Landscaping With Biochar

Michael Urban


There is exciting news about Biochar or horticultural charcoal and its use as a soil amendment.  This information is for landscapers and is all about the history, research, and characteristics of this material that is producing astounding results. The relatively recent implementation of biochar (or horticultural charcoal) as a soil amendment has stirred interest between professional landscapers and their customers, which include homeowners as well as commercial interests such as municipalities, owners of commercial buildings and golf courses.  This is because of its recently understood sustainable characteristics and soil amending properties.  This article is intended to aid your company in understanding the most recent and one of the most ancient trends in soil amendments.

Historical background

Dating well before the time of the European explorers of late fifteenth century, Native South Americans learned to use charcoal to amend and improve their notoriously weak soils.  Although rainforest and jungle soils are commonly believed to be extremely fertile, in fact, these soils are naturally very weak and unable to sustain much life – and the thin amount of nutrients vital for agriculture were quickly consumed, requiring the farmer to move on to a different garden plot support his family or tribe.

When man infused charcoal into his plots to create terra preta (Portugese for “dark earth”) the soil fertility in the soils was transformed and this new soil condition enabled the native peoples to live via agriculture in large numbers. Previously, only slash-and-burn techniques were used. The dark earths are believed to be responsible for mythical city of El Dorado.  In the BBC film The Secret of El Dorado (it can be viewed on, a modern archaeologist tells the compelling tale of how terra preta enhanced the earth and is the secret.


Professor Johannes Lehmann of Cornell University’s Department of Crop and Soil Science is leading the way, having conducted extensive research on terra preta and the effects of biochar in the soils. He is, perhaps, the leading expert on the effects of biochar as a soil amendment and a means for carbon sequestration and as a potential means to reduce greenhouse gas emissions.

Dr. Lehmann has created a video called “The Promise of Biochar”
which explains that while making charcoal is perhaps the oldest manufacturing process known to man, it has only recently been rediscovered as a means to sequester carbon and to dramatically amend poor soils. Dr. Lehmann also has authored a scientific textbook:   Biochar for Environmental Management: Science and Technology.  He and others in the field are using it to teach a generation of soil scientists. 

All over the world many other individuals and agricultural institutions all over the world are conducting trials, research and studies on the efficacy of biochar as a soil amendment.


Charcoal has two significant properties:  permanence and porosity.  Under a microscope, charcoal is filled with microscopic pores.  The pores enable the charcoal to absorb and retain not only moisture, but perhaps more significantly - NPK (nitrogen, phosphorous and potassium) and other valuable nutrients.  In normal fertilizer applications, many of these nutrients would be washed away, producing run-off, and increasing the requirement for repeated fertilizing.  With biochar present, however, more of the nutrients are retained – reducing run-off, the associated ground water pollution and the need for re-fertilization.


The microscopic pores in the carbon additionally provide a haven for microbe activity – enhancing the fertility of the soil in a very real way.  Given the relative permanence of the carbon – its ability to remain in the soil over time (case in point: the pre-Columbian terra preta soils are still present in Amazonia) – this change in the fertility increases over time with subsequent applications and permanently enhances it.   So consider this:  the material (essentially Carbon) is organic and permanent.  These characteristics are very special for agriculture and could represent a significant addition to the business of landscapers.

Our understanding of biochar is still evolving.  One thing for certain is that because the carbon is permanent when put in the soil, the soil becomes a carbon sink – and it becomes a permanent repository – reducing its potential to become a greenhouse gas. Thus, while even in limited home or commercial use, biochar in a small but real way reduces greenhouse gases, and justifiably earns the distinction as the most effective of all soil amendments.

Basic Q&A for the Landscaper

“As a landscaper, how do I put biochar to work in my business?”

·       If your business is in an arid area, then biochar will help treated soils by retaining moisture due to its porous and absorptive qualities.

·       If your business is in an area where soils are tight clay, then biochar will lighten the soil, improving tilth - making soils workable with a trowel that normally in summer have the quality of cracked concrete.

·       The weaker the soils, the more dramatic the results – relative to enhancing soil fertility.

