The roadbuilding industry has discussed sustainability for decades, but the pace of change has accelerated. Asphalt producers worldwide discover that green practices benefit both the planet and their bottom line through reduced costs and efficiency gains. This article explores how companies like Ammann are making asphalt production more sustainable through innovative technologies. For a broader overview of how Asphalt Plants and Pavement Construction Equipment a Complete approach to hot mix production works, read our detailed guide.
Dr. Hans-Friedrich Peters, executive vice president of Ammann’s Plants Division, provided an in-depth look at sustainable asphalt production. Ammann, a Swiss family-owned company since 1869, supplies asphalt-mixing plants and compaction equipment worldwide from its North American hub in Davie, Florida.
The Role of Recycled Asphalt in Sustainable Pavements
The green roadbuilding conversation begins with reclaimed asphalt pavement, commonly known as RAP. According to Dr. Peters, the biggest reductions in indirect CO2 emissions result directly from implementing RAP in asphalt production. He emphasizes that RAP should not be categorized as waste material but recognized as a perfectly viable substitute for virgin materials. The aggregates in reclaimed asphalt show little aging and remain mechanically and geometrically within the quality ranges of new material. Bitumen, the binding agent in asphalt, also holds up well over time. Its aging is limited and can be compensated by adding small amounts of new bitumen during the mixing process. When producers utilize RAP, they save on both aggregate and bitumen costs while simultaneously reducing emissions both initially and over the lifetime of the road.
High Percentage RAP Capabilities
Modern technology allows the use of RAP percentages up to 100 percent. In practice, the percentage is usually determined by the amount of RAP available and the specifications defined by local authorities. In highly specialized global roadbuilding markets, RAP contents exceeding 80 percent and even 90 percent are already occurring. Countries that did not initially adopt recycling are moving ahead quickly. China, for example, is leveraging some of the most advanced recycling plants to create mix with extremely high percentages of RAP. Earlier adopters are also recycling more than ever before, driven both by governments lifting restrictions and by asphalt producers recognizing the economic value of RAP. From an environmental perspective, all parties involved should increase their efforts to expand RAP usage for new pavements.
Innovative Plant Designs for Maximum Recycling
One of the most notable advances in plant design is the Ammann ABP HRT (High Recycling Technology) plant. This system is designed entirely around incorporating large percentages of RAP, elevating recycled material from a supporting role to the lead actor in the production process. The most striking feature is that the entire recycling system sits vertically, in direct line above the mixer. This vertical arrangement allows materials to be dropped rather than conveyed, which minimizes wear and optimizes transport of hot RAP. The design also leaves sufficient room in the plant tower for additive feed components and for carrying out inspection and maintenance work.
Alternative Heating Processes for Recycling
Ammann offers varied heating processes depending on the amount of recyclables required:
- RAH60 – A parallel flow dryer that can feed up to 60 percent hot recycled materials.
- RAH50 – A unique solution enabling RAP usage up to 40 percent. The dryer has a middle ring where a portion of RAP enters before delivery to the mixing tower, while the rest is injected directly into the mixer. Batch plants operate in continuous mode with the screen deck bypassed.
- Cold RAP addition – Up to 30 percent cold recycled material can go directly into the mixer without special dryers, meaning almost every standard Ammann plant can utilize that amount of RAP.
These high-recycling technologies represent a critical piece of the puzzle as we work toward a Building Sustainable Future.
Emissions Reduction Strategies in Plant Operations
Reducing emissions from asphalt production goes beyond incorporating RAP. Modern plants employ a multi-pronged approach targeting CO2, volatile organic compounds (VOCs), dust, and other pollutants. Dr. Peters outlined several key areas where Ammann has made significant progress.
CO2 Reduction Through Process Optimization
Ammann continually works to reduce CO2 emissions through several methods:
- Actively cooling the drum to improve thermal efficiency
- Increasing drying efficiency across the production process
- Utilizing alternative energy sources such as biofuels and wood dust
- Switching to electrically heated vertical bitumen tanks instead of traditional horizontal tanks heated with thermal oil
These technologies can diminish CO2 emissions by 10 percent or considerably more, depending on the age of the plant and the specific technology selected. The bitumen tank farm presents a particularly significant opportunity. Traditional horizontal tanks heated with thermal oil consume oil and produce emissions. Switching to electrically heated vertical tanks eliminates oil consumption and emissions while proving cost-effective. Electrically heated bitumen tanks have become standard across Europe and other parts of the world.
Volatile Organic Compounds and Odor Control
Volatile organic compounds must be diminished in the clean gas stream to reduce total carbon value. Bitumen fumes are the primary source of odor at asphalt plants. Ammann offers different solutions to contain both fumes and odor, focusing on reduction points including the bitumen tanks, the skip and load-out levels, and the stack. As with dust, these measures ensure plants remain good neighbors in their communities.
Dust Filtration and Baghouse Technology
Dust emissions are managed through the baghouse filter system. Ammann plants use a highly efficient baghouse filter that lowers exhaust dust to less than 0.0044 gr/ft3, setting an exemplary benchmark. The company is working to reduce this further to less than 0.0022 gr/ft3. However, Dr. Peters notes that logistical operations around the plant, including trucks and wheel loaders, create much more dust than the chimney. Key dust reduction points beyond the baghouse include the cold feeder, load-out area, skip hood, overflow silo, filler loading area, screens, belts, and transfer points.
