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Fireside Chat – Autothermal Pyrolysis of Woody Biomass – Dr. Sean Rollag

Dr. Sean Rollag, an R&D Engineer at LanzaTech, and Dr. Andrew Jones at Activated Research Company discuss Dr. Rollag’s Ph.D. thesis research on autothermal pyrolysis with a goal of maximizing reactor productivity while producing sugars from biomass in a carbon-negative way.



2.[01:21]Research Goals


4.[03:43]Research Motivation

5.[05:15]Unique Pyrolysis Approach


7.[10:08]Pyrolysis – Climate Change – Decarbonization

8.[11:51]Analytical Challenges


10.[20:09]Career Advice

11.[22:09]Last Act


Hi everyone. I’m excited to be joined today by Dr. Sean Rollag, an R&D Engineer at LanzaTech. Today, we’re going to talk about his Ph.D. work on Pyrolysis when he was at Iowa State University under the direction of Professor Robert Brown. Sean, how are you doing?

I’m doing well Andrew, thanks for having me.

Thank you for coming. I love talking to other scientists, and what you’re doing in pyrolysis is near, and dear, to my heart. It’s what got me interested in Chemical Engineering to begin with – so I’m super excited to hear about who you are, how you got into this, what your work led to, and where you see the future going.

We’ll also talk about your paper titled: The Role of Catalytic Iron in Enhancing Volumetric Sugar Productivity During Autothermal Pyrolysis of Woody Biomass. Before we jump into that – what does it mean?

Research Goal[01:21]

The goal of the research was driven by the idea of process intensification – of trying to maximize the productivity of a given reactor, or a given chemistry, and then making it as small as possible to enable modular manufacturing. We wanted to produce as much as possible from a given volume of biomass, and then containerize the reactions so we could scale the entire process.

I see the term “intensification” thrown around a lot – so that’s making things happen faster so you can go smaller – is that right?


A lot of our funding came from the RAPID (Rapid Advancement in Process Intensification Deployment) Institute which is focused on process intensification and research. That was the main driver, and we found an avenue where we could significantly intensify the pyrolysis process.

Great. I’m excited to jump into that, but before we do – how did you get into this field?


Well, I grew up on a farm, where there are so many daily challenges that must be solved. From early childhood, I was tearing stuff apart and putting it back together – just trying to understand how things function at a basic level. Once you know that, you can build off it and do all kinds of crazy things.

My introduction to Chemical Engineering came when I read a book called The Alchemy of Air by Thomas Hager, which is about the Haber-Bosch process. I thought it was fascinating how they took a simple chemistry lab system that produced only a few drops, and scaled it through engineering and catalyst research to build the modern world of agriculture we know and feed everyone with. That inspired me with a “take an idea – make it real – change the world” sort of thing.

Haber-Bosch DID do that – they fed the world! Very cool.

So, what was the motivation behind you choosing pyrolysis intensification as the direction you wanted to pursue?

Research Motivation[03:43]

Growing up on the farm – my personal motivation was around: How do you help the rural economy and add value to it? Some of it is environmental – you “know” the rain should come at the right time – but weather changes, and it really impacts farmers. You can’t plan out the seasons.

The things we’re seeing – like the corn belt creeping north as it gets warmer – you see first-hand how climate change makes an impact. I really wanted to be involved in the Ag Industry. You can work on renewables and other areas – but I think pyrolysis could provide a big solution. We also see parallels in our business and personal lives – where climate solutions are good for everyone.

So, as a farmer you got to see some of the impacts of climate change?

Firsthand! The main thing was that the growing season is getting longer as the first freeze happens later in the year.

That’s pretty cool. So, you saw this climate change impact and it drove you to get excited about doing research to help mitigate it – or help in some way.

It’s a problem, and I want to find solutions to problems. I’m a problem solver, and, in my opinion, that’s what engineering is about.

I can relate to that. So, pyrolysis has been around for a while – what’s unique about what you were studying versus what everyone else has done?

Unique Pyrolysis Approach[05:15]

A previous grad student had developed a process for autothermal pyrolysis – where unlike conventional inert pyrolysis – you add air so you can combust products. That lets you generate the energy needed to drive the pyrolysis reactions required for process intensification.

You end up with a lot of heat and you can generate it at the center of a reactor. You can keep feeding more biomass – because you can always add more air. If you keep the two balanced, you can significantly increase the throughput of the reactor. Once you unlock that – you can make a ton of this bio-oil stuff.

What can you do with that?

It turns out there are trace amounts of sugar in the reaction – and we could do even more if we could add more sugar. The research turned into: How do we make more sugars from pyrolysis? That’s when I was brought in and began to encounter issues with some of the traditional treatments of acid washing and sulfuric acid passivation.

So, trying to increase the amount of sugar yield is important because it’s a feedstock to certain industries?

