The team at Planetary is grateful for the engaged participation of the Nova Scotia community regarding our work. We recognise that there are many perspectives at play in the community and aim to target our responses to the “curious and concerned citizen”. We also recognise that some groups of people (e.g., activists, scientists, etc.) may be interested in a more detailed answer or wish to explore a different facet of the topic, and we invite you to continue to reach out to us with additional questions.

 For questions not specific to our Nova Scotia project, please see our general FAQs about Planetary’s process.

  • What is planned in the next phase of field trials taking place over the summer of 2024? What are the risks associated with this ongoing trial work and how are you mitigating those?


    This ongoing study has been designed in conjunction with Dalhousie University to maximise the amount of knowledge we can gain while minimising all risks. Building off the work done leading up to and including the first field trial event in 2023, the second phase of this trial is projected to take place over the summer and fall of 2024. Iterating on all the prior work done, we will be undertaking thoughtful improvements that will allow for:

    Longer duration trial with increased monitoring 

    This year’s trial will run from July to December, with breaks for analysis and maintenance scheduled throughout. We’ll use a new alkalinity source with a lower carbon footprint and test new on-shore equipment for safer and more efficient handling. We have expanded and upgraded the suite of sensors we’ll use to monitor the outfall and our alkalinity addition point to increase data collection.   

    Additional alkalinity testing 

    Like last year, we’ve hired an independent verification, testing, and certification lab to analyze samples of the alkalinity we’ll use before adding it to the outfall. This year, we’ve added another series of tests to increase the confidence level of results, raising the overall certainty of carbon removal measurements and environmental safety.

    Increased community involvement

    We are working in collaboration with Carbon to Sea (CtS), Centre for Ocean Ventures and Entrepreneurship (COVE), Dalhousie University on a Joint Learning Opportunity Initiative (JLO). The JLO’s goals are to provide a mechanism and funding to advance and evolve complimentary, OAE-focused research and development for the planned 2024 field trials. This includes accepting proposals aimed at local communities that are exploring Indigenous Traditional Knowledge Systems with the goal of evolving our collective understanding of MRV.

  • Tell us more about this new alkalinity source being used for this trial.


    The alkalinity for this trial is produced by Magnesitas Navarras in northern Spain. The primary component of this material is magnesium oxide (MgO), which when mixed with water into a slurry creates magnesium hydroxide (Mg(OH)2). Magnesium hydroxide is a common antacid used both medically (primary ingredient in Milk of Magnesia) and in wastewater treatment, and is the same compound we used during our 2023 field trial. The material is loaded onto a container ship in Barcelona, transported to Halifax, and stored in a warehouse until it’s ready to be used. The carbon emissions for every step of the material’s production and transportation are accounted for.


    We selected this alkalinity for 3 main reasons: 

    1. It has a low carbon footprint, so we can be sure that when accounting for all the steps required to add it to the ocean, this alkalinity can result in significant net negative carbon emissions – in other words – even greater net carbon removal. 
    2. It readily dissolves in seawater, meaning it will rapidly neutralize the CO2 and begin removing carbon from the atmosphere, rather than sinking and accumulating on the seafloor. 
    3. It has low concentrations of impurities (i.e. other metals), so we can be confident that our diligent monitoring will not reveal any negative effect on water quality or biological systems during the trial.
  • What uncertainties and/or risks need to be dealt with before you scale up your project?


    To Planetary, “deployment scale” means that we are operating at a full and safe capacity for ongoing continuous operations. We can envision that time in the future, but it is still a number of years away. We will only ever reach full operational scale when we are confident that the benefits to the climate, the ocean, and the community far outweigh any small and manageable risks that have not yet been eliminated.

    There are 3 main risks and uncertainties, posed here as questions, that must be addressed before we move to deployment scale, not only in Nova Scotia, but at any of our project sites:

    1. Is this process actually resulting in net atmospheric CO2 removal?
      This answer has several components. First, any activity will emit some CO2, which needs to be considered. We will develop a high degree of confidence, combined with independent verification, of the total CO2 that our projects emit, all the way down to the emissions used to make the probes that we use for our measurements. Next, using real ocean measurements, we’ll demonstrate that the process is working. For example, we’ll need to show, with evidence, that alkalinity in certain parts of Halifax Harbour is ‘enhanced’, or increased, relative to the background concentration. Finally, we’ll share the results of numerical models that clearly indicate how much CO2 removal occurred because of the alkalinity enhancement. One specific risk here is that after alkalinity is added, the waters sink to the deeper ocean before completely absorbing the atmospheric CO2 as intended. Measuring that will be extremely challenging, so we will rely on high-quality models to estimate this potential ‘loss’ and work to minimise the uncertainty associated with that estimate. The methods themselves, and the results they provide, will be validated by third parties. Multiple, well-established ocean models are used and (in Nova Scotia) one of the critical numerical models is run by our Dalhousie colleagues – this particular model is well-known across the ocean science community as being of high quality.
    1. Is this process having any negative impact on the local ecosystem?
      Our approach to carbon removal is particularly promising because (in theory) it does not directly impact the biological system. However – nature is complex – so we must look very closely for any indirect impacts. Lab-scale experiments assessing biological impacts both here in Nova Scotia and around the world are very encouraging, and this diligent, university-driven science must continue as we begin to move into the field. To some degree, this search for impacts must be conducted across the entire ecosystem, but we will also follow the scientific community to target our search on the most critical and logical groups of organisms. Planetary’s approach here aligns well with the latest literature: we must closely monitor:

      • Particles (which can change the light environment)
      • Impurities (some of which can be harmful at high levels)
      • Acidity level or pH (we deacidify on purpose but need to stay within safe bounds)
      • The seafloor (where particles and metals might accumulate).

