% of its power from wind, solar and storage at a comparable price to today's (all-in) cost of electricity, would that do?


NBF's commentary on that:

Found the full article and the cost analysis. Yes, this study is crap.

Kit P

“Yes, this study is crap.”


It is a sad commentary that the staff and students at a community college in Delaware do not understand that we do not have very good wind or solar resources. I understand why BS Bob thinks the whole world is like California.

Here is a link to the PJM:

At the moment there are some utilities that are paying for others to take power from the steam plants. It is going to get cold tomorrow and those coal plants will be needed.

Except for pumped hydroelectric (which happens to be the closest power plant to where I live), making more power than we need and storing the energy is a stupid idea.

There is no reason why some of out power can not come from renewable energy so we can see what the impact is and how it works. .

Bob Wallace


Please describe, exactly, the problems with Budischak, et al. That single fact free page you linked is worthless.

Your link states:

Tbhis (sic) is basing (sic) analysis upon the crappy plans by Stanford's Professor Jacobson.

No. The Budischak paper does not use Jacobson and Delucchi's data or analysis. It simply states that Jacobson and Delucchi determined that there was more than adequate renewable energy resources around the world to meet all our energy needs. Their assessments have been verified by subsequent research.

Then your link states:

General limitations are I doubt they consider any economic growth that would require more power (it assumes you stay at the current energy requirements). I would also like to see how they are handling the power grid costs and if the grid is in the right places. Usually renewables need more power grid extensions which are costly and time consuming.

Yes, growth will require more power. The Budischak paper talks about this, but this issue is not germane to the issue. The paper also talks about grid issues but that is outside the scope of the paper which is about generation, not distribution.

The only valid point on your linked page is that the cost of providing fossil fuel free electricity might be less expensive using nuclear energy. Might be.

That is a different argument. One that can be had. But this issue is that you claimed -

The capital and operating cost of those systems are not something I'd bet on to run industrial civilization.

Budischak, et al. has demonstrated that our largest grid could be run with 99.9% renewable energy, meeting minute to minute actual demand over a four year period. And that it could be done for approximately the cost of what we now pay for electricity.

Here's the link. I'm looking forward to your learned evaluation...

Bob Wallace

Kit, I'll offer you maps of US wind and solar resources so that you might acquaint yourself with the resources available....

Wind, and do look at all that excellent red color just off PJM's coast...

And then solar. Zone 5, in which much of PJM is located gets an average of 4.2 solar hours per day.

If you wish to argue that actual load demands could not be met largely by wind, solar and storage you are free to read the Budischak paper and discover any mistake they may have made.

When you read do keep in mind that the researchers treated the PJM as a standalone grid. Connecting to surrounding grids would almost certainly have further decreased the use of fossil fuels below 0.1% and lower overall electricity prices by allowing less overbuilding and more sharing of storage.

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