Acidic Soils & Biochar

I suspect that many people don’t yet realize it, but acidic soils are a growing problem (so to speak!) around the world, already impacting more than 50% of soils used or suitable for agriculture.  Humans are both the cause and the casualty of soil acidification, though other biota are also impacted. We humans have come up with various solutions to combat low soil pH each with their own pros and cons some of which are outlined in a recent paper on this topic by Dai et all (see my summary infographic above).

In attempting to parse the biochar qualities that are relevant to increasing soil pH, the authors highlight feedstock and production temperature as being critical to designing or selecting the right biochar for this particular task.  They note that higher temps tend to increase fixed and total C, pH, ash, total exchangeable and soluable base cations and surface area.  At the same time however higher temps tend to lower yield, volatile matter, total O and CEC.  Generally speaking though if a ‘soil toiler’ wants to increase pH using biochar, so far the best advice points to using relatively high temperature chars (e.g. ~600C) from manure biomass or using a blend of biochars made from different feedstocks.

The discussion on mechanisms or how biochar reduces acidity, gets deep into the weeds of agronomy, but these are the general takeaways from my perspective:

  • Soil acidity: alkaline biochars help acid soils but not alkaline soils – pretty logical!
  • Certain biochars reduce Aluminum (Al) bioavailability & thereby its toxicity to plants; high surface area chars may provide more adsorption sites for Al and other metals
  • Nutrient Availability – research is all over the map at this stage with one of the only consistent findings being that manure chars have more nutrients than chars from plant or woody feedstock.  This is widely acknowledged in the literature.
  • Soil nitrification impacts – also seemingly inconclusive at this stage with much more research recommended.

Lots more work to be done on this subject, especially on long-term impacts of biochar and other soil amendments on soil pH, but overall it was a hopeful read!


Reinventing Math: turning negatives to positives

Remember those ridiculous word problems in math class that were laughably convoluted and unrealistic? What if we were to inject a bit of reality combined with some consciousness-raising into word problems. We could get kids motivated to solve real world problems and oh, by the way, learn a little math in the process. Here are some possible word problem examples (which of course involve biochar!) based on a recent New York Times article about air pollution in India.

India produces 34 M tons of crop residues, mostly rice and wheat straw.   Although illegal, most farmers burn the straw as this is the quickest way to clear fields for the next crop. Instead of burning, which contributes significantly to air pollution, farmers could carbonize these residues, creating a valuable nutrient carrier, biochar, which can also sequester carbon in the soil.  Solve the following problems:

  1. 800 liters of straw will yield 200 liters of biochar.  What is the yield as a percent?
  2. If all farmers in India produced biochar instead of burning crop residues, how many tons of biochar could be produced?
  3. If straw char contains 36% carbon, how many tons of carbon could India create from crop residues per year?
  4. A typical car emits 4.7 metric tons of greenhouse gases per year.  What is the equivalent in the number of cars, to the amount of carbon which India could create if all crop residues were carbonized?
  5. A small farmer with 1 hectare is fined USD$38 for burning his crops.  Crop residues per hectare vary from .4 tons – 3.0 tons depending on many factors.  Assume Farmer A has 2 tons of crop residues and that one laborer who is paid $8 per day can harvest and carbonize 800 kg of straw in one day. Will the farmer be better off burning his crops or carbonizing them?
  6. How much biochar will Farmer A produce? 
  7. For every kilo of biochar produced, assume the farmer can reduce purchases of lime for his fields. (Lime is needed for fields that are acidic.) Lime costs $30 per ton. How much will the farmer save assuming a 1:1 ratio for biochar:lime.
  8. What is the effective cost of producing biochar when labor and savings in lime are included?

The list of word problems could go on and on just for this single scenario.  The questions could even get more complicated for older students, but you get the general idea. Math word problems could be customized for different regions or for different problems which resonate with different cultures around the world. 

Maybe, just maybe, if we create a math curriculum focused on climate change solving math word problems, we could start turning negatives into positives….in more ways than one!  Kids could educate their parents on this new math, offering new solutions which will not only reduce air pollution and rebalance carbon levels but could also improve farmer livelihoods too!



The walls we should really be building: C-walls!

