Biochar is an ethically sourced charcoal made from invasive species, agricultural waste or forestry clearing organic matter (or biomass) that has gone through a low-oxygen heating process called pyrolysis. It is known to remediate polluted soils, increase agricultural yields and store carbon. Can hemp and biochar help fight and mitigate Climate Change, together?

Raw biochar courtesy of Louis Miller of Miller’s Soil

Slash and Char – a 10,000-year-old Soil Fertility Management Method

The world of maintaining and sustaining our precious living soil web, ethically, has been practiced for thousands of years. If you were to visit the Amazon Basin in South America, there you will see rich, dark, and fertile soil that has been taken care of by the stewards of the land between 450 BCE – 950 CE. Amerindians practiced what we call “slash-and-char” where biomass, manure, compost, pottery shards, and bones were mixed, and low-temperature charcoal was added and then buried. The resulting soil,  known as “Black Earth” or Terra Preta has been studied for decades since its discovery in 1960 by soil scientist Wim Sombroek. This method of increasing soil fertility allowed for the creation of cities that in the 14th century were larger than London was at the time and considered as an early form of carbon farming.

Today, instead of slash-and-char, slash-and-burn techniques are being used to clear land, deforesting while emitting the greenhouse gasses (GHG) that contribute to global warming. Farmers used this method to bring nutrients back into the soil, temporarily, and once the soil has degraded, generally a couple of years later, they migrate to other land and repeat the process – not a sustainable method if you ask me. Yes, the ash content from the burnt vegetation will temporarily enrich the soil, but slash-and-char is the better alternative because instead of releasing GHG and destroying habitats, we are reducing CO2 emissions, storing carbon, and enriching soil all in the same process with great advantage to the ecosystem.

The slash-and-char method was the farming communities’ way of practicing soil management and keeping the earth beneath us fertile and healthy. Not only did this enriched soil teeming with nutrients and microorganisms give the farming communities high yield in their harvest, but it also sequestered carbon. If we continued to follow the wisdom of the indigenous Indians who lived along the Amazon Basin and mimic their ability to keep the soil fertile by the slash-and-char method, we will sequester carbon helping us decarbonize our atmosphere, mitigate climate change, and combat global warming.

Climate Change and Why Should We Be Concerned

Climate change. We hear about it on the news, on podcasts, and global summits gather year after year to discuss it, but what is climate change and why should we be concerned? Climate change has been defined as “Climate change is a long-term change in the average weather patterns that have come to define Earth’s local, regional and global climates. These changes have a broad range of observed effects that are synonymous with the term.” by NASA. Our planet’s temperature is slowly, but steadily rising due to greenhouse gas emissions. With an outstanding number of metric tons of GHG being emitted per year, this can cause natural disasters and erratic weather patterns. Warmer waters can increase harmful algae blooms that will negatively affect marine life, cause a rise in salinity in freshwater, and lead to droughts. Ice caps, which are naturally a carbon sink sequestering 58 megatons of C02 a year, are melting. This will cause more carbon to be released into the atmosphere and with glaciers melting it may contribute to the rise of sea levels and in turn, may cause devastating floods to low-lying coastal cities and islands. Most importantly, climate change has greatly impacted our farmers. Weather patterns have become more erratic, droughts are lasting longer each passing year and desertification menaces the livelihood of billions.

Farmers are urging the government to act now and would like to know how they are addressing climate change. Farmers and ranchers have the most important job and that is producing and providing the nation with food. When there is a lack of technical support, resources, and guidance from the government, farmers are feeling lost. They simply cannot compete against Mother Nature. With soil degradation spreading across the nation, the country will most likely experience food insecurity. Alongside food insecurity is the alarming rate of inaccessible water. Soon lakes, reservoirs, and freshwater sources will deplete, and it may be too late to reverse it. Irrigation will become problematic and states that are practically deserts will scramble to find a solution to conserve water and may use drastic measures to preserve and conserve clean water (Utah has already imposed fines for excessive and improper water usage). To reverse global warming or to keep our planet’s temperature below 1.5 Celsius we, as in globally, must remove 10 gigatons of CO2 per year for the next 30 years – that’s a billion metric tons or 2.2 trillion pounds per year by 2050. Yes, there should be a sense of urgency that our life necessities are in the red and racing against the clock, but there is hope if we utilize existing carbon sink technology and carbon sequestration solutions.

Pro-Natura International’s super vegetable garden grown with biochar

Charred Biomass Saving the Planet One Hectare at a Time

How do biochar and hemp fit into the equation of mitigating climate change? Let’s start with biochar. As stated earlier, biochar is created by heating ethically sourced organic matter (contrarily to charcoal, which is the main cause of deforestation in Africa) in a low-oxygen environment. The organic matter can be wood, forestry and animal waste, food, and crop residue. During this process of pyrolysis, a type of charcoal is created. Biochar is slightly different from the other types of charcoal we are normally exposed to. It’s not charcoal you throw on a grill to cook up your kabobs – though both go through the pyrolysis process and are carbon-rich solids – the difference between the two is one is used for soil amendment with high adsorption capabilities (the ability to remove micropollutants and metals) for agricultural purposes and the other is used for fuel and heat. To create biochar, a pyrolysis kiln is needed. Some kilns can range in the thousands to half a million-price tag and there are kilns that can be DIY and done in your own backyard. Depending on how you want to scale your operation whether it’s small or commercial, being able to access a kiln isn’t problematic, but it must be sized appropriately for your biomass.

