A fines idea: C&D fines prove to be a product with a learning curve.

Mixed C&D

No matter what you call them, "construction and demolition debris fines" or "recovered screen materials," they are ultimately an unavoidable byproduct generated when construction and demolition debris (C&D) is processed or recycled. As recyclers and users of this material have discovered, sometimes there is a steep learning curve associated with obtaining permits for and using this material for various reuse applications.

In many instances it is apparent that C&D fines have great potential for various reuse applications; however, performance considerations must be made so that potential impacts are ascertained up front and prior to use.

Depending upon the recycler's processing methodology (e.g. screen size, up-front separation, etc.), C&D fines can make up as much as 30 percent of a C&D recycler's output. Fines are made up of many constituents, such as:

* sand and dirt with limited quantities of asphalt products, brick, block, concrete, gypsum and glass

* organic materials such as wood

* small amounts of fluff materials (paper, cloth, foam and fabric)

* ferrous and nonferrous metals.

Much of the C&D fines tonnage generated in the United States has been and is currently used for lower value end use markets, such as alternative daily cover (ADC) at landfills. Competition for landfill use of fines has grown where C&D recycling has become more prevalent in light of higher tipping fees and competition for disposal space. In those areas other uses for fines have been investigated and capitalized on (e.g. landfill closure material, sub grade material, fill, etc.).

Typically the alternative uses require a "beneficial use determination" (BUD) permit which redefines the material as a product. However, like any product in any industry, a bad experience, rogue use or improper pre-use investigations can paint a broad negative brush stroke against the entire C&D recycling industry.

HEEDING THE CALL FOR DATA

Because C&D fines are generated at commingled C&D recycling facilities, it is a commodity that must have viable outlets. Given the importance of maintaining and securing viable outlets, the Construction Materials Recycling Association (CMRA) has retained Green Seal Environmental Inc. of Sandwich, Mass., to conduct a nationwide search for fines test data.

This project was developed in an attempt to quantify and determine what the common chemical components are within C&D fines.

The objective of this research was to establish a baseline of compiled industry-wide data that could provide recyclers, users and state regulatory agencies with a significant amount of test data that could ultimately reduce the timeframes for obtaining permits, avoid additional study and reduce permit costs associated with characterization.

It was also CMRA's intention to make this information available nationwide, especially in geographical areas where C&D recycling is in its infancy, which will allow future recyclers to focus on the creation of "new" markets rather than duplicate what has been performed by others in the past.

As part of the scope of work, the 48 contiguous states were contacted and asked to provide any available C&D fines test data. Surprisingly, many state agencies did not have any data at all. At the same time, CMRA members were also contacted in an effort to create as large a database as possible. All of the data was then tabulated and is now in the process of being assessed.

PRELIMINARY RESULTS

Based on the data received, it is clear that C&D fines are non-hazardous. However, based on a few of the data sets, specifically elevated total lead concentrations, a statistical analysis (T-Test) is being performed on the entire data set to normalize the information. Based on the preliminary research, Green Seal Environmental has concluded the following:

1. The fines do not display "hazardous" characteristics and as such, "regulated" applications, including ADC, shaping and grading and fill are viable uses.

2. Based on certain characteristics of the material (e.g. high gypsum content), producers and users should assess their material to ensure that it is suitable for its intended use.

3. There is significant variability between facilities and states with respect to what type of chemical characterization is performed.

4. C&D fines are suitable for some land applications and landfill environments and do not present a significant threat to human health and the environment.

5. Even though we expect that statistical analysis to conclude that the fines are non-hazardous from a RCRA standpoint, this does not mean that fines can be used for any land-applied application without first assessing potential impacts, such as exposure, physical properties and the potential to impact sensitive receptors.

HYDROGEN SULFIDE GAS

Recently, the generation of hydrogen sulfide (H2S) gas at landfills has become a hot topic across the United States. H2S gas is slightly heavier than air and has an undesirable rotten egg odor. The human nose can detect H2S at very low levels, approximately 0.2 parts per billion in the air. At greater concentrations (greater than 10 parts per million) significant health effects can occur.

The H2S gas is produced in a landfill environment when sulfur-reducing bacteria (SRB) consumes sulfur compounds under certain environmental conditions. When any one of those conditions is absent, the SRB cannot live and, therefore, H2S will not be produced.

During the past few years, the finger has been pointed at C&D-derived materials such as fines as the primary cause of H2S problems because the material can contain a fair amount of gypsum (calcium sulfate).

However, H2S can also be caused by other materials within landfills, such as sewage sludge, certain types of municipal solid waste and other wastes that contain sulfate. These potential sources have never received the scrutiny that C&D fines have.

