By Hugh McLaughlin, PhD, PE — Lee Enterprise Consulting, Inc.
Special to The Digest
Biochar is an emerging market; growing rapidly, still in its infancy, but with gigaton market potential when we, as in humanity, start addressing the climate crisis. Activated carbons are a mature market of about one million tons annual production, which is growing slowly. They are basically like fraternal twins; they have a lot in common, they share the same world, and they are different.
First, let’s explain the basic difference between THREE materials: activated carbon, charcoal and biochar. Activated carbon, also known as activated charcoal and several other ‘active/activated source-material’ names, all come down to the implication of the modifier ìactivatedî. When used in conjunction with adsorbents, ‘activated’ refers to a small set of processing techniques that increase the internal microporosity of the original carbon-rich source material. All ‘activation’ processes remove individual carbon atoms and create individual nooks and crannies in the carbon-rich material, which are the adsorption sites. The key to activated carbon is that it is optimized for specific adsorption application (water, vapor, certain adsorbates, etc.) and the adsorption capacity is packed into as dense a material as possible to minimize the volume of adsorbent necessary. In the end, activated carbon is an adsorbent ñ intended to remove something, typically organic compounds, from either vapor or liquid streams.
Biochar vs charcoal
In contrast, Charcoal is a fuel that is used for cooking and other heat generating applications and created by heating biomass, typically wood, under conditions of limited oxygen. In general, charcoal burns hotter and with less smoke than the starting biomass, and also can convert mineral ores to the corresponding metals, inspiring a series of ages: bronze, iron, etc.
Biochar is made in the same manner as charcoal, but it is intended for utilization as an adsorbent and/or a soil amendment. Basically, the key is the end use of the material. It is charcoal if it is intended to be used as a fuel; hence it is manufactured with optimal fuel properties. In contrast, if the intended use is adsorption or as a soil amendment, then it is manufactured to a different set of properties and labeled biochar. As a result, biochar shares properties with activated carbon and charcoal, but has a few unique features that distinguish it from both.
While biochar shares adsorption properties with activated carbon, it also exhibits a significant amount of ion exchange capacity, a property that is minimal or absent in traditional activated carbons. The ion exchange property, which is usually measured and reported as ‘cation exchange capacity’, is due to residual carboxylic acid functionalities on the biochar graphitic backbone. Since activation removes any residual side chain aliphatic groups, activated carbons have reduced ionic interactions.
The other big differences between biochar and activated carbons are bulk density and mechanical hardness. Activated carbon is intended for applications where packing as much adsorption capacity into a fixed volume is paramount, like gas masks and fixed-bed adsorbers. In addition, activated carbon can be regenerated and reused in many applications, so mechanical hardness (also known as the lack of friability) allows the carbon to be moved without falling apart or breaking down in particle size.
If one combines the lower adsorption per unit weight of biochar with the lower bulk density, the resulting adsorption capacity on a volume basis is 1/6th to 1/12th that of high quality activated carbons. For this reason, biochar is typically used in applications where the material is spread out on the ground, so low density is not a disadvantage. In fact, in soil applications, where an important property is the ability to capture excess precipitation and retain it, the low density of biochar translates into additional voids that can fill when it rains.
Biochar is a material that is preferred when several of its unique properties can be exploited in the same application. The unique properties of biochar include low density (providing additional voidage and aeration in the soil), significant adsorption and cation exchange capacity, and the ability to promote living microbiology in the soil, enhancing the ìSoil Food Webî. Combining these properties leads to a predictable selection criteria for when to consider activated carbons versus biochar.
As noted earlier, activated carbon is intended and optimized for adsorption applications, and is available in many physical forms and grades that are specialized to the end use. The market has been growing steadily for the past 50 years, driven by specific purification processes in some industries and many applications involving removal of organic compounds from air and water streams prior to discharge into the environment. Indeed, most of the activated carbon demand has been created by a series of environmental regulations that have been enacted over the years, including the Clean Water Act and the Clean Air Act.
