BIOCHAR AND ORGANIC WASTES

G. Gascó (1), A.M. Tarquis(2), A. Méndez (3)

(1) Edafología. E.T.S.I. Agrónomos. Email: gabriel.gasco@upm.es

(2) Matemáticas. ETSI Agrónomos

(3) Ingeniería de Materiales. ETSI Minas.

International Conference “Protection of soil functions – challenges for the future”

Definition of biochar

-Biochar is a carbon-rich solid obtained by the thermal decomposition of organic matter

under a limited supply of oxygen and at relatively low temperatures (Lehmann and

Joseph, 2009)

- Biochar is defined as char produced by pyrolysis for use in agriculture in an

environmentally sustainable manner.

Raw materials

Pyrolysis: Thernal process

Without O2 (<2% )

300-700ºC

Biochar

Sewage sludge treated at

400ºC

Lehmann, J., Joseph, S., 2009. Biochar For Environmental Management. Earthscan, London.

Feedstock (Schmidt et al., 2012): Guidelines from biochar production

Schmidt H.P., Abiven S., Kammann C., Glaser B., Bucheli T., Leifeld J. 2012. Guidelines from biochar production. Delinat

Institute und Biochar Science Network, Switzerland

- Biodegradable waste with waste separation: biodegradable waste with kitchen waste

and leftovers

- Garden waste: leaves, flowers, roots, pruning from trees, vines and bushes, clippings

from nature conservation measures, hay, grass

- Agriculture and forestry: bark, bark and chippings, sawdust, wood shavings, wood wool

-Vegetable production : material from washing, cleaning, peeling, centrifuging and

separation processes. Pulp, pips, peelings, shreds or pomace (from oil mills, spent grain)

-Waterway maintenance : flotsam, fishing residues

-Kitchens and canteens : Kitchen, canteen and restaurant leftovers

-Animal by-products: bones, hides , skins

-Materials from food production and confectionary production: oilseed residues,

mushroom substrates, fish residues

-Textiles: cotton, cellulose

-Paper production: paper fibre sludge

-Biogas plants: fermentation residues

Pyrolysis conditions

Temperature

- Carbon content increases with temperature (Okimori et al., 2003): 56 % (300ºC)

to 93% (800º)

- Biochar surface area (Day et al., 2005): 120 (400 ºC) to 460 m2 g-1 (900 ºC)

- Surface area, pH and total surface charge (Ippolito et al., 2012): Switchgrass.

Increase from 250 to 500 ºC.

Day, D., Evans, R.J., Lee, J.W., Reicosky, D., 2005. Energy 30, 2558–2579..

Ippolito, J.A., Novak, J.M., Busscher, W.J., Ahmedna, M, Rehrah, D., Watts, D.W., 2011. J. Environ. Qual. 41, 1123-1130.

Okimori, Y., Ogawa, M., Takahashi, F., 2003. Mitigat. Adaptat. Strateg. Mitig. Adapt. Strateg. Glob. Chang. 8, 261-280.

Pyrolysis conditions

Temperature

- H/C ratio, cation exchange capacity (Kloss et al., 2012): Straw and woodchips.

Decrease from 400 to 525ºC.

- Low temperatures: controlling the release of nutrients in soils, hydrophobic

properties and limit the capacity for soil water storage.

Song, W., Guo, M., 2012.. J. Anal. Appl. Pyrol. 94, 138-145..

Kloss S., Zehetner, F., Dellantonio, A., Hamid, R., Ottner, F., Liedtke, V., Schwanninger, M., Gerzabek, M.H., Soja, G.,

2012. J. Environ. Qual. 41, 990-1000..

Optimal temperature treatment for soil amendment

(Song and Guo, 2012)

300-600 ºC

Influence of temperature on biochar properties (Méndez et al., 2013)

