i

Abstract:

Among the major factors for the soils to be considered fertile and productive, is presence of soil

organic carbon (SOC). Soil organic carbon plays a great role in improving the structure of the

soil as well as its tilth, increasing water holding capacity of the soils making water more

available to plants and reduction of soil erosion due to improved soil structures. Reduction in soil

erosion by biochar, reduces nutrients removal from the soil surface making the soil retain its

fertility. All these benefits of SOC result into increased or improved yields of various crops

grown in fields with appreciable amount of SOC.

Various organic materials have been scientifically proven to contain carbon which could be

applied in the fields for the purpose of improving soil fertility especially in the fields with

extremely poor soil fertility. One of such organic materials could be biochar made from rice

husks.

However, the potentiality of rice husks as materials for soil amendment is generally ignored

among Tanzanias farmers. A laboratory experiment was therefore conducted to investigate the

potentiality of biochar made from rice husks as soil amendment. Biochar produced from rice

husks was analyzed in the laboratory using standard methods to determine the levels of different

plant essential nutrients which it could release in case is applied in the field. The study showed a

presence of 15% Organic carbon, 0.49% Total N and a pH vaue of 5.73 in water, all of which

exceed the optimal range of plants nutrients required in the soil for optimal to high yield

production. Moreover, the exchangeable bases, appeared to exceed the optimal range of nutrients

required in the soil for optimal plant growth.

Therefore, application of biochar from rice husks is very imperative to increase soil fertility,

enhance nutrient uptake, and to reduce the negative effects to crops caused by poor soil fertility

accounted by low amount of soil organic carbon.

ii

DECLARATION

I, FORTUNATUS ALEXANDER, do hereby declare that this work is a result of my personal

effort and that the best of my knowledge, it has never been submitted to any university as a

partial fulfillment for any degree award.

Signature ………………………………..Date ……………………………….

iii

COPY RIGHT

No part of this document may be reproduced, stored in any retrieval system or transmitted in any

form or by any means without prior written permission of the author or Sokoine University of

Agriculture on behalf.

iv

AKNOWLEDGEMENT

I give special thanks to my supervisor Dr. Amur Nyambilila who spent a lot of her time to

advice, direct and instruct me on different issues related to my special project, all of which

enabled me to accomplish this hard task.

I also extend my appreciation to HESLB for their financial support. It will not be fair if I forget

to give my thanks to the staff members of the soil science laboratory for their encouragement

assistance in sample preparation and analysis, and to my friend Sikazwe Willy, for his moral

support and encouragement during my study period. I wish them all the best and may Almighty

God bless them in whatever good things they do.

v

LIST OF ABBREVIATIONS AND SYMBOLS C………………………Carbon

Ca……………………..Calcium

Cu……………………..Copper

HESLB………………..High Education Students’Loan Board

Mg……………………..Magnesium

Mn……………………Manganese

pH……………………negative logarithm of H+ in the soil solution

SOC………………….Soil organic carbon

Zn…………………….Zinc

K……………………...Potassium

Kg……………………Kilogram

%.................................Perc

vi

DEDICATION This work is dedicated to my beloved parents; Paul P.M. Bupamba and Emiliana M. Chongoma,

my sisters Mrs. A kimisha and all my family members who sacrified a lot towards my education.

I also dedicate this work to all my beloved friends for their encouragement, support and prayers

during my studies. May Almighty God bless them all.

vii

TABLE OF CONTENTS

Abstract:................................................................................................................................................... i

DECLARATION .................................................................................................................................... ii

COPY RIGHT ........................................................................................................................................ iii

AKNOWLEDGEMENT ......................................................................................................................... iv

LIST OF ABBREVIATIONS AND SYMBOL ........................................................................................ v

DEDICATION ....................................................................................................................................... vi

1.0 Introduction ....................................................................................................................................... 1

1.1 Problem statement. ............................................................................................................................ 2