Cellulosic sugars have a lot of value because you can ferment them into many different products. I’m taking sugar and fermenting it into various products and chemicals. Ethanol is a big one you want to help, but you can bioengineer bugs to grow many different compounds from those sugars. You need the sugar molecule building blocks in the first place, and the enzymatic hydrolysis approach has its own issues. You’re looking at ways to get sugars out of biomass. It’s there, but there’s not much. If you pre-treat it – you greatly increase it – so it starts to look attractive. It’s an area that’s ripe for development work to be done.

It looks like you were quite successful. You increased sugar yields from 5 to 20 percent. That’s pretty cool. What were the biggest challenges you came across while doing this research?


There were several – but the biggest challenge was the scale up. It’s easy to do micro-pyrolysis experiments. You can do dozens of those a day. When you start to scale it up, the actual pretreatment process wasn’t working, and there was a lot of redesign effort that became more of a shakedown test.

How long does it take for the chemicals to diffuse into the biomass surfaces? When we were dealing with a powder. That’s not something we initially considered, so we struggled with that for quite a while. Then, trying to avoid a lot of the effects of the reactor agglomeration – you can’t see that until you get to an actual continuous reaction system. There were a lot of struggles.

You did scale it up – so you went from this micro-pyrolysis scale – how big did you end up going?

The largest scale we got to was a pilot scale. We reached a half ton a day which was hundreds of kilograms of biomass. That was a lot of fun – to start with an idea – and then, suddenly, people are holding liter bottles of the oil.

What a cool experience to be able to do that in grad school. My work never got bigger than a few micrograms. That’s pretty neat.

That’s a unique approach of the Brown Research Group – that ability to scale up to pilot scale testing.

I’ve worked in pyrolysis a bit, and it’s being talked about more and more as decarbonization is brought into the limelight. What are your thoughts on the role pyrolysis might play in climate change and decarbonization?

Pyrolysis – Climate Change – Decarbonization[10:08]

Before I went to grad school, I hadn’t heard much about pyrolysis. It’s not a field people talk about – but I do think it’s going to get its day in the spotlight.

Through the fermentation of sugar – you can make all the chemicals you need to produce clothing and other things. The advantage of pyrolysis is you can make those sugars and do it in a carbon-negative way.

As we get further into global climate change – where there’s too much CO2 in the atmosphere – we need to start pulling some of it out. Pyrolysis lets you do this, and it generates a little biochar stream you can sequester. If you’re pulling CO2 out and using electricity to turn it into fuel – at best that’s carbon-neutral. Using pyrolysis, you can get to carbon-negative and start drawing down the CO2 in the atmosphere to meaningful levels and start reversing the effects we’re seeing.

I love that.

Let’s shift gears to the analytical challenges you had. What did you measure in these experiments? How did you do that? What were the challenges in doing that with pyrolysis?

Analytical Challenges[11:51]

The best part of the research was obviously the scale up – but you have to start small – so it was a little micro-pyrolizer into a GC-FID with an ARC Polyarc® system in there to really help with the quantification of all the different compounds.

Pyrolysis produces just a “soup” of different molecules, so you can’t go through and try to quantify by building calibration curves for every single molecule. Our system was to have a Mass Spec and the Polyarc® FID system so we could easily identify hundreds of compounds. It really saved us a lot of time building calibration curves.

There are a lot of unknowns. We added different catalysts, and the unknowns changed in different ways – so which catalysts were effective and which ones weren’t effective? Having that rapid quantification of different products was very useful. Then, with our lighter fractions of oxygenated molecules which you can’t really detect very well with an FID. So again, having that Polyarc® system allowed us to look in kind of the lighter compounds, formaldehyde and stuff like that. The really light organics that with certain catalysts you can make a lot of them, but you can’t see them. It’s tough to quantify how much difference the catalyst made, and we definitely had that happen.

The difficulty we had with the system was that the levoglucosan, which was our target molecule, has such a high boiling point that it was very difficult to get it out of the column after every test. If you ran for a week – you’d have to clean out your column liner. It filled up with some heavy tars. You had to flush your columns all the time. It was tough. The molecule we cared about was the hardest one to get a solid baseline on because it just wouldn’t go away after you ran a sample.

You were right on the limit of gas chromatography – getting into the liquid chromatography realm. How hot were you going in the GC? Did you get up to 400°C?

I think we got up to like 200°C+ on some of them. I think it was like 300°C. Harsh conditions. The GC folks wouldn’t be too happy if they knew what we were doing.

Those GC components start to get unhappy when you get really hot. You start to bake off that polyimide and the column turns brown.

Were there any other challenges getting the analytical data you wanted? Were you able to get complete, or near-complete, carbon closure? When you use the Polyarc®, you have a good idea of where your carbon is going.

We could get high carbon closure. The issue with pyrolysis is you still end up with dimers and trimers that you’re just not going to get with a GC.

It’s in your inlet liner.

