Flame Cap Kiln Char Analysis

Biochar researcher John McDonald-Wharry put out a call for char samples a few months ago. I was curious about my cone kiln char, so I shipped a small bit of char out to New Zealand, and John ran it through his Raman Spectroscopy analyzer (see how casually I mentioned that, as if I know what the heck that is!). Here is the note he sent me today, with the results of his analysis:

Kia ora,

I have attached the provisional Raman results for the char sample you sent in. I am in the process of writing a paper on the around 40 samples which were contributed to this Raman survey.

Your sample was well-carbonised in the top 3 of 40 in terms of our measurements of nanostructural development with results similar to our laboratory produced chars at HTTs between 700 and 1000 degrees C. I am impressed with how consistently well-carbonised this sample was with the results indicating a low level of variability with the sample.

I will send out copies of the paper manuscript once it is near completion to the contributors which should help with interpreting results and allow comparisons with a wide range of other chars (and a few other carbonaceous materials).

Thanks,

John McDonald-Wharry

 

This result is very interesting to me. I don't own any thermocouples, so my only way of measuring the temperature of my cone kiln was to use a cheap infrared thermometer on the side of the kiln. I knew it must be hotter than the 350 degrees C I could measure on the outside metal of the kiln, but I had no idea it could get up to between 700 and 1000 degrees C! Time to get some thermocouples and check it out. 

 

The other surprise is what John said about consistency in the sample. I took the sample - just a few grams - from a barrel of char that was made in the pyramid kiln. The char had gone through the leaf shredder, so it was pretty well mixed. Maybe it was just luck, but I am surprised that it was so uniform.

 

Anyway, here are the results that John sent me: Download Raman Report August2014 (Cone kiln)

You are welcome to check them out.

 

And here is what Wikipedia says about Raman spectroscopy:

 

Raman spectroscopy (/ˈrɑːmən/; named after Sir C. V. Raman) is a spectroscopic technique used to observe vibrational, rotational, and other low-frequency modes in a system.^[1] It relies on inelastic scattering, or Raman scattering, of monochromatic light, usually from a laser in the visible, near infrared, or near ultraviolet range. The laser light interacts with molecular vibrations, phonons or other excitations in the system, resulting in the energy of the laser photons being shifted up or down. The shift in energy gives information about the vibrational modes in the system. Infrared spectroscopy yields similar, but complementary, information.