Prius the top new vehicle badge in California in 2012; state accounted for 26.2% of Prius sales in US
EU “POWERFUL” project developing new low-emission combustion engines

Audi to introduce natural gas A3 Sportback g-tron at year’s end; CO2-neutral e-gas

Audi A3 Sportback g-tron. Click to enlarge.

Audi will introduce the compact A3 Sportback g-tron—which can be powered by the CO2-neutral Audi e-gas, synthetic methane generated from eco-electricity in the Audi e-gas project (earlier post)—at the end of the year. The e-gas fuel will be produced in the power-to-gas plant in Werlte, Germany.

The five-door car consumes on average less than 3.5 kilograms per 100 km of compressed natural gas (CNG) or Audi e-gas. CO2 tailpipe emissions are less than 95 grams per km (153 g/mile) in gas mode. When the A3 Sportback g-tron is powered by Audi e-gas, no more CO2 is released than was chemically input in its production beforehand, creating a closed loop. When the energy required to build the e-gas facility and wind power generators is included in a comprehensive analysis, CO2 emissions under e-Gas operation are still less than 30 grams per km (48.28 g/mile).

The engine is based on the new 1.4 TFSI. Key modifications relate to the cylinder head, turbocharging, injection system, and the catalytic converter. Developing 81 kW (110 hp) and 200 N·m (148 lb-ft) of torque, the Audi A3 Sportback g-tron has a top speed of 190 km/h (118 mph), with 0 to 100 km/h (0 - 62 mph) taking 11 seconds.

The Audi A3 Sportback g-tron is fully bivalent—i.e. its performance figures are identical in CNG and gasoline modes. CNG provides a range—based on standard fuel consumption—of around 400 km (249 miles), with gasoline providing another 900 km (559 miles) if necessary; the total range of 1,300 km (808 miles) is approximately on a par with an Audi TDI.

The car’s two tanks under the luggage compartment floor can each hold seven kilograms (15.43 lb) of CNG at a maximum 200 bar pressure. In tune with the ultra-lightweight construction concept, each tank weighs 27 kilograms (59.52 lb) less than its conventional counterpart.

The tanks are built with a new type of matrix. The inner layer consists of gas-impermeable polyamide polymer, while a second layer of carbon fiber-reinforced polymer (CFRP) gives the tank its extremely high strength; a third layer of glass fiber reinforced polymer (GFRP) provides rugged protection against damage from the outside. High-strength epoxy resin is used to bind the fiber reinforced materials.

A second feature of the Audi A3 Sportback g-tron is its electronic gas pressure regulator. This compact and lightweight component reduces the high pressure of the gas flowing from the cylinders down to around five to nine bar in two stages.

The regulator ensures that the right pressure is always present in the gas rail and at the injector valves—low pressure for efficient driving in the lower speed range, and higher when the driver calls for more power and torque. If the pressure in the tank drops below 10 bar, the engine management system automatically switches over to gasoline operation.

Two displays in the instrument cluster provide the driver with up-to-date information on the fuel level in each of the tanks. The driver information system also displays the current fuel consumption based on the particular operating mode.

The two filler necks are placed under a common fuel flap. After refueling, and whenever it is very cold, the engine is started with gasoline initially, then it is switched over to natural gas as quickly as possible.

Buyers of the Audi A3 Sportback g-tron will presumably obtain the e-gas at the public CNG refueling stations via an ecological accounting method, similar to the method currently in existence for obtaining eco-electricity.

e-gas. With the e-gas project, Audi is the first automobile manufacturer to develop an entire chain of sustainable energy carriers. The start of the chain has electricity produced from renewable energy sources; the end products are hydrogen and the synthetic Audi e-gas. Construction of the world’s first industrial plant to produce synthetic methane (e-gas) from CO2 and renewable electricity is almost complete in Werlte (Emsland district of Lower Saxony), Germany.

The Audi e-gas plant uses the renewable electricity in the first stage for electrolysis—splitting water into oxygen and hydrogen (Audi e-hydrogen), which could one day power fuel-cell vehicles. Because there is not yet a widespread hydrogen infrastructure, however, the hydrogen is then reacted with CO2 in a methanation plant to produce renewable synthetic methane, or Audi e-gas.

