A successful municipal composting system—one that processes various types of waste from a community into compost—is no simple undertaking. Large-scale composting must accommodate food waste, biosolids, or other organic materials while adhering to regulations regarding odors, groundwater contamination, and other environmental impacts. Achieving this requires specialized knowledge and equipment.

How to Develop a Municipal Composting System

Before selecting a composting system, there are several critical factors to consider:

• Characteristics and quantity of the anticipated feedstock
• Desired final product
• Odor and emissions considerations
• Site footprint and potential layout
• Budget
• Zoning requirements and location relative to the community
• Regulatory requirements and environmental impact studies

Once these design criteria are established, selecting the appropriate industrial composting system becomes more straightforward. Working with experts ensures the most viable, economical, and environmentally successful outcome.

The Biggest Challenges with Municipal Composting

Municipal composting projects face significant challenges, and ECS has successfully addressed each of them in past projects. Examples include:

• Odor management. In the case of the City of Long Beach project, ECS provided a tunnel-type in-vessel system, a roof-covered aerated static pile (ASP) for secondary composting, and a four-auger feedstock mixer. The sealed, insulated design of the vessels minimizes fugitive emissions.
  • ECS offers odor modeling to quantitatively predict odor impacts.
• Maintaining semi-optimized process conditions for composting over the long-term. In the case of the Freestate Farms project, ECS designed an aerated static pile system with trench aeration floors, reducing maintenance and ensuring long-term efficiency.
  • ECS offers aeration demand testing to measure compost process data from customer feedstock.
• Water Management. In the case of the Napa Composting project, due to the City wanting to upgrade its compost facility to process more yard waste along with the addition of food waste and digestate (while still adhering to rigorous permit conditions required by the state water board) ECS provided extensive technical support throughout the long permitting process.
  • ECS offers water modeling services to help calculate the water generation and water consumption for a composting facility.

ECS offers compost tools for success

Since 1999, ECS scientists and engineers have helped design, develop, and maintain over 80 municipal composting systems worldwide, including:

ECS Procurement Recommendations for Municipal Composting Projects

Challenges of a Turnkey Single-Contract Approach

Many municipal composting projects trigger public procurement requirements. ECS has experience with both a single RFP for a turnkey solution and a separate equipment + construction contract. Based on our experience, the latter provides the best value. Here’s why:

• Loss of Owner Control: In a turnkey contract, ECS would be a subcontractor to a prime construction firm, which has final decision-making authority. This diminishes our ability to advocate for the owner and operator.
• Misaligned Financial Interests: Turnkey bids sideline owners and operators in the design process, reducing opportunities for value engineering and leading to avoidable operational challenges.
• Regulatory and Permitting Uncertainty: Permitting negotiations (e.g., with Puget Sound Clean Air Agency) often introduce conditions requiring design modifications. A turnkey contract does not easily accommodate these changes without costly change orders.
• Wide Variability in Construction Costs: Based on 14 recent composting facilities, we observed substantial cost differences:
  • Maximum: $436 per ton per year (TPY)
  • Minimum: $49 per TPY
  • Average: $154 per TPY These cost variations stem from infrastructure, site conditions, labor/material costs, and permitting requirements—not ECS’s system pricing.
• Turnkey Contracts Increase Costs: A prime contractor consolidates consultant, subcontractor, and vendor deliverables while adding overhead, contingency, and markup.

Recommended Two-Contract Approach

ECS delivers the most value when focusing on its core competencies: designing, permitting, and supplying aerated composting and emissions control systems. A team-based design approach aligns interests and minimizes risk. Our recommendations:

1. Develop a Compost Process Specification
   o Throughput requirements
   o Minimum retention time to achieve Solvita 5
   o Aeration system and control system performance
   o Odor control performance
2. Issue an RFP for the Aerated Composting System
   o Require bidders to detail their engineering calculations, materials, operations, and references.
   o Specify a fixed-price bid with transparent deliverables and cost adjustments based on material changes.
   o Allow bidders to propose an inflation factor if procurement exceeds 12 months, using standard indexes (CPI, HDPE pipe costs, stainless steel costs).
3. Award a Three-Phase Contract for the Compost System
   o Phase 1: Collaborate with the owner’s team for permitting and detailed design (used for construction bidding).
   o Phase 2: Deliver the aerated composting system, either as owner-supplied or novated to the construction contractor.
   o Phase 3: Provide training, warranty, and ongoing technical support independent of the construction contract.
4. Award a Separate Construction Contract
   o Use the detailed design package to competitively bid construction, reducing cost uncertainties.
5. Procure Yellow Iron Equipment Separately
   o Include grinders, screens, loaders, conveyors, etc., in the operations contract, ensuring operators select equipment with the best life-cycle value.

Structuring an Effective Compost RFP

A well-structured RFP should focus on performance specifications rather than prescribing a detailed design. The goal is to allow vendors to leverage their expertise and proven solutions to meet project requirements, rather than dictating exactly how they must build the system.

For example, when purchasing a vehicle, a buyer might specify the need for excellent off-road performance but would not dictate how the manufacturer should engineer the suspension, drivetrain, or frame. Similarly, an RFP for compost equipment should define key performance outcomes—such as aeration efficiency, odor control effectiveness, and processing capacity—while allowing vendors the flexibility to propose the best solutions based on their extensive experience.

ECS has seen RFP packages range from as concise as six pages to as extensive as 1,200 pages. In one case, a municipality spent >$1M on engineering fees to design a pilot project. We could have designed and supplied the equipment for <$250k. Overly detailed engineering packages often require the vendor to repeat much of the same design work, leading to unnecessary costs. Instead, the most effective RFPs focus on:

• Throughput requirements (e.g., tons per year, material mix)
• Performance benchmarks (e.g., minimum retention time to achieve Solvita 5)
• Demonstrated experience with past installations, their performance and customer support
• Aeration system and process control criteria (e.g., airflow uniformity, ability to control with dampers)
• Servicability and life cycle cost

By keeping the RFP streamlined and focused on results, project owners can attract better proposals, avoid unnecessary engineering costs, and benefit from vendor expertise in delivering proven, high-performing composting solutions.

Conclusion

A separate equipment + construction contract approach enhances owner control, ensures flexibility in permitting and design, and reduces overall project costs. ECS’s extensive experience in compost facility development supports this approach as the best-value strategy for municipalities.
For more information, contact ECS today.