Emissions Benchmarks and Regulations
| Emissions Category | Current Benchmark | Future Target |
|---|---|---|
| Dust (baghouse output) | < 0.0044 gr/ft3 | < 0.0022 gr/ft3 |
| CO2 (process optimization) | 10%+ reduction possible | Further gains via new fuels |
| VOCs in clean gas stream | Diminished via combustion | Continued improvement |
| NOx in combustion process | Addressed via burner tech | Hydrogen-ready systems |
The main focus is trimming CO2, VOCs, and NOx in the combustion process while reducing residual dust content. Requirements are becoming stricter overall but vary significantly between countries. These principles align closely with Sustainable Construction Green Building Practices Materials and Strategies, which examines industry-wide environmental responsibility approaches.
Next Generation Fuels and Low Temperature Technologies
Perhaps the most exciting developments in sustainable asphalt production involve shifting toward renewable and alternative energy sources. Ammann has been at the forefront of integrating these technologies into practical plant operations.
Wood Dust and Carbon Neutral Combustion
A standout innovation is the wood dust burner, which transforms wood dust from locally available sources into renewable fuel. What makes this burner exceptional is its carbon neutrality. The carbon dioxide released when burning wood is offset by the fact that the tree consumed that same amount of CO2 during its lifetime. The burner has proven effective on multiple Ammann plants and can be retrofitted on existing facilities, making it accessible to operators not ready for a completely new plant.
Biofuels and Alternative Energy
Biofuels represent another important initiative toward reducing fossil fuel reliance. Examples include rapeseed oil, sugar cane based fuels, and tall oil, which is a waste product of cellulose sulphate production. Ammann biofuel burners can also utilize traditional fuels such as natural gas, LPG, light and heavy oil, and kerosene, alleviating concerns for customers hesitant to rely solely on newer fuels. Using these renewable sources conserves natural resources and reduces pressure on landfills.
Low Temperature Asphalt Production
Low temperature asphalt, also known as LTA or warm mix asphalt, is gaining traction across the industry. While conventional asphalt is produced at around 338 degrees Fahrenheit, low temperature processes allow production at approximately 212 degrees Fahrenheit. This significant reduction in manufacturing temperature eases energy needs and lowers emissions. LTA impacts the entire production process, including drying, mixing sequences, and recycling. Ammann has focused its research and development on the complete manufacturing process for LTA to ensure product quality matches conventional hot mix standards.
The Hydrogen Horizon
Looking further ahead, Dr. Peters expects that fuel types such as hydrogen will significantly reduce gas emission values in the near future. These fuels will become increasingly important in the asphalt industry, and Ammann is already working on solutions to be prepared for this transition. These developments complement concepts explored in Everything You Need to Know About Kinetic Roads, where innovative transportation infrastructure is reshaping how we think about sustainability.
Upgrading Existing Plants: Retrofits and Noise Mitigation
Not every asphalt producer needs a new plant to achieve meaningful sustainability improvements. Dr. Peters emphasized that operators might be surprised by how much they can accomplish with existing equipment through targeted upgrades.
Control System Upgrades and Training
A very accessible first step is upgrading the control system. A modern control system like the Ammann as1 significantly improves efficiency across many production processes, reducing fuel usage, emissions, and material waste. Training is equally important. Even the best plant and control system underperform if operators cannot leverage the built-in value. Proper training ensures operators maximize efficiency and minimize waste, making it one of the most cost-effective sustainability measures.
Comprehensive Retrofits
For those seeking more significant improvements, a comprehensive retrofit costs a fraction of a new plant and works with products from Ammann and other manufacturers. Retrofit options include:
- Recycling solutions to increase RAP usage
- Foam bitumen and wax additive systems
- Special bitumen handling and alternative mixing cycles
- New dryers that optimize heat transfer and reduce emissions
- Environmental upgrades to bitumen tanks and baghouses
- Noise reduction solutions
- Revamped burners, mixers, and control systems
Many retrofit customers incorporate a new dryer, which optimizes heat transfer, reduces emissions, and enables use of an expanded range of materials including RAP. The plant owner determines the level of commitment based on specific needs and budget.
Noise Mitigation for Urban Locations
A shortage of industrial land means plants increasingly must locate near residential areas, where local governments have strict noise standards. Ammann offers varied sound-suppression packages, from burner variable speed drives and stack silencers to full plant cladding. An interesting benefit of full cladding is that plants begin to look like commercial buildings that blend into urban office parks, with passersby never guessing an asphalt plant is operating inside.
A Path Forward
From maximizing RAP content and optimizing plant processes to adopting renewable fuels and implementing noise mitigation, every step contributes to a greener industry. The technologies exist today to make significant progress, and companies like Ammann continue to push boundaries. As Dr. Peters noted, requirements are becoming stricter, and the industry is responding with innovation and commitment. The future of asphalt production is sustainable, and that future is already taking shape.