Biochar is the solid byproduct of biomass' thermochemical conversion under oxygen-limited conditions. Its properties provide potential for long-term carbon storage in soil, offering a viable avenue for mitigating climate change effects by effectively sequestering carbon. Biochar's refractory stability ensures its persistence in soil for extended durations, potentially providing lasting benefits to agricultural ecosystems.
In agricultural settings, biochar demonstrates remarkable potential in improving
soil fertility and structure. Studies have shown positive correlations between biochar application and enhanced crop yields, particularly in degraded or nutrient-poor soils. By reducing leaching of critical nutrients and promoting nutrient uptake, biochar contributes to soil health and resilience, fostering sustainable agricultural practices.
Beyond its role in soil management, biochar finds application in diverse sectors, from
animal breeding to construction materials. As a feed additive, biochar shows promise in improving digestion and reducing
methane emissions in
livestock, highlighting its potential to address environmental challenges in animal agriculture. In the construction industry, biochar serves as a sustainable alternative to traditional concrete additives, offering reduced carbon emissions and enhanced material properties.
Despite its numerous benefits, the widespread adoption of biochar faces challenges and considerations. Concerns regarding its potential impact on soil pH levels and pesticide efficacy necessitate careful evaluation and implementation strategies. Additionally, economic factors such as production costs and scalability pose hurdles, particularly in resource-constrained agricultural settings.
As research into biochar continues to evolve, ongoing efforts seek to explore its full potential and address remaining uncertainties. Collaborative initiatives span across academic institutions, research organizations, and government agencies, reflecting a growing recognition of biochar's role in sustainable development and environmental stewardship.
History
The word "biochar" is a late 20th century English
neologism derived from the
Greek word βίος, bios, "
life" and "
char" (
charcoal produced by carbonization of biomass).[1] It is recognized as charcoal that participates in biological processes found in soil, aquatic habitats and in animal digestive systems.
Pre-ColumbianAmazonians produced biochar by
smoldering agricultural waste (i.e., covering burning biomass with soil)[2] in pits or trenches.[3] It is not known if they intentionally used biochar to enhance soil productivity.[3] European settlers called it terra preta de Indio.[4] Following observations and experiments, a research team working in
French Guiana hypothesized that the Amazonian
earthwormPontoscolex corethrurus was the main agent of fine powdering and incorporation of charcoal debris in the mineral soil.[5]
Production
Biochar is a high-carbon, fine-grained residue that is produced via
pyrolysis; it is the direct
thermal decomposition of biomass in the absence of
oxygen (preventing
combustion), which produces a mixture of solids (the biochar proper), liquid (
bio-oil), and gas (
syngas) products.[6]
Gasifiers produce most of the biochar sold in the United States.[7] The gasification process consists of four main stages: oxidation, drying, pyrolysis, and
reduction.[8] Temperature during pyrolysis in gasifiers is 250–550 °C (523–823 K), 600–800 °C (873–1,073 K) in the reduction zone and 800–1,000 °C (1,070–1,270 K) in the combustion zone.[9]
The specific yield from
pyrolysis is dependent on process conditions such as
temperature,
residence time, and heating rate.[10] These parameters can be tuned to produce either energy or biochar.[11] Temperatures of 400–500 °C (673–773 K) produce more
char, whereas temperatures above 700 °C (973 K) favor the yield of liquid and gas fuel components.[12] Pyrolysis occurs more quickly at higher temperatures, typically requiring seconds rather than hours. The increasing heating rate leads to a decrease of biochar yield, while the temperature is in the range of 350–600 °C (623–873 K).[13] Typical yields are 60%
bio-oil, 20% biochar, and 20% syngas. By comparison, slow pyrolysis can produce substantially more char (≈35%);[12] this contributes to soil fertility. Once initialized, both processes produce net energy. For typical inputs, the energy required to run a "fast" pyrolyzer is approximately 15% of the energy that it outputs.[14] Pyrolysis plants can use the syngas output and yield 3–9 times the amount of energy required to run.[3]
Besides pyrolysis,
torrefaction and
hydrothermal carbonization processes can also thermally decompose biomass to the solid material. However, these products cannot be strictly defined as biochar. The carbon product from the
torrefaction process contains some
volatile organic components, thus its properties are between that of biomass feedstock and biochar.[15] Furthermore, even the hydrothermal carbonization could produce a carbon-rich solid product, the hydrothermal carbonization is evidently different from the conventional thermal conversion process.[16] Therefore, the solid product from hydrothermal carbonization is defined as "hydrochar" rather than "biochar".
