Effectivity of Activated Biochar from Waste of Rubber Seed

Shells and Epicarp (Hevea brasiliensis) As a Amelioration

Material Towards Pesticide Residues in The Soil

Sumihar Hutapea

1, Ellen Lumisar Panggabean

1, Tumpal HS Siregar

2, Andi Wijaya

2

1. Medan Area University, Agricultural Faculty, Department of Agrotechnology,. Jl. Kolam

No. 1 Medan Estate, Medan 20223, Indonesia.

2. Indonesian Rubber Research Institute (IRRI), Sungei Putih Research Center. Galang-Deli

Serdang, Po Box 1415, Medan 20001, Indonesia.

Abstract

Producing environment-friendly technology is important to improve the quality of corps

land and dairy products through the utilization of biomass waste as amelioration agent

of pesticide residues in agricultural land. It had investigated that pesticide was widely

used on holticultural land in Karo District to prevent crop failure caused by pests.

Generally, farmers used pesticide on chilies, onions or tuberous root groups and it was

also expected to contaminate the products produced by the plant so that it can cause

health problem. This study aimed to determine adsorption capacity in the soil using

activated biochar from epicarp and rubber seed shells (Hevea brasiliensis). This

experiment used two soil samples from Sukanalu and Korpri village, Karo District,

North Sumatera-Indonesia. Each soil sample was equilibrated with varying

concentration of cypermethrin and chlorpyrifos, i.e 3, 6, 9, and 12 ppm. Langmuir and

Freundlich isotherms model were used to explain equilibrium adsorption. The result

showed that from these isotherms it was evaluated that Freundlich isotherm was obeyed

with adsorption capacity of cypermethrin about 1.786 mg/g (R2=0.963) for Sukanalu

and 1.247 mg/g (R2=0.983) for Korpri. Adsorption capacity of chlorpyrifos about 2.529

mg/g (R2= 0.905) for Sukanalu and 5.395 mg/g (R

2=0.929) for Korpri. Generally,

activated biochar applied by soil sample of Korpri had bigger adsorption capacity than

soil sample of Sukanalu. Adsorption mechanism of pesticide residue was integrated by

clay of soil structure, organic material, and pH value.

Keywords : Hevea brasiliensis, activated biochar, cypermethrin, chlorpyrifos,

adsorption capacity

1. INTRODUCTION

As the product of photosynthesis from carbon dioxide and water, biomass is the only

renewable resource available for both energy and chemical feedstock production. Among different utilization method of biomass, this study focus on biochar, which is the solid product

of pyrolysis. At moderately high temperature in an inert atmosphere, pyrolysis thermally

decomposes the carbohydrate structure of biomass into carbonaceous solid residue (biochar),

and condensable and non condensable vapors of various molecular weight compounds.

Biochar is a value added product, which can be used for many purpose (Lee, et al., 2013).

Recently, the application of biochar to soil is drawing greater attention for sustainable

soil quality improvement and carbon sequestration (Lehmann et al., 2006; Woolf et al., 2010;

Sohi, 2012). In the soil, biochar increases the capacity of the soil holding water and nutrients,

reducing the need for fertilizers. Many small and field test reported increases in the plant

growth and crop productivity after mixing biochar with the soil (Jeffery et al., 2011). Biochar

also reduces the emission of other greenhouse gases from the soil, such as N2O and CH4 (Van

Zweiten et al., 2009). More importantly, biochar can directly store the carbon for a

sufficiently long time due to its strong resistance to biological decomposition (Preston and

Schmidt, 2006; Liang et al., 2008).

For global warming prevention, it is important to study the sequestration mechanism

of carbon in soil of farmland where biochar and composts are used. By using biochar

carbonized with biomass materials such as waste wood, bamboo, and agricultural materials in

farmland, carbon storage in the soil for long period is expected. As the soil properties are

improved and soil microorganisms concentration increase with the addition of charcoal to the

soil, the plant growth promotion in the farmland is also expected.

Growth stimulation of the spinach in the farmland used with the charcoal and the

composts was observed. The aggregation of the soil in farmland was developed by using the

biochar and the composts. It was suggested that the soil was aggregated with microorganisms

proliferated on the surface of the aggregate in the soil (Shuji, et al., 2013).

