What does ancient Terra Preta in Amazon Forests have in common with Eldorado, modern day Biochar, Black Revolution in agriculture, and local Gasification Initiative?

By Nancy Cooper and Matt Newman (Aries Clean Energy), Forbes Walker, Ph.D. (University of Tennessee, Knoxville), and Natalia Smothers (Your Green Homestead)

Wouldn’t it be great if our soils retained a porous aerated structure without annual digging, provided a reliable long-term housing to beneficial microorganisms, regulated moisture levels by sponging water during rain and releasing it in drought, maintained its fertility for decades and centuries without constant addition of fertilizers, composts, and mulches, accelerated plant growth, neutralized methane gas and any toxic spills or contaminants, and cleaned our rivers with the runoff water from the fields – all this while sequestering carbon from the atmosphere and contributing to the production of clean renewable energy? As you will see in the summary of inspirational stories in this article, all this is not only possible, this soil revolution is already happening right now. Even better news is that you personally are able to accelerate this movement by increasing the demand for sustainably-produced biochar soil amendment and adding it to your soil in your houseplant pots, greenhouses, your front and backyard, and/or crop-producing fields on your homestead or farm. Many local Gasification plants in various parts of the world, including Tennessee, produce this biochar as a byproduct of a non-polluting renewable energy process and are happy to pass it to farmers. In this article, you will learn what is biochar, how it was discovered, why it is important for climate change reversal, how it benefits our soils, and helps us process waste biomass into non-polluting source of energy. This article and the Events listing also include the information about the upcoming Tour of the Gasification Initiative in the City of Lebanon, Tennessee on August 14, 2019 at 4:00 PM.

What is Terra Preta?

According to Project Drawdown, “in ancient Amazonia, the waste disposal method of choice was to bury and burn. Wastes were baked beneath a layer of soil. This process, known as pyrolysis, produced a charcoal soil amendment rich in carbon. The result was terra preta, literally ‘black earth’ in Portuguese. Today, terra preta soils cover up to 10 percent of the Amazon basin, retaining extraordinary amounts of carbon”. [1]

This discovery was made in Amazon forests not long ago – at the end of the 20th century by a group of researchers who found pieces of pottery with intricate design from unknown ancient civilization between layers of black substance that was determined to be a charcoal-like biochar. A BBC documentary The Secret Of Eldorado – TERRA PRETA [2] makes a connection of this discovery with the stories of the Spanish explorer and conquistador Francisco de Orellana in the 16th century who was the first European to navigate the entire length of the Amazon River and witness an advanced civilization along the river. It is thought that the consequent expeditions could not locate these settlements due to the population being wiped out by the smallpox and other European diseases [3].

Credit: www.BBC.co.uk/horizon (2002).
BBC documentary about the discovery of biochar

Black Revolution in Agriculture

In the main featured image by Jim Richardson at National Geographic Creative, “researchers and archeologists from Embrapa, a network of Brazil’s agricultural research stations, hover around an excavation showing how deep biochar (terra preta) is buried in Amazonian soils. In Manaus, the Embrapa staff has planted annual crops in terra preta–laden soils for forty years and has been unable to exhaust or ruin their fertility or productivity” [1].

The BBC documentary [2] shows some experiments by a team of Cornell University researchers comparing crops planted in biochar-rich terra preta and an average tropical soil with low nutrients due to the heavy rains washing them away. The crystalline-carbon structure of biochar with a lot of small pores provides housing to soil microorganisms and retains water and minerals for slow release, substantially reducing the need for yearly application of fertilizers and irrigation. “Some scientists call the potential of terra preta nova the equivalent of a ‘black revolution’ in agriculture” [1].

Carbon Sequestration

“When biomass decomposes on the earth’s surface, carbon and methane escape into the atmosphere. Biochar retains most of the carbon present in biomass feedstock and buries it. Rendered stable, that carbon can be held for centuries in the soil—a much-delayed return to the atmosphere. Theoretically, experts argue, biochar could sequester billions of tons of carbon dioxide every year”, placing it among top 80 solutions on the Project Drawdown list for reversing climate change [1].