The Amazonian pit/ trench method[3] harvests neither bio-oil nor syngas, and releases CO2,
black carbon, and other
greenhouse gases (GHGs) (and potentially,
toxicants) into the air, though less greenhouse gasses than captured during the growth of the biomass. Commercial-scale systems process agricultural waste, paper byproducts, and even municipal waste and typically eliminate these side effects by capturing and using the liquid and gas products.[17][18] The 2018 winner of the
X Prize Foundation for
atmospheric water generators harvests potable water from the drying stage of the gasification process.[19][20] The production of biochar as an output is not a priority in most cases.
Smallholder farmers in developing countries easily produce their own biochar without special equipment. They make piles of crop waste (e.g., maize stalks, rice straw or wheat straw), light the piles on the top and quench the embers with dirt or water to make biochar. This method greatly reduces smoke compared to traditional methods of burning crop waste. This method is known as the top down burn or conservation burn.[22][23][24]
Centralized, decentralized, and mobile systems
In a centralized system, unused biomass is brought to a central plant[25] for processing into biochar. Alternatively, each farmer or group of farmers can operate a
kiln. Finally, a truck equipped with a pyrolyzer can move from place to place to pyrolyze biomass. Vehicle power comes from the
syngas stream, while the biochar remains on the farm. The
biofuel is sent to a refinery or storage site. Factors that influence the choice of system type include the cost of transportation of the liquid and solid byproducts, the amount of material to be processed, and the ability to supply the power grid.
Common crops used for making biochar include various tree species, as well as various
energy crops. Some of these energy crops (i.e.
Napier grass) can store much more carbon on a shorter timespan than trees do.[26]
For crops that are not exclusively for biochar production, the
Residue-to-Product Ratio (RPR) and the collection factor (CF), the percent of the residue not used for other things, measure the approximate amount of feedstock that can be obtained. For instance,
Brazil harvests approximately 460 million tons (MT) of
sugarcane annually,[27] with an RPR of 0.30, and a CF of 0.70 for the sugarcane tops, which normally are burned in the field.[28] This translates into approximately 100 MT of residue annually, which could be pyrolyzed to create energy and soil additives. Adding in the
bagasse (sugarcane waste) (RPR=0.29 CF=1.0), which is otherwise burned (inefficiently) in boilers, raises the total to 230 MT of pyrolysis feedstock. Some plant residue, however, must remain on the soil to avoid increased costs and emissions from nitrogen fertilizers.[29]
Various companies in
North America,
Australia, and
England sell biochar or biochar production units. In Sweden the 'Stockholm Solution' is an urban tree planting system that uses 30% biochar to support urban forest growth.[30]
At the 2009 International Biochar Conference, a mobile pyrolysis unit with a specified intake of 1,000 pounds (450 kg) was introduced for agricultural applications.[31]
Thermo-catalytic depolymerization
Alternatively, "thermo-catalytic depolymerization", which utilizes
microwaves, has been used to efficiently convert organic matter to biochar on an industrial scale, producing ≈50% char.[32][33]
Properties of biochar and activated biochar
The physical and chemical properties of biochars as determined by feedstocks and technologies are crucial. Characterization data explain their performance in a specific use. For example, guidelines published by the International Biochar Initiative provide standardized evaluation methods.[6] Properties can be categorized in several respects, including the
proximate and elemental composition, pH value, and porosity. The atomic ratios of biochar, including H/C and O/C, correlate with the properties that are relevant to organic content, such as
polarity and
aromaticity.[34] A
van-Krevelen diagram can show the evolution of biochar atomic ratios in the production process.[35] In the carbonization process, both the
H/
C and
O/C
atomic ratios decrease due to the release of functional groups that contain hydrogen and oxygen.[36]
