February 22, 2011 | General

Conducting A Feedstock Supply Assessment

BioCycle February 2011, Vol. 52, No. 2, p. 33
Types and amounts of commercial source separated organics, potentially available for feedstock at a proposed anaerobic digestion facility, were identified in a study for Ramsey and Washington counties, Minnesota.
Dan Krivit and Deborah Carter McCoy

IN the Twin Cities region of Minnesota, the Ramsey/Washington County Resource Recovery Project (the Project), a joint powers program, has been exploring using anaerobic digestion (AD) to convert food and organic waste into renewable natural gas. The Twin Cities metropolitan region, comprising seven counties, has diverse collection and processing options for source separated organics (SSO), defined as food, fiber or paper-based packaging and plant material. These include food rescue and donation, rendering, direct feeding to livestock (cattle and hogs) as allowed by the Minnesota Board of Animal Health, manufacture of livestock feed and composting.
In 2009, a feasibility study was conducted on the various aspects of planning, siting, developing, financing, constructing, and operating a proposed AD facility. The study identified some of the opportunities and challenges associated with feedstock from residential SSO collection programs. It also identified the “low-hanging fruit” of SSO from commercial establishments that was not yet recovered and potentially available for the AD facility. Based on this potential, the Project contracted with the consulting firms of Foth Infrastructure and Environment, LLC and JL Taitt & Associates, Inc. to estimate the amount of commercial SSO not currently recovered by other programs.
The 2010 assessment contained estimates of the types and amounts of commercial SSO potentially available for feedstock at the proposed AD facility.
The assessment characterized the types of commercial establishments that may be the most likely sources for larger volumes of targeted SSO including nonrecyclable paper. Existing food rescue and recovery programs were described to help characterize the food waste that was already treated as reusable or recyclable commodities. The assessment also highlighted some of the potential planning and operational issues that should be considered when securing a new supply of such commercial, source separated organic materials.
A preliminary supply specification was developed that focused on the following types of materials: All types of food waste including produce, dairy products, bakery goods, deli foods, frozen and dry goods, meats and seafood, fats, cooking oils and grease and spent grains; Fiber or paper-based packaging, including paper and cardboard; and plant materials (e.g., yard trimmings). The researchers always kept in mind that surplus, edible food from the existing food rescue programs should not be displaced.

With a preliminary specification in hand, the work turned to evaluating current and potential SSO recovery. Foth reviewed historical trends for the diverse public and private SSO recovery systems in the Twin Cities region. Private for-profit companies have developed competitive systems, including sourcing programs, for securing food waste supplies. The SSO data was extracted from county reports submitted to the Minnesota Pollution Control Agency (MPCA). The trend lines in Figure 1 indicate the growth and long history of private SSO rescue and recovery. When county reports first started recording organics recovery in 1991, there was rapid growth indicated in part due to increasing awareness and also improvements in reporting.
Foth then evaluated the total amount of SSO reported in 2009 to the Minnesota Pollution Control Agency (MPCA) as rescued and recovered from Ramsey and Washington counties. The total amount was 38,640 tons: Rescued (food to people): 810 tons; Food waste direct to livestock: 22,380 tons; Food waste to manufacture livestock feed ingredients: 15,410 tons; Organic waste to compost: 40 tons. Roughly 47 percent of commercial SSO is rescued and recovered in Ramsey and Washington counties. Remaining commercial food waste and nonrecyclable paper (53%) is disposed.
While the potential for residential SSO recovery is also significant, it was beyond the scope of this commercial assessment. In addition, commercial yard trimmings and brush were not identified as priority materials for the proposed AD facility based on low biogas yield from brush and other wood materials, significant seasonal fluctuations, and very mature yard trimmings collection and composting infrastructure in the Twin Cities region.

Foth then devised a means to estimate available SSO in the waste stream, based on disposal rate estimates of SSO as reported in relevant literature and applied to employee counts. A database of selected commercial establishments in Ramsey and Washington counties was developed based on the searchable Dun and Bradstreet (D&B) publication. The D&B database was sorted by Standard Industrial Classification (SIC) code categories and employee counts. Using this method, the assessment estimated about 45,000 tons of SSO were disposed each year from commercial establishments in the two counties. This number is higher than the reported recovery estimates by counties to the state and offers validation that additional material is in the waste stream. Table 1 shows these organics disposal estimates by SIC category highlighting the largest sources of potential SSO, but does not include all materials or waste generators considered within the definition of source separated organics.
Eighty percent of the total tons are disposed from three categories: food stores; eating and drinking places; and educational services. Locally, many grocery stores, with the exception of the major chains, are not yet recovering the full complement of SSO. The analysis estimates that about 51 percent of the total SSO disposal is from restaurants and 20 percent is disposed by grocery stores, suggesting that these two specific categories of businesses, as well as educational services, should be targeted for additional SSO recovery. While most restaurants do not have SSO recovery programs, some restaurants have been separating SSO for decades. The research also shows that wholesale produce companies and bakeries are being serviced by existing SSO recovery operations such that these materials are already valuable commodities.
Ramsey County, the MPCA, elementary schools, and the University of Minnesota have adopted SSO recovery programs but many other government and educational institutions do not yet have collection programs and could be targeted for SSO recovery. Educational institutions dispose about nine percent of the total available food waste and government agencies dispose about five percent. Colleges, universities and other educational institutions should continue to be a priority target for recovery as they have large kitchen facilities with high volumes of food waste.

