Overview
Biosolids are a product of the water resource recovery process that serve as a renewable source of nutrients and organic matter. Biosolids are federally recognized and regulated pursuant to the Clean Water Act and the Code of Federal Regulations (CFR) Part 503 Biosolids Rule. Under these laws and regulations, biosolids must achieve science-based quality standards, be safeguarded through pretreatment/source control programs, and have their use and disposal reported on annually.
Biosolids also represent a nutrient-rich, organic material that can be in integral part of the circular resource economy we rely upon in modern society. As long as people continue to flush, there will be biosolids. The key is to use this locally generated resource in an efficient and beneficial manner. This can lead to numerous benefits, including:
- Reduced reliance on fossil-fuel-based, inorganic fertilizers
- Improved soil and crop health, and improved crop yields
- Increased soil water holding capacity, reducing overall water usage
- Stored carbon in the soil, reducing impacts of greenhouse gas emissions
- Restored scarred landscapes to functional ecosystems
CASA’s biosolids program was created in 2003 to:
- Represent and advocate for sound biosolids management in the State of California
- Engage in dialogue among regulators and the regulated communities
- Inform CASA members, regulatory agencies, and surrounding communities about important changes that impact biosolids and local clean water agencies.
- Identify and support ongoing research that helps to answer pressing questions and support science-based regulations.
- Demonstrate support for integrating circular resources like biosolids into broad-reaching environmental initiatives that benefit our local communities and the larger global circular water society efforts.
Biosolids have demonstrated benefits when used in accordance with best practices and established regulations and are a key in realizing a circular resource economy.
CASA Biosolids Fact Sheets
- National Communication Guidance: PFAS and Biosolids Management
- Biosolids: A Natural Resource (2-sided flier)
- Biosolids Regulatory Primer
Biosolids Guidance Resources
- Biosolids 101 Video & Presentation, (G. Kester)
- Contractor Guidance for POTWs – Document & WEF Presentation
- County Biosolids Ordinance Map (2023)
- Biosolids Options (Infographic)
- Excess Digester Capacity Study
California Regulatory Documents
- CalRecycle SB1383 Website
- CalRecycle SB1383 Presentation
- State Water Resources Control Board Biosolids General Order
- Statewide Programmatic Environmental Impact Report
- CRNA Natural & Working Lands Climate Smart Strategy
Regional Association Resources
Federal
Key Regulations & Issues
- EPA Federal Biosolids Regulations: 40 CFR Part 503
- EPA Federal Biosolids Website
- 2023 DC EPA Meeting Summary
Regulations in Development
- EPA Draft Biosolids Risk Assessment for PFOA & PFOS
- EPA PFAS Problem Formulation for Risk Assessment Presentation
- CASA FAQ Quick Reference to EPA OIG report
Research
- National Research Council: Biosolids Applied to Land Report
- EPA Update: NAS Report 14 Projects
- EPA OIG Report: Pollutants in Land-Applied Biosolids
- CASA FAQ Quick Reference to EPA OIG report
- EPA Guide on Use of Soil Amendments for Remediation, Revitalization and Reuse
- EPA FAQ on Ecological Revitalization of Superfund Sites
- USDA Twenty Years of Experience Says Sewage Sludge Beneficial
WEF Biosolids Convening
Key Research
Climate
End-Use
- 45 Year Review of Biosolids Land Application in CO
- National Biosolids End Use Report 090622 (2018 data); Data link
- Biosolids Land Application & Food Crop Quality Assurance
- Review of Health Survey of Residents Living Near Farm Fields
- National PFAS Study – Phase 1 Report
Reclamation
- CASA Assessment of Runoff from Fire Damaged Lands Amended with Biosolids
- Restoring Fire Ravaged Land in California with Biosolids
- British Columbia Biosolids Use in Constructed Wetlands for Landfill Leachate Treatment
- British Columbia Biosolids Use in Restoring Shoreline Riparian Area
- British Columbia Biosolids Use in Wetland Creation
Overall
- Water Research Foundation: Biosolids Research & Biosolids Research Summit 2019
Select Comment Letters
- 4-9-25 CASA Comments on CalRecycle Zero Waste Plan Recommendations & Pathways
- 3-28-25 CASA Comments on USEPA Draft Risk Assessment for PFOA & PFOS in Biosolids
- 3-28-25 W5170 Expert Review of US EPA Draft Risk Assessment for PFOA & PFOS in Biosolids
- 2-20-25 CASA Comments on USEPA Approved Method 1633A
- 5-16-22 Comment letter to USDA Request for input to support American-made Fertilizer Production (Supporting signatory with WEF & Northwest Biosolids)
- 4-18-22 Maine – Letter to Governor Mills Requesting Veto of LD 1911
- 7-12-21 Comment Letter to GlobalGap
- 1-22-21 CASA Comments on EPA PFAS Destruction Guidance
- 7-24-20 W4170 Rebuttal to OIG Report
- 10-5-20 Certified Organic Crop Program: Comments to Lift Prohibition on Biosolids
- 5-18-20 Climate Action Reserve: CASA Comments on CAR soil enrichment protocol
- 12-24-03 EPA Assistant Administrator Mehan Rebuttal to Center for Food Safety Petition to ban Land Application of Biosolids
- 10-18-19 CASA Comments SB 1383 Draft Regs
- 12-04-18 NACWA Comments to OIG
- 11-29-18 Joint Comments to OIG (CASA, NEBRA, MABA, VBC, USCC)
- 9-26-18 Biosolids Alliance Proposal to GlobalGAP
- 2-17-16 Comments to CDFA on Application Rates
- 4-27-16 Global GAP Letter Final on Biosolids Prohibition
- 7-14-15 Final comments on Proposed Revisions to Compost and In-vessel Digestion Regulations
- 7-28-14 Letter to Whole Foods Opposing their Prohibition of Biosolids
- 10-5-20 Certified Organic Crop Program: Comments to Lift Prohibition on Biosolids