Carbon Farming & Biochar Workshop Recap

Last Saturday we had the first of what may, if there is sufficient help and interest, be an annual event for the region; a gathering of those interested in carbon farming and biochar.  Thanks to our gracious host Peter Arena, the event was held at the beautiful Boathouse Beer Garden which has spectacular views of Cayuga Lake.  On the agenda were folks representing government, academia, industry and consumers. The quadruple helix as I like to call it. Nearly 50 people gathered to hear about the status and strategy of the recently proposed NYS Assembly bill on carbon farming and learn all about biochar.  Technology vendors and newbies to biochar met and mingled with regional biochar ‘experts’.

NYS Assemblywoman Barbara Lifton kicked things off with a discussion on the NYS proposed legislation.  While there is not currently a twin bill in the Senate, she explained that at least this gets the conversation started.  Miranda Phillips from the Ithaca chapter of the Citizens Climate Lobby spoke about the types of citizen advocacy needed to get bills such as this funded and forwarded.

Dr. Michael Hoffmann, Executive Director of the Cornell Institute of Climate Smart Solutions (CICSS) provided a great perspective on what NY farmers can expect in terms of climate change, both negative and positive, and described various adaptation tools and strategies that Cornell has been working on .  Dr. Johannes Lehmann, one of the world’s leading biochar researchers, spoke about how biochar can actually help mitigate climate change by way of rebalancing atmospheric carbon levels. Johannes is a tough act to follow but I did my best to provide what I call the layman, not Lehmann perspective on biochar.

Technical demos from Biomass Controls, Acorn Biochar, America Sequesters and my biochar buddy Dale Hendricks demo’d a small TLUD stove. I was supposed to demo a Kon-Tiki kiln but was juggling a bit too much to strike a match.  We also had GreenTree Nursery there to show some of there biochar enriched horticultural products and talk about soil matters.  Local organic farmers Gerard Dumphry and Jennine Huber who have been using biochar for nearly a decade showed how they are incorporating it into a soon to be planted organic hop yard.

After a rather unexpectedly long lunch period, which one kind soul said provided ample opportunity for people to meet many interesting attendees, we heard from one of my research buddies at RIT, Steve Barber, on using biochar for filtering food & beverage industry effluent.  Following this was a very interesting perspective on using biochar in a fixed bed biodigester.  This research was managed by Bruno Xavier in Brazil but Bruno is now working in the Finger Lakes – always good to have more people in the region!

Our workshop attracted a number of Canadians including Rasmus Kiehl who told us about the Open Source Biochar Wiki page that he has been curating since 2009!  This is a great resource which I encourage everyone to check out!

Wrapping it all up was a panel of carbon farming and biochar users: Gerard Dumphy of Danby Farms, Dale Hendricks from Green Light Plants who spoke about its use in the horticulture industry and Suzanne Hunt from Hunt Country Vineyards who spoke about building soil resiliency by boosting soil carbon.

We were fortunate to have 2 videographers shooting video for the day so at some point we will have more pictures and video available.

Overall I was very pleased with the variety and enthusiasm of attendees and presenters.  Mother Nature cooperated by providing perfect burn weather.  We even had an exceedingly rare on-site visit by a white deer which must have escaped the nearby shuttered Seneca Army Depot.  Although I’ve seen plenty of white deer within the Depot, I have NEVER seen one outside of the 24 miles of fenced in area.  I think it was a sign, so thanks white deer and thanks also to our host, Peter and all the others that helped make the event a success!

How Biochar supports the UN Sustainable Development Goals

The 17 Sustainable Development Goals (SDGs) adopted by the United Nations are focused on ending poverty, protecting the planet and ensuring prosperity for all by 2030.  These are what are sometimes called BHAGs (Big, Hairy, Audacious Goals) in the business world. Big aspirational goals are exactly what is needed to reimagine, reinvent or in some cases retrofit our precariously unbalanced world.