1.2 Justification. ...................................................................................................................................... 3

1.3 Objectives of the study....................................................................................................................... 3

1.3.1 General objective. ........................................................................................................................... 3

1.3.2 Specific objectives. ......................................................................................................................... 3

2.0 Literature review. .............................................................................................................................. 4

2.1 Historical perspective of Biochar ....................................................................................................... 4

2.2 Influence of Biochar on biological processes ...................................................................................... 4

2.3 Adsorption properties of biochar and nutrient retention ...................................................................... 4

2.4 Effect of biochar on soil physical properties ....................................................................................... 5

2.5 Biochar and Soil C sequestration ....................................................................................................... 5

3.0 Materials and Methods ....................................................................................................................... 6

3.1 Collection and pyrolysis of rice husks ................................................................................................ 6

3.2 Biochar chemical analysis. ................................................................................................................. 7

4.0 Data analysis ..................................................................................................................................... 7

5.0 Discussion and interpretation of the findings ...................................................................................... 8

5.1 Biochar Organic carbon. .................................................................................................................... 8

5.1 Biochar Exchangeable bases .............................................................................................................. 9

5.2 Biochar pH ........................................................................................................................................ 9

6.0 Conclusion. ..................................................................................................................................... 11

7.0 REFERENCES ................................................................................................................................ 12

viii

LIST OF FIGURES.

Table 1: Biochar sample parameters and the methods used used to determine them .................................. 7

Table 2: Biochar laboratory analytical results .......................................................................................... 7

1

1.0 Introduction One of the major factors for the soils to be considered fertile and productive is presence of soil

organic carbon (SOC). Soil organic carbon plays a great role in improving the structure of the

soil as well as its tilth. Soil organic carbon increases water holding capacity of the soils making

water more available to plants (Lal, 2004). Also due to improved soil structure caused by the

presence of soil organic carbon, soil erosion is reduced to a large extent because the soil particles

become strongly held in the soil body. As the result, nutrients removal from the soil surface is

reduced making the soil retain its fertility. All these benefits of SOC result into increased or

improved yields of various crops grown in fields with appreciable amount of SOC.

Several ways are available for increasing SOC, which includes using manures, compost,

conservation tillage, and conversion of monoculture to complex diverse cropping systems.

(Sauerbeck, 2001). Apart from these ways, biochar has also been found to be one of the major

sources of organic carbon in the soil. (Skjemstad 2001; Skjemstad et al. 2002).Soil organic

carbon differs from biochar in that, while biochar describes black carbon formed through

pyrolysis of plant biomass and other organic materials (Woolf et. al. 2008), soil organic carbon

refers to the carbon (in organic or inorganic form) occurring in the soil in soil organic matter

(Milne, E., 2009). Soil organic matter (SOM) describes the organic constituents in the soil

(tissues from dead plants and animals, products produced as these decompose and the soil

microbial biomass), (Milne, E., 2009). Thus, in formation of soil organic carbon, ther is no

burning (pyrolyisis) of organic materials as done in biochar production.

Despite their differences biochar and soil organic carbon are important for the function of

ecosystems and agro-ecosystems having a major influence on the physical structure of the soil,

the soil's ability to store water (water holding capacity), and the soil’s ability to form complexes

with metal ions and supply nutrients( Like in absence of biochr (black carbon), loss of SOC can,

therefore, lead to a reduction in soil fertility and land degradation. (Milne, E., 2009).

Biochar refers to the porous carbonaceous solid produced by themochemical conversion of

organic materials in an oxygen depleted atmosphere which has physiochemical properties

suitable for the safe and long term storage of carbon in the environment and, potentially soil

improvement (Shackley and Sohi, 2010). Also, Woolf et. al. (2008), defined the term 'biochar' as

2

black carbon formed by the pyrolysis of biomass; the term pyrolysis means heating of biomass in

an oxygen-free or low oxygen environment such that it does not (or only partially) combusts.

