Hugh McLaughlin - Biochar Workshop

Unique Biochar Phenomena

Hugh McLaughlin, PhD, PE

www.acfox.com

November 23, 2014 @ Tufts

Despite their artistic pretensions,

sophistication, and many

accomplishments, humans owe

their existence to a six-inch layer

of topsoil and the fact that it rains.

– anonymous

Theories for Ancient Practices

• Prior to steel axes, fire was the main tool for

modifying the landscape and clearing land

• Staple crops tend toward starches, which

require significant potassium and phosphates –

which have to be added for sustained field

productivity (and this field was a lot of work)

• Field preparation by transporting water

vegetation, like palm leaves, then “cool

burning” to release fertilizers into soil

This is the tree as it grows.

About one half of the carbon

dioxide uptake results in

additional carbon atoms in

biomass

This is when biomass dies

and becomes detritus: such

as leaves and tree death

This is due to microbial

breakdown of dead biomass –

95% in one to twenty years

200 CO2

200 C

<100CO2>

100C

Fate of Reduced “Fixed” Carbon

- After the plant takes care of

energy requirements of procuring a

balanced diet, the excess carbon is

directed to seeds, biomass growth or

stored as sugars for the next season.

- Sugars are excreted into the soil

biota in exchange for plant nutrients

(NPK and micro-nutrients).

- If NPK are available, the plant

does not “waste” sugars on soil.

microbes and puts that carbon into

plant priorities = more plant growth

- Without plant sugars, soil microbes

attack each other and soil carbon

decreases, leading to sterile soil.

Pyrolysis and Carbonization

convert biomass into biochar:

one half of the carbon atoms

are released as volatiles and

one half converted to biochar

The volatiles contain carbon

atoms that the tree removed

from the atmosphere as it

grew = carbon neutral

A minority of biochar is

slowly oxidized by soil

microbes; the majority

is stable for hundreds

to thousands of years40C remains in

stable in the soil

200 CO2

50C

<50CO2>

<10CO2>

Climate

Civil

Disobedience

Carbon

Time-out

Biochar: “invented” 600 million years ago by Mother Nature

From: http://www.techtp.com/Torrefaction for High Quality Wood Pellets.pdf, page 7 of 36

Figure 2: Wood Physical Structure – from tree to molecules of lignin & sugars

From: http://www.techtp.com/Torrefaction for High Quality Wood Pellets.pdf, page 7 of 36

Figure 2: Wood Microscopic Structure – molecular mixtures at the atomic scale

D

drying (A)

Extensive

Devolatilisation

and

carbonisation

(E)

Limited

devolatilisation

and

carbonisation (D)

depolymerisation

and

recondensation

(C)

A

E

D

C

E

A

D

C

glass transition/

softening (B)

Hemicellulose Lignin Cellulose

100

150

200

250

300

Temp

eratu

re (°

C)

Hemicellulose Lignin Cellulose

100

150

200

250

300

Temp

eratu

re (°

C)TORR

EFAC

TION

Pyrolysis & Carbonization Reactions of Wood@300C: Below = Torrefied Wood Above = charcoal & biochar

Hardwood Pellets: Dried, Carbonized 200C to 300C

From page

Amorphous Graphite = Domains of Graphene

8

Figure 3: Development of local Graphene domains during carbonization

of J. Phys.: Condensed Matter 19 (2007)

9

Figure 4: Development of porous 3-dimension structure during carbonization

Figure 1: Yield and Adsorption Capacity of Lab Chars

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

200 300 400 500 600 700 800 900

Heat treatment temperature Celsius

Ch

ar

yie

ld a

s w

t %

of

dry

bio

mass

0%

1%

2%

3%

4%

5%

6%

7%

8%

9%

10%

Ad

so

rpti

on

cap

acit

y a

s w

t %

R134a a

t 100C

Yield

Ads @ 100C

Pivotal Biochar properties:

Short-term Effects are due primarily to• Ash Content – due to pH impact

• Mobile Matter – due to stimulating parasitic soil

microbes, which compete for nitrogen, but

sometimes any microbes are better than none

Long-term Effects are attributed to only the• Resident Matter – because it

• Adds Volume with high porosity to the soil

• Increases Cation Exchange Capacity

• Introduces significant Adsorption Capacity

How does Biochar work in the Soil?

• Biochar works in conjunction with the

existing soil, crop and climate.

• Biochar helps “soil” go back to being soil.

• Improved Moisture Dynamics – high & low

• Improved Nutrient Retention (N, P, K)

• Improved Microbe survival during drought

• Improved Plant-Microbe synergisms

This begs the question:

How does Resident Matter accomplish

the following in the Soil?





- and why does it depend on Biochar

Porosity, CEC and Adsorption?




