Acti­vat­ed Carbon

Feeding Char

What is it, anyway?

Biochar is a mate­r­i­al obtained by the car­bon­i­sa­tion of biomass. The biomass – e.g. green waste – is burned in tra­di­tion­al coal piles or in modern pyrol­y­sis plants with little oxygen. Ideally, this pro­duces highly porous biochar.

Advan­tages of biochar – Where is it used?

Depend­ing on the pro­cess­ing stage, biochar can be used in the fol­low­ing areas. As:


  • Soil con­di­tion­er
  • Feed addi­tion – in the form of feeding char
  • Addi­tive in the biogas process
  • Stable bedding
  • Aux­il­iary mate­r­i­al for composting
  • Filter media – in the form of acti­vat­ed carbon
  • Cos­met­ics and phar­ma­ceu­ti­cal addi­tives – in the form of acti­vat­ed carbon

Further advan­tages – CO2 foot­print and animal welfare

In addi­tion to the many pos­si­ble uses of biochar, the refine­ment of biomass also ben­e­fits the envi­ron­ment and improves animal welfare. For example, biochar binds CO2 and nitrous oxide, closes mate­r­i­al cycles and improves animal health in a com­plete­ly natural way when sup­plied as char­coal in feed.
The advan­tages of using biochar are man­i­fold. To shed more light on these diverse appli­ca­tions, you will find brief descrip­tions and media reports as well as a large number of spe­cial­ist reports. 

How does biochar work as a soil improver?

Where biochar is men­tioned as a soil improver, “terra preta” (black earth) is usually men­tioned. Terra preta refers to fertile, deep black soils in the Amazon region. This soil was created by Indians thou­sands of years ago, who enriched the nutri­ent-poor soil with a com­post­ed or fer­ment­ed mixture con­sist­ing of plant residues, manure and human faeces as well as coal from the hearths.
Biochar alone is not a fer­tilis­er. It is highly porous and has a surface area of up to 300m² per gram. Biochar acts as a sponge that can absorb up to five times its own weight. “Microor­gan­isms can settle here, water and nutri­ents can be stored,” explains Dr. Ines Vogel of Freie Uni­ver­sität Berlin. This prop­er­ty is called the adsorp­tion capac­i­ty (AC) of biochar for hydropho­bic sub­stances. It depends on both the pyrolyzed biomass and the pyrol­y­sis conditions.

To achieve the same effect as in the Amazon region, however, the biochar first needs to be ‘acti­vat­ed’, meaning it must be enriched with nutri­ents and soil organ­isms, for example, during com­post­ing. If pure biochar is intro­duced into the soil, it absorbs the water and sub­stances dis­solved therein from the envi­ron­ment. This of course has a neg­a­tive effect on plant growth and exactly the oppo­site of the desired effect is achieved. This is where the secret of terra preta soils comes in.

Biochar in the garden

Biochar doesn’t have to make a grand entrance. It also has an effect in small areas, such as your own garden or balcony box. Every­one can do some­thing good for their soil and at the same time help the climate.

Only com­post­ing turns dead coal into a living micro­cosm” (from: Ute Scheub, Haiko Piplow, Hans-Peter Schmidt: Terra Preta, Oekom Verlag 2015).

Biochar alone does not make a good garden soil. A handful of healthy earth con­tains more living beings than people on the planet: Bac­te­ria, fla­gel­la and cil­i­ates, fungi, algae, worms, beetles, larvae, snails, spiders, woodlice… Biochar offers these tiny organ­isms a living envi­ron­ment. It loosens the garden soil and makes it per­me­able to water and oxygen. Thanks to its huge surface and mul­ti­ple pores, biochar also has an excel­lent capac­i­ty to store nutri­ents and water. For biochar to work in the soil, it must first be loaded with microor­gan­isms and nutri­ents, oth­er­wise it is only an empty reser­voir. This is best done in the garden by mixing the compost with a maximum of 1/5 of the total amount of biochar and letting the mixture rest for a few weeks until it is humi­fied. This can also be done in small, stacked lattice boxes on the balcony. Learn more about it in this highly read­able book.

Recent con­tri­bu­tions on the subject of gardening

Terra Preta, the black revolution

Terra Preta, the black revolution

The authors Scheub, Pieplow and Schmidt describe how to produce healthy food in their own gardens and at the same time improve the climate in a highly read­able book about biochar. It describes step by step how biochar can best be used in the…

Biochar as a sub­sti­tute for peat

Biochar as a sub­sti­tute for peat

Biochar as a growth medium and as a sub­sti­tute for peat: The authors and sci­en­tists Steiner and Hartung have tested this in a study (“Biochar as a growing media addi­tive and peat sub­sti­tute, Solid Earth 2014). Because peat…

4 ways to “recharge” biochar with nutrients

4 ways to “recharge” biochar with nutrients

So that biochar can quickly and effi­cient­ly develop its soil-improv­ing effect in the garden, city park or on the field, biochar must first be “charged”. Mixing with compost is the most common method, but there are many other ways to…


Mil­lions of new trees are planted every year in Germany – to dec­o­rate spaces, as fruit trees or to improve air quality in urban areas. Their growth does not always progress smooth­ly; young trees increas­ing­ly suffer from stress, depend­ing on the loca­tion. Too narrow plant­i­ng pits restrict root growth and soil com­paction pre­vents suf­fi­cient oxygen and water from reach­ing the tree. What’s more, many trees suffer from cli­mat­ic changes such as rising tem­per­a­tures, increas­ing drought stress in summer and more fre­quent extreme weather events.

