With so many promising uses for algae, it’s a wonder that the commercial algaculture industry is still relatively new and small. Yet, there is no shortage of challenges making it hard for new business owners to expand into the world of algae production. Despite being pervasive and hard to control in the wild, algae are surprisingly tricky to get to thrive in an enclosed setting. Many of the world’s largest and most productive algaculture facilities have nonetheless experienced major die-offs with confusing or unknown causes. Understanding the challenges that must be overcome for algae to flourish is the first step in designing any raceways or other cultivation facilities.
Light Control
As with other chlorophyll containing plants, algae rely on light to internally generate the sugars it needs to feed itself. Those sugars also turn into the proteins, lipids, and other compounds that make algae so valuable as a product. Unlike most plants, algae species often have the capacity to grow almost infinitely with the right amount of light. There’s no need to expose some types of algae to darkness to stimulate correct growth or fruiting. This means that algaculture may require supplying artificial light at night to maximize production. Other alternatives include using photosensitive species that do require periods of darkness to take better advantage of natural light sources or choosing algae that don’t require light at all.
Temperature Requirements
Microalgae, like phytoplankton, are particularly sensitive to temperature. Even macroalgae, like seaweed, prefer warmth and go dormant or die in cold temperatures. This largely limits algaculture to the warmer parts of the world or to indoor heated facilities. If a quick growing species is chosen, an outdoor and unheated facility that only operates during the warmer months may be a feasible operation. Most microalgae species prefer temperatures between 65 and 85 degrees F. Exposure to temperatures below or above these ranges will either damage or kill off most species, especially those of high value for food or fuel purposes.
Nutrient Supply
Since the typical bioreactor or raceway will have a much higher concentration of algae cells than the standard open waterway, it’s necessary to add nutrients to stimulate the rapid growth desired. Like other plants, algae require nitrogen, phosphorous, and potassium for rapid growth and reproduction. Yet, adding nutrient solutions to the water for algae growth can quickly eat into the profits of a venture or make it cost more than it produces. Low cost or even free sources of nutrients can include manure sludge, fertilizer runoff, and even stormwater drainage collections, depending on the composition of the water and the specific needs of the algae.
Genetic Testing and Isolation
When developing new and unusual strains of algae for highly specific applications, genetic isolation is essential. Algae love to mix and even cross to create strains that may not be appropriate for the intended use. Many cultures are not as isolated as they could be and should be further refined before being released into a larger raceway or bioreactor system. Designing multiple, separate tanks or ponds is essential to ensure that related but separate types of algae don’t mix and create a contaminated final product.
Constant Circulation
Since algae need to stay exposed to sunlight to photosynthesize, the water in any algaculture pond or tank must stay constantly moving. Without constant mixing and stirring, the majority of the algae will fall below the well-lit surface and grow slowly or not at all. This kind of circulation is accomplished in different ways depending on the culture method. Bioreactors tend to be designed to take advantage of either gravity flow or centrifugal forces to keep the algae swirling and moving. For raceways, paddlewheels and circular designs that encourage flow work together to keep a uniform mixture. Paddlewheels are some of the lowest power circulation options, but they still require a steady supply of power to ensure that the water doesn’t go still and settle.
Contamination Risks
With many algae stocks being used for animal or human consumption, the development of the wrong species or the introduction of a contaminant from the water supply could cause serious damage. Unlined raceways and ponds are particularly risky because they experience contamination both ways. Water can enter from the environment through the soil and carry along chemicals or minerals that are unsafe for consumption, or the nutrients from the algae solution can leach out and cause issues in the environment. Lining all raceways, ponds, and tanks with an impermeable barrier is the best way to prevent these problems.
Harvesting and Processing the Algae
The single biggest challenge of algae production, on a commercial level, is the harvesting stage. Algae in an open pond or raceway is generally only concentrated at 1 gram of plant matter per 1 liter of water. In contrast, bioreactors often achieve concentrations as high as 20 grams per liter of water. No matter the original concentration or density, all algae solutions require concentration and then dewatering to produce the desired sludge or solid cake product. While it might seem simple to just filter or seine out larger macroalgae species, fine phytoplankton that produce the most biomass are much harder to separate from the solution they’re grown in. For algae grown specifically for oil production, companies have reported 30% or more of costs were directly related to harvesting and dewatering. Harvesting methods for commercial algaculture include:
- Flocculation to cause the algae to clump together and settle at the bottom, either through CO2 starvation or the introduction of a powdered agent
- Filtration with a series of screens designed to trap as much of the algae as possible
- Aeration or flotation methods that use air bubbles to force the algae to the surface for skimming or filtration
- Dewatering methods like centrifugal spinning, conveyor belt screening, and even electric pulse systems designed to separate water from algae particles.
All harvesting and processing methods require a lot of energy, which is one of the biggest reasons algaculture has been limited commercially. As new technologies emerge to reduce the cost and time required by this stage of production, algaculture is sure to grow in scale and profitability.
Despite these challenges, many algae species represent some of our best chances at improving food, fuel, and feed production around the world. It’s worth solving the issues that interfere with productive commercial algaculture so the industry can grow to meet changing demands in the future. While we can’t solve all the problems related to algae cultivation, here at BTL Liners we can help with pond and raceway building. Check out our reliable and food-safe liner products to find one that is perfect for any kind of algaculture facility.
