For the same reasons plants and plant waste can be used to make feedstock for synfuel production, solid waste can also feed the process. Usable solid waste includes old tires, sewage and waste from landfills [source: Speight]. As long as it contains organic matter (and high levels of carbon), it can be used to create some form of fuel. Waste used for feedstock undergoes the same process as other synfuel feedstocks. It is burned under special conditions to produce syngas, which then goes through the Fischer-Tropsch process to be synthesized into liquid fuel. As an alternative, the gas that landfills naturally emit as waste decomposes can be used to produce synthetic fuel.