Biochar is
charcoalCharcoal is the blackish residue consisting of impure carbon obtained by removing water and other volatile constituents from animal and vegetation substances. Charcoal is usually produced by slow pyrolysis, the heating of wood, sugar, bone char, or other substances in the absence of oxygen...
created by
pyrolysisPyrolysis is the chemical decomposition of condensed organic substances by heating. The word is coined from the Greek-derived elements pyro "fire" and lysys "decomposition"....
of
biomassBiomass, a renewable energy source, is biological material derived from living, or recently living organisms, such as wood, waste, and alcohol fuels. Biomass is commonly plant matter grown to generate electricity or produce heat. For example, forest residues , yard clippings and wood chips may be...
. The resulting charcoal-like material is a form of
biosequestrationBiosequestration is the capture and storage of the atmospheric greenhouse gas carbon dioxide by an increased volume or quality of photosynthesis , as well as enhanced soil carbon in agriculture...
or atmospheric
carbon capture and storageCarbon capture and storage is a means of mitigating the contribution of fossil fuel emissions to global warming, based on capturing carbon dioxide from large point sources such as fossil fuel power plants, and store it away from atmosphere by different means...
. Charcoal is a stable solid and rich in
carbonCarbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
content, and thus, can be used to lock carbon in the
soilSoil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics. It is composed of particles of broken rock that have been altered by chemical and...
. Biochar is of increasing interest because of concerns about
climate changeClimate change is a change in the statistical distribution of weather over periods of time that range from decades to millions of years. It can be a change in the average weather or a change in the distribution of weather events around an average...
caused by emissions of
carbon dioxideCarbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state...
(CO
2) and other greenhouse gases (GHG). Carbon dioxide capture also ties up large amounts of
oxygenOxygen Oxygen Oxygen (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter) is the element with atomic number 8 and represented by the symbol O...
and requires energy for injection (as via
carbon capture and storageCarbon capture and storage is a means of mitigating the contribution of fossil fuel emissions to global warming, based on capturing carbon dioxide from large point sources such as fossil fuel power plants, and store it away from atmosphere by different means...
), whereas the biochar process breaks into the carbon dioxide cycle, thus releasing oxygen as did coal formation hundreds of millions of years ago. The
atmosphereAn atmosphere is a layer of gases that may surround a material body of sufficient mass, by the gravity of the body, and are retained for a longer duration if gravity is high and the atmosphere's temperature is low...
would be rebalanced more quickly this way.
Biochar is a way for carbon to be drawn from the atmosphere and is a solution to reducing the global impact of farming (and in reducing the impact from all agricultural waste). Since biochar can
sequester carbonCarbon capture and storage is a means of mitigating the contribution of fossil fuel emissions to global warming, based on capturing carbon dioxide from large point sources such as fossil fuel power plants, and store it away from atmosphere by different means...
in the soil for hundreds to thousands of years, it has received considerable interest as a potential tool to slow global warming. The burning and natural decomposition of trees and agricultural matter contributes a large amount of CO
2 released to the atmosphere. Biochar can store this carbon in the ground, potentially making a significant reduction in atmospheric GHG levels; at the same time its presence in the earth can improve water quality, increase soil fertility, raise agricultural productivity and reduce pressure on old growth forests.
Current biochar projects are small scale and make no significant impact on the overall global carbon budget, although expansion of this technique has been advocated as a
geoengineeringThe modern concept of geoengineering is usually taken to mean proposals to deliberately manipulate the Earth's climate to counteract the effects of global warming from greenhouse gas emissions...
approach. As trees pull down carbon dioxide and release oxygen very efficiently they are already well suited to geoengineering rather than the artificial trees proposed by some. Further research is in progress, notably by the
University of EdinburghThe University of Edinburgh founded in 1582, is an internationally renowned centre for teaching and research in Edinburgh, Scotland, UK. It is the sixth university to be established in the British Isles, making it one of the ancient universities of the United Kingdom.The university is amongst the...
, which has a dedicated research unit.
AgricharAgrichar is the global brand name and US registered trademark for the Biochar produced from the proprietary slow pyrolysis process useful in biosequestration of atmospheric C02, improving fertility of soils and reducing pressure on old growth forests....
is produced by Best Industries in Australia.