Recently my ‘charmigo’ Ramon, who hails from Mexico, told me the only way he would support Mexico paying for a wall is if it was made from biochar.  The chuckle I could not suppress was filled with gallows humor. Still it got me thinking, not so much about walls, especially not between the US and Mexico which I believe is a complete waste of time and money as our US food system would quickly unravel if we did not receive the benefit of hard working Mexicans – but about other possible biochar based barricades.  Indulge my current biochar fantasy if you will please…

Although many would like to believe the biggest threat to civilization is citizens of one country trying to enter another in an effort to escape famine or fighting, the real threat to humanity and many other life forms is sea level rise. Below is a map of what a future USA could look like if the Arctic  ice keeps melting.


Forecasts from 6 – 12’ sea level rise are being projected with more and more certainty. Pretty dire any way you look at it.  Many threatened cities are talking about building sea walls to protect themselves.  But Mother Nature has a way of overcoming many manmade structures.  Which got me thinking about mountains – the ultimate land structure that stands up to rising tides.  Which got me further thinking about these kinds of man-made mountains, which I normally bemoan:

 What do all these capped landfills have in common?  On the upside (so to speak) they are tall, far higher than the worst case scenario of 12’ sea level rise. On the downside, they are pretty darn ugly and largely devoid of biodiversity. Oh, and most belch CH4 for up to 20 years after they are capped adding more fuel to the climate fire.  So creating a great wall of garbage mountains to fend off the rising seas is definitely not the answer. Besides most neighborhoods understandably detest them as they smell and decrease land values.

But what if instead of garbage under them there hills, we put lots and lots of carbon in the form of (mostly) biochar?  Create our own ‘Sea era Terra’ or Sierra Terra (a sierra is a chain of hills or mountains) as it were. Of course the entire ridge could not consist solely of biochar since that would not be structurally viable, but as our indigenous brethren in the Amazon and other cultures discovered, lots of other organic waste could be mixed in to add structural integrity and biological diversity to the mound. Blending charred and uncharred organics (and perhaps some non-toxic organic waste such as crumbled concrete), layer by layer, could build mountains of bounty where trees could be planted to further help pull down CO2 from the atmosphere.

As to the question of where to build, of course current beach homeowners would never allow a C-wall to be built to block their views (short term thinking!). Somehow we seem to have found a way to build pipelines over thousands of mills despite the fact that they destroy lands and landscape, so perhaps there is a way to find land for constructing climate cliffs. If successful such a wall has the potential to enrich a whole new corridor of real estate owners which might suddenly become coastal communities.  So the sales pitch to land owners would be more about potential land enhancement  rather than environmental hazards.

As to the question of with what, no need to fear that food growing land must be converted to biomass for biochar production.  On the contrary, as I have stated many times in this blog the world is nearly drowning in unloved biomass which could be carbonized.  Just recently a company told me they will soon be producing 20,000 tons of biochar per year from sewage sludge and tree debris in a small town not too far from me.  Converting tons to volume with biochar can be tricky and variable (due to density, particle size, etc.) but imagine 20,000 super sacks (which are already being used to reduce flooding elsewhere though not filled with biochar). Although super sacks come in all sorts of sizes, let’s take your average 2.5′ squared and tall sack for a bit of back of the envelope calculating.  There are 5,280 feet per mile, so 2,112 sacks would be needed per mile and a single layer would be 2.5′ tall.  That means this one small town could build a 2 mile long x 12′ tall carbon corridor from pyrolyzed sewage and tree waste in just one year.  That’s pretty astonishing when you think about it.

(Please note that I’m am not advocating for walls like this one, but rather mountains that promote biodiversity and beauty, but this gives an idea of how quickly and how far carbonized waste could go.) How to create such carbon filled precipices before humanity reaches that other looming precipice…that is the question that fueled my latest fantasy.

Biochar vs Activated Carbon

One of the most compelling above-ground markets for biochar is as a substitute for activated carbon. Activated carbon is used in a wide variety of applications from filtration to remediation. Problem is AC comes with a heavy carbon footprint and it’s not cheap. A recently published meta-analysis compares the energy demand, the GHG emissions and the economic performance of AC versus biochar used to filter certain heavy metals.