The phenolics would polymerize as well – so you’re not getting those either – so I had some issues with some of the carbon closures. Some of the pre-treatments were a lot better than others at actually fractioning everything into monomers pretty well – but some of them left everything as trimers.


The phenolic polymers were kind of impossible. Even the liquid chromatography couldn’t handle some of those lignin compounds. We had some pretty good results with the lighter compounds. Once we kind of got the system down, of the method you need, stuff like that.

One of the things we never quite figured out is there’s always a mismatch between how much levoglucosan we could quantify – and how much glucose we could hydrolyze from our samples. We always ended up with more glucose that we put in as levoglucosan so there’s always a theory we had dimer, or something, that’s just not coming out of the GC that’s getting hydrolyzed to glucose. So, in the paper, at least, we tried to report everything on kind of the glucose basis. So, those practical sugars that if you were to commercialize it, that’s what you would end up with is this much glucose. You couldn’t quite quantify that on the small scale due to the mismatch there. It’s coming from somewhere, but we’ve never quite identified what the source was.

There are still some challenges. We need someone to invent the GC/LC that can do everything – dimers, trimers, etc. I’ve thought about doing it, but we’re not there yet.

It sounds like the Polyarc® was helpful – which I love to hear – that makes me happy that we have customers out there using it.


We had two Polyarc® systems in our lab, and there was some fighting amongst grad students as to who got to use those GCs because those were the coveted ones. You had to have a good argument for “why.” “I need to use that one because I need to identify all these compounds.” If you’re looking at just one compound it was like: “NO! we’ve got a calibration curve for that one. You don’t get it; this is not important enough for that.”

It sounds like we need to sell you guys more. I’ll go back to Professor Brown and talk to him.

You had a lot of great success with this, and, obviously, the yield gains were huge. What questions remain – and, looking into the future, what do you want to see next?

There are still some questions on the fundamental side of things. We identified this trend of the S (sinapyl or syringyl) and G (coniferyl or guaiacyl) lignen being very important in determining why there’s a separation of hardwoods and softwoods which has a melt formation. More fundamental research into what is the mechanism behind why these two lignen molecules or monomers behave so vastly differently with ctalyst loadings. Some of those are correlations we identified but the reasoning behind it is a large unknown. We did investigate it, and there is another paper published on that, but I don’t think we would find that because I think there are still a lot of answers to that question. True fundamental effect I’ve just kind of got a correlation.

Is that complicated because there’s just so much going on in these reactions – it’s not an A to B reaction?

We asked some of the DFT model guys if they could build this dimer – and, well, that’s computationally complex, trying to figure out how this very different catalyst or interactive or what state those catalysts were in that…


It’s quite a challenge, especially with the complexity of the biomass system. Once you’re at the crossing you can get the end of the cellulose and cellulose fractions – obviously not steady-state isothermal conditions – you’ve got all these changing fluctuations and denautilizations, it’s a very complex system to try and find a lot of what I think you need – you need to be able to probe it at that level to understand this.

This question is more for the students out there who are making that tough decision as to whether they do a Ph.D. or go into industry right away. What would you tell other students who are looking to get into this field or potentially do research here?

Career Advice[20:09]

I would say you really got to want it and have a love for science because it consumes a lot of your life. It’s not 40 hours a week – it’s 7 days a week, 24 hours a day, because going to sleep you’ll have an idea and you’ve got to write it down quick because it’s possible you can never really turn it off. It’s more consuming at times. There are some really slow periods. You might run 30 tests and not have any success – and then you might run one test and it just branches off into all these other discoveries. You got to love the slow times as well. I’m still learning things. It’s not exciting stuff, but every day I’m learning something that was unknown to the world before. You need that kind of mentality to drive you – OR – it might be better to just go into industry right away. It’s a process.

I agree with that. I think Ph.Ds. are wired a little differently. Maybe our tolerance for pain is higher?

I’ve had people say to me – “I haven’t found a job yet…maybe I should go to grad school…buy myself some extra time to find a job.” That’s not the motivation you want. You’ll be there six months, find a job, and then it’s “oh I don’t want to be here. I’m just wasting my time at grad school.”

I think that’s great advice. This will be valuable to students, and Ph.Ds. and people in the field, and, hopefully, some people who are not scientists.

Last Act[22:09]

I appreciate your time, Sean, this is fantastic. Keep up the good work. It sounds like you’re in industry now and changing the world in other ways. We’ll keep watching what you’re doing.

Hopefully, I do get to make some big changes to the world. I’m still working on it.

Thanks. Awesome.

Thanks for your time as well. I enjoyed talking about my research, and I’m glad other people want to hear about it too.

Thank you to our guest, Dr. Sean Rollag, for your time today. It’s been wonderful. You’re doing a great job on some interesting things. We’ll keep an eye out for the things you’ll continue to do. Thanks, Sean.

Thank You.

Let’s Change the World!

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