Production temperatures influence biochar properties in several ways. The molecular carbon structure of the solid biochar matrix is particularly affected. Initial pyrolysis at 450–550 °C leaves an
amorphous carbon structure. Temperatures above this range will result in the progressive thermochemical conversion of amorphous carbon into turbostratic
graphene sheets. Biochar
conductivity also increases with production temperature.[37][38][39] Important to carbon capture, aromaticity and intrinsic recalcitrance increases with temperature.[40]
A 2010 report estimated that sustainable use of biochar could reduce the global net emissions of carbon dioxide (CO 2),
methane, and
nitrous oxide by up to 1.8 billion tonnes
carbon dioxide equivalent (CO 2e) per year (compared to the about 50 billion tonnes emitted in 2021), without endangering
food security,
habitats, or
soil conservation.[45] However a 2018 study doubted enough biomass would be available to achieve significant carbon sequestration.[57] A 2021 review estimated potential CO2 removal from 1.6 to 3.2 billion tonnes per year,[58] and by 2023 it had become a lucrative business renovated by carbon credits.[59]
As of 2023, the significance of biochar's potential as a carbon sink is widely accepted. Biochar is found to have the technical potential to sequester 7% of carbon dioxide in average of all countries, with twelve nations able to sequester over 20% of their greenhouse gas emissions.[60] Bhutan leads this proportion (68%), followed by India (53%).
In 2021 the cost of biochar ranged around European carbon prices,[61] but was not yet included in the EU or
UK Emissions Trading Scheme.[62]
In developing countries, biochar derived from
improved cookstoves for home-use can contribute[clarification needed] to lower
carbon emissions if use of original cookstove is discontinued, while achieving other benefits for sustainable development.[63]
Soil amendment
Biochar offers multiple
soil health benefits in degraded tropical soils but is less beneficial in temperate regions.[64][65] Its porous nature is effective at retaining both water and water-soluble nutrients. Soil biologist
Elaine Ingham highlighted its suitability as a habitat for beneficial soil
micro organisms.[66] She pointed out that when pre-charged with these beneficial organisms, biochar promotes good soil and plant health.
Biochar reduces leaching of E-coli through sandy soils depending on application rate, feedstock, pyrolysis temperature,
soil moisture content,
soil texture, and surface properties of the bacteria.[67][68][69]
For plants that require high
potash and elevated
pH,[70] biochar can improve yield.[71]
Biochar's impacts are dependent on its properties[77] as well as the amount applied,[76] although knowledge about the important mechanisms and properties is limited.[78] Biochar impact may depend on regional conditions including soil type, soil condition (depleted or healthy), temperature, and humidity.[79] Modest additions of biochar reduce
nitrous oxide (N 2O)[80] emissions by up to 80% and eliminate
methane emissions, which are both more potent greenhouse gases than CO2.[81]
Studies reported positive effects from biochar on crop production in degraded and nutrient–poor soils.[82] The application of
compost and biochar under FP7 project FERTIPLUS had positive effects on soil humidity, crop productivity and quality in multiple countries.[83] Biochar can be adapted with specific qualities to target distinct soil properties.[84] In Colombian savanna soil, biochar reduced leaching of critical nutrients, created a higher nutrient uptake, and provided greater nutrient availability.[85] At 10% levels biochar reduced contaminant levels in plants by up to 80%, while reducing
chlordane and
DDX content in the plants by 68 and 79%, respectively.[86] However, because of its high adsorption capacity, biochar may reduce pesticide efficacy.[87][88] High-surface-area biochars may be particularly problematic.[87]
Biochar may be plowed into soils in crop fields to enhance their fertility and stability and for medium- to long-term carbon sequestration in these soils. It has meant a remarkable improvement in tropical soils showing positive effects in increasing soil fertility and improving disease resistance in West European soils.[83] Gardeners taking
individual action on climate change add biochar to soil,[89] increasing plant yield and thereby drawing down more carbon.[90] The use of biochar as a feed additive can be a way to apply biochar to pastures and to reduce methane emissions.[91][92]