The authors compared LCA data from a variety of different ACs against 28 different types of biochars.  The amount of energy required to make the various ACs ranged from 44 – 170 Mj/kg whereas the biochars required significantly lower amounts ranging from 1.1 – 16 Mj/kg. That shows that biochar needs 90% less energy to be produced! Somewhat surprisingly the chars at the lower end of energy requirements include chars made from digestate (1.1), paper sludge (1.1), and whisky draff (1.1) – which are all relatively high in moisture content.

On the GHG front the news in even more promising. Whereas AC production is responsible for 1.2 – 11 kg CO2 eq/kg, all of the biochars analyzed had net negative emissions from -.1 to -3.5 with miscanthus char showing the most sequestration potential.


Comparing economic performance must take into account both price and adsorption capacity.  I have a disagreement with the authors on the pricing data used for comparison purposes.  While efforts were made to contact multiple vendors to get an average price, the price used in the study for biochar is US$5/kg (i.e. $2.27/lb or $4,545 per short ton).  Although these prices might represent retail prices for small quantities of biochar, no one that I know in the biochar world is selling char for >$4,500 per ton! In fact as more and more production capacity is coming on line, the price is coming down rather substantially.  Depending on the type of biochar and the demand for that particular char, current prices seem to range from $500 – $2,000 per ton (i.e. .55 – $2.20 per kilo).

The authors include an excellent table which provides comparisons of the adsorptive capacity of different ACs and biochars for 4 different metals: Chromium, Cadmium, Copper and Lead. Using this data and a normalized price for biochar, an economic performance comparison is provided. The ranges for adsorption capacity are provided below combined with the economic performance as stated by the authors (v1) and a revised version based on more realistic biochar pricing as stated by yours truly (v2).


What is most interesting to me is a comparison of the best biochar against the best AC.  For each metal there was at least one biochar that had higher adsorption capacity mg/g than the best AC. Not only that but some of the biochars that out-performed AC had significantly lower surface areas (e.g. dairy manure biochar, the best performing biochar for cadmium filtration has a surface area pf 5.61 m2/g vs the best performing AC which had a surface area of 984). This indicates that something other than surface area is responsible for the high rates of cadmium removal (51 mg/g for dairy manure biochar vs 8 mg/g for AC).

When more realistic prices for biochar are taken into consideration, the economic performance of biochar versus AC for heavy metals removal becomes even more favorable. The take-aways from this and a growing number of peer reviewed studies on the use of biochar to filter both toxins and nutrients are that 1) significantly less energy is needed to produce biochar based adsorbents; 2) the GHG emissions related to production for biochar are all negative as compared to all positive emissions for AC; and 3) biochar is significantly cheaper than AC for metals removal. That should be a pretty compelling value proposition. The key will be, as with all things biochar related, to select the right biochar for the job.  This study shows that what you are removing may require a different kind of biochar, but perhaps the ultimate solution will be a blend of different biochars.

Biochar stability vs Carbon stability


Next up on my reading list from the biochar bible, is Chapter 11 “Movement of Biochar in the Environment”.  Rather unsurprisingly something light and fluffy such as biochar is fairly mobile.  It can move both vertically down into the soil profile and horizontally across the landscape and into water bodies.  Lots of different forces cause this movement as can be seen from my one page overview above.

It is possible, in some scenarios, say for example freshly top-dressed, hydrophobic char applied on steep slopes with no soil cover, that quite a lot of char could be eroded away during the next big rain (similar to how freshly applied Nitrogen gets leached away). The final resting place of that biochar varies largely depending on topography, but there is a good chance that it could still sequester carbon whether it is in the soil or in a body of water. If char simply moves across land, it may fractionate and some tiny particles may volatilize, but much of the char will simply be moved from one spot to another – much to a farmers chagrin.  If it lands up in water, the carbon may still remain as carbon, but as with so many things related to biochar ‘it depends’! From what I can tell after reading this chapter, a lot more research is needed to really assess carbon stability in real-world vertical and lateral transportation scenarios of biochar.

If you want to reduce mobility, here are a few things to keep in mind:

  • Particle Size –larger particle may fractionate into smaller ones when hit by raindrops; but smaller particles will tend to leach and erode more quickly;
  • Hydrophobicity – fresh char, especially made at low temps (<500) is likely to move more
  • Soil texture matters as always! Sandy soils will experience more leaching & erosion.