Wide scale adoption of the production & use of biochar could materially help achieve at least 12 of these goals.  While I could (and may!) do a full blog post on each of the SDGs that biochar could influence, here is a brief overview of which goals biochar can impact with some examples of how it is already working:

Goal #1: No poverty – making biochar from crop waste & blending with animal urine & manure decreases the need for subsistence farmers to purchase off-farm fertilizers and boosts yields.  Farmers in Nepal improved yields by more than 100%

Goal#2: Zero hunger – growing more food, especially in poor soils with increasingly erratic climate, reduces hunger. (see Nepal example above)

 Goal #3: Good health & well-being – using biochar in soils can immobilize certain metals and toxins and reduce the need for chemicals in soils.  Using biochar to filter storm water can reduce E.coli and other bacteria. See the Warm Hearts example in Thailand on replacing chemicals in agriculture with biochar.

Goal #6: Clean Water & Sanitation – using biochar as a low cost water filtration medium can reduce negative impacts of unfiltered effluents.  Carbonizing sewage sludge is a way of reducing volume and immobilizing toxins.

Goal #7: Affordable & Clean Energy – a growing number of biochar production technologies can be used to produce heat and/or electricity and/or syngas.

Goal #8: Decent Work & Economic Growth – carbonizing underutilized biomass which is commonly burned in open fields creates economic opportunity for farmers and other rural inhabitants.

Goal #9: Industry Innovation & Infrastructure – new biochar uses include building materials (e.g. concrete, bricks, asphalt) and other composites. Incorporating biochar has been shown to improve various properties of both concrete and asphalt thereby extending the potential lifespan of the materials.

Goal #11: Sustainable Cities & Communities – biochar has been shown to benefit storm water management, green roofs and urban tree planting. It could also be used to remediate urban brownfields.

Goal #12: Responsible Consumption & Production – converting waste into biochar and using the char to displace high carbon footprint or non-renewable or expensive materials will lead us away from a linear economy to a more circular one.

Goal #13: Climate Action – this would be a long list starting off with the ability to stabilize carbon pulled out of the air via photosynthesis.  Biochar production can also displace fossil fuel based energy.  Fed to cows or added to landfills or manure slurries it can lower CH4 emissions. The list goes on…

 Goal #14: Life below Water – adding biochar to soils can reduce nutrient leaching which is responsible for significant eutrophication around the world. 

 Goal #15: Life on land – reclamation, remediation, restoration are all ways that biochar can improve life on land!

Char putty

DIY slime is all the rage these days.  It’s fun and funny and just plain weird. You can kneed it, bounce it and break it over and over yet it always returns to a gelatinous blob. My teenage daughter has made all sorts of variations of this easy-to-make polymer using just three simple ingredients: glue, borax and shaving cream.  It’s the XXI century version of silly putty which is made with just two ingredients: silicone oil and boric acid.  As I have an insatiable desire to add biochar to almost everything, I decided to fold in some char to my first attempt of DIY slime.  The pictures show the slime before and after adding char (I used particle size <1/20” and a lot more char than is shown in the picture).  It is rather beautiful especially compared to the bland, milky-white pre-char substance. 

But might it have any practical value?  The inventor of silly putty asked this question for years and the best they came up with was a toy; a multi-million dollar toy mind you, but still just a toy.  Might there be some benefit to adding carbon to this particular polymer?  After adding biochar to various materials, my next favorite thing to do is chat with Master Google about big questions such as this, so off I went on my cyber quest.  Lo and behold researchers in Dublin recently blended graphene, biochar’s more sophisticated and expensive carbon cousin, with homemade silly putty.  Alas my idea was not so crazy – nor original!  Dubbed ‘g-putty’, this polymer turns out to be a highly sensitive sensor which may just have bio-medical applications.  Researchers claim that g-putty could, amongst other possible uses, be used to track human vital signs.  Its ability to conduct electricity is what appears to be the basis for its high level of sensitivity.  Fascinating!

One thing I’ve pondered ever since a good friend battled chemo-induced neuropathy is whether biochar could somehow help expunge or pull out the toxins pumped into the body during chemotherapy.  Could char putty draped around the affected limbs help detoxify their systems once the chemo has done its duty? Would magnetized biochar, the new darling for sorbing heavy metals and other toxins, make this work?  Or are the pores clogged with the other substances in the char putty?

Therapy putty is already ‘a thing’.  Its prescribed for those with anxiety.  But perhaps char putty could reduce more than anxiety.  It’s worth considering.  Hears to hoping this not-so crazy idea might inspire a few researchers to put this putty through its paces! 

