This past
weekend was a busy one at the Sebastopol
Demonstration Energy
Garden. After a summer of
soaking in sun and filling their stalks and seeds with sugars and starches, our
Dale Sorghum crops went full cycle. From the 212 sq ft. that we had under cultivation
we harvested 9 kg of dry seed and 115kg of sugar rich stalks. From the stalks
that we harvested in addition to the 110 kg of stalk that were donated to us by
Live Power farms (225 kg in total), we produced 10 gallons of sorghum juice. Of
the 10 gallons produced, we fermented 8 gallons and with the other two produced
approximately 57 oz of sweet sorghum syrup; this demonstrates the multiple
possibilities that the crop offers. In addition we were able to utilize the
carbon in the pressed stalks by adding what we didn’t use as a layer in our
sheet mulch as an ingredient to our compost piles. The chickens quickly
consumed the fresh leaves that topped each pile.

It took three
of us approximately three hours on Friday to harvest the stalks and seeds; this
includes removing the leaves from the stalks. The process entailed one man
cutting the stalks at their base with a pair of hand held clippers while
another tied the stalks in bundles and removed the seeded florets which were
processed by a third. The seeds were separated and laid thin upon screens in
the sun to be dehydrated and the stalks were stacked in the shade to be pressed
the next day.

To press the
stalks it required three people an additional 3.5 hours of labor on Saturday. We
used the Improved Chattanooga #12 to press the stalks and caught the juice in 5
gallon buckets; the juice that emerged was a pea green and contained 15% sugar
by volume. By comparing the measured weights (lbs) of bundles of four stalks
with the volume (mL) of liquid that emerged we determined that on average 162.3
ml of juice is produced for every 1 kg of stalk pressed.

Overall
harvesting and processing the stalks required about 21 hours of labor. We
produced 10 gallons at 15% sugar from the 225 kg of stalk that we pressed
giving us a 22.5:1 ratio of kilograms of stalk for each gallon of juice
produced.

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Data published
in the Alternative Field Crops Manual reports yields of 10 ton/acre for Dale
Sorghum, of which 70% is comprised of the stalk. This is synonymous to 6350.3 kg of
stalk/acre, which would indicate that 282.24 gallons could be achieved for each
acre of Dale Sorghum under cultivation. Seeing that the juice produced from
pressing the stalks is 15% sugar, fermentation should yield 282.24 gallons of mash
at 7.5% alcohol. This shows that from one acre of Dale Sorghum, 21.17 gallons of
200 proof ethanol can be produced; the theoretical yield that they indicate however is over 400 gallons/acre.

Data published by Morris J. Bitzer
at Blairsville, GA, and Quicksand, KY shows yields of Dale Sorghum at
20 tons of stalk/acre, 20321.28 kg stalk/acre, double the yield
proposed by the Alternative Field Crops Manual, whose data was compiled
from Waseca, MN.

Data published by Oak Ridge National Labratory, acquired from 4 different test sites in Indiana and Alabama, reported yields of 22.2 Mg/ha (9.9 tons/acre), similar to that published by Alternative Field Crops Manual.

Data Published by Texas A&M Extension agronomist, Juerg Blumenthal said the highest yield he'd acheived was 12.4 tons of dry
matter per acre with the production of 395 gallons of ethanol per acre.

No indication of the
proof of alcohol produced was provided in any of these studies, but I
do not see how it is possible to yield such high volumes per acre. In each case either the juice pressed from the stalks is of a higher
sugar percentage, their method of pressing is more
efficient, or the sorghum is being grown in higher densities; none of
this information was provided. Somehow, in each case, higher volumes of
ethanol per acre were produced from lower masses of stalks per acre

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Proposed yields of sorghum stalk/acre: 10 ton/acre, 12.4 ton/acre, 22.2 Mg/ha (9.9 tons/acre), 20 ton/acre