What they didn’t say: A lot of chatter about biochar tends to tout ‘once & done’ benefits of biochar but in fact according to this chapter biochar can be quite mobile so ‘once & done’ could end up as ‘once & gone’ under the right (or really wrong) circumstances.  Ancient soils such as Terra Preta in the Amazon or the Plagganthrepts soils in Europe (see picture in lower left hand corner above) are not the result of single applications.  These soils were continually amended with char and other organic wastes for decades or centuries and created a deep dark soil profile that has persisted for millennia.  It is highly unlikely that adding a single instance of biochar, even at high application rates, would create similar profiles.  Thus adding lower rates more frequently may be preferable in the long run for both long-term carbon storage and soil fertility.

Biochar & Heavy Metals


I recently took the plunge and purchased the updated ‘Biochar for Environmental Management’ (Lehmann & Joseph 2015), which I often refer to as the ‘biochar bible’.  Any book with more than 900 pages would be daunting, but this one is filled with scientific jargon that would keep your average non-scientist (e.g. me) googling for hours just to get through one chapter! Still if one is to succeed in the world of biochar, it is important to try to really understand where the current biochar research is leading, how to optimize biochar characteristics and how biochar impacts soils, carbon & economics.  This is one of the few books that endeavors to do that.  As I wade through various chapters I thought I would share some of the more interesting nuggets using infographics (an updated variation of ‘Cliff Notes’ if you will) which I designed to help  depict and distill the sometimes dense dissertations.

Having just returned from a visit to China where biochar research is heavily slanted towards remediation of toxic soils, I dove into chapter 20 which is titled “Biochar & Heavy Metals” (Beesley et al).  The above infographic covers the first part of the chapter which talks about how soils are contaminated, how toxicity can be mitigated and most importantly how biochar can remediate toxic soils.  The mechanisms by which biochar can help immobilize toxins deserves an infographic on its own (working on it!), but this first one gives an overall view of the problem and how biochar can help. Hope you find it useful!

How not to pound sand


Sand. How in the world can we be running out of sand? The world seems full of it, right? River-beds, oceans and deserts are full of sand.  Yet according to a number of recent articles, certain types of sand are being depleted so rapidly that some countries are putting bans on exporting it.  Such bans have given rise to sand mafias in some parts of the world.  Such sand mafias, which could have been called  Sandinistas if the name hadn’t already been taken, clandestinely mine river-beds and vacuum ocean floors to sell this finite resource to voracious buyers both far and near, leaving behind devastated eco-systems and sandless beaches.

To what end you ask? Our insatiable appetite for concrete is largely to blame; more specifically for the construction of housing, offices, factories, in fact brand new cities that spring up practically overnight in some parts of the world.  One kilometer of road requires 30,000 tons of sand and a single house can quickly use up to 200 tons (more details here). Concrete accounts for 80% of mined sand usage. Depending on the specific end use for concrete, up to 3 times the amount of sand will be required for every part of cement. Its role is to fill in the spaces of larger aggregates (e.g. stone). Both fine and course sand are used in cement with varying impacts on comprehensive strength, flex strength, permeability, durability, shrinkage, cracking, etc. Desert sand, due to its smoother and rounder geometry, doesn’t work as well as river and ocean sand so it is largely ignored.

Given that I blog about all things biochar, where does biochar come in to play on this most recent tragedy of the commons (i.e. disappearing sand)?  It is no secret that biochar is being tested and used in concrete recipes (see here, here, and here).  To date, however, the motivation for including biochar in concrete has focused on carbon sequestration or to lighten up the weight of concrete.  But perhaps displacing the use of sand with biochar in concrete should focus more on the ecological benefit of saving our rivers, oceans and related flora & fauna from utter devastation.