The approach which favors applications that benefit the poorest is gaining traction: in May 2009, the Biochar Fund received a grant from the Congo Basin Forest Fund to implement its concept in Central Africa. In this concept, biochar is a tool used to simultaneously slow down
deforestationDeforestation is the clearance of naturally occurring forests by the processes of logging and/or burning of trees in a forested area. There are several reasons deforestation occurs: trees or derived charcoal can be sold as a commodity and used by humans, while cleared land is used as pasture,...
, increase the
food securityFood security refers to the availability of food and one's access to it. A household is considered food secure when its occupants do not live in hunger or fear of starvation. According to the World Resources Institute, global per capita food production has been increasing substantially for the past...
of rural communities, provide
renewable energyRenewable energy is energy generated from natural resources—such as sunlight, wind, rain, tides, and geothermal heat—which are renewable . In 2006, about 18% of global final energy consumption came from renewables, with 13% coming from traditional biomass, such as wood-burning...
to them and sequester carbon.
History
Pre-Columbian Amazonian Natives used biochar to enhance soil productivity and made it by smoldering agricultural waste. European settlers called it
Terra Preta de IndioTerra preta refers to expanses of very dark, fertile anthropogenic soils found in the Amazon Basin. Terra preta owes its name to its very high charcoal content, and was indeed made by adding a mixture of charcoal, bone, and manure to the otherwise relatively infertile Amazonian soil over many years...
.
Biochar is a high-carbon, fine-grained residue which used to be produced using centuries-old techniques by smoldering biomass (i.e., covering burning biomass with soil and letting it smolder). The ancient method for producing biochar as a soil additive was the “pit” or “trench” method, which created
terra pretaTerra preta refers to expanses of very dark, fertile anthropogenic soils found in the Amazon Basin. Terra preta owes its name to its very high charcoal content, and was indeed made by adding a mixture of charcoal, bone, and manure to the otherwise relatively infertile Amazonian soil over many years...
, or dark soil.
Carbon sink potential
Biochar can sequester carbon in the soil for hundreds to thousands of years. Modern biochar is being developed using pyrolysis to heat biomass in the absence of oxygen in
kilnKilns are thermally insulated chambers, or ovens, in which controlled temperature regimes are produced. They are used to harden, burn or dry materials...
s. Modern biochar production can be combined with
biofuelBiofuel is defined as solid, liquid or gaseous fuel obtained from lifeless or living biological material and is similar to fossil fuels, which are derived from long dead biological material. Also, various plants and plant-derived materials are used for biofuel manufacturing...
production in a process that may produce 3 to 9 times more energy than invested, is carbon-negative (withdraws more carbon from the atmosphere than it releases) and rebuilds geological carbon sinks. This technique is advocated by prominent scientists such as
James HansenJames E. Hansen heads the NASA Goddard Institute for Space Studies in New York City, a part of the Goddard Space Flight Center in Greenbelt, Maryland, Earth Sciences Division. He has held this position since 1981...
, an internationally-renowned climate scientist and head of
NASA'sThe National Aeronautics and Space Administration is an agency of the United States government, responsible for the nation's public space program. NASA was established by the National Aeronautics and Space Act on July 29, 1958, replacing its predecessor, the National Advisory Committee for...
Goddard Institute for Space StudiesThe NASA Goddard Institute for Space Studies , at Columbia University in New York City, is a component laboratory of NASA's Goddard Space Flight Center Earth-Sun Exploration Division and a unit of The Earth Institute at Columbia University...
, and
James LovelockJames Ephraim Lovelock, CH, CBE, FRS is an independent scientist, author, researcher, environmentalist, and futurist who lives in Devon, England...
, creator of the
Gaia hypothesisThe Gaia hypothesis is an ecological hypothesis proposing that the biosphere and the physical components of the Earth are closely integrated to form a complex interacting system that maintains the climatic and biogeochemical conditions on Earth in a preferred homeostasis...