During the pyrolysis process, the biomass or feedstock is being heated at a certain temperature. For biochar, ideally, you would like the kiln to heat the biomass at 300-800° Celsius. With higher kiln temperatures, the biochar will have higher porosity (varies on the type of biomass for surface area and porosity structure and chemical reaction) and decreased content in volatile matter (which plays a role in plant growth and hydrophobicity). Pores are important for water-holding capability, and it also plays the role as a microhabitat for microorganisms like mycorrhizae fungi and bacteria. Biochar can retain water because of its many pores, thus creating channels to the roots of the plants, promoting plant vitality and healthy growth. Its micropores’ sorption process dissolves organic matter, improves microorganisms’ activity, and becomes a catalyst in the soil remediation process by cleaning up soil pollutants.

Biochar is a phytoremediator, but how does it store carbon? There are two types of pyrolysis processes, slow pyrolysis, and fast pyrolysis. The difference between the two are pressure, heating temperature, and time. Fast pyrolysis is a preferred process to turn biomass into a liquid form like bio-oil or biofuel or a gas through gasification and slow pyrolysis supports carbonization through a complex process of thermal decomposition. Since biochar is organic matter being charred and turned into a solid, the carbon from the organic matter is being stored in this type of charcoal. And instead of burning it, we are burying it (if it’s suitable for agriculture and not full of toxins and metals) and returning carbon back into the soil. Biochar is carbon storage with beneficial properties for the soil, the most important land surface on this planet that has been neglected and overlooked.

Simply put, biochar can help mitigate climate change because of its ability to store water and support the water cycle, which greatly impacts how we live. Climate change affects the precipitation of rainfall, thus causing an imbalance for regions that are seeing a rise in excessive rainfall and drought. The planet’s behavior is shifting because of warmer temperatures and utilizing biochar can possibly stabilize the natural cycle of water distribution and temperature. Because of biochar’s water-holding capabilities, there will be less water evaporation. Why is that important? Fast evaporation can cause low-forming clouds and cause a faster rate of rainfall which leads to floods. Floods can devastate topsoil that leads to run-offs into our waterways and channels. Run-offs can carry pollutants and toxins into our waters because of improper water filtration. Polluted waters threaten our access to clean water, which we need for irrigation for agriculture and drinking water for humans. Topsoil is quite important since that is where the soil food web lives and when there is disruption of our soil food web, there is the displacement of microorganisms. If you’re a fan of food, you’re going to want these microorganisms. Water vapors, evaporation, makes up 60% of GHG which can affect the non-condensed GHG that is warming our planet. Biochar can possibly help the water cycle because of its job of holding water that can help minimize water run-offs and promote proper water filtration while storing carbon, remediating the soil, and giving a home to microorganisms.

Because of biochar’s surface structure, which is responsible for hydrology functionality and high porosity, there is a lot of capillary action. This is great news for water retention and better news for drought-prone regions, like Africa. We spoke to Brando Crespi, Vice-Chair of Advanced Carbons Division of Santa Fe Farms, Mitchell Prize winner and environmentalist who has worked with biochar for two decades in 63 countries. Crespi knows biochar can help drought-prone regions and has successfully used biochar to promote crop growth while remediating the soil and storing carbon. Crespi and the non-profit he co-founded, Pro Natura International, have worked with biochar for 15 years in regions where water accessibility is limited or scarce.

With the biochar from their pyrolysis technology, that won the Altran Foundation prize for best technology for the developing world, they were able to help families grow vegetables on the edges of the Sahara Desert. “Our “super vegetable gardens” using biochar, camel dung, very little water, and much elbow grease produce 11 harvests throughout the African Sahel countries. With just 60 sq meters they can feed a family of 10 and the excess production can then be sold in their marketplaces.” Crespi stated. If growing produce in the desert, without disrupting the natural ecosystem, is achievable what can it do with our existing farmlands and importantly, to their crops and yields?


Hemp grown in Miller’s Soil biochar

Doubling the Yield, while Remediating the Soil

In a country where monoculture is the norm and biodiversity practices are minimal, conventional farming has unintentionally ruined our soil. With over-tillage, weed-suppressing chemicals, and little crop rotation, our soil is slowly turning into dirt. The UN has calculated that there are approximately 60 harvests left from our soil, a reality that has been called “peak soil” Soil health lays the foundation for plant vitality and crop growth. To support soil health, you want your soil to be teeming with nutrients, microorganisms, and decomposing plant material – and if you spot worms in your soil, that’s a good thing. Farmers or producers can test their soil by contacting a soil health consultant to further understand their soil’s fertility but would be best advised by consulting with a soil scientist to learn more about their soil and take additional steps if their soil is experiencing nutrient deficiency and degradation. To reverse the damage that has been done to the soil, biochar can be used as a soil additive for farmers and other methods for regenerative farming can be adopted. With biochar’s ability to store nutrients, clean up micropollutants, and hold water, it is one of the solutions to remediate our land. Combine biochar, the use of mycorrhizae fungi, and cover crops to a field and that will not only save costs on water usage but help to conserve it. Biochar will help remediate and promote soil health while cover crops help suppress weeds.

