Adding clay and iron sulphate to biochar

Apparently, it makes a tremendous difference in the formation of the pores, the ability to store and release phosphorus, and in the retention of microbes near the biochar if you add them to the feedstock before burning. I found a soil amendments/farming store near me who sells it for $40 for 60 pounds.

Iron Sulphate Biochar treatment

Its really simple. Dissolve ferrous sulphate in boiling water  let it cool and then using a simple spray applicator spray onto the surface of the biomass or a mineral clay if the biomass has a waxy coating and then  pyrolyse.  I have used this technique in rural areas of developing countries.  Dont need a University just need access to iron sukphate.


Yes nealy all our biochars are pretreated with iron sulphate

We have published many papers now on the role of iron sulphate in enhancing the properties of biochar.  Page one of google scholar

Regards
Stephen

Here is the first abstract, but there are many:

Abstract
Abstract Image

Dramatic changes in molecular structure, degradation pathway, and porosity of biochar are observed at pyrolysis temperatures ranging from 250 to 550 °C when bamboo biomass is pretreated by iron-sulfate-clay slurries (iron–clay biochar), as compared to untreated bamboo biochar. Electron microscopy analysis of the biochar reveals the infusion of mineral species into the pores of the biochar and the formation of mineral nanostructures. Quantitative 13C nuclear magnetic resonance (NMR) spectroscopy shows that the presence of the iron clay prevents degradation of the cellulosic fraction at pyrolysis temperatures of 250 °C, whereas at higher temperatures (350–550 °C), the clay promotes biomass degradation, resulting in an increase in both the concentrations of condensed aromatic, acidic, and phenolic carbon species. The porosity of the biochar, as measured by NMR cryoporosimetry, is altered by the iron–clay pretreatment. In the presence of the clay, at lower pyrolysis temperatures, the biochar develops a higher pore volume, while at higher temperature, the presence of clay causes a reduction in the biochar pore volume. The most dramatic reduction in pore volume is observed in the kaolinite-infiltrated biochar at 550 °C, which is attributed to the blocking of the mesopores (2–50 nm pore) by the nonporous metakaolinite formed from kaolinite.

(It might be easier to see if you run your own search on google scholar-JS)

