Biochar is often hailed as a miracle material but how stable is it, really?
For decades, black carbon (biochar) was assumed to be almost indestructible in soils, locking away atmospheric carbon for millennia. A new study challenges that view, showing that biochar is indeed stable, but not invincible, and its fate depends on both how it’s made and how it’s measured.
How are samples measured?
Samples are measured using coulometry with different front-end units:
- TOC (Total Organic Carbon): Coulometer and a furnace at approximately 600 °C
- TC (Total Carbon): Coulometer and a furnace at approximately 1000 °C
- TIC (Total Inorganic Carbon): Coulometer and an acidification unit
In this study, biochar degradation was monitored with precision using UIC Inc. carbon analyzer coulometer systems, which electrochemically titrate absorbed carbon until a spectrophotometric endpoint is achieved. These instruments provided the sensitivity needed to distinguish microbial versus abiotic oxidation over the course of a year.
The big reveal:
Biochar does break down, but very slowly. Across a range of biomass types and charring temperatures, long-term models predict carbon half-lives ranging from hundreds to tens of millions of years, depending on production conditions. While microbes played a role, abiotic oxidation alone accounted for a surprisingly large fraction of carbon loss.
What was done and what was found:
Researchers produced biochars from six biomass types, pyrolyzed at multiple temperatures. Incubations were run with and without microbial inoculation, and CO₂ release was tracked using UIC Inc. coulometers. Results showed that:
- Biochars made at lower temperatures were more labile.
- Fine-grained chars degraded faster than coarse ones.
- Abiotic oxidation contributed between 50–90% of the microbial signal.
Implications:
These findings redefine our understanding of carbon sequestration. Biochar is indeed long-lived, but its persistence is strongly influenced by production methods. For policymakers and soil managers banking on biochar as a carbon sink, precise measurement, as enabled by UIC Inc. systems, is essential to quantify its real climate impact.
Takeaway:
Biochar is not a silver bullet, but when properly made and tracked with advanced tools like UIC Inc. carbon analyzer coulometers, it offers a powerful way to stabilize carbon for centuries to millennia. If we are serious about reversing climate change, measurement precision is not optional, it’s the foundation.
Reference: Zimmerman, A. R. (2010). Abiotic and microbial oxidation of laboratory-produced black carbon (biochar). Environmental Science & Technology, 44(4), 1295–1301. https://doi.org/10.1021/es903140c
