Low carbon, high hopes

Written by: Maxine Perella | Published:
Shougang demonstration facility in China

Making fuel and low-carbon chemicals – including aviation fuel – from waste gas could be a sustainable alternative to landfill or traditional incineration, thanks to one company’s new technology. Maxine Perella reports

Carbon recycling might not be the most immediate topic that springs to mind for waste industry professionals, but given the global focus on Paris climate goals and reducing international CO2 emissions, new solutions to tackle waste carbon – especially from heavy industry – are attracting a lot of interest.

One promising contender is LanzaTech’s gas-to-liquid technology, which is opening up new channels for the production of low-carbon chemicals and fuels that displace petroleum without the environmental concerns associated with crop-based biofuels.

One market where LanzaTech’s vision is set to take off is in commercial aviation – the technology provider has been working with Virgin Atlantic Airways to produce the world’s first batch of low-carbon jet fuel sourced from the industrial waste gases of steel mills.

The process is based on gas fermentation, so instead of using sugars, LanzaTech utilises the waste gases from mill flue stacks which would otherwise be combusted and emitted. Bacteria (rather than yeast) then feed on the carbon in the waste gas and multiply, producing an ethanol by-product which is then refined further to produce the aviation fuel. Each gallon (US) of ethanol produced can be converted into 0.5 gallons of low-carbon jet fuel.

Game-changer for aviation

LanzaTech claims its process delivers at least a 65% reduction in greenhouse gas emissions compared with conventional aviation fuels. Virgin founder Sir Richard Branson has gone so far as to call the project a “real game-changer for aviation”, saying it could significantly reduce the airline industry’s reliance on oil within a generation.
In February, 1,500 gallons of the low-carbon jet fuel were produced from a demonstration facility at steel company Shougang in China. The fuel now has to undergo a series of rigorous approval processes before it can be used in a commercial flight.

Besides the potential benefits to airline operators such as Virgin Atlantic, steel producers also have a keen interest in making this technology work, according to LanzaTech CEO Jennifer Holmgren. “Across the sector, there is a drive to reduce carbon emissions, and many steel mills are eager to turn their waste emissions into an opportunity rather than a liability,” she says. “We are currently working with a number of steel companies globally, including Shougang, one of the largest steel companies in China, where we are building our first commercial facility that will be operational later this year. We are also working with the world’s largest steel company, ArcelorMittal. Our first commercial facility in Europe will be at one of its flagship mills in Ghent, Belgium, with potential to roll out to other sites.”

Globally, around 1.7 billion metric tonnes of steel is produced every year. LanzaTech estimates that its process could
be retrofitted to 65% of the world’s steel mills, offering the potential to produce 30 billion gallons of ethanol, or 15 billion gallons of jet fuel each year. This figure would represent just under 19% of all aviation fuel currently used worldwide.

Currently the technology has the potential to capture and recycle one-third of the waste carbon from steel facilities. But what about the remaining two-thirds?

Holmgren explains that because the bacteria used in the process draw on the carbon as both an energy and hydrogen source, they cannot recycle all the carbon into ethanol.

“To recycle 100% of the waste carbon, our organism needs an external hydrogen source. If there were an unlimited supply of hydrogen at the mill, you could get to 100% carbon capture,” she says.

Outside of the steel industry, LanzaTech is also looking to source other types of waste feedstock to scale up its operations – including municipal solid waste (MSW).

“Our process is fully flexible and can use a variety of waste gases,” explains Holmgren. “We have demonstrated the process using waste emissions from the ferroalloy and refining sectors and we have an operating demonstration facility that takes gasified MSW and makes ethanol.”

Lessons learned

In order to use solid waste, a gasifier is required to convert it into a syngas that the microbes can feed on.

“At present the MSW at the site we are operating on is gasified and the resulting syngas is combusted to make power,” says Holmgren, adding that a LanzaTech fermentation unit sits within the same site, where it takes some of the syngas for conversion into biofuel, producing around 20,000 litres a year.

The Asia-based facility has been up and running since 2014, with MSW feedstock sourced from a local municipal waste site.

Asked what learnings have come out of this particular demonstration facility so far, Holmgren replies: “The main learning is that we now know that our process can effectively convert gasified MSW to fuels and chemicals.

“Before the operation of the plant, we had tested the process on industrial off-gases from the steel sector, but hadn’t shown that using gasified MSW was possible. The successful operation of this facility, and the continuous data we have generated, have enabled us to improve on the process and show that this is a viable alternative to power generation and combustion.”

She adds: “The key thing we need to add to our process when using MSW or any other waste biomass resource is that we need a gasifier. In addition, the gas produced from the gasifier needs to be cleaned before going into our fermentation system. We have been able to do this at our demo plant and it has shown no adverse effects on the process.”

Holmgren believes that if such a solution were scaled up, it could offer a more sustainable alternative to landfill or traditional incineration.

“I can see no reason to bury waste in the ground when you can gasify it and reuse it to make new products that would otherwise come from fossil resources.”

She takes plastics waste as a case in point. “Plastic that can’t be recycled would today be incinerated. If you avoided incineration and fed the resulting gas to our process, you could make not only fuels, but platform chemicals that could make new plastics – avoiding the need for more fossil resources to make those plastics. This is the circular economy in action.

“You can keep gasifying or recycling these products and keep the carbon locked up in the product. It’s a new way of looking at carbon capture and sequestration.”

Creating other opportunities

LanzaTech has also licensed its technology to a US industrial biotechnology firm, Aemetis, which will have scope to use a variety of agricultural biomass wastes and residues including forestry, dairy, orchard, vineyard, corn, rice and wheat to make ethanol.

While Holmgren says that this particular commercial unit is not yet up and running, the intention is to roll out the application across California. “The gasified orchard waste produces a gas very similar to that produced through the gasification of MSW,” she adds.

Like most innovative technologies, the big question is whether these applications can commercially scale. The backing of Virgin Atlantic is a tremendous boost in this respect. Holmgren says any new aviation fuels need to be affordable as fuel is the top business expense for airline operators.

“There are a variety of new technologies out there today, but they are still developing and the volumes produced are too small to make economic sense.

“Across the industry, the main challenges now are to scale up production and make the fuels cheaper. LanzaTech is in a good position, in that we are building our first commercial units today with the first one coming online later [this year] in China,” she explains.

Importantly, LanzaTech’s low-carbon jet fuel is also designed to be exchangeable with regular fossil fuel kerosene, meaning that the same fuel systems and aircraft can still be used.

This is an essential consideration in the aviation industry where infrastructure is shared across different stakeholders. It is hoped that the fuel will be tested in a non-commercial ‘proving’ flight this year – data collected from this flight will then hopefully open the door for the fuel to be used on routine commercial flights.

In time, this could also help pave the way for LanzaTech to fund and build an alcohol-to-jet-fuel plant in the UK. “We would very much like to have a facility in the UK, but making this work requires many stakeholders, and so we are unable to provide more details at this time,” says Holmgren.

She goes on to add: “In our mind, the UK can become a leader in this space, as a hub for clean low-carbon
aviation fuel.”

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