Sunflowers and rapeseed can supply biodiesel feedstock, but on the corpus’s own hand-worked yields a hectare of sunflowers gives about 122-426 litres of pressed oil, not the parent’s 400-600, so a generator burning 2,920 litres a year needs 6.9-24 hectares rather than 5-7. That is land that could instead feed roughly 6-12 people per hectare as corn, so oilseed biodiesel is a luxury of a well-fed community.
Part of Biodiesel Production
Oilseed crops are plants grown for their oil-rich seeds; this covers their oil content, realistic hand-worked yields and what the land and seed would otherwise supply.
The Parent’s Figures
Per the parent: sunflower seed is 40-50% oil by weight and yields 400-600 litres of oil per hectare; rapeseed or canola is 38-44% oil, cold-tolerant, 500-700 litres per hectare; soybean is only 18-20% oil, but fixes nitrogen; flax is 35-45%. The corpus’s other oil pages give sunflower as 35-45% (Oil Extraction) and 40-50% (Plant Oils), so treat 35-50% as the range.
Rebuilding The Yield From The Corpus’s Own Inputs
Three inputs, each from a corpus page:
- Seed per hectare. The caloric guide’s non-industrial figure for sunflower is 500-1,000 lb per acre (Crop Calorie Yields Per Acre). The row is labelled “(oil)” but its 2,620 kcal per lb is 5.8 kcal per gram, the energy of seed; oil is 9 kcal per gram. So this page reads it as seed. Converting (1 lb/acre = 1.1209 kg/ha): 560-1,121 kg/ha.
- Oil content: 40-50% (parent).
- Hand-press recovery: 50-70% of the oil in the seed (Oil Extraction); screw presses 55-70% (Seed Pressing). The plant-oils page says 75-85% for a screw press, which disagrees with those two; the lower figures are used here.
Low case: 560 kg × 0.40 × 0.50 = 112 kg of oil. High case: 1,121 kg × 0.50 × 0.70 = 392 kg. At 0.92 kg/L (assumed) that is 112 ÷ 0.92 = 122 L/ha and 392 ÷ 0.92 = 426 L/ha. The parent’s 400-600 L needs 1,050 to 1,750 kg of seed per hectare at 45-50% oil and 70% recovery, above the corpus’s own hand-worked 500-1,000 lb per acre, or a better press (at 85% recovery the top case is 517 L).
The generator in the parent runs 2 litres an hour for 4 hours a day: 8 L × 365 = 2,920 litres a year. Land needed: 2,920 ÷ 600 = 4.9 ha and 2,920 ÷ 400 = 7.3 ha on the parent’s yield (it says 5-7), but 2,920 ÷ 426 = 6.9 ha to 2,920 ÷ 122 = 24 ha on the corpus’s hand-worked figures.
What That Land Is No Longer Doing
- As corn: the same land at the corpus’s hand-worked yields feeds 6.0-12.0 person-years per hectare, roughly 6-12 people (Yield per Hectare Comparison), so 6.9 ha is at least 6.9 × 6.0 = 41 and 24 ha is up to 24 × 12.0 = 288 person-years of food energy a year.
- As sunflower food: the oil itself is 112-392 kg × 9,000 kcal/kg = 1.0-3.5 million kcal per hectare, 1.0-3.5 person-years at 2,800 kcal a day, less than the corn.
- What comes back: the press cake keeps the protein. From 560-1,121 kg of seed less 112-392 kg of oil, about 448-729 kg of cake per hectare remains for livestock feed (some residual oil included).
What You Need
- Seed crop and land, and a press that gets 50-70% of the oil (Seed Pressing; the screw-press force arithmetic is in Press Construction, written for a printing press)
- A way to dry and clean the seed, because wet seed moulds
- The parent’s claim that the press needs 200 kg/cm² or more. Check it: the corpus’s lever press at 6:1 with 20 kg of rock gives 120 kg of force (Seed Pressing), which over a 15 cm diameter basket (177 cm²) is 0.7 kg/cm², far below 200, yet the same page reports 45-60% recovery from it. A screw press is different: a 100 cm lever and 1 cm pitch turn a 20 kg pull into over 12,000 kg of force (Press Construction, before friction), which over a 10 cm piston (78.5 cm²) is 153 kg/cm², and reaches 200 kg/cm² only on a basket of about 60 cm² or less. So 200 kg/cm² is out of reach for a lever press and marginal for a screw press, and the corpus’s recovery figures (45-70%) are given with no pressure, so they neither support nor need the 200 kg/cm² figure.
Common Mistakes
- Planning from litres per hectare without weighing your own seed.
- Counting the oil but not the land. The seed is the crop; the question is what else the hectare could have grown.
- Skipping the cake. Feeding it back recovers some of the cost.
Pressing, drying and dust
Presses store energy and can crush hands; the seed dust is combustible, and press cake can heat itself if stored damp. Keep the press guarded, dry seed before storage and stack cake loosely and dry.
What’s Next
- Learn next: Production Process, turning the pressed oil into fuel
- Combine with: Caloric Budget for a Community, to see whether the land can be spared