(since the intensive husbandry is limited to the first few years of their producing lives) and can provide cash-crops to rural areas, such as rural India. In the case of Millettia Pinnata and a few others, the fact that they are nitrogen-fixing legumes is another very important factor, in that they do not deplete the soil. Among other benefits of these trees is that they have root-systems that penetrate much deeper and do not compete with shallow-rooted plants, like grass (once the trees have attained a certain maturity). This means that the land can be used for multiple purposes, such as grazing for animals. Yet another benefit of using Millettia Pinnata to produce bio-diesel is that it can tolerate low rainfall (as little as 250 ml per year), far below what most food-crops require, thus reducing yet more their potential to compete. Algae for vegetable oil production Some species of algae contain as much as 50% vegetable oil. Algae have very high growth rates compared to plants normally used to produce vegetable oil. Potentially algae could produce much more oil per area of land than current farming methods. So producing vegetable oil this way should result in less deforestation and less competition for food production land. Yusuf Chisti of the Institute of Technology and Engineering at Massey University states, "As demonstrated here, microalgal biodiesel is technically feasible. It is the only renewable biodiesel that can potentially completely displace liquid fuels derived from petroleum. Economics of producing microalgal biodiesel need to improve substantially to make it competitive with petrodiesel, but the level of improvement necessary appears to be attainable." Where there is existing electricity generation using fossil fuels, there is a source of sterile CO2. This makes algaculture much easier. To grow algae you need lots of CO2, but if you get it from air you will also get all kinds of other organisms, some of which eat algae. Getting CO2 from a smokestack works out really well. Governments trying to address the external costs of coal power plants may have a carbon tax or carbon credit that provides additional motivation to use CO2 from smokestacks. Several commercial pilot plants are under construction. There is substantial research and development work in this area but as of 2007 there is no commercial vegetable oil produced from algae and used as biofuel. ExxonMobil is investing $600 million and estimates they are 5 to