Retted Switchgrass Fireballs

Retted Switchgrass Fireballs
Jeff Davis, September 10,2006

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Note: Click on image to enlarge.

These fireballs are made from retted switchgrass with some waste vegtable oil (WVO) added. As can be seen in the above picture they burn well in the inverted down draft gasifier thus the Woodgas Camp Stove.

The non-WVO switchgass fireballs (dry, no oil) did not burn well in this stove. They burned somewhat like charcoal fireballs. First lots of smoke then after the smoke cleared there was the charcoal like glow for about ten minutes. This smokey burn can be seen in picture 1. Also, they did not put out much heat. This provoked me to explore enriching them with WVO. Picture 11 shows a WVO enriched fireball (left) and a dry fireball (right).

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My WVO is not exactly WVO, its stale cooking oil that I had for a few years. It might be corn oil, the label fell off some time ago. But in this article I refer to it as WVO.

Below in table 3 you will find the data concerning the burn/boil test. Also, in picture 7 you can see the boiling. Picture 2 is the fuel.

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Table 3
fuel (oiled) 287.9g
water @ start 800g
water remaining after boil 126.1g
water boiled away 673.9g
start to boil ~ 4 min.
boil time ~ 19 min.
flame time ~ 24 min.
charcoal glow after flame ~ 10 min.
ash 104.7g



Picture 3, 4, 5 and 6 are all shots of the burn.

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Below in pictures 9 and 10 you will see the 10 minutes of charcoal like burn and the remaining ash, in that order.

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I made one major mistake. I forgot to measure how much the fuel weighed before the oil was added. I think I dipped the original batch of fireballs twice. So I repeated the oil dipping, plus more dippings and weighings. This information can be seen in table 2 below.

Table 2
Woodgas Camp Stove Charge
Description Fiber + Oil Total Oil Oil ea. Dipping
dry 198.7g 0 0
1st oil dipping 256.5g 57.8g 57.8g
2nd oil dipping 304.7g 106g 48.2g
3rd oil dipping 329.6g 130.9g 24.9g


Picture 12 shows the stove filled with this new oiled dipped fireballs. This is to prove that they do not expand when the oil is added. If anything they may have shrunk but I can not see this as being possible.

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I measured the angle of repose with the tube shown in picture 13 and the results can be seen in picture 14 and table 1

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Table 1
Description Value
angle of repose ~20%
bulk density [1] dry 354.4g / liter
dry particle density 0.460g / cm^3
oiled (3rd) particle density 0.957g / cm^3




Jeff Davis