Each day, a parade of trucks heads north out of the Southern California metropolis, grinding over the Tehachapis and descending into Kern County, one of the state's premier agricultural regions. The convoy is nearly a mirror image of the truck traffic heading the other way laden with commodities grown in the fertile Central Valley. There is an important difference, however. Whereas the southbound trucks, bearing oranges, tomatoes, almonds, carrots, cotton and other valued products, are welcomed, the northbound trucks haul a less popular cargo: sewage sludge, the semisolid leftovers of municipal wastewater treatment. This aesthetically unsavory product is a perennial headache for sanitation districts. Yet to farmers trying to coax crops from marginal farmland, sludge is a nutrient-rich resource. And now it is at the heart of a legal and political battle that pits science against popular perception, and the state's rural heartbeat against urban muscle. Technically, "sludge" is organic solids separated from untreated wastewater. The stuff trucked to Kern County from cities throughout Southern California is known more accurately, if less descriptively, as "biosolids" — human and industrial waste that has been filtered from treated wastewater, pumped into tanks and allowed to cook in its own biologically generated heat until bacteria and other pathogens have been neutralized. For decades, sewage plants dumped their sludge in the ocean, buried it in landfills or incinerated it. But regulatory barriers to ocean disposal and burning have made those options unattractive. And high tipping fees at crowded urban landfills have made burying it costly. Searching for a new solution, municipal sanitation districts have in recent years seized on a paradoxically old technique: land application. Essentially, properly treated biosolids are a fertilizer and organic soil amendment, and plowing such waste into cropland to boost fertility has an ancient history. An Environmental Protection Agency guide describes the value of sludge in glowing terms: "Biosolids are, in effect, a slow-release nitrogen fertilizer with low concentrations of other plant nutrients. In addition to significant amounts of nitrogen, biosolids also contain phosphorus, potassium, and essential micronutrients, such as zinc and iron, which are of great benefit in the West, where many soils are deficient in micronutrients. Since biosolids are also rich in organic matter, they can improve soil quality by improving water-holding capacity, soil structure and air and water transport. Proper use of biosolids can ultimately decrease soil erosion." Southern California sanitation districts had little trouble finding receptive farmers in Kern County, which has much land that is fertile but also much that is not. Both varieties are urged into cultivation by inexpensive water. A billion pounds of sludge a year, more than 50 truckloads a day, makes its way to Kern County, where it is spread on land used for such nonfood crops as cotton, sorghum and alfalfa. Thanks to its proximity to Southern California's urban centers, and the convenient access provided by Interstate 5, Kern County has quietly become California's top repository of sludge. Not everyone in Kern County is happy about that. Local environmentalists and health activists, for example, warn that sludge might contain high levels of toxic metals derived from industrial processes, as well as viruses, parasites and other pathogenic organisms that survive processing. The limited research that has been done, however, suggests there is little public health risk. Heavy-metal concentrations in municipal wastewater have been greatly reduced since the 1970s under tough federal and state discharge regulations. A 1996 report by the National Research Council noted, "There have been no reported outbreaks of infectious diseases associated with a population's exposure — either directly or through food consumption pathways — to adequately treated and properly distributed reclaimed water or sludge applied to agricultural land." But an audit of EPA's biosolids management and enforcement, which the U.S. Inspector General's Office released March 20, found that federal regulations governing the land application are adequate. But the Inspector General also concluded that EPA does not collect enough information or conduct enough field inspections to determine whether farmers comply with the law. If the actual public health threat is ambiguous, public attitude is not. "We don't want to be L.A.'s toilet," one Kern County farmer told a newspaper reporter earlier this year. Sensitive about the public image of Kern County agricultural products — particularly high-value specialty crops competing in a cutthroat market — a coalition of growers persuaded the Kern County Board of Supervisors last October to pass an ordinance making it illegal to apply conventional sludge to farmland. The ban would be phased in over three years, after which time only "exceptional quality" biosolids — sludge that has been mixed with other organic matter and composted — could be plowed into the soil. Municipal agencies relying on Kern County farmland as a destination for sludge responded in November with a lawsuit contending that the county violated the California Environmental Quality Act by failing to review the environmental impact of its sludge ban. The Southern California agencies also claimed they are exempt from local ordinances. The Superior Court trial, moved to presumably neutral Tulare County, is now in the discovery phase. The dispute even migrated to the Legislature, where Sen. Richard Polanco (D-Los Angeles) introduced SB 1956, which would prohibit local governments from adopting biosolids regulations more restrictive than the federal government's. Assemblyman Roy Ashburn (R-Bakersfield) countered with legislation (AB 2495) specifically requiring local agencies to abide by the building and zoning ordinances of other local jurisdictions. Polanco has put his bill on hold, but Ashburn's remains alive, having received unanimous approval in the Assembly. Although Kern's contested ordinance officially declared the county's willingness to accept "exceptional quality" sludge, the sincerity of that commitment is in doubt. In May, the Yakima Co. abandoned plans to build a composting facility able to handle 600,000 wet tons (biosolids are 75 percent water) of sludge a year from eight Southern California waste agencies. The company blamed fierce community opposition, which led to permitting delays. To municipal waste managers, the failure of Yakima's plans suggests that public perception — not legitimate concerns about health risks or groundwater purity — is responsible for Kern County's ban. And they see that attitude as shortsighted. "We think it's a more reasonable, sensible option" than burying it in a landfill, said Mike Sullivan, Sanitation Districts of Los Angeles County biosolids recycling coordinator. His agency sends 1,500 to 2,000 wet tons of sludge a week to Kern County, reimbursing farmers for the cost of hauling it, spreading it and handling the paperwork — a sum that averages around $25 a ton. The cheapest alternative would be to truck the sludge to a landfill the agency owns, but that would shorten the landfill's three-year life expectancy. And it would mean forgoing the utility of a nutrient-rich organic fertilizer, as well as ignoring the broader question of what to do with so much waste. And if the sanitation agencies lose their legal attempt to overturn Kern County's ban? There's always Arizona. "They welcome the stuff there," Sullivan said. Contacts: Kern County counsel's office: 661-868-3800. Sanitation Districts of Los Angeles County: (562) 699-7411 EPA Biosolids website: www.epa.gov/unix0008/community_resources/muni/water/wbiosolid.html