The scientific merit of the benefits of biochar as a soil amendment has been tested for over a thousand years. Highlighted by the Parliament of Australia, Department of Parliamentary Services, 10 September 2009, “The Basics of Biochar”; biochar is primarily produced using pyrolysis on biomass—which is plant material and agricultural waste—hence the name ‘biochar’. Pyrolysis is the heating of organic matter in a low- or no-oxygen environment. What differentiates biochar from charcoal is its purpose; it is produced as an additive to soils, mainly to improve nutrient retention and carbon storage. (Ref: J Lehmann and S Joseph, eds, Biochar for environmental management, Earthscan publishing, London, 2009). The history of biochar extends thousands of years.
The term ‘biochar’ first appeared in the modern scientific literature in a paper presented by Harshavardhan Bapat and Stanley E. Manahan at the 215th National Meeting of the American Chemical Society in 1998. They won first prize for that paper from the ACS division of Environmental Chemistry in the category of poster presentations: Bapat, Harshavardhan D., and Stanley E. Manahan, “Chemchar Gasification of Hazardous Wastes and Mixed Wastes on a Biochar Matrix,” 215th American Chemical Society National Meeting, Dallas, March 29-April 2, 1998. I was thankful to conduct my graduate research under Dr. Manahan from 1998 to 2002.
Despite the relatively recent scientific push to understand the benefits of biochar, the origins of the concept for biochar are ancient. (Ref: EG Neves, RN Bartone, JB Petersen and MJ Heckenberger, The timing of Terra Preta formation in the central Amazon: new data from three sites in the central Amazon, 2004, Springer: Berlin; London.) Throughout the Amazon Basin there are regions—up to two meters in depth—of “terra preta”, which is the Portuguese term for “dark earth.” This is a highly fertile dark-colored soil that has for centuries supported the agricultural needs of the Amazonians. Theses fertile areas exist only where humans occupied the area. As shown in the photograph (See Figure 1) comparing soils with terra preta and without in the Amazon, the ability for corn to grow is significantly better with the dark soil. Biochar is equal to terra preta with the same benefits to the land.
Figure 1. Photo credit to Julie Major and Bruno Glaser
Longevity of Biochar
The longevity of biochar, a carbon-based porous material, has proven to provide higher crop yields, improve soil health and retain nutrients in the soil and preventing their leaching into the groundwater. There are a number of benefits of biochar that will provide a positive effect in preventing nitrogen and phosphorous components of fertilizer from leaching into tributaries and finding their way into the Gulf of Mexico and creating a dead zone from hypoxia (little to no oxygen in the water):
- Strong ability to retain hydrocarbons and other organic compounds
- High Cation Exchange Capacity (CEC)
- High physical adsorption capacity within the macropores (up to 10 microns) to micropores (sub-nanometer) (Ref: AIChE website https://aiche.confex.com/aiche/2015/webprogram/Paper425349.html )– surface area correlation numbers of approximately 500 m2/g dry
- Able to maintain structure as a stable lattice network
- High carbon content
- High organic content
- Able to improve soil water retention (Ref: “Biochar addition to agricultural soil increased CH4 uptake and water holding capacity – Results from a short-term pilot field study” Agriculture, Ecosystems and Environment 140 (2011) 309–313)
- Provide viable environments for beneficial microbes to grow and positively impact plant growth as well as remove harmful organics
- Sequester carbon in a stable structure which prevents the carbon from converting to carbon dioxide and contributing to greenhouse gases
The high surface area and the excellent cation exchange capacity of biochar provides an efficient surface for the binding of ammonium and ammonia (Ref: Treating Liquid Manure with Biochar, Hans-Peter Schmidt, Ithaka Journal, Vol 1 (2012) pages 273-276, ISSN 1663-0521).
Manufacturing of Biochar
The manufacturing of biochar contributes to carbon sequestration and provides usable bio-fuels in addition to the creation of biochar. Overall, biochar manufacturing is considered a carbon negative. This means that there is more carbon being removed from the atmosphere than would have been released under normal circumstances. Using pyrolysis, responsibly obtained biomass is processed in a low or no oxygen environment at high temperatures ranging from approximately 400 to 800 degrees Celsius. The majority of feedstock/biomass used in biochar manufacturing is obtained from the waste or byproduct from farm fields, like corn stover and grass, and the fallen or diseased trees removed by Forestry Departments from forests. If these feedstocks were left to decompose naturally a high percentage of their carbon content would be converted to carbon dioxide and released to the atmosphere. The conversion to biochar locks the carbon in a stable form that will not react with oxygen to produce carbon dioxide. The diagram (See Figure 2) shows the basic method for pyrolysis. In the manufacturing, there is the ability to recycle the heat from the pyrolysis to power the machinery. In addition, the heat given off by pyrolysis can be distributed as electricity for consumer use. If the feedstock is too wet and the moisture content greater than optimal levels for pyrolysis the heat from the pyrolysis reaction can be diverted to dry the feedstock prior to entry into the reactor cell. Therefore, the manufacturing of biochar has additional scientific merit to the stewardship of our environment and the positive application of biochar on farmland for the retention of fertilizer.
