Providing certainty in CO2 accounting for photobioreactors

September 26th, 2023

Harnessing new microalgae technology for long-term, verified carbon sequestration

Project duration: July 2023–December 2024

Image: DALL·E with prompt- a close up of bioalgae growing in a photobioreactor. two thirds of the image is the bioalgae, the remaining third is separated by a glass tube and the external lab

Project lead

Dr Anusuya Willis

Dr Anusuya Willis

Research Scientist


Jim Williams, Alasdair Currie and Jacques Malan.


Photobioreactors (PBRs) grow high densities of microalgae for biomass harvesting and extraction of high-value products that are used in aquaculture, research, food production, stock feed, pharmaceutical, biochemical and biotechnology applications.

Recently, microalgae growth in PBRs has also been proposed as a carbon sequestration path. The excess biomass created (~90% with no current use) has the potential to be transformed into carbon-sequestration products (e.g., green concrete, bio-bricks) or material suitable for burial and long-term storage such as biochar.

Microalgae only capture and store a small proportion of CO2 for photosynthesis and, currently, PBRs don’t have the capacity to precisely account for the CO2 input into the system and its transfer to biomass. This requires a PBR with continuous monitoring and control of available dissolved inorganic carbon, pH, and O2 in the water, and controlling the system for complete CO2 uptake. Accurate CO2 accounting in PBRs is a critical step in developing microalgae products for long-term carbon sequestration via photosynthesis. Our previous research designed a carbon control and accounting module for PBRs (InCIRT) but it remains untested. If successful, the technology provides an opportunity to incorporate carbon sequestration into microalgae biomass production and generate high-value products (including intellectual property) for commercialisation.


We’ll build and test the InCIRT module to optimise its use, and confirm the accuracy of the carbon uptake and conversion to biomass in a PBR that’s controlled via the module.

In the first phase we’ll build the prototype and develop the programming for running the InCIRT. Phase two will thoroughly test the parameters of carbon uptake in a PBR running the module, and assess design programming needs to optimise monitoring and control.

The aim is to generate a patented protype InCIRT module for commercialisation that has the ability to account for complete CO2 capture through a closed-system PBR. This will enable verifiable carbon capture from waste microalgae biomass and a viable option for fast carbon sequestration (given algae growth and photosynthesis rates are much faster than land plants). Ultimately, the InCIRT module will provide certainty in CO2 accounting and the ability to offer verified Australian carbon credit units (ACCUs) on the carbon offset market.


The challenge is to design a new type of bioreactor where the algae capture all CO2 and none is lost back to the atmosphere. We’ll address this challenge by providing a route for monitoring and accounting for the CO2 input into the system via the InCIRT module. While PBRs may not provide carbon sequestration on a large scale, relative to other technologies, they do provide options for smaller-scale, verifiable carbon capture, which translates to high-value ACCUs.