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Biokol är välkänt som ett alternativ för att mildra klimatförändringarna. Här vill vi ge helheten och återbesöka en del av den grundläggande vetenskapen bakom det.
Senast uppdaterad: 19 januari 2022
To grasp the bigger picture, one must start with the global carbon cycle (Figure 1, reproduced from Friedlingstein & colleagues (2020), available online).
Looking at the thick arrows, this figure tells us where anthropogenic emissions of carbon dioxide are distributed in various environmental compartments (ocean, atmosphere, terrestrial biosphere).
Now, looking at the thin arrows, the figures tells us about carbon cycling in the ocean, the terrestrial biosphere, rivers, lakes, and coastal areas. The geolocical carbon cycle is not visible, mainly because it is extremly slow (turnovers of millenias to millions of year) leading to small/neglectable natural flows. For the fast carbon cycles (daily to decadal & millenia turovers), the flows are much larger.
One is of particular interest to biobased technologies like biochar: the carbon cycle from vegetation, with its two main mechanisms photosynthesis & respiration. These flows are of about 120 GtC yr-1 (Ruy, Berry and Baldocchi, 2019). Biomass based removal technologies are basically trying to imbalance the two flows in this cycle: increase photosynthesis (biomass productivity) & slow down respirtation (biomass decomposition).
In short, the longer the better. At minima, to have an effect on the climate system, the removal should last significantly longer than the turover rate of the carbon cycle from which the removed carbon came from.
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There are few studies that estimated the potential for biochar production & related carbon sequestration in biochar. The potential could be up to 3 GtC yr-1 or, equivalently, 10 GtCO2 yr-1
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Biochar carbon sink, carbon sequestration, carbon removal, biochar decomposition, biochar stability, & climate impact of biochar systems.
All these terms are related. Some are synonyms. Some have different meanings. Let’s clarify them.
First, the largest difference is between the biochar carbon sink & climate change impact of a biochar system. It is illustrated in the Figure 2, below.
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Biochar stability estimates have been derived according to two main approaches:
Here, we only cover the second approach as it relies on actual observations and is becoming the dominant approach in the recent research literature.
The process to extrapolate incubation data to longer times is described in Figure 3, alongside with methodological choices that arise along the way.
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Financing action to mitigate climate change has a long history. For several decades, it took the form of climate compensation through the financing of projects that avoided fossil fuel emissions, deforestation, or encouraged replanting of trees. This was not without debate & distrust. Today, the compensation or offsetting market is moving towards new types of projects: carbon removal projects.
Let’s be clear:
When it comes to biochar, in the early 2020s, “biochar C removal certificates” have been defined & are being sold on a non-regulated voluntary market by a handful of organisations.
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Your biochar data | |||
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Calculation methods & returned values | ||||||||||
Method | IPCC (2019) |
IBI (2013) |
Spokas O:C (2010) |
EBC C-sink (Agro) |
EBC C-sink (Charcrete) |
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100-year stability (%) | n/a | n/a | n/a | n/a | n/a | |||||
100-year C sequestration (kg C/tonne biochar) |
n/a | n/a | n/a | n/a | n/a | |||||
100-year CO2 sequestration (kg CO2-eq/tonne biochar) |
n/a | n/a | n/a | n/a | n/a | |||||
CO2 sequestration after
years (kg CO2-eq/tonne biochar) |
n/a | n/a | n/a | n/a | n/a | |||||
Notes |
Enter your biochar properties in the first row for the calculations to start...
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