10 JanCurlex vs. Straw
Evaluating Curlex® and Straw Fibers for Erosion Control Blankets
Straw and Curlex are two common fibers for erosion control blankets. Each fiber type has distinct advantages and reasons why end users buy or specify the blankets.
Why choose one instead of the other? Here are some key characteristics to consider:
- Material differences in straw and Curlex
- Performance for short term erosion control
- Performance for extended term erosion control
- Price
Straw Fiber Basics
Straw Blankets are produced from agricultural straw, a by-product of farming operations. Agricultural straw for straw matting must meet quality control standards for age, moisture, length and width. Straw fibers that are too old will decrease the longevity of the straw blanket. Additionally, straw fibers that are too moist will increase the likelihood of mold which diminishes the blanket’s performance.
Fibers that are too short cannot be properly stitched into the fiber matrix. American Excelsior, for example, specifies that 75% of the agricultural straw for the Premier Straw® Blankets must be 4 inches or greater in length.
Straw fibers should also be wide. A wide straw fiber increases surface area, reducing the impact of droplets onto soil, thus reducing soil erosion. Wide straw fibers also protect seedlings and increase absorption which is important for grass establishment. However, if the straw fiber is too wide and the straw blanket too dense, sunlight won’t be able to penetrate through to the seedlings in the soil.
One of the most important qualities of agricultural straw fiber is that it is 100% weed seed free. Erosion control blankets stabilize the soil by creating an established turf system. Before erosion control matting is installed, the soil is seeded. When the seedlings germinate and grow through the erosion control blanket, their roots interlock with the erosion control matting fibers to create a stabilized system. If the erosion control blanket’s fibers contain weed seed, those weeds will choke out the seedlings and prevent the site from establishing healthy turf.
Curlex Fiber Basics
American Excelsior’s patented Curlex fibers are made from 100% Great Lakes Aspen wood fibers. The end of each wood fiber is curled and barbed which distinguishes it from the flat straw fiber.
The curled wood fibers interlock with each other and with the soil to create an intimate connection. This allows Curlex erosion control blankets to further connect with the ground, intertwine into the root system and reduce soil erosion.
Similar to the minimum standard length for straw fibers, American Excelsior specifies 80% of Curlex fibers for Curlex I blankets should be six-inches or greater in length. This ensures fibers are properly stitched together, evenly distributed through the entire surface area and of consistent thickness.
Also similar to straw matting, Curlex blankets are made exclusively from naturally seed free fibers to eliminate cross contamination between the erosion control blanket and the grass seed on site.
A key differentiating factor between straw and Curlex is Curlex fibers don’t float. Wet Curlex fibers swell and interlock to form a strong fiber matrix. This creates intimate soil contact and forces water to flow over the fiber matrix (rather than under). Excelsior fibers also successfully retain moisture, which improves vegetation establishment. This means when your construction site is hit with a major rain event, the excelsior fiber blanket clings to the soil so that water flows over the blanket, soil is retained and the erosion control blanket does not float.
Short Term Erosion Control Performance
“Short term erosion control” can vary widely depending on who you ask. In general, we consider short term up to 12 months.
You have several products to choose from for short term erosion control matting including:
- Curlex NetFree
- Single Net Straw
- Single Net Straw All Natural (biodegradable netting)
- Double Net Straw
- Double Net Straw All Natural (biodegradable netting)
It is important to note that estimated longevity is an estimate and how long an erosion control blanket performs on site is subject to installation, wear and tear and site conditions.
Cross compare our five short term erosion blankets below.
| Key Properties | Curlex NetFree | Single Net Straw | Single Net Straw All Natural | Double Net Straw | Double Net Straw All Natural |
|---|---|---|---|---|---|
| Netting | No netting | 1 degradable polypropylene | 1 biodegradable jute | 2 degradable polypropylene | 2 biodegradable jute |
| Functional Longevity | 3 months | 12 months | 12 months | 12 months | 12 months |
| Slope Application | Flat and up to 3:1 | Up to 3:1 | Up to 3:1 | Up to 2:1 | Up to 2:1 |
| Channel Flow | 3.0 ft/sec | 4.5 ft/sec | 4.5 ft/sec | 7.0 ft/sec | 7.0 ft/sec |
| Shear Stress | 1.0 lb/sf | 1.55 lb/sf | 1.55 lb/sf | 1.75 lb/sf | 1.75 lb/sf |
| Soil Loss Ratio (event-based RUSLE C factor) | 0.063 | 0.05 | 0.05 | 0.05 | 0.05 |
Extended Term Erosion Control Blankets
Extended term erosion is generally defined as 15 – 24 months of estimated functional longevity on site, subject to site conditions.