Therefore, the term biochar may simply be defined as a product of burnt plant materials

(biomass) or feed stocks in an environment that does not allow the escape of carbon stored in

such materials. Biochar and charcoal (traditional charcoal), may be similar in that they are all

products formed through burning of the plant biomass in an oxygen-free or low oxygen

environment such that it is only partially combusts. The difference between charcoal and biochar

may be that, while charcoal is formed by necessarily burning of woody plant materials, biochar

encompasses black carbon produced from any biomass feedstock including animal and poultry

dung. Thus, for charcoal to be applied into the soil as source of organic carbon has to be crushed

to form a powdery form.

Different countries in the world have been using different plant residues in producing biochar,

and rice husks being one of such materials. Rice husks are pyrolised using modern technologies

to form biochar. (Biochar Project from the UK Biochar Research Centre.Final Report Available,

(2011). But research have shown that the availability of rice husks all over the world is very

large compared to the needs for them to be used in biochar production. In other words, rice husks

are less used in biochar production compared to their use as source of fuels, methane gas and

electricity.

1.1 Problem statement. One of the major causes of decrease in crop yield is the decline of organic carbon in the soils.

Organic carbon in soils, increasingly get degraded due to poor agronomic management practices

among most farmers. But biochar is stable in soils. It does not rapidly degrade. It becomes a

fungal matrix and a water filter. Water flows down into the soil, hits the char layer and

flows through. As it does so, it leaves nitrogen, potassium and other essential nutrients

trapped in the matrix (Bohemian, 2008).

Moreover, in Tanzania the characteristics of biochar originating from charcoal and rice husks has

not been explored, considering variability of soils and biomass used for biochar production.

Thus, the potential of biochar as soil amendment is still uncertain. The ability of biochar to

3

increase fertility status of the soils depends on the biochar nutrient contents and its influence of

physic-chemical properties of soils.

This study was made to characterize the biochar in terms of nutrient content, heavy metals

content, and chemical properties so as to deduce the potentiality biochar from rice husks and

charcoal as soil amendment.

1.2 Justification. This study was made to determine the ways to replace the degraded organic carbon in soils

which contribute to low crop yields in Tanzania. For so many years, the rice husks and charcoal

wastes have been thrown away after rice milling and charcoal use. These potential sources of C

could be applied into the soils and increase the C store which is very essential for soil

amendment. Furthermore, the study provided general information on the potential of biochar as

soil amendment, information of which seemed to be helpful in waste disposal and or recycling of

these wastes to benefit agricultural land.

Having done this study, Tanzania’s farmers are now expected to benefit by increasing their crop

yields which will in turn improve their life standards.

1.3 Objectives of the study.

1.3.1 General objective. To characterize biochar from rice husks and charcoal wastes for their potential as soil

amendments.

1.3.2 Specific objectives. • To determine the extractable elements present in biochar from rice husks and charcoal

which play part in increasing the fertility of soils.

• To determine the physical chemical properties of biochar including cation exchange

capacity (CEC), exchangeable bases, and Ph.

• To compare characteristics of biochar produced from different biomass and from

different soils.

4

2.0 Literature review.

2.1 Historical perspective of Biochar The greatest suggestion that biochar may be beneficial to soil fertility comes from studies of the

Amazonian Dark Earth (ADE) soils known as terra preta and terra mulata which contain high

levels of black carbon (biochar) formed through natural forest fires (Glaser 2001). Amazonian

Dark Earth (ADE) soils are prized for their high nutrient levels and high fertility (Lehmann et al,

2003). The high cation exchange capacity (CEC) of ADEs compared to adjacent soils is due to

its black carbon content (Liang et al 2006). The obvious question that came following this

suggestion was whether adding black carbon to other soils might have similar beneficial effect

on their fertility. To find out the answer to this question, different researches were carried out

and the following are some of the information found about biochar as soil amendment, (the

information of which are based on properties of biochar)

2.2 Influence of Biochar on biological processes Biochar can increase microbial activity and reduce nutrient losses during composting (Dias et al.

