One of the properties of biochar that I never gave much thought to until recently is its low thermal conductivity. In fact, I wasn’t even sure what low thermal activity meant in terms of its usefulness for biochar. [Confessions of a non-scientist!] But in just the last week I read two different research papers focused on two completely different end uses for biochar that mentioned it, so I decided it was time to become a little less ignorant on the topic.
The first mention I came across was in a recently translated article on Biochar use as a building material from the Ithaka Institute (full disclosure: I am thrilled to now be working with this organization, but more on that in the future). In this context low thermal conductivity translates to high insulation which is a good thing in the construction industry. All those pockets of air, or pore space within biochar creates a kind of lattice structure that slows down the movement of heat. [Come to think of it slowing down hot air would be really helpful in our current political arena! I’ll have to think how biochar could creatively be used to do that …]
The second mention I found was in a paper called “Biochar in growing media: A sustainability and feasibility assessment” written by some of the gods of biochar research. This paper has some really great info comparing biochar to other growing media, but what caught my eye was this statement: “Charcoal has a heat capacity similar to soil and peat but much lower thermal conductivity that could provide thermal buffering.“ The paper was hypothesizing that this could provide some protection to nursery stock. There has been some intriguing biochar related research on this topic, but not all that much from what I’ve found.
One of the reasons I found this so interesting is that the winter we just experienced in the Finger Lakes was a tad on the brutal side. Very long and very cold. Vineyards suffered and no one is quite sure yet how bad the long term damage will be. This got me wondering if biochar might be able to act as some type of frost buffer for NE vineyards. To be on the safe side many vineyards practice something called ‘hilling up’ in the fall which tills soil up above the graft zone of the vines as a means of protecting them from the cold – some vineyards use straw around the vines as well. In the spring the soil is then ‘hilled down’ to allow air flow around the vines. Given its low thermal conductivity, hilling up with biochar or a biochar + pomace compost could possibly provide a nice thermal blanket which would be tilled down into the soil in the spring. Sadly this year they may end up having to pull out quite a few acres of vines which are often burned to get rid of the biomass. Turning these vines into biochar and then using the char/pomace compost to hill up in the fall might be one way to turn a negative into a positive.
And for NE farmers with annual crops perhaps using biochar might allow seeds to be planted a bit earlier in spring if it helps buffer soil temperatures!
Coming up soon…frost protection techniques are in need of a biochar intervention!