This e-gas is chemically identical to fossil-based natural gas. As such, it can be distributed to CNG stations via the natural-gas network. The power-to-gas process links the electricity grid and gas network bi-directionally for the first time. Until now, while one could generate electricity from gas, the reverse was not possible. The Audi e-gas plant therefore paves the way for tapping into the natural-gas network with its huge capacity as a storage and transport system for hitherto excess electricity capacity.

The CO2 used in Audi’s e-gas plant is a waste product from a nearby biogas plant, operated by power utility EWE. The CO2 is chemically bonded into the fuel at the Audi e-gas plant. The e-gas plant will annually produce about 1,000 metric tons of e-gas and will chemically bind some 2,800 metric tons of CO2.

The CO2-neutral e-gas from Werlte will power 1,500 new Audi A3 Sportback g-tron vehicles 15,000 kilometers (9,321 miles) every year. The power industry can also benefit from Audi’s e-gas project, as it addresses the nagging challenge of how to store large quantities of renewable electricity produced from wind turbines and photovoltaic systems efficiently and irrespective of location. The electricity-gas cogeneration technology could significantly foster the expansion of renewable energies.



Whether e-gas or Tesla Superchargers, it is good to see car makers providing energy for their cars. You can spend more on energy for the car than the car costs over the life of the car.


I'm not so sure I'm accepting the whole "CO2-neutral e-gas" argument. In fact I have strong doubts.

The e-gas still involves using CO2-tainted electricity to create hydrogen. That electricity would be more efficiently used directly rather than going through 3 additional conversion steps to move the CO2 emission from a smokestack that supplies electricity to the "power-to-gas" plant, to the tailpipe of an Audi car. These steps are NOT without energy losses, and you end up creating more CO2/mile than if you just used fossile fuel as a direct input to an efficient hybrid, preferably a 70+ mpg diesel hybrid. The electricity should be used directly for other purposes that are most effectively powered by electricity (residential electrical lighting is one such use).

The fact that the proponents invoke that some or all of the electricity has to come from wind power to make the argument is a telltale sign that they are cheating: Basically, they are stealing (diverting) clean wind power for use in cars instead of using it to displace CO2-tainted and dirty coal power in the electrical grid mix. That tells you right there that they are just playing CO2 shell games.

You have to look at the total picure. The truth is indisputably that the total CO2 emissions would become less if we feed the same wind power in to the grid for non-car use, and at the same time used fossile fuel directly in a diesel hybrid car that gets 70+ mpg. Their so-called closed loop is LOSSY and inefficient, and the net effect is more CO2/mile than the best existing hybrid car technology.

The "CO2-neutral e-gas" is a ruse to look good, while in truth making the overall CO2 emissions worse than what they have to be.

It is very counterproductive that people are proposing such convoluted schemes as "CO2-neutral e-gas" to look good, but there is a silver lining: It means that the policy makers and the general public are starting to understand that feeding CO2-tainted electrical grid-mix into "electric" cars is CO2-detrimental overall. The proponents are trying desperately to hide this fact, but the general public is slowly catching on to the hide-the-CO2 shell games. The proposal of such elaborate schemes is evidence that the hide-the-CO2 schemers are being backed into a corner.

In case anyone is wondering why I care about all of this:

I have two overall goals: Reduce fossile fuel use and related CO2 emissions by as much as possible, to slow global warming, AND to delay the inevitable extinction of fossile fuel sources for as long as possible. Leave the fossile fuel in the ground for future generations.


It does seem odd to make SNG when we have a lot of natural gas in the U.S. The one positive point is that they are using the CO2 twice, otherwise you would have CO2 from the power plant and CO2 from the car.



"using the CO2 twice" is an accounting fraud (or a CO2 shell game, as I like to call it). The proponents of e-gas ignore the excess CO2 created by the grid-mix electricity that is spent to create H2 and then bind with the CO2 to make the e-gas.

The net CO2/mile is *larger* than if they had fed the electricity directly into the car as an EV with a battery. Moreover, the electric car in turn has worse CO2/mile than the most efficient hybrid.



I should say that it is correct that burning natgas directly would be more CO2-efficient than the e-gas scheme, and that would be true even if 100% of electricity was made by natgas turbines.

H2 and e-gas are just energy-losing extra steps betwen electricity and the car.

The core of the scam is to pretend that the electricity going into the e-gas process is CO2-free. It is not. Every time electricity is diverted into driving a car, someone somewhere has to increase coal and/or natgas based electricity production, because there is no surplus of CO2-free electricity such as hydro, wind or nuclear.


