Using Biochar as an Ingredient for Compost Making

SoilMatrixNewsletter No. 12

January, 2018

Where did 2017 go?   Now that we are well into the New Year of 2018, this is the year I hope to be making even higher quality compost to spruce up my garden this spring.   This article will be dedicated to the use of biochar as a “carbon” source for making the highest quality compost consisting of all the nutrients plants require and teaming them up with beneficial microbes (bacteria and fungi).

I am referring to two (2) scholarly articles to provide the facts and experimental evidence for this newsletter material:

  1. Linda Chalker-Scott, “Biochar: A Home Gardener’s Primer”, Washington State University Extension Fact Sheet, FS146E, 2014


  1. Daniel Fischer and Bruno Glaser (2012). “Synergisms between Compost and Biochar for Sustainable Soil Amelioration, Management of Organic Waste”, Dr. Sunil Kumar (Ed.), ISBN: 978-953-307-925-7, InTech, Available from:

You may already know something about biochar — how it is made and its claims to be a soil enhancing agent — but understanding exactly how it enhances soils for plants will help you to know how it can be used most profitably in soils and in compost making.

A good quality biochar will be granulated down to particle sizes of 1mm to 5mm, and will have very few, if any, chunks larger than a half inch and very little dust.

Large chucks of biochar are not as effective in soils and composts as the fine textured (1 mm to 5 mm) material on the right.

The organic carbon and porous cavities in the biochar will attract beneficial microbes such as nitrogen fixing bacteria and nutrient transporting fungi such as arbuscular or endo-mycorrhizal fungi. Biochar’s surface area has both negative and positive charges that attract positive and negative charged nutrient ions like nitrogen, phosphorous, potassium, magnesium, calcium, and other micronutrients. During the compost making process, these nutrients have the potential to leach through the compost pile and be lost. Microbes that are attracted to and protected by the biochar also have the opportunity to incorporate these nutrients into their body mass and wastes and upon their expiration, these nutrients are retained in the compost and will be more available to plants as food.

The negatively charged biochar surface area can also increase the amount of hydrogen ions in the soil causing the pH to increase, which may be beneficial for some plants and not for others. This “liming” effect may beneficially treat acidic soils.   If acidic-soil-loving plants are being grown, such as Begonias, Blueberries, Dogwood, Fuchsia, Holies, Hyrdrangeas, Magnolias, this negative impact can be overcome by adding a soil acidifier like Aluminum Sulphate at a rate of about 2.2 lbs (1 kg) per 200 sq. ft. (20 m2).

The benefits of adding biochar to soils and compost becomes very interesting when we begin to consider its positive effects on soil microbes.   The small pores of biochar provide a hiding place for fungi and bacteria that protects them from grazing protozoa, such as amoebas and nematodes. When beneficial bacteria and fungi populations increase in the soil, pathogenic bacteria populations decrease and plant health is improved as a result.

So, given the significance of Soil Organic Matter (SOM) for soil health and the ability for biochar additions to compost to increase this important soil quality, let’s take a closer look at this synergy. An application of well-made compost to soil provides easily accessible carbohydrates for soil organisms and ionized nutrients for plants. Larger soil organisms like earthworms are also positively influenced and these in turn have a positive impact on soil health through their ability to blend the soil (a process called bioturbation) and produce droppings (worm castings) consisting of organo-mineral complexes that are beneficial for plants. Addition of biochar during the composting process increases all of these prospects as discussed in the second reference given above. I have summarized some of this information in the following notes relating to addition of biochar to the residential composting process.

Biochar’s excellent nutrient and moisture holding capacity along with its ability to stimulate and protect the growth of beneficial plant microbes is fully utilized when it is blending with compost.   A number of important research studies are underway to quantify the numerous ways in which blending compost and biochar results in a soil amendment product that is richer in microbes and nutrients along with the benefit of a more resilient soil organic carbon material that is long lasting in a garden, turf, or crop lands. Addition of biochar to the composting process is a technique used by Indigenous people in the Amazon basin some 2000 years ago.

Reference 2 lists a number of potential benefits of including biochar in the composting process that are currently the subject of considerable research. Some of these benefits are listed below.

  1. Because of the higher temperatures encountered during the composting process, “surface oxidation (that occurs when biochar is included in the process) will enhance the capacity of biochar to chemisorb nutrients, minerals, and dissolved organic matter. It is further postulated that this increases the reactivity of the biochar surfaces.
  2. There is evidence that biochar, as a bulking agent, improves oxygen availability and hence stimulates microbial growth and respiration rates. Furthermore, biochar in compost provides habitates for microbes, thereby enhancing microbial activity.
  3. Biochar-amended composts are reported to have increased moisture absorption, which is beneficial to the composting process as well.
  4. Applications of compost only to soils will result in more rapid mineralization and require replenishment sooner than applications of compost-biochar mixtures.