The role agrochemical in modern agriculture is continuously evolving, and their

contribution to crop protection continues to increase. Linking science and policy is a

cornerstone of the work of both the regulatory authorities and industry. Pesticide are widely

used in producing food and feed. Their residues may remain in small amounts in or on

agricultural produce and processed food. To ensure the safety of food, most governments

regulate the maximum level of each permitted pesticide residue (Byung-Youl, 2001).

In principle, all chemicals, including pesticides, which are introduced into the

environment are gradually recycled within and between the bio-, geo-, atmo-, and hydro-

spheric systems. The rate at which pesticides are moved and dissipated is closely related to

the physico-chemical parameters of the chemical itself and surrounding environmental

conditions. The latter factors include application time and dose, land use patterns and target

crops. Factors related to climate and weather include temperature, rainfall, evapo-transpiration

rates and wind velocity. Parameters related to soil are run-off characteristics, organic carbon

content, texture, hydraulic characteristics and pH (Byung-Youl, 2001).

The experiment about effectivity of activated biochar from rubber seed shells and

epicarp wastes (Hevea brasiliensis) as a amelioration material towards pesticide residues in

the soil aimed to determine the adsorption capacity of cypermethrin and chlorpyrifos residue

using the Langmuir and Freundlich isotherm models.

2. MATERIALS AND METHODS

A series of experiments on adsorption of pesticide residues in some soil samples was

carried out in July and August 2016. The soil sample was obtained from Sukanalu and Korpri

village, Karo District, North Sumatra-Indonesia. The series experiments consist of

manufacturing activated biochar and test of adsorption isotherm of pesticide residues in the soil.

2.1. Preparation and manufacturing activated biochar

Rubber seed shell and epicarp wastes were obtained from experimental field of Sungei

Putih, Galang-Deli Serdang. The properties of biochar were studied from rubber seed shells

and epicarp waste. The reactor was made of metal with a diameter of 57 cm and a height of

120 cm for carbonization. After carbonization, biochar was placed inside an electrically-

heated furnace. In each test, 100-400 g of sample was heated from room temperature to 800oC

and maintained for at least two hour to allow sufficient time for complete pyrolysis. A

detailed description of process and analytical methods has been presented elsewhere

(Hutapea, 2015).

2.2. Test and analysis adsorption of pesticide residues in the soil

For laboratory study the inert soil samples were collected from the 0 to 15 cm soil

depth and ground to pass through a 2 mm sieve. These soil samples were stored in plastic

bags at room temperature. The standard methods were used to determine physicochemical

properties of the soil.

Residue pesticides adsorption isotherms were determined according to the procedure of

Muktamar (2015). Fifty gram of soil sample was equilibrated with 20 ml of varying

concentrations of cypermethrin and chlorpyrifos in 0.01 M CaCl2 solution in erlenmeyer. The

concentrations of the solutions were 3, 6, 9, 12 ppm. Then soil sample was incubated for a

week.

Analysis of pesticide residues in soil used the QuEChERS (quick, easy, cheap, rugged,

and safe) method using a single-step buffered acetonitrile (MeCN) extraction and salting out

liquid-liquid partitioning from the water in the sample with MgSO4. Dispersive-solid-phase

extraction (dispersive-SPE) cleanup was done to remove organic acids, excess water, and

other components with a combination of primary secondary amine (PSA) sorbent and MgSO4;

then the extracts were analyzed by mass spectrometry (MS) techniques after a

chromatographic analytical separation (AOAC, 2007).

Calculation of residual concentration using the formula:

2.3. Langmuir isotherm model

This model deals with monolayer and homogeneous adsorption because the adsorbed

layer is one molecule in thickness, with adsorption occurring at fixed sites, which are identical

and equivalent. Linear form of this model is given in Equation (1):

Ce/(x/m) = 1/ab + 1/a Ce…………….. (1)

Where Ce is the equilibrium concentration of pesticides in solution and x/m is the amount of

pesticides residue in soil, a is the monolayer adsorption capacity, and b is Langmuir isotherm

which was not obeyed by adsorption of pesticides residue (cypermethrin and chlorpyrifos).

2.4. Freundlich isotherm model

Freundlich isotherm is related to the non-ideal and reversible adsorption, not limited to

monolayer formation. Therefore is applied to multilayer adsorption, with non-uniform

distribution of adsorption heat and affinities over the heterogeneous surface. Linear form of

this model is given as in Equation (2).

