Wednesday, January 15, 2014
Audi backs Direct Air Capture on the road to zero-carbon fuels
In an exciting milestone for Direct Air Capture (DAC) systems, Audi has recently announced that it is teaming up with VEC finalists Climeworks in their quest for the world’s first carbon-neutral synthetic fuels. The ambitious Audi e-gas project reacts hydrogen produced using renewale energy with CO2 to make synthetic methane, or e-gas, that is used as high-performance fuel in specially-designed engines. Through their partnership with Climeworks, they may soon be sourcing that CO2 straight from the air.
Credit: Audi Encounter 1/2014
Climeworks’ technology relies on chemical sorbents bound to a carefully-designed cellulose matrix that selectively “stick” to dilute CO2 molecules in ambient air as it passes through. When the sorbents are fully loaded with CO2, they are heated to around 95 degrees Celsius until they release the trapped gas in a concentrated stream that is more than 99% pure. Capture of CO2 from air has in the past been questioned over its energy requirements, but Climeworks’ efficient design aims to use waste heat to meet most of these demands, potentially allowing air capture to piggyback on other industrial processes at the Audi plant. Once the CO2 is captured, it will be combined with hydrogen that Audi produce from water by electrolysis with renewable energy to make synthetic methane fuels that have a near-zero carbon footprint.
Climeworks has been successfully operating a demonstration plant producing 4kg of pure CO2 per day for the last twelve months. Image credit: Audi Encounter 1/2014
People may ask why are Audi so interested in Direct Air Capture technology to produce their CO2? Why not use CO2 captured from power stations or, as is currently the case, produced from local biogas plants? Dr Hagen Seifert, Audi’s officer for carbon footprint, future materials and renewable energies, explained that DAC CO2 can have important advantages both in terms of its carbon footprint and its economics. Unlike CO2 captured from fossil fuel combustion, DAC-CO2 forms a completely “closed circuit” with fuel combustion. Capturing fossil CO2 only to convert it to another fuel only delays its release into the atmosphere, but when fuels made from DAC-CO2 are burned, it forms a closed carbon cycle between the fuel tank and the air that leaves fossil fuels in the ground. On top of that, CO2 in the atmosphere is present everywhere, so Audi can locate their plants wherever they want without the need for expensive CO2 pipelines from the nearest power station.
The Climeworks team
The chemical extraction of CO2 from the atmosphere is not the only suggested potentially scalable and sustainable greenhouse gas removal option. Many proposed activities and several of our finalists work with the ways of taking carbon out of the air that nature has researched and developed for itself; namely photosynthetic organisms. However, biomass can have its own challenges. Bioenergy and biofuels have come under fire recently for a range of reasons, not least of which is the suggestion that they can be far from carbon neutral if not sustainably sourced. Growing biomass also takes up a lot of land, and it must be harvested and transported to centralised points for use.
“synthetic fuels offer a vital early route to developing and commercialising DAC technology”
DAC systems and other sources of atmospheric CO2 should not be considered rivals, however. The world is a very diverse place, and it will be more a case of understanding which systems work best in each real world instance (this may also apply when considering renewable hydrocarbons against electric powertrains!). For the Audi project, however, an on-site DAC plant would help avoid the problems of managing upstream biomass resources. And as Dr Seifert explained, installing their own DAC system could also pave the way for Audi making e-gas on much larger scales, as they will no longer be limited by the modest local supply of biogas-derived CO2. And, as VEC saw at several CO2 utilisation conferences last year, such as the one run by the German Nova Institute there are further processes capable of converting syngas into more complex hydrocarbons, from dimethyl ether, to gasoline, and even jet fuel and rocket propellant!
The Audi A3 g-tron, designed to run on carbon-neutral synthetic fuel. Credit: Audi Encounter 1/2014
Of course, turning captured CO2 into fuels doesn’t qualify as Greenhouse Gas Removal (GGR) as the CO2 is re-released to the atmosphere as soon as the fuel is burned in a car: the process will be carbon-neutral at best. However, synthetic fuels offer a vital early route to developing and commercialising DAC technology in the absence of a strong carbon price and climate policies that appropriately contextualise and reward Greenhouse Gas Removal as well as reduction. The synthetic methane produced could also be used as a valuable building block for a new generation of carbon-negative plastics, which can be more properly considered GGR. The commercial success of Audi’s carbon-neutral fuels using DAC systems would also be a resounding demonstration that the unique advantages of Direct Air Capture can give it a serious role to play in the future of our energy system.
This is why, even though both the partnership and the technology itself are at an early stage, this announcement is a very exciting moment for Direct Air Capture as a whole. It is a great sign for the future of the technology that such a significant player in the automotive industry has recognised the value and commercial potential that DAC systems can provide, and has stepped up to help to drive this emerging technology forwards.
By Guy Lomax
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