The use of the word “biochar” needs to be used with some understanding of the product. We’ve talked about biochar needing to be from a biomass. The use of biomass gives us the “bio” in biochar. The “char” part of biochar is what can be defined by people in many ways. The char is the carbon framework without any residual oils leftover after pyrolysis. Wakefield Biochar is not a fuel. We don’t call it charcoal for a reason. It doesn’t have the oils in it to help provide heat in your Weber Grill. Wakefield wants our customers to be able to confidently purchase premium biochar that is high quality and useful. How we handle the biochar after pyrolysis makes a difference. First, why would you want to do something extra to biochar after it has been through pyrolysis? It’s a reasonable question. There are good things that can be done and some not-so-good things. Let’s discuss quenching, activating and charging biochar.
After the biochar has been created in the pyrolysis reactor, the biochar is extremely hot; too hot to handle. It needs to be quenched with water. Quenching drops the temperature of the biochar and adds water to the mixture. Having some water in the biochar makes it easier to handle and ship. Biochar that is bone-dry is extremely light and can fly away on a windy day and get in your eyes. Quenching is done by most all large-scale biochar manufacturing systems.
At this point, we have a great biochar. If you were to take this biochar and continue to clean it up with chemical or thermal processes, then you would be making a pure “activated carbon”. There are some companies that don’t call their product biochar, but they will refer to it as a hybrid biochar. They can’t call it biochar because the company has conducted more processing of the biochar after pyrolysis. For example, if you do acid washing, re-heat the biochar or blast it with steam, then you will be removing the ash, oxygen and other minor components of the biochar to create an activated carbon. A high quality activated carbon is pure carbon (100%). Biochar has a high carbon content (60% to 90%), but would not be 100% carbon.
The term “activated” means that the surface of the carbon has a large number of pores for the purpose of adsorbing gases and solutes out of solution. Activated carbons can have a surface area of 1500 to 3000 m2/g of material. There can be very useful and important reasons to use activated carbon in purification and other commercial processes. Biochar is activated once it is finished with the pyrolysis process and it has a large surface area to interact with the air, water and soil. Wakefield biochar has a surface area of approximately 365 m2/g. Wakefield biochar is considered a low grade activated carbon. Less than 15 grams (or 0.03 lbs) of Wakefield biochar has a surface area similar to a football field.
The term “charged” means that the biochar is ready to provide the soil with water and nutrients to support microbial life and increase root growth for plants. The biochar will be charged with nutrients like nitrogen, phosphorous, and potassium and other micro-nutrients. Charging biochar is done in many ways. The biochar directly out of the pyrolysis system is not charged. You can mix biochar with organic materials like compost, worm castings and fertilizer and water prior to putting into the soil. Giving the biochar to mix with these products will allow for the biochar to adsorb their nutrients. This is one of the big benefits of biochar. Without biochar, more of the nutrients in compost and other soil amendments will leach away into the soil during watering and rain events. The biochar holds the nutrients and provides them to the microbes and plants with a much greater efficiency. Many studies have shown that biochar-amended soil requires 40 to 60% less fertilizer than non-biochar amended soils. The biochar is making the nutrients more available to the microbes and plants.
Sieving vs. Grinding
The size of the feedstock will impact the size of the biochar. A feedstock will reduce in size during pyrolysis to form the new carbon structure. There are times when the size of the biochar is as important as the surface area and carbon content. If biochar is being used in water remediation projects, there may be a preference for the biochar to be larger particles to allow for easier water flow and to prevent the clogging of a filter. Any fine particles in the biochar would be detrimental to the project. In this situation, the biochar should be sieved to remove the fine particles and leave the larger pieces. On the contrary, biochar can be sprayed in a solution. To spray biochar in solution, the biochar will have to go through a nozzle with consistent particle size. Sieving is a valuable way to apply biochar without having to change the shape of the biochar particle after pyrolysis.
Grinding biochar has been done achieve smaller particle sizes. Wakefield Biochar has not been ground up. The surface of the biochar is key to how the biochar interacts with soil and water. Any grinding of the biochar will destroy the pores on the surface of the biochar and lessen the effectiveness of the biochar.
Carbon Negative Process
Wakefield Biochar wants to provide an environmentally friendly product. The waste from the additional washing of the biochar can be more of a burden for waste disposal and, due to the nature of the added processes, increase pollutants to the environment. Correctly manufactured biochar is a carbon negative process. A carbon negative process reduces the amount of carbon being released into the atmosphere as a greenhouse gas (carbon dioxide, methane, etc.). Activated carbon is the result of a carbon positive process because the energy requirements to get a 100% carbon product takes more energy and, in turn, more release of greenhouse gases into the environment than are being sequestered back into the soil.
Biochar that has been put in the ground is considered to be an act of sequestering the carbon. Normally, as a biomass decomposes, the natural microbes in the soil will break it down, use oxygen and release carbon dioxide. If, however, undergoes pyrolysis, little or no carbon dioxide would be released, and the bulk of the biomass would harden into a kind of porous char, essentially sequestering the carbon as a solid. Learn more about geoengineering.
Molly sloboda says
Thank you so much for this. This solved my biggest issue for this presentation in my class about why we should use pyrolysis.
Jackie Smith says
Looking forward to adding biochar to a pile of cow manure and then spreading on my sandy soil. Have added manure in the past but nutrients leach out after only a couple years. I hope the biochar gives me some ling term fertility. I’m going to see what happens with no amendments, only manure, and with manure/biochar. I’ll take photos