Figure: A schematic illustration of the overall process of deploying terrestrial biomass into an anoxic storage. 

The process is limited to lignin-rich terrestrial biomass—plant materials that naturally resist decomposition in low-oxygen conditions. By placing these materials in scientifically verified storage sites within national maritime jurisdictions, carbon can be sequestered for 1,000+ years. Strict site selection criteria, requiring location-specific ecological data, and supported by advanced oceanographic modeling and robust monitoring practices, ensure effective durable storage of carbon. 

The fundamental goal is to create a stable, long-term carbon storage solution that mimics natural conservation processes in the deep sea. By leveraging the unique physical and chemical characteristics of anoxic marine basins, this methodology offers a promising pathway for removing atmospheric carbon. 

Key Benefits of OSB

The OSB methodology provides potential co-benefits, Sustainable Development Goals (SDGs): 

1. SDG 14.c: Enhancing the conservation and sustainable uses of ocean and their resources by implementing international law as reflected in the United Nations Convention of the Sea (countries making progress in ratifying, accepting and implementing through legal, policy and institutional frameworks). 

2. SDG 11.6: Reduced adverse environmental impact of cities (related to agricultural and biogenic waste). 

3. SDG 9.4: Improved sustainability of industries (with increased resource-use efficiency). 

Environmental and Social Considerations

1. The methodology introduces safeguards and monitoring processes for effectively managing environmental and social risks. 

2. The limitations on eligible biomass sources and strict storage site selection criteria aim to avoid negative impacts. 

3. Scientifically robust characterization of the marine ecosystem, as well as efficient communication with relevant local stakeholders are key factors in ensuring the safety of operations. 

Please note that when the requirements set in the methodology are followed, negative impacts to people or the environment can be effectively avoided, minimized or mitigated. 

Period of Consultation 

The public consultation will be open 15 January – 5 February 2025.
We welcome feedback from all stakeholders during this period. Your input is invaluable to our methodology development process, ensuring transparency and informed decision-making. 

Consultation Documentation 

Puro Ocean Storage of Biomass Methodology, Edition 2025 Version 1 (Draft) 

Public Consultation Feedback Form 

 
Webinar 

Date: January 22nd at 16h00 GMT /8h00 PST / 11h00 EST 

The OSB public consultation webinar will cover key aspects of the process and will be recorded. Please sign up for the webinar and submit questions or topics you wish us to cover during the webinar using this form. 

Please download the consultation documents and submit your feedback to contact@puro.earth using the provided form. 

Your insights and expertise will help us refine and improve this groundbreaking methodology for durable carbon removal. We look forward to your participation in shaping the future of ocean-based carbon storage solutions. 

Frequently Asked Questions

1. What is an anoxic basin? 

In the context of this methodology, anoxic basins are considered as permanently oxygen-depleted marine basins, where oxygen-depleted bottom waters do not mix with the oxygen-containing surface waters. Importantly, these non-mixing conditions are created by physical barriers, e.g. vertical basin walls, and high water-density difference which keeps the heavier water (higher density) at the bottom. These conditions must be stable to ensure the safety and durability of the storage over time. Please note, that there are other types of anoxic water bodies, which are not considered stable/permanent conditions and do not meet the eligibility requirements in this methodology. 

2. What is permanence on stored carbon based on? 

Carbon from biomass is lost when bacteria and microbes decompose it. They need oxygen to be able to live. Oxygen-free areas in the ocean do not support most life forms, although microbes and bacteria may thrive in those conditions as well. Decomposition of lignocellulosic biomass in anoxic (oxygen-free) basins is generally negligible, since most of the released carbon will stay in the bottom waters. The permanence is maintained over time since the oxygen-free bottom waters have limited to no mixing with other ocean currents. When both the biomass eligibility and the storage site criteria set in this methodology are met, the 1000-year permanence is possible. 

3. What is the risk for carbon losses and/or reversals? 

We separate the concepts of carbon loss and carbon reversal.

Carbon losses are known and accounted for in the methodology. Carbon losses may occur when the decomposition products of the biomass (such as CO2, nitrous oxide and methane) reach the oceanic layers where they can mix with the surface waters and return to the atmosphere. Losses are the fraction of the stored carbon which is measured to be lost and is accounted for in the CORC calculation. However, the volume of losses is expected to be extremely low due to the properties of the eligible anoxic basins, which act as natural safeguards against losses. The projects must demonstrate the measured fraction of carbon losses by experimental data. 

Carbon Reversal is an event which cancels, entirely or in part, the effects of an issued CO2 removal certification (CORC). Reversal is an unaccounted-for event resulting in a situation where at least a part of the removed, quantified and certified carbon represented as a CORC is either released back into the atmosphere (re-emission) or can no longer be considered safely and durably stored. 

In this methodology, the rules ensure that the risk of reversal is minimized and support the overarching rules of the Puro Standard General Rules should the unlikely situation of a reversal event. 

4. How are environmental risks assessed and avoided and / or mitigated? 

By limiting the scope of the methodology to lignocellulosic, terrestrial biomass into anoxic basins, many environmental risks are avoided, minimized or mitigated. The methodology requires a comprehensive Environmental Risk Assessment and specifies certain key environmental risks which must be accounted for. 

 Additionally, the methodology sets strict criteria for monitoring identified environmental risks. While anoxic basins are generally not productive, the changes in the microbial communities must be monitored, as well as any potential negative impacts to the ecosystem on a larger scale. Overall, the monitoring requirements set robust, science-based end-to-end monitoring and reporting criteria. 

5. Why is this methodology limited only to terrestrial biomass?

While marine biomass, such as seaweed, holds promise as a feedstock for carbon removal pathways, certain challenges still exist especially regarding carbon accounting. Furthermore, especially for cultivated marine biomass, there are additional ecosystem risks to address. 

Marine CDR approaches are still novel and evolving. This methodology will also be updated when new scientific evidence emerges, and the biomass type scope may potentially be broadened in the future. 

6. Why is this methodology limited only to anoxic basins? 

The lack of oxygen, little to no water column mixing and lack of complex life forms in anoxic basins limits potential ecological impacts and dramatically reduces the risk that the sequestered carbon will recirculate back into the atmosphere. 

The storage type scope may be broadened when new scientific evidence emerges, potentially allowing for other storage types to be added. However, other storage conditions may have their own specific environmental risks and potential for re-emissions, which need to be evaluated separately. 

7. What would be an example of an eligible approach in the context of this methodology? 

An eligible approach would include collection, pre-processing (such as baling), transporting and sinking a batch of eligible biomass into a suitable anoxic basin, such as the Black Sea or the Orca Basin in the Gulf of Mexico. 

Essentially, eligible biomass, such as wood residue or agricultural residue, is abundant globally, and without intervention, would either be left to decompose or burn, releasing the carbon back to the atmosphere. Thus, sinking the biomass will keep the carbon content in the biomass stored for 1000+ years.