Sewage sludge CAP-400ºC CAP-600ºC

pH (1:2.5) 6.33 7.76 8.72

EC (1:2.5 (dS m-1, ) 3.6 3.04 1.46

TOM (%) 20.10 17.49 11.95

SOM(%) 0.15 ip ip

CEC (cmol(+) kg-1) 45.23 29.90 11.67

BET Surface Area (m2/g) 6.81 33.44 37.18

Cu (mg kg-1) 545 632 740

Ni (mg kg-1) 102 129 134

Cd (mg kg-1) 7.54 9.67 9.76

Zn (mg kg-1) 2398 2983 3922

Pb (mg kg-1) 189 239 253

A. Méndez, M. Terradillos, G. Gascó .2013. Physicochemical and agronomical properties of biochar from sewage sludge at

different temperatures. Journal of Analytical and Applied Pyrolysis 102: 124-130

SL 400ºC 600ºC

Proximate analysis of SL, CAP-400 and CAP-600 (by thermal analysis)

A. Méndez, M. Terradillos, G. Gascó .2013. Physicochemical and agronomical proeprties of biochar from sewage sludge at

different temperatures. Journal of Analytical and Applied Pyrolysis 102: 124-130

Sample VM (%) FC (%) Ash (%) FC/(FC+VM)

SL 35.89 6.99 57.12 16.30

CAP-400 23.34 4.64 72.02 16.58

CAP-600 16.70 4.77 78.53 22.23

VM: Volatile matter, FC: Fixed carbon

-1,0

-0,5

0,0

0,5

1,0

1,5

0 100 200 300 400 500 600 700 800 900

Temperature (ºC)

DT

A (

uV

/mg)

SL

CAP-400

CAP-600

exo DTA curves

-The exothermic band is more intense in

the original feedstock (SL) due to their

higher organic matter content

- Pyrolysis reduces organic matter content

- Temperature at which combustion starts

and finishes moves to higher temperatures

from SL to CAP-400 and CAP-600. These

results indicate that as the pyrolysis

temperature increases, the biochar

obtained was thermally more stable.

- This fact is according to the reduction of

VM(%) during pyrolysis.

Sewage sludge

CAP-400ºC CAP-600ºC

Fibers from pruning waste added in the sewage sludge composting process can be

observed in images from raw samples. Some fibers are still in the biochar pyrolyzed at

400ºC but completely disappear at 600ºC.

Optical micrographs of sewage sludge and biochar samples

Influence on soil properties

1. The soil emissions of CO2 and greenhouse gases for long term.

2. Physical, chemical and biological soil properties.

Formulation of growing media

3. Hydrophysical characteristics of the substrates

Soil and water remediation

4. Soil contaminated by Ni

5. Water contaminated by metals and organic compounds

Soil CO2 emissions: biochar and carbon sequestration (Méndez et al., 2013)

“Biochar contribute to carbon sequestration due to carbon stability of biochar materials”

A. Méndez, A.M. Tarquis, A. Saa-Requejo, F. Guerrero, G. Gascó.

2013. Influence of pyrolysis temperature on composted sewage

sludge biochar priming effect in a loamy soil. Chemosphere 93:

668-676

Treatments

Selected soil (T) was amended with sewage

SL and biochars (CAP-400 and CAP-600) at

8%wt

CO2 evolved was evaluated during 80 days at

a temperature of 28 ºC

101a

139d

123c

95a

0

20

40

60

80

100

120

140

0 20 40 60 80C

um

ula

tive

CO

2 e

volv

ed

(m

g C

-CO

2/

10

0 g

)

Time (Days)

T

SL

B400

B600

The application of biochar prepared from

sewage sludge reduced the CO2 evolution by

11 and 32% with respect to sewage sludge

treatment after the incubation experiment

Soil CO2 emissions: biochar and carbon sequestration

Double first-order kinetic model (Jenkinson, 1977)

)1()1( 21

2121

tktkeCeCYYY

Y1 is the cumulative evolved C–CO2 (mg CO2/100 g of soil)

from labile C and Y2 is the cumulative evolved C–CO2 (mg

CO2/100 g of soil) from relatively recalcitrant mineralizable C.