Fo sale on Amazon.com

Byproducts and Gasification Solutions

“Biochar is commonly made from waste material ranging from peanut shells to rice straw to wood scraps. During the slow baking of biomass in the near or total absence of oxygen, gas and oil separate from carbon-rich solids. The output is twofold: fuels that can be used for energy and biochar that can be used to enrich soil” [1]. There is no ash product that requires disposal.

This wasteless process has attracted many energy and investment companies to fund numerous Gasification installations in all regions of the world, including the United States. The main feature of the gasification plants is a sizable kiln/furnace that bakes the organic biomass in the absence of oxygen and chemically decomposes it at elevated temperatures (typically above 430°C/800°F – half of the burning temperatures). This process is known as pyrolisis. Please feel free to view the comparison of several forms of biomass conversion processes in the Biomass 101 video by Student Energy [4].

Credit: Biomass 101 by Student Energy (2015)

During the pyrolitic baking, majority of the commercial installations collect the resulting syngas and bio-oils and processed them further. Some installations burn them for energy and electricity similar to natural gas plants, and some more complex plants convert them into gasoline-like green fuels that are chemically identical to fossil fuels. In most cases, about 85% (by weight) of the raw material in the kiln is converted to fuel gas with the remaining 15% becoming biochar. The biochar is typically cooled off, tested for carbon content, packaged, and sold for agricultural use.

As an example, the U.S. based Cool Planet was funded in 2014 by world’s biggest energy companies, including BP, Exelon and ConocoPhillips, and constructed a plant in Louisiana with annual production capacity of 10 million gallons of fossil fuel-like gasoline [5]. Their biochar co-product CoolTerra [6] has been sold on Amazon.com since 2015 and currently indicates that it is made 100% from coconut shells.

Aries Clean Energy in Tennessee

Aries Clean Energy headquartered in Franklin, Tennessee is specializing in the design and installation of innovative downdraft and fluidized bed gasification systems that provide for the sustainable disposal of waste, reduction of carbon emissions, and the production of clean thermal and electrical energy. For example, one of their current projects is the Gasification Initiative in the City of Lebanon, Tennessee that has the capacity to produce electricity equivalent to the needs of about 300 households [7]. Within 24 hours, it is able to process about 60 tons of waste (usually the wood that is diverted from landfill) and reduce it into about 3 tons of biochar.

Credit: University of Tennessee Institute of Agriculture (2017)
Gasification Initiative in the City of Lebanon, TN installed & operated by Aries Clean Energy.

In the spring of 2019, Aries Clean Energy announced about its Aries GREEN™ biochar product earning two certifications: (1) the U.S. Department of Agriculture (USDA) Certified Biobased Product label and (2) certification from the International Biochar Institute (IBI). The product is now able to display both the USDA label and the IBI Certified™ biochar seal. Why is this important?

“Consumers can confidently use the certified product on houseplants, lawns, and gardens knowing that it is 96% carbon, and nothing in it is harmful because it has been through independent testing,” explained Gregory Bafalis, CEO of Aries Clean Energy. “Our biochar is a product of a renewable energy process. When waste wood is used for our fuel, it is diverted from the landfill. We never cut down trees for feedstock. The biochar community recognizes IBI as a credible brand. Buyers are assured that biochar with the IBI Certified™ biochar seal meets the IBI Biochar Standards for material characteristics and passes screening tests for certain potential toxicants.”

Even though Aries GREEN™ biochar is not the cheapest on the market, the testing and the IBI certification seal provide the assurance of its safety and justify its premium. Please visit the Biochar Information web page on Aries website to learn more about Aries GREEN™ [8]. It is now available for sale in two sizes (4 quarts and 5 gallons) on the Aries website and the Amazon marketplace.

Tours of Aries Gasification Initiative in the City of Lebanon, TN

Aries Clean Energy is organizing free tours of the Gasification Initiative in the City of Lebanon, TN. The first Tour will take place on Wednesday, August 14, 2019 at 4:00 PM, and additional tours will be scheduled on demand. Please feel free to indicate your interest and preferred dates in the Biochar Forum on Your Green Homestead, via the Contact Us form, or by email to info@yourgreenhomestead.com.

