The fossil fuel crisis arising due to our increased use of oil leading to diminishing oil reserves, is giving rise to an increase in renewable energy generation. While solar and wind are preferred to produce electricity, biodiesel is preferred as a replacement to petrol and diesel. Biodiesels are produced from plant or animal matter, like vegetable oil, animal fat or even waste cooking oil. Although biodiesels still produce exhaust gases, they are much cleaner and safer compared to the toxic fumes coming out of fossil fuel powered engines. Scientists at Indian Institute of Science have been working on improving the efficiency and reducing the exhaust fumes in biodiesel engines. Their latest work looks at reducing the Nitrogen oxide (NO) released from the exhausts of biodiesel engines. While biodiesel produced from pongamia pinnata, a native Indian plant, powered a diesel engine, the scientists injected ozone into the stream of exhaust fumes. By doing so, the high amount of NO in the exhaust gets oxidized or to higher oxides of nitrogen, like Nitrogen Dioxide (NO2). Next, this stream of higher oxides of nitrogen passes through pellets of lignite ash, an industrial waste produced in lignite coal fired power plants, where NO2 is adsorbed by the pellets. The two steps together effectively reduce around 95% of the amount of NO and NO2 in the exhaust. The researchers have also compared other techniques available, such as direct plasma treatment, at removing NOx from the exhaust. While the new method is as efficient as many techniques available today, it also manages to remain economical, with the use of industrial waste material -lignite ash.