Charcoal Stability and Storage in Soils

Charcoal has been found in soils and radio carbon dated to tens of thousands of years old, it does break down bio-chemically*.  The rate of decomposition is based on the time, texture, depth, temperature, moisture, reactivity, and total organic carbon (Frink1999).  The rate is measured in thousands of years for typical farm applications and will have a minimal impact on calculating sequestration rates.  However, this work will need to be done. Here are links to various research areas.


  1. Effects of wood carbonization on soil and initial development of seedlings in miombo woodland

  2. The nature of unextractable organic matter fractions in allophanic andosols

  3. What the Kansai Electric Group Doing

  4. Soil Carbon Sequestration by Holocene Fires Inferred from Soil Charcoal in the Dry French Alps


  6. Black Carbon in Soils Looking for the missing carbon


  8. *Selections from: The OCR Carbon Dating Procedure and Its Application at the Rmiz Site, Czech Republic





Chidumayo E N (1994) Effects of wood carbonization on soil and initial development of seedlings in miombo woodland, Zambia. Forest Ecology & Management. 1994. 70(1/3): 353-357.

On charcoal spots - the site of charcoal production using the traditional earth kiln method - in miombo woodland in central Zambia, tree regeneration (both of indigenous species such as Brachystegia manga and Julbernardia globiflora, and exotic species such as Gmelina sp. and Eucalyptus sp.) is much slower and less successful than on areas outside the spots. An assessment was made of the effects of charcoal production on soil nutrients in the field and seedling growth (of seven indigenous woody plants) under laboratory conditions, from August 1992 to March 1993, in the Chitemalesa area. Charcoal was gathered from three kiln sites in June (at one site) and November 1992, and local people intercropped maize [Zea mays] and pumpkin [Cucurbita sp.] on all spots during the 1992-93 rainy season (December-March). Soil samples were collected (0-10 cm and 11-30 cm depths) from within and without the charcoal spots. Charcoal production increased soil pH and exchangeable P and K. Generally seed germination was better in soil with charcoal than in undisturbed soil among the seven indigenous woody plants studied (Acacia polyacantha, Bauhinia petersiana, Isoberlinia angolensis, Pterocarpus angolensis, Swartzia madagascariensis, Tamarindus indica and Ziziphus mauritiana). Seedling growth in charcoal soil was good, except for I. angolensis which had a lower growth rate than in undisturbed soil.

http://www.soton.ac.uk/~icuc/tambib/tam-pps2.htm      TOP

2. The nature of unextractable organic matter fractions in allophanic andosols

Up to 50% of the organic matter in most soils is unextractable by standard methods. This unextractable matter contains undecomposed plant remains, remnants of apolar aliphatic polymers, charcoal, and strongly mineral-bound matter. In the light of global carbon dynamics, the very strongly bound fraction, which is very stable over time, is extremely important. This project aims to characterize this fraction. It is isolated through various extraction procedures. Characterization is by pyrolysis-GC/MS or equivalent methods.

by mutual agreement. Samples are available
Preferably J050-202 and J050-237; interest in laboratory work.
21-27 credits
P. Buurman, B. van Lagen, E.J. Velthorst, P. van Bergen

http://www.dow.wageningen-ur.nl/ssg/educat/tsr1-6.htm      TOP

3.What the Kansai Electric Group Doing (PDF)  - ... using charcoal as medium to improve the soil and to purify water. ?? Outline of business feasibility study in Indonesia Project name Site Contents Duration ...
http://www.kepco.co.jp/e/action_e/pdf2001e/P75-78.pdf       TOP
4. Soil Carbon Sequestration by Holocene Fires Inferred from Soil Charcoal in the Dry French Alps (pp 282-288)
Christopher Carcaillet and Brigitte Talon

