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Leaving vs. pyrolyzing crop residues? #cropresidue


Kim Chaffee
 

All,

Could anyone tell me whether it is generally better for the environment to leave crop waste on the soil or to turn it into biochar? Let’s assume that, if the crop residues were removed and pyrolyzer, the farmer would immediately plant cover crops on the same acreage.

I assume that it might matter what type of crops we are considering: corn stalks vs. soybean plants vs. almond shells. Does the answer also depend on other factors, such as soil type and climate?

Many research papers on atmospheric carbon removal with biochar assume that crop residues will be a major source of pyrolysis fuel. If it’s environmentally better to leave the dead crops on the fields, then that would prevent a lot of organic waste from being turned into biochar. That, in turn, could lower the maximum amount of carbon that biochar could remove from the atmosphere annually.

From another perspective, is pyrolysis with cover cropping less cost-effective than leaving the crop waste on the field?

Thanks.

Kim


Paul S Anderson
 

Kim,

My response to your questions are in the following 2 paragraphs that I have written for a not-yet released white paper about biochar specifically as a negative emissions technology (NET). I expect to release the whole document before the National Biochar week in December, and only after having some qualified "peers" provide review comments. Volunteer reviewers should write to me privately at psanders@ilstu.edu .

^^^^^^^^^^^^^
After harvest, many fields have an overabundance of crop residue or refuse (including weed seeds and hard stems) that should be reduced or incorporated into the soil before the next planting season. Industrial societies have turned to mechanical agriculture for plowing, ,disking, chopping, bailing, etc. to have fields ready for the next planting season. In the less developed world that heavily depends on human or animal labor, when sufficient physical removal of residue from the fields is too troublesome, burning is a common “solution” that results in excessive removal, nutrient loss and serious air pollution.
A far better solution would be to pyrolyze an appropriate amount of that crop residue. Pyrolysis would put 50% of the carbon atoms of the processed residue into the soil while having cleaner combustion of the emissions, meaning less air pollution. ... for CDR objectives, some pyrolytic solution would result in the permanent sequestration of nearly 25% by weight of the carbon (not CO2) of the pyrolyzed biomass, or the CO2equivalent that would weigh about 45% of the original weight of the biomass.

^^^^^^^^^^^^^^^^^^
Basically, good agriculture should desire to leave SOME of the crop residue, and often truly needs to remove some residue. But as you wrote, different situations of soils, crops, economics, labor, etc. mean that there is not one simple response to cover all cases.

Paul

Doc / Dr TLUD / Paul S. Anderson, PhD --- Website: www.drtlud.com
Email: psanders@ilstu.edu Skype: paultlud
Phone: Office: 309-452-7072 Mobile & WhatsApp: 309-531-4434
Exec. Dir. of Juntos Energy Solutions NFP Go to: www.JuntosNFP.org
Inventor of RoCC kilns for biochar and energy: See www.woodgas.com
Author of “A Capitalist Carol” (free digital copies at www.capitalism21.org)
with pages 88 – 94 about solving the world crisis for clean cookstoves.

-----Original Message-----
From: main@Biochar.groups.io <main@Biochar.groups.io> On Behalf Of
Kim Chaffee via groups.io
Sent: Friday, November 6, 2020 6:55 PM
To: Biochar@groups.io
Subject: [Biochar] Leaving vs. pyrolyzing crop residues?

[This message came from an external source. If suspicious, report to
abuse@ilstu.edu<mailto:abuse@ilstu.edu>]

All,

Could anyone tell me whether it is generally better for the environment to
leave crop waste on the soil or to turn it into biochar? Let’s assume that, if
the crop residues were removed and pyrolyzer, the farmer would
immediately plant cover crops on the same acreage.

I assume that it might matter what type of crops we are considering: corn
stalks vs. soybean plants vs. almond shells. Does the answer also depend
on other factors, such as soil type and climate?

Many research papers on atmospheric carbon removal with biochar
assume that crop residues will be a major source of pyrolysis fuel. If it’s
environmentally better to leave the dead crops on the fields, then that
would prevent a lot of organic waste from being turned into biochar. That,
in turn, could lower the maximum amount of carbon that biochar could
remove from the atmosphere annually.

From another perspective, is pyrolysis with cover cropping less cost-
effective than leaving the crop waste on the field?

Thanks.

Kim





Rick Wilson
 

Kim,

What I know is that you do not want to move your residue around, because that can spread disease.

Related to your question, in a forestry scenario where you are turning thinnings to biochar, what do people do with that biochar (Kelpie)? What happens if you integrate it into the forest soil. Any studies?

Rick

On Nov 6, 2020, at 4:54 PM, Kim Chaffee <kim.chaffee2@gmail.com> wrote:

All,

Could anyone tell me whether it is generally better for the environment to leave crop waste on the soil or to turn it into biochar? Let’s assume that, if the crop residues were removed and pyrolyzer, the farmer would immediately plant cover crops on the same acreage.

I assume that it might matter what type of crops we are considering: corn stalks vs. soybean plants vs. almond shells. Does the answer also depend on other factors, such as soil type and climate?

Many research papers on atmospheric carbon removal with biochar assume that crop residues will be a major source of pyrolysis fuel. If it’s environmentally better to leave the dead crops on the fields, then that would prevent a lot of organic waste from being turned into biochar. That, in turn, could lower the maximum amount of carbon that biochar could remove from the atmosphere annually.

From another perspective, is pyrolysis with cover cropping less cost-effective than leaving the crop waste on the field?

Thanks.