Although restaurants as a category are the largest potential suppliers of SSO, collection presents a significant challenge given the often small physical size, diversity of establishments, decentralized ownership and management structure, and high staff turnover rates. The risk of contamination of SSO with prohibited materials (e.g., glass, metal, nonbiodegradable plastic) must be anticipated. Small, frequent loads from these generators must be serviced on a very regular schedule. The quality and consistency of SSO from the preconsumer (i.e., food preparation operations in the kitchen) will be significantly higher and more reliable than postconsumer (i.e., table waste) material from retail customers. In general, fruits and vegetables comprise the majority of preconsumer SSO from full service restaurants. Additional materials of significance include bakery, dairy and sugar-based/starch-based products.
Given the significant volume of eligible organic material disposed, restaurants should be carefully considered in any new SSO recovery initiative. Also, different supply specifications for existing end markets in the Twin Cities region may result in different collection economics and market dynamics. The largest economic savings from instituting a new SSO program should come from downsizing trash service levels, such as size of dumpster and frequency of pulls. This downsizing relationship, however, is not always direct, especially if the restaurant has different collection service providers for SSO, other recyclables and/or trash. The market for providing organics recycling service to restaurants is still in the initial stages of development.

Existing service fees for SSO collection and recovery are priced to compete with the comparable mixed MSW removal charges. Some of the larger commercial establishments with the highest value and volume food by-products (e.g., bakeries, wholesale produce processors) enjoy SSO collection services at very low prices, even “free” removal (i.e., SSO collection, including disposal, without service charges). This study suggested that new SSO programs and facilities, such as the proposed AD facility, should assume that committed feedstocks from larger suppliers already marketed as valuable commodities will not be available without a substantial discount for service.
Both Ramsey and Washington counties implemented a County Environmental Charge (CEC) in 2003 to fund solid waste programs thereby replacing or significantly reducing the solid waste management service charge added to property tax statements. Together with the Minnesota Solid Waste Management (SWM) Tax, the CEC counties demonstrated a major policy shift to better align the financing of government solid waste programs directly with the generation of waste. The SWM Tax and the CEC are charged by the haulers on the mixed MSW removal service (both collection and disposal). The SWM Tax and CEC are not charged on recycling services such as municipal curbside recycling or SSO collection programs, therefore the incentive to avoid these added service fees is significant.

Based on the data reviewed, the following strategies were recommended to Ramsey and Washington counties: Retain the CEC and expand promotions of economic savings due to SSO recovery; Encourage downsizing of mixed MSW service levels with increased amounts of SSO recovery; Help assure that the end market for SSO is reliable and long-term (e.g., a large-scale SSO facility); Continue to invest in education of generators and haulers.
In discussions about how to best capture new volumes of SSO, the following strategies were developed by the consultant team: Assure reliable and high quality SSO collection services; Consider innovative hauling concepts (e.g., backhauling with existing livestock farmers, route optimization for account density, integrated transfer operations with other organics such as yard waste, etc.); Encourage competitive pricing of SSO recovery services vs. traditional mixed MSW removal charges; Encourage downsizing of mixed MSW service levels with increased amounts of SSO recovery.
Both Ramsey and Washington counties have favorable prospects for additional commercial SSO recovery. While mature organic management methods exist for some SSO materials generated in the counties, development of additional organics processing and management capacity is needed for a fully integrated and complete organic recovery system. The counties intend to monitor and work with the development of an AD facility as it progresses.

Dan Krivit is Senior Project Manager with Foth Infrastructure & Environment, LLC in Lake Elmo, Minnesota. Deborah Carter McCoy is with the Saint Paul-Ramsey County Public Health Environmental Health Section in Maplewood, Minnesota.
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Links to the reports cited in this article:
An Integrated Organic Waste Management System: From the Perspective of Commercial Generators: JL Taitt &Associates, Inc., May 2010
Source Separated Organic Materials Anaerobic Digestion Feasibility Study: Foth Infrastructure & Environment, LLC, June 2009
Organic Materials from Commercial Establishments: A Supply Assessment: Foth Infrastructure & Environment, LLC, June 2010

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