Chinese euphorb oils ain't oils

As someone who will brake for algae (the words on the bumper sticker on one of my previous cars), I am ready to be convinced algae can solve all the world's problems. Luckily that is balanced by my inherent pragmatism and scepticism, so I know they can't. Some, but not all.

Plants - the mostly green things that evolved from one of the algal lineages - may be able to fill in the gaps. Both algae and plants have been mooted as sources of biofuels. I've posted on algal biofuels before, reporting that an area the size of Portugal would have to be covered in algal farms to provide enough biofuel to run land transport across Europe. I also took a deep dive into some of the methods for extracting oils from algae, in a report from an algal conference held in the UK back in 2012.

Today I want to balance the algae-plant ledger a little by talking about two 'euphorbs' I happened upon during my last visit to China, in December. I was at the South China Botanical Garden, where I saw an ornamental specimen of the West Indian Jatropha integerrima (labelled as Jatropha pandurifolia), and at one of their field stations, at Dinghushan, when a colleague pointed out the local Cleidiocarpon cavaleriei to me.

The spurge family, Euphorbiaceae, often recognisable by its milky white sap, is a good source of oil. As I noted a few year's ago, the common garden plant Euphorbia rigida has been tested in biofuel trials.The two plants I encountered in China are potentially or actually valuable as a source of biofuel. Sort of.

The Jatropha species I photographed (above) is grown for its attractive flowers, remeniscent of cherry blossom; its Chinese common name is Ri Ri Ying, which translates (according to the nearby sign) as Every-day-flowered Cherry Blossom. In English is it sometimes called Peregrina, as are other euphorbs, or Spicy Jatropha (noting that this is a very poisonous plant so do not eat any of it).

The oil in this plastic bottle at the top of the post is from Jatropha curcas, extracted by researchers at the South China Botanical Garden. That species is already the source of biofuel in a range of pilot programs for cars and planes, but the environmental and community costs of producing jatropha oil in commercially viable quantities as a crude oil replacement are considerable.

Researchers at South China Botanical Garden continue to work on the genetics and extraction of high grade oil from Jatropha curcas, while enjoying the aesthetics of Jatropha integerrima in the landscape outside the laboratories.

My other oil-bearing plant, Cleidiocarpon cavalerieri, is native to southern China but not Guangzhou. This large specimen (below) was planted behind a temple at Dinghushan. It comes from a little west of there, the Guangzi and neighbouring regions through to Vietnam.

My photographs are of fruits and leaves at the top of the tree, so I wasn't able to examine them close up. The fruits look a little like stunted legume pods, but they are technically drupes (stone fruits).

The flowers, which I didn't see, are massed together (separate male and female flowers, as in all euphorbs) and look a little like a wattle blossom.

Mapping the chloroplast genome (which I can't resist including here, from a 2012 paper by Gui-Liang Xin and co-authors from Xi'an), supports a close relationship between this species and another oily plant, Ricinus communis, the Caster Oil Plant.

Unlike the Caster Oil Plant, and at least some of the Jatropha oil plants, oil from Cleidiocarpon cavalerieri is reputedly edible. It is also less widely available and grown at the moment, so you are unlikely to encounter it in your travels unless you visit this part of the world.

Note: the title will be obscure to all but older English-speaking Australians, who may recall the advertising campaign by Castrol, trying to make the point that not all oils are same. Which they are not.