Application rates of 2.5–20 tonnes per hectare (1.0–8.1 t/acre) appear required to improve plant yields significantly. Biochar costs in developed countries vary from $300–7000/tonne, which is generally impractical for the farmer/horticulturalist and prohibitive for low-input field crops. In developing countries, constraints on agricultural biochar relate more to biomass availability and production time. A compromise is to use small amounts of biochar in lower-cost biochar-fertilizer complexes.[93]
Slash-and-char
Switching from slash-and-burn to slash-and-char farming techniques in Brazil can decrease both deforestation of the
Amazon basin and
carbon dioxide emission, as well as increase crop yields. Slash-and-burn leaves only 3% of the carbon from the organic material in the soil.[94] Slash-and-char can retain up to 50%.[95] Biochar reduces the need for nitrogen fertilizers, thereby reducing cost and emissions from fertilizer production and transport.[96] Additionally, by improving soil's till-ability, its fertility and its productivity, biochar-enhanced soils can indefinitely sustain agricultural production, whereas slash/ burn soils quickly become depleted of nutrients, forcing farmers to abandon the fields, producing a continuous slash and burn cycle. Using pyrolysis to produce bio-energy does not require infrastructure changes the way, for example, processing biomass for
cellulosic ethanol does. Additionally, biochar can be applied by the widely used machinery.[97]
Biochar has been used in animal feed for centuries.[99]
Doug Pow, a
Western Australian farmer, explored the use of biochar mixed with
molasses as stock
fodder. He asserted that in
ruminants, biochar can assist digestion and reduce
methane production. He also used
dung beetles to work the resulting biochar-infused dung into the soil without using machinery. The nitrogen and carbon in the dung were both incorporated into the soil rather than staying on the soil surface, reducing the production of
nitrous oxide and
carbon dioxide. The nitrogen and carbon added to soil fertility. On-farm evidence indicates that the fodder led to improvements of liveweight gain in
Angus-cross cattle.[100]
Doug Pow won the Australian Government Innovation in Agriculture Land Management Award at the 2019 Western Australian
Landcare Awards for this innovation.[101][100] Pow's work led to two further trials on dairy cattle, yielding reduced odour and increased milk production.[102]
Concrete Additive
Ordinary
Portland cement (OPC), an essential component of concrete mix, is energy- and emissions-intensive to produce; cement production accounts for around 8% of global CO2 emissions.[103] The concrete industry has increasingly shifted to using supplementary cementitious materials (SCMs), additives that reduce the volume of OPC in a mix while maintaining or improving concrete properties.[104] Biochar has been shown to be an effective SCM, reducing concrete production emissions while maintaining required strength and ductility properties.[105][106]
Studies have found that a 1-2% weight concentration of biochar is optimal for use in concrete mixes, from both a cost and strength standpoint.[105] A 2 wt.% biochar solution has been shown to increase concrete flexural strength by 15% in a three-point bending test conducted after 7 days, compared to traditional OPC concrete.[106] Biochar concrete also shows promise in high temperature resistance and permeability reduction.[107]
A cradle-to-gate
life cycle assessment of biochar concrete showed decreased production emissions with higher concentrations of biochar, which tracks with a reduction in OPC.[108] Compared to other SCMs from industrial waste streams (such as
fly ash and
silica fume), biochar also showed decreased toxicity.
Energy carrier
Biochar mixed with liquid media such as water or organic liquids (ethanol, etc) is an emerging fuel type known as biochar-based slurry.[109] Adapting slow pyrolysis in large biomass fields and installations enables the generation of biochar slurries with unique characteristics. These slurries are becoming promising fuels in countries with regional areas where biomass is abundant, and power supply relies heavily on diesel generators. [110] This type of fuel resembles a
coal slurry, but with the advantage that it can be derived from biochar from renewable resources.
