Steve Diddy

Composting, organics recycling and the concept of zero waste has become so popular that I receive inquires like this almost daily. Ten years ago the majority of the callers were from municipal governments that wanted to compost biosolids or better understand the issues involved around adding food waste to their yard waste composting operation. Today, there are more solid waste companies (haulers) and merchant facility developers who wish to compete for source separated organic waste streams that include food waste. Regardless of who calls, my answer to the question above is always, “Well, that depends…”

The garbage industry has long focused on metrics like $/mile or $/ton, so it is natural that, when they ask what seems like a simple question, they expect a simple (and rapid) answer. However, there are many different methods to produce a compost product, and even more variables to consider when designing a compost facility.  All of which affect the bottom line.

If you are considering developing a commercial composting facility, there are three steps that you should follow in order to help you evaluate the viability of your opportunity:

  1. Learn the Biology and the Business of Composting
  2. Qualify Your Opportunity
  3. Dig into the Details—Conduct a Pro Forma Analysis

 

Step 1: Learn the Biology and the Business of Composting

Composting is part (simple) biology and part business. You don’t need to understand the biology part in scientific detail. You do, however, need to understand the role that feedstock mix, airflow, moisture, temperature and processing time play in facilitating the biological process (like a baker understands cooking). By controlling these variables per best management practices (BMPs), you will control nuisance odors and create a marketable product (see Figure 1).

Your understanding of the business of composting should start with learning the steps of the process, the regulatory requirements, the technology choices and the local compost market (see Figure 2). For example, the compost process typically includes three process phases (primary, secondary and curing).  In these phases there are generally regulations that concern the air and water leaving the process, the temperatures during the process and often the stability at the end of the process.

There are three broad groups of process technologies: Aerated Static Piles (ASP), In-vessel and Windrow. Each process has its pros and cons, and any can be used in combination with the others.

You can learn much about the biology and business of composting by attending national and regional composting conferences, taking the Compost Facility Operator Training Courses offered by the U.S. Composting Council, visiting facilities and reading industry periodicals.

Step 2: Qualify the Opportunity

Step two is where you really need to roll up your sleeves and get into the details. This may include hiring qualified consultants as well as:

  • Quantifying and Characterizing Feedstocks
  • Site Selection and Site Study
  • Market Evaluation

 

Quantify and Characterizing Feedstocks

Feedstocks are what you want to compost. The feedstocks are called food waste, yard waste, land clearing debris, construction debris, crop residue, pre-consumer, post-consumer, vegetative, protein, etc. Feedstocks have different densities, moisture contents, C/N ratios and levels of contamination. You will need to know the characteristics and quantity of each feedstock you expect to process per day (and account for peak-days or months based on seasonal variations—think grass and leaves).

Figures 3 to 6 are all called food waste and are presently being composted via commercial facilities. You can observe that their physical characteristics differ greatly and can imagine that the process required for one feedstock would differ from another (and also affect the cost of their processing). They are a) residential curbside-collected food waste and yard waste, b) post-consumer prison waste, c) pre-consumer grocery store waste and d) source-separated food waste collected from urban multi-family buildings/apartments. Figure 7 and 8 are examples of yard waste from municipal curbside collection programs.

Site Selection and Site Study

Needless to say I could write an entire article on finding the right site for locating a compost facility. I’ve heard it said that land with solid waste handling permits is the most valuable land in the country. Certainly, having enough land that is not too close to neighbors, not too far away from your feedstocks, and with the proper zoning and permitting is valuable land indeed.

Appropriate facility sites can be located in industrial areas, wastewater treatment plants, landfills, farms, mines, even abandoned factories. However, sites need to be researched for permitting purposes (zoning, traffic, flooding, etc), odor studies and neighborhood acceptance.

Here is a little known fact: The Right Choice of Process Technology is Site Specific. That is the size and odor sensitivity of the site, the weather, the desired facility throughput, the facility process goals, capital budget, labor constraints, and projected tipping fees all contribute and narrow down the range of possible process designs and technology alternatives for any given opportunity. Therefore, choosing the process technology prior to selecting and evaluating the opportunity puts the cart a bit before the horse. There are pros and cons to each system type—and the appropriate technology for any given site depends on its analysis.