Figure 2.Pyrolysis Process Diagram – www.dynamotive.com
The Smart Group Inc, report dated May 2013, “Biochar and Remediation of Disturbed Lands and Water – A Review of the Effects of Biochar on Reducing Contaminant Concentrations in Disturbed Soils and Water” provide support from multiple academic studies confirming the effectiveness of biochar to retain nitrogen and phosphorous compounds. (See Figure 3)
Figure 3. University Studies – Biochar and Nitrogen and Phosphorus Effectiveness
Based on a Purdue University study, titled “Building New Corn Nitrogen Fertilizer Recommendations for Indiana – Results of 2006 Nitrogen Rate Trials” by Jim Camberato, Bob Nielsen, Dan Emmert, and Brad Joern, https://www.agry.purdue.edu/ext/soilfertility/Nratetrials.asp, the optimum economic yield at $3.50 per bushel of corn at $0.30 per pound of nitrogen resulted in 177 pounds of nitrogen per acre. As the price of corn decreases and the price of nitrogen increases the economic effect is 148 pounds of nitrogen per acre. The average yield was 185 bushels of corn per acre. Of the 150+ pounds of nitrogen per acre, there may be up to 50 pounds of nitrogen loss. Typical nitrogen losses from heavier soils in winter and spring have been in the range of 20 to 50 pounds of nitrogen per acre in tile drainage studies at Purdue University (Brouder et al., 2005, https://www.agry.purdue.edu/ext/corn/news/articles.08/floodingnitrogen-0613.html ). Therefore, adding biochar to the soil would need to hold an estimated 50 pounds of nitrogen. A 5% mix of biochar in the top 5 inches of soil is equivalent to 33.6 cubic yards of biochar. An estimated weight of 750 pounds per cubic yard for biochar equals a total weight of 25,200 pounds of biochar per acre. Based on this scenario, the biochar would have to utilize less than 0.2% of its mass to retain the biochar. Similar values would hold true for phosphorus. It is reasonable to hypothesize that the biochar has a significant chance of retaining nitrogen that is not utilized by the crops or held in the soil by other mechanisms.
The ammonia (NH3) and ammonium (NH4+) ion are excellent at sorption with biochar. Biochar’s cation exchange capacity, the capacity for biochar to hold and exchange cations, is high due to many reasons. First, there is a high porosity of the biochar’s surface during pyrolysis. It also has a high charge density on the surface. The use of a high-temperature pyrolysis gives a strong aromatic structure and higher C:O ratio than using a lower temperature pyrolysis. It would be a best practice to have the starting species of nitrogen used in the fertilizer to be in the ammonia and/or ammonium ion form. The sorption on the biochar surface is primarily due to electrostatic interactions. With regard to ammonia, there are many documents to support biochar’s ability to make it bioavailable for crops. Specifically, biochar influences soil nitrogen transformations and its capacity to take up ammonia is well recognized (Ref: Taghizadeh-Toosi, A., Clough, T.J., Sherlock, R.R. et al. Plant Soil (2012) 350: 57).
Using beneficial microbes to increase the uptake of fertilizers to the crops has good promise to a more efficient transfer of nitrogen to crops. These microbes are a critical part of the conversion of nitrogen to nitrate; the usable form for plants. Using fertilizer in an ammonia and/or ammonium ion starting material allows the microbes to convert the nitrogen to a nitrate for uptake by the plant roots. Having the microbes control the conversation rate of nitrogen to nitrate will all create a higher efficiency of nitrogen use by the crops. In turn, this will prevent the leaching of nitrates into the groundwater.
Do the Benefits of Biochar Scale
The scalability of using biochar in farm fields to prevent nitrogen will improve soil health and increase crop yields on farmlands around the world. There will be a chain of events that are positive from the use of biochar. First, farmers will use less water. Then they will react to soil testing by using less fertilizer. The crop yield increase will provide value added to their farms. This is a big idea which already has scalability in place.
