How Foamed Glass Aggregate is Being Used on Transportation Infrastructure at NJDOT: An Interview

NJDOT, like other State departments of transportation (DOTs), has become increasingly conscious of infrastructure’s environmental burdens and are seeking more environmentally sustainable materials in construction.  Recently, we spoke with Kimberly Sharp, Manager, Structural Design, Geotechnical Engineering and Geology, and Mohab Hussein, Project Engineer, Deputy Chief Technical, Geotechnical Engineering about NJDOT’s adoption of Foamed Glass Aggregate which serves an example of the deployment of an innovative, sustainable material.

To make foamed glass aggregate, crushed container glass is collected from recycling companies, finely ground into powder and mixed with a foaming agent, and sent through a kiln and softened. Bubbles form within the softened glass. When it cools, the material cracks and forms lightweight, coarse, foam-like aggregate pieces that can be used in various transportation construction projects.

Q. How did you learn of this material?

Foamed glass aggregate in use on the pilot project at Rt. 7 Wittpenn Bridge, Kearny

Aero Aggregates in Eddystone, Pennsylvania, reached out to the Department in 2018 to provide a technical presentation on foamed glass aggregate. An industry presentation is an established step in NJDOT’s process for exploring new technologies. If we are interested in the product, as we were in foamed glass aggregate, we start a pilot project.

Q.  When did NJDOT begin using foam glass aggregate?

Our pilot project was the Rt. 7 Wittpenn Bridge in Kearny, NJ in 2019. Use of this material replaced 32,000 cu.yds. of regular fill and saved almost 28 million bottles from the landfill. We used the material for a crossover from one side of the road to the other. We built it and let the contractor use the area for six weeks with heavy equipment traveling over it. We maintained survey equipment at the site and looked for settlement and any lateral spreading and nothing moved.

Q. What have been the most common uses?

For us at NJDOT, the most common uses have been as fill underneath roadways to raise the profile, behind existing abutments where we were putting in a new backwall and new girders and we wanted to lighten the lateral forces on the backwall, as backfill to the approach to a bridge, to resolve sheeting issues on a project, and as backfill behind a temporary wire wall.

Foamed glass aggregate placed behind an abutment on I-80 over Rockaway River, Denville

We have very soft, compressible soils beneath some of our roadways, and in areas of high tide or frequent flooding, therefore we want to raise the elevation of the roadway. Using heavy, natural fill material beneath the pavement box can lead to pavement that ultimately would ride like a roller coaster due to uneven settling.  A less costly approach is to over-excavate the existing soil and place with the foamed glass aggregate. At 22 lbs./cu.ft., the aggregate is buoyant, so regular weight soil is placed over it to weigh it down, and then the pavement box is built on top of the soil. Use of the aggregate lessens the amount of settlement and results in a nice smooth roadway.

Q.  Who are suppliers of this material?

Aero Aggregates is the supplier that we work with. They recycle glass from Pennsylvania and from a southern New Jersey recycling center. We appreciate that they are using local materials.

Q.  What are the environmental benefits of using this material? What is it replacing?

Foamed glass aggregate is saving millions of bottles from landfills. This material is made of 100 percent recycled material. In addition, the material replaces traditional backfill that would be quarried, and so minimizes depletion of natural resources. It also minimizes use of other material such as rebar, concrete and other foundation elements. In addition, it is lightweight, about half the weight of regular lightweight fill material, and so reduces transportation emissions. There are associated cost savings to its use.

Aggregate being applied behind wire wall on Fish House Road, Kearny

Q. Is there an ongoing assessment process for use of this material, or is it an established process?

We had questions in the beginning. The material was so light that we worried about its durability. The manufacturer provided results from testing and we tested the material in the field. Use of foamed glass aggregate is an established process at NJDOT. The material was first used in Germany in the 1980s, and in Norway in the 1990s to prevent rutting of pavements because it has good insulating qualities. It is useful in cold regions.

Q.  Are there limits to the transportation construction applications where this material can be used?

Foamed glass aggregate has its own compaction requirements; it is lightly compacted or graded out with lightweight equipment to avoid crushing of the aggregate. As mentioned above, it requires capping to weigh it down. Pavement design engineers want several inches of regular weight soil between the lightweight aggregate and the pavement box.