Long-term effects of biochar on
carbon sequestration have been examined using soil from arable fields in Belgium with charcoal-enriched black spots dating from before 1870 from charcoal production mound kilns.
Topsoils from these 'black spots' had a higher organic C concentration [3.6 ± 0.9% organic carbon (OC)] than adjacent soils outside these black spots (2.1 ± 0.2% OC). The soils had been cropped with maize for at least 12 years which provided a continuous input of C with a C isotope signature (δ13C) −13.1, distinct from the δ13C of soil organic carbon (−27.4 ‰) and charcoal (−25.7 ‰) collected in the surrounding area. The isotope signatures in the soil revealed that maize-derived C concentration was significantly higher in charcoal-amended samples ('black spots') than in adjacent unamended ones (0.44% vs. 0.31%; p = 0.02). Topsoils were subsequently collected as a gradient across two 'black spots' along with corresponding adjacent soils outside these black spots and
soil respiration, and physical soil fractionation was conducted. Total soil respiration (130 days) was unaffected by charcoal, but the maize-derived C respiration per unit maize-derived OC in soil significantly decreased about half (p < 0.02) with increasing charcoal-derived C in soil. Maize-derived C was proportionally present more in protected soil aggregates in the presence of charcoal. The lower specific mineralization and increased C sequestration of recent C with charcoal are attributed to a combination of physical protection, C saturation of microbial communities and, potentially, slightly higher annual primary production. Overall, this study evidences the capacity of biochar to enhance C sequestration through reduced C turnover.[117]
Biochar sequesters carbon (C) in soils because of its prolonged residence time, ranging from years to millennia. In addition, biochar can promote indirect C-sequestration by increasing crop yield while, potentially, reducing C-mineralization. Laboratory studies have evidenced effects of biochar on C-mineralization using 13 C signatures.[118]
Fluorescence analysis of biochar-amended soil dissolved organic matter revealed that biochar application increased a humic-like fluorescent component, likely associated with biochar-carbon in solution. The combined spectroscopy-microscopy approach revealed the accumulation of aromatic-carbon in discrete spots in the solid-phase of microaggregates and its co-localization with clay minerals for soil amended with raw residue or biochar. The co-localization of aromatic-C: polysaccharides-C was consistently reduced upon biochar application. These finding suggested that reduced C metabolism is an important mechanism for C stabilization in biochar-amended soils.[119]
Research and practical investigations into the potential of biochar for coarse soils in semi-arid and degraded ecosystems are ongoing. In
Namibia biochar is under exploration as
climate change adaptation effort, strengthening local communities' drought resilience and
food security through the local production and application of biochar from abundant
encroacher biomass.[120]
^Solomon, Dawit; Lehmann, Johannes; Thies, Janice; Schäfer, Thorsten; Liang, Biqing; Kinyangi, James; Neves, Eduardo; Petersen, James; Luizão, Flavio; Skjemstad, Jan (May 2007).
"Molecular signature and sources of biochemical recalcitrance of organic C in Amazonian Dark Earths". Geochimica et Cosmochimica Acta. 71 (9): 2285–2298.
Bibcode:
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doi:
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ISSN0016-7037.
Archived from the original on 22 November 2021. Retrieved 9 August 2021. "Amazonian Dark Earths (ADE) are a unique type of soils apparently developed between 500 and 9000 years B.P. through intense anthropogenic activities such as biomass-burning and high-intensity nutrient depositions on pre-Columbian Amerindian settlements that transformed the original soils into Fimic Anthrosols throughout the Brazilian Amazon Basin
^
abcdLehmann 2007a, pp. 381–387 Similar soils are found, more scarcely, elsewhere in the world. To date, scientists have been unable to completely reproduce the beneficial growth properties of terra preta. It is hypothesized that part of the alleged benefits of terra preta require the biochar to be aged so that it increases the cation exchange capacity of the soil, among other possible effects. In fact, there is no evidence natives made biochar for soil treatment, but rather for transportable fuel charcoal; there is little evidence for any hypothesis accounting for the frequency and location of terra preta patches in Amazonia. Abandoned or forgotten charcoal pits left for centuries were eventually reclaimed by the forest. In that time, the initially harsh negative effects of the char (high pH, extreme ash content, salinity) wore off and turned positive as the forest soil ecosystem saturated the charcoals with nutrients. supra note 2 at 386 ("Only aged biochar shows high cation retention, as in Amazonian Dark Earths. At high temperatures (30–70 °C), cation retention occurs within a few months. The production method that would attain high CEC in soil in cold climates is not currently known.") (internal citations omitted).
