Odette Varela MillaWu-Jang Huang PhD.

National Pingtung University of Science and TechnologyPingtung, Taiwan.

Contents: Objectives Introduction Characteristics of carbonized rice residues Biochar preparation and characterization Scanning electron microscopy analysis Water spinach Worm avoidance test Soil Application of rice husk biochar and wood

biochar to soil Results

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Objectives:

Realize an investigation of the short-term effects

related to slow pyrolysis biochar effects in plant

growth.

Furthermore it is planned to determine biochar

characteristics such as biodegradability, porosity and

cation exchange capacity, produced from agricultural

waste.

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Organic waste as feedstock for biochar production

Many different materials have been proposed as biomassfeedstocks for biochar, including wood, grain husks, nutshells, manure and crop residues, (Lua et al., 2004, Martinez etal., 2006, Gonzalz et al., 2009).

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The use of rice straw and rice husk has been practiced for a longtime (Ponamperuma, 1982; Eagle et al., 2000; Singh et al., 2008;Kaewpradit et al., 2009).

Karmakar et al., (2009) studied the effect of application of fly ashand rice husk ash, the study showed that the application of thesetype of waste improved soil properties by decreasing soil bulk densityand increasing soil pH, organic carbon, available nutrients, and cropsyield.

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The total amount of crop residues produced each year in rice-basedsystems of Asia can be roughly estimated at about 112 million tons ofrice husks (based on 2005 production and a husk/paddy ratio of 0.2).(Pandey 1998)

Asia and China Rice Production 2008

Residue burning is widely practiced and causes air pollution, humanhealth problems, and considerable nutrient losses.

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Source: http://www.fao.org/corp/statistics/en/

Taiwans cultivated land area

0

50000

100000

150000

200000

250000

Rice Vegetable

s

Fruits Tea Others

cropsOrganic (ha) 949.44 518.43 295.52 139.84 453.1

No organic (ha) 147081.56 151573.57 215067.48 25647.16 13107.9

He

cta

res

99.36% 99.66% 99.86%

99.46%96.66%

0.64%

0.14%

0.54%3.34%

0.34%

Source: Organization of certification Agriculture and Food Agency ,Council of Agriculture. 2009

Characteristics of Carbonized Rice Residues

Carbonized rice husks are a very light material with amicroporous structure and a bulk density of about 0.150 g cm3(Nakajima 1986).

The structure of rice husks is preserved in the carbonizationprocess but carbonized husks break easily, especially ifcarbonized at high temperatures.

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Biochar was found to be alkaline in nature (pH 8.2). Rice husk biocharproduced under temperatures between 500 and 600 , showed anoticeable increment in silicon, calcium, potassium and magnesiumcontent.

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Biochar preparation and characterization

Scanning electron microscope analysis

The EDS point analysis of rice husk indicated that the biocharparticles consisted of high silicon mineral agglomerates on lowercarbon content fibers with structures typical of its biomassorigin

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Wood biochar EDS point analysis, indicated that the biocharparticles consisted of high potassium, chlorine, and calcium.

Mineral agglomerates also showed high carbon content

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To investigate and quantify effects of rice husk-basedbiochar and wood-based biochar on the growth of waterspinach, a field experiment was carried out under differenttreatments, consisting of:

(1) control soil and fertilizer,

(2) soil with rice husk biochar and fertilizer in fivedifferent quantities,

(3) and soil with wood biochar and fertilizer in fivedifferent quantities.

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From the literature, the recommends amount of rice husk biocharthat should be applied is: 10 ton per hectare (Biochar and CarbonSequestration, a regional perspective, 2009).

1.94 m

1.10 m

Water spinach

Water convolvulus has been widely grown throughout the world. It isfound in South and Southeast Asia, Tropical Africa, SouthAmerica, and Oceania (Wenfang, 1997). However, it is only in southand Southeast Asia that it is an important leafy vegetable.

16http://waynesword.palomar.edu/ww0804.htm

Worm avoidance test

A toxicity test was conducted before starting the biocharexperiment. Following the guidelines from A guide toconducting biochar trials (Major. J., 2009) we realized aworm avoidance test

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We made our trial with 50 worms that were purchased in a fish shop

The container was prepared with rice husk biochar and soil fromthe experimental field. We had as a result that most of theworms shown an acceptance for rice husk biochar

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Soil

The experiment was conducted on an uncultivated clayey Ultisol soil, which are strongly leached, acid forest soils with relatively low native fertility.

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Germination comparison between Soil field with Biochar andsoil field without biochar

Soil with biochar shows the best germination

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Application of rice husk biochar and wood biochar to soil

Soil preparation21

Biochars were weighted and later added to each one of the plots

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Top soil mixing technique (Major, 2009)

Before transplanting was necessary to irrigate for 10 minutes

Following the literature recommendations, plants were transplanted in a distance of 15cm between them.

Each plot had 22 plants

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Morphology

Leaf number

Leaf length and wide

Stem size

Stem number

Root size

Weight

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Results:

Water spinach plants for all of the considered treatments were harvested after 8 weeks.

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Effect of rice husk biochar and wood biochar on plant root growth

All water spinach plants were measured before harvesting; carefully plants and roots were removed from soil.

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Statistical analysis

Both biochar treatments where compared using leastsignificant difference (LSD), for their main effectson plant growth properties (SAS 9.1, 2004).

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0 1 2 3 4 50

20

40

60

80

100

120

140

160

Leaf le

ngth

(m

m)

Treatments

Rice husk

Wood

0 1 2 3 4 50

10

20

30

40

Le

af

nu

mb

er

Treatments

Rice husk

Wood

0 1 2 3 4 50

5

10

15

20

Leaf w

ide (

mm

)

Treatments

Rice husk

Wood

0 1 2 3 4 50

20

40

60

80

100

120

140

160

Leaf le

ngth

(m

m)

Treatments

Rice husk

Wood

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0 1 2 3 4 50.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Ste

m n

um

ber

Treatments

Rice husk

Wood

0 1 2 3 4 50

50

100

150

200

Ste

m s

ize

(m

m)

Treatments

Rice husk

Wood

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Randomly we choose water spinach plants from eachtreatment, T1, T2, T3, T4, T5, treated with each one of the biochars.

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0 1 2 3 4 50

50

100

150

Ro

ot

siz

e (

mm

)

Treatments

Rice Husk

Wood

Effect of rice husk biochar and wood biochar on plant fresh weight

From each treatment, plants were collected

All plants were classified by treatment

Plants were weighted35

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0 1 2 3 4 50.0

0.1

0.2

0.3

0.4

0.5

0.6

We

igh

t (k

g)

Treatments

Rice Husk

Wood

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Figure 4.1 Figure 4.2

Conclusions

Rice husk biochar showed better holding capacity than woodbased biochar, due to the differences in their particle size, ricehusk biochar was able to integrate better into soil making thedistribution more uniform.

Water spinach requires plenty of water because of its highsucculence, regardless of this information, we irrigated theplants every 2 days for only 10 minutes.

The plants were able to absorb the water that biochar wasretaining, being not affected by the lack of water.

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