Q.   What is the state of industry knowledge and acceptance of the use of this material?

It is still early in the process of nationwide adoption. New Jersey is one of the first states to implement use of the material on our projects. We have received calls from many state DOTs asking how we began using it, and about our experience of using it in lieu of other lightweight material, so word is getting around. Aero Aggregates used it in Philadelphia around I-95. The industry is working on starting up new plants. Word is spreading through the contracting community. The first contractor that used it with us liked it so much they eliminated all other lightweight types of materials in the contract bid items. Through word of mouth, other design consultants and Contractors have picked up on use of the material.

Q.   Do you have current projects where this is being used and do you anticipate continued use of the material in the future?

View video on YouTube or access it from the NJDOT Platform

Yes, and we have some in design, and we will include foamed glass aggregate in the contract for future projects for consideration.

For future projects, we have not used foamed glass aggregate behind structural walls as yet, although we know it has been used in Philadelphia, and we are considering that application.

The Department is also considering applications related to temporary water storage in flood areas. Our current and past projects are using closed cell foamed glass aggregate, but an open cell aggregate is available. Its porosity might be beneficial in flood mitigation and other resiliency projects.

We really like the product and look forward to expanding its use. We are always looking for new technologies and this is one that will continue to be of great benefit.

Q.  What do you consider to be the keys to the successful adoption of the material?

Agency willingness has been the key to successful adoption of this innovative material.


Foamed Glass Aggregate [Video].  Retrieved at:

Foamed Glass Aggregate [Presentation].  Retrieved at:

From Landfill to Commitment to Communities Newsletter. How NJDOT Uses Non-Recyclable Materials for a Sustainable Future, Vol. 27, Spring 2023.  Retrieved at:

Image of a black car with a white electric charger plugged in to the rear left of it, next to the tail light.

VW Mitigation and Emissions Offset Funds Fuel NJ’s Clean Transportation Transformation

Image of Pdf cover reading 2019 New Jersey Energy Master Plan, Pathway to 2050. Behind the text is a wind turbine and a solar panel.
The 2019 Energy Master Plan, a guiding document for New Jersey’s clean transportation transformation. Courtesy State of New Jersey

In February of 2021, Governor Phil Murphy announced a historic $100 million investment in clean energy transportation vehicles and infrastructure, building on work laid out in the 2020 Energy Master Plan, which calls for a transition to 100 percent clean energy by 2050. In 2019, the State emitted 97 million metric tons (MMT) of carbon dioxide (CO2); with the implementation of the Energy Master Plan, annual emissions are projected to be dramatically reduced to 24.1 MMT of CO2. Several NJ State agencies are working to lay the foundation for this monumental transition. The $100 million commitment is only one aspect of a much larger, inter-agency undertaking.

The Energy Master Plan provided a blueprint for New Jersey’s greenhouse gas reduction goals, and the 2020 New Jersey Senate Bill 2252 (S2252), commonly referred to as the electric vehicle law, is the legislative impetus for such work. The New Jersey Department of Environmental Protection (NJDEP), the New Jersey Economic Development Agency (NJEDA), the New Jersey Department of Transportation (NJDOT), and NJ TRANSIT, among others, are now collaborating to achieve the transformation of the transportation sector, responsible for the largest share of the State’s net greenhouse gas emissions, to 100 percent carbon neutral.

Zero Emissions Vehicles (ZEVs) from Volkswagen Funds

The clean energy initiative is funded, in part, through a legal settlement negotiated between Volkswagen and the United States Environmental Protection Agency (USEPA) and the California Air Resources Board (CARB), after a court determined that the automaker had installed defeat devices that hid emissions of nitrogen (NOx) in certain vehicles models. From the resulting $3 billion settlement, New Jersey was allocated $72.2 million, which is now being administered by NJDEP for clean energy transportation projects.

Four men stand smiling in front of a trailer with two small white truck-like vehicles on them, the electric yard tractors that were just delivered to this facility.
Two new electric yard tractors delivered to Red Hook Terminals LLC in Port Newark. Courtesy NJDEP

The first and second rounds of New Jersey’s Volkswagen Mitigation Trust proceeds were awarded to select applicants for the purchase of ZEVs. For example, $1.9 million was given to a company in Trenton for five new electric school buses, and Jersey City received $2.4 million for five new electric garbage trucks. Red Hook Terminals LLC of Port Newark (pictured at right) recently received sufficient funding to purchase ten electric yard tractors.

