The Permanence of Biochar Carbon Removal (BCR)

At Carbo Culture, we believe permanence must be a prerequisite for carbon removal, as it is crucial to prevent the return of CO2 to our atmosphere. New research has proven biochar carbon removal is one of the safest and most permanent carbon dioxide removal (CDR) methods available.

This article explains how we know that carbon will stay sequestered in our biochar. We will also answer questions like what is carbon removal permanence, how is the permanence of biochar carbon removal measured, and how long the carbon will remain sequestered?

Longer permanence leads to higher value for the atmosphere and the credit

The permanence of carbon removal reflects the duration for which the carbon remains stored and avoids re-entering our atmosphere. It is also called “durability” or “long-term storage” of carbon. In the context of carbon dioxide removal (CDR) and climate change, carbon removals should have durability that matches the shelf-life of carbon emissions in the atmosphere (300-1000 years).

As a result, long-term permanence is considered extremely important for the validity of carbon removal credits. Consequently, solutions that can store carbon for 1000s of years are highly sought after and have a higher value in both the voluntary and compliance markets as buyers of carbon credits can be sure that the carbon is safely stored.

How can the durability of biochar carbon removal be assessed?

For biochar carbon removal, permanence refers to how long the carbon remains stored in the biochar. Depending on the pyrolysis process some biochar is more permanent than others. The industry has coined the term Biochar Carbon Removal (BCR) to clarify which biochar can be used for permanent carbon removal. Today’s industrially produced BCR is chemically and structurally extremely stable, has permanence levels way beyond 1000 years, and complies with strict monitoring, reporting and verification (MRV) schemes. There are several evidence-based methodologies for measuring the permanence of carbon in biochar, so let’s take a closer look. 

Traditional methods of measuring biochar permanence

The permanence of biochar carbon removal is often measured by using artificial methods to attempt to age and degrade a biochar sample. These experiments have a lot of value and can show the difference between more durable chars from pyrolysis and less stable chars made with low-temperature methods. 

 

The figure above shows the amount of carbon remaining from a few key lab results. A few key points are:

• Biochar made at higher temperatures shows barely any degradation relative to biochar made at lower temperatures.
• Biochar is much more permanent than fresh biomass.

However, researchers typically conduct experiments to collect this data over only 1-2 years. They then extrapolate these results to estimate durability at 100 or even 1000 years. This inherently generates a lot of errors and inaccurate claims. Additionally, many of the biochar used in these experiments are made with lower process temperatures and have much higher Hydrogen:Carbon ratios, which is a proxy for how pyrolysed biochar is.

The results from these experiments have created an inaccurate skew on the permanence of good commercial biochar carbon removal.

The higher the reflectance, the more permanent the biochar is

New research takes a geologic approach to solve this issue. Random reflectance (Ro) is an established method used to determine the maturity of sedimentary organic matter. Recent reflectance studies have shown that fully carbonised biochar created in high temperatures of over +550 °C mainly consist of fractions with the same structure as inertinite. Inertinite is a highly carbonised organic material found in nature that is thousands to millions of years old. Inertinite started as an organic material and was converted into a stable material through various natural processes. It has a random reflectance of >2%. Therefore, biochar with a random reflectance rate greater than 2% is considered geologically stable, and we can expect to find it down in our earth’s crust millions of years from now. Our Carbo Culture biochar also falls into this highly permanent category.

Most importantly, as seen in the figure below, biochar has three fractions: liptinite, semi-inertinite, and inertinite. Liptinite (Ro <1.2%), will degrade in short time horizons, semi-inertinite (1.2% < Ro <2%) will degrade at much longer timescales, but the inertinite fraction (Ro >2%) will remain persistent. Different types of biochar will have different proportions of these fractions. Biochar with a Ro greater than 2% is considered inertinite BCR and the inert fraction of the biochar can be used for permanent biochar carbon removal (BCR).

This new analysis allows for the full categorisation of any biochar, where one can determine its quality by analysing the portions with different reflectance.

Permanent carbon storage

In general, any type of biochar can have various environmental benefits, e.g. improving soil health and reducing nutrient leaching. However, high-temperature, industrially produced biochar that is scientifically proven to be inertinite is the only reliable and permanent carbon storage. Only these types of permanent biochar should be called biochar carbon removal. The reflectance rate is a perfect test to verify which biochar is which and how much permanent carbon there is.

We are committed to producing only the most permanent type of biochar that is scientifically proven to contain only inertinite. If you are interested in the permanence of BCR or BCR credits please contact one of our experts:

 

Hanna Ojanen, Head of Carbon Markets and Policy
Matthew Mallory, Product Manager