Seaweeding Algae & Seaweed Growing

What is a Bioreactor for Algae & Why You Might Want One

what is a bioreactor for algae

Algae is an excellent source of vitamins, nutrients, and minerals. But purchasing dried algae from the local health store can be a very costly experience for anyone. In order to reduce the overall costs and enjoy the many benefits of including algae in a regular diet, more and more people are choosing to grow their own algae at home.

On your mission to grow your own algae, you may have heard about a bioreactor for algae, or algae photobioreactors or even macro algae reactors. Talk about intimidating terms, like something you might hear in relation to a nuclear power plant rather than seaweed!

So, in this article we dive into what an algae bioreactor is, and reasons why you may (or may not) want to build one for yourself.

What is a Bioreactor for Algae? Overview

Algae photobioreactors or a macro algae reactor (macro algae = seaweed) are really just fancy names for systems or setups used to grow algae. However, in most cases, we are talking larger-scale systems than a simple fish tank in your lounge room, and you’re more likely to come across the term in industrial, educational or commercial applications rather than home seaweed growing.

That’s not to say you can’t build your own bioreactor for seaweed growing at home, it’s just that you will hear the terms used more often in larger-scale algae projects.

Starting an algae growing venture at home starts with the proper planning and development of your very own photobioreactor or PBR. You can build your own, and they can be built in a number of different ways, depending on what type of seaweed or algae you are attempting to grow.

So, let’s take a closer look at the different types of algae bioreactors available today.

Open vs Closed Systems

Open System. An open system is the simplest form of bioreactor for algae. It consists of nothing more than a pond open to the environment. Thus, the term open system. An example might be if you decided to grow seaweed in a fishpond or disused swimming pool in your backyard.

Closed System. On the other end of the spectrum, is what’s known as a closed system. Closed systems are closed to the surrounding environment, and are exclusively regulated and controlled by the owner. An example might be a closed aquarium or tank in your home or garage.

Which type of algae photobioreactors are best?

To ensure that your algae is safe for human consumption, it’s important to grow it in a closed photobioreactor. These enclosed systems allow you to control the lighting, temperature, pH levels, and nutrients that are made available to the plants.

Our instructions for growing brown seaweed (kelp), as well as growing spirulina at home, both utilize a form of enclosed system as they use a controlled indoor aquarium environment. The video links at the bottom give good instructions for how to build a home photobioreactor closed system for growing algae.

Benefits of a closed bioreactor for algae/seaweed

Maybe you’ve wondered whether you can just toss some edible seaweed you harvested from the seaside into an old swimming pool outside and simply let nature do its propagation thing (an open system) – after all, that’s how it happens in the ocean, right? Kind of.

Although there are many benefits to operating both a closed and opened system, here are the top reasons for choosing to build your own closed photobioreactor instead:

  • Prevents Contamination
  • Control over pH Levels
  • Control over Light Levels
  • Control over Carbon Dioxide Levels
  • Control over Temperature Levels
  • Reduced Water Evaporation
  • Low Carbon Dioxide Losses
  • High Cell Concentrations
  • Can Be Grown in Any Environment or Climate

Advantages & Disadvantages of a Closed Macro Algae Reactor

While there are a number of advantages to building your own closed system algae photobioreactors, there are also many disadvantages. The biggest disadvantages of building your own system at home really come down to the size, scope, and overall cost. But generally speaking, the advantages far outweigh these in the long run.


There are many excellent benefits to building your own closed photobioreactor at home. Not only will you save a lot of money by growing your own colonies, but you will ensure that your algae is safe for consumption.

#1 Contamination Prevention

Contamination prevention is at the top of the list of advantages for building and growing your own algae at home in a controlled, closed system. Open ponds are problematic, to say the least. Because it is hard to control the environment around them, they are more likely to be susceptible to a wide variety of contaminations. Not only can plants and animals find their way into the open ponds, but pollutants in the air can also settle on the water. By building a closed-system photobioreactor, you’re able to prevent the possibility of contamination.

#2 Climate Controlled

Let’s face it, not everyone lives somewhere where the conditions are just right for growing algae year-round. For those who live further north, it may never get warm enough to grow algae in an open system. Closed systems, on the other hand, can be made relatively cheaply and allow you to control the environment. This ensures that a smaller closed system can be built inside of a home, garage, or even on a porch.

#3 Quality Control

When you have control over all of the inputs, you also control the outputs. By taking control over every aspect of your colony’s growth, you can ensure that the end product is of the highest caliber. You will be able to ensure that your photobioreactor gets a consistent supply of UV light every single day. You can ensure that the pH levels of the water are maintained accordingly. And more importantly, you can provide just the right amount of nutrients needed for your colony to bloom and expand.

#4 Evaporation Management

One of the biggest disadvantages of an open system is evaporation. During the dog days of summer, there is a greater chance of losing the vast amount of water within an open system purely through evaporation. The smaller the system, the greater the effect that this evaporation plays. When you operate a closed photobioreactor system, you are able to reduce the amount of evaporation to a more manageable level.

#5 Carbon Dioxide Management

Some people choose to build their own algae photobioreactor simply to control the amount of carbon dioxide in the atmosphere. After all, algae survive by consuming carbon dioxide and sunlight, and multiply, releasing oxygen into the environment. When you operate your own photobioreactor, you’re able to manage the release of carbon dioxide into the environment and funnel it directly into your colony.

#6 Higher Concentrations

Perhaps the biggest advantage of building a closed-system photobioreactor is the increase in cell concentration. A closed system puts you in full control over the growth of your colony, and therefore allows you to provide the perfect conditions for growth. As a result, even a simple DIY photobioreactor is capable of having higher cell concentrations than any open system.


As with all things, there are both advantages and disadvantages to operating your own macro algae reactor at home. The biggest downside to starting any project is size, scope, and of course, cost.

#1 Cost

The biggest cost of building an advanced photobioreactor comes down to the cost of the acrylic tubes used in large corporate and university-scale projects. But it’s important to remember that not all photo bioreactors need to be built using clear acrylic tubes. In fact, thanks to experimenters from around the globe, the cost of building a photobioreactor has become increasingly more affordable.

#2 Size and Scope

For the most part, the development of photobioreactors has been limited to laboratory environments. In recent years, large commercial-scale production has seen an increase. It’s now not uncommon to see large-scale photobioreactor systems connected to modern power plants around the world.

But for those wanting to grow algae at home, the size and scope of these larger, commercial-grade installations can be overwhelming. In order to produce enough algae for home consumption, a well-thought-out plan must be developed first.

Video Source: Save the planet – Algae bio reactor diy system (YouTube)

Additional Video Resource: ALGAE Photo-Bioreactor (Episode 1: Initial Build) by Dansville (YouTube)

Final Thoughts

We hope you’ve found this article to be a valuable introduction to the world of algae bioreactors, and in particular, the benefits of building a closed system if you are planning on growing algae at home.

The main takeaway message is probably, don’t try and grow edible algae outside exposed to the environment (open system), if anything just for the risk of contamination – you will never know 100% what you are eating. In a closed system, you can control it, however.

If you’re curious to learn the steps for growing algae at home in a simple DIY closed system reactor, have a look at the video links above. Alternatively, try your hand at growing some brown algae (kelp) at home with these steps.

Happy Seaweeding!