biochar 101
May 12, 2018 5:34 PM Subscribe
In simple terms, what's biochar all about? How does it work? Is it actually good for the environment? Should I make it or should I just compost the yard waste?
I grew up with "slash and burn is bad." Fire is air pollution, air pollution is bad, right? Then I got to the place I'm currently WWOOFing, and they say the previous WWOOFer was doing biochar.
I have gotten as far as figuring out that biochar is different than charcoal in that it can be made of any biomatter. Ok. Some sources online say it's a carbon sink, some say it's an oxygen sink. Is it just that it gives microbes a structure to fix NPK and that's so good it cancels out the air pollution somehow?
(This is in a semi-rural area where neighbors aren't close enough to mind a fire.)
I'm looking for people who already have an understanding of what's up with biochar or enough of a background in climate change/soil science/etc. to answer this question, please.
I grew up with "slash and burn is bad." Fire is air pollution, air pollution is bad, right? Then I got to the place I'm currently WWOOFing, and they say the previous WWOOFer was doing biochar.
I have gotten as far as figuring out that biochar is different than charcoal in that it can be made of any biomatter. Ok. Some sources online say it's a carbon sink, some say it's an oxygen sink. Is it just that it gives microbes a structure to fix NPK and that's so good it cancels out the air pollution somehow?
(This is in a semi-rural area where neighbors aren't close enough to mind a fire.)
I'm looking for people who already have an understanding of what's up with biochar or enough of a background in climate change/soil science/etc. to answer this question, please.
Here's the basic concept behind biochar. You dig up coal which has sequestered carbon away from the atmosphere for million of years, burn it and add carbon dioxide to the atmosphere.
Then plants absorb that CO2 from the atmosphere, you convert the plants to biochar, and bury it. So essentially you are putting coal back into the ground from where it came. That's the basic claim of biochar.
Sounds simple, but biochar claims may be running ahead of the science. It only works if the biochar really does remain in the soil for long periods of time as if it were buried coal. There isn't a lot of data to indicate that the biochar really does remain stable in the soil. It depends on the ecology of the soil environment. In some cases the biochar is broken down by microorganisms and returns to the atmosphere as CO2. So nothing is gained.
posted by JackFlash at 7:08 PM on May 12, 2018
Then plants absorb that CO2 from the atmosphere, you convert the plants to biochar, and bury it. So essentially you are putting coal back into the ground from where it came. That's the basic claim of biochar.
Sounds simple, but biochar claims may be running ahead of the science. It only works if the biochar really does remain in the soil for long periods of time as if it were buried coal. There isn't a lot of data to indicate that the biochar really does remain stable in the soil. It depends on the ecology of the soil environment. In some cases the biochar is broken down by microorganisms and returns to the atmosphere as CO2. So nothing is gained.
posted by JackFlash at 7:08 PM on May 12, 2018
Just adding another way of describing biochar here, in case it complements SaltySalticid’s explanation. (No offense, JackFlash, but it seems to me that you’re glossing over some key details and in doing so misrepresenting a bit).
There are a few reasons that biochar advocates recommend making it. One is that in cases where significant amounts of biomass are being landfilled or left to compost (think plant wastes from food processing - husks, shells, cobs, pits - and or food wastes in cities, which typically go to landfills), burning that material to create carbon-stable biochar sequesters carbon that would otherwise more rapidly enter the atmosphere (as SaltySalticid explains above).
Another is that when mixed with compost, biochar can significantly enrich soils and increase soil water retention, thereby improving plant growth. There’s a measurable growth boost in fertile souls, but the improvement is particularly significant in places where soil conditions are bad (so biochar is sometimes used, for example, in agricultural practices where soils are nutrient-poor, or recently to reduce compaction and thereby improve street tree health in a successful biochar project in Stockholm).
The upshot is that converting plant and food waste to biochar is win-win: you take what would become atmospheric carbon through decomposition and instead sequester it for a long time, and you also get a useful material for improving soils, retaining and filtering groundwater, etc.
If you’re looking into making biochar on a small scale, you need to make sure that you’re burning your biomass correctly (I don’t know all the details offhand, but I do know the burn temperature needs to be within a certain range that is somewhat low). There are small kilns out there made for this, and I’m sure there must be some make-your-own-kiln approaches as well. Also, if you want to use biochar to amend soil, it is essential that you mix it with compost first - alone in soil it will likely do more harm than good (but again, I don’t know all the details here).
(Re: where this info comes from: I’m a landscape architect/scholar who recently taught a graduate studio on urban strategies for carbon sequestration, and biochar was one of the methods we studied/proposed. We were working with Finger Lakes Biochar, an organization working to promote biochar use in central New York State. Like SaltySalticid, I could point you to papers if you like, though I’d recommend looking into online biochar discussions first: there’s a well-networked and communicative set of people discussing research and application worldwide.)
posted by marlys at 8:12 PM on May 12, 2018 [2 favorites]
There are a few reasons that biochar advocates recommend making it. One is that in cases where significant amounts of biomass are being landfilled or left to compost (think plant wastes from food processing - husks, shells, cobs, pits - and or food wastes in cities, which typically go to landfills), burning that material to create carbon-stable biochar sequesters carbon that would otherwise more rapidly enter the atmosphere (as SaltySalticid explains above).
Another is that when mixed with compost, biochar can significantly enrich soils and increase soil water retention, thereby improving plant growth. There’s a measurable growth boost in fertile souls, but the improvement is particularly significant in places where soil conditions are bad (so biochar is sometimes used, for example, in agricultural practices where soils are nutrient-poor, or recently to reduce compaction and thereby improve street tree health in a successful biochar project in Stockholm).
The upshot is that converting plant and food waste to biochar is win-win: you take what would become atmospheric carbon through decomposition and instead sequester it for a long time, and you also get a useful material for improving soils, retaining and filtering groundwater, etc.
If you’re looking into making biochar on a small scale, you need to make sure that you’re burning your biomass correctly (I don’t know all the details offhand, but I do know the burn temperature needs to be within a certain range that is somewhat low). There are small kilns out there made for this, and I’m sure there must be some make-your-own-kiln approaches as well. Also, if you want to use biochar to amend soil, it is essential that you mix it with compost first - alone in soil it will likely do more harm than good (but again, I don’t know all the details here).
(Re: where this info comes from: I’m a landscape architect/scholar who recently taught a graduate studio on urban strategies for carbon sequestration, and biochar was one of the methods we studied/proposed. We were working with Finger Lakes Biochar, an organization working to promote biochar use in central New York State. Like SaltySalticid, I could point you to papers if you like, though I’d recommend looking into online biochar discussions first: there’s a well-networked and communicative set of people discussing research and application worldwide.)
posted by marlys at 8:12 PM on May 12, 2018 [2 favorites]
Just compost the yard waste, unless you have a lot of wood in your waste stream. The process of making char (which *is* just charcoal) means that you will denature a lot of organic material and simply burn it off, creating carbon dioxide out of a higher percentage of the input feedstock than you would if you were to simply compost it.
If you compost it, a lot of that organic material that charring would convert to CO2 would instead be will be converted into the chitin and hemolymph of arthropods and fungus, and into the flesh and blood of the creatures that eat them, and so on into a wriggling, breathing pyramid of life deriving its energy from your composting.
*If* you have a lot of wood in your waste stream (3/4 inch sticks and bigger), and *if* you have heavy, dense, or degraded soils that you are trying to upgrade or recover, then you might consider making biochar out of the woody waste. Simply make charcoal as efficiently as possible (where part of the energy of burning some of the woody waste converts the rest of it into charcoal). Making charcoal is an old, old process, and you should be able to do it with a decidedly primitive setup.
Biochar behaves primarily as an inert, lightweight, nontoxic soil amendment. It does not biodegrade easily, and can improve drainage.
One other advantage of treating your woody waste like this is the problem that wood and lignin present to the composter: these materials have to be physically processed, like fine chipping, so they can be biodegraded, and they will consume an enormous amount of nitrogen nutrients as biology converts them into usable carbon.
I suggest that you steer clear of technologies that involve gasification for the creation of biochar. Gasification is the process of using basically woody waste and using it to generate fuel gas (carbon monoxide and hydrogen) for energy production, as the fuel is readily consumable by internal combustion engines. The side effect of gasification is purported the creation of biochar, with all of its benefits, but I allege that it is primarily greenwashing. Mentions of gasification and biochar mentions are highly correlated, and there is usually something to buy that makes a lot of fuel gas and not much biochar.
posted by the Real Dan at 11:07 AM on May 13, 2018
If you compost it, a lot of that organic material that charring would convert to CO2 would instead be will be converted into the chitin and hemolymph of arthropods and fungus, and into the flesh and blood of the creatures that eat them, and so on into a wriggling, breathing pyramid of life deriving its energy from your composting.
*If* you have a lot of wood in your waste stream (3/4 inch sticks and bigger), and *if* you have heavy, dense, or degraded soils that you are trying to upgrade or recover, then you might consider making biochar out of the woody waste. Simply make charcoal as efficiently as possible (where part of the energy of burning some of the woody waste converts the rest of it into charcoal). Making charcoal is an old, old process, and you should be able to do it with a decidedly primitive setup.
Biochar behaves primarily as an inert, lightweight, nontoxic soil amendment. It does not biodegrade easily, and can improve drainage.
One other advantage of treating your woody waste like this is the problem that wood and lignin present to the composter: these materials have to be physically processed, like fine chipping, so they can be biodegraded, and they will consume an enormous amount of nitrogen nutrients as biology converts them into usable carbon.
I suggest that you steer clear of technologies that involve gasification for the creation of biochar. Gasification is the process of using basically woody waste and using it to generate fuel gas (carbon monoxide and hydrogen) for energy production, as the fuel is readily consumable by internal combustion engines. The side effect of gasification is purported the creation of biochar, with all of its benefits, but I allege that it is primarily greenwashing. Mentions of gasification and biochar mentions are highly correlated, and there is usually something to buy that makes a lot of fuel gas and not much biochar.
posted by the Real Dan at 11:07 AM on May 13, 2018
On a small scale, I suspect computing makes the most sense. I used some with fencing that was free. Just a wide cylinder that I filled with food waste and yard waste. I don't turn it or worry about brown or green. That compost enriched an area of dead soil that is now growing flowers. My neighbors gave away their big plastic composter, so I am using that, though it's big and plastic and ugly, so I may pass it along.
You may find the time is better spent being active in your community. Road design affects carbon use, water is is an issue; there are many ways to come at the problem. Good question- I hadn't been aware of this.
posted by theora55 at 5:26 AM on May 14, 2018 [1 favorite]
You may find the time is better spent being active in your community. Road design affects carbon use, water is is an issue; there are many ways to come at the problem. Good question- I hadn't been aware of this.
posted by theora55 at 5:26 AM on May 14, 2018 [1 favorite]
Typing on my phone, sigh. Computing should be composting. with fencing should be wire fencing.
posted by theora55 at 5:46 AM on May 14, 2018
posted by theora55 at 5:46 AM on May 14, 2018
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All carbon cycles, it’s just a matter of if the pools are faster or slower at turning over. This is how you can grow miscanthus grass, burn the dead tops for fuel, and have a net carbon sink into the soil*
*off topic but happy to explain that if you want.
TLDR: carbon in leaf mould goes back to the atmosphere in a few years. Carbon in char can take take thousands. When you account for fluxes up and down, biochar is a good sink on the hundred year horizon, whereas normal compact can vary from minimal sink to minimal source on that time frame, depending on how it’s made and how it’s used.
(I am a plant ecologist who has worked adjacent to the hard core carbon accounting crowd. I can supply scholarly refs if interested, but this is my understanding after rubbing elbows with serious pros for several years.)
posted by SaltySalticid at 5:52 PM on May 12, 2018 [5 favorites]