Biochar
The Good, The Less Good, The Yet to be Studied
CDR News
A new study on the absolute NEED for removals
Tech receiving “gold standard” removal status
Great video interview with Danny Cullenward on This is CDR via The Open Air Collective.
Nerd rating: 3 (1 to 10 scale on the technical density of the post)
Biochar Benefits and Challenges
I will keep it short this week, as I’ve had a full plate. I wanted to hit the high-level basics of biochar and provide some insight into its strengths and challenges going forward.
Benefits
Not going to reinvent the wheel here, and as always, I will continue to rely on and communicate the most relevant research in the area. The below figures are from this paper which is a meta-analysis. This figure shows:
Selected parameters with highest agronomic relevance that were investigated in the 26 reviewed meta-analyses. The mean overall effect size (% change) and 95% confidence intervals are given as reported in the original studies. The numbers in parentheses indicate the number of pairwise comparisons used for that specific parameter
So as shown, biochar can increase plant productivity, crop yield, photosynthetic rates, water use efficiency, plant-available soil water, root biomass, root length, etc. It is important to note that the application of biochar reduces nitrogen leaching and emissions, another climate benefit.
The positive agriculture aspects of biochar are measurable, demonstrated, and backed up by several scientific studies.
There are removal benefits as well. Biochar removes carbon at two points in the process, one being the decomposition of the biomass in an oxygen-deprived environment and the next when applied to the soil. The first essentially elongates the degradation process of biomass, stretching it out over a more extended period of time, and the second increases a soil’s ability to stabilize organic matter, including carbon. Further expanded upon in the great CDR Primer
By enhancing soil quality, such as by raising pH, biochar application can increase crop yields (Spokas et al., 2012; Jeffery et al., 2017; Crane et al., 2013) and carbon return to soil, thereby further increasing soil carbon storage (Whitman et al., 2011). In this way, biochar can potentially form a positive feedback loop: increasing biomass growth and further increasing carbon sequestration.
The potential for yearly removals is varied but encouraging from 0.03–6.6 GtCO2-eq yr–1 by 2050. This range is due to constraints like food insecurity, habitat loss, land degradation, and estimated technical abatement. These numbers are from the linked IPCC paper.
Noting some feedback I received last week, I will place two quotes on the potential for biochar below—both from Albert Bates with the US Biochar Initiative. The first quote speaks to the different sectors and use cases of biochar, some outside removals. The second to the potential of usage for biochar. This is not necessarily an endorsement of the comments but a reasonable faith effort to show a different side of the argument.
Biochar strengthens concrete 30%, for instance, and reduces the requirement for sand. It is also valuable in electronics, dyes, batteries, water filtration, mold-control and much more. Soil application may be its lowest value proposition. Likewise it would be a great waste to pump bio-oil or volatile gases into geological storage when those can form industrial cascades as bioplastics, composites, polymers, chemicals and epoxies, and also have soil chemistry applications.
When all the potential uses for biochar at a profit are taken into account (ignoring carbon offset subsidies), its limiting factor is only the availability of photosynthetic-origin feedstocks. As Kathleen Draper and I describe in detail in BURN: Using Fire to Ignite a New Carbon Economy to End the Climate Crisis if you factor in future marine algae farming and kelp forestry wastes, municipal sewage and rubbish, wildfire mitigation, and step-harvested agroforestry, the potential for annual sequestration for biochar is likely to be well above 50 GT CO2.
Challenges
Like all other CDR pathways, biochar needs more research to understand the mechanisms for removal and verification of the carbon removal itself. A complete life-cycle analysis of biochar is necessary to understand the emissions associated with pyrolysis relative to the feedstock, the sequestration value of the biochar (in all uses cases), and the effect of the biochar on other GHG emissions like nitrous oxide or methane.
There is some evidence1 to suggest that the application of biochar over surfaces decreases the albedo of that surface, increasing the sunlight absorbed and heat absorbed. Albedo is an expression that relates to a material’s ability to reflect sunlight or heat. Dark surfaces absorb more sunlight and thus heat, and light surfaces reflect it. Click the link above for a more in-depth look at how albedo influences climate change.
For biochar to play a prominent removal role as we advance, there must be more studies into the permanence of the sequestered carbon. We must first discover exactly how much carbon is removed once biochar is applied and then the length that carbon stays removed. As of now, most of the studies have been in labs and greenhouses.
There is no one-size-fits-all for biochar. The research above will depend on the available feedstock, soils, crops for application, regional climates, elevations, and hydrology in a particular study area. This heterogeneity makes it difficult to standardize a removal across a marketplace or through private procurement.
Some groups are working on this, and Verra has developed a methodology that “provides a framework for quantifying emission reductions and removals from:
Improved waste handling practices that result in the production of biochar from feedstock biomass;
Certain non-soil material applications such as cement or asphalt.”
Finally, cost, which is and will continue to be a challenge for all CDR. The cost breakdown can be considered relative to two modalities—the cost of creating the biochar itself and the price of a ton of carbon removed. Current mean costs of biochar production range from $96-$1,834/ton2 of biochar. Costs for biochar to become viable via removals are anywhere from $30-$120/ton CO2, with some of the difference being explained in the biomass production method (dedicated vs. waste).
Final thoughts
Biochar, first and foremost, has demonstrated value in many important plant physiological processes. If the price comes down and the education on that fact becomes more robust, farmers across the globe can use it for all the benefits mentioned above. Alongside this usage, and others noted by Albert above, biochar can remove some carbon.
However, biochar is an incredibly complex removal proposition. We need to continue to study the ability of the material to remove carbon across soil and plant types, hydrologies, climate zones, and any other motivating factors. We need to know precisely how much carbon is being released and how long it is staying removed. The quantification and ongoing MRV associated with biochar will write its future as a removal. Notwithstanding, this is true of every single CDR technology.
Next week: BECCS: More than just a soccer hero
Learn
Microsoft’s latest lessons learned from removals
Follow
@JesseJenkins, the man made it on John Stewart!
@Carbon_Direct expertise in all things carbon
@airminers got a removal idea? Go here
Verheijen, F.G.A., et al., 2013: Reductions in soil surface albedo as a function of biochar application rate: Implications for global radiative forcing. Environ. Res. Lett., 8, 044008, doi:10.1088/1748-9326/8/4/044008.
https://www.sciencedirect.com/science/article/abs/pii/S0306261918312558