, for
mitigation of global warmingMitigation of global warming involves taking actions to reduce greenhouse gas emissions and to enhance sinks aimed at reducing the extent of global warming. This is in distinction to adaptation to global warming which involves taking action to minimize the effects of global warming. Mitigation is...
by
greenhouse gas remediationGreenhouse gas remediation projects are a type of geoengineering and seek to remove greenhouse gases from the atmosphere, and thus tackle the root cause of climate change. These techniques either directly remove greenhouse gases, or alternatively seek to influence natural processes to remove...
.
Biochar is a high-carbon, fine-grained residue which today is produced through modern pyrolysis processes. Pyrolysis is the direct thermal decomposition of biomass in the absence of oxygen to obtain an array of solid (biochar), liquid (bio-oil) and gas (
syngasSyngas is the name given to a gas mixture that contains varying amounts of carbon monoxide and hydrogen. Examples of production methods include steam reforming of natural gas or liquid hydrocarbons to produce hydrogen, the gasification of coal, biomass, and in some types of waste-to-energy...
) products. The specific yield from the pyrolysis is dependent on process conditions, and can be optimized to produce either energy or biochar. Even when optimized to produce
charChar is the solid material that remains after light gases and tar have been driven-out or released from a carbonaceous material, during the initial stage of combustion, which is known as carbonization, charring, devolatilization or pyrolysis...
rather than energy, the energy produced per unit energy input is higher than for
corn ethanolCorn ethanol is ethanol produced from corn as a biomass through industrial fermentation, chemical processing and distillation. It is primarily used in the United States as an alternative to gasoline and petroleum...
.
Use as a carbon sink
Biochar can be used to sequester carbon on centurial or even millennial time scales. Plant matter absorbs CO
2 from the atmosphere while growing. In the natural
carbon cycleThe carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth...
, plant matter decomposes rapidly after the plant dies, which emits CO
2; the overall natural cycle is carbon neutral. Instead of allowing the plant matter to decompose, pyrolysis can be used to sequester the carbon in a much more stable form. Biochar thus removes circulating CO
2 from the atmosphere and stores it in virtually permanent soil carbon pools, making it a carbon-negative process. In places like the Rocky Mountains, where beetles have been killing off vast swathes of pine trees, the utilization of pyrolysis to char the trees instead of letting them decompose into the atmosphere would
offset substantial amounts of CO2 emissionsA carbon offset is a financial instrument aimed at a reduction in greenhouse gas emissions. Carbon offsets are measured in metric tons of carbon dioxide-equivalent and may represent six primary categories of greenhouse gases...
. Although some organic matter is necessary for agricultural soil to maintain its productivity, much of the agricultural waste can be turned directly into biochar, bio-oil, and syngas. The use of pyrolysis also provides an opportunity for the processing of municipal waste into useful clean energy rather than increased problems with land space for storage.
Biochar is believed to have long mean residence times in the soil. While the methods by which biochar mineralizes (turns into CO
2) are not completely known, evidence from soil samples in the Amazon shows large concentrations of black carbon (biochar) remaining after they were abandoned thousands of years ago. The amount of time the biochar will remain in the soil depends on the feedstock material, how charred the material is, the surface:volume ratio of the particles, and the conditions of the soil the biochar is placed in. Estimates for the residence time range from 100 to 10,000 yrs, with 5,000 being a common estimate. Lab experiments confirm a decrease in carbon mineralization with increasing temperature, so carefully controlled charring of plant matter can increase the soil residence time of the biochar C.
Under some circumstances, the addition of biochar to the soil has been found to accelerate the mineralization of the existing soil organic matter, but this would only reduce and not suppress the net benefit gained by sequestering carbon in the soil by this method. Furthermore, the suggested soil conditions for the integration of biochar are in heavily degraded tropical soils used for agriculture, not organic matter-rich boreal forest soils (as tested in the above reference).
Assuming biochar is effective at storing carbon for adequately long periods of time, serious questions remain as to whether biochar will play a significant role in combatting global warming. First is a question of scale. Assuming a natural carbon cycle in which trees absorb and release 120 billion tonnes of carbon per year, and human-caused emissions of 8 billion to 10 billion tonnes per year, in order to address even half of human-caused emissions, biochar would require harvesting of 3% to 4% of the world's forests per year - an enormous undertaking.