^Glaser, Lehmann & Zech 2002, pp. 219–220 "These so-called Terra Preta do Indio (Terra Preta) characterize the settlements of pre-Columbian Indios. In Terra Preta soils large amounts of black C indicate a high and prolonged input of carbonized organic matter probably due to the production of charcoal in hearths, whereas only low amounts of charcoal are added to soils as a result of forest fires and slash-and-burn techniques." (internal citations omitted)
^Amonette, James E; Blanco-Canqui, Humberto; Hassebrook, Chuck; Laird, David A;
Lal, Rattan; Lehmann, Johannes; Page-Dumroese, Deborah (January 2021).
"Integrated biochar research: A roadmap". Journal of Soil and Water Conservation. 76 (1): 24A–29A.
doi:10.2489/jswc.2021.1115A.
OSTI1783242.
S2CID231588371. Large-scale wood gasifiers used to generate bioenergy, however, are relatively common and currently provide the majority of the biochar sold in the United States. Consequently, one of these full-scale facilities would be used to produce a standard wood biochar made from the same feedstock to help calibrate results across the regional sites.
^Akhtar, Ali; Krepl, Vladimir; Ivanova, Tatiana (5 July 2018). "A Combined Overview of Combustion, Pyrolysis, and Gasification of Biomass". Energy Fuels. 32 (7): 7294–7318.
doi:
10.1021/acs.energyfuels.8b01678.
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^Tripathi, Manoj; Sabu, J.N.; Ganesan, P. (21 November 2015). "Effect of process parameters on production of biochar from biomass waste through pyrolysis: A review". Renewable and Sustainable Energy Reviews. 55: 467–481.
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^Gaunt & Lehmann 2008, pp. 4152, 4155 ("Assuming that the energy in syngas is converted to electricity with an efficiency of 35%, the recovery in the life cycle energy balance ranges from 92 to 274 kg CO2 MWn−1 of electricity generated where the pyrolysis process is optimized for energy and 120 to 360 kg CO2 MWn−1 where biochar is applied to land. This compares to emissions of 600–900 kg CO 2 MWh−1 for fossil-fuel-based technologies.)
^
abWinsley, Peter (2007). "Biochar and bioenergy production for climate change mitigation". New Zealand Science Review. 64. (See Table 1 for differences in output for Fast, Intermediate, Slow, and Gasification).
^Aysu, Tevfik; Küçük, M. Maşuk (16 December 2013). "Biomass pyrolysis in a fixed-bed reactor: Effects of pyrolysis parameters on product yields and characterization of products". Energy. 64 (1): 1002–1025.
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ISSN0360-5442.
^Laird 2008, pp. 100, 178–181 "The energy required to operate a fast pyrolyzer is ≈15% of the total energy that can be derived from the dry biomass. Modern systems are designed to use the syngas generated by the pyrolyzer to provide all the energy needs of the pyrolyzer."
^Kambo, Harpreet Singh; Dutta, Animesh (14 February 2015). "A comparative review of biochar and hydrochar in terms of production, physicochemical properties and applications". Renewable and Sustainable Energy Reviews. 45: 359–378.
doi:
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ISSN1364-0321.
^Laird 2008, pp. 179 "Much of the current scientific debate on the harvesting of biomass for bioenergy is focused on how much can be harvested without doing too much damage."
^Mochidzuki, Kazuhiro; Soutric, Florence; Tadokoro, Katsuaki; Antal, Michael Jerry; Tóth, Mária; Zelei, Borbála; Várhegyi, Gábor (2003).