Young Carbon

(C1)

Old Carbon (C2)

CO2

r K1 C1

r K2 C2

r= factor summarising external influence. In our case r=1.

i=Carbon input . In our case i=0.

Jenkinson, D.S. 1977. Studies on the decomposition of plant material in soil. J. Soil Sci. 28, 424-434.

Reduction of CO2 emissions

between 301 and 932 kg CO2 ha-1

with respect to the direct application

of raw sewage sludge after 10 yr.

Physical and chemical properties

-Field capacity (FC) followed the order C=SL4<B4<SL8<B8 .

- Wilting point (WP) followed the order C<B4<SL4<B8<SL8.

-Available water (AW) increased in the soil treated with biochar according to Beck et al. (2011).

-Biochar did not improve soil aggregation according to Peng et al. (2011).

- SL8 improved soil aggregation .

Treatments

Biochar (B) was prepared by pyrolysis of selected sewage sludge (SL) at 500ºC.

Haplic Cambisol was amended with the sewage sludge (SL) and the biochar (B) at two different

rates in mass: 4 and 8%, leading to SL4, SL8, B4 and B8 treatments.

Soil

sample

FC (%) WP (%) AW (%) Soil aggregates (%)

(> 2 mm)

T 10.65±0.07a 5.05±0.04a 5.60±0.09 b 22.2±3.1ab

SL4 10.85±0.08b 5.48±0.04c 5.37±0.06 b 27.2±2.1bc

SL8 12.68±0.12 c 7.76±0.06e 4.92± 0.15a 29.0±1.9c

B4 12.32±0.12 b 5.25±0.07b 7.07±0.06c 20.4±2.27a

B8 13.83±0.10 d 6.01±0.07d 7.83±0.14d 18.3±1.50a

Soil aggregates (%)

Total organic carbon (TOC), cation exchange capacity (CEC), pH and electrical conductivity

(EC) of control and amended soils after the incubation experiment

Soil sample TOC (%) CEC (cmol(c) kg-1) pH (1:2.5) EC (1:2.5)

(µS cm-1, )

T 0.66±0.05 a 6.76±0.16a 7.84±0.04 b 73±7a

SL4 1.30±0.04 b 7.94±0.28 b 7.80±0.08 b 978±8 c

SL8 2.42±0.05 d 9.97±0.13 c 7.44±0.05a 1124±9 c

B4 1.28±0.07 b 7.11±0.04a 7.83±0.02 b 293±7 b

B8 1.74±0.08 c 7.16±0.06a 8.01±0.02 c 304±6 b

Méndez A, A. Gómez, J. Paz-Ferreiro, G. Gascó. 2012. Effects of sewage sludge biochar on plant metal availability after

application to a Mediterranean soil. Chemosphere 89 (2012) 1354–1359.

-The largest increase in both TOC at the end of the incubation happened when adding SL8 which

resulted in a 3.5 fold increase in TOC to the control soil. The order of TOC at the end of the

incubation was SL8 > B8 > B4 = SL4 > C.

-Biochar increased soil pH by 0.2 units when a high dose (B8) according with the biochar pH

(9.5) while sewage sludge (SL8) decreased pH to 7.44.

-Sewage sludge (1055 µS cm-1) amendment multiplied EC value by 15 in the soil,

Physical and chemical properties

Soil sample TOC (%) CEC (cmol(c) kg-1) pH (1:2.5) EC (1:2.5)

(µS cm-1, )

T 0.66±0.05 a 6.76±0.16a 7.84±0.04 b 73±7a

SL4 1.30±0.04 b 7.94±0.28 b 7.80±0.08 b 978±8 c

SL8 2.42±0.05 d 9.97±0.13 c 7.44±0.05a 1124±9 c

B4 1.28±0.07 b 7.11±0.04a 7.83±0.02 b 293±7 b

B8 1.74±0.08 c 7.16±0.06a 8.01±0.02 c 304±6 b

Total organic carbon (TOC), cation exchange capacity (CEC), pH and electrical

conductivity (EC) of control and amended soils after the incubation experiment

Méndez A, A. Gómez, J. Paz-Ferreiro, G. Gascó. 2012. Effects of sewage sludge biochar on plant metal availability after

application to a Mediterranean soil. Chemosphere 89 (2012) 1354–1359.