In case anyone is interested in purchasing Aries GREEN™ biochar, Aries Clean Energy is offering a special discount on the 4 quarts jug of biochar and even bigger discount (over 50%) on the 5 gallon bucket of the Aries GREEN™ biochar for the tour participants. It will be sold in person at the end of the tour only to those who pre-order it prior to 12 noon on Tuesday, August 13th and bring cash to the tour on August 14th ($20 for 4 quart jug or $34 for 5 gallon bucket). Any purchase is completely optional and is not required for this free tour. The main objective of the tour is to learn about the wasteless production of clean energy.

How should biochar be used in the soil?

The University of Tennessee (UT) researchers have been working on projects investigating potential benefits of using biochar in agriculture for several years. The container growing in plant nurseries had the most dramatic results. When UT researchers added about 25% biochar by volume to pine bark in containers growing hydrangea, the measurements indicated that the need for watering decreased by about 30% because of the improved soil moisture retention with added biochar. Addition of about 10% biochar by volume also had water retention benefit but not as dramatic as the containers with the 25% biochar by volume [9].

Similar moisture retention experiments in sandy soils in West Tennessee left after flooding demonstrated biochar’s ability to make this kind of soil more productive, reduce drought stress, and increase plant growth. In the first year of these experiments, the biochar was able to significantly increase the yields in soybeans in comparison with the regular crops grown without biochar – even in a year when rainfall was above average.  

Overall it appears that biochar has the potential to improve soil productivity in many kinds of soils. As with other soil amendments, it will not lead to improvements in all soils. For example, UT experiments in Lebanon, TN did not show much difference in the crop yields in the fields with regular soil and added biochar (about 10 tons per acre of a fescue-dominated pasture) and without biochar. That year the rainfall was above average and adequate for optimum crop production and most likely responsible for the non-differentiating results.

It appears that biochar’s best fit will be for the use on poorer soils, such as sandy soils and highly disturbed soils, where organic matter content and water holding capacity is low. Biochar may also help build the resilience on many other kinds of soil and make them more adaptable to dry conditions or the next drought.

The UTIA researchers also noticed the ability of biochar to inactivate herbicides when the biochar was applied at the usual level of about 35 tons per acre (about 1 inch in thickness). The following year they tried the lower level of biochar (about 3 tons per acre) and did not have as much of the weed problem.

Credit: University of Tennessee Institute of Agriculture (2018)
Sandy soil remediation with biochar in Jackson, Tennessee and water retention experiments

Other work at the University of Tennessee is starting to look at using biochar to trap nutrients and metals, and even bacteria by filtering water through biochar-based barriers. This work is in its infancy for now. The idea here is to include biochar in the soil mixtures used in rain gardens and/or bio-swales, or to intercept runoff from parking areas and/or dog-parks. This way some potential pollutants could be removed before they reach nearby streams and rivers.   

Enrichment of Biochar

Typically very sandy soils or heavy compacted clay soils benefit from about 10 quarts of biochar per 100 square feet by applying a mixture of 1 part (20%) biochar to 4 parts (80%) soil or compost as the top 3-4 inches of soil around each plant in your vegetable garden. 

The University of Tennessee has not investigated the possibility of enriching biochar prior to spreading it on the fields with compost microorganisms or other amendments – as popularized by some individual farmers online. Dr. Forbes Walker who is leading a lot of research projects at UTIA, has not encountered any reliable studies to support the benefits of enriching biochar ahead of time for a couple of weeks and advocates to just spread it together with compost or fertilizer on the soil for the best results.

If you decide to follow the biochar enriching advice from individual farmers and gardeners like GrowingYourGreens or Plant Abundance, you are welcome to try applying both enriched and pure biochar and then share your results in the Biochar Forum.

We look forward to an exciting journey of reviving an Eldorado dream and building the sustainable fertility of our soils together!


  1. https://www.drawdown.org/solutions/food/biochar
  2. https://www.youtube.com/watch?v=0Os-ujelkgw
  3. https://en.wikipedia.org/wiki/Francisco_de_Orellana
  4. https://www.youtube.com/watch?v=yHWcddUZ35s
  5. https://www.cnbc.com/2014/06/17/disruptors-in-2014-cool-planet-energy-systems.html
  6. https://www.coolplanet.com/about/corporate/
  7. http://www.lebanontn.org/502/Gasification-Initiative
  8. https://ariescleanenergy.com/biochar/information/
  9. https://www.youtube.com/watch?v=rOUwg37N-40

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