The current global carbon budget has a missing sink, which is believed to be in terrestrial ecosystems. At least one carbon sink, wood charcoal sequestrated in soil, remains poorly detailed. We estimate the wood charcoal-carbon content in soils located in dry valleys within the French Alps. Soils were sampled at five sites along altitudinal transects, from the conifer-dominated subalpine forests to the alpine grasslands. The five sites were distributed along a bioclimatic and biogeographic gradient from the southern Mediterranean to the northern continental Alps. The altitudinal distribution of charcoal exhibits the same pattern in the five sites, despite stand fire history, and regional bioclimatic and biogeographic differences. Charcoal concentrations are low (0.01 to 10 gchar m-2) in soils from the current treeless belt, while soils at lower elevation show high concentrations (10 to 2000 gchar m-2). The results suggest that the landscape structure determine the charcoal accumulation throughout variability of vegetation type and fire frequency. Charcoal concentrations recorded in the subalpine belt in the Alps are similar to those of Swedish boreal forests, but are 10 to 100 times lower than values from Mediterranean ecosystems. Dry to subhumid ecosystems contain subfossil carbon in the form of charcoal, which should be explicitly taken into account in the global carbon budget.

http://www.colorado.edu/INSTAAR/arcticalpine/volume33/33-3abs.html     TOP

5. Originally published in Archaeology of Eastern North America 20:67-79 (1992)

ęCopyright 1992 Eastern States Archaeological Federation



Douglas S. Frink

Archaeology Consulting Team, Inc.

Essex Junction, Vermont.


The interdependent dynamics of climate, biota, relief, parent material and time

affect the evolution of both soils and archaeological remains within the soil. Carbon-ized

organic matter, charcoal, is one class of archaeological material subject to these

environmental factors. Although charcoal is generally presumed to be immune to

environmental influences, chemical analyses of feature soils containing charcoal from

archaeological sites throughout New England demonstrate its susceptibility to the

effects of environmental factors. Calculation of a formula of the interdependent dynamics

of these environmental factors provides some understanding of the specific

influences of each factor. This formula, when expressed in terms of the factor time,

provides an independent, inexpensive and accurate means to determine the age of

archaeological charcoal. The low cost and ease of this procedure is well-suited to environmental,

geological and archaeological disciplines. Since this is a chemical procedure,

relatively young charcoal can be dated without the problems found in radiocarbon

dating of young charcoal.


The interdependent dynamics of climate, biota, relief, parent material and time

are generally recognized as the prime causes for the development of soils (Jenny 1941).

As soil constitutes the contextual matrix of most archaeological deposits, these five

factors are likely to have an influence on certain classes of archaeological deposits. One

such class, carbonized organic matter or charcoal, is affected by these five soil formation

factors in ways that have implications for archaeological research. Organic matter,

whether used for food, clothing, structures, tools or fuel, constitutes the largest class of

cultural remains. However, this particular class of artifacts is extremely susceptible to

biochemical alterations in its form, (i.e., decay), and dispersement of its parts due to

natural recycling and leaching of elements. The net result is that little surviving evidence

of this class of cultural material is found in an archaeological context (Schiffer


One form of organic matter which does survive in archaeological context is

carbonized organic matter resulting from human activities (i.e., cooking hearths) or

natural events (e.g., environmental fires)(Schiffer 1987). Carbonized organic matter,

often referred to as charcoal, consists mainly of elemental carbon and inorganic com-pounds,

and is generally thought to be immune to biochemical decay and natural

recycling (e.g., Dowman 1970).......(click link for more)

http://members.aol.com/dsfrink/ocr/downloads/chemicalvariability.pdf    TOP


Black Carbon in Soils
Looking for the missing carbon

(Press release dfd 6/2000) Burning fossil fuels releases large amounts of carbon dioxide into the atmosphere. However, researchers have found less of this greenhouse gas in the air than they ought to have according to their global carbon dioxide balance. Around half of the amount is missing. Scientists of Cologne University have been looking for this depression.

"The missing link here has long been suspected in the oceans. But we now believe that the missing carbon could occur in terrestrial ecosystems, especially in soils," Dr. Michael Schmidt explains. Around 20 percent of the depression probably occurs owing to regular forest fires. The trees are not completely combustible but are charred. Largely, charcoal is left. Also, there are considerable amounts of soot that eventually rains down on the earth again. Charcoal and soot are simple terms for complicated organic molecules. They consist of graphite-like layers the arrangement of which always differs according to how they are formed. Scientists refer to them with the generic term of black carbon.

This organic material accounts for up to half of the composition of soils. It is extremely resistant to chemicals. "So far, examinations have only covered three to four years. During this period, black carbon is not decomposed at all," Schmidt explains. "But if nothing were to happen o it in the long run, we would be wading knee-deep in charcoal." From this, he concludes that the decomposition rates are somewhere between 100,000 and a couple of years. In order to cover such huge expanses of time, the Cologne scientists have looked for an already existing model system. Although black carbon deposits do not exist in Sung, on the shores of Lake Onega in Russia, a similar substance does occur. A graphite rock called shungite has been deposited there over a period of around two billion years. This graphite and black carbon have analogous structures, so that the researchers can examine the decomposition behavior of such carbon compounds with the aid of the old rock.