Log (x/m) = log k + 1/n log Ce ……………. (2)

Where k is multilayer adsorption capacity and n is adsorption intensity. The parameters of

both models are shown in Table 2.

3. RESULTS AND DISCUSSION

Table 1 compares the characteristics of biochar in experiment with SNI standards. The

biomass samples exhibit large variations in the proximate analysis, especially in the volatile

matter and fixed carbon. From the carbon content and mass yield, the carbon yield

representing the amount of carbon remaining in the biochar can be calculated. Biochar have

carbon yields of about 61-65% while the rest have values in the range of 65%.

Tabel 1. Characteristics of biochar compared with SNI standards

Parameters

Value

Biochar SNI

standards

Moisture content (%) 3.97 Max. 15

Ash content (%) 3.78 Max. 10

Volatile matter (%) 30.91 Max. 25

Fixed carbon (%) 65.27 Min. 65

Iodium number (mg/g) 875.97 Min. 750

Benzena number (%) 25.94 Min. 25

Sumihar (2015)

The main role of biochar in the soil is the increased retention of nutrients in addition to the

direct supply of nutrients. Therefore, the microscopic surface area is one of the crucial

properties for biochar, which determines the capability of nutrients and water absorption.

3.1. Soil properties

The soil samples were collected from horticultural land and analyzed in order to evaluate the

soil texture and pH value. Table 2 shows the results obtained from these tests. From table 2, it

was noticed that the silt percentage is larger than that in the clay. Organic carbon is relatively

high (4.07 and 4.22%) which reduced the adsorption of pesticides. Sorption of pesticides to

soil generally increases with soil organic matter content (Tiwari and Guha, 2012).

Tabel 2. Physical and chemical soil properties

Parameters Sukanalu Korpri

Texture

sand (%) 62.87 59.05

silt (%) 33.41 33.50

clay (%) 3.72 7.46

pH (H2O) 5.30 5.70

Organic material

C (%) 4.07 4.22

N (%) 0.78 0.82

P-Bray (ppm) 541.00 448.00

Base saturation (%) 29.91 28.96

CEC (meq/100 g) 32.97 32.45

K-exch (meq/100 g) 6.51 5.39

Ca-exch (meq/100 g) 1.57 2.50

Mg-exch (meq/100 g) 1.31 1.63

Na-exch (meq/100 g) 0.18 0.15

The results of the analysis of both physical and chemical properties soil samples in

both groups, namely Sukanalu and Korpri shown in Table 2. The soil samples Sukanalu

contains 62.87% sand, 33.41% silt, and 3.72% clay. The pH value of the water is 5.30 and

relatively acid. Organic matter content C includes high at 4.07%, while the organic matter

content of N is very high, 0.78%. P content is obtained by extracting Bray classified as very

high at 541.00 ppm. While the CEC and base saturation values obtained are respectively

32.97 meq / 100 g (high) and 29.91% (lower). The composition of cation in the soil samples

Sukanalu includes K at 6.51 meq /100 g (very high), Ca at 1.57 meq /100 g (very low), Mg at

1.31 meq /100 g (moderate), and Na of 0.18 meq /100 g (low). The soil samples of Korpri

contain 59.05% of sand, 33.50% of silt and 5.7% of clay. The pH value of the water is 5.70

and the relatively acid. Organic matter content C includes high at 4.22%, while the organic

matter content of N is very high, 0.82%. P content is obtained by extracting Bray classified as

very high at 448.00 ppm. While the CEC and base saturation values obtained are respectively

32.45 meq /100 g (high) and 28.96% (lower). The composition of cation in the soil samples of

Korpri includes K at 5.39 meq /100 g (very high), Ca at 2.50 meq /100 g (low), Mg of 1.63

meq /100 g (moderate), and Na 0.15 meq /100 g (low). In general, both the soil samples have

physical and chemical properties are no different.

