Converting Trash to Energy

Tomorrow's household garbage might be blended with after-harvest leftovers from fields, orchards, and vineyards to make ethanol and other kinds of bioenergy.  Agricultural Research Service (ARS) scientists are investigating the straightforward, eco-friendly strategy in their laboratories at the agency's Western Regional Research Center in Albany, Calif.

In most cases, wastes like rice straw, almond hulls, and the oversize outer leaves of iceberg lettuce will have to be pretreated before being used as a bioenergy resource.  The garbage, known as "municipal solid waste," or "MSW," would also be pretreated.

The garbage would be processed in a jumbo-size autoclave, a device which acts something like a giant pressure cooker to convert the MSW into grey, lightweight clumps.  The pretreated agricultural wastes and autoclaved MSW would then be transferred to a biofermenter.  Yeasts and enzymes would be added to make ethanol.

Scientists are determining the best ways to use just water and heat, instead of hazardous chemicals, to pretreat the farm wastes, thus keeping the biorefining process environmentally friendly.  Besides producing biofuels, the biorefinery would also reduce the volume at landfills and minimize the need for new ones.