Second is a combined question of policy and markets. Energy produced from producing biochar is less than that produced from burning biomass. Thus, in order to scale up biochar to industrial levels worldwide, there would need to be a significant price imposed on carbon emissions so as to make biochar more financially attractive than burning. Yet if there were a significant price on carbon emissions, alternative (non-biochar) techniques for carbon reduction would become increasingly cost-effective.
Enhancing soil
In addition to its potential for carbon sequestration, biochar has numerous co-benefits when added to soil. It can prevent the
leachingIn pedology, leaching is the loss of mineral and organic solutes due to percolation. It is a mechanism of soil formation. It is distinct from the soil forming process of eluviation, which is the loss of mineral and organic colloids. Leached and elluviated materials tend to be lost from top soil and...
of
nutrientA nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. Nutrients are the substances that enrich the body. They build and repair tissues, give heat and energy, and regulate body processes...
s out of the soil, increase the available nutrients for plant growth, increase water retention, and reduce the amount of fertilizer required. Additionally, it has been shown to decrease
N2ONitrous oxide, commonly known as happy gas or laughing gas, is a chemical compound with the chemical formula N
2O. At room temperature, it is a colorless non-flammable gas, with a pleasant, slightly sweet odor and taste. It is used in surgery and dentistry for its anesthetic and analgesic...
(Nitrous oxide) and
CH4Methane is a chemical compound with the chemical formula . It is the simplest alkane, and the principal component of natural gas. Methane's bond angles are 109.5 degrees. Burning methane in the presence of oxygen produces carbon dioxide and water. The relative abundance of methane and its clean...
(methane) emissions from soil, thus further reducing GHG emissions. Although it is far from a perfect solution in all economies, biochar can be utilized in many applications as a replacement for or co-terminous strategy with other
bioenergyBioenergy is renewable energy made available from materials derived from biological sources. In its most narrow sense it is a synonym to biofuel, which is fuel derived from biological sources...
production strategies. One of its most immediate uses is in switching from "slash-and-burn” to “
slash-and-charSlash-and-char is an alternative to slash-and-burn that has a lesser effect on the environment. It is the practice of charring the biomass resulting from the slashing, instead of burning it as in the slash-and-burn practice....
” to prevent the rapid deforestation and subsequent degradation of soils.
“Biochar sequestration does not require a fundamental scientific advance and the underlying production technology is robust and simple, making it appropriate for many regions of the world.” Johannes Lehmann, of Cornell University, estimates that pyrolysis will be cost feasible when the cost of a CO
2 ton reaches $37, (as of the end of June 2008,
CO2 is tradingEmissions trading is an administrative approach used to control pollution by providing economic incentives for achieving reductions in the emissions of pollutants. It is sometimes called cap-and-trade or cap-and-tax....
at $45/ton on the
European Climate ExchangeThe European Climate Exchange manages the product development and marketing for ECX Carbon Financial Instruments , listed and admitted for trading on the ICE Futures Europe electronic platform. It is no longer a subsidiary of the Chicago Climate Exchange but rather a sister company...
, or ECX) – so using pyrolysis for bioenergy production is feasible, even though it may be more expensive than
fossil fuelFossil fuels or mineral fuels are fuels formed by natural resources such as anaerobic decomposition of buried dead organisms. The age of the organisms and their resulting fossil fuels is typically millions of years, and sometimes exceeds 650 million years...
s at the moment.
Co-benefits for soil of pyrolysis
Biochar can be used as a
soil amendmentA soil conditioner, also called a soil amendment, is a material added to soil to improve plant growth and health. The type of conditioner added depends on the current soil composition, climate, and the type of plant. Some soils lack nutrients necessary for proper plant growth and others hold too...
to increase plant growth yield, improve water quality, reduce soil emissions of GHGs, reduce leaching of nutrients, reduce soil acidity, and reduce irrigation and fertilizer requirements. These properties are very dependent on the properties of the biochar, and may depend on regional conditions including soil type, condition (depleted or healthy), temperature, and humidity. Modest additions of biochar to soil were found to reduce N
2O emissions by up to 80% and completely suppress methane emissions.
