Algae raceways of all sizes and styles need impermeable lining solutions. Yet the sheer size of commercial algaculture raceways makes them difficult to line, especially once you consider the curves and tight corners required for optimal water turbulence. Don’t assume that you’re limited to malleable materials like concrete when lining an in-ground or raised raceway. Concrete is far from the best material, even if it’s necessary for structural elements of the design. You’ll need a material that is truly impermeable rather than slightly porous and prone to seepage over time. Discover what liners work best for algae raceways so you’re not left relining your ponds after just a few cycles.
Why Concrete Isn’t Enough
Concrete may seem like the ideal material for lining a raceway for algae production, but it has many disadvantages when used alone. It does perform well as a structural cover for reinforcing the banks of the pond and preventing damage from the constant circulation and turbulence of the water. However, it’s not impermeable or crack-resistant enough to serve as the primary containment method for the solution. Concrete is a porous material with tiny openings that allow water to soak through its surface and eventually seep out into the soil due to capillary action. Simply adding a layer of flexible and impermeable material from BTL Liners is enough to turn concrete into a reliable and resilient addition to a raceway.
Flexible Liner Advantages
The biggest benefit of choosing a flexible liner is its reliable impermeability. However, it’s far from the only advantage since there are other impermeable materials on the market. When compared to other impermeable liners, flexible polymers like RPE offer advantages like:
- Easier installation than rigid materials that are hard to conform around the curves and sloped edges of a raceway
- Lighter weight for lower shipping costs and fewer handling challenges on the job site
- High crack and slump resistance due to the flexibility of the material; two major issues with both rigid and clay liners
- Ease of replacement if needed in the future.
RPE: The Best Flexible Liner for Algae Raceways
Reinforced polyethylene (RPE) is the best material to choose when shopping for a flexible liner for algae raceways. It’s not just a material recommended for this industry or specific use, but rather one of the top pond liners in general. You’ll find RPE from BTL Liners used to seal everything from high risk waste storage ponds to edible fish farms. Depending on the specific formulation, it’s possible to find RPE liners that are certified for potable water use, which is required for algae grown for human consumption as well as for animal consumption in some areas. UV exposure is a concern for outdoor algae raceways because the harvest process is easiest when the liner is left exposed. RPE can handle 20 years or more of constant daily sun exposure without breaking down or weakening. There’s no need to settle for a heavy or thick liner when this material is surprisingly thin and lightweight. This makes it easier to maneuver into place during installation, reducing labor costs and the total time needed for the work. Few other flexible liner materials can offer even some of the benefits provided by RPE liners.
Other Liner Options and How They Stack Up
You’ll find quite a few other flexible liners sold or marketed for algaculture use, but most of them are poorly suited to raceway installation. In addition to flexible polymer products, you’ll also see some recommendations for designs based on alternative products like bentonite clay or polymer sprays. None of these other options can quite compare to RPE, so it should be your first choice for any algaculture raceway project.
PVC
Polyvinyl chloride (PVC) is one of the materials most commonly recommended for use as a general-purpose pond liner. Being a widely used product doesn’t necessarily make it well suited to the demanding environment of the algae farm. PVC is not designed for exposed use in most cases, and algae raceways are harder to clean when covered with a layer of sand or rough exposed concrete. PVC can also break down in reaction to the lipids and acids released by some algae as they grow. It’s not always easy to find liners made from this material that qualifies as food or fish safe due to its propensity to leach chemicals into the water.
HDPE and LDPE
High- and low-density polyethylene (HDPE and LDPE) are related to RPE, but neither one is quite as good as RPE. HDPE tends to be stiff and harder to get to conform to the curves of an algae raceway. LDPE is flexible enough, but it’s less durable and can react in response to some nutrients you may add for algae growth. If neither contains any reinforcement, they’re generally weaker than RPE. If you want a liner that will last for years, with minimal maintenance, choose RPE over either HDPE or LDPE.
EPDM
The thick sheet rubber best known as EPDM may have once been the only material available for lining raceways, but it’s far from the best choice today. It’s simply too thick, hard to shape, and heavy to use for lining the relatively narrow passages of a raceway. EPDM is also too reactive to many lipids and other compounds found in algae for this kind of use. It remains one of the more expensive liner materials as well, giving it no advantages of any kind over RPE for algaculture use.
CSPE
Chlorosulfinated polyethylene (CSPE) is a highly flexible liner material that is known for being potable water safe, making it a good choice for food production. It also has fairly good UV resistance for exposed installation. However, it’s also very expensive and is known to react with lipids. Many algae release some of their lipids during the reproduction and growth cycle, making reactions likely if this material is used in an algaculture raceway. Considering its high cost, it’s not worth risking a shortened lifespan by exposing it to reactive compounds. RPE can handle high lipid levels and is even used for oil and fuel storage. There’s no reason to choose CSPE for algaculture installations.
Why Choose a Reinforced Liner?
If you’re still not sure what makes RPE different from other polyethylene products, consider its reinforced design. Reinforced pond liners are often only half as thick as other liners made from the same materials. The addition of a reinforcing layer of woven or non-woven material dramatically increases the tear and crack resistance while allowing the use of thinner materials. Thinner liners are easier to spread, but they have to be tough to resist damage over the years. Reinforced liners have a greater lay-flat ability too, which means they spread out quickly and form fewer wrinkles that crack under the pressure of thousands of gallons of water. Reinforced liners are a better choice for all kinds of ponds, but they’re especially recommended for algae raceways.
With this guide to selecting liner materials for algaculture, you should find it a little easier to settle on the right choice for a new raceway. These materials can also work well for bioreactors and other types of algae cultivation equipment, especially if you are experimenting with alternative methods and new designs to take your production to a new level. Work with us here at BTL Liners to create the raceways you need to succeed by starting with the right lining materials.
