Sugar crops are the easiest ethanol feedstock because their sugar is already fermentable: crush or press the fruit, cane or beet, ferment the juice, and expect roughly 70-80 litres of ethanol per tonne of sugarcane, 80-100 per tonne of sugar beet and 60-70 per tonne of apples. The sugar that makes the fuel is the same sugar a community would otherwise use to preserve fruit and sweeten food, so fuel from a sugar crop is only justified from waste or surplus.
Part of Ethanol Fuel Production
Fruit, cane, beets and sweet sorghum as ethanol feedstocks: how the sugar is released, how much fuel it gives and what it competes with.
Sugar Crops Skip The Conversion Step Starch Needs
Table sugar (sucrose) is split by yeast’s own enzymes into glucose and fructose, so no malt and no cooking are needed. The work is releasing the juice.
- Fruit: crush and ferment, skins included; wild fruit costs nothing but picking (Fruit Mash).
- Sugarcane: roller-press the stalks; needs a tropical or subtropical climate.
- Sugar beet: shred or slice and extract with hot water or press (Sugar Beet Processing); roots hold 12-20% sucrose by weight per that guide.
- Sweet sorghum: press the stalks like cane (Sweet Sorghum Cultivation).
Check The Table Against The Chemistry
Fermentation turns sugar into ethanol at best 0.511 kg per kg of glucose (2 × 46.07 ÷ 180.16), and 0.538 kg per kg of sucrose (4 × 46.07 ÷ 342.30). The yeast also uses some sugar to grow, so a working figure is about 95% of that (Pasteur’s classic figure is 48.4 g of ethanol per 100 g of glucose, 48.4 ÷ 51.14 = 94.6% of the ideal). Working back from the parent’s litres per tonne, with ethanol at 0.789 kg/L:
| Feedstock | Litres/tonne | Ethanol kg/t | Sugar needed at 95% (kg/t) | As % of weight |
|---|---|---|---|---|
| Sugarcane | 70-80 | 55-63 | 108-123 | 10.8-12.3% |
| Sugar beet | 80-100 | 63-79 | 123-154 | 12.3-15.4% |
| Apples | 60-70 | 47-55 | 93-108 | 9.3-10.8% |
Each row needs about 9-15% fermentable sugar by weight, which is within what these crops hold, so the table is consistent. (Beets at 12-20% sucrose could in theory give more, 82-136 L/t at 100% conversion; the table keeps to what extraction and fermentation losses leave.)
What The Land And The Sugar Are No Longer Doing
The parent’s per-hectare figures (cane 6,000-8,000 L, beet 5,000-6,500 L) come from mechanised yields of 75-114 t/ha for cane and 50-81 t/ha for beet. The corpus’s own sugar guide gives 15-25 short tons of beets per acre, which is 33.6-56.0 tonnes per hectare, and warns that its beet figures do not all fit together (Growing Sugar Beets at Scale). At 33.6-56.0 t/ha and the parent’s 80-100 L/t, a hectare of beets would give 2,690-5,600 litres.
Against that: the same hectare under hand-worked potatoes or corn feeds about 6-13 people for a year (6.8-12.7 and 6.0-12.0 person-years at 2,800 kcal a day; Crop Calorie Yields Per Acre). Sugar is not a balanced diet, but a community that makes ethanol from beets has chosen to give up that land’s food and its sweetener supply, which the sugar guide uses for preserving fruit and morale (Sugar Production & Sweetener Sourcing).
Method: Prepare A Sugar Wash
Step 1: Release the sugar. Crush fruit to a pulp, press cane or sorghum, or extract beets in hot water. Strain out coarse solids.
Step 2: Adjust strength. Aim for 15-20% sugar by weight (a hydrometer reads this; see Monitoring & Troubleshooting). Dilute with water if stronger, because a very sugary wash stresses yeast.
Step 3: Cool and pitch. Bring to 25-35°C and add yeast (Yeast Selection & Propagation).
Common Mistakes
- Fermenting juice that has already started to ferment wild. Wild yeast usually stops at 5-8% alcohol and can sour; press and pitch the same day.
- Counting the table’s tonnage as your own. Weigh what a plot actually yields before planning litres.
What’s Next
- Learn next: Starch Crops, the feedstocks that need a conversion step
- Combine with: Fermentation, which takes the wash from here