More than 12 years ago, I gave my first public presentation about biochar to a room filled with people far more knowledgeable about biochar than I was. It was a 5-minute Ignite-style talk where sound-bites are the order of the day. One of my slides is shown above and the words behind it were:
This thing called biochar covers an almost unlimited variety of products which are in fact very different. A very smart Cornellian once compared it to using the word ‘tree’ and leaping to the conclusion that all trees are the same. We need to acknowledge and understand the differences between charred products.
Fast forward to the present when biochar is finally experiencing a ‘moment’ yet we are still struggling as an industry to agree on a definition of biochar. A few times per year without fail someone in the ever-helpful biochar forum (https://biochar.groups.io/g/main/topics) rails against the misuse of the word biochar for one reason or another. A typical case is someone claiming it’s not biochar unless it’s blended with something to put the ‘bio’ in it. Or the topic comes up on LinkedIn (and probably other social media sites that I have long since abandoned) and the turf defending gets personal and impolite (to say the least). Engaging in these discussions used to be interesting, now it’s mostly tiresome as the same ground is covered over and over. It is, however, important to outline some of the challenges in defining biochar. Here is my take:
Defining something by what it looks like. Some things you can name just by looking at them. This may only get you so far however if a name covers a wide category such as trees or birds. Biochar looks almost exactly like any other black powdery substance including charcoal, activated carbon, carbon black, graphite, graphene, fly ash and even gun powder! So using looks to identify biochar is a no go.
Defining something by what it’s made from. Although almost any material can be pyrolyzed including tires or plastics, the solid output cannot always be labelled as biochar (though many still call it that). “Eligible” feedstocks vary somewhat by which standard or methodology is being referenced. Most non-fossil organic materials are considered eligible though even that is not always straightforward. In the early days of carbon removal credits, some methodologies did not support purpose-grown feedstocks for fear of incentivizing another ethanol boom or debacle depending on your perspective. More recently I’ve heard some say biochar from trees shouldn’t be included since it is “older carbon” and releasing any of that CO2 during production is a bad thing. Others eschewed, and may still do (I haven’t kept up on this sort of thing), residues from palm oil production as that industry has contributed to vast destruction of old forests and biodiversity and they don’t want to condone that. Still others disallowed organics contaminated or blended with things like plastics or in-organics. So, defining biochar by what it is made from has been problematic.
Defining something by how it’s made. Biochar has been produced by many ancient cultures using fairly primitive methods for thousands of years. Only in the last few decades has it been produced at industrial scale using high-tech machines. Exactly what types of equipment produces biochar is often disputed. Purists promote pyrolysis as the one true process for biochar production. Others support a broader range of thermochemical conversion including gasification and modified combustion. Hydrothermal carbonization has both supporters and detractors. Lower tech kilns more in line with how indigenous cultures made biochar has also, for some reason, found some very vocal critics. I’ve heard all kinds of rationales for why some should be included while others excluded; from the ‘quality’ of the biochar (which IMO varies by end use) to the potential emissions which are assumed to be emitted. So, much as some have tried, defining biochar by how it is made has also been challenging.
Defining something by its function. A functional definition focuses on what something does such as charcoal being used for cooking or heating. For many in the biochar industry biochar is viewed as a soil amendment and nothing else. For others, me included, it casts a broader net to include anything that helps keep the carbon captured during the plants lifetime from returning to the atmosphere. Particularly when viewed as a carbon removal strategy, widening the definition this way makes a lot of sense. It also excludes the use of the word biochar as a substitute for fuel which is a bit of a bone of contention for some. Here again using a broad category such as function or purpose has proven to be imperfect and often confusing.
Defining something using standards or methodologies? Then we have standards, which one would think clears things up noticeably when it comes to what is or is not biochar. And yet, they have not. In days of old, the International Biochar Initiative created a material standard for biochar use in soils. This defined biochar by three main things: carbon content, H/C ratio and toxins (there were other categories, but these are the main things). The Europeans developed more nuanced categories for biochar including biochar use in livestock feed, agriculture and materials. These morphed into what are now administered under the World Biochar Certificate banner. Then along came biochar methodologies for carbon removal some of which defer to the WBC standard, though others don’t directly. They are particularly focused on the durability of biochar (also known as permanence) but also layered on additional requirements, for understandable reasons, about how biochar is produced from the perspective of minimizing emissions. In the days when hardly anyone had even heard of biochar, biochar producers focused more on standards that farmers were more familiar with such as the organic standard OMRI, to assure organic farmers that their biochar would pass muster. OMRI allowed some but not all types of biochar to be certified, specifically they disallowed biochar produced from manure to be certified as organic. Newer standards are being developed for specific end uses such as biochar use in concrete with the aim of providing more confidence to those buying biochar for this purpose. It will, I believe, focus more on the specific properties of relevance and the optimal range for those parameters for use in concrete versus what it is made from or how it is made. I would love to see more of this in the future for different end uses such as improved water holding capacity in soils, water filtration for specific toxins such as PFAS, etc.
A few years back some of the top-notch biochar producers began emphasizing the need to move away from using the word biochar to saying ‘biochars’. This was a good start towards educating producers, policy makers and end-users about the nuances of biochar. Hopefully this post about the other challenges the word biochar has posed will help readers understand some of the nuances the industry has and continues to face in explaining what it is!