Market Evaluation

Depending on the quality of your product, the annual volume, your location and a host of other considerations (like length of the growing season) selling your product for the price stated in your pro forma can range from easy to difficult. It is essential to avoid creating the Brown-Mountain of unsold products. Evaluating market potential is often a good place to consider hiring qualified consultants.

Step 3: Pro Forma Analysis

Pro Forma Analysis is a study of, and the preliminary design of, the facility that will ultimately be constructed at a proposed site. It requires assistance from a qualified and experienced compost process engineering firm; and civil engineering firm. The Analysis includes:

  • Environmental Compliance Assessment (odors, air emissions, surface and ground water)
  • Feedstock Analysis (mass balance, mix recipes, lab analysis if necessary, consider pilot projects)
  • Initial Process Design (review process, process technologies and operational alternatives)
  • Initial Facility Design (drawings, layout, single line electrical, process and instrumentation diagram, material flow)
  • OPEX and CAPEX Facility Cost Analysis (labor, power, fuel, water, sewer, equipment, staff skill and labor requirements)
  • Revenue and Profit Models (land, design, permitting, equipment, tip fee, product revenue, carbon and pollution credits)

 

The outcome of the Pro Forma Analysis provides preliminary drawings in enough detail to obtain accurate construction estimates, begin permitting; and provide enough cost and revenue data on which to build an accurate business Pro Forma. Based on this solid data you can now make an informed business decision on the sustainability of your project.

After conducting a Pro Forma Analysis those who find out that owning and operating a compost facility would not have met their goals are happy to figure this out during this preliminary planning stage. When they decide to continue with the Detailed Design and Construction of their compost facility, they are able to do so with better planning and greater confidence.

Steve Diddy has worked in the compost, recycling and solid waste industries (both public and private) since 1989. He joined Engineered Compost Systems (Seattle, WA) in 2001 and is their Director of Business Development. ECS is an engineering and manufacturing firm dedicated to providing appropriate compost design, technology and ongoing technical support to their clients. Their staff is comprised of compost experts; mechanical, electrical, and software engineers; project engineers; project/construction managers and supporting technical staff. Steve can be reached at (206) 634-2625, via e-mail at steve@compostsystems.com or visit the Web site at www.compostsystems.com. 

Part 2 of this article will focus on design considerations and how municipalities can put composting projects out to bid. 

Figure 1

Figure 1

What the industry trade organization, U.S. Composting Council and the waste industry, in general, believe are best management practices for standard values for the incoming feedstock mix.

Figure 2

Figure 2

The process of composting and, in particular, the components that are the most important for good planning: the solids are the feedstocks, odor and VOCs are in the air, and water includes condensate/leachate and rainwater.

 

Figure 3

Figure 3

Residential curbside collected food waste and yard waste.

 

Figure 4

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Post-consumer food waste from a federal prison.

 

Figure 5

Figure 5

Food waste pre-consumer from a grocery.

 

Figure 6

Figure 6

Curbside collected food waste from  high density residential.

 

Figure 7

Figure 7

Curbside collected yard waste.

 

Figure 8

Figure 8

Curbside collected yard waste.

 

Figures courtesy of Engineered Compost Systems.

 

Sidebar

Appropriate Process Design and Process Technology Selection

Appropriate technology is a local decision. That is the size and odor sensitivity of the site, the desired facility throughput, the facility process goals, capital budget, labor constraints, and projected tipping fees all contribute and narrow down the range of possible process designs and technology alternatives for any given opportunity. Therefore, choosing the process technology prior to selecting and evaluating the opportunity puts the cart a bit before the horse. There are pros and cons to each system type—and the appropriate technology for any given site depends on its analysis. ECS offers both in-vessel and ASP compost process technologies:

  • SV Composter (in-vessel with stationary vessels)
  • CV Composter (in-vessel with containerized vessels)
  • AC Composter (Fabric Covered ASP)
  • ASP Systems (in several different configurations – both covered and uncovered)

 

Below are examples of four ECS compost process technologies; two ASP systems (covered and uncovered) and two In-vessel systems (stationary and containerized vessels)

  • Figure 9 is a fabric covered ASP in a discrete pile configuration

Figure 9

  • Figure 10 is an organic covered in a bunker wall configuration

IF

  • Figure 11 is a stationary in-vessel (tunnel) system

Figure 11

  • Figure 12 is a containerized in-vessel system

 Figure 12

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