·       If your customer is interested in making a difference with a sustainable gardening practice that will demonstrate his or her good earth stewardship – this will spark an interest.  Building the soil and improving it with biochar is a sustainable undertaking and a long-term investment – compared with the short term beauty resulting from the addition of fertilizers and even compost alone that has temporary benefits.


Coastal soils are thin and have poor fertility because of their sandy texture, low pH, and low organic carbon content.  Biochar or horticultural charcoal can permanently reverse those characteristics as proven by Dr. Jeffrey Novak (USDA).  His success improving these soils with the use of Biochar is published.


The State of Florida is initiating an effort to encourage its residents help reduce chemical run-off, reduce the use of fertilizers and pesticides, reduce ground water exploitation.  Biochar can be part of a well-considered campaign by homeowners with the help of landscapers to support the Florida State government’s Florida Friendly initiative.


Learn about permaculture and the role Biochar can contribute to the creation of a permaculture experience.



How is biochar made?

Pyrolysis (see web definition) is thermal reduction of bio mass in the absence of oxygen. Ideally the process should occur between 450 and 600 degrees Celsius, because it is in that temperature range that the optimal soil characteristics are achieved.   Once the organic material has been reduced to char, but before it turns to ash, the process is stopped.




One ancient method utilized a wood pile covered with moist earth with a vent on top and a heat source on the bottom





This is the TLUD or top load updraft technique has been developed for very small scale production





Modern production equipment such as these portable systems that enable relatively large scale production.


Ideal production methods include the capture and recycling of all energy and emission and preventing any greenhouse gases to escape.  Some have manipulated feedstocks, time and temperatures, to produce "Designer Biochars" or boutique chars with differing Ph levels and nutrient absorption characteristics that meet the needs of particular soil types.



The cost of producing and shipping biochar is high – and boutique biochar’s cost is even higher, making the retail sale somewhat challenging; and yet, the magic of it —the history of terra preta, its sustainability, and its soil amending properties – once understood by your customer can quickly make a sale and an installation at some level possible.


More can be found on biochar by looking up Josiah Hunt (of University of Hawaii)’s and his excellent article.

In the short-term, you are adding a unique insight and value to your service which your competition does not. Many people feel responsibility towards the earth, and the use of biochar enables allows that desire to be fulfilled. As a long-term investment, landscapers will find an eager audience to foster the stewardship of a greener, healthier planet. Biochar can be equated to the homeowner’s next metaphorical Prius. Because so few people know about it, the opportunity from landscaper’s perspective is relatively limitless; thus, those who use and sell biochar are considered early innovators of sustainable agriculture at a local and very personal level.


Other Benefits:

Resistance to Plant pathogens, molds and mildew has been shown in the roses, tomatoes and peppers. The mechanisms for these broad benefits are currently in great debate by soil scientist. What is not debatable are the fabulous results achieved in temperate and tropical soils.
Biochar has also found great utility as a bulking agent in active compost processing. The absorption characteristics produce a compost that retains much of the nitrogen that is normally lost to the air as the microbes do their composting work.

Economical benefits over time

Biochar’s permanence enables the application the material gradually, over time. For example: on a lawn that has been aerated or thatched, or had a small amount of charcoal applied under sod could be applied in subsequent applications over time to spread out the cost.  The initial investment will not be wasted or lost because the permanence of the charcoal.

Application Rates

Much of the research done today is aimed at determining best application rates for what plants in what soils and in what climates. Here are some tips in biochar application:

  • 5 -20% biochar in the native soils in blended combinations with other organic materials such as manure mixed into the prospective root zone of the plant.
  • The charcoal is best if it is pre-treated and not put raw in proximity to a seed or a seedling.
  • More biochar can be added to your soil over time.
  • Top dressing beds will require time to enable the charcoal to work its way down to the root zone.
  • After thatching or lawn aeration, charcoal alone or in combination with fertilizer can be applied with a spreader.  It can also be applied under sod.
  • Keep records.  Do experiments.  The biochar community will be grateful for results and reports on trials.

The opportunity for the landscaper then, clearly, is to learn for himself; to educate his prospect, to add value to his service by implementing charcoal or biochar to the gardens and lawns of his customers and to profit as a result. 

Special thanks to Mr. Hugh McLaughlin and Mr. Erich Knight for their assistance in developing this article.

Michael Urban


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