The Shortest Route to Reducing Road CO₂? A New Method to Combat Cracks in Snowy Regions: Algae Oil Makes Asphalt More "Flexible"

An Unexpected Answer to the "Usual Reason" Winter Roads Break

For those living in snowy regions or areas with extreme temperature fluctuations, roads in early spring often look the same. Cracks form a network, water seeps in, freezes and expands, melts leaving gaps, and eventually turns into potholes. Cars bounce, pedestrians are at risk, and municipal repair costs soar.

To alleviate this "winter debt" even slightly, researchers have introduced a new material. Instead of mixing roads with tires or plastic, they are using... "algae (microalgae)." According to Phys.org (an article provided by ACS), an asphalt binder made from algae-derived components has shown potential to reduce cracking at sub-zero temperatures and increase durability. Phys.org

The "weakness" of asphalt is that the petroleum-derived "glue" hardens

Asphalt pavement maintains its shape by binding aggregates like sand and crushed stone with bitumen, a sticky substance derived from crude oil. It expands on hot days and contracts on cold days—this flexibility to follow expansion and contraction is crucial. However, when it cools rapidly, the binder becomes brittle and prone to cracking. Once cracks form, water enters, and repeated freeze-thaw cycles quickly worsen the damage. Phys.org

This research targets the "problem of hardening in the cold" by creating a sustainable binder with "rubber-like" properties from algae oil, aiming to enhance performance in low-temperature ranges. Phys.org

Evaluating Four Types of Algae Oil to Select the Most Promising

Interestingly, the research team did not jump straight into experiments. They evaluated four types of algae-derived oils using computational models to assess whether they would mix well with the solid components of asphalt and maintain functionality at freezing temperatures, before proceeding to testing. Phys.org

The most promising result came from oil derived from the freshwater green microalgae Haematococcus pluvialis. This oil showed positive trends in resisting permanent deformation (rutting damage) under stress simulating traffic loads and in resisting moisture-induced damage. Phys.org

In Simulated "Freeze × Traffic" Tests, Deformation Recovery Improved by Up to 70%

In lab demonstration tests that repeated cycles of "traffic loading" and "freezing and thawing," algae asphalt using H. pluvialis showed up to 70% improvement in deformation recovery compared to traditional petroleum-based binder pavements. Additionally, at sub-zero temperatures, it resulted in fewer cracks than petroleum-based binders, which is the key point. Phys.org

The important aspect here is that instead of "just hardening," the focus is on enhancing the flexibility and recoverability needed more in colder conditions. In cold regions, if the pavement is too soft, it ruts in summer, and if too hard, it cracks in winter. Algae-derived binders offer an alternative in this balancing act.

CO₂ Reduction Impact: 4.5% Reduction with 1% Replacement, Potential for "Carbon Neutral" with 22%

Not only performance but environmental figures are also presented. According to the research team's estimates, replacing just 1% of petroleum-based binders with algae-derived binders could reduce net carbon emissions from asphalt by 4.5%. Moreover, if approximately 22% could be algae-derived, it could theoretically approach carbon neutrality. Phys.org

Of course, this is also the point most likely to spark debate. Carbon neutrality can only be solidified by evaluating the entire lifecycle, including "how the algae are grown," "energy used for oil extraction and modification," "transportation," and "whether the pavement lifespan is truly extended." The numbers should be read as "potential indicators." American Chemical Society

Implementation Challenges: Scale, Cost, Standards, and Evaluation of "Heat Side"

The research side envisions a path to "high-performance, cost-effective, sustainable paving infrastructure." Phys.org

On the other hand, there are several points of discussion for implementation.

• Raw Material Scale: Roads require massive quantities. How can algae oil be supplied stably, at what price, and through which supply chain?

• Manufacturing and Mixing Process: Can it be handled within the viscosity and temperature range of existing asphalt plants, or is modification necessary?

• Long-term Durability: How long can performance be maintained under real-world conditions like UV, oxidation, repeated loads, deicing agents, and oil stains?

• Performance in Hot Seasons: Even if strong in winter, will rutting and flow resistance in summer decrease?

• Standards and Certification: For use in public works, compliance with standards and adoption decisions by the client are necessary.

The current achievement demonstrates "promise in sub-zero performance," and the next desired step is data from the field (actual roads).

SNS Reactions: Voices of Expectation and Scrutiny of "Numbers Behind"

This topic is not confined to the laboratory. In a LinkedIn post by Elham Fini (under the name Ellie Fini), who leads the research, it was highlighted that the paper was featured on the cover of ACS Sustainable Chemistry & Engineering, emphasizing an approach to "predict the compatibility of bio-oils using molecular-level indicators (polarizability)," gathering reactions and comments. LinkedIn

In the comments section, there are praises such as "impressive as a sustainable material" and "layering science on infrastructure leads to a greener future." LinkedIn

On the other hand, whenever this kind of "green material × infrastructure" becomes a topic on social media, certain points of discussion almost always arise.

• "Can it be mass-produced?" (Supply volume and price)

• "Does it really reduce CO₂?" (Criticism of LCA assumptions)

• "What about other environmental impacts?" (Land, water, chemical processing, industrialization side effects)

• "How long does it last?" (Pavement is all about longevity)

The combination of praise and demands for verification is actually healthy. Since roads are a social infrastructure, "interesting material" alone will not lead to adoption. The challenge is to break down performance, cost, workability, safety, and environmental impact into terms that can be explained in practical language.

Still, the "Next Norm" Suggested by Algae Asphalt

The value of this research lies not in "mixing algae makes it eco-friendly," but in the ability to directly address the failure mode in cold regions (low-temperature cracking) through material design. Moreover, by incorporating computational models into material exploration, narrowing down candidates, verifying through experiments, and even presenting hypotheses for emission reduction. Phys.org

If the loop of breaking in winter, repairing in spring, and breaking again in winter can be eased even slightly, it will impact driver safety, municipal budgets, and ultimately CO₂ emissions. Whether the day will come when algae save roads depends on the next field data.

(Reference: DOI 10.1021/acssuschemeng.5c03860 / Funding noted as supported by the U.S. Department of Energy)