Researchers in India have suggested that tree seeds, rather than biomass or fuel crop plants, could represent an abundant source of renewable energy. Publishing the results of their study in the International Journal of Automotive Technology and Management, the researchers suggested that seeds from the Indian mahua and sal trees have almost as good a thermal efficiency as biodiesel but would produce lower emissions of carbon monoxide, waste hydrocarbons and nitrogen oxides, all problematic pollutants.

Sukumar Puhan of the GKM College of Engineering and Technology explained how tree seeds represent a vast untapped biomass resource for the production of automotive fuels in India. He said tree seed oils have benefits over vegetable seed oils in that they possess both lower viscosity and greater volatility, which would reduce some negative impacts associated with current biofuels.

Puhan and his colleagues also pointed out that the deciduous mahua (Madhuca indica) and semi-deciduous sal (Shorea robusta) trees provide large amounts of seeds, which are currently "left to waste on the forest floor."

The mahua kernel constitutes 70 percent of the seed and contains 50 percent oil, which can be extracted at levels of 34 to 37 percent, according to the GKM team. Sal can produce about 20 percent oil. The team also successfully tested the biodiesel conversion process for the two trees.

Although neem seeds were also found to be potentially suitable for biodiesel production, Puhan and his team suggested the economics of using this species are "prohibitive, because the tree has greater value for its wood and also has a much longer maturation period than mahua at 25 years."

The team suggested their findings could be put into practice, creating plantations across 15 million hectares of degraded, notified forestland in India "that could be converted to plantation to provide sal and mahua seed in a sustainable fashion as well as generating employment opportunities for a large number of people."

The suggested, "Biodiesel production from tree seeds in India will not only reduce the dependence on crude oil imports, but also reduce the environmental impact of transportation and increase employment opportunities."