Farmers have seen success with their crop and yield when adding biochar to their soil. There are countless trials and experiments around the globe where crops have doubled in size and have combatted floods and run-offs using biochar vs conventional fertilizers. Biochar technology has been adopted in developing countries, which has been proven to be a solution as a viable tool for a successful harvest and economic opportunities for families. The International Biochar Initiative has gathered data from 43 countries working with biochar and their trials can be viewed on their website.

Hemp farmer, Kasey Cannon of Fox Canyon Co of California, used biochar in her planter box when growing cannabinoid hemp. She states that the comparison between field-grown hemp and those planted in biochar was noticeable. Her cannabinoid hemp grown in the field was the average height of 3-4 feet, but the plants that grew in her biochar bed doubled in height and got as high as 8 feet tall. Their cannabinoid percentages in their flower that was in the biochar bed also reached a high 17-18% range which on average, cannabinoid producing plant percentages range about 12-13%.

Different feedstock has been used and has been experimented with to produce biochar. From pine needles to rice husks to camel dung, feedstock or biomass can be made from most organic matter. Does that mean hemp has the opportunity to be used as biomass for biochar?

Pyrolysis Kiln – Biochar Solutions Production Equipment

Hemp in Biochar and Beyond

Can hemp biomass be a suitable feedstock for biochar and a possible avenue for hemp producers to explore? The answer is yes, but before you toss your hemp biomass in a pyrolysis kiln and call it a day, there are some things to consider.

Hemp can be grown for cannabinoids, fiber, and grain. Each type being turned into various end-products. With cannabinoid-producing hemp being the most popular and mostly grown in the US, cannabinoid biomass is readily available; but can it be used as suitable biomass for biochar? Since there has been minimal research and development surrounding hemp and biochar, we’ve reached out to a few industry professionals who have experimented with hemp biomass and biochar to gather their thoughts and opinions.

Louis Miller of Miller’s Soil has done some R&D on hemp and biochar and answered a couple of our questions regarding hemp biomass and biochar.

  1. Is hemp different from other biomass typically used for biochar?
  2. Yes, it is different because hemp holds on to everything from the soil.
  3. If hemp biochar can be a viable option for farmers, what are the issues they might run into?
  4. We have found high metals in all the hemp char we have produced. So that’s not good char to go back on to a field but there are homes for that char.

Since hemp is also a phytoremediator, it is understandable that there would be high metals in the char being produced. Since it can’t go back into the soil, where can it go? Miller suggested it can be used for “Mine reclamation sites and/or as air filtration for heavy metals.” Which studies had suggested that using biochar on mine sites can lead to an increase in pH and soil water content which can help with vegetative cover.

We asked Crespi a similar question on where biochar that is high in metals can be used and he stated “It can be used in asphalt or in cement.” as a bio-modifier. Not only does it improve their performance, it decreases the high carbon footprint of these two materials.

The type of hemp feedstock is also important in creating biochar. The hemp that was used in Miller’s R&D was raw cannabinoid hemp, which has not been through any type of ethanol-based or solvent process, which is key because you obviously do not want to throw flammable and combustible biomass into a heating chamber. But not all is lost because there may be a solution for the solvent-processed hemp biomass which may be used in advanced biochar technology.

Clayton Turner, Visionary of Santa Fe Farms, states “Hemp waste material is biomass and pyrolysis machines make biomass into biochar. Most often the material is made from the woody content of the stem containing lignin and in the case of hemp extraction, we are left with a mixture of stem and bud as well as leftover stems from flower hemp production (these materials may be soaked in solvent, depending on your system you may want to take that into account as this adds volatility and gasses to the plant and can cause issues with ignition in your process where you do not want it and our process takes this into account). The material is burned, the gasses are then captured, and biochar is derived along with wood vinegar, biofuel, and syngas.”

Biofuel and syngas support the innovative clean energy industry in which Sweden has invested and is now using biochar to power Stockholm’s district heating network and also using it to promote tree growth. Wood vinegar and biochar can be used as fertilizer as well and decrease the leaching of glyphosate (commonly used herbicide) from plants.

Another innovative avenue for the hemp industry would be to really dive into the properties of hemp cellulose and lignin. There in the stalk holds the potential and power for electrical conduits, aerogel, and as an elite carbon-cycler.

The possibilities are there when using hemp biomass as biochar, especially when mixed with other organic matter. As an emerging industry in the United States, more research and development must be done to further explore the potential of hemp in the biochar industry.

Anna Chanthavongseng – National Hemp Association