At a glance
- Guardrails first: HVB excludes co-digesting municipal biosolids with community organics unless a dedicated pyrolysis pathway documents the temperature and retention needed to keep PFAS and other contaminants out of downstream uses.
- Pathogen framing: The Class A/B and Exceptional Quality distinctions signal how much pathogen and vector reduction the material has received and therefore where it can safely land across agricultural, reclamation, and landscaping sites.
- Regulatory alignment: New York Part 361 imposes setbacks, agronomic limits, incorporation timing, and annual reporting expectations that every application plan must describe.
- PFAS vigilance: We track NYDEC's Program Policy DMM-7 interim PFAS strategy and Draft DMM-7a (public comment open through Jan 9, 2026) so sampling, verification, and thermal controls match the latest expectations.
When biosolids enter a circular system
Biosolids only enter the HVB circular flow after passing through a standalone pyrolysis system with documented temperature, retention, and feed handling controls; those controls are what keep PFAS, metals, and other persistent contaminants away from digestate, soil, and water reuse pathways.
Verification bundle before any reuse:
- Documented operating temperature and retention profiles for the pyrolysis run.
- Chain-of-custody and segregation protocols that keep biosolids-derived streams isolated from other organics.
- Testing plan for the resulting ash or char tailored to the intended reuse (e.g., ash chemistry, PFAS screening).
- Clear go/no-go criteria that must be satisfied before any downstream deployment.
Position statement
Hudson Valley Biogas maintains a firm posture against co-digesting municipal sewage sludge/biosolids with other community organics because PFAS, heavy metals, pharmaceuticals, and similar contaminants are not removed during anaerobic digestion and can compromise the downstream integrity of digestate, soil amendments, or water reuse.
Biosolids are only permitted through the HVB circular system after they have passed through a standalone pyrolysis system designed to keep those contaminants segregated. Each pathway must document thermal profiles, retention time, and handling controls that prevent cross-contamination with other organics so digestate and fertilizers remain suitable for agriculture and land restoration.
Biosolids 101
Definitions & origins
Biosolids are the nutrient-rich solids recovered from a wastewater treatment plant after raw sewage sludge passes through stabilization processes such as digestion, composting, or heat-drying. The stream begins as human waste, food fats, soaps, and municipal runoff before being processed into a stabilized product that is easier to handle and transport.
Why classifications exist
Regulators tier biosolids because the level of pathogen reduction, vector attraction control, and metal testing determines where the material can be safely reused. The classification helps match the biosolids treatment to the sensitivity of the receiving environment - whether it is an agricultural field, reclamation site, or landscaping project.
Biosolids classes and what they mean
Untreated sewage sludge versus treated biosolids
Untreated sewage sludge is the solids expelled from clarifiers - wet, odorous, and managed as waste. Treated biosolids are that same material after it has been stabilized through digestion, dewatering, heat, or composting methods that reduce biological risks. Treatment does not strip every contaminant, so the classification system remains important even after the material is dewatered.
Class A vs Class B (pathogen reduction framing)
Class A biosolids meet pathogen reduction requirements that allow unrestricted crop use because the material has passed high-temperature and/or time-based treatments. Class B biosolids meet lower pathogen thresholds and thus carry waiting periods, site controls, and signage before human or animal contact resumes. The distinction is guided by vector attraction reduction practices and documented test results, not by whether the material is digested.
Exceptional Quality (EQ) as a distribution concept
Exceptional Quality (EQ) is a distribution label applied to biosolids that meet the strictest metal, pathogen, and vector attraction limits permitted under 40 CFR 503. EQ status signals that the material can travel through a broader market, but it does not address PFAS or emerging contaminants, so HVB still evaluates every EQ shipment against our PFAS policy before reuse.