Average = 13.075 ton per acre

1 acre = 43559.46 sqft

Harvested 212 sq ft = 0.005 acre

0.005 * 13.075 = 0.065 ton/acre

1 ton = 907 kg

Harvested 115 kg stalk = 0.127 ton stalk/0.005 acre = 25.4 ton stalk/acre

*25.4 tons stalk/acre being grown on site > 13.075 ton/acre proposed yield

Proposed yields of ethanol/acre: 400 gallons of ethanol/acre, 395 gallons

Average = 397.5 gallons ethanol/acre

Produced 10 gallon juice from 225kg stalk, of which 115 were grown on site

115/225 = 0.51 * 10= 5.1 gallons juice produced from grown sorghum

1 acre/0.005 acre = 200 * 5.1 gallons of juice produced = 1020 gallons of juice/acre

15% sugar will ferment to 7.5% ethanol

1020 gallon juice/acre * 7.5% ethanol after fermentation = 76.5 gallons ethanol/acre

*76.5 gallon of ethanol/acre produced < 397.5 gallon ethanol/acre proposed. This data correlates more with the projected 21.17 gallons of ethanol/acre that I proposed based on the obtained 22.5 kg stalk:gallon juice ratio and the assumption that starting with a 15% sugar content will produce a 7.5% alcoholic mash after fermentation.

My name is Michael Bomford. I work for the Community Research Service at Kentucky State University, an historically black land grant university in Frankfort, Kentucky's capitol city. My research focuses on developing sustainable organic agriculture systems suitable for adoption by small farmers. Check out some of the projects I'm working on here.

KSU energy farm project, with food crops (foreground),
high tunnel, and energy crops (background).

1. 1. Biointensive - using human labor and hand tools in small beds, according to the methods of John Jeavons
2. 2. Market garden - using no machinery larger than a walk-behind tractor in medium-sized beds
3. 3. Small farm - using standard four-wheeled tractors for crop production at the field scale.

Due to the apple press' limited ability, we constructed a much more sophisticated tool to aid in our goal of fermenting fallen apples as a means of producing ethanol.

It functions as both a grinder and a press and we were able to construct it out of basic hardware, including parts from the previous apple press (all lumber used was recylced).

The grinding mechanism was built using 3/4" steel nipples attatched to a 5" in diameter cut of fir. Screws were then distributed around the circumfrance of the wood to act as the teeth of the grinder.

The grinder was mounted by drilling 1 1/2" holes through the diagonal support beams that connect the leg posts and a handle was added for easy torque. We then added a funnel to hold the apples to be ground and added horizontally placed 2x4s to support the press.

The construction of the press was more demanding because it required that the platform be waterproof and that we provided a faucet of some sort to dirrect the pressed liquid. The platform that we made was first caulked with silicone to avoid any leaks and then coated with a sheet of galvanized steel. The faucet was made from PVC parts left over from the drip irrigation system and was installed just as the grinder was, by drilling a 1 1/2" hole within which it rested. Silicon was also used to make sure no liquid escaped around the sides of the faucet.

We are able to easily remove the press and fill/empty the contents because rather than permanently attatching its parts, they are simply clamped down before and after each pressing.

With one person opperating the machine, we are able to produce 4 gallons of liquid per hour; this includes collecting the apples, grinding them, and pressing them.

After producing eigh gallons of wort, measurements of the temperature, the sugar content, and the pH were taken.

A pH of 3.5 was measured at 78 degrees farenheit with a sugar content of 12% prior to bringing the wort to a boil.

The wort was then poured into a stainless steel kettle, and brought to a boil so as to kill any bacteria that might compete with the yeast we would soon add. By doing so we were also boiling out water, hence increasing the sugar content as well as neutralizing the pH.

After boiling the wort and allowing it to cool, yeast nutrients were added and measurements were once again taken. As the temperature of the wort cooled, the hydrometer's reading of the sugar content became more accurate. I was able to boil out enough water to bring the sugar content to 20% and the pH to 4.5. The sugar content could have even been higher and this has been noted for the next batch.

Once a temperature of 80 degrees farenheit was reached, the yeast was added, the lid was put on the bucket and the bucket was placed in a cool place to ferment for the next three days.