The manufacturing of biochar has been done for over a thousand years. By this timeline, we can say that even a simple resident with a small subsistence farm in a third world country can make enough biochar to benefit their field. On the flip side to that, in our industrialized nations that are facing regulatory issues for environmental pollutants, there is a strong growth in renewable energy and smart agriculture. The use of existing gasification and pyrolysis units around the United States and the world already produce biochar as a byproduct. This byproduct (biochar) has economic value to a larger economy. Farmers lower operating costs because they will need less water and fertilizer due to biochar’s proven ability to hold them in the soil. The increased bioavailability of nitrogen for crops will increase yields and provide more food for the world and higher profits to keep farmers (large and small) in business. The energy companies looking for renewable energy sources can optimize biomass as an energy producer and incorporate biochar in their business model as a revenue source. Additionally, healing our rivers and oceans will increase fish populations and, in turn, the fishing industry. The global impact of a large-scale biochar use in farmland is the sequestration of carbon and the reduction of greenhouse gases, like carbon dioxide on a massive scale. Using carbon neutral technologies are good for the world, but biochar incorporated in farmland is BETTER. Biochar is a carbon NEGATIVE. It will help to reverse the amount of carbon dioxide in the atmosphere by locking the carbon in the soil!
Of special note, there are now biochar manufacturing facilities throughout the United States that are looking to produce biochar as their main product and not a byproduct of energy production. What does this mean? It means that there is serious interest in producing a quality biochar that can be monetized to support employees and has a market for consumption.
Biochar does have limiting factors involving scalability. There are three main factors to scaling biochar:
- Feedstock/biomass to produce biochar
- Availability of pyrolysis, gasification and other machines to produce biochar
- Means to transport the biochar to farmers
These three areas are manageable, but require support from industry and government. There is substantial feedstock available. Biomass can be trees responsibly removed from the forest by Forestry Departments. Biomass is found in the corn stover after a farmer’s harvest and grasses from the fields. Biomass is continuously being produced by the farmers we are asking to use biochar in their fields. Other sources of biomass are forestry waste, treated human waste, industry wastes. For example, the total amount of green tons (biomass) in Oregon and northern California alone is estimated to be over 12 million tons just from thinning in the forests (Ref: http://fingerlakesbiochar.com/debunking-the-biochar-deforestation-myth/ ).
The availability of pyrolysis, gasification or other improved technology to produce biochar is rapidly improving. The basis for these units has been proven over time and effective in making usable biochar. It is not unreasonable for a modest company to produce anywhere from 10 to 100 tons of biochar a day. Larger scale operations are also possible.
In regards to the issues of transport of the biochar to the farmland, there are current logistical systems in place to bring farmers seed, fertilizer and other materials in large quantities. Depending on the farmer, they can use a regional storage facility to purchase and bring their biochar to the field. Larger farms may have the ability to store the biochar on site for future use. The biochar can be stored outside in all climates year around. Biochar is made to be in the elements.
There are strong positives to the scalability of biochar. Once a field has had biochar incorporated into the soil the biochar will remain there for years to come. Farmers can monitor their soil health and determine if more biochar is beneficial over time. Farmers with land that is not farmable due to poor soil conditions can be saved with biochar. Biochar’s ability to increase beneficial microbes, carbon content, aeration, water retention and remediation of harmful organics and metals can be an invaluable tool for a farmer to take advantage of previously un-farmable land.
The relationship between the total amount of farmland, the amount of fertilizer used on the land and the amount of biochar needed to sequester the excess nitrogen is scalable and proportionate to the farm. Whether the farmer chooses to apply smaller percentages of biochar over time to spread out costs or has the means to employ all the needed biochar desired at one time will still have positive impacts on nitrogen retention.
Farming equipment is capable of spreading biochar as a soil conditioner. There are multiple ways to apply biochar on a field. It can be dumped from the back of a truck and then plowed into a field. The biochar can be mixed with a dry fertilizer and spread in combination. Biochar has the ability to be a granule that mixes well with other solids. It can also be made into a fine powder that can be mixed with the solution and sprayed through a nozzle. Best practices would dictate that the media and method to control the nitrogen loss in the fields be adaptable to the current farming practices. Biochar has the flexibility to be incorporated into many methods of delivery into the soil.
Supply vs. Demand
Feedstock will increase through coordination with farmers for crop wastes and other industries. Existing farm service facilities that currently support fertilizer and seed storage can also be used for biochar storage. For example, paper mills have an enormous waste of cellulose material that can be converted to biochar. The timber industry has large amounts of wood waste that can be converted to biochar. Once a field has been filled with a recommended amount of biochar it would not have to have biochar mixed with it for many years. Soil health could be monitored for future needs.
The issue of handling and health when using biochar is relevant to its scalability. When manufactured responsibly, biochar will receive a USDA Certified Bio-based Product. The manufactured product is safe to handle with minimal issues. Handling it as a fine powder would require proper personal protective equipment similar to any handling of a powder. Biochar made for agricultural use is not meant to be a fuel but could burn in proper conditions. Biochar is not a charcoal. It does not have oils and other components that increase thermal releases of energy. Most biochar is transported in bulk with a moisture content between 30% and 50% water. The moisture keeps the granules from easily taken by the wind.