Kim






Geoff Thomas
 

Kim, in northern Australia, much sugar cane is grown, - for decades the residue after harvesting has been cool burned.
Much research has shown that that soil is producing far more than it should, - sugarcane being a strong feeder.
But that sort of slow burning is a strong charcoal producer and fungicide.

Now almost universally the residue is ploughed into the soil, - just a few years so far, so it will be interesting to see the latest research? Anyone? - although much more artificial fertiliser is being used these days.. blurring the picture.

Cheers, Geoff Thomas.

On 7 Nov 2020, at 12:04 pm, Rick Wilson via groups.io <rick012=yahoo.com@groups.io> wrote:

Kim,

What I know is that you do not want to move your residue around, because that can spread disease.

Related to your question, in a forestry scenario where you are turning thinnings to biochar, what do people do with that biochar (Kelpie)? What happens if you integrate it into the forest soil. Any studies?

Rick




On Nov 6, 2020, at 4:54 PM, Kim Chaffee <kim.chaffee2@gmail.com> wrote:

All,

Could anyone tell me whether it is generally better for the environment to leave crop waste on the soil or to turn it into biochar? Let’s assume that, if the crop residues were removed and pyrolyzer, the farmer would immediately plant cover crops on the same acreage.

I assume that it might matter what type of crops we are considering: corn stalks vs. soybean plants vs. almond shells. Does the answer also depend on other factors, such as soil type and climate?

Many research papers on atmospheric carbon removal with biochar assume that crop residues will be a major source of pyrolysis fuel. If it’s environmentally better to leave the dead crops on the fields, then that would prevent a lot of organic waste from being turned into biochar. That, in turn, could lower the maximum amount of carbon that biochar could remove from the atmosphere annually.

From another perspective, is pyrolysis with cover cropping less cost-effective than leaving the crop waste on the field?

Thanks.

Kim










Tom Miles
 

As with most situations it is site, soil, and crop specific. Years of research and some major biofuel projects have shown that quantities of energy crops, like canes, miscanthus or switchgrass, can be removed while leaving sufficient residue for regeneration. For most field crops like straws and grasses you need to be able to remove 1.5 tons or more per acre to deliver the residue economically to an industrial use. There is often 3-5 tons available while leaving 1.5 tons as stubble. Leaving more may be required depending on the circumstances.

Our grass seed straw was open burned to control disease from about the time that my great uncle planted ryegrass for seed in 1938 until the late 1960s when air pollution became a serious concern. The stubble burners that our firm developed, which used the stubble as fuel to sanitize the field, were technically efficient but not economically feasible. Now most straw from our perennial grass seed fields is harvested and exported as roughage for animal feed. Air pollution from burning residues has been a driver behind the harvest of wheat straw and corn stover per year in China which is converted to biochar based fertilizers. They call it "straw returning" as described in a 2019 article in the Biochar Journal at bit.ly/2RqkZh8

Harvesting field residues from sugar cane started in the 1980s in Australia with the development of the Tilby method of mechanical harvesters. Before that, as Geoff described, most tops and leaves were burned in the field prior to harvest. Mechanical harvesting is now the preferred method in many areas. Some manual harvesting is maintained for social purposes. Most of the fibrous residue from sugar extraction is converted to energy, especially in India. "Green harvest" methods of harvesting the whole cane with tops and leaves in the field were not successful in Hawaii in the 1990s. Systems for separating the tops and leaves at the mill in the US have failed so far. Various projects are underway to convert field residues and excess fiber to energy and biochar.

Tom

-----Original Message-----
From: main@Biochar.groups.io <main@Biochar.groups.io> On Behalf Of Geoff Thomas
Sent: Friday, November 06, 2020 9:15 PM
To: main@Biochar.groups.io
Subject: Re: [Biochar] Leaving vs. pyrolyzing crop residues?

Kim, in northern Australia, much sugar cane is grown, - for decades the residue after harvesting has been cool burned.
Much research has shown that that soil is producing far more than it should, - sugarcane being a strong feeder.
But that sort of slow burning is a strong charcoal producer and fungicide.

Now almost universally the residue is ploughed into the soil, - just a few years so far, so it will be interesting to see the latest research? Anyone? - although much more artificial fertiliser is being used these days.. blurring the picture.

Cheers, Geoff Thomas.

On 7 Nov 2020, at 12:04 pm, Rick Wilson via groups.io <rick012=yahoo.com@groups.io> wrote:

Kim,

What I know is that you do not want to move your residue around, because that can spread disease.

Related to your question, in a forestry scenario where you are turning thinnings to biochar, what do people do with that biochar (Kelpie)? What happens if you integrate it into the forest soil. Any studies?

Rick




On Nov 6, 2020, at 4:54 PM, Kim Chaffee <kim.chaffee2@gmail.com> wrote:

All,

Could anyone tell me whether it is generally better for the environment to leave crop waste on the soil or to turn it into biochar? Let’s assume that, if the crop residues were removed and pyrolyzer, the farmer would immediately plant cover crops on the same acreage.

I assume that it might matter what type of crops we are considering: corn stalks vs. soybean plants vs. almond shells. Does the answer also depend on other factors, such as soil type and climate?

Many research papers on atmospheric carbon removal with biochar assume that crop residues will be a major source of pyrolysis fuel. If it’s environmentally better to leave the dead crops on the fields, then that would prevent a lot of organic waste from being turned into biochar. That, in turn, could lower the maximum amount of carbon that biochar could remove from the atmosphere annually.

From another perspective, is pyrolysis with cover cropping less cost-effective than leaving the crop waste on the field?

Thanks.

Kim