The graphite deposits cover an area of 9,000 square kilometers, which is around a quarter of the area of North Rhine-Westphalia. What is special about the area is that the shungite is a gigantic field experiment organized by nature, for ice scraped out this landscape 10,000 years ago, exposing the rock with a carbon content. This is precisely the period the researchers examine. It is only since then that the rock has weathered and new, fertile soil has formed. "It is like in a supermarket. We can take our pick of graphite qualities," says Schmidt. Since Shunga lies in a wide plain, no material from outside is washed or blown over the rock that would wear away the top layers. So the old carbon structures can decompose undisturbed.

The researchers now want to examine the rock layer by layer in order to analyze the step-by-step changes in the organic compounds. For chemical and biological decomposition lessens continuously from the surface to bottom. The scientists are drilling to get samples reaching down to a depth of ten meters. They can only hope that the graphite has not decomposed there yet since they have not had any experience with the decomposition zone of the shungite. However, under similar conditions, crude oil mother rock only decomposes down to a depth of five meters, Schmidt maintains. His team is examining the drilling cores under the microscope, and they are paying attention to how the material's appearance changes with progressive decomposition. Then they apply detailed chemical analysis methods. Isotope measuring, nuclear resonance spectroscopy and element analysis are just a few of the techniques they are using. The researchers hope that this will help them establish the link between the decomposition of black carbon and the missing carbon dioxide in the atmosphere. The mystery of the missing carbon in the air won't be solved before they have found out what happens to charcoal and soot particles from forest fires in the long run. Jo Schilling (dfd 6/2000

http://www.research-projects.unizh.ch/math/unit70600/area695/p2880.htm   TOP



Interpretive Summary:
The increase in carbon dioxide in the atmosphere has attracted interest due to potential global warming and the prospects of using the soil as storage for carbon released by other human activity. High levels of charcoal carbon resulting from repeated historical burning of grasslands, open woodlands and agricultural crop residues have been reported in soils from Australia and Germany. In this study, five U.S. soils were selected from long-term research plots in widely-different agricultural areas. The charcoal carbon content was estimated on each soil using sophisticated methods. These analyses showed that all five soils contained measurable amounts of charcoal carbon, and constituted up to 35% of the soil total organic carbon. The charcoal material had a plant-like morphology but was blocky and had fractured edges. The implications of this charcoal material, which must be highly resistant to microbiological decomposition, to the soil carbon cycle and issues such as greenhouse gas emissions from soil are important. The processes of charcoal formation, its biological, physical and chemical properties and distribution in many soils are largely unknown and require further study. Understanding the role of charcoal in nutrient cycling and C sequestration is vital for understanding the role and minimizing the impact of agriculture on climate change. This information will impact scientists around the world by allowing them to identify important forms of carbon and potential impact on global climate change. These results are significant to farmers and policy makers because carbon credits require understanding the function and form of soil carbon. This information will be of direct benefit to the farmers to enable them to maintain crop production with minimal impact on the environment.

http://www.nal.usda.gov/ttic/tektran/data/000011/49/0000114943.html          TOP

8. Selected text: A portion of : The OCR Carbon Dating Procedure and Its Application at the Rmiz Site, Czech Republic

The OCR Carbon Dating procedure measures the site-specific rate of biodegradation of organic carbon, either as soil humic material or as charcoal.  SLIDE 2 (Carbon cycle) While some forms of organic carbon, such as fresh organic matter, are quickly recycled, other more resistant forms, such as humus and charcoal, are recycled at a much slower rate.  This recycling follows a linear progression though time when considered within the site-specific context, and includes factors that influence biochemical degradation of organic carbon.  Charcoal and soil humic material, once though to be inert, are biologically recycled at a slow, but measurable, rate (Frink 1992).

