Pyrolysis - good or bad idea?

[CaptainPanic]

In another thread (this one), Essay mentioned pyrolysis. I am not a big fan of pyrolysis, so I wanted to discuss it. But it seems to be off-topic, so I continue the discussion here, in a separate thread.

 

Rather than work hard to grow special biofuel crops (or electricity-producing crops), we could easily convert any/all waste biomass into a crude biotar type of product. We already have the technology to refine crude oils and tars into high-grade fuels. Pyrolytic conversion of biomass into biotar can be an exothermic process (so extra energy can be captured), or it can be run more endothermically (via solar or other heating) to increase the yield of biotar.

I disagree. The bio-crude contains way too much oxygen (about 50% on a weight basis) to be compatible with standard petrochemistry. Refining the bio-crude is a separation nightmare, because the crude is still reactive and contains a lot of different components. Standard distillation is a bad idea, because the crude will react upon heating.

 

Removing the oxygen is energetically a bad idea, and economically impossible.

 

The large majority of bio-waste is lignocellulosic, and can be fractionated into its main biological components which can then be selectively reacted to desirable products (like cellulose --> glucose --> ethanol, as in the 2nd generation ethanol factories).

 

Chemical engineering of waste biomass seems to be much easier, safer, and more economical and natural than the genetic/agricultural engineering required to intensively grow pre-refined fuels--that still need further processing, storage, and transport.

Totally agree with this.

 

We only disagree on which technology is the best. I think that the pyrolysis just turns the biomass into a bio-mess (that must be the worst joke of the day).

 

Pyrolysis technology isn't so esoteric that it can't be used widely in backyards across the globe, helping rural and agricultural communities in third-world regions as well as providing opportunities on an industrial scale for careers and new industries in more developed and overdeveloped regions.

While it's technologically easy to use, there are a few reasons why I wouldn't advise local small-scale use of this technology.

1. CO (carbon monoxide) is formed. Fumes coming off the process are highly toxic.

2. Explosion hazards, fire hazards.

 

If people want localized energy, sun and wind are more practical and affordable. Or, alternatively, they can just burn the biomass.

[Ronald Hyde]

Pyrolysis can be combined with Hydrogenation to produce perfectly good fuels with lower oxygen content. The Germans used Hydrogenation during WW2 to supply themselves with gasoline after their supplies were cut of by the Allies. They used lignite coal as their 'biomass', which is similar to lignin.

 

We may need to resort to those methods in time, but as long as it is not economic that won't happen. Also you can Hydrogenate tar sands to get more and better fuel out with less pollution. One big problem is disposal of the waste, which may be highly toxic, and for instance, contain heavy metals or other toxins like Arsenic or Selenium.

[Essay]

We only disagree on which technology is the best. I think that the pyrolysis just turns the biomass into a bio-mess (that must be the worst joke of the day).

 

 

Thanks! And that is a great joke (I will use it in future); certainly the best laugh in my day today. All you point out is true, and I did make it sound as if standard petrochemical refining equipment would work on biotars/oil/acids --the biomess-- which they can't, directly. I would imagine even the variability in natural oils leads refineries to develop new processes and equipment, but a pyrolytic biomess is outside of the range of that variability.

 

But I'd also imagine that a lot could be learned from petro refining and applied to bio refining. Fortunately chemistry is still chemistry (just the same) for these petro and bio molecules. Learning to better refine fuels from more reactive oils/tars would require a bit more R&D, but is that a bad thing? Don't we need a new industry in this global economy?

 

The payoffs seem fairly large and easy, if one can control the "mess" factor, which is where chemical engineering comes in. As you say, it is a problem of 'which technology is best.' Or at least can be made to work well enough? What technologies and consequences are you comparing with pyrolysis?

 

And you're right. I wouldn't advocate for backyard pyrolytic distillation, especially any "still" in a densly populated area; but where people already cook with open fires (about 1 billion cook this way), a pyrolytic gasifier stove would expose them to much less carbon monoxide, and smoke/soot in general, compared with their current methods. Until they get electric or gas stoves, this would be an improvement. Some of the new gasifier stoves even generate enough extra electricity to power an LED and charge a phone--both needed items where they still cook on open fires.

 

And yes, when it comes to doing something that might explode, I'd advocate for doing that in an industrialized sector with good safetly and environmental regulations. But they would need trainloads of biomass for such an endeavor... which could fractionally replace trainloads of coal, I'd expect.

 

No doubt there are many hurdles to overcome and details to research and develop, but I think the general idea makes sense from a lot of angles: Many problems currently linked to our chemical oxidation of "fossil" carbon could be improved by including an economy based in part on a judicious chemical reduction of "ambient" carbon. Pyrolysis provides that opportunity, and it doesn't seem as if it would take much research or any sort of a "breakthrough" to pursue this avenue.