Reference 2 also mentions a series of crop trials involving oats on sandy (trial 1) and loamy (trial 2) soils.   Biochar was added to compost at rates of 0, 3, 5, and 10 kg per ton of compost.   Plant growth was generally increased with increased amendments of biochar/compost blends. The impact is greatest for sandy soil or nutrient-poor soils compared to loamy soils. What is surprising is the impact of these relatively low biochar application rates. Figure 7 in Reference 2 indicates as much as a 100% increase in yields with the addition of only 10 kg of biochar per ton of compost.

The overall conclusion of the research reviewed and conducted in Reference 2 suggests that there is “optimism for synergistic effects of compost and biochar technologies for ecosystem services and for sustainable management of natural resources including organic wastes.

What does all this mean for future biochar amendments for my garden?   Well, I will be incorporating biochar into my composting process to enhance the retention of nutrients and microbial activity to enhance my future soil amendments!

Stay tuned for more results of compost and biochar blending experiments as they become available here!

Thank you for your interest in this topic.

Copyright ©_2017 AirTerra, All rights reserved.

Read More

SoilMatrix Biochar Presenting at ASTech Foundation’s “Next Gen Innovators Showcase, Nov. 3, 2017”

SoilMatrixNewsletter No. 11

November, 2017

As you may have already heard, I have been busy presenting and promoting the “Biochar Revolution” for soil health at as many events as possible.  The next opportunity is November 3, 2017 at the Telus Spark (aka – The Science Centre) building, Calgary, Alberta.  I will have a display in one of the centre’s open areas and you are welcome to come and visit me – your friendly soil geek.  Here is additional information about the event:

Event:               ASTech Next Gen Innovator’s Showcase

When:               5:00 pm to 9:00 pm, November 3, 2017

Where:               TELUS Spark in Calgary – 220 St. Georges Drive N. E.

Parking:             Available on the west side of the building for $5.00

What:                The ASTech Foundation will be presenting awards to this this year’s best innovators in the areas of: Energy, Agriculture, Health, Technology, Start-ups, and Science Fair Innovators.  It will be an excellent opportunity for students, startups, and industry veterans to connect with one another and get inspired for the journey ahead!

Find out more and register here:  ASTech Foundation Next Gen Innovators Showcase Information and Registration

For this occasion I have produced a two-minute iMovie which explains why I see the use of biochar for soil regeneration in Alberta to be more important than ever.

To watch the video, just follow the link…  AirTerra’s ASTech Event Video

Now that you know all about it, I hope to see you there so we can encourage other innovators, be inspired by them, and participate in a stimulating discussion about the path forward.

Thank you for your interest in this topic. We will see you at the end of November.

Copyright ©_2017 AirTerra, All rights reserved.


Read More

Biochar for climate change mitigation (CO2 sequestration) and soil enhancement

SoilMatrix Newsletter No. 9

October, 2017

Welcome back to the SoilMatrix Newsletter.  This issue provides a short set of videos to demonstrate how much research is taking place around the world on the topic of using biochar as a soil enhancement agent and as a way to mitigate CO2 emissions to the atmosphere by CO2 sequestration in the form of carbon.  This was one of the identified unknowns in our July Newsletter.

Click here to read the July SoilMatrix Newsletter

Most climate change measures such as driving an electric vehicle, switching incandescent light bulbs to LED lighting, installing solar panels, geological sequestration of coal fired power plant CO2 emissions, and so on, are considered to be carbon neutral activities. In this edition of the SoilMatrix Newsletter, you will learn how using biochar to enhance your lawn and garden soil, or your farm soil or any soil, actually REMOVES CO2 from the atmosphere by sequestering carbon into soils for 100’s to 1000’s of years.

The following series of short videos were made available by the UK Biochar Research Centre of The University of Edinburgh.   They are evidence of the amount of effort being put towards answering questions relating to the use of biochar for soil enhancement and CO2 emissions reduction.

What is Biochar? by Dr. Saran Sohi…   Click here to view this video

The research hope for Biochar as a climate change mitigation and adaptation technology…

Click here to view this video

Current biochar research at The University of Edinburgh’s UK Biochar Research Centre, by Dr. Ondrej Masek…   Click here to view this last video

My hope in sharing these videos is to demonstrate how a large number of researchers around our planet are now investigating both the benefits biochar has for soils and the effectiveness of long term sequestration of carbon in soils to mitigate climate change.

Thank you for your interest in this topic. We will see you at the end of October.

Copyright ©_2017 AirTerra, All rights reserved.

Read More

Biochar – What’s good, not so good, and what’s not fully understood

SoilMatrix Newsletter No. 7

July, 2017

It’s mid-summer, so let’s enjoy it while it lasts.

This is how the SoilMatrix Garden looked on Thursday, July 27, 2017.

The romaine at the front corner is being consumed (by us). It is also being invaded by the zucchini (must remember not to plant so much of it next year).   Once again, this garden is receiving no chemical fertilizers, pesticides, or herbicides and as little city of Calgary water as possible. We are attempting to bring the soil health up to a level where all of these inputs are happening below ground level via our soil life food web friends.