- Sewage sludge increased the value of CEC while Biochar did not.

- CEC of biochar is scarce after low pyrolysis temperatures, increasing at higher temperatures

(Lehmann, 2007).

- Our results agreed with other studies reporting biochar to have a minimal CEC when compared

to soil organic matter (Lehmann, 2007; Cheng et al., 2006; Cheng et al, 2008).

- It is admitted that the effect of biochar addition on CEC is dependent on the type of biomass

pyrolyzed (Jha et al., 2010).

Metal content in sewage sludge and biochar: leaching experiment (mg L-1) and after

extraction with CaCl2 or DTPA (mg kg-1) (Méndez et al, 2012)

Méndez A, A. Gómez, J. Paz-Ferreiro, G. Gascó. 2012. Effects of sewage sludge biochar on plant metal availability after

application to a Mediterranean soil. Chemosphere 89 (2012) 1354–1359.

Metal content after leaching experiment (mg L-1)

Sample Cu Ni Zn Cd Pb

L 0.300 0.085 a 0.081 0.004 a 0.071 0.005 a 0.008 0.001 a 0.0022 0.0006 a

B 0.012 0.006 b 0.029 0.015 b 0.034 0.001 b 0.002 0.001 b 0.0013 0.0004 a

Plant-available metals (DTPA) (mg kg-1)

Sample Cu Ni Zn Cd Pb

L 85.18 4.10 a 31.04 1.21 a 90.05 2.13 a 0.503 0.175a 68.60 3.78a

B 43.55 2.47 b 0.63 0.12 b 29.60 1.27 b 0.321 0.112 b 8.82 0.07 b

Mobile forms (CaCl2) (mg kg-1)

Sample Cu Ni Zn Cd Pb

L 34.24 4.31 a 5.45 0.42 a 247.54 7.60a 0.350 0.107a 12.540 0.107a

B 14.8 2.55 b 4.10 0.31b 24.52 2.33b 0.302 0.101a 2.452 0.072b

Mobile and available forms of metals reduced after pyrolysis (Méndez et al, 2005)

The plant bioavailability (DTPA) of Ni, Zn, Cd and Pb were 57%, 30%, 29% and 31% of those

in SL8 (Méndez et al, 2012).

Advantages of sewage sludge pyrolysis

-It removes pathogens

- The risk of metals lixiviation is reduced

Available Metals (DTPA) in soils (mg kg-1)

0,00

1,00

2,00

3,00

4,00

5,00

6,00

7,00

8,00

Cu Ni Zn Cd Pb

T

SL8

B8

Bio

aval

ible

met

al

(mg/k

g)

Biochar and soil enzyme activities

“Use of soil biochemical properties as indicators of soil quality”

Treatments

Umbrisol with a pH of 6.5. Sandy-loam

Biochar from sewage sludge: 650ºC at a rate of 10º

C min-1 and the final temperature was maintained for

2 h

Biochar and sewage sludges were added to soil at a

rate of 4 % and 8 % (w/w) obtaining the following

treatments: B4, B8 for biochar; SL4 and SL8 for

sewage sludge. 60 % of water holding capacity

(WHC). Incubation: 70 days.

Biochar and soil enzyme activities

J. Paz-Ferreiro, G. Gascó, B. Gutierrez, A. Méndez2.. 2012. Soil activities and the geometric mean of enzyme

activities after application of sewage sludge and sewage sludge biochar to soil. Biology and Fertility of Soils

48:511–517.

The geometric mean of enzyme activities (GMea) was used as a soil quality

index

GMea = (DH x Glu x Phos x Aryl )1/4

Where DH, Glu, Phos and Aryl are dehydrogenase, b-glucosidase,

phosphomonoesterase and arylsulphatase activities, respectively

-Individual biochemical properties showed a different response to the treatments

Advantages of sewage sludge pyrolysis

GMea showed an increase in the quality of soils amended with the high biochar dose and a

decrease in those amended with a high sewage sludge dose.

High doses of sewage sludge are harmful for the soil microorganisms

J. Paz-Ferreiro, G. Gascó, B. Gutierrez, A. Méndez2.. 2012. Soil activities and the geometric mean of enzyme

activities after application of sewage sludge and sewage sludge biochar to soil. Biology and Fertility of Soils

48:511–517.

Treatment Dehydrogenase -glucosidase Phosphomonoesterase Arylsulphatase Gmea

Control 0.11±0.02 a 2.64±.0.86 a 2.57±0.54 a 0.19±0.06 a 0.59±0.05 a

SL4 0.12±0.02 a 1.98±0.22 ab 4.39±1.46 bc 0.16±0.06 a 0.61±0.02 ac

SL8 0.10±0.08 a 0.58±0.10 c 5.24±0.21 c 0.19±0.06 a 0.49±0.05 b

B4 0.16±0.08 a 1.71±0.19 b 2.94±0.54 ab 0.23±0.04 a 0.63±0.05 ac

B8 0.29±0.05 b 1.22±0.20 bc 2.67±0.32 a 0.26±0.04 a 0.70±0.03 c

Enzyme activities (units are expressed as mmol product g dry soil-1 h-1)

Germination index (watercress): Zucconi phytotoxicity test

Zucconi phytotoxicity test

-The germination test was carried out on

filter paper in petri dishes.

- 5 mL of aqueous extract (1/10 w/v) from

different treatment (8%), soil, sewage

sludge and biochar (650ºC)

-10 seeds of watercress (Lepidium sativum)

were placed on the filter paper and dishes

placed in the dark at 28 ºC.

-Germination percentages (Ge) with respect

to control (distilled water) and root lengths

(Lm) were determined after 48 hours.

Germination index (IGe)

IGe = %Ge * Lm/Lc,

where %Ge is the percentage of germinated seeds in each

extract with respect to control; Lm is the mean total root

length of the germinated seeds in each extract and Lc is

the mean root length of the control (Zucconi et al., 1985).

The control GI value is considered as 100%.

Soil contaminated by Ni

Methods

-Vertisol was artificially contaminated by Ni2+ at a concentration of 1000 mg Ni kg-1 soil

- Biochar was prepared by pyrolysis of de-inking sewage sludge (HP) at 500ºC (HP-500).

- HP and HP500 were added to polluted soil at a rate of 5% (w/w) and soils were incubated

during during 80 days at a temperature of 28ºC.

Treatment Ni H2O

(mg kg-1)

Ni CaCl2

(mg kg-1)

Ni DTPA (mgkg-1)

S - 1.30a 0.60a

S1000 1.34b 15.46b 64.70c

S1000+HP 1.87b 15.52b 73.40d

S1000+HP500 0.15c 10.85c 43.60e

HP500 addition to the polluted soil reduced the quantity of mobile, leached and bioavailable Ni

Water contaminated by metals and organic compounds

Activated carbon or carbon based adsorbent

Reinoso and Marsh (2000)

Type of

pore

Diámetro

(nm)

Micropore d < 2

Mesopore 2 < d <5

Macroporoe d > 5

Removal of contaminants

-Introduction in the pores

- Superficial charge density

- Precipitation

Malachite green removal from water (mg L-1)

Initial concentration of MG (mg/kg)

MG

Re

mo

va

l (%

)

0

20

40

60

80

100

Removal of malachite green (%)

HP-3

HP-10

CAC

ORGANIC WASTES

Sewage sludges

Deinking sludge and other paper wastes

Prunning waste

Growing media

Organic

amendments

Soils

Pyrolysis

Biochar

Carbon-based

adsorbents

Soil flushing Wastewater

treatment Gabriel Gascó Guerrero

Email: gabriel.gasco@upm.es

Soil Department (Edafología)

Universidad Politécnica de Madrid (Spain)