 

I agree that pyrolysis creates a biomess problem, but that problem seems puny compared to the problems we are trying to solve with advanced, resource-intensive, technology--often still waiting for some needed breakthroughs. I'm hoping the old primitive pyrolysis technology (which was fairly abandonded when cheap oil came along) will find new, cleaner and more efficient ways to contribute as the future develops.

 

~

[CaptainPanic]

Pyrolysis can be combined with Hydrogenation to produce perfectly good fuels with lower oxygen content. The Germans used Hydrogenation during WW2 to supply themselves with gasoline after their supplies were cut of by the Allies. They used lignite coal as their 'biomass', which is similar to lignin.

 

We may need to resort to those methods in time, but as long as it is not economic that won't happen. Also you can Hydrogenate tar sands to get more and better fuel out with less pollution. One big problem is disposal of the waste, which may be highly toxic, and for instance, contain heavy metals or other toxins like Arsenic or Selenium.

The Germans were desperate to get gasoline - they'd lose the war without it. The price didn't really matter. So, as you said in the 2nd part of your post, it's not economical, and it's not gonna happen. I have seen studies that support your claim that the use of so much hydrogen "has a strong negative impact on the process economics" (pdf warning).

 

It's like the US military: they can actually afford to use airplanes to transport fuel to the front lines. The price doesn't matter (it's apparently $400/gal (2nd source)!). But for the normal consumers, the price would be totally unacceptable - obviously.

 

You should never suggest that something is economically feasible because the military is using it. The military stands outside the economy. I'm quite sad to see that the pyrolysis (and also gasification) are often said to be feasible because the Germans used it in WWII. But that argument overlooks the #1 issue: the economy.

 

But I'd also imagine that a lot could be learned from petro refining and applied to bio refining. Fortunately chemistry is still chemistry (just the same) for these petro and bio molecules. Learning to better refine fuels from more reactive oils/tars would require a bit more R&D, but is that a bad thing? Don't we need a new industry in this global economy?

 

I think the most popular methods nowadays try to leave the main chemical components (sugars, aromatics) in one piece. So, the goal is basically to fractionate and to break up the biomass into chunks of 5 or 6 carbon atoms (with all the oxygen and hydrogen still on it). And then move on from there. It's a waste of energy to break up the biomass into smaller parts - like pyrolysis or gasification.

 

You're right that the biomass needs to be "refined" (I think "fractionated" is the popular word in biomass technology). The fractionation uses other methods though. Certainly not distillation, but instead things like solubility in water (and then a solid/liquid separation, like a filter) to make the primary separation. Playing with the pH or otherwise influencing the solubility of components is the primary trick I believe.

 

Alternatively, you can read up on steam explosion, which is a way to open up the structure of biomass, so that enzymes can break up cellulose. The glucose then dissolves and can be removed with a liquid fraction from the otherwise solid biomass.

 

In other words, it looks like most initiatives nowadays are looking for far more selective processes than pyrolysis.

[Essay]

In other words, it looks like most initiatives nowadays are looking for far more selective processes than pyrolysis.

...but they still use heat to help break up the biomass, don't they? I'm not wedded to using only heat to reform biomass into fuel, but I guess I consider anything done along those lines as modifications and improvements to the basic pyrolytic process. I'm all for finding better ways to modify pyrolysis, or any method that converts biomass into reduced carbon/fuels. Do you know of any other methods?

 

 

I've heard the military is looking for ways to be more green and self-sufficient in the field. At $400.00 per gallon, I'd think someone could figure a way to reform biomass into fuel for some fraction of that. Simply turning the biomass into charcoal, the most inefficient conversion, might make sense at those prices.

 

I know economics drives decisions, so we need to wait until the carbon reserviors, and the redox balances of carbon globally, are valued more. But the military need often drives technological developments and advances.

 

Whatever the particulars are in a given situation, pyrolysis offers the simplest way overall to restore the global redox balance of carbon--using ambient oxidized carbon to make more reduced carbon--slowing the conversion of fossil reduced carbon into ambient oxidized carbon.

~Or words to that effect

 

The fact that we can get heat and power, and even fuel, by using pyrolysis is just an added benefit--or perhaps incentive--from a Gaian perspective.

~

[Ronald Hyde]

The Germans were desperate to get gasoline - they'd lose the war without it. The price didn't really matter. So, as you said in the 2nd part of your post, it's not economical, and it's not gonna happen. I have seen studies that support your claim that the use of so much hydrogen "has a strong negative impact on the process economics" (pdf warning).

