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
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 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…
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
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…
In the Canadian province of Quebec, plant coal has been used as a substitute for peat and perlite in reforestation projects for the rearing of tree seedlings for some time. There are two reasons for this. On the one hand, prices for conventional planting…
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.
- 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
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
Thanks to biochar, a mighty soil rich in nutrients and humus has developed in some areas of the Amazon over the centuries. This can also be achieved on European soils. Bruno Glaser, soil biogeochemist and professor at the University of Halle, comes to this…
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…
If biochar is also composted, it is heavily loaded with nitrogen (nitrate) and promotes plant growth more strongly than uncomposted biochar. This was shown, among other things, in studies in which the effects of biochar were tested in the vineyard…
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