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Biochar has been getting a lot of attention for its ability to enhance soil carbon content and help mitigate climate change. But the real question is: just how good is it – and how can we accurately measure how well it works?

That’s something the MASH Makes research and development team is looking into – and the answer isn’t entirely straightforward. 

How biochar affects soil carbon

Recently, our R&D  team looked at how various biochar application rates influence soil total carbon. The results showed a significant positive correlation (R² = 0.95) between the rate of biochar application and the total carbon content in soil samples.

This is great news! It means that biochar is highly effective at increasing soil carbon levels due to its high carbon content, produced during the pyrolysis process. But there's more to the story.

Biochar seems to be doing something fundamentally different from just adding carbon to the soil. While it does boost soil carbon,the real magic of biochar is not only in the soil organic carbon (which is tricky to measure) but also biochar's benefits lie in other areas as well like improving overall soil health and plant growth.

So, while we can see an increase in carbon, that might not be the only factor helping the plants the most.

The challenges of accurate measurement

While our team’s findings are exciting, there's also  a catch. Using large amounts of biochar to significantly increase soil carbon might not be practical in real-world situations. Too much biochar can make the soil too alkaline, disrupting the balance of nutrients and reducing the amount of nitrogen available for plants. So, we need to find a balance – what's best for the plants and what's best for the environment?

This balance is tricky to measure. Traditional methods like the Walkley-Black method, which uses chemicals to oxidise carbon, don’t work well with biochar because its carbon is recalcitrant and can’t be eaten by bacteria. This leads to inaccurate results.

We also tried measuring the total carbon in biochar using the Fertilizer Control Order (FCO) method, which involves checking how much weight is lost after burning it. However, this method didn’t work well because the temperature we used (650-700°C) wasn’t high enough to burn off all the carbon, especially the more stable types like graphite-like carbon that need much higher temperatures (around 800-1000°C) to burn completely. Plus, the burning time of 6-8 hours wasn’t long enough to fully burn the biochar, especially when it was highly carbonised. 

To get a clearer picture, we followed the dry combustion method for CHNS (Carbon, Hydrogen, Nitrogen, Sulfur) analysis. This method measures all types of carbon in the soil, giving us a better understanding of biochar’s impact. One challenge with CHNS is that we need to provide a 1 mg sample and therefore the sampling process can become tricky. We’re planning to study this method further to confirm its accuracy. 

What’s next

The industry needs to take a closer look at the best ways to measure biochar’s benefits. As research continues, advanced methods and field trials will be essential to making biochar application more practical and beneficial for sustainable farming and climate change efforts.

At MASH Makes, we believe in the possibilities of biochar – but we also know there’s still a lot to learn about how it works and where it can have the greatest impact. That’s why we’re conducting several biochar lab studies and field trials at our research and development labs in India. You can read more about our biochar here.