 

It's like the US military: they can actually afford to use airplanes to transport fuel to the front lines. The price doesn't matter (it's apparently $400/gal (2nd source)!). But for the normal consumers, the price would be totally unacceptable - obviously.

 

You should never suggest that something is economically feasible because the military is using it. The military stands outside the economy. I'm quite sad to see that the pyrolysis (and also gasification) are often said to be feasible because the Germans used it in WWII. But that argument overlooks the #1 issue: the economy.

 

 

 

I think the most popular methods nowadays try to leave the main chemical components (sugars, aromatics) in one piece. So, the goal is basically to fractionate and to break up the biomass into chunks of 5 or 6 carbon atoms (with all the oxygen and hydrogen still on it). And then move on from there. It's a waste of energy to break up the biomass into smaller parts - like pyrolysis or gasification.

 

You're right that the biomass needs to be "refined" (I think "fractionated" is the popular word in biomass technology). The fractionation uses other methods though. Certainly not distillation, but instead things like solubility in water (and then a solid/liquid separation, like a filter) to make the primary separation. Playing with the pH or otherwise influencing the solubility of components is the primary trick I believe.

 

Alternatively, you can read up on steam explosion, which is a way to open up the structure of biomass, so that enzymes can break up cellulose. The glucose then dissolves and can be removed with a liquid fraction from the otherwise solid biomass.

 

In other words, it looks like most initiatives nowadays are looking for far more selective processes than pyrolysis.

 

I don't think we should forget the roles that innovation and scale play in the economics and efficiency of chemical processes. A single innovation, reverse osmosis for example, can completely reform a process, boiler feed water treatment in this case, and other processes too. The manufacture of lead/acid batteries was similarly changed by the discovery of polypropylene. But scale too, something which works poorly on a small scale may work much better on a large scale, and vice versa.

[CaptainPanic]

...but they still use heat to help break up the biomass, don't they? I'm not wedded to using only heat to reform biomass into fuel, but I guess I consider anything done along those lines as modifications and improvements to the basic pyrolytic process. I'm all for finding better ways to modify pyrolysis, or any method that converts biomass into reduced carbon/fuels. Do you know of any other methods?

hmm... if you use the term pyrolysis in the broadest sense of the word, then you might be right. In practice though, those working in the field will not use the term pyrolysis for every heated process with a lack of oxygen.

All wet processes are not called pyrolysis. Pyrolysis is a dry process, where only the biomass is heated, without many additional chemicals.

 

I've heard the military is looking for ways to be more green and self-sufficient in the field. At $400.00 per gallon, I'd think someone could figure a way to reform biomass into fuel for some fraction of that. Simply turning the biomass into charcoal, the most inefficient conversion, might make sense at those prices.

 

I know economics drives decisions, so we need to wait until the carbon reserviors, and the redox balances of carbon globally, are valued more. But the military need often drives technological developments and advances.

They pay 400 $/gal for a gallon of fuel for planes and tanks, not for charcoal, which they can buy at the local market in Afghanistan for a few cents per kilogram.

 

Whatever the particulars are in a given situation, pyrolysis offers the simplest way overall to restore the global redox balance of carbon--using ambient oxidized carbon to make more reduced carbon--slowing the conversion of fossil reduced carbon into ambient oxidized carbon.

Yes, pyrolysis will increase the carbon content, reduce oxygen content... but that happens only in a significant way if you make the solid charcoal.

The liquid is still full of oxygen (and even contains water!). It a pretty poor fuel.

 

I think that currently the most popular way to turn biomass into actual fuels (like diesel) is to gasify it, then make diesel from syngas through the Fischer Tropsch reaction. (Again something the Germans used in WWII, btw). This is not economically interesting at the moment either, but might be used by the military.

 

The fact that we can get heat and power, and even fuel, by using pyrolysis is just an added benefit--or perhaps incentive--from a Gaian perspective.

 

You can get heat and power from just burning wood too. And the fuel you get from pyrolysis is, as I said before, pretty poor.

 

I don't think we should forget the roles that innovation and scale play in the economics and efficiency of chemical processes. A single innovation, reverse osmosis for example, can completely reform a process, boiler feed water treatment in this case, and other processes too. The manufacture of lead/acid batteries was similarly changed by the discovery of polypropylene. But scale too, something which works poorly on a small scale may work much better on a large scale, and vice versa.

The amount of hydrogen needed in a hydrogenation scales linearly with the scale (ok, that sounds pretty obvious). But as I quoted earlier, the price of this bio-crude is driven up by the use of hydrogen, not the high investment costs or something else.

 

The rule of thumb that bigger=better is only true with regard to the investment costs. And the investment costs are not the problem here.

Also, more innovations will not reduce the amount of hydrogen needed - innovations do not change stoichiometry!