But since eco-system services is often a tough sell, especially without regulations to control those that feel no shame in ruining the environment, economic impact must be addressed.  Sand is still shockingly cheap (roughly $6/ton) given that it is the most in demand natural resource after water.  At that rate, biochar is unlikely to compete purely on price for a very long time.  However this recent paper suggests the biochar added to cement can help reduce cracking and improve flexural strength as compared to using just sand for the fine aggregate. This same research claims that biochars ‘jagged and irregular shape provides a snug fit to cement paste’.  Earlier research out of Korea showed that certain types of biochar ‘reduces water evaporation from concrete which reduces both the plastic shrinkage and drying shrinkage’.  Thus improving concrete through the use of biochar could potentially reduce liabilities related to concrete failure, or reduce curing time which means faster building, or could provide better insulation which will reduce building operating costs.  If we start to approach the use of biochar in buildings through this lens, it just might attract more interest than focusing on its carbon sequestration potential.  Future research would be well served to use a Triple Bottom Line approach to using biochar in building materials.

How the sea can help rebalance C


This week I happened upon some fascinating biochar research focusing on charring seagrass wrack as a more sustainable means of disposal.  Not only is this environmentally preferable as compared to landfilling it, which causes all sorts of GHG emissions from the decomposition stage, but in all likelihood it could be economically better too.

Let’s discuss climate change mitigation potential first.  The reports states that in a mere 9.5km of Kenyan coastline, 6.8M kg of seagrass (dryweight) carpets the coast on an annual basis.  In their research they achieved biochar production yields of 48 – 57% which is actually pretty astounding and definitely not the norm with most current biochar production technologies.  (They did pulverize the seaweed prior to pyrolyzing so that likely provided increased yield.)  Still for conservative calculations, let’s assume 25%  biochar yield which is far more common.  Using the low end of the carbon content range they found for seagrass of 34.6%, this one small stretch of beach, which is less than 1% of Kenya’s coastline, could sequester more than 2M kgs of CO2e per year – not including calculations for reducing methane emissions from rotting wrack! 

Now on to economics.  Imagine how places like Kenya could benefit from creating sustainable jobs, cleaning up coastlines and possibly even becoming a carbon negative country by carbonizing excess seagrass! On the cost reduction front, the article states that one coastal town in Australia spent more than $28M for wrack ridding in just one year.  While there is a cost to collecting, handling, possibly drying and pyrolyzing seagrass, if mobile units could be taken to affected beaches, costs would most likely be lower, especially if carbon offsets were available. 

Seagrass is not the only excessive bounty from the sea that could be carbonized. Seaweed, an algae that grows 30 – 60 times faster than most land-based plants, is becoming ever more abundant due to fertilizer abuse (amongst other reasons).  Countries around the world that depend on beach tourism are increasingly beleaguered by odiferous mountains of Sargassum seaweed and kelp.  This too often gets carted off to landfills or buried in ditches at great expense, largely born by hotel chains or governments. Carbonizing fast growing seaweed could be a very efficient and relatively low-tech way to rebalance carbon levels and meet CO2 reduction targets while solving other problems that can depress tourism income.

A challenge with this particular type of biochar is likely to be the (relatively) high salt content.  For that reason it may not be ideal for use in certain soils.  However, it could be used in other ways that might help island or coastal communities to adapt to climate change.  Bagging it and piling it up to create artificial dunes could help when storm come and waters rise.  Using it as a construction material for sea walls might be interesting.  Perhaps it could be briquetted and used as green charcoal to reduce deforestation.  Incorporating seachar into salt licks for livestock might even be worth testing.  The point is, uses can be found!

I can’t even begin to calculate what the overall carbon mitigation potential is for all of this excess sea-based flora, but it is, as one of least palatable presidential candidate’s in US history would say, HUGE!

2016 USBI Biochar Conference Recap


The 2016 USBI Biochar Conference flew by in a flash this week.  It was great to see old friends, meet so many folks that I’ve corresponded with but never met in the flesh and to see so many new people that are joining the biochar fray. Academics mingled with industry, government representatives (USDA NCRS and Forestry mainly) chatted with NGOs and Venture Capitalists; Idealists focused on reversing climate change spoke to pragmatists focused on building the next big industry; Newbies met with the biochar literati and technology promoters exchanged ideas with agronomists.  Beyond those from within the US border were attendees from Canada, Mexico, Guam, Norway and South Africa (and probably other countries as well but those are the ones that I met).  It truly lived up to the ‘Synergy of Science and Industry’ theme.

