I don't want to use plastic!!

### The Environmental Impact of Geosynthetics: A Closer Look at Microplastics

As a design engineer concerned with the environmental implications of the materials we use, I often find myself questioning whether the geosynthetic products employed in our projects contribute to the growing problem of microplastics. Let's delve into the potential for microplastics from polymer-based civil engineering products.

#### Understanding Microplastics

Microplastics are generally defined as plastic particles smaller than 5mm but larger than one micron. Anything smaller falls into the category of nanoplastics. Microplastics can be categorized into two types:

- Primary Microplastics: These are intentionally manufactured at small sizes for specific applications, which doesn’t apply to civil engineering products.

- Secondary Microplastics: These result from the breakdown of larger plastic items. This is where our focus lies when considering the impact of civil engineering products.

#### Civil Engineering Products and Their Microplastic Potential

The types of polymer-based civil engineering products we're discussing include:

- Geogrids for soil reinforcement in mechanically stabilized earth (MSE) walls and embankments

- Geogrids for pavement stabilization

- Civil engineering fabrics

- Erosion and sediment control products

These products are integral to infrastructure development, but do they contribute to microplastics in the environment? We believe they do not, and here's why.

#### Degradation of Polymer-Based Products

Polymer-based products, or geosynthetics, primarily degrade in two ways:

1. Physical Abrasion: When these products rub against other surfaces, causing small pieces of plastic to break off.

2. Chemical or UV Degradation: When the product degrades internally due to chemical reactions or UV exposure, leading to small pieces breaking off.

We can further classify these products based on their use: below ground and above ground.

##### Below Ground Use

The majority of geosynthetics are used below ground. Geogrids and engineering fabrics are typically buried, meaning they experience minimal physical abrasion after installation. These products are designed for long lifespans, often exceeding 100 years, with no significant abrasion. At the end of their design life, they can be recycled, making them environmentally friendly. For example, drainage composites, which use a small amount of polymer per square meter, can replace large quantities of quarried rock traditionally used for drainage. By engineering these products for durability and placing them where they are not exposed to UV light or physical wear, we can prevent them from generating microplastics.

Chemical degradation mechanisms like hydrolysis and oxidation are also controlled when these products are buried, protected from sun and rain. Any potential degradation is addressed during design with polymer additives or reduction factors, ensuring the product's longevity.

##### Above Ground Use

Above-ground applications of geosynthetics present different challenges. Common uses include:

1. Temporary Erosion Protection on Construction Sites:

   - These products usually have a design life of six months to two years.

   - If used above ground, they risk abrasion and UV degradation.

   - To mitigate this, we use UV-protected products and employ calendering (a process where heat rollers bind fibers together, preventing them from breaking off).

2. Erosion Control Matting:

   - These mats often use biodegradable materials like coconut fiber, which degrade completely when they break off.

   - Some mats include a UV-stabilized polymer backing for soil stabilization.

   - These products are designed to avoid creating microplastics, using biodegradable or UV-stabilized materials.

When geosynthetic products are used appropriately, particularly by embedding them into the root zone rather than the foliage zone, they remain out of sunlight, further reducing the risk of degradation and microplastic generation.

#### Conclusion

It's crucial to distinguish between single-use plastics and engineered long-term plastics. The geosynthetics we use in civil engineering are designed to last over 100 years and are carefully engineered to prevent microplastics from entering the environment. These materials not only avoid contributing to microplastic pollution but also offer significant environmental benefits by replacing large quantities of natural resources and reducing carbon footprints. By understanding and addressing the degradation mechanisms of these products, we can ensure their sustainability and minimal environmental impact.