The United States Environmental Protection Agency and the State of Hawaii have launched a project to turn human waste products into paving asphalt and to extract useful fuel oil in the process. The project will work with sludge from sewage processing plants. Sewage sludge is on organic material containing a large variety of carbon-based molecules. Researchers hope to develop an economical means of converting organic sludge to hydrocarbon chains of various sizes, mostly of the kind that make up asphalt that is used for paving roads. A by-product would be synthetic oil. Hawaii currently must import large quantities of expensive heavy petroleum in order to make all its paving asphalt. By using sewage, the state government believes it can save a great deal of money on road pavement while solving some environmental problems. What will be the source of the raw material for the project discussed in the passage?