Without sufficient charging infrastructure, the envisioned shift to EVs will prove impossible to achieve. One oft-cited reason hindering EV adoption is “range anxiety,” a fear of not being able to refuel for lack of nearby facilities. Currently, 95 percent of state residents live within 25 minutes of a DC Fast Charger, a distance that will only decrease as new chargers are built. Stations throughout the State can be located using NJDEP’s Public Electric Vehicle Charging Locator.

For Phase 1 of the Volkswagen Mitigation Fund disbursal, NJDEP allocated $3.2 million to pay for public fast chargers. In 2019, through the It Pay$ to Plug In program, VW funds have financed 827 new charging outlets, ranging from the City of Cape May, to Rutgers—New Brunswick, to the Village of Ridgewood.

Ongoing Initiatives

A screenshot of NJDEP's REGGi Climate Investments Dashboard. The Dashboard shows 19 projects funded, $22.25 million in funds awarded, an estimated 43,786.58 short tons of lifetime CO2 Emissions Avoided, and a map of projects across New Jersey, which shows a concentration in the northeastern section of the state.
The New Jersey RGGI Climate Investments Dashboard shows current clean energy investments from auction proceeds. Courtesy NJDEP

An important source of revenue for supporting Governor Murphy’s $100 million pledge is the Regional Greenhouse Gas Initiative (RGGI). RGGI is a multistate partnership that has set a regional cap on carbon dioxide emissions. Fossil-fueled power plants exceeding the limit must purchase extra capacity at an RGGI auction. In the first quarter of 2021, New Jersey received $27.1 million that will be invested to fight climate change according to a Strategic Funding Plan. The New Jersey RGGI Climate Investments Dashboard provides up-to-date, visual reports of progress on RGGI grants across the State. The initiative has awarded $22.2 million thus far to several municipalities, including for the purchase of two electric garbage trucks for the City of Trenton, and two electric shuttle buses for West New York.

The RGGI purchases coincide with Phase 2 of NJDEP’s Volkswagen settlement disbursal, announced in February, 2021. A further $31.7 million of funding for ZEVs from the settlement will be distributed across the state. As Passaic County receives RGGI funds for an electric shuttle bus, the City of Paterson has been allocated VW money for two electric garbage trucks. With VW funds and RGII auction proceeds, the City of Elizabeth School District purchased seven electric schoolbuses. Gradually, municipalities and companies across the state are beginning to grow their ZEV fleets.

Image of a row of Tesla Superchargers in a parking lot. The chargers are rectangular with plugs resembling gas pumps inside the hollow rectangle.
Tesla agreed to install V3 Superchargers at eight service areas on the New Jersey Turnpike. Courtesy Ank Kumar on Wikimedia Commons

To complement these 2021 ZEV additions, NJDEP has proposed spending an additional $5.4 million of Volkswagen funds for charging grants. For example, the agency selected an ACME grocery store in Woodbury, a Shell station in Wayne, and a hotel in Fort Lee, among others, for DC Fast Charger grants. The DC Chargers are being prioritized in this round because of their high efficiency: a twenty-minute charge can add 60 or 80 miles of driving range.

Emissions Mitigation for Heavy Transportation

In July, 2020, New Jersey and fourteen other states and the District of Columbia signed a Memorandum of Understanding (MOU) committing to collaborate on policies to convert medium and heavy-duty vehicle fleets, such as school buses and freight trucks, into ZEVS The MOU sets a goal of 30 percent electric share heavy and medium-duty vehicles sold in 2030, with a 100 percent share by 2050. The regional approach reflects an acknowledgement that transportation emissions are an interstate issue, and that interstate collaboration is necessary to meet such goals.