Mineral–biochar composites: molecular structure and porosity
A Rawal, SD Joseph, JM Hook, CH Chia… - … science & technology, 2016 - ACS Publications
… , and porosity of biochar are observed at pyrolysis temperatures ranging from 250 to 550
C when bamboo biomass is pretreated by iron-sulfate-clay slurries (iron–clay biochar), as …
Save Cite Cited by 109 Related articles All 8 versions
The mechanisms and consequences of inorganic reactions during the production of ferrous sulphate enriched bamboo biochars
…, B Gong, J Shepherd, W Buss, S Joseph - Journal of Analytical and …, 2018 - Elsevier
… Recent work has also identified a range of specific improvements in the soil remediation
properties of biochars amended with iron compounds. The work of Waychunas et al. [9] further …
Save Cite Cited by 11 Related articles All 6 versions
[HTML] nature.com
[HTML] Chemolithotrophic processes in the bacterial communities on the surface of mineral-enriched biochars
…, SD Joseph, M Ji, S Nielsen, DRG Mitchell, S Donne… - The ISME …, 2017 - nature.com
… We further show here that the presence of clay minerals and iron sulfate on the biochar
influences the bacterial community composition on the surface by specifically enriching two …
Save Cite Cited by 84 Related articles All 8 versions
Effect of clay and iron sulphate on volatile and water-extractable organic compounds in bamboo biochars
A Reynolds, SD Joseph, TV Verheyen, K Chinu… - Journal of Analytical and …, 2018 - Elsevier
… batch pyrolysis conditions producing different biochar surface and bulk molecular properties…
released from biochar, this work contributes to our understanding of biochar efficacy in soils. …
Save Cite Cited by 4 Related articles All 5 versions
Characteristics of biochar: microchemical properties
JE Amonette, S Joseph - Biochar for environmental management …, 2009 - books.google.com
… biochar as manifested primarily at a microscopic and molecular scale. We start by describing
the biochar-… insoluble sulphide (eg CaS, K2S) in the biochar matrix, or from fixed to reactive …
Save Cite Cited by 609 Related articles All 4 versions
[PDF] wiley.com
How biochar works, and when it doesn't: A review of mechanisms controlling soil and plant responses to biochar
S Joseph, AL Cowie, L Van Zwieten, N Bolan… - GCB …, 2021 - Wiley Online Library
… When biochar is applied in the form of BCF that combines biochar, minerals and N and P
compounds (eg urea, ammonium sulphate, diammonium phosphate), the physical and …
Save Cite Cited by 16 Related articles All 12 versions
Biochar and enhanced phosphate capture: Mapping mechanisms to functional properties
JG Shepherd, S Joseph, SP Sohi, KV Heal - Chemosphere, 2017 - Elsevier
… capture in biochar and thereby inform its future optimisation as a sustainable P fertiliser. The
biochar … (3) Dissolution of sulfate minerals (as observed in the biochars produced at 450 C). …
Save Cite Cited by 57 Related articles All 12 versions
[HTML] sciencedirect.com
[HTML] Phosphorus adsorption onto an enriched biochar substrate in constructed wetlands treating wastewater
L Bolton, S Joseph, M Greenway, S Donne… - Ecological …, 2019 - Elsevier
… biochar surface was associated with aluminium, silica, iron, magnesium and calcium-rich
mineral phases. This study showed that an enriched biochar … present as iron sulfate (FeSO 4 ·…
Save Cite Cited by 41 Related articles All 3 versions
[PDF] researchgate.net
Effects of enriched biochars containing magnetic iron nanoparticles on mycorrhizal colonisation, plant growth, nutrient uptake and soil quality improvement
S Joseph, HM Anawar, P Storer, P Blackwell, C Chee… - Pedosphere, 2015 - Elsevier
… This suggests that biochar addition increases the niche space for soil microorganisms.
Field trials indicate that biochar application can lead to a plant and crop yield increase (Chan …
Save Cite Cited by 73 Related articles All 13 versions
[HTML] sciencedirect.com
[HTML] Effects of iron-modified biochar with S-rich and Si-rich feedstocks on Cd immobilization in the soil-rice system

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Biochar is a rabbit hole.  The more I learn about it, the more fascinating it is to me.  Thanks for posting that.

Very interesting, John. I came across one of these papers recently and skimmed it (really busy at the time). I'm thinking of trying it but without the clay, because my flame cap process runs hot (650-750 C) and Stephen says that at higher temperatures the kaolinite formation blocks up the micropores.

When I get to the stage where I can make this in a reactor with temperature control ability, the possibility of all sorts of pre treatments gets better.

Excellent point, Phil. I was breezing through them as well, and I didn't focus on the temperature and effect on the clay.  I'll also have to hold off on the clay until I can get an accurate temperature for my biochar set up.

John S
PDX OR

I have been delving further into how to trick out your biochar prior to pyrolysis. Apparently, it can greatly improve nutrient cycling.  I realize that the practice of adding bones to the biochar prior to burning, which I have been doing, makes sense with this further research. This article is very dense. I may try adding ag lime before, as it's so cheap.  I also think I'm going to add ferrous sulphate, which is also pretty cheap and they are both cited in this article.  I found it in Google Scholar under Mineral enhanced biochar, soil fertility.

John S
PDX OR

https://www.nature.com/articles/s43247-022-00394-w

Update: I bought some ferrous sulphate.  It was from China and expired.  It gave a web address to look into possible contamination.  The url said Great product! Contamination free! We are outstanding company with good people!    I returned it.  I emailed the guy who's been doing it a lot with ferrous sulphate and he said that he gets it from Australia.  The guy at the store said almost all of the packages are from China.   If the website had actual data, I would have reconsidered it.  

I'm going to wait until I can find better ferrous sulphate.  It seems as if it would be nearly impossible to remove the contamination once you put it into your soil.   I'm going to try with ag lime and oyster shells for right now until I can see a better option.

John S
PDX OR

If you are up for making your own…

https://labmonk.com/preparation-of-ferrous-sulphate

I don't think my skills are up to that yet, but it's great info for someone who is ready.
John S
PDX OR

I wonder if you could get something similar by soaking steel wool (or other form of iron) with epsom salts and water for a week?

I love these blue-collar shade tree mechanic solutions!

John S
PDX OR