This blog post comes courtesy of Claude Abraham, Ph.D. candidate in electrical engineering. Claude posed the question.
“Tom, I have been following your work in biochar, especially with regard to concrete. With all the studies on this why has it not caught on?”
This is a very good question and answering it with any degree of certainty is very difficult. One could point to economics, lack of familiarization, a marketplace just in its infancy, technical limitations and more. What makes biochar so interesting is that it has many different applications. The challenge so far is that while biochar has found a place in applications such as concrete, blacktop, water, and soil remediation it has yet to find itself in an area where it excels over existing technology.
As with a lot of new technologies the knee jerk reaction to jump on the environmental bandwagon is often rudely awakened with the harsh realities of real-world application and what engineers call mass balance.
In the case of biochar and concrete, the euphoria of discovering that biochar strengthens concrete in a lab environment does not by itself overcome the technical and economic realities of successful commercial application. When Dr. Liu L. Lin, the inventor of Glanris 901X biochar asked me to join him in launching the technology, concrete was an application that he and many others had already looked at extensively. In our opinion the obstacles to commercializing biochar concrete moved this application down in the list of priorities for possible success. Whether my beliefs were/are correct or not, I do not know as many in the industry are still working in this arena. However, I will list the reasons that I personally believe that biochar concrete is at best a small and difficult market.
- Extreme amounts of water required when mixing biochar concrete.1 – Findings have varied but in general compared to standard concrete it requires an extra liter of water per kilogram of concrete produced.
In the university lab, dealing with small volumes such a consideration goes unnoticed. However, to the fence installer who uses 80 pounds of concrete for each fence post this specification has a major impact. 80 pounds of concrete calls for an extra 36.4 liters, or 9.61 gallons of water.
Green technology you say? In a time when water shortages are becoming the norm and not the exception, how sensible and green is a technology that requires significantly more water to implement? Can you imagine how much more water road and building construction will require?
But wait, no pun intended, that 9.61 gallons of water per fence post? The additional water required adds 80 pounds to the concrete needed for a single fence post. Now, translate that to the construction industry. A typical cement truck delivers 8 cubic meters. At 1,440 kg per cubic meter, a truck will deliver 11,520 kg of product. If it is a biochar product the added water requirement will add roughly 25,400 pounds to each 8 cubic meters delivered. This added weight requires additional transportation fuel costs, which translates into more fossil fuel and more carbon emissions. Green, you say!
- The diverse varieties and versions of biochar make standardization for the cement/concrete/mortar applications in construction, in my opinion impossible.2
When we speak about biochar we must first ask, “what is the source of the biochar”. Is it rice husk, corn stalks, grape vines, sawdust, wood chips or other? Then, if it is corn stalks we have settled on, do corn stalks from Iowa behave the same way corn stalks from Ohio do? Enter variable #2. Pyrolysis Temperature greatly affects things like pore size and carbon content. What temperature do we settle on?
Enter variable #3, particle size. Cement products work best when aggregates have specifically engineered particle sizes. To achieve a uniform particle size biochar must undergo some type of grinding. Easy enough, however, when we grind biochar to a more uniform particle size, we change the pore size of the biochar, thereby changing the effects it has in the finished product. Add to this that crop biochar is friable and crushes easily. The consistency of particle size of biochar leaving the plant is likely to be less consistent after the media has been packaged, loaded onto trucks, transported and then unloaded at the shipping destination. Conversely, sand doesn’t change no matter what is done to it.
Let me introduce you to potential problem #4, weight. No, not the water weight, we already covered that. I am speaking about the weight of the media. In my experience with rice husk biochar we found the basic material weighed approximately eight pounds per cubic foot, and the powdered form weighed about 35 pounds. Conversely, sand weighs about 90 pounds per cubic foot.
How is that a problem you ask? It will require somewhere 2.5 – 12 times the volume of biochar to replace a similar weight of sand or other aggregate. The problem here is that for any given amount of cement mix, it is going to require 2.5 – 12 times as many shipments of biochar to achieve the same weight. Again, dramatically higher transportation, fuel and labor costs associated with biochar present a huge obstacle to making market sense. These emission producing elements involved here also detract from, if not negates the idea of being carbon neutral.
- There is growing skepticism about the environmental safety of biochar, and its actual carbon sequestering ability once placed into the environment. Multiple major university studies have called for more real-world studies to be done before the environmental benefits can be touted to the public.3
- Unexpected physical and mechanical properties also may cause skepticism to market acceptance4.
- Studies have found that biochar can make concrete less permeable. This would minimize CO2 sequestration as the gas could not easily penetrate the surface of the concrete.
- By decreasing concrete density and using a media that has air-filled pores and is naturally hydrophobic, some biochars have been shown to make concrete buoyant. Such a concrete could “float” up from wet soil during rain. This would be a safety issue by creating unstable foundations.
- Some biochar decreases the ductility of concrete.
- The research into the longevity and durability of biochar concrete related to long-term exposure to sulphates, chlorides, acid, oil, grease, seawater, and other chemical challenges are very few
As the founder of a biochar company and a patent holder on the chemical regeneration of pyrolyzed rice-husks I have a vested interest in this technology. A a man of science however, I have lived to see more than one dead end for technologies that were introduced to save the planet. Windmills, solar panels, cars that run on water, and electric vehicles stand as prime examples of green technologies that have fizzled into technical impotency once applied to the real world and forced to compete with existing technologies.
While I am not placing such a pronouncement on biochar cement, for the reasons listed in this article and a few others, I don’t see a future where it becomes a staple of concrete/cement ingredients.
Scientists create technologies that pull. Zealots on the other hand take science hostage and push their wares. The challenge that all new technologies face is not in the limitations in the scope of their applications, but instead in the inability of those promoting these technologies to accept those limitations.
Biochar has a place in our world. In my opinion the reason it has yet to catch on is because the biochar community refuses to take the time to define where that place is, but instead frantically tries to force it into commercial success.
- https://www.sciencedirect.com/science/article/abs/pii/S0961953418303039 ↩︎
- https://www.sciencedirect.com/science/article/pii/S0958946523002780 ↩︎
- https://www.geoengineeringmonitor.org/2023/08/growing-concerns-about-biochar-safety-and-carbon-markets/#:~:text=A%20review%20of%20259%20studies,producers%20is%20on%20the%20rise. ↩︎
- https://www.researchgate.net/publication/275479004_Mechanical_Properties_of_Mortar_Containing_Bio-Char_From_Pyrolysis ↩︎