[ed]

So the ELI5 is they burn crop waste, harvest the heat and bury the carbon-rich ash. This process is called BECCS. (Not totally right - see 'pkrein’s comment below.)

The upper bound on capture is pretty good! Almost 70% of yearly CO2 emissions.

> Intergovernmental Panel on Climate Change (IPCC), suggests a potential range of negative emissions from BECCS of 0 to 22 gigatonnes per year [1]

> Human activities emit over 30 billion tons of CO2 (9 billion tons of fossil carbon) per year [2]

1 - https://en.m.wikipedia.org/wiki/Bioenergy_with_carbon_captur...

2 - https://en.m.wikipedia.org/wiki/Carbon_dioxide

[pkrein]

Actually we aren’t burning the biomass, we’re heating it without oxygen (pyrolysis) to create a transportable biomass intermediate called bio-oil. That bio-oil is rich in carbon, molasses-like consistency, and the overwhelming odor of barbecue sauce. Today we primarily pump that bbq sauce underground as carbon removal (Biomass Carbon Removal and Storage - BiCRS), but in the future it could be used for BECCS processes like you outline.

[dbcurtis]

How is this an overall improvement over leaving the corn stalks in the field to decompose and return nutrients to the soil? This process moves soil nutrients away from point of origin. (Serious question from former Iowa farm boy who still owns corn ground operated by others. Should I let my tenants ship stover away? I want to be a good steward of the soil. )

[pkrein]

The process separates the biomass carbon into bio-oil, and the NPK in the biomass separates into the biochar/ash (2% of the N, 70% of the P, >90% of the K). That biochar/ash goes back into the soil. So we recover most of the nutrients, plus you get biochar which improves soil carbon, water retention, microbial health, etc.

https://charmindustrial.com/faq?question=how-do-you-sustaina...

[colechristensen]

Yes, but why is this better than leaving the biomass in the field and perhaps doing some soil building techniques?

You also need to hire some farm kids or pay for some scholarships to get interns. Some of the problems you described solving over months would have been trivially solved by someone with farm experiences.

You’d really benefit from going to farm auctions, finding one of these, taking it apart, and adapting the mechanisms to your purposes. https://youtu.be/aYv8aDRv998

[pkrein]

Leaving the biomass on the field results in the CO₂ going back into the atmosphere (~80% within 2 years): https://cdnsciencepub.com/doi/10.4141/cjss2010-055#T0002

By contrast, our process retains the nutrients, improves the soil health relative to the baseline of just leaving it, and you get permanent carbon removal.

Yes, we're hiring for great mechanical engineers with experience in these areas ;) Lots to do!

[jonstewart]

How does removing the biomass improve soil health?

[Fomite]

Yeah, the West Coast Ag School professor in me in flinching at some of this.

[RosanaAnaDana]

Whatever their answer they'll need to account for the fuel cost of the trip to a facility, lifecycle cost of the instrumentation, and fuel cost of a return trip for where ever the whatever is going to go.

I can tell you right now having done experimental LCA previously, its not gonna pen out. The cost of moving massive amounts of 'stuff' to do 'something' with it when its an extremely low margin, low value add product; this will end up generating more CO2 than it sequesters.

If you can't do it in place, you likely can't do it.

[YeGoblynQueenne]

Couldn't the bio-oil generated by the process be used to power the transport and supply lines? Or don't the maths work out? I don't know any of the numbers here...

[RosanaAnaDana]

You have to drive the 'stuff' to 'somewhere' to turn it into 'whatever'.

The stuff costs more in CO2 to drive to the place than you get from turning it into 'whatever'.

[YeGoblynQueenne]

But is this a general and inescapable rule?

[dreamcompiler]

That would defeat the purpose. Burning the bio-oil to extract energy from it would just pump CO2 into the atmosphere.

[YeGoblynQueenne]

Yes, I understand that, but I thought that most of the CO2 is bound to the ash that's supposed to be buried underground? So there would be a net reduction of CO2, even if the bio-oil was burned?

[dbcurtis]

Yes, that is my take. It only works economically if the soil nutrients come back to the field, and it costs no more (net) than adding a stalk chopper to the combine.

Extra trips over the field burn fuel, and something needs to pay for the dollar cost of that (in added fertilizer value or something) not to mention the net carbon emissions of burning diesel to go over the field again.

[colechristensen]

You usually have to have entirely renewable generated electric powered processes in order to actually sink meaningful amounts of carbon.

And even then, to actually sink carbon the correct thing to do would be to electrify the farm machinery for a much higher carbon ROI.

[jonstewart]

(Another former Iowa farm boy) This is a CO2 sequestration process, and one still in development. The carbon in the corn stalks is obviously pretty neutral—it’s the petroleum for tractors, drying, and fertilizer that are the CO2 emissions problem.