2010). Some indications exist from soils that are rich in bio-char, that; microbial community

composition, species richness, and diversity, change with greater bio-char concentrations.

Pietika¨inen et al., (2000); Yin et al., (2000); and Thies and Suzuki, (2003), found a greater

bacterial growth rate in layers of charcoal than in the underlying organic horizon in a temperate

forest soil. Also, a greater microbial biomass was reported in forest soils in the presence of

charcoal by Zackrisson et al. (1996), and higher microbial activity (CO2 production as well as

organic matter decomposition) was found in soils exposed to black carbon aerosols derived from

charcoal making (Uvarov, 2000), all of which are evidences of potentiality of biochar and

charcoal as soil amendment in increasing microbial activities.

2.3 Adsorption properties of biochar and nutrient retention Biochar is considered to have the potential to reduce leaching of pollutants or nutrients from

agricultural soils (Lehmann et al 2006). The potential to reduce leaching is due to strong

adsorption affinity of biochar for soluble nutrients such as ammonium (Lehmann et al. 2002),

nitrate (Mizuta et al. 2004), phosphate (Beaton et al. 1960), and other ionic solutes (Radovic et

al. 2001). What is special about biochar is that it is much more effective in retaining most

5

nutrients and keeping them available to plants than other organic matter such as for example leaf

litter, compost or manures Lehmann, (2007). Interestingly, this is also true for phosphorus which

is not at all retained by 'normal' soil organic matter. This property of biochar aids in nutrient

retention in the soils making the soils fertile for a long time.

2.4 Effect of biochar on soil physical properties Soil at charcoal manufacturing sites were found to have 8% greater hue, and 20% higher value

and chroma. (Oguntunde, (2008). This shows that, when biochar and charcoal are applied into

the soil, especially in soils that are low in organic matter, can dramatically darken the colour of

soil. Darkening of the colour of the soil, has a great influence on soil temperature making soils

suitable for cultivation of crops which require soils of moderate to high temperature levels

(Ketterings et al., 2000). This concept was also supported by (Krull et al., 2004). who said that,

dark soils absorb more solar energy, a state of which may cause higher soil temperatures and

affect rate processes, enhancing the cycling of nutrients and potentially extend the growing

season in seasonal climates.

One important thing to note is that, it is important to be cautious when handling dry biochar,

which is very dusty and should not be spread in windy conditions. This can be easily remedied

by wetting the biochar before application. Respiratory protection (e.g., dust mask) should be

worn when handling the dry material. The reason behind is to avoid harm that may be caused by

contaction or inhalation of biochar.

2.5 Biochar and Soil C sequestration Apart from being a source of carbon in soils, a number of studies have highlighted the net benefit

of using biochar in terms of mitigating global warming (Lehmann, 2007a; Lehmann, 2007b;

Lehman et al., 2005; Ogawa et al., 2006;Laird, 2008; Mathews, 2008; Woolf, 2008). When the

organic materials are charred, much of the carbon becomes “fixed” into a more stable form

(Liang et al.2008), and when the resulting biochar is applied to soils, the carbon is effectively

sequestered. Also it is estimated that, use of this method to store C in soils has the potential to

reduce current global carbon emissions by as much as 10 percent (Woolf et al. 2010). However,

relatively few studies exist that make a quantitative assessment of biochar-based soil

management scenarios with regard to greenhouse gas, energy, and economic perspectives

6

(Fowles, 2007; Gaunt et al., 2008), and more so in the tropics. Before biochar can be widely used

as soil amendment, there is a need for adequate information about biochar properties.