Two different moisture regimes,

with three different mechanisms:

– High moisture in tight soils (flooding in clays)

– High moisture in loose soils (flooding in sand)

– Low moisture in all soils

• desiccating or drought conditions

- Also Bulk Density or the box of corn flakes

- this is the density of the individual corn flakes

-this is the density of the corn flake “molecules”

or the corn flake skeleton without vapor volume

- applies to all micro-porous media including chars

Calculating the “density, porosity, voidage”

of a typical biochar (a good one…)

• Apparent Density = 250 kg/cubic meter

• Skeletal Density = 1500 kg/ cubic meter

– Skeleton = 250/1500 = 1/6 cubic meter

– Total voidage = 1 – 1/6 = 5/6 cubic meter

• Assuming 1/3 inter-particle voids

– Space between particles = 1/3 cubic meter

– Space inside particles = 5/6 – 1/3 = 1/2 m3

Summary: Biochar is 83% voidage and

17% graphitic skeleton

• 33% of the volume is between particles –

this improves soil drainage and aeration

• 50% of the volume is inside particles – this

volume is available to store bulk water

This available volume improves overall soil

properties during excess moisture

– but what about desiccating soil conditions?

That requires ADsorption of the moisture

Mechanis

m

Linear

isotherms

Non linear

isotherms




This is the CEC = Cation Exchange Capacity property

Biochar has both Cation and Anion Exchange capacity

- Exchange Capacity is due to non-graphitic organic

side chains, oxidized to organic acid functionalities

and organic bases due to bound nitrogen molecules

- Adsorption of Humic Acids also increases EC





Microbes need two things to survive: food and water

- Biochar adsorbs water and water soluble

organics via isotherms – and desorbs them when

background levels are below “equilibrium”

Freshly made Biochar is like raw Ground Beef;

is it food? – not yet

Steps to preparing biochar for optimal soil benefit: C-C-I

- Conditioning: equilibrate with soil moisture properties

- pH effects, total dissolved solids (salts), liming

- desorb soluble sugars and other mobile matter

- Charging: equilibrate with soil fertilizer levels

- in balance with annual fertilizer fluxes

- Inoculating: Biasing the Soil Microbial Populations

- this may not be necessary or even work

All of which happens during composting or given enough time

Make Biochar,

and save your world

Options for obtaining Biochar

• You can buy it – but from who?

– Some charcoals are good biochars, some are

BAD – and all need to be tested

• You can make it

– For “gardening”, TLUDs work best

– The other approach is “Retort” processes

– Equipment is coming to the market – slowly

• Example: Adam Retort – about 350 kg/batch

How does wood burn?

• Wood, consists of hemicellulose, cellulose and lignin

– Hemicellulose gasifies at 250 – 300C

– Cellulose splits into char and volatiles between 300C and 450C

– Lignin splits into char and volatiles between 300C and 750C

– Volatilization cools the remaining solid, but the gases burn and generate radiant heat (yellow to blue light)

– Eventually, oxygen can react with the remaining char to make CO2, H2O and ash, plus more heat (red light)

– Putting it all together, we have:

Figure 1: Yield and Adsorption Capacity of Lab Chars

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

200 300 400 500 600 700 800 900

Heat treatment temperature Celsius

Ch

ar

yie

ld a

s w

t %

of

dry

bio

mass

0%

1%

2%

3%

4%

5%

6%

7%

8%

9%

10%

Ad

so

rpti

on

cap

acit

y a

s w

t %

R134a a

t 100C

Yield

Ads @ 100C

H-1. Charcoal burners were a strange breed, living alonely life in the forest, like wild beasts… At its best,making charcoal was not for any normal human. Thetime required for charring a small mound varied fromone to two weeks, but with mounds 30 feet or moreround, a month was average. During all that time,through every kind of weather, the charcoal maker livedwith his mound, sleeping only in dozes for fear a flamemight start and explode into a full fire which woulddemolish the mound. There was no time for washing;there was seldom more shelter than a bark lean-to.

Any Volunteers for running a Earth mound Kiln?

Earth Kiln – Ohio - 1942

Tropical Products Institute

- Mark V

Tropical Products Institute

- Mark V – IN ACTION

Figure 4: Completed TLUD

Google: 1G Toucan

Figure 7: Half way through burn

Figure 10: 1G Toucan Biochar

Larger than TLUDs, appropriate for

home gardeners and consuming small

amounts of scrap wood or “forestry

slash” are:

• Two Barrel Retorts

• Double Barrel Twin Keg Retorts

• Jack Daniel’s Rickyard Technology

Google:

Jolly

Roger

Ovens or

JRO Biochar

Commercial operations require larger

equipment and regulatory approval:

• Adam-style Retorts

• This is a developmental “Chicken or

the Egg” – Nobody makes them

because nobody wanted them

The Mobile Adam Retort c/o New England Biochar

http://flowfarm.org/biochar.html

Make Biochar,

and save your world

Unique Biochar Phenomena

Hugh McLaughlin, PhD, PE

www.acfox.com

November 23, 2014 @ Tufts

Hugh McLaughlin - Biochar Workshop

Environment

Transcript of Hugh McLaughlin - Biochar Workshop