Biochar.
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

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.

Trees

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.

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

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