Biochar, The Soil Capacitor

Work With Nature

David talks about his biochar experiments and that got me thinking…

Recently I watched a great talk about the negative priming effects of pyrogenic carbon on soil organic carbon that you may find interesting:

Extrapolating from Silene’s results, when biochar concentration is high enough (~3%) there should be a halving of soil organic carbon (SOC) priming, and this should cause a doubling of SOC sequestration and effectively grow high carbon content Terra Preta soils faster. This correlates well with other research I’ve seen by David Johnson.

What the biochar is doing is interesting. I’ve hypothesised that microbes change metabolic strategy in the presence of enough carbon and in particular high electron transfer biochar, as recently biochar has been shown to increase electron transfer within soils.

So in addition to nutrient sorption, biochar may be acting as a sort of microbe electricity grid, and moving their metabolism from one of oxidation to reduction as they get their energy from the grid, thereby facilitating more SOC sequestration.

If this is the case, to facilitate this we may want high electron transfer biochars that have large surface areas that are effectively many aggregate soil capacitors, which made me think of Robert Murray-Smith’s recent videos in which he creates his own graphene inks for batteries and capacitors, and has been recently been talking about his strange capacitors.

I know from other research that the most productive soils long-term are those that are most connected ecologically, not fungal dominated, though that helps up to a point, and creating these connected soils is important if we want productive systems. This electron transfer effect that biochar has may be one small part of the puzzle along with plant roots, mycorrhizal fungi and other interconnected ecosystems we’ve yet to discover.

Also, if I calculated correctly, in Silene’s video, 450C carbon-13 tagged biochar soil appears to respire at a rate about 13x slower than SOC, so it’s not going to stay around forever.

Kids & Sticky-finger Superbugs on Farms

A study about superbugs on industrial hog farms using antibiotics claims children of workers were more than twice as likely to have their noses stuffed with drug-resistant germs than other kids. That the sticky fingers of booger-mining kids could be important spreaders of drug-resistant germs, something to be aware of. You can read about it on ars:

Careful where you barefoot.

Elephantiasis podoconiosis is caused by repeatedly walking barefoot in volcanic soils, which contain tiny, sharp mineral crystals that can penetrate the soles of the feet. Once these crystals are under the skin, they provoke repeated cycles of inflammation. Over time, the inflammation produces a build-up of scar tissue that blocks lymphatic vessels and produces dramatic and disabling swelling and open sores in the lower legs.

Mysterious outbreak of disfiguring tropical disease in western Uganda linked to decades of walking barefoot in volcanic soils | EurekAlert! Science News

Microorganisms may be drawn to electrons that biochar can transport.

Microorganisms need electrons for everything they do. If they consume nutrients or spew out methane or expel carbon dioxide – for any living, biological process – they need electrons.

Amending the soil with pyrogenic carbon – known as biochar – brings high definition to the electron network. In turn, the electrons spur conductive networks and growth.

Lehmann and the members of his laboratory had struggled to understand why microorganisms thrived in the presence of biochar. The group removed soil phosphorus, making the environment inhospitable. They ruled out water and nutrients. They discarded the use of biochar as a food source because microorganisms cannot consume much of it. Through Sun’s background in environmental chemistry, the scientists found that microorganisms may be drawn to electrons that the biochar can transport.

Biochar provides high-definition electron pathways in soil

Other research has shown that long-term ecosystem succession is caused by an increase in the connectivity of the ecosystem, and as carbon builds in soils this aids that process.

Fine Root Soil Building

Fine roots with high specific root length drive long-term carbon sequestration deep in the soil profile, so I was interested to learn the following from a new paywalled paper.

  • Higher temperatures make roots shorter and thicker
  • Higher rainfall reduces root nitrogen concentration
  • Soil bulk density influences morphology and favours thicker, denser, fine-roots
  • Herbaceous roots are finer and longer than woody species and fix more nitrogen

Climate, soil and plant functional types as drivers of global fine-root trait variation

Supplemental pages also show a species graph that I don’t yet quite understand scale wise. I just assume for long fine roots we want a large white circle (fine?) for mean root diameter (MRD) and a large black (long?) one for specific root length (SRL). Also White (low?) root tissue density (RTD) and Black (high?) root nitrogen concentration (RNC). Fabaceae have very black RNC, but there are blacker. 🙂


or WHITE, WHITE, WHITE, BLACK if you only care about building the topsoil.

root trait.png