New Wonder Weed to Fuel Cars?

Hugh Pickens writes "Jatropha, an ugly, fast-growing and poisonous weed that has been used as a remedy for constipation, may someday power your car. The plant, resilient to pests and resistant to drought, produces seeds with up to 40 per cent oil content that when crushed can be burned in a diesel car while the residue can be processed into biomass for power plants. Although jatropha has been used for decades by farmers in Africa as a living fence because its smell and taste repel grazing animals, the New York Times reports that jatropha may replace biofuels like ethanol that require large amounts of water, fertilizer, and energy, making their environmental benefits limited. Jatropha requires no pesticides, little water other than rain and no fertilizer beyond the nutrient-rich seed cake left after oil is pressed from its nuts. Poor farmers living close to the equator are planting jatropha on millions of acres spurred on by big oil companies like British Petroleum that are investing in jatropha cultivation."

Comments

Some numbers for comparison.

[AnotherBlackHat]

Lex Worrall, chief executive of Helius Energy, claims Jatropha can produce 2.7 tonnes of oil per hectare. http://www.timesonline.co.uk/tol/news/world/article2155351.ece

For comparison, corn produces about 0.15 tonnes per hectare, hemp about 0.30 tonnes, and canola (rapeseed) only 1.0 tonnes.
So if he's right, it's a very good oil producer, on the order of much harder to grow oil producers like avocado (2.2) or coconut (2.3).

Still 1/5 of algae though.

-- Should you believe authority without question?

Re:Just use hemp.

[rossifer]

In the coarsest terms, plants require both bioavailable carbon and bioavailable nitrogen along with a few other nutrients to grow. The atmosphere supplies bioavailable carbon to plants through CO2. But atmospheric nitrogen is not usable by plants. Bioavailable nitrogen must be supplied to plants through their roots, and it doesn't just appear in soil and water. Some nitrogen appears in topsoil, but agriculture will quickly deplete nutrient supplies. If they aren't replaced, you end up with productivity losses, loss of cropland, and in the worst case, desertification.

Means of nutrient replacement:

1. Tilling animal manure into the soil.
2. Tilling composted plant material into the soil.
3. Planting nitrogen fixing plants (peas, beans, etc.) and then tilling them into the soil.
4. Leaving the field fallow (without a crop) for several years (a slower version of (2)).
5. Adding fertilizer

So what this article is claiming is that the seedcake left over from oilpressing contains all of the nitrogen and other nutrients needed to restore the soil using just technique (2). That's an extraordinary claim. This plant is not a legume or one of the other nitrogen fixing plants, so by itself, cannot increase the amount of nitrogen in the soil. Some of the nitrogen will be unusable in the seedcake, some of the nitrogen needed to grow the plant will go into other parts of the plant that will have other economic uses or take too long to compost. A 100% cycle of nitrogen back into the soil would be great, but doesn't make any sense.

As for the sun and water, well, they can only do so much given that neither one is a supply of the nutrients needed to keep the soil healthy.

Regards,
Ross