As you know, the world is running out of fossil fuels, that is, crude oil, coal and natural gas.
As an alternative, certain plants are now being considered as biofuels, which are fuels made from organic plant material.
These are possible sources of energy once the fossil fuels have gone forever.
Well, one such plant goes by the name of Jatropha.
It was first a native of Central America and it's now found across the world.
A few things that make this plant especially attractive is that it can survive in very poor quality infertile soil, as it does, for example, alongside train tracks in India on the line between Mumbai and Delhi.
And for up to three years it's resistant to drought.
That's right, it can do without rain for that long.
And even if it's not actually a plant that people can eat, it's still worth having it on your land as it prevents erosion.
And we looked at the dangerous consequences of that in a previous lecture.
Furthermore, Jatropha seeds can be slowly distilled to produce diesel oil, and it's this kind of fuel, of course, that's of interest to scientists and power companies.
After processing, the seeds can yield up to four times the oil that soybean can, and ten times the amount compared to corn.
So you can see why it's causing such interest.
And not much is wasted in the processing procedure either.
After the oil has been extracted from the seeds, the residue is processed into biomass which can run power stations, which in turn can provide electricity for thousands of local homes.
Also, whereas our fossil fuels cannot be replaced, the energy produced by biofuels such as Jatropha is renewable.
It's not going to run out because the plants just go on growing.
There's no doubt that it is a remarkable plant, and one that has been very beneficial to man.
In various African communities, it's been used to operate water pumps and refrigerate medicines.
It can be used to produce candles, or as a fencing plant to keep some animals enclosed, and some animals out.
It can also treat a number of health problems.
For example, the boiled leaves can do much to relieve the suffering of people with malaria.
And some Jatropha species have seeds which are used to treat digestion problems.
Anyway, that's not what the European corporations who are buying vast amounts of land for Jatropha plantations are focusing on.
They claim that people who are dependent on rural economies will benefit from growing Jatropha, and that it will help them bring an end to poverty by providing a long-term local industry.
They also point out that few or no modifications would be necessary in modern diesel engines since they were originally designed to run on biofuels such as peanut oil and ethanol anyway.
Of course, when the plants are burnt, they release carbon dioxide, but they absorb great amounts when they're growing, making them a considerably greener alternative to fossil fuels.
But not everyone shares the excitement over Jatropha, nor other biofuels.
In Western Australia, Jatropha has in fact been banned since the seeds of some species are toxic, and it only takes three or four to kill a person.
And animals are also very vulnerable.
Furthermore, sceptics also point out that as there are many species of Jatropha, its oil productivity is unreliable.
Aside from this, critics of Jatropha and other biofuels claim that farmers now have a strong economic incentive to grow them rather than food crops.
Poor countries would be particularly affected because they would have to rely on imported foods to survive, and people would end up having to pay greatly inflated prices for basic foods.
There's also the concern over environmental damage.
In order to provide land for palm oil or sugarcane plantations, for instance, companies are cutting down vast areas of rainforest which can never be replaced, and this in turn results in the disappearance of wildlife which depended on that habitat.
You can also imagine that such deforestation makes a considerable contribution to global warming.
Furthermore, opponents also reject the idea that biofuels are a carbon-neutral source of energy.