Animal feed
Before incorporating biochar into the soil, it also has use as dietary supplement for animals, and traditionally as
charcoal biscuitCharcoal biscuit is a biscuit based on a powdered willow charcoal or activated carbon mixed with ordinary flour, and made into dough with butter, sugar and eggs.- History :...
s for humans. The effects of this are to provide additional minerals, maintain a healthy digestive system, reduce
flatulenceFlatulence is the expulsion through the rectum of a mixture of gases that are byproducts of the digestion process of mammals and other animals. The mixture of gases is known as flatus, fart, or simply gas, and is expelled from the rectum in a process colloquially referred to as "passing gas" or...
(which is a source of methane), and reduce the odour of and
ammoniaAmmonia is a compound of nitrogen and hydrogen with the formula NH
3. It is normally encountered as a gas with a characteristic pungent odor. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to foodstuffs and fertilizers...
emissions from slurry (ie. sweeten the dung). Nutrients in the dung become intimately mixed with the biochar, reducing the effort required to mix biochar with the soil.
Slash and char
Switching from slash-and-burn to slash-and-char techniques in Brazil can both decrease deforestation of the Amazon and increase the crop yield. Under the current method of slash-and-burn, only 3% of the carbon from the organic material is left in the soil.
Switching to slash-and-char can sequester up to 50% of the carbon in a highly stable form. Adding the biochar back into the soil rather than removing it all for energy production is necessary to avoid heavy increases in the cost and emissions from more required nitrogen fertilizers. Additionally, by improving the soil tilth, fertility, and productivity, the biochar enhanced soils can sustain agricultural production, whereas non-amended soils quickly become depleted of nutrients, and the fields are abandoned, leading to a continuous slash-and-burn cycle and the continued loss of tropical rainforest. Using pyrolysis to produce bio-energy also has the added benefit of not requiring infrastructure changes the way processing biomass for cellulosic
ethanolEthanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug, best known as the type of alcohol found in alcoholic beverages and in modern thermometers. Ethanol is one of the oldest recreational drugs...
does. Additionally, the biochar produced can be applied by the currently used tillage machinery or equipment used to apply fertilizer.
Energy production: bio-oil
Bio-oil can be used as a replacement for numerous applications where fuel oil is used, including fueling space heaters, furnaces, and boilers. Additionally, these biofuels can be used to fuel some combustion turbines and reciprocating engines, and as a source to create several chemicals. If bio-oil is used without modification, care must be taken to prevent emissions of black carbon and other particulates. Syngas and bio-oil can also be “upgraded” to transportation fuels like biodiesel and gasoline substitutes. If biochar is used for the production of energy rather than as a soil amendment, it can be directly substituted for any application that uses coal. pyrolysis also may be the most cost-effective way of producing electrical energy from biomaterial. Syngas can be burned directly, used as a fuel for gas engines and gas turbines, converted to clean diesel fuel through Fischer Tropsch or potentially used in the production of
methanolMethanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with formula CH3OH . It is toxic: drinking 10 ml will cause blindness, and as little as 100 ml will cause death...
and
hydrogenHydrogen is the chemical element with atomic number 1. It is represented by the symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly flammable diatomic gas with the molecular formula H
2...
.
Bio-oil has a much higher energy density than the raw biomass material. Mobile pyrolysis units can be used to lower the costs of transportation of the biomass itself if the biochar is returned to the soil and the syngas stream is used to power the process. Bio-oil contains organic acids which are corrosive to steel containers, has a high water vapor content which is detrimental to ignition, and, unless carefully cleaned, contains some biochar particles which can block injectors. The greatest potential for bio-oil seems to be its use in a bio-refinery, where compounds that are valuable chemicals, pesticides, pharmaceuticals or food additives are first extracted, and the remainder is either upgraded to fuel or reformed to syngas.
Production of biochar
The yield of products from pyrolysis varies heavily with temperature. The lower the temperature, the more char is created per unit biomass. High temperature pyrolysis is also known as gasification, and produces primarily syngas from the biomass. The two main methods of pyrolysis are “fast” pyrolysis and “slow” pyrolysis. Fast pyrolysis yields 60% bio-oil, 20% biochar, and 20% syngas, and can be done in seconds, whereas slow pyrolysis can be optimized to produce substantially more char (~50%), but takes on the order of hours to complete. For typical inputs, the energy required to run a “fast” pyrolyzer is approximately 15% of the energy that it outputs. Modern pyrolysis plants can be run entirely off of the syngas created by the pyrolysis process and thus output 3-9 times the amount of energy required to run. Alternatively, microwave technology has recently been used to efficiently convert organic matter to biochar on an industrial scale, producing ~50% char.