Image of a slide reading Proposed ZEV Sales Requirements, detailing how manufacturers in NJ will have to provide credits each year starting in 2024 to offset the emissions cost of the vehicles they are selling. By 2034, for example, they will have to sell (or purchase credits for) 50% of their vehicles as clean energy vehicles.
NJDEP’s proposed rules would follow California’s emissions credit/deficit system for medium and heavy vehicle sales. Courtesy NJDEP

To begin instituting this shift, NJDEP has started the rulemaking process for N.J.A.C. 7:27-31 and 33, two proposed regulations that would institute a credit/deficit program for manufacturers of trucks of over 8,500 pounds. Beginning in 2025, sellers of medium and heavy-duty vehicles would be required to generate or purchase credits to offset deficits from the sale of greenhouse gas-emitting vehicles. This offset could be accomplished by increasing sales of ZEVs, or by purchasing credits from another manufacturer. Deficits would increase every year through 2035, resulting in an increase in the number of commercial ZEVs sold in the state. This is modeled after the Advanced Clean Trucks (ACT) rule that California implemented in 2019.

For public transit, bus fleets must be converted as well. The state’s EV law, S2252, requires that NJ TRANSIT transition its new bus procurements to all-electric. New bus purchases must be 50 percent electric by the end of 2026, and 100 percent zero-emissions by the end of 2032. NJ TRANSIT, which received funds for eight new electric buses in Camden from VW Phase 1, will start testing these vehicles in service in the fall of 2021. One issue affecting the conversion is range; on certain routes, particularly in South Jersey, the required driving distance exceeds single charging capacity. NJ TRANSIT is currently exploring solutions such as building new chargers and making changes to operating routes.


Though $100 million is a significant investment, more resources will be needed to promote the transition from carbon-emitting vehicles. Further investment, as well as interagency and regional cooperation will be crucial to meet the Energy Master Plan’s goal of 330,000 ZEVs on New Jersey Roads by 2025.

NJDOT is working to support the efforts of agency partners to achieve the goals set out by the Energy Master Plan and mandated by the electric vehicle law. NJDOT has continued to invest in alternative mobility, increasing traffic efficiency, and the conversion of its fleet to ZEVs.  In a recent NJDOT newsletter, the Commissioner Diane Gutierrez-Scaccetti noted that the agency has worked with a team from Princeton University to determine an electric charging infrastructure implementation plan, the first step of which will be installation of equipment at the Ewing, New Jersey headquarters.

This infrastructure will be important not just for NJDOT but for the statewide fleet, which, as it transitions to ZEVs, needs centralized charging infrastructure. By law, the statewide fleet must be 25 percent electric by 2025, and 100 percent electric in 2035. NJDOT has already ordered 49 hybrid vehicles, progressing toward the department goal of 88 alternative fuel vehicles in service in the next three years.

Success will require not only committed public policy, but overwhelming public support to make use of the budding charging network, expanded subsidies, and soon-to-be converted fleets.


Higgs, L. (2021, May 26). NJ Transit Unveils Electric Bus Plan, But it Has to Compensate For Low Battery Range.

Johnson, T. (2019, June 4). Administration Promises Almost $25M to Electrify Transportation Sector. NJ Spotlight News.

Johnson, T. (2021, February 17). NJ to Spend $100M on Green Energy, Environmental Justice. NJ Spotlight News.

NJ Car. (2021, April 26). NJ CAR Hosts Webinar On NJDEP’s It Pay$ To Plug In EV Charging Grant Program.

NJDEP. (2019, June 3). Second Round of Volkswagen Settlement Funds to Support Development of Heavy-Duty Electric Vehicles, With Emphasis on Improving Air Quality in Environmental Justice Communities.

NJDEP (2021, June 1). NJ Public Electric Vehicle (EV) Charging Locator.

NJDOT (2021, April). How NJDOT is Working Toward a Cleaner New Jersey.

NJ Office of the Governor. (2020, January 27). Governor Murphy Unveils Energy Master Plan and Signs Executive Order Directing Sweeping Regulatory Reform to Reduce Emissions and Adapt to Climate Change.

Regional Greenhouse Gas Initiative. (2021, June 1). New Jersey RGGI Climate Investments Dashboard.

State of New Jersey. (2020, January 9). NJ S2252.

Tap Into Camden. (2021, 26 May). NJT Bringing Eight New Electric Buses to Camden This Fall.

United States Department of Energy. (2020). Electricity Laws and Incentives in New Jersey.