      Additionally, multiple research groups are conducting independent studies into potential biological impacts, including ecosystem-wide impact using measurements of environmental DNA within the ocean water, as well as targeted sampling of both microscopic plankton and mussels present in the vicinity of the Tufts Cove site. For more information on the types of research being conducted both around the world and here in Halifax, you can visit the Dalhousie-led Alk-Align project website and the Joint Learning Opportunity information page.

    2. Is the community generally supportive of deployment?
      Getting to deployment will take multiple field trials over multiple years, and communities must be with us every step of the way. We want to be very clear – there is not yet any agreement in place to deploy this process at scale in Halifax. At this time, we are investigating whether it might be technically feasible for that to be considered. In addition to technical capability and regulatory approval, we are committed to working with the communities here in the area to determine whether this process should be deployed, and, if so, under what conditions.Planetary trusts that our process will be successful at reaching our goals of healing the ocean and restoring the climate – as well as delivering the many potential benefits to the community – but if the collective decision of local people is that the process should not be deployed here, we would not move forward.

Archived FAQ

Planetary will always answer community questions to the best of its current knowledge. However, our understanding of our project sites is improving over time, and our answers may shift based on new scientific data or newly published research. When this happens, we may update our responses to FAQs on this page.

To maintain transparency, we have preserved previous versions of FAQ responses, and these can be read below.

  • Are there risks related to September’s field trial? How are you mitigating them?


    The current study has been designed in conjunction with Dalhousie University to maximise the amount of knowledge that we are able to gain while minimising all risks.

    The study began with a literature review to identify any risks and challenges that might be known based on other studies. We then conducted a series of in-the-lab experiments to answer fundamental questions such as:

    • Exactly how much carbon dioxide is taken up by seawater given various concentrations of various alkalinity types?
    • How quickly does this carbon uptake happen?
    • At what amount of alkalinity addition does the process become less efficient?

    Answering these questions with our academic partners at Dalhousie University and the University of Miami contributed significantly to our XPRIZE Milestone award in April 2022. These ‘beaker-scale’ experiments are critical and continue to be an important part of our work today. 

    To better simulate real ocean alkalinity addition, and to test out measurement capability using real ocean sensors, we conducted experiments in the Dalhousie Aquatron – Canada’s largest university aquatic research facility. Along with these experiments, our partners at Dalhousie University also conducted experiments on phytoplankton to understand the safe local limits on the part of the ecosystem most likely to be affected. The collaboration between the Planetary and Dalhousie research teams has produced the necessary foundational data to advance this project to the next stage – a small-scale field trial. This trial will help us gain a better understanding of the potential of this climate and ocean restoration solution in the Halifax area. 

    Whenever considering risks, we need to compare the risk of action to the risk of inaction. Namely, what will happen if we don’t move forward with this project? Climate change continues to intensify – causing additional damage to the oceans. The consensus is that we need to act now – and act carefully – to successfully balance the urgency of action with the safety of a well-designed study.

    One important part of the study design is its size. We know that the effects of an addition of Magnesium Hydroxide (MH) are temporary – the environment reverts to its previous state after an addition as the tides quickly dilute it and wash it away into the open ocean. We have purposely kept the addition amount small and the timeframe short.

    There are three potential risks that we have identified:

    •  If the addition of alkalinity leads to cloudiness of the water for an extended period, it can impede the growth of plankton. We plan to add the MH at a specific rate that is very far below the rate at which such clouding would occur.  Additionally, we will very carefully monitor the water for any clouding, and we will pause the study if any clouding does occur.
    • All natural minerals have the potential to contain other trace elements, which, if added in too high a concentration, may have an adverse effect on local plants and animals. We address this risk in two ways. First, before the material (a natural form of MH, called brucite) was shipped to the study site, we conducted an elemental analysis on the material to ensure that it meets environmental quality standards. Second, during each addition, we will monitor the local environment to determine if the trace metals in the area have increased. If we approach any limits, we will pause the addition.
    • If there is a buildup of alkalinity on the seabed, there is a small chance that organisms living there could be affected. To address this risk, we are starting with a baseline MH addition rate of less than 0.01% of the cooling water flowrate. Secondly, we will regularly scrutinize the seabed using cameras to look for any buildup. Finally, we will regularly take samples of the seafloor and measure the particles for alkalinity.