Choose from the following products for extended term erosion control:
- Curlex I CL
- Curlex I
- Curlex I FibreNet (biodegradable netting)
- Curlex II CL
- Curlex II
- Curlex II FibreNet (biodegradable netting)
- Straw/Coconut Blanket
- Straw Coconut All Natural (biodegradable netting)
Cross compare our eight extended term erosion blankets below.
| Key Properties | Curlex I CL | Curlex I | Curlex I FibreNet | Curlex II CL | Curlex II | Curlex II FibreNet | Straw/ Coconut | Straw/ Coconut All Natural |
|---|---|---|---|---|---|---|---|---|
| Netting | 1 polypropylene | 1 polypropylene | 1 biodegradable jute | 2 polypropylene | 2 polypropylene | 2 biodegradable jute | 2 polypropylene | 2 biodegradable jute |
| Functional Longevity | Up to 15 months | Up to 18 months | Up to 18 months | Up to 18 months | Up to 24 months | Up to 24 months | Up to 24 months | Up to 24 months |
| Slope Application | Up to 2:1 | Up to 2:1 | Up to 2:1 | Up to 1.5:1 | Up to 1.5:1 | Up to 1.5:1 | Up to 1.5:1 | Up to 1.5:1 |
| Channel Flow | 5.0 ft/sec | 7.0 ft/sec | 7.0 ft/sec | 7.3 ft/sec | 9.0 ft/sec | 9.0 ft/sec | 8.5 ft/sec | 8.5 ft/sec |
| Shear Stress | 1.60 lb/sf | 1.75 lb/sf | 1.75 lb/sf | 1.80 lb/sf | 2.25 lb/sf | 2.25 lb/sf | 2.0 ft/sf | 2.0 ft/sf |
| Soil Loss Ratio (event-based RUSLE C factor) | 0.039 | 0.018 | 0.018 | 0.050 | 0.022 | 0.022 | 0.15 | 0.15 |
Straw Blankets are Cost Effective for Short Term, Temporary Erosion Control
As you can see above, straw blankets are best for short term applications unless combined with coconut. Despite being designed for short term applications, Single Net Straw Blanket is the most common and the most affordable erosion control blanket we sell in Virginia.
Our Single Net Straw Blanket is VDOT Approved for EC-2 Type 1 Matting and meets VA DEQ design criteria for Treatment 1 Soil Stabilization Matting. This base-level erosion control application is very common on Virginia projects and might include low-velocity channels, shoulder stabilization, and mild slopes not steeper than 3:1 grade.
Installing Single Net Straw Blankets for temporary erosion control in these applications is simply the most cost-effective choice.
Curlex Blankets Provide Superior Erosion Protection than Straw Blankets
Straw blanket may be the popular and budget-friendly erosion control matting, but it does not always meet the standards for many construction sites. Curlex blankets, on the other hand, provide superior erosion control but come at a slight increased cost to the consumer.
Since curled and interlocked Curlex fibers create an intimate soil connection and don’t float in hydraulic events, Curlex blankets have a major performance advantage over straw blankets. Curlex® is the preferred performance choice when you need erosion control matting for channel flow applications like ditch bottoms, on steeper slopes and in areas subject to higher erosion stress.
In the comparison tables above, you will see that the Curlex blankets have a lower Soil Loss Ratio C-Factor than the straw blankets.
Event-based RUSLE C factor calculates the soil loss ratio which is the total amount of soil lost to water erosion from the test plot relative to a bare soil plot under the same conditions. A lower soil loss ratio translates to less soil mass lost to erosion. Curlex II’s C-Factor is .022, or 99.978% reduction in soil loss by the Curlex II blanket compared to Double Net Straw’s .05 or 99.95% reduction in soil loss. While this example doesn’t present a significant difference, it demonstrates Curlex’s performance superiority compared to straw. Use the C-Factor to compare erosion control blankets of varying materials and manufacturers.
Two Great Erosion Control Blankets: what does your application require?
Both Straw Blankets and Curlex® Erosion Control Blankets successfully control erosion, prevent soil loss, and revegetate construction sites.
It is not a question of which fiber is better, but which fiber is better for your application?
If you need assistance with selecting the right blanket for your application, contact our sales team. We can provide you with pricing and technical data that relates to your site so that you can make the best decision for your project.