a filtration system that uses a filter to convert wastes in automotive exhausts into carbon nanotubes is disclosed . metallic salts , such as iron salts , may be mixed with diesel fuel by way of using algal biodiesel to ensure homogenous suspension of the metallic salts in the diesel fuel . the metallic salts form a suitable catalyst to grow carbon nanotubes on a filter placed in the pathway of the diesel combustion exhaust . the filter surface may be composed of iron of similar catalyst . the filter may be placed along the pathway of exhaust streamlines preferably at an angle of more than 5 degrees and less than 15 degrees . the filter is heated to temperatures in the range of 200 - 1000 degrees celsius . the filter described in this invention can work in its own or supplement existing filtration systems . the filtration system may produce a material that is commercially valuable , synthesized carbon nanotubes .