In this newsletter we will provide a few links to research that indicates the various benefits of biochar soil amendments. I spent some time compiling these for your learning so you can read for yourself how biochar amendments make a difference to your flower and/or vegetable garden.

The concept of using biochar as a plant growth enhancing soil amendment didn’t really enter public awareness until the fall of 2008.   It was previously mostly an academic curiosity that was gaining attention in universities around the globe. Research has since expanded rapidly and today almost every university in every city has some form of biochar research taking place. Most of the papers written about biochar in these academic arenas are steeped in highly scientific language and, as such, are less accessible to the public. An exception to this is a well-researched book by Dr. Paul Taylor, which was written in 2010. A link to the book’s website is provided here:

where you will find free downloads of Chapter 1 as well as a recently written free download by Dr. Paul Taylor.

One of the co-authors of this book is a good friend and colleague of mine, Dr. Hugh McLauglin. Hugh wrote Chapter 7 “How Biochar Helps Soils”. One of the most informative compilations of the benefits, possible negatives, and unknowns of biochar in soils is referenced in this chapter:

“Biochar Application to Soils – A Critical Scientific Review of Effects on Soil Properties, Processes and Functions.” Report of the EU Joint Research Centre, Institute for Environmental Sustainability. Read more here:

To keep this Newsletter brief, I have summarized here the list of biochar’s possible benefits, disadvantages, and some unknowns that require further research:


  1. Biochar is a natural soil ingredient, which is found in soils in most parts of the world.
  2. The principle of improving soils with biochar has been tried successfully in many places over thousands of years.
  3. Plant production has been found to increase significantly after biochar additions to soils. In some cases negative effects have also been reported… see these in the “disadvantages” below.
  4. Biochar produces a “liming effect” to balance acidic soil towards a neutral pH.
  5. Biochar has an affinity for adsorbing contaminants and keeping them out of harm’s way for plants.
  6. Microbial habitat improvement and protection is offered by biochar’s presence.
  7. Moisture and nutrient retention improvements are evident as a result of biochar’s ability to both absorb moisture and adsorb nutrients and retain them longer.
  8. Increases in mycorrhizal fungi abundance is observed – these are fungi that are linked to plant productivity.
  9. Increases in earthworm abundance are observed.


  1. The use of biochar is well documented for only a few geographical locations. Much more research is needed to fully understand its benefits or disadvantages in soils around the globe.
  2. Soil loss by erosion can be an issue when top dressing biochar to soils. This occurs by wind and/or water transport of small, light biochar particles.  Proper incorporation into a soil blend is necessary.
  3. Risk of contamination of biochar exists (PAHs, heavy metals, dioxins) when contaminated feedstocks are used and/or the process conditions used to make the biochar are such that temperatures are greater than 500 C are used.
  4. Residue removal for use as a feedstock for biochar production could result in reduced incorporation of crop residues into soils and potentially lead to negative effects on soils. This would be the case if farmers were to use all of the straw produced in a field to make biochar, for example.
  5. Extremely high rates of biochar application could have negative effects on earthworm survival rates; however this would be in cases where application rates are greater than 67 kilograms per square meter of land – an impractical level of biochar application.


  1. Emperical evidence is extremely scarce (at this time) for many modern biochars in soils under modern arable management.
  2. The ability to sequester carbon in soils amended with biochar is still largely unquantified and requires further research.
  3. Biochar’s effects on the nitrogen cycle depend on many factors which have not yet been fully explored.
  4. Biochar benefits may be crop and soil dependent, which may be an issue given the irreversibility of biochar once applied to the soil.
  5. Distribution and availability of contaminants that are adsorbed by biochar (heavy metals, PAHs) require further research to assess the rate of bioavailability and toxicity of the contaminant depending on the biochar type, application rates, feedstock, production conditions, soil types, and environmental conditions.
  6. More research is needed to fully map the life cycles of biochar’s effects on soil organic matter.
  7. Issues of pore size and connectivity and the optimum particle sizes for biochar that is amended for soil enhancement still requires research.
  8. Soil water retention and availability requires further research for variations in soil type.
  9. Effects on larger soil organisms – such as contact of skin with biochar in soil for larger organisms.   This is still in the early days of research.
  10. Hydrophobicity of biochar in soils remains largely untested.
  11. Rate of decomposition of biochar as a function of agricultural management requires further research.
  12. There is a good potential that biochar can improve “Cationic Exchange Capacity” of soil – a facilitator of nutrient uptake by plants.   However, the effectiveness and duration of this effect after addition to soils remains poorly understood and requires long term experimentation.

Given these point form benefits, negatives, and unknowns, there seems to be much more in the “unknown” category, which is the reason for the huge interest in this topic at leading research institutions around the globe.   Much more will be discovered about biochar in the coming years. It could makes for an exciting career for budding agronomists, biologists, and soil scientists.

We hope to keep you informed as the results from all this research becomes available.

Thank you for your interest in this topic. We will see you again at the end of August.

Copyright ©_2017 AirTerra, All rights reserved.

Read More