For soil health, I think you’d want your renter to go no-till (if isn’t already). And then for emissions, look into putting solar panels wherever, seeing whether there are electric/heat pump dryers available (???) if you have drying bins, and encouraging renter to use biodiesel.

[carbadtraingood]

Decomposing biomass releases almost all its mass back as CO2 into the atmosphere, very little is sequestered.

This approach removes carbon from the atmosphere permanently.

It's also (probably) a net energy producer and it doesn't require creating massive piles of decomposing plant matter everywhere.

[goda90]

This depends on the conditions the biomass is decomposing in. A lot of carbon can be captured in the soil if handled well. No till, no spray, cover crops, and managed grazing of the cover crops can create an environment where the soil is a carbon sink and a better base for future crops.

[carbadtraingood]

Yes. And also no. Practices like that are good, but the majority of your carbon sequestration will come in the form of the roots of plants. (This is part of why no till is good.)

Getting surface vegetation to deposit carbon in the soil long term is trickier. You aren't wrong, but it's also not as simple as some folks believe. Just cutting the corn stalks and cobs and leaving them on a field won't put much carbon back in the soil.

[ciphol]

Possibly the bacteria which decompose the corn emit CO2 as they "burn" the corn for their food?

[bob29]

How are you heating it? How are you powering all the chippers, blowers, conveyer belts, and other machinery? Along with the transportation of crop residue to your facility, how much carbon is re-emitted with your consumption of all these industrial products of the primarily fossil fueled powered energy system?

[carbadtraingood]

Pyrolysis is an energy positive reaction. It requires an initial heat input, but after getting started it produces more heat than it needs. That heat can be used to generate electricity or warm water.

[bob29]

Pyrolysis is entirely endothermic - it requires applying heat to biomass. Pyrolysis yields a vapor that will combust in the presence of oxygen and release energy. The energy released in the combustion of pyrolysis products can be used to drive further pyrolysis. A "Top Lit Updraft Gasifier" is a simple apparatus to achieve this.

Capturing the heat from pyrolysis in this way does however convert the pyrolysis vapor from hydrocarbon into combustion byproducts, namely C02. This company claims to be condensing all of these hydrocarbons, not combusting them.

For a nice and understandable example of pure pyrolysis without combustion, there is this project [0] wherein an airtight vessel is loaded with biomass, heat/energy is applied with electrical resistive heating elements. The pyrolysis occurs and the resulting vapors are captured and stored as a low pressure vapor for later use in cooking or powering internal combustion engine.

[0]https://www.patreon.com/posts/story-of-thing-i-61916621

[dreamcompiler]

Pyrolysis could in theory be done with concentrated solar thermal energy. The issues would be:

-- How much mirror area [heat] would be needed?

-- Mirror geometry: Troughs may lend themselves to continuous processing and gas recovery a bit better than central point concentrators but they provide less heat potential.

-- Can the economics work if you only process when the sun shines?

[carbadtraingood]

Totally. I am currently experimenting with TLUDs for waste products from some forest land I own. I didn't realize they were also attempting to capture the gases from pyrolization rather than using them to continue the pyrolysis.

In that case, you are totally correct, they'll need an input heat source.

[mnw21cam]

Neat idea.

My main concern is about whether you're sealing all the plant nutrients deep underground too, or are they separated out at some stage?

As a world, we're going to need to put all those nutrients back into the soil to be able to keep growing stuff. Particularly phosphorous has limited mineable stocks.

[photochemsyn]

I'd guess the ash/gunk remaining from the pyrolysis would be a mixture of carbon, phosphorous, maybe some nitrogen. It'd probably make a decent fertilizer/soil amendment, particularly for degraded low-carbon soils.

[CoastalCoder]

Okay, I've got to ask: Does it actually taste like BBQ sauce?

[ryanmcbride]

probably mostly tastes like carbon but you might notice a smokey aftertaste

[mcronce]

To be fair, the smokey flavor you get from barbeque is primarily carbon

[ryanmcbride]

Yup I just assume bitterness would be front and center

[ed]

Oh, this is your company! I heard you were working on this and thought dang way to go Peter.

Are there companies buying bio-oil yet? If I understand correctly, I like that you’re plugging into a larger system and applying engineering to make a piece of it more efficient. It’s always easier to get bigger than it is to get smaller!

[rmccue]

This is pretty cool!

Presumably it takes some amount of energy currently to run this process, so the "cost" of the carbon removal is energy usage currently. Would a BECCS process remove the need to use external energy altogether?

[soco]

So out of the 30 gigatons of CO2, up to 22 are from biomass? That's way, way more than I would have thought...

[Imnimo]

I think the 22 is not how much is currently emitted from biomass, it's the upper bound on how much we could store if we replaced a bunch of energy generation with this process.

[philote]

I think the meaning is that out of the 30 gigatons of CO2, 22 gigatons can be recaptured ("negative emissions").

[soco]

Right and that sounds like a lot to me. I hope they're right.