The ancient method for producing biochar as a soil additive was the “pit” or “trench” method, which created terra preta, or dark soil. While this method is still a potential to produce biochar in rural areas, it does not allow the harvest of either the bio-oil or syngas, and releases a large amount of CO
2, black carbon, and other GHGs (and potentially, toxins) into the air. Modern companies are producing commercial-scale systems to process agricultural waste, paper byproducts, and even municipal waste.
There are three primary methods for deploying a pyrolysis system. The first is a centralized system where all biomass in the region would be brought to a pyrolysis plant for processing. A second system would effectively mean a lower-tech pyrolysis kiln for each farmer or small group of farmers. A third system is a mobile system where a truck equipped with a pyrolyzer would be driven around to pyrolyze biomass. It would be powered using the syngas stream, return the biochar to the earth, and transport the bio-oil to a refinery or storage site. Whether a centralized system, a distributed system, or a mobile system is preferred is heavily dependent on the specific region. The cost of transportation of the liquid and solid byproducts, the amount of material to be processed in a region, and the ability to feed directly into the power grid are all factors to be considered when deciding on a specific implementation.
Unless crops are going to be dedicated to biochar production, the residue-to-product ratio (RPR) for the feedstock material is a useful gauge of the approximate amount of feedstock that can be obtained for pyrolysis after the primary product is harvested and the waste remains. The amount of crop residue available to be used for pyrolysis can be determined by using the RPR, and the collection factor (the percent of the residue not used for other things). For instance,
BrazilBrazil , officially the Federative Republic of Brazil , is a country in South America. It is the fifth largest country by geographical area, occupying nearly half of South America, the fifth most populous country, and the fourth most populous democracy in the world. Bounded by the Atlantic Ocean...
harvests approximately 460Mt of sugar cane annually, with an RPR of 0.30, and a collection factor (CF) of 0.70 for the sugar cane tops, which are normally burned on the field. This translates into approximately 100Mt of residue which can be pyrolyzed to create energy and soil additives annually. Adding in the
bagasseBagasse is the fibrous residue remaining after sugarcane or sorghum stalks are crushed to extract their juice and is currently used as a renewable resource in the manufacture of pulp and paper products and building materials....
(sugar cane waste) (RPR=0.29 CF=1.0) which is currently burned inefficiently in boilers, raises the total to 230 Mt of pyrolysis feedstock just from sugar cane residues. Some plant residue, however, must remain on the soil to avoid heavily increased costs and emissions from nitrogen fertilizers.
Commercial viability
Current biochar projects are small scale, though many developments show that organic matter can be efficiently turned into biochar, potentially making a significant impact on the overall global carbon budget.
See also
- Bioenergy in China
China has set the goal of attaining one percent of its renewable energy generation through bioenergy in 2020.The development of bioenergy in China is needed to meet the rising energy demand....
- Black carbon
Black carbon or BC is formed through the incomplete combustion of fossil fuels, biofuel, and biomass, and is emitted in both anthropogenic and naturally occurring soot. Black carbon warms the planet by absorbing heat in the atmosphere and by reducing albedo, the ability to reflect sunlight, when...
- Carbon sequestration
- Geoengineering
The modern concept of geoengineering is usually taken to mean proposals to deliberately manipulate the Earth's climate to counteract the effects of global warming from greenhouse gas emissions...
- Terra preta
Terra preta refers to expanses of very dark, fertile anthropogenic soils found in the Amazon Basin. Terra preta owes its name to its very high charcoal content, and was indeed made by adding a mixture of charcoal, bone, and manure to the otherwise relatively infertile Amazonian soil over many years...
- Pyrolysis
Pyrolysis is the chemical decomposition of condensed organic substances by heating. The word is coined from the Greek-derived elements pyro "fire" and lysys "decomposition"....