3.0 Materials and Methods

3.1 Collection and pyrolysis of rice husks Rice husks were collected from Mang’ula village in Kilombero district, and were air dried. The

rice husks were then pyrolysed by using a locally made kiln. A pyrolising kiln was locally

fabricated using iron metals. Before pyrolising the rice husks, the kiln was filled with burning

charcoal and was left for one day so as to remove the colours which were painted on it.The

reason to remove the colour was to prevent contamination of the sample by metallic elements

present in such colours . Having been removed their colours; the kilns were washed with water

and soap to make them clean ready for pyrolising the rice husks.

The kiln was dried and the rice husks were then poured into it. A few burning charcoal solids

were put into the kiln for burning the rice husks. Only a little oxgen to support burning of the rice

husks was allowed to enter the kiln through a small opening on top of the kiln.The rice husks

were left to burn and cool for two days.

After two days, almost 90% of the rice husks were completely pyrolised. The pyrolysed rice

husks were sampled and ground to pass through 2 mm sieve for chemical analysis.

7

3.2 Biochar chemical analysis. The prepared biochars samples were analyzed in the laboratory by using standard methods as

summarized in the table below:

Table 1: Biochar sample parameters and the methods used used to determine them

Parameter of the sample to be

analysed.

Method to be used

1. Exchangeable bases. Total analysis (dry digestion)

2.Exchangeable Mn,Zn,Cu DTPA

3.Extractable Phosphorus Olsen

4.Extractable Sulphur/SO4 Turbidimetric

5. pH of the sample ( in H2O ) pH meter

6.Total Nitrogen Macro Kjeldahl ( wet digestion )

7. Organic carbon Walkely – Black method.

4.0 Data analysis Data collected were summarized in a tabular form as shown below Table 2: Biochar laboratory analytical results

Sample parameter Value Exchangeable K (Cmol(+)kg-1) 2.51

Exchangeable Na (Cmol(+)kg-1) 2.99

Exchangeable Ca (Cmol(+)kg-1) 0.51

Exchangeable Mg (Cmol(+)kg-1) 2.24

Exchangeable Mn (mg/L ) 63 Extractable Sulphur/SO4 (mg/Kg) 27.52

Extractable Phosphorus ( % ) 0.047 Exchangeable Copper ( mg/L ) 1.07 Exchangeable Zinc ( mg/L) 2.67 Total Nitrogen ( % ) 0.49 Organic Carbon ( % ) 15 pH in water 5.73

8

5.0 Discussion and interpretation of the findings The biochar analytical results obtained through this study have shown a great potentiality of

biochar from rice husks as soil amendment. Although crops have different levels of nutrient

requirements and pH values, biochar has been found to be of great importance to all crops whose

nutrients requirements are within the nutrient range that may be achieved through application of

biochar.

5.1 Biochar Organic carbon. The biochar analytical results indicated the presence of high quantity of organic carbon in

biochar. The high value of organic carbon in biochar could be resulted from the presence of high

amount of carbon in rice husks. Thus, if biochar is applied in the soils, it would release this

organic carbon which serves a lot of positive effects in the soils for proper growth of various

crop plants. Soils treated with biochar are characterized by having high organic carbon content.

The high content of Organic carbon in biochar treated soils, indicates the recalcitrance of organic

carbon in biochar. (Glasser et al. 2002; Lehman et al., 2003; Rondon et al., 2007)

This organic carbon in biochar is very important for soil amendment as it increases water holding

capacity, improves soil structure, decreases uptake of soil toxins and other many functions

including carbon sequestration as its carbon is very stable that it may reside in soils over

decades, centuries, even up to millennia. However, even though some of these functions may

lead directly or indirectly to increased production in some soils, the benefit of biochar is not

universal. In fact, some biochars may have adverse effects on plant growth, and not all soils

respond to biochar additions in the same way (Ernsting and Smolker, 2009; Senjen, 2009).