Some large cities such as Stock­holm, Mel­bourne or Toronto have there­fore switched over to plant­i­ng their trees in mixed sub­strates of gravel and biochar. Biochar is not only much more porous than sand or clay, it is also not biode­grad­ed or com­pact­ed as quickly as peat, for example. The high poros­i­ty of biochar increas­es gas exchange and water storage capac­i­ty and ensures enhanced root pen­e­tra­tion thanks to its high permeability.

Recent con­tri­bu­tions on trees

Pro­tect­ing urban trees with biochar

Pro­tect­ing urban trees with biochar

Urban trees are indis­pens­able for healthy air in cities. However, they are also exposed to special stress factors and there­fore have sig­nif­i­cant­ly shorter lifes­pans and higher main­te­nance costs. For this reason, the Swedish capital Stock­holm has been…

Biochar improves urban soils and tree growth

Biochar improves urban soils and tree growth

The growth of urban trees is often inhib­it­ed by low soil quality and numer­ous dis­turb­ing factors such as (air) pol­lu­tion or drought stress. There­fore, attempts are gen­er­al­ly made to stim­u­late the growth of urban trees through syn­thet­ic fertilizers…

Biochar in agri­cul­ture and in viticulture

In the field

“A healthy soil con­tains up to ten percent humus. Today it is usually only two to three percent,” notes Fredy Abächer­li, Man­ag­ing Direc­tor of Verora GmbH, a company that orga­nizes train­ing sem­i­nars on soil struc­ture, humus man­age­ment and com­post­ing. An intact humus layer stores both nutri­ents and water – biochar facil­i­tates this process. With a 

surface of 200 – 800m² per gram and a high poros­i­ty, biochar can absorb up to five times its own weight in water and the nutri­ents con­tained in it. It there­fore increas­es the water reten­tion capac­i­ty and reduces washout losses.
Biochar is not a fer­til­iz­er, but acts as a carrier for nutri­ents. This means that the biochar must be charged and/or bio­log­i­cal­ly acti­vat­ed. This is done, for example, by com­post­ing with biochar.

The coal remains stable during decom­po­si­tion and does not rot. It is there­fore suit­able for build­ing up humus and increas­ing the soil’s storage capacity.

Prof. Dr. Bruno Glaser of the Martin Luther Uni­ver­si­ty Halle-Wit­ten­berg describes the concept as a baking recipe for farmers. “You need the ingre­di­ents nutri­ents, biochar and soil organ­isms. The product depends on the quality of the ingre­di­ents and the “baker’s” exper­tise, i.e. the way the ingre­di­ents are processed.”

As a result, farmers are able to improve the quality of soil, save money for fer­tilis­ers and obtain addi­tion­al credits from emis­sion certificates.

Further advan­tages:

  • Less stench
  • Nitrate loads in soil and ground­wa­ter are con­sid­er­ably reduced
  • The for­ma­tion of climate-dam­ag­ing gases is con­sid­er­ably reduced
  • Soil acid­i­fi­ca­tion is reduced
  • The build-up of humus is strengthened
  • Plant nutri­ents remain avail­able much longer
  • The need for addi­tion­al fer­tilis­er is con­sid­er­ably reduced

In viti­cul­ture

The healthy devel­op­ment of the vine is strong­ly depen­dent on exter­nal envi­ron­men­tal influ­ences. The weather con­di­tions of the pre­vi­ous year have a strong influ­ence on the for­ma­tion and sub­se­quent devel­op­ment of the buds in the fol­low­ing spring. Expo­sure and tem­per­a­ture con­di­tions, but also the supply of nutri­ents and water play a central role here.

The use of biochar has mul­ti­ple advan­tages in the vine­yard: It loosens the garden soil and makes it per­me­able to water and oxygen. Impor­tant microor­gan­isms can settle in the soil, demon­stra­bly improv­ing soil fer­til­i­ty. Thanks to its huge surface area and high poros­i­ty, biochar also has an excel­lent capac­i­ty to store of nutri­ents and water. There­fore, the ability of the grapevines to with­stand extreme weather con­di­tions such as weeks of drought stress and sub­se­quent flood-like rain­fall is sig­nif­i­cant­ly improved.

Biochar has also proven to be an envi­ron­men­tal­ly friend­ly and effec­tive carrier of manure. Biochar reduces nutri­ent leach­ing and envi­ron­men­tal­ly harmful emis­sions. Last but not least, the use of biochar in the vine­yard is an impor­tant con­tri­bu­tion to climate pro­tec­tion: carbon is brought back into the soil from the CO2-con­t­a­m­i­nat­ed atmosphere.

Recent con­tri­bu­tions on agri­cul­ture and viticulture

Biochar approval

Biochar approval

Germany is still a laggard when it comes to the approval of biochar. Cur­rent­ly, it is only per­mit­ted in the form of char­coal with a carbon content of at least 80 percent. Tech­nol­o­gy has been avail­able for a long time to produce biochar free of…

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