    The effect of the biochemical degradation of charcoal and soil humic material is measured by a ratio of the total organic carbon to the readily oxidizable carbon in the soil sample.  In general, as the total amount of organic carbon decreases though time due to recycling, the relative percentage of readily oxidizable carbon increases.  This ratio is called the Oxidizable Carbon Ratio, or OCR.  The rate of biochemical degradation will vary within the specific physical and environmental contexts of the sample.  An age estimate of the organic carbon is determined through a systems formula that accounts for the biological influences of oxygen, moisture, temperature, carbon concentration, and the soil reactivity SLIDE 3 (OCRDATE formula).  Residual influences on this system are included through a statistically derived constant (Frink 1994). (click link below to read entire artile)

http://www.comp-archaeology.org/DougRmizOCRSAA1999.htm   TOP




Recent studies have demonstrated that carbonized organic matter, or charcoal,

within a soil context undergoes chemical changes over time (Frink 1992). These

changes are directly related to the age of the sample within the environmental contexts

of climate, biota, relief, and the soil chemical and textural matrix. Results from this

study determined that charcoal undergoes biochemical alterations over time which are

detectable through simple, inexpensive chemical procedures. Variability in the chemi-cal

analysis was found to be directly dependent on specific environmental factors such

as rain fall and temperature, and contextual factors such as soil texture, pH, and the

depth of the sample below the surface.

The two chemical analyses used in this procedure determine the total percent-age

of carbon and the percentage of readily oxidizable carbon in the sample. The

results are converted to a ratio of total carbon to the readily oxidizable carbon in each

sample, the Oxidizable Carbon Ratio ("OCR"). The OCR value is then factored into

an environmentally based contextual formula and an estimate of age results.

The data for climatic regimes and soil textures were given values based on an

arbitrary scale for statistical analyses in the initial study. Climatic regimes are theoreti-cal

constructs derived from the combined influence of precipitation and temperature

on soil development. Rainfall and temperature affect soil development in several ways.

With increased rainfall, carbonates and clay are leached from the soil and organic

decomposition increases. For every 10o centigrade rise in temperature, the speed of

chemical reaction increases by a factor of two to three times. Soil texture, the descrip-tion

of the size and percentage of individual soil particles, affects soil development by

regulating the diffusion of moisture and atmospheric gases. The preliminary study

revealed that the variability in the OCR was the result of the interdependent dynamics

of several environmental variables. However, the climatic regime and soil texture

heavily influenced the variability in the OCR reading. (Click on the link below for the full article)

http://members.aol.com/dsfrink/ocr/downloads/aproposedsolution.pdf     TOP


Douglas S. Frink


While few people would argue that the biochemical decomposition of organic

matter is independent from the environmental influences of heat, moisture, and O2, it

has been argued that the process of carbonization renders organic matter inert to these

influences (Dowman, 1970). The research leading to the development of the OCR-dating

procedure demonstrates that C, whether in the form of fresh plant litter or

charcoal, is subject to biochemical decomposition. Archaeologists who work in environments

conducive to biochemical decay are familiar with this fact. Cultural features

containing charcoal are common at recent open-air surface archaeological sites in the

dynamic mesic and thermic environmental regimes. Few, if any, such features are

found on early Holocene and late Pleistocene Period sites in similar contexts. Cultural

features containing charcoal from these early periods are found only under conditions

where the effects of the environment on the charcoal have been minimized. Caves and

rock shelters protect features from heat and humidity, and deeply buried features are

preserved by the reduction in available O2. Open-air surface areas expose archaeological

sites to the full impact of the environment. Older, exposed sites lack visibly identifiable

features due to the biochemical decomposition of charcoal.

(Click on the link below for the full article)

http://members.aol.com/dsfrink/ocr/downloads/applicationoftheocr.pdf       TOP



The OCR Carbon Dating procedure,developed by the Archaeology Consulting Team,

measures the site-specific rate of biodegredation of organic carbon,either as soil humic

material or as charcoal.The biological recycling of organic carbon is fundamental to

nearly all biological systems on this planet.While some forms of organic carbon,such

as fresh organic matter,are quickly recycled,other more resistant forms,such as hu-

mus and charcoal,are recycled at a much slower rate.This recycling follows a linear

progression though time when considered within the site-specific context,and in-

cludes the factors that influence biochemical degredation of organic carbon.Charcoal

and soil humic material,once thought to be inert,are biologically recycled at a slow

but measurable rate. (Click on the link below for the full article)

http://members.aol.com/dsfrink/ocr/downloads/ocrwatsonmound.pdf     TOP