Production and markets around the world
The current world production of activated carbon products is approximately one million tons per year, with most production in Tropical and Asian countries. The majority of activated carbon production is exported to developed countries in North America and Europe, where it is used in environmental and processing applications. The activated carbon marketplace is dominated by a relatively small number of international companies that have both production and marketing capabilities.
Over the past few years, the developed countries have been enacting new regulations requiring the removal of trace mercury from industrial emissions, principally impacting the coal-based electric power industries in North America and Europe. This has created an additional market for specialized powdered activated carbons that serve to capture mercury from the flue gases of power plants. The potential market demand for these MATS = Mercury and Air Toxics Standards activated carbon is several hundred thousand tons per year if the entire industry used the technology, but the combination of aging coal plants and cheap natural gas has resulted in significantly lower actual market requirements for mercury-capture activated carbons.
Mercury capture is one of very few market applications where biochar products might complete with traditional activated carbon products, with the other being those remediation applications where soil decontamination due to legacy pesticides or ordnance residues are preventing significant plant growth. In the mercury marketplace, biochar is at a disadvantage due to the presence of established suppliers from the activated carbon producers. In contrast, in remediation, biochar has the advantage that it can provide the initial detoxification requirements, followed by providing the added benefits of improving the soil as a growing medium for all forms of vegetation.
The biochar marketplace is nascent and suffering from ìthe chicken or the egg syndrome. To date, there have not been sufficient reliable suppliers of biochar products to allow the demonstration of the at-scale value propositions in specific biochar markets. Thus, the issue of how cost-effective is biochar in reducing water and fertilizer requirements in specific markets such as corn cultivation is basically unresolved, although credible studies are accumulating in the literature and within individual industrial demonstrations. Furthermore, in the absence of specific market opportunities that demonstrate the value of biochar, financing biochar production capacity is stymied. The development gridlock is slowly being resolved and rapid growth in biochar capacity and adoption is anticipated over the next decade.
There are some external drivers that are also promoting biochar adoption, including atmospheric carbon dioxide levels and concerns driven by consequences of climate change. Since biochar is produced from biomass that was created from carbon derived from carbon dioxide from the atmosphere as the plant grew, the carbon in biochar is viewed as ‘carbon-negative’. As such, it represents carbon removed from the air and converted into a form that will remain in the soil (and out of the atmosphere) for centuries or longer.
Unfortunately, to date, the direct financial incentives for sequestering carbon dioxide have been insufficient to significantly stimulate biochar production. With the adoption of the Paris Climate Accord, biochar has become recognized as one of the most viable and accessible methods for reducing a nationís carbon footprint and meeting future emission reduction obligations. This trend will play itself out in many versions in individual nationís public policies for managing the requirements of utilizing fossil fuels and achieving reduced overall climate impact goals.
Frankly, it is impossible to predict how the climate driver will or will not stimulate the future biochar production and utilization patterns. Additional, and equally powerful, drivers for the adoption of biochar are the documented improvements in water requirements in agriculture due to improved moisture retention and management by biochar-enhanced soils. With the improved water retention, the concurrent phenomenon of loss of soluble soil nutrients by leaching, when excess precipitation extracts nutrients out of the soil, is suppressed. It is the combined improvements in water and fertilizer efficiency by an existing growing method, coupled with the potential benefits of enhanced soil health due to improved soil microbiology, that create a powerful economic argument for the widespread adoption of biochar.
However, only time will tell how it will all play out.
Hugh McLaughlin is a member of Lee Enterprises Consulting. Lee Enterprises Consulting is the worldís premier bioeconomy consulting group, who have consultants and experts worldwide, including in the technologies discussed in this report.† The opinions expressed in the report are those the author, and do not, necessarily, express the views of Lee Enterprises Consulting.
Hugh has a B.S. in Chemistry from Harvey Mudd College, an M.S. in Chemical Engineering from the USC, and a Ph.D. in Chemical Engineering from Rensselaer Polytechnic Institute. He is a registered professional engineer in Massachusetts. Hugh is a recognized technical/technology expert in biochar and activated carbon, having designed and commercialized patented technologies for their production. He is a leading authority on biochar properties and characterization.