3.2. Cypermethrin adsorption isotherms

Tabel 3. The residual values of adsorption by activated biochar on some concentrations of

cypermethrin

Sample

of soil

C0

(ppm)

Ce

(ppm)

Cads

(ppm)

Xm/m

(mg/g) Ce/(X/m) log Ce log Xm

Sukanalu 3 1.39 1.61 0.81 1.7267 0.1430 -0.0942

6 2.08 3.92 1.96 1.0612 0.3181 0.2923

9 3.16 5.84 2.92 1.0822 0.4997 0.4654

12 4.02 7.98 3.99 1.0075 0.6042 0.6010

Korpri 3 1.13 1.87 0.94 1.2086 0.0531 -0.0292

6 1.60 4.40 2.20 0.7273 0.2041 0.3424

9 2.18 6.82 3.41 0.6393 0.3385 0.5328

12 2.63 9.37 4.69 0.5614 0.4200 0.6707

The process of absorption or adsorption by an adsorbent is influenced by many factors

and patterns within specific adsorption isotherm. Factors that influence in the adsorption

process, i.e the type of adsorbent, the type of substance that is absorbed, the surface area of

the adsorbent, the substance concentration and temperature. Because of these factors, each

adsorbent which absorbs a substance one with another substance would not have the same

pattern of the adsorption isotherm (Handayani and Sulistiyono, 2009).

Table 3 shows that the greater the concentration of pesticides was, the greater the mass

of pesticide was adsorbed by biochar. In concentration of 3 ppm of cypermethrin, pesticide

was adsorbed by biochar about 0.81 mg/gram for Sukanalu and 0.94 mg/gram for Korpri. In

concentration of 6 ppm, pesticide was adsorbed by biochar about 1.96 mg/gram for Sukanalu

and 2.20 mg/gram for Korpri. In concentration of 9 ppm, pesticide was adsorbed by biochar

about 2.92 mg/gram for Sukanalu and 3.41 mg/gram for Korpri. In concentration of 12 ppm,

pesticide was adsorbed by biochar about 3.99 mg/gram for Sukanalu and 4.69 mg/gram for

Korpri. Generally, the absorption of pesticide residues in soil samples of Korpri was larger

than the soil samples of Sukanalu. This condition occured because the soil samples of Korpri

have a clay structure that was larger than the soil samples of Sukanalu, so that the absorption

of pesticide residues was also influenced by the structure of clay in the soil (Tu, 2001).

Figure 1. Langmuir plot for the Cypermethrin adsorption onto biochar

Figure 2. Freundlich plot for the Cypermethrin adsorption onto biochar

Table 4. Equilibrium adsorption isotherm values for cypermethrin pesticide

Soil samples Isotherm Isotherm

parameters Value

Sukanalu Langmuir

a (mg/g) 4.464

b 0.224

R2 0.590

Korpri Langmuir

a (mg/g) 2.525

b 0.396

R2 0.801

Sukanalu Freundlich

k (mg/g) 1.786

n 0.688

R2 0.963

Korpri Freundlich

k (mg/g) 1.247

n 0.534

R2 0.983

The Langmuir adsorption isotherms showed that it is not linear relationship on the

present results shown in Figs. 1, but the Freundlich adsorption isotherms showed linear

y = -0.224x + 1.817R² = 0.59

y = -0.396x + 1.531R² = 0.801

0.0

0.5

1.0

1.5

2.0

0.0 1.0 2.0 3.0 4.0 5.0

Ce/

(Xm

/m)

Ce

Sukanalu

Korpri

y = 1.454x - 0.252R² = 0.963

y = 1.873x - 0.096R² = 0.983

-0.20

0.00

0.20

0.40

0.60

0.80

0.00 0.20 0.40 0.60 0.80

Log

Ce/

Xm

Log Ce

Sukanalu

Korpri

relationship present results shown in Figs. 2. R2 of the Freundlich adsorption isotherms is

larger than that in Langmuir adsorption isotherms and close to 1. It means that this Freundlich

model was obeyed by adsorption of cypermethrin as shown in Figs. 2.

Adsorption tends to have n between 1 and 10. Larger value of n implies stronger

interaction between the soil and the pesticides (Öztürk and Bektas, 2004). The n values were

0.688 and 0.534 for Sukanalu and Korpri respectively in Freundlich isotherm model, showing

that adsorption process was unfavorable and this has to do with low percentage of the clay

(3.72 and 7.46) and due to the organics material available in the horticultural soil. The

multilayey capacity factor of both pesticides (k) is higher than one which shows the good

interaction between the soil and the pesticides with more interaction in Sukanalu than Korpri.