Conferences like this tend to be like a smorgasbord – where there is more than a little something for everyone.  Hors d’oeuvres in the form of table displays showcasing various pre-production & pyrolysis technologies (I was particularly impressed with Forest Concepts “Crumbles” technology) as well as some other non-traditional technologies where biochar is part of an overall system (check out this amazing Algae Aqua Culture Technology).  Biochar producers brought samples and new products which I always love to see (and take!).

Also on the menu was an abundance of biochar presentations – nearly 90 in all.   Presentations were categorized into 4 subject areas: Agriculture/Horticulture, Forestry, Policy, and Stormwater & Remediation. Many of the presentation slides will be added to the USBI2016 website in the near future, so if you are interested in exploring a particular topic a bit further, check that out next month sometime.  I was particularly impressed with the sessions I attended in the Stormwater & Remediation track.  There is so much positive news coming out of that arena in terms of regenerating mine lands as well as using biochar to filter different waste streams.  Several folks are working on the sewage/biosolids and biochar front – both academic but also in terms of production technologies that can deal with high moisture content feedstocks such as biosolids.  Since I just recently wrote about this topic in the Biochar Journal, it was great to find and chat with others focusing on this endlessly renewable waste stream. 

Though there has been a burn ban on in Oregon due to the drought, a few folks did bring some small scale production technologies to display at the conference including a very nice version of the Kon-Tiki kiln, a funky pyramid kiln with the ability to flare off syngas (a new one for me), a rather fancy TLUD, and a little biochar bar-b-que (forgot to take pictures!)

Against the gorgeous backdrop of Corvallis and OSU’s campus, the ambiance, the knowledge sharing and the vibe was really great at this Conference.  Sincere thanks to all of the organizers!


Towards a Biochar Ethos

rhetorical triangle

Jonathan Shapiro’s book “Lawyers, Liars, and the Art of Storytelling: Using Stories to Advocate, Influence and Persuade” has a great perspective on ethos as it relates to Aristotle’s rhetorical triangle.  The biochar world would be well served to understand his thinking.  Ethos is often used to describe beliefs or ideals that define a community. In the context of Aristotle’s rhetorical triangle (i.e. ethos, logos, pathos), ethos refers to credibility.

Credibility can be boosted in many ways.  Clothes credentialize cops, cadets and candy stripers.  Certifications credentialize professions and products.  Testimonials, if provided by respected authorities, can also boost credibility.  Shapiro calls this ‘ethos by extension’.  Oddly enough he then adds “The field of expertise almost doesn’t matter.” This conflating of relevant expertise is something I see in the biochar world fairly often, yet I can’t quite bring myself to agree with Shapiro.  While it might work in a courtroom, I can’t say that is works in corn fields!

The biochar world has all manner of “experts”: agronomists, engineers, business people, climate scientists, farmers, environmental activists and more.  Each brings their own perspective, their own priorities and their own passions to the table.  Yet the question of who is most credible is critical.  It will determine who lives or dies, not only at the company level but for the industry as well.  [I could go on to say quite possibly for the planet as well, but that would likely lower my credibility in the eyes of many!] The question for the biochar community and more importantly for future buyers of biochar, is who to trust when they are talking about biochar? Whom do you trust before you incorporate massive amounts of the stuff permanently into your fields; fields which provide sustenance for you family, your community, and food security for us all. 

This is not a trivial or rhetorical question, nor is there a simple answer.  Scientists are often pushed to publish only positive requests if they want tenure.  Businessmen may take advantage of a lack of scientific understanding by the buying public and make extraordinary claims, perhaps unproven, about performance or may claim that only their product is safe.  Neither of these scenarios helps to build ethos for the individual nor for the industry.

For the biochar industry to succeed, we must take the other path outlined by Shapiro.  Instead of taking advantage of the confusion caused by a new and complex product, we should aim to enlighten and educate.  We should not attempt to sell biochar to everyone everywhere, but to sell the right kind of biochar and/or production technology to the farmer (i.e. ‘the audience’ in Aristotle’s parlance) whose specific constraints it can alleviate.  There are many ways to position biochar, but understanding what is most important to your audience is key to any selling effort. That is a much taller order, a much longer sell, and requires much more than just slick marketing of products with broad generalizations of the potential benefits of biochar.  But in the end, this additional effort will enable biochar to succeed and will facilitate word of mouth selling amongst satisfied customers which at the end of the day is what an industry needs to be truly sustainable.