It is Not the Critic Who Counts

Recently someone claiming to have ‘spent years’ researching biochar wrote a rather lengthy blog/report about his viewpoint on the prospects for biochar as a viable solution for climate change mitigation. I won’t mention the title as it seems to have changed a few times, perhaps in an effort to garner further attention.  Not surprisingly though there has been some interesting conversation within the biochar community about said article. One of the main complaints was that the site that published the article never allowed comments, which seems a little thin-skinned.  That is a tactic that our new President and certain cabinet secretaries have been using, so perhaps it is becoming something of a new norm to discourage dialogue.  To quote a frequent late night twitter abuser – ‘SAD’! 😉

But what is so glaringly obvious to anyone that is actually inside the industry and has actually spent a lot of time on biochar research or at least reading broadly and deeply on the topic, is that the article is so out of date.  If it had been published 2 – 3 years ago, the last time the author seems to have spoken to anyone in the industry, some of what he wrote would have been more relevant.  However in the past few years much has changed in the world of biochar. Not only has the breadth of biochar research expanded in terms of a wide variety of potential new uses and a better understanding of the nuances of biochar production and the best ways to use it in different growing systems, but also the number of companies that are beginning to produce thousands of tons of biochar is increasing every quarter.  Hardly what I would consider a ‘standstill’ for the industry, which is what the author claims

Another odd point is that the author chose to focus almost exclusively on biochar’s ability to sequester carbon for the long term, something for which he claims there is dubious research – without really backing that up with recent peer reviewed citations.  He claims that for the past several years there has been an effort to get biochar included in carbon markets.  By and large that effort ended a few years ago and while it is true that it was unsuccessful, the fact of the matter is that the whole carbon market industry has been something of a disappointment.  Prices per ton of CO2e on the carbon markets have been hovering around $12 in the U.S.  whereas the lowest price per ton of biochar is around $600 (and often much higher).  Needless to say with such a huge disparity, the carbon market side of things doesn’t really get too many folks in the biochar world all that excited these days, at least not in the U.S.  That is not to say they wouldn’t welcome additional income, but this is not something a lot of people are actively working on.  The focus has been on documenting biochar’s value proposition in agriculture, in remediation, in wastewater treatment and other areas.  There is acknowledgement that biochar doesn’t make economic sense everywhere given the current price, but the quest for identifying viable markets has definitely moved beyond carbon markets.

This article also resuscitates an old yarn claiming that the only way for biochar to make a significant impact in rebalancing atmospheric carbon, is if substantial food bearing land is converted into growing biomass for carbonization.  I call a hearty BS on that one. To clarify what I mean by BS, I am talking about not just bull manure, but all human and animal excrement as just one stream of waste that when carbonized, has the potential to significantly reduce current GHG emissions related to large animal and human poop processing AND sequester carbon at the same time.  I’ve blogged about lots of other waste that is currently either being out-right burned (e.g. crop waste, invasives, etc.), or landfilled (e.g. food waste, green waste, etc.) or otherwise underappreciated that can take us a long, long way before ever entertaining the needless notion to convert land used for crops into land used for biomass.

Then there are claims that ‘in many instances’ the biochar industry has teamed up with the Oil & Gas industry looking for ways to mitigate their emissions or remediate the harm they have done to eco-systems. Many compared to what? I have seen or heard of very little financial investment from the fossil fuel folks (FFF) outside of funding some academic research. Of course the FFF are beginning to hedge their bets into renewables and other climate friendly technologies, so it would be naïve to claim they have invested nothing, but I would love to hear more facts instead of unsubstantiated innuendo.  This type of hack job reporting is what has made Fox News famous. 

It is disappointing to see biased articles like this that purport to have spent so much time on an issue, when it is clear the goal was headlines and not balanced reporting. Balance requires following all the threads, not just the titillating ones.  Those of us ‘in the arena’ as Teddy Roosevelt so famously said, with our faces marred by dust (perhaps he meant biochar?), are hard at work trying to find the bright spots of where and how and for how long biochar can help rebalance carbon while also helping humanity to adapt to the ominous perils of climate change, toxified soils and other environmental calamities.  It is far more productive for all of humanity to build something up, rather than to tear something down.  That doesn’t mean we can’t admit to the flaws and failed attempts to build an industry, but we need to focus on what works and how to replicate it quickly, economically and sustainably if we are to have any chance of making an impact with biochar. 

