Organic Materials Management

Biosolids

• Biosolids Usage
• Classifications
• Land Application
• Composting
• Alternative Daily Cover
• Landfilling
• Incineration
• Disposal and Regulatory Resources

Biosolids are the nutrient rich by-product of wastewater treatment, generated by channeling human waste through nearly 250 treatment plants and collection systems throughout California. Although the terms biosolids and sewage sludge are often used interchangeably, biosolids are the end product after treating sewage sludge with anaerobic digestion in combination with heat.

With the prohibition of ocean disposal of wastewater residuals in 1992, the use of biosolids as soil amendments (soil conditioners or fertilizers) or for land reclamation has increased to reduce the volume of biosolids that must be landfilled, incinerated, or disposed of at surface sites. In the last several years, numerous scientific, political and social factors have contributed to a growing public concern over the safety of biosolids which has resulted in strict local ordinances banning or severely restricting biosolids use in several California counties.

The management of biosolids in this state is layered and complex. This complexity is amplified by overlapping federal, State and local laws and ordinances, competing and fragmented jurisdictional oversight, shifting scientific evidence on human health and environmental safety, and sometimes short-term political solutions.

An item was presented to the CIWMB on these issues.

Biosolids Usage

According to the California Association of Sanitation Agencies (CASA), California generates 750,000 dry tons of biosolids every year, most of which are Class B biosolids. Of this 750,000 dry tons:

• 54 percent are land applied.
• 16 percent are composted.
• 12 percent are used as alternative daily cover at landfills.
• 6 percent are disposed of in landfills.
• 4 percent are surface disposed.
• 8 percent are incinerated or stored.

Note that the 6 percent landfilled (approximately 45,000 tons) represents about 0.1 percent of all materials disposed in Class I (hazardous waste) landfills.

Classifications

Biosolids can be used as a soil amendment/fertilizer but are also disposed of when land application uses are not available or accessible, and too costly. When land applied, biosolids are generally used in four forms: as a rich, moist soil amendment, dried pellet, liquid, or compost. There are essentially three categories of biosolids: Class B biosolids, Class A biosolids, and Exceptional Quality (EQ) biosolids.

• Class B biosolids may have low levels of pathogens which rapidly die-off when applied to soils, essentially becoming pathogen-free within a short period following application when the "Part 503" Rule requirements are followed. "Part 503" refers to the section in Title 40 of the Code of Federal Regulations, where various standards related to pathogens and metals in biosolids are codified. (Regulation Example: Riverside County)
• Class A biosolids are essentially free of pathogens prior to land application. The metal contents requirements under the Part 503 Rule are the same for Class A and Class B biosolids. (Regulation Example: Riverside County, Chapter 13.24)
• Exceptional Quality biosolids have lower metals concentration requirements than either Class A or Class B biosolids and have the same pathogen levels as Class A biosolids.

Land Application

Land application is the primary way biosolids are used in California and is currently the most controversial. Biosolids are used to enrich nutrient-depleted and/or barren soil with essential nutrients that, because they are organically bound, are released gradually to plants. Concerns about the land application of biosolids have been expressed by members of the general public regarding potential health effects related to such application. Some of the specific concerns include the presence of pathogens, heavy metals, and other chemical constituents in biosolids, and odors in areas where land application occurs. While no studies have directly linked the use of biosolids in this manner to harm in human or ecosystem health, a review by the National Research Council (NRC) of current federal regulations on biosolids (i.e., the Part 503 rule) cites problems in risk assessment methodologies and calls for additional research into biosolids safety. See the "Health Effects" section of the Board's April 2004 agenda item for more details on the NRC study.

Composting

Composting is the second largest use of biosolids with approximately 16 percent of the biosolids being composted for agricultural, horticultural, and land reclamation uses. Biosolids can be composted using a bulking agent such as wood chips or co-composted with green waste. Biosolids composting requires accessibility to an existing permitted facility with the capacity to accept additional material or a significant capital investment and operational outlay to fund the permitting, construction, and operation of a new facility.

There are currently several biosolids composting operations operating in California with the majority of operations located in Southern California. At this time, the overall size of the market for composted materials is uncertain and competition exists with the green waste composting market. Market considerations are an important aspect of composting since in the absence of an end market, composted materials would, by necessity, have to be landfilled. Composters who end up landfilling biosolids would incur financial losses due to tipping fees plus the costs incurred during the production of the biosolids into compost.

Alternative Daily Cover

Approximately 12 percent of the biosolids generated in California are used as alternative daily cover (ADC) at some landfills. ADC is material used to cover and contain landfilled materials at the end of each day and is a critical part of vector control at landfill facilities. Certain materials are permitted for use as ADC because of their physical characteristics and manageability. Of the 161 active landfills in California, three routinely accept biosolids for use as ADC. Regionally, there are areas in California where there are no landfills that accept biosolids for use as ADC and thus ADC is not a widespread biosolids management option.

Landfilling

Approximately 6 percent of the biosolids generated in California are disposed of at landfills. Biosolids can only be disposed of at permitted landfills. Some landfills permitted for the disposal of biosolids do not accept biosolids on a routine basis. Of the 161 landfills located in California, 60 are permitted to accept biosolids for disposal while only a portion of this 60 actually accept biosolids for disposal. As with ADC, there are regions in California where there are no landfills that accept biosolids for disposal. Due to limited landfill availability and the fact that the materials are disposed of rather than being beneficially used, landfill disposal is not a widespread management option.

Surface disposal methods account for 4 percent of the biosolids produced in California. Surface disposal methods require large amounts of vacant land which is lined with an impermeable material prior to the implementation of disposal operations. These operations are individually permitted and monitored by the California Regional Water Quality Control Board. Surface disposal is used on a limited basis by several wastewater treatment agencies and is not used on a widespread basis due to the dedicated land area requirements.

Incineration

Approximately 5 percent of the biosolids generated in California are incinerated. Incineration involves the high temperature burning of biosolids using a fuel supply such as natural gas or diesel fuel. The resultant ash is significantly lower in volume than the feedstock (biosolids) and, since the incineration process concentrates the trace metals that were present in the biosolids, there is a higher metal content. The ash is typically landfilled. Incinerators require significant capital investment and have high operating costs. There are three operating facilities statewide, each with a very limited capacity relative to the total amount of biosolids produced statewide. Due to existing and increasing air quality regulations, permitting of additional facilities is not considered likely and thus incineration is not considered a widespread management option.

Approximately 3 percent of the biosolids generated in California are stored temporarily in onsite facilities, such as lagoons. The biosolids are dried and further processed while in storage prior to the final deposition of the material using one or a combination of the management options described above.