The Case for Biochar
By Gavi Welbel
We can store carbon from the atmosphere, rebuild degraded soils, increase plant yield, invigorate our urban tree canopy, filter stormwater, remove toxins from the air and soil, and upcycle waste. All this can come from biochar: a special type of charcoal made from wood waste, nutshells, and other organic waste material.
Stockholm is already doing it. Minneapolis is working on it. San Francisco, Norway, and other champions of sustainability across the world are investigating and implementing this time-tested—yet newly rediscovered technology—called biochar. Biochar is organic material that has been burned so it looks and feels similar to the charcoal you might have in your grill. It can be created from green and brown waste materials through a process called pyrolysis, in which the waste material is burned in the absence of oxygen. The resulting products can include biochar, bio-oil, and synthesis gas, which is a mixture of hydrogen and carbon monoxide and can be used as a fuel. Depending on the conditions in which pyrolysis occurs, different proportions of biochar, bio-oil, and syngas are produced. Maximizing biochar production has been shown to have great climate change mitigation potential because it literally breaks the carbon cycle. Rather than letting wood and plant waste naturally decay in a matter of days or years, releasing all of the plant’s carbon into the atmosphere as gaseous CO2, much of the carbon is stored in a stable solid form for up to 100,000+ years.
While significant research is still needed to confidently determine the co-benefits of biochar as a soil amendment or low-impact development material, we know one thing for sure: biochar slows greenhouse gas emissions . We need to start cranking it out—locking plant carbon before it cycles back into the atmosphere. Then, we can find places to put that biochar. Luckily, there are plenty of places to put it, including agricultural or garden soils and green infrastructure . Increasing crop yield, reducing fertilizer costs, improving green roof longevity: These are factors that can incentivize potential biochar buyers. Unfortunately, because biochar can have a wide range of effects depending on source material, production mechanism, and application, research is often too unreliable for potential users to feel confident in their purchase. No matter what, consumers should feel confident that they will be contributing to climate change mitigation if sourced responsibly. Carbon credits, however, have not successfully been integrated into American economics, so creating a biochar market has posed a challenge. This lack of profitability has also slowed research urgency and progress so we are stuck in a conundrum.
Biochar production can happen in large-scale high tech machinery that costs upwards of $500k, but it can also happen in low-tech, small-scale technology such as the Kon-Tiki Open Flame Curtain Kiln, which only requires an initial investment of about $1k. The Kon-Tiki Kiln still produces low-emissions, high quality biochar, outputting about 200 kg of biochar in 5 hours. The cost is so minimal in the scope of farm equipment investment that such technology could “represent a promising possibility for sustainable rural biochar production”. Still, to allow farmers to put in the labor of collecting wood waste and firing the kiln there must be sufficient economic incentive in at least one of three forms: carbon tax credits, market retail (to other farmers or urban uses), or increased crop yields.
Further, biochar production and use is aptly suited to be integrated alongside other climate change mitigation strategies including afforestation/reforestation (using tree prunings, nut shells, and other resulting wood waste materials as biochar feedstock) and enhanced rock weathering (using basalt and biochar as soil amendments promoting soil carbon sequestration). All three of these mechanisms: biochar, afforestation/reforestation, and enhanced rock weathering have been reported as necessary and viable systemic changes for limiting climate change below the critical global warming threshold for a safe and habitable earth.
Scientists agree that we need to capture and store carbon at unprecedented levels. Climate change mitigation must take on all hands on deck approach—we no longer (and haven’t for a long time now) have the leeway to try out a few different strategies, slowly implementing what works best. We must do everything we can to cut down the amount of CO2 in our atmosphere right away. Biochar can be an affordable multi-beneficial strategy to capture carbon before it hits the atmosphere. We have to take that chance—we must take it carefully looking at biochar from a systems perspective to make sure it is sourced, produced, implemented, and used in a way that sinks more GHGs than it does create, and doesn’t have other harmful effects. Right now, we can be confident that if done responsibly—based on guidelines already established in the literature—biochar is an effective way to sink carbon. As we continue to use and study its implementation, we will better understand the potential to increase soil fertility, plant yield, water retention and water filtration.
There are feasible steps we could take to create those economic incentives. We could push policy to expand carbon capture tax credits (45Q exists right now), rely on existing research to push municipalities, urban foresters, and low-impact development projects to invest in biochar, rely on existing research to push farmers to invest in soil-rebuilding biochar, and fund further biochar research to more reliably demonstrate co-benefits.
If we don’t take bold steps toward mitigating climate change and building resilience, people will die. People are already dying due to the impacts of anthropogenic climate change. Once biochar becomes mainstream as a soil amendment and/or low-impact development material, there could be a cascading effect; there are nearly limitless applications, but we need to get the ball rolling.
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