The document describes biochar trials conducted in 2013 by the Kerr Center to determine how biochar made from different feedstocks affects soil organic matter content. Samples of biochar made from various plant materials like pine needles, corn, and okra were mixed with sand in individual cups. The mixtures were analyzed at a lab to measure their organic matter content. A separate trial sent bulk biochar pieces to a lab to compare how long biochars from different sources persist in soil before breaking down. The goal was to identify the best feedstocks for making biochar to amend soils.

1. BIOCHAR TRIALS 2013

2. The Kerr Center makes and uses biochar as a
soil amendment; it acts roughly like soil
organic matter in holding water and nutrients.
Two­barrel nested
biochar retort ­
click here to learn
how to make and
use one.

3. We wanted to know how biochar
made from different feedstocks
affects soil organic matter content.

4. We compared eight different feedstocks ­
of which pine needles, pine slash, and
hardwood branches are shown here.

5. Intern Jon Pollnow checking a fresh batch of
biochar. The scrapwood in the foreground is
used for fuel.

6. Jon Pollnow taking samples from
a fresh batch of biochar

7. A fresh batch of biochar

8. Another fresh batch of biochar

9. We used sand (storebought for uniformity)
as the soil medium, due to its low nutrient and
organic matter content.
We oven­dried it to calculate its bulk density,
in order to know how much biochar to add.

10. The dry sand's density was 1.47 grams per
cubic centimeter, in the range of very
coarse sand.

11. Each cup holds 16 oz. of storebought sand,
enough for a standard soil sample.

12. Each cup of sand receives an addition
of 1.9 grams of biochar (roughly
equivalent to 10,000 lbs. per acre).

13. Each cup received an addition biochar from a
different feedstock, including okra...

14. ...corn...

15. ...peanuts...

16. ...sunflower...

17. ...pine needles...

18. ...pine slash...

19. ...hardwood...

20. ...and office paper.

21. The biochar was ground in glass jars
using the butt of a garden trowel.

22. The ground biochar was sieved to exclude
any pieces larger than 1 mm.

23. Sieved biochar is in the white tray at right.

24. 1.9 grams of this material is added
to each cup of sand.

25. Checking the density of a random biochar
sample, to visually gauge how much a given
amount of biochar might weigh.

26. Each ground, sifted biochar sample has
the same weight as all the others...

27. ...illustrating the difference in density between
biochars made from the different feedstocks.

28. Each biochar sample is thoroughly
mixed with sand...

29. ...creating a marked color change
compared to sand alone.

30. Each combined biochar/sand sample is
individually bagged...

31. ...and sent to a professional lab to be
analyzed for soil organic matter content.

32. In a separate trial, bulk biochar
pieces were sent to a different lab...

33. ...to compare the length of time that
biochars from the different feedstocks will
persist in the soil before breaking down.

34. Results:
Feedstock Guide for a Two-Barrel Nested
Biochar Retort
Biochar Feedstock Research Using a Two-
Barrel Nested Retort
The Effects of Added Mineral Salts on
Biochar Yield Using a Two-Barrel Nested
Retort