But there's yet another caveat: Before diverting any natgas to car use,
it would be CO2-advantageous to displace all coal-based electricity with natgas -based electricity FIRST.


It is not phony accounting at all. If I burn gasoline in the car and coal in the power plant, I produce more CO2.

If I burn coal in the power plant and capture the CO2 to make fuels using wind powered electricity, I use the carbon twice and emit less of it to the atmosphere.


If one uses electricity from wind turbines when they are generating excess power as for instance around midnight to produce synthetic methane the accounting works out since there is no economic way to store electricity.


@ Jus7tme

You have two goals I have one. My goal is to use fossil fueled cars for as long as they are cheaper and more practical than EVs. If and when EVs ever reach that point where they prove superior the market will determine the future of hydrocarbon fuels. Mandates from on high as you would like to see dictated aren't going to hack it.


@ Jus7tme

You're overlooking one big factor with e-gas: Germany, especially, has a big problem with surplus wind energy during periods of low demand. The power that will be used to make e-gas is essentially free; it would otherwise be wasted.

Other things being equal, it would admittedly be more efficient to use the power to charge EV batteries. But EV batteries are still very expensive for the energy they store. E-gas taps into an existing gas infrastructure and delivers far better driving range.


I should point out this line from the second to last paragraph: "The CO2 used in Audi’s e-gas plant is a waste product from a nearby biogas plant"


even better.


I didn't even know Audi had it's own synthetic methane, but I wonder how much of it is a marketing ploy. I agree with the argument that there are systemic energy losses when you convert CO2 to methane using electricity, but my bigger concern is that drivers won't always be near a fueling station with e-gas available and will just end up using cng anyway.

And on a personal note, g-tron is probably one of the silliest names I've ever heard. But I still love Audis.


A biogas plant produces methane and CO2, the CO2 would be released to the atmosphere if not used for another purpose. This puts that CO2 to work making fuels rather than emitting it AND burning fuel in the cars.


NG is delivered through a network of pipelines so it's a simple matter to just pump the SNG to all the stations on the network through the same pipeline. Each driver will get a percentage of SNG in his tank that's equal to the percentage of SNG supplying the network.



>> It is not phony accounting at all. If I burn gasoline in the car and coal in the power plant, I produce more CO2.

No, the accounting is completely wrong and as phony as it gets. If you burn coal (or natgas) to make electricity to make H2 to make syngas to run in cars, then that produces more CO2/mile than just running the natgas directly in the car, or running on gasoline for that sake. If you have windpower, use it do displace natgas and coal-fired electricty DIRECTLY. Do not add extra steps that lose energy as heat and produce more CO2 than if the windpower electricty is used directly.

This should not be difficult to understand, but there is a lot of propaganda out there by people who want it to look like they are saving CO2, when in fact they are making more CO2 than will be emitted by using best practices.



>>You're overlooking one big factor with e-gas: Germany, especially, has a big problem with surplus wind energy during periods of low demand. The power that will be used to make e-gas is essentially free; it would otherwise be wasted.

This is not true. Allow me to explain. There is no surplus of wind power in Germany, even in the middle of the night. Germany's grid mix is 60% fossile, 20% renewable (about 18% wind and 2% solar), and the the rest is nuclear (still) and hydro, some of it imported. With nighttime load being MORE THAN HALF of daytime load, there is NO WAY 18% can be an oversupply of windpower at any hour of the day or night.

There IS a grid problem to get the windpower delivered from where it is produced to where it is needed. And there is contention between windpower and the fossile plants, who do not want to dial down their plants at night, because that reduces their profits. THAT is the problem, and a source of much self-interested propaganda (is there any other kind?) that has mislead a LOT of people.


One more thing: If we EVER get to the point that there REALLY is a continental surplus in Europe or USA or Asia, of use-it-or-lose-it renewable power (such as wind power or solar power), there is a simple solution:

Transmit the power to a hydroelectric dam (in Switzerland, Austria, Germany/Bavaria, French Alps, Norway, Sweden, Italy?) and and use it to pump water back up to the reservoir. This is called pumped hydro storage, and there should be a lot more of it. It is highly efficient, and produces hardly anyextra CO2, unlike these harebrained e-Gas/syngas schemes. Pumped hydro storage does cost some money. But so do the worse alternatives.

The comments to this entry are closed.