In an effort to mitigate or reduce the potential for H2S generation in a landfill environment, some regulatory agencies have responded by creating new rules and policies.

For example, Massachusetts requires C&D recyclers to remove as much gypsum as possible during the sorting process, after initial tipping, if the material is to be used for shaping and grading during a landfill closure. To date, it appears that this regulation has been relatively successful.

A more abrupt measure was taken by the New Hampshire Department of Environmental Services (NHDES) in the summer of 2004.

With an approximate 10-day notice, the NH DES banned the use of C&D fines as ADC at MSW landfills because of nuisance odor conditions, particularly H2S. This measure stunned C&D recyclers in the region and in light of the short notice placed an undue hardship on the impacted facilities.

As a result of this ruling, the CMRA, along with the affected C&D recyclers, interested parties and Green Seal Environmental, worked with the NHDES to form a working group of stakeholders on the issue. Based on the work of this group, NHDES has agreed with the stakeholders that certain interim "best management practices" (BMPs) could be implemented to allow C&D fines to be used in the landfill environment. The final product of that work can be viewed at www.des.state. nh.us/whats_new_interim_best_management.pdf.

Unfortunately, the steps taken by the NHDES have prompted some regional MSW landfills to reduce their reliance on C&D fines, which has ultimately reduced the number of viable outlets for this material.

ONGOING RESEARCH

Based on the lack of qualitative data on the relationship of C&D fines to the generation of H2S, the CMRA is either organizing or monitoring several projects related to C&D fines and hydrogen sulfide gas. They include:

* Developing test methods for sulfate (the current methods are not effective in ascertaining the potential for H2S production);

* Developing a standard that can predict the potential amount of H2S gas production given an amount of sulfate in fines;

* Studying the effects of best management practices on H2S gas production;

* Developing additives to counteract H2S gas production; and

* Developing best management practices for C&D fines use nationwide to maintain its viability as a beneficial material.

ONGOING PROJECTS

Because no standard test procedures have been developed for measuring or quantifying gypsum content in C&D fines, Dr. Timothy Townsend of the University of Florida is working with CMRA to develop a standard laboratory procedure.

Townsend will conduct validation testing of the developed procedure on sources of C&D debris ADC from several different recyclers. This will also provide baseline data for understanding differences in gypsum content among different ADC sources.

In addition, this research should develop a standard operating procedure (SOP) for measuring volatile solids in C&D debris ADC. The resulting SOP could be used by any laboratory and should minimize differences in results among laboratories.

In addition, Green Seal Environmental has had the opportunity to work with CMRA member LL&S Inc. in Salem, N.H. LL&S has taken measures to study the effects of certain best management practices on H2S production. The company has studied the effects of mixing fines with inorganic materials to "dilute" or change an environmental characteristic so bacteria can't grow.

LL&S has also studied the use of biological additives that consume H2S. To date, the results have been positive; however, more testing will be performed in the spring and summer of this year.

CMRA member ERRCO of Epping, N.H., is working with Dr. James Wang of Northeastern University to study its C&D fines. Progress has been made on identifying how much H2S gas is generated given a known amount of sulfate and certain environmental conditions.

Besides their ongoing studies, ERRCO and other C&D recyclers are investigating other beneficial use applications that would be suited for this type of material.

CMRA member Taylor Recycling of Montgomery, N.Y., has completed a project with Aceto Corp. and Wang. Their study ultimately quantified the effect of a "Fuller's Earth" chemical product that can destroy and/or significantly reduce the potential for H2S generation.

Other actions being taken by CMRA include reaching out to environmental agencies, industry professionals and other solid waste organizations to dispel myths, provide real data and help them help C&D recyclers. Many CMRA members are spending their time and capital in this effort to ensure the future of C&D recycling.

Green Seal Environmental gives kudos to all organizations involved for making positive strides toward preserving a necessary component that makes C&D recycling a viable industry.

It is already apparent that C&D fines display potential attributes for various reuse applications, and additional studies will provide a comfort level to processors, users and regulators.

Once the actions are completed, the next step will be to distribute this information so that progress can be made with respect to growing the overall industry.

Condition               Detail

pH                      Between 4 and 9 (optimum)
Temperature             Between 300C and 380C
Amount of air           Anaerobic (absence of oxygen)
Food source             Sulfate ions
Water                   Moist or wet
Carbon source           Wood, paper, glue, etc.

Gregory Wirsen is principal of Green Seal Environmental, Inc. based Sandwich, Mass. Green Seal Environmental is an engineering and sciences consulting firm. Worsen also serves as the director of the New England Chapter of the CMRA.