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| 3.12.1 The Growing Need for
and Importance of Waste Minimization and Recycling |
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Recycling means reintroducing waste material into the production process, to supplement
primary resources. The use of waste as a raw material saves resources and primary
raw material, reduces air and water pollution, and extends limited landfill life.
Recycled products can also save financial resources through lower material costs
and lower disposal costs. In some cases, using recycled products can improve material
performance as well. Consequently, using recycled materials is a key aspect of more
efficient and environmentally sensitive highway design and construction. [N]
Recycling also saves energy. A quantitative assessment of environmental impacts on
life cycle of highways found that most energy is consumed in the manufacturing stage
of construction materials, with consumption of 1,525 tons of oil equivalent (TOE)/functional
unit (1 km and 4 lanes of highway). [N]
Energy consumption in the maintenance and repair stage was also fairly high among
the life cycle stages; the next highest consumption was for the construction and
demolition stage. Through the whole life cycle of 20 years, 2,676 TOE of energy/functional
unit was consumed, and this corresponds to SO2, NOx, and CO2 emissions of 62.1 tons,
17.1 tons, and 2,438.5 T-C, respectively. [N]
The United States spends approximately $13 billion annually (1999 dollars) on highway
construction and repairs, requiring nearly 350 million tons of both natural and
manufactured construction materials. [N]
Approximately 4.1 billion metric tons of non-hazardous solid waste materials are
generated annually. The majority of these materials are being landfilled in many
states; however, landfills and access to materials are increasingly limited by growing
environmental regulations and permitting requirements, restrictive zoning laws,
land uses, and other economic considerations. Community opposition has restricted
the expansion of and forced the closure of existing landfills, quarries, and gravel
pit operations. The latter has created localized shortages of construction aggregates
and borrow materials in some areas, further adding incentive to explore alternatives
in order to alleviate such shortages and to conserve natural resources.
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| 3.12.2 Common Recycling Applications
in the U.S. and Europe |
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Research into new and innovative uses of waste materials is continually advancing.
Many highway agencies and private organizations have completed or are in the process
of completing studies and projects concerning the feasibility, environmental suitability,
and performance of using recycled products in highway construction. Reduction of
waste material at its source and reuse of construction waste complement recycling
efforts.
Recycled materials are typically used in such applications as bituminous pavements,
Portland cement concrete (PCC) pavements, road base, embankments and fills, flowable
fills, landscaping, bicycle paths, parking lots, and appurtenances such as signs,
fencing, barriers, traffic delineators, etc. Some of the most notable uses of recycled
materials in the highway environment over the last 20 years have included recycled
asphalt pavement (RAP), reclaimed concrete pavement, coal fly ash and blast furnace
slag. A few states and local governments have passed legislation to promote recycling
in road construction. In some case beneficial use determination processes (BUDs)
evaluate uses though a wide range of approaches are used; California, Illinois,
Massachusetts, New Jersey and Pennsylvania are working to standardize the BUD process
and create reciprocity. State DOTs and state environmental protection agencies (State
EPAs) are also trying to balance the desire for increased use of recycled materials
with concerns about potential environmental impacts of leaching from recycled materials.
FHWA produced a review of the use of recycled materials in highway construction
in the early 90s, a summary of which is included below. [N]
NCHRP Synthesis of Highway Practice 199, Recycling and Use of Waste Materials
and By-Products in Highway Construction. [N]
developed a methodology for assessing the suitability and practicability of specific
waste resource materials in transportation applications, determining appropriate
uses, developing design and construction guidelines, and evaluating long-term in-service
performance and applied the methodology to a spectrum of waste resource materials.
The project developed a comprehensive CD-database including material and engineering
properties; environmental information; legislative, regulatory, and litigation information;
history of past use and performance; references to existing specifications and guidelines;
information on material generation (source, quantity, existing inventory); and information
on ongoing research and demonstration projects. [N]
Congress has supported development of a Recycled Materials Resource Center (RMRC)
at the University of New Hampshire to perform research and outreach to reduce barriers
to recycling in a highway environment. FHWA and RMRC produced a 2001 manual to provide
guidance to assist transportation agencies in the maintenance of high-quality roads
that perform to high engineering standards over their design life, without future
problems, and to promote cooperative efforts with environmental agencies to ensure
that present and future environmental problems do not arise when recycled materials
are used in highway infrastructure. Read the Framework for Evaluating Use of Recycled Materials in the Highway
Environment online. [N]
. The private sector is also developing innovations in processing and applications.
In 1999, FHWA, AASHTO, and NCHRP sponsored an international scan tour to Denmark,
Sweden, Germany, the Netherlands, and France to review and document innovative policies,
programs and techniques in Europe and make recommendations that would lead to the
reduction of barriers to recycled material use. In particular the scanning team
sought applications in highway construction in the ROW (e.g., roads, shoulders,
medians, bridges, culverts, swales, appurtenances) though activities associated
with highway construction can also result in use of recycled materials outside the
highway ROW. In Europe, government policies and regulations such as bans on landfilling,
landfill taxes, and natural aggregate taxes support recycling. Generally, clear
and unambiguous engineering and environmental test methods and performance standards
help to reduce uncertainty and allow recycled materials to compete with natural
materials. Where tests and standards do not exist, governments often support recycling
by sharing risk.