The Langmuir adsorption isotherm is commonly applied to monolayer chemisorptions of

gases. This isotherm is mainly applied when no strong adsorption is expected and when the

adsorption surface is uniform. The Langmuir isotherm shows that adsorption will increase

with increasing pesticides concentration up to a saturation point, in which all of the sites are

occupied (Fig. 1) (Jodeh, et.al., 2013).

3.3. Chlorpyrifos adsorption isotherms

Tabel 5. The residual values of adsorption by activated biochar on some concentrations of

chlorpyrifos

Sample

of soil

C0

(ppm)

Ce

(ppm)

Cads

(ppm)

Xm/m

(mg/g) Ce/(Xm/m) log Ce log Xm

Sukanalu 3 1.82 1.18 0.59 3.0847 0.2601 -0.2291

6 3.06 2.94 1.47 2.0816 0.4857 0.1673

9 5.30 3.70 1.85 2.8649 0.7243 0.2671

12 7.30 4.70 2.35 3.1064 0.8633 0.3710

Korpri 3 2.03 0.97 0.49 4.1856 0.3075 -0.3143

6 3.43 2.57 1.29 2.6693 0.5353 0.1089

9 4.37 4.63 2.32 1.8877 0.6405 0.3645

12 6.57 5.43 2.72 2.4199 0.8176 0.4337

Table 3 shows that the greater the concentration of pesticides was, the greater the mass

of pesticide was adsorbed by biochar. In concentration of 3 ppm of chlorpyrifos, pesticide was

adsorbed by biochar about 0.59 mg/gram for Sukanalu and 0.49 mg/gram for Korpri. In

concentration of 6 ppm, pesticide was adsorbed by biochar about 1.47 mg/gram for Sukanalu

and 1.29 mg/gram for Korpri. In concentration of 9 ppm, pesticide was adsorbed by biochar

about 1.85 mg/gram for Sukanalu and 2.32 mg/gram for Korpri. In concentration of 12 ppm,

pesticide was adsorbed by biochar about 2.35 mg/gram for Sukanalu and 2.72 mg/gram for

Korpri. Generally, the absorption of chlorpyrifos residues in soil was smaller than the

adsorption of cypermethrin.

Figure 3. Langmuir plot for the chlorpyrifos adsorption onto biochar

Figure 4. Freundlich plot for the chlorpyrifos adsorption onto biochar

Tabel 6. Equilibrium adsorption isotherm values for chlorpyrifos pesticide

Soil samples Isotherm Isotherm

parameters Value

Sukanalu Langmuir

a (mg/g) 15.15

b 0.066

R2 0.112

Korpri Langmuir

a (mg/g) 2.755

b 0.363

R2 0.494

Sukanalu Freundlich

k (mg/g) 2.529

n 1.066

R2 0.905

Korpri Freundlich

k (mg/g) 5.395

n 0.653

R2 0.929

y = 0.066x + 2.494R² = 0.112

y = -0.363x + 4.281R² = 0.494

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

0.00 2.00 4.00 6.00 8.00

Ce/

(Xm

/m)

Ce

Sukanalu

Korpri

y = 0.938x - 0.403R² = 0.905

y = 1.531x - 0.732R² = 0.929

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.0 0.2 0.4 0.6 0.8 1.0

Log

Xm

/m

Log Ce

Sukanalu

Korpri

The Langmuir adsorption isotherms showed that it is not linear relationship on the

present results shown in Figs. 3, but the Freundlich adsorption isotherms showed linear

relationship present results shown in Figs. 4. R2 of the Freundlich adsorption isotherms is

larger than that in Langmuir adsorption isotherms and close to 1. It means that this Freundlich

model was obeyed by adsorption of chlorpyrifos as shown in Figs. 4.

Adsorption tends to have n between 1 and 10. Larger value of n implies stronger

interaction between the soil and the pesticides (Öztürk and Bektas, 2004). The n values were

1.066 and 0.653 for Sukanalu and Korpri respectively in Freundlich isotherm model, showing

that adsorption process was unfavorable and this has to do with low percentage of the clay

(3.72 and 7.46) and due to the organics material available in the horticultural soil. The

multilayey capacity factor of both pesticides (k) is higher than one which shows the good

interaction between the soil and the pesticides with more interaction in Korpri than Sukanalu.

The Langmuir adsorption isotherm is commonly applied to monolayer chemisorptions of

gases. This isotherm is mainly applied when no strong adsorption is expected and when the

adsorption surface is uniform.