"Electrical and Physical Properties of Carbonized Charcoals". Industrial & Engineering Chemistry Research. 42 (21): 5140–5151.
doi:
10.1021/ie030358e. (observed five) orders of magnitude decrease in the electrical resistivity of charcoal with increasing HTT from 650 to 1050°C
^Constanze Werner, Hans-Peter Schmidt, Dieter Gerten, Wolfgang Lucht und Claudia Kammann (2018). Biogeochemical potential of biomass pyrolysis systems for limiting global warming to 1.5 °C.
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^Lehmann, Johannes.
"Terra Preta de Indio". Soil Biochemistry (Internal Citations Omitted).
Archived from the original on 24 April 2013. Retrieved 15 September 2009. Not only do biochar-enriched soils contain more carbon - 150gC/kg compared to 20-30gC/kg in surrounding soils - but biochar-enriched soils are, on average, more than twice as deep as surrounding soils.[citation needed]
^Lehmann 2007b "this sequestration can be taken a step further by heating the plant biomass without oxygen (a process known as low-temperature pyrolysis)."
^Lehmann 2007a, pp. 381, 385 "pyrolysis produces 3–9 times more energy than is invested in generating the energy. At the same time, about half of the carbon can be sequestered in soil. The total carbon stored in these soils can be one order of magnitude higher than adjacent soils.
^Abit, S.M.; Bolster, C.H.; Cai, P.; Walker, S.L. (2012). "Influence of feedstock and pyrolysis temperature of biochar amendments on transport of Escherichia coli in saturated and unsaturated soil". Environmental Science & Technology. 46 (15): 8097–8105.
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^Abit, S.M.; Bolster, C.H.; Cantrell, K.B.; Flores, J.Q.; Walker, S.L. (2014). "Transport of Escherichia coli, Salmonella typhimurium, and microspheres in biochar-amended soils with different textures". Journal of Environmental Quality. 43 (1): 371–378.
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^Glaser, Lehmann & Zech 2002, pp. 224 note 7 "Three main factors influence the properties of charcoal: (1) the type of organic matter used for charring, (2) the charring environment (e.g. temperature, air), and (3) additions during the charring process. The source of charcoal material strongly influences the direct effects of charcoal amendments on nutrient contents and availability."
^Dr. Wardle points out that improved plant growth has been observed in tropical (depleted) soils by referencing Lehmann, but that in the boreal (high native
soil organic matter content) forest this experiment was run in, it accelerated the native soil organic matter loss. Wardle, supra note 18. ("Although several studies have recognized the potential of black C for enhancing ecosystem carbon sequestration, our results show that these effects can be partially offset by its capacity to stimulate loss of native soil C, at least for boreal forests.") (internal citations omitted) (emphasis added).
^Lehmann 2007a, pp. note 3 at 384 "In greenhouse experiments, NOx emissions were reduced by 80% and methane emissions were completely suppressed with biochar additions of 20 g kg-1 (2%) to a forage grass stand."
^Elmer, Wade, Jason C. White, and Joseph J. Pignatello. Impact of Biochar Addition to Soil on the Bioavailability of Chemicals Important in Agriculture. Rep. New Haven: University of Connecticut, 2009. Print.
^Gaunt & Lehmann 2008, pp. 4152 note 3 ("This results in increased crop yields in low-input agriculture and increased crop yield per unit of fertilizer applied (fertilizer efficiency) in
high-input agriculture as well as reductions in off-site effects such as runoff, erosion, and gaseous losses.")
^Lehmann 2007b, pp. note 9 at 143 "It can be mixed with manures or fertilizers and included in no-tillage methods, without the need for additional equipment."
^
abDaly, Jon (18 October 2019).
"Poo-eating beetles and charcoal used by WA farmer to combat climate change". ABC News. Australian Broadcasting Corporation.
Archived from the original on 18 October 2019. Retrieved 18 October 2019. Mr Pow said his innovative farming system could help livestock producers become more profitable while helping to address the impact of climate change.
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