Join me at the Carbon Farming & Biochar Workshop!

Exciting news!  Legislators in the NYS Assembly recently introduced the ‘Carbon Farming Act’ (A3281) which seeks to reward farmers for practices that maximize carbon sequestration in New York.  The bill acknowledges that ‘soil & vegetation management can significantly enhance soil & carbon sequestration’ while at the same time improving soil health, crop yield and water quality. 

To help educate the public on what this really means and build support for the bill, I am helping to host a one day workshop on May 20th which will provide an overview of carbon farming methods, including a focus on biochar of course!  The workshop will review the proposed legislation and its potential impact on farmers and will include sessions led by students and faculty from Cornell University and Finger Lakes Biochar on carbon farming and biochar.  You will leave the event knowing how to make biochar, different kinds of equipment available to make it and a few ways to use it at home or on your farm.

I’ve rattled the cages of other biochar experts in the region and am happy to say that many of them will be on hand to provide demonstrations on how to make biochar and talk about using biochar in different ways.   Joining me will be folks from America Sequesters, Biomass Controls, Green Light Plants, Acorn Biochar, RIT’s Golisano Institute for Sustainability and more! 

Many thanks to our host, the Boathouse Beer Garden (6128 State Route 89, Romulus, NY 14541), a lovely spot off the West side of Cayuga Lake.  The good folks from the Ithaca chapter of the Citizens Climate Lobby have been helping to get the policy folks to the event as well. The event will kick off at 10am and run until 4pm on Saturday May 20th.  Lunch and a local beverage (e.g. beer, wine or non-alcoholic) are included and a portion of the proceeds will be used to purchase organic produce from local farmers for the local Food Pantry.  Free biochar samples will be available to those interested in collaborating on small scale biochar trials.

If you’d like to join the fun, register now here or contact me if you would like to help sponsor or provide a demonstration at the event.

One big benefit of adding biochar to livestock feed: healthier milk

While doing some research recently a collaborator asked if biochar fed to dairy cows impacts the quality of milk.  Given that the purpose of adding biochar to livestock feed is to bind toxins and other nasties, it seemed logical but as I sought an answer to the question, the research on this particular question seemed scarce.  However I did find a few tantalizing bits of research which showed how much healthier goat and dairy milk was when goats and cows were fed charcoal.  But before I get to the good news, let me tell you about a not so fun guy (or fungi) that can often be found lurking in different animal products.

Aflatoxins: not a word that is commonly bandied about outside of academia, but aflatoxins can have a major impact on crops and critters, including us!  Aflatoxins are naturally occurring products brought to us by fungi.  They can be generated in soils or silos when too much water is left on crops. They are most commonly found on corn and cottonseed, but may also be found on soybean and distillers grain.  When eaten by livestock a certain amount of it can carry over into eggs, milk and meat.  When consumed by humans, high or long term exposure can lead to all sorts of health issues from convulsions to cancer.  In the US alone, the economic impact of aflatoxins on the dairy industry is estimated to exceed $200M per year!

And now to the good news. The goat research out of India showed that supplementing charcoal in the daily diet of dairy goats (1% DM), significantly reduced the amount of aflatoxins that showed up in their milk without any reduction in milk quantity or nutrient quality – with the exception of Zinc which increased. The two charts in the above graphic show just how much aflatoxin levels can be reduced (T1 is control; T2 is sodium bentonite and T3 is charcoal). The control milk had nearly five times as much aflatoxin as compared to the milk from the char chomping goats! The dairy research done in Italy showed that certain types of activated charcoal could reduce aflatoxin carry over in milk by up to 50%, an improvement of other common binders which topped out at 36%.

Unfortunately in the U.S. the use of plant derived charcoal is not currently permitted as a feed additive for livestock that are expected to enter the human food chain (i.e. its ok for cats but not cows!). In 2012 the Association of Animal Feed Control removed charcoal from their approved list of feed additives citing concerns of possible chemical or heavy metal contamination.  Thankfully researchers and biochar producers are working closely with the Food & Drug Administration to demonstrate that feeding biochar to livestock is not only safe, but highly beneficial.   Researchers and producers in Germany have also been working with regulators quite successfully to demonstrate the multiple health and economic benefits of feeding char to hogs, hens and Holsteins!


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.