Researches have to be done before application of biochar in the fields so as to predict the effects

of biochar application in such fields. This is essential since studies that have reported positive

effects with regard to crop production, often involved highly degraded and nutrient-poor soils,

whereas application of biochar to fertile and healthy soils does not always yield a positive

change. (Krull, E.S et al.2006)

9

5.1 Biochar Exchangeable bases The presence of high values of exchangeable bases in biochar as indicated by the biochar sample,

might be attributed by the presence of ash in the biochar which helps in the immediate release of

the occluded mineral nutrients like Ca, K , Mg and Nitrogen for crop use. These results obtained

from the laboratory analysis of biochar agree with (Glasser et al. 2002; and Lehman et al., 2003

who reported the high exchangeable bases in biochar applied soils. They suggested that, the

increase in exchangeable bases in their experimental fields through application of biochar could

be resulted from inherent characteristics of biochar which include high surface area, high

porosity, variable charge organic materials that have the potential to increase soil cation

exchange capacity(CEC),surface sorption capacity and base saturation when added to soil.

Therefore it is quite logical that, soils applied with biochar will have high CEC (Chan et al.

(2007).

5.2 Biochar pH

Another significance of biochar that has been revealed through this study, is its ability to rise pH

in acidic soils. This result indicated that rice husk biochar could be used as a substitution for lime

materials to increase the pH of acidic soils (Chan et al. (2007). Different crops have different pH

value requirements. Other crops require low pH value for their optimal growth while other crops

require high pH values. Since the pH value of biochar has been found to be approximately 6, it is

an indication that, biochar could suit to be applied in soils with low pH in case crops which

require high pH are to be grown in fields whose soil pH are lower than that required by the crops

in question. For example the application of biochar results in plants which do better with a more

acid soils such as strawberries, blueberries or such nightshade plants as potatoes or tomatoes -,

the application of biochar will often lead to a worsening of yields of such crops. On the other

hand the application of biochar on acid soils improves the living conditions of such plants as

cucumbers and cabbage, plants preferring a more alkaline environment. Therefore, soil analysis

is very important to be done before application of biochar in any field intended to grow any kind

of crops.

Although some properties of biochar such as high amount of exchangeable bases and pH value

favor only certain crop families, certain effects of biochar, such as increasing a soil’s ability to

store water, to provide better aeration or to increase electrical conductivity are deemed positive

for all crop families.( Hans-Peter Schmidt und Claudio Niggli, 2011) These positive aspects can

10

however at least in the short term be overweighed by more significant changes in soil

ecosystems, thereby leading to an overall decline in yields. This is to say that, it is not

necessarily that whenever biochar is applied in the field whose fertility status would be increased

by biochar, must increase the yield, some factors such as significant changes in soil ecosystem

may interfere the growth of crops leading to low crop yield.

11

6.0 Conclusion.

The results obtained in this study, reveal that application of biochar in different soils of low or

poor fertility status, could increase soil organic carbon, total nitrogen, available phosphorus,

exchangeable bases ( K, Na, Ca, and Mg ) and adjust soil pH to the range that is optimal to most

crops, thus improving the fertility of such soil. The increase in elemental plant nutrients P, K,

and Ca is as a result of addition of plant nutrients contained in the biochar (Ponamperuma, 1982).

Also the results showed low content of micronutrients in biochar a thing that could be significant

in reducing the subjection of soils to nutrient toxicity as micronutrients are required by plants in

a small quantity.

As the results have indicated, the presence of high quantity of plant nutrients in biochar

associated with other physical properties of biochar such as, high surface area and porous nature

of biochar, are identified as the main reasons for the increase in soil fertility and highest nutrient

uptake by plants in biochar treated soils. Also biochar’s ability to act as a medium for

microorganism due to provision of favorable environment for such micro organism has been

found to be an added advantage as far as soil amendment processes are concerned.

Therefore, application of biochar in the agricultural fields among Tanzania’s farmers could be

imperative in order to increase soil fertility and enhance nutrient uptake by crop plants all of

which would result into high crop yields especially where agricultural activities seem to be not

economically beneficial due to poor soil fertility.

12

7.0 REFERENCES Beaton, J.D., Peterