Garden Char Processing

I've added some photos to Flickr on how I currently prepare my charcoal for add ing to garden soil. This is in support of the Biochar for Gardeners FAQ.

I am lightly soaking (shallow soak, lots of turning to keep surfaces moist) my charcoal to precondition it for a crush-and-chop reduction and then screening. To soak, I add soluble mineral fertilizer and fish emulsion. Once in the soil, these will stimulate biologic conditioning and will help prevent stalled plant growth due to induced N deficiency, a concern with direct use of fresh char in the garden.

Also, regarding the mineral fertilizer, I have it in the back of my mind that adding ammonium sulphate (a common ingredient in off-the-shelf soluble fertilizer formulations) to the soak water will boost water penetration. I am thinking this might help because ammonium sulphate is used hold farm chemicals on waxy plant surfaces (like thistle), and because saltier water generally tends to penetrate further and faster into problem soils. I am encouraged to think that ammonium sulphate helps to overcome fresh charcoal's water repellency, even if only to a slight degree.

No Miracles

Charcoal cannot replace the need for adding mineral nutrients.

I am an unabashed charcoal enthusiast. Used properly, adding charcoal to soil improves biomass production and soil health. Sometimes dramatically when soil productivity is low. Certainly part of the effect is increased nitrogen use efficiency: less N lost to nitrification and leaching. Charcoal also tends to be associated with higher post harvest soil levels of P and K for reasons that are not entirely clear. Perhaps this effect also is due to increased efficiency.

Most TP enthusiasts, myself included, are convinced that the most mysterious effects from adding charcoal relate to soil biology, more than they relate to direct physical and chemical effects, although those realms play important roles also. And, in keeping with my previous post, it seems clear to me that increased energy efficiency is a critical bit here. Plants and microbes are growing more biomass with less effort for reasons that can't be entirely explained by traditional nutrient-based perspectives. Yes, the charcoal adds potassium, yes it raises soil pH, yes it increases soil water and nutrient holding capacity. But the results speak to more, much more.

The behavior of charcoal amended soil seems to defy the limits of the soil-biology system understood by traditional science. However, it would be entirely foolish to think that simple soil nutritional requirements are not still in play. Nutrient deficiencies limit living systems. Charcoal may promote efficiencies that help stretch the budget in regards to those limits, but in the end, the most limiting nutrient before adding charcoal is probably still going to be the most limiting nutrient after adding charcoal.

What got me thinking about this was consulting soil scientist Doug Edmeades’ posts on soil organic matter. The first, Carbon farming: take-off or rip-off, explored how carbon sequestration efforts can cut both ways. The second, Soil Organic Matter Matters, hits on the most-limiting-nutrient.

Pasture plants need 16 nutrients. Without all 16 the clover will disappear, the pasture will be N deficient, the quality grasses will fail, pasture production would collapse followed by a need to cut back the stocking rate and, given sufficient years, a farm would be back to native pastures and bush. In the process soil carbon levels would decline.

Collapsed pasture production is no idle threat. We know that the collapse of legumes in pasture systems in Europe and in the eastern US helped motivate the expansion of the western US. Against that historical backdrop, Benjamin Franklin famously demonstrated sulfur deficiency when he added gypsum to alfalfa to form the words "This has been plastered". Doug Edmeades mentions this because soil carbon sequestration enthusiasts seem to have temporarily lost track of these limits. The same caution applies to charcoal.

There is great potential for increasing productivity through judicious use of charcoal. However, TP enthusiasts must not lose sight of the fact that charcoal cannot replace the need for adding mineral nutrients.

New Gardening with Biochar FAQ

Note: Bio-char, agrichar, and charcoal are interchangeable terms when it comes to the intentional use of charcoal in the garden.

The argument for encouraging biochar use as a ubiquitous household practice is compelling: Improved garden soil will increase food production where it has the most impact on energy demand. Implementing charcoal manufacture at a household level draws in a supply of yard prunings and workbench scraps that otherwise would be lost to non-charcoal alternatives.

Unfortunately, finding even the most basic information on how to implement biochar use as a personal sustainability practice is discouragingly time consuming. In response I have started up a FAQ, a collaborative wiki, building on the efforts of the TP enthusiast community (1, 2, 3). Maybe you, the concerned gardening public, can help us thresh out the most important questions that need asking. Leave a comment here or at the FAQ. Here's my favorite bit from what has been posted so far:

2.05 What are some less smokey approaches to making charcoal for the gardener?

Choose your feedstock wisely. No matter what technique you use to make charcoal, choosing uniformly sized, dry woody material produces the highest yields. Uniformity is one reason that colliers will routinely use coppiced hardwoods.

Inverted Downdraft Gassification. For a cleaner burning configuration, consider a Top Lit Updraft (TLUD) technique, also referred to as an inverted downdraft gassification. The technique looks simple but in reality it involves some fairly sophisticated principles (PDF). That doesn't prevent success using common materials and dead simple design. Take that same open barrel configuration, tweak the design per the aforementioned sophisticated principles, and now light it from the top instead of the bottom. This takes a different skill set than lighting from the bottom but its also not that difficult to master. A little vaseline or ethanol on a cotton ball can work wonders for starting up. Once the fire gets going, the top layer of wood burns, creating charcoal, naturally. The heat from the top layer burning warms the wood below it releasing combustible and noncombustible gases which flow up into the charcoal layer. Glowingly hot charcoal has a wondrous ability to strip oxygen molecules from of anything that passes over it, so it converts the water into hydrogen, and the carbon dioxide into carbon monoxide. These two gases are flammable. They join with the other flammable gases released from the fuel. These ignite as they mix with air coming into the top of the open barrel above the charcoal layer. The result is a scrubbed gas-fed flame that is much more controlled, and which burns substantially cleaner and hotter than can be achieved with the bottom lit burn barrel. (Source). Insufficient oxygen below the combustion zone impedes loss of the charcoal despite the high temperature flame immediately above it. This allows charcoal to build up faster than it is consumed, at least until the pyrolysis zone reaches the bottom of the fuel column. The downside is that, while wondrously clean burning, a TLUD is challenged to achieve yields above 20% charcoal-to-fuel.

Folke Günther's simple TLUD-fired Retort. A retort works by restricting the air supply to the target feed stock for the duration of the burn. An outside heat source pyrolyzes the retort contents, small openings in the retort allow wood gas to escape, but restrict the flow of oxygen in. While retorts are capable of very high yield efficiency, the open flame used to fire the retort is not as clean as can be achieved with a gasifier. In small retorts, a further inefficiency is that wood gas generated from the retort can end up blowing by the combustion zone without being burned. Folke Günther's elegant solution is to combine a TLUD with a retort. This is easily the cleanest burning and highest yielding method we know of to make garden-sized batches of charcoal.

(Source)

The Charcoal Vision

I want to shout this from the rooftops.

A Win–Win–Win Scenario for Simultaneously Producing Bioenergy, Permanently Sequestering Carbon, while Improving Soil and Water Quality by David A. Laird, USDA-ARS, National Soil Tilth Laboratory

Processing biomass through a distributed network of fast pyrolyzers may be a sustainable platform for producing energy from biomass. Fast pyrolyzers thermally transform biomass into bio-oil, syngas, and charcoal. The syngas could provide the energy needs of the pyrolyzer. Bio-oil is an energy raw material (~17 MJ kg–1) that can be burned to generate heat or shipped to a refinery for processing into transportation fuels. Charcoal could also be used to generate energy; however, application of the charcoal co-product to soils may be key to sustainability. Application of charcoal to soils is hypothesized to increase bioavailable water, build soil organic matter, enhance nutrient cycling, lower bulk density, act as a liming agent, and reduce leaching of pesticides and nutrients to surface and ground water. The half-life of C in soil charcoal is in excess of 1000 yr. Hence, soil-applied charcoal will make both a lasting contribution to soil quality and C in the charcoal will be removed from the atmosphere and sequestered for millennia. Assuming the United States can annually produce 1.1 x 109 Mg of biomass from harvestable forest and crop lands, national implementation of The Charcoal Vision would generate enough bio-oil to displace 1.91 billion barrels of fossil fuel oil per year or about 25% of the current U.S. annual oil consumption. The combined C credit for fossil fuel displacement and permanent sequestration, 363 Tg per year, is 10% of the average annual U.S. emissions of CO2–C.

Washington State Biochar Research

Washington State University researchers will produce biochar (a residue potentially used as a soil amendment) from low temperature pyrolysis of biomass materials. The biochar will be tested for its potential to store carbon, evaluated for any growth effects on plants in the greenhouse, and assessed for economic impacts. Research on biochar has shown promise in long-lasting carbon storage and improved crop production. This research will be the first rigorous study of biochar use in agricultural soils in this state. (Source)

Agrichar trials in NSW

News and commentary on agrichar is flowing steadily this spring, first with the reporting on the 1st annual Agrichar Conference, and now with the reporting on initial agrichar trials by the New South Wales Department of Primary Industries (NSW DPI). Particularly encouraging is that the sophistication of the comments continues on the increase.

Snippets from ABC' Discovery channel ...

Recent greenhouse trials found soils mixed with the charred waste, called agrichar or biochar, were more attractive to worms and helpful microbes.

Agrichars trialled by NSW DPI include those from poultry litter, cattle feedlot waste as well as municipal green waste and paper mill sludge. Each agrichar has its own characteristics and interacts differently with different soil types.

Some agrichars raise soil pH at about one-third the rate of lime, raise calcium and reduce aluminium toxicity.

Kimber said more research needs to be done on working out which agrichars are best for which soils and on the impact of any contamination in biomass.

... reinforce the need for local pyrolysis pilot projects. The pyrolysis pilot hurdle is necessary where widespread agrichar use is the goal. Clean air concerns combines with the limited supply of local expertise and experience needed to achieve the low-temperature pyrolysis ideal for producing agrichar.

I have submitted comments emphasizing the need for pilot agrichar projects to our State's climate change folks.

(AP image source)

Agrichar: In the news May 15th

Two short articles well worth the read for terra preta enthusiasts:

Carbon project raises hopes: Waikato Times, NZ:

...Structural biologist Alfred Harris, process engineer Wolfgang Weinzetll and two Tauranga entrepreneurs are involved in Ecotechnology Ltd, which is working to reduce fertiliser use without hampering plant growth. The company is investigating producing a charcoal product from forestry and other organic waste which collects unwanted nutrients...

Recent work by Australian researchers showed wheat gained an additional $A96 per hectare in value when charcoal was banded in the soil with mineral fertilisers.

Is banded C the killerapp for agrichar? I don't know what the charcoal application rate was, but last I knew, banding equipment had limited material application capacity, charcoal is low density, and there was mineral fertilizer in the hopper also. A charcoal application rate in the neighborhood of about 100 lbs per acre seems reasonable to expect. At $100/ton for charcoal, material cost would be $5/acre ($A15/hectare). Is the value in comparison to a no-C comparison? I would surely like to see the research.

Seeder image source: Flickr by IRRI Images

Another May 15 article

Special Report: Inspired by Ancient Amazonians, a Plan to Convert Trash into Environmental Treasure (by Scientific American) has a great soil point-counterpoint under the heading: But is it viable? :

As with all new technologies, many questions about the ultimate utility of agrichar have yet to be answered. "As of now agrichar is not a uniform product," explains John Kimble, a retired USDA soil scientist. "And there's no easy way for farmers to apply it with existing equipment. They also need to know there is a large enough source of the material. Farmers are driven by profit, as is everyone, and they need to be shown that it will improve their bottom line."

Complicating debates about the costs of agrichar is the paucity of data on the subject. "No one is sure what types of biomass should be used as raw material," Kimble notes, "or exactly what production methods work best, so calculating the costs is really an exercise in speculation."

In addition, scientists are finding it hard to replicate the original terra preta soils. "The secret of the terra preta is not only applying charcoal and chicken manure—there must be something else," says Bruno Glaser, a soil scientist at Bayreuth University in Germany. Field trials in Amazonia using charcoal with compost or chicken manure find that crop yields decline after the third or fourth harvest. "If you use terra preta you have sustaining yields more or less constantly year after year," he says.

"I'm skeptical about adding just a pure carbon source," says Stanley Buol, a professor emeritus from the Department of Soil Science at North Carolina State University's College of Agriculture and Life Sciences who spent 35 years studying Amazonian soils. "It will be black and look good," but will it contain enough inorganic ions, such as phosphorus and nitrogen, essential to plant growth?"

Many of the interactions between the char, the soil and the microorganisms that develop with time and lend the soil its richness and stability are still poorly understood. Glaser believes that the key to making agrichar behave like terra preta lies in the biological behavior of the original Amazonian dark earths—a difference he attributes to their age. "You would need 50 or 100 years to get a similar combination between the stable charcoal and the ingredients," he cautions.

"I think [research into the biological behavior of terra preta] is where the new frontier will be," Lehmann counters. If he is right, and scientists can perfect a modern-day recipe for agrichar, then its fans will not need Richard Branson's $25 million to jump-start their initiative—the annual demand for fertilizers exceeds 150 million tons worldwide.

There are strong indications that soils amended with high (multiple tons/acre) rates of biochar need considerable time to reach their optimum. For setting where return on investment cycles need to be short, lower rates sustained for long periods of time may make more sense as a strategy for building soil C.

Agrichar future

In a post earlier today: Mental Rut, Back40 takes Johannes Lehmann, soil scientist, and terra preta front man, to serious task for cheer leading the politically attractive aspects of TP:

Agrichar should not be crufted up with political baggage or tainted by association with the various climate hysteria inspired carbon wheezes. That it sequesters carbon in a more durable form than forests or other organic forms is a plus, but not its primary value. It is just one of the multiple benefits of agrichar. That fact should not be lost in a blaze of hype. It's the wrong message.

Back40's comments make good sense. Consider that terra preta has serious political problems in the offing. Charcoal production as a tool to combat global warming can be understandably counterintuitive. Char's mode of action in the soil is only partly understood, the degree of benefit to the soil is not well documented. Claimed char additions may be difficult to monitor.

Various blog and forum posts ask: Does the fuel value of charcoal provide a dangerous incentive to divert agrichar to fuel use? To overharvest biomass? Can the reality of terra preta nova be separated from marketing pitches by commercial pyrolysis interests?

In this environment, poor marketing choices will hurt the prospects of terra preta. We terra preta advocates need to distinguish our advocacy for improved soil from our advocacy of commercial pyrolysis and of char carbon sequestration. The value of char as a soil amendment can, and must, stand on its own merits. Only successful implementation of terra preta nova in stand alone and market driven settings can validate the fundamental benefits of biochar.

The agricultural value of charcoal is competing well with its fuel value at a market price of about $100/ton. Agrichar doesn't appear to need carbon sequestration subsidies, and at $4 a metric ton CO2, maybe it isn't even worth the paperwork.

Charcoal is fairly simple, and generally profitable to produce. The pyrolysis process used to produce char is adaptable and scalable. It can be used to co-generate heat, nitrogen fertilizer, hydrogen fuel and/or electrical power, indicating ample incentives to increase charcoal supply capacity. Rising fuel prices seem certain to increase the supply of charcoal.

The price of charcoal is driven mostly by its value as fuel. Coke, originally derived from coal to replace charcoal, cost about $100/ton in late 2006, which seems to also be about the same price as charcoal at the time. Significant quantities of charcoal are used in Japan for agriculture at these market prices.

Proponents of terra preta hope to speed adoption by subsidizing it with carbon credits. Currently CO2 sequestering goes for about $4 per metric ton on the carbon credit market. Carbon dioxide units at full molecular weight can be converted into carbon units by dividing by 44/12 (see endnotes here). Thus the carbon credit value of amending soil with charcoal is currently $14.67 per metric ton, or $13.31 per ton. This could be a nice kicker but the soil amendment value of charcoal, at $100/ton, is the significant component.

Note: Image from Flickr by carlosjwj (Location: Korogocho, Nairobe)

Simpler Way To Counter Global Warming Explained: Lock Up Carbon In Soil

The techniques of ancient American Indians who used charcoal in their soil to keep them fertile (Terra preta) are being married with modern engineering. More here:
http://forums.hypography.com/terra-preta.html http://terrapreta.bioenergylists.org/



read more | digg story

Added: I came across this story on digg and noticed the blog-it tab...

Agri Char Conference Reviews

Agri-char aka bio-char is the key ingredient in soil scientists' holy grail, terra preta nova (my previous mention). Initial reports from participants at the first meeting of the International Agrichar Initiative indicate continued hope that agrichar amended soils could contribute significantly to our planet's health and productivity.

Kelpie Wilson, Truthout's environment editor, writes:

Charcoal's pores also make excellent habitat for a variety of soil microorganisms and fungi. Think of a coral reef that provides structure and habitat for a bewildering variety of marine species. Charcoal is like a reef on a micro-scale.

Over at the Sydney Peak Oil forum, attendee burko writes:

It would be very easy to become enthusiastic about the future of these integrated technologies. However, there is one overriding impression of this field to keep in mind – it is brand, spanking new. So new that even the choice of name Agrichar is being debated. There are no books; there are few years of experience even amongst the researchers; the debates about the benefits to AGW are only just beginning.

In short, being a part of the conference could be compared to hearing an orchestra tuning up. There are skillful cellists and masterful tuba players preparing next to each other. The idea is potential for beautiful music, rather than cacophony. We aren't really sure who the conductor is yet – plenty of skillful people are taking part of that role. There is cooperation and the desire to share experience at all points – but this is a new kind of orchestra.

While the soil biology alone is a staggering subject, we should be as interested in the methods of producing the black carbon. Burko writes on pyrolysis:

The gas produced is referred to as syn gas, called producer gas sometimes.

My formative understanding of the process says something like this – if you want to produce non-activated chars, temperatures need to be constrained below the levels that gasification requires in order to make the reaction sufficiently exothermic to be self sustaining.

Of course, there is more to it than that – I did find that combustion engineers found it difficult to provide a simpler explanation.

I did get one useful figure from Dr Robert Brown, from Iowa State University – if you're burning wood in an open fire, you're probably only getting a third of the heat energy that should be possible from gasification – a pretty compelling reason to try and understand this stuff. It's been said that up to a third of the worlds deforestation happens in the name of inefficient cooking fires.

From the reports, it is clear that the number of players, and their diversity, is growing exponentially. One reason for this diversity is that the process of making terra preta nova appears to be as adaptable to a wide range of soils and climates as it is scalable. You can have regional collection and distribution approaches coexisting with processes adapted to individual enterprises. The plan at Fourth Corner Nurseries (mentioned previously) near Bellingham, WA is a great example of both points. The operation already amends the soil with char. Observed better root growth confirms what we already sense, that black carbon can have a positive effect on a wide range of soils. The nursery plan to use surplus biomass from their willow coppice field to power the nursery and to produce char is easier said than done, but is brimming with promise.

Image: Scanning electron micrograph of a conductive carbon sticky tab. (Flickr - St Stev)

Charcoal amended soil for real

Richard Haard, Fourth Corner Nurseries, near Bellingham WA is using charcoal as a soil additive, apparently for at least the 2006 growing season. From the way he describes it, this bare-root nursery operation seems like one of the better places to see if and how much of a difference charcoal can make. He has lots of pictures of the process, including some observed positive effects on root growth. He is using charcoal as a carrier for inoculate as a matter of routine and has several future experiments under consideration:

• Rehabilitation of depleted soil: Bare-root production at the nursery is very hard on the soil and impact varies with the species grown, as revealed by differences in subsequent cover crop vigor. Using charcoal treatment plots and comparable control plots would be interesting.
• Improving nodule formation on Alnus rubra roots: Using charcoal to enhance performance of Frankia sp., an Alnus root nodule endophyte.
• Natural inoculation of bromide sterilized soil: Using a combination of charcoal, fertilizer and natural inoculum in an attempt to reverse stunting apparently due to soil sterilization.

As an aside, he mentions that the "use of surplus biomass from our willow coppice field and other materials is our alternative energy vision."

Yes.



Technorati tags: bio-char, terra preta

More on pyrolysis

James, over at The Good Life (Ireland) has been trying out a MIDGE aka modified inverted downdraft gasifier experiment. (MIDGE plans pdf). That is pretty much the direction I have been thinking of heading on my quest for balanced charcoal making. James has a valuable reference to a a book I am definitely going to get: How to Convert Wood into Charcoal & Electricity, by Richard Burton.


Technorati tag: bio-char

Pyrolysis

Step 3: Pyrolysis
Originally uploaded by paleorthid.

Charcoal holds a key to improved soil vitality. Reported effects are impressive. Level of response varies with the temperature the charcoal is produced at. Low temperature charcoal is better. The soil improvement process that charcoal initiates is poorly understood. I want to see this at work for myself.

Briquets are no good for my experimental use. They are made with a high-boron binder, and the temperatures that are used to produce them leave few wood gas condensates. At some point I'll find a supply or locate a collier. In the meantime I'm making my own, just to see what it takes.

I made a few small batches of low-temp charcoal with a retort fashioned from a cracker tin. It produced impressive volumes of smoke, so I got on a track of finding out how that smoke might be put to good use.

Thomas B. Reed, Biomass Energy Foundation president and CREST gasification list moderator, has been working on a better understanding of inverted downdraft gasification. He is passionate about improving the efficiency of cook stove fuel use in third world countries. Thus his perennial effort to perfect a household-size inverted downdraft gasifier. Of interest to soil scientists, some of his designs have the capacity to produce charcoal.

Tom Reed designs have inspired others. In 2003 Ray Garlington produced a simplified design. I modified Ray's design to be able to shut it down and hold the charcoal. I used it to boil a cup of water with only a small handful of cedar. It was 2 deg F outside but not a problem. I even produced a fair bit of charcoal. Photos of my run are posted on Flickr.

Update: Concise description of the process: "The wood is placed into the stove and ignited from the top. The top layer of wood burns, creating charcoal. The heat from the charcoal layer burning heats the wood below it, and ignites it. The gases (carbon dioxide and water) flow through the charcoal layer. Glowing hot carbon has a unique ability to strip oxygen molecules off of anything that it touches, so it converts the water into hydrogen, and the carbon dioxide into carbon monoxide. These two gases are flammable and they are ignited once mixed with air above the charcoal layer. The result is a flame that is much more controlled, and cleaner than that of raw wood burning." (Source)

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