What can be used where-
| Use case | Regulatory allowance | HVB guardrail |
|---|---|---|
| Food crops (edible portion contacts soil) | Only Class A/EQ or ash that meets contaminant/PFAS limits; Class B is prohibited under 40 CFR 503.32. | HVB requires pyrolyzed ash that passes PFAS and metals testing before nutrients are returned to food-acreage; no untreated or Class B deliveries are accepted for these sites. |
| Feed/fiber crops (hay, silage, biomass) | Class B allowed with a 30-day wait; Class A/EQ can be used immediately. | Only ash or other biosolids-derived products with documented PFAS policy and testing move toward feed/fiber fields, and the supplier's controls must align with NYDEC expectations. |
| Pasture or grazing land | Class B requires a 30-day wait before animals return plus access controls and signage. | Untreated streams are barred unless pyrolyzed, and livestock owners receive the waiting-period documentation so they can keep animals out until the site is reopened. |
| Reclamation (mine sites, brownfields, stormwater basins) | Class A and Class B may be used when public exposure is limited and restrictions are observed. | Use only stabilized, tested material and provide DEC-approved restoration plans that detail how the material will be handled and monitored. |
| Landscaping/greenspace (turf, public gardens) | Class A/EQ may be used; Class B is typically avoided except under strict signage and access controls. | HVB keeps untreated biosolids away from public landscaping unless pyrolysis and contaminant testing are complete, plus a documented management plan follows each delivery. |
These distinctions summarize the regulatory permissions and the tighter internal guardrails we impose to keep downstream reuse consistent with HVB's safety goals.
Class B land application restrictions
40 CFR Part 503.32 outlines the federal waiting periods and access controls for Class B biosolids; every permittee also layers signage, fencing, and monitoring as needed and states commonly layer additional restrictions on top of these minimums.
| Scenario | Waiting period | Access/site restrictions |
|---|---|---|
| Food crops with edible portions touching the soil surface | 14 months | No harvest or grazing; post, lock, and monitor the site until the restriction lifts. |
| Food crops with edible portions above the surface (tree fruit, tree nuts) | 12 months | Keep fencing posted, limit nonessential access, and document when the waiting period expires. |
| Food crops with below-surface edible portions | See the federal baseline table below for the 20/38-month timing based on incorporation. | Maintain the same signage and access controls until the longer of the two waiting periods ends. |
| Feed/fiber crops (hay, silage, fiber) | 30 days | Restrict cutting and grazing, keep the area posted, and limit personnel access until the interval passes. |
| Pasture or grazing land | 30 days before animals return | Gates remain closed, signs stay posted, and only trained crews enter until animals are allowed back. |
| Turf grown for sod or lawns with high public exposure | 12 months before harvest/sale (longer if permit requires) | Signs remain posted, public access is limited, and harvest dates are documented. |
| Public access (high potential) | 1 year | Lock gates, post signage, and defer events until the restriction lifts. |
| Public access (low potential) | 30 days | Post signage and monitor the site while access is limited. |
Class B land application: required site restrictions (federal baseline)
| Site or use | Requirement |
|---|---|
| Food crops where the harvested parts touch the sludge/soil mixture and are totally above ground | Do not harvest for 14 months after application. |
| Food crops where the harvested parts are below the surface |
|
| Food crops, feed crops, and fiber crops | Do not harvest for 30 days after application. |
| Animals | Do not graze for 30 days after application. |
| Turf | Do not harvest for 1 year if it will be placed where public exposure is high or on a lawn (unless permitting authority specifies otherwise). |
| Public access (high potential) | Restrict access for 1 year. |
| Public access (low potential) | Restrict access for 30 days. |
These are federal baseline restrictions; states and permits may be stricter.
What can be grown on land receiving Class B biosolids-
The federal waiting periods above determine which crops can be planned for Class B applications. This is planning and eligibility guidance, not an agronomic prescription; always verify the permit language and any state-specific add-ons before planting or grazing.
Generally compatible
- Feed and fiber crops (hay, silage, biomass): harvests resume 30 days after application.
- Pasture or grazing land: keep livestock off the field for at least 30 days and maintain fencing/signage until the period ends.
- Reclamation plantings and stormwater basins with low public exposure: observe the posting/access controls while the restriction runs and report the timing.
- Certain row crops where the edible portion does not touch the soil surface (tree fruit, tree nuts): plan for the 12-month wait, and if a harvested part is below ground, follow the 20/38-month rule tied to the surface exposure duration before incorporation.
Higher sensitivity
Leafy greens, root crops, or any crop whose edible portion contacts the soil must meet the longer waiting periods, and some local permits may prohibit those uses entirely. Incorporation timing matters for below-ground harvests: 20 months if the biosolids stay on the surface for four months or longer before incorporation, and 38 months if the surface interval is shorter.
