| While much of what goes into biodiesel could be | | | | they reduce the volume of the MSW by 90 percent, |
| considered biodegradable waste, the concept | | | | and with 40 million Americans each producing an |
| deserves its own section because of its enormous | | | | average of more than 1,600 pounds a year, that's |
| potential. As we said before, biomass happens. When | | | | important. WTEs can convert a ton of garbage into |
| the quantities were relatively low, few people | | | | 525 kilowatt-hours of electricity (and 300 to 600 |
| considered waste management a problem people | | | | pounds of ash). Today, 14 percent of the MSW in |
| used to burn trash in their back yards, or bury, or | | | | the U.S. get incinerated. |
| put it out for the trash truck without a thought. | | | | But as with landfills. WTEs were not without their |
| Industrialization, population growth, and dozens of | | | | own problems. What remains after incineration is ash, |
| other factors caused the amount of waste produced | | | | and much of it hazardous. High concentrations of the |
| annually to skyrocket, and for a long time everything | | | | metals (e.g., lead, cadmium) in the MSW remain in the |
| got dumped into old mines, quarries and other big | | | | ash, from dyes, inks, batteries, ceramic materials and |
| holes: landfills. | | | | more. Pollutants overall have decreased |
| Soon enough it became apparent that in solving the | | | | substantially-roughly 85 percent overall-since EPA |
| problem of what to do with the waste, other | | | | introduced the Maximum Achievable Control |
| problems had cropped up. Before landfill developers | | | | Technology (MACT) standards in 1995 as part of the |
| thought to line the pits, contaminated water leeched | | | | Clean Air Act. But U.S. facilities combine their fly ash |
| into the aquifers. They attracted rats and other | | | | (airborne) with their cleaner bottom ash, which brings |
| scavengers. "Landfill gas" (methane and CO2) filled | | | | the overall percentages of toxic materials into |
| the air, killing surface vegetation and contributing in a | | | | compliance standards for expanded reuse. |
| major way to greenhouse gases (1.2 tons of CO2 | | | | The newest development is converting the useful |
| per ton of municipal solid waste, or MSW). And, quite | | | | biomass energy stored in MSW to feedstock and |
| simply, they stank. | | | | ethanol in biorefineries. A number of processes are in |
| Still, economics caused most MSW to end up in | | | | the R&D and pilot stages, including one in Texas, |
| landfills. Then huge incineration plants called | | | | that uses a biological/chemical process that |
| waste-to-energy facilities (WTEs) were built to take | | | | anaerobically digests the biomass into liquid |
| care of the problem. They do solve some issues: | | | | mixed-alcohol fuels. |