In the U.S. there are widespread needs for clear engineering and environmental test
methods and performance standards. The owner or contractor generally assumes risk.
The States, academia and the private sector are conducting significant research.
In the U.S. some recycled materials like RAP, coal fly ash and blast furnace slag
are widely used in a true free market situation because of their excellent performance
and competitive costs. Other materials are used more locally in response to more
specific local market forces. There is little federal government involvement, except
for construction procurement guidelines for materials like coal fly ash. Rather,
the situation is driven at the state level. For example, the State of Pennsylvania
has adopted legislation to promote recycling in the highway environment. RMRC's
Report for the International Scan Tour on Recycling Techniques, is available
on-line. [N]
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| 3.12.3 General Recommendations
for DOTs with Regard to Recycling and Waste Management |
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The International Scan Tour Report generated a number of recommendations for AASHTO's
Standing Committee on the Environment and Subcommittee on Materials that are pertinent
to recommended practices for state DOTs: [N]
- Include a recycling strategy in the sustainability aspect of strategic plans
and long range research priorities.
- Create a framework to consider the use of recycled materials in project planning,
alternatives analysis, and mitigation analysis.
- Encourage long term materials supply plans and recycled materials availability
plans.
- Develop clear engineering and environmental guidelines at the State and Federal
level that are available for suppliers and decision-makers.
- Develop courses on recycling.
- Evaluate contractors with respect to use of recycled materials or environmental
protection during contract performance reviews.
- Develop and implement the use of warranty and performance based specifications.
[N]
The following practices are also recommended to facilitate environmental stewardship
in materials management: [N]
Materials should be used in the most effective way possible.
- Structures should have long lives.
- Materials should be recyclable.
- Consumption of energy in the construction development should be optimized.
- Alternatives for conventional resources should be considered.
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| 3.12.4 Life Cycle Cost-Benefit
Analysis |
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The most recent TRB research needs meeting called for an expansion of life cycle
analysis to reduce waste, prevent pollution, and encourage recycling. [N]
FHWA's Highway Economic Requirements System (HERS) is an example of a tool that supports
tradeoffs between preservation and improvement projects. The HERS application is
based on the Highway Performance Monitoring System (HPMS) database, and is intended
to replace HPMS as the source of biennial federal needs studies submitted to Congress.
The HERS algorithms address both highway capacity and pavement preservation needs.
Thus, state application of HERS or HERS/ST are uniquely suited to asset management
studies that are more comprehensive than those addressed by individual management
systems (e.g., pavement management and congestion management) and can explore tradeoffs
between system preservation and system improvement or expansion.
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| 3.12.5 Areas for
Recycling Applications |
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Areas for recycling applications in maintenance, many of which are applicable for
other parts of the organization, are described in detail in Section 10.13.
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| 3.12.6 Specifications for
Recycled Materials in Transportation Applications |
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Available AASHTO or DOT specifications for the recycled materials covered in ensuing
sections are included as web links within those sections, and more specifications
are being developed all the time. The Recycled Materials Resource Center (RMRC)
has a project underway to Develop and Prepare Specifications for Recycled Materials
in Transportation Applications. Participants in the project - Caltrans, FDOT, Illinois
DOT, Mass Highway, Michigan DOT, Mn/DOT, NHDOT, NJDOT, NYSDOT, NCDOT, Ohio DOT,
PennDOT, TxDOT, and WisDOT - identified the recycled materials of greatest interest
to DOTs and assisted in the development of specifications. Six material/application
combinations are underway. The first of these, a specification for glass cullet
use as an aggregate base course, was published in 2001 (M-318-01). This past year,
a second specification, "M-319-02, Reclaimed Concrete Aggregate for Unbound
Soil-Aggregate Base Course," was published in the 22nd edition of the AASHTO's
Standard Specifications for Transportation Materials and Methods of Sampling and
Testing. A third specification, "Use of Recycled Concrete as an Aggregate
Substitute in PCC Pavements," is under review by the AASHTO Technical Section.
A specification for coal fly ash in embankments has been tabled by the Technical
Section, while a draft specification for reclaimed asphalt pavement as an aggregate
in asphalt concrete has been prepared for submission to the Technical Section. The
last specification on the use of roofing shingle scrap as an aggregate for asphalt
concrete is in preparation.
See also:
As of February, 2004, specifications under development via RMRC projects include
the projects listed in the Appendix. RMRC keeps an updated list at their RMRC Resources and Specifications site. [N]
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| Continue to Section 3.13 »
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View Table 11: FHWA Summary of Known Uses in Waste Applications 