New York State compliance notes (Part 361)
- Setbacks separate application sites from property lines, residences/public contact areas, wells, and surface waters/wetlands (e.g., 25 feet from property/residences, 150 feet from potable wells, 50 feet from streams or wetlands).
- Land application is prohibited where groundwater/bedrock is shallow or the ground is saturated or frozen, unless the biosolids are injected below the surface.
- Application rates cannot exceed the agronomic rate (DEC can impose tighter limits on phosphorus).
- Incorporation is expected within 24 hours of surface application and sometimes sooner if it is relied on for vector attraction reduction.
- Annual reporting must list the crop grown on each field plus the planned crop for the following year.
Setbacks and access controls
6 NYCRR Part 361 spells out setbacks from property lines, residences/public contact areas, potable wells, and surface waters or wetlands, plus posting and entry controls that keep the public and sensitive habitats separated while restrictions run.
Agronomic rate, incorporation timing, and reporting
New York requires biosolids to be applied at or below the crop's agronomic rate (the department can further constrain phosphorus-based limits), incorporated within 24 hours of surface application (shorter timelines apply when relying on that incorporation for vector attraction reduction), and documented through annual reports that list the crop grown on each field and the planned crop for the following year. Permittees must retain sampling, PFAS testing, and application records for DEC review.
PFAS and emerging contaminants: why HVB is cautious
PFAS concerns are a major reason HVB avoids co-digesting municipal biosolids with other community organics; protecting downstream reuse quality is the core value driving that choice. Before any material moves downstream, it must pass through a dedicated pyrolysis system with temperature logs, ash sampling, and chain-of-custody records so stakeholders can confirm the stream never reunited with digestate, soil, or water reuse flows.
New York's DEC Program Policy DMM-7 interim PFAS strategy and Draft DMM-7a expansion for biosolids-derived products (public comment open through January 9, 2026) show the state is tightening monitoring and reuse controls; HVB follows those policies and points partners to the NYSDEC biosolids management page for ongoing updates.
Practical checklist: what to ask a WWTP or biosolids supplier
- Provide the most recent representative sampling results for pathogens, regulated metals (As, Cd, Pb, Hg, etc.), and the PFAS suite (PFOS, PFOA, PFNA, etc.).
- Confirm the biosolids class, the vector attraction reduction method used, and whether the stream is destined for Class A/EQ, Class B, or pyrolyzed ash.
- Explain how the load meets 40 CFR Part 503 and 6 NYCRR Part 361 limits before it departs the treatment plant.
- Share the supplier's PFAS policy, how it aligns with NYDEC DMM-7/DMM-7a, and the latest PFOS/PFOA concentrations.
- Document the land application management plan: fields, planned crops, setbacks, incorporation timing, and the pyrolysis pathway (temperature logs, retention profiles, ash handling).
- Detail the site restrictions, posting/access controls, and who is accountable for enforcing compliance.
- Describe the chain-of-custody, segregation, and cross-contamination controls that keep this stream separate from other organics.
If you're offered biosolids or sludge: questions to ask before saying yes
- Is this untreated sewage sludge or treated biosolids-
- What class is it (A/B) and what documentation supports that designation-
- What vector attraction reduction method was used to achieve that class-
- What are the most recent pollutant/metals test results-
- What PFAS policy applies (especially under NY rules) and what are the latest PFOS/PFOA results if they are available-
- What is the land application management plan (fields, crops, setbacks, incorporation timing)-
- What site restrictions apply and who is responsible for enforcing compliance-
- Chain-of-custody: how do you keep this stream segregated and avoid cross-contamination if other organics are being handled-
HVB asks these questions because accountability is how communities trust digestate and soil/water reuse; practical answers help everyone make an informed yes/no decision.
Sources (primary and program guidance)
- 40 CFR Part 503: pathogens, site restrictions, and vector attraction reduction
- Cleaned-up Cornell LII copy of 40 CFR Part 503
- NYSDEC Biosolids Management page (land application program and permitting)
- NYSDEC Program Policy DMM-7: PFAS interim strategy
- NYSDEC Draft Policy DMM-7a notice (public comment open through Jan 9, 2026)
- NYCRR 361-2.5 land application requirements (Cornell LII)
Informational, not legal advice; confirm with permitting authorities.