Generally, the effect of organic matter content in the soil into adsorption residue as the

influence of soil clay content. The greater the content of organic material is, the greater the

adsorption. Pesticides have the speed for different decay (half-life). The half-life of this will

affect the resistance properties of the residue in the soil. The greater half-life is the longer it

will stay in the soil and more difficult to be degraded. Activated biochar which has been

incorporated into the soil will have different adsorption power compared to the initial state.

This is due to the possibility of activated biochar adsorb other compounds.

4. CONCLUSION

It was evaluated that Freundlich isotherm was obeyed with adsorption capacity of

cypermethrin about 1.786 mg/g (R2=0.963) for Sukanalu and 1.247 mg/g (R

2=0.983) for

Korpri. Adsorption capacity of chlorpyrifos about 2.529 mg/g (R2= 0.905) for Sukanalu and

5.395 mg/g (R2=0.929) for Korpri. Langmuir isotherm model was not obeyed in this

experiment because the result showed that R2 value was not close to 1. Generally, activated

biochar applied by soil sample of Korpri had larger adsorption capacity than soil sample of

Sukanalu. Adsorption mechanism of pesticide residue was integrated by clay of soil structure,

organic material, and pH value.

Acknowledgement

We thank Indonesian Rubber Research Institute-Sungei Putih Research Center,

University of Medan Area, Ministry of Research and Higher Education (Simlitabmas-

competitive research 2016) for the financial support.

5. REFRENCES

AOAC. (2007). Pesticide residues in foods by acetonitrile extraction and partitioning with

magnesium sulfat. Official method 2007.01

Handayani, M. and E. Sulistiyono. (2009). Test Langmuir and Freundlich Equation On Waste

Absorption Chrom (VI) by Zeolite. Proceedings of the National Seminar on Nuclear

Science and Technology, Bandung. (In bahasa).

Jeffery, S., F.G.A. Verheijen, M. van der Velde, A.C. Bastos. (2011). A quantitative review of

the effects of biochar application to soils on crop productivity using meta-analysis.

Agric. Ecosyst. Environ. 144: 175-187.

Jodeh, S., O. Khalaf, A.A. Obaid, B. Hammouti, T.B Hadda, W. Jodeh, M. Haddad, I. Warad.

(2013). Adsorption and kinetics study of abamectin and imidacloprid in greenhouse

soil in Palestine. J. Mater. Environ. Science 5(2), 571-580.

Lee, Y., J. Park, K.S Gang, C. Ryu, W. Yang, J.H. Jung, and S. Hyun. (2013). Production and

characterization of biochar from various biomass materials by slow pyrolysis.

Technical Bulletin 197: Food and Fertilizer Technology Center, Taiwan.

Lehman, J., J. Gaunt, M. Rondon. (2006). Biochar sequestration in terrestrial ecosystem-a

review. Mitig. Adapt. Strat. Gl., 11:403-427.

Öztürk N., Bektas T. E. (2004). J. Hazar. Mat., 112 (2004) 155.

Preston, C.M., M.W.I. Schmidt. (2006). Black (pyrogenic) carbon in boreal forests: a

synthesis of current knowledge and uncertainties. Biogeosciences 3: 211-271.

Shuji, Y. and S. Tanaka. (2013). Biochar and compostization: maximization of carbon

sequestration with mitigating GHG emission in farmlands. Technical Bulletin 196:

Food and Fertilizer Technology Center, Taiwan.

Sohi, S.P. (2012). Carbon storage with benefits. Science 338: 1034-1035.

Tiwari, M. and S. Guha. (2012). J. Environ Eng 138(2012) 426.

Tu. (2001). Weed control methods handbook. The nature conservancy. Version April 2001.

Van Zweiten, L., B. Singh, S. Joseph, S. Kimber, A. Cowie, and K.Y. Chan. (2009). Biochar

and emissions of non-CO2 greenhouse gases from soil (Ch.13), in: Lehmann, J. and

S. Joseph (Eds.), Biochar for environmental management. Earthscan, Gateshead,

UK, p.227-249.

Woolf, D., J.E. Amonette, F.A. Street-Perrot, J. Lehmann, S. Joseph. (2010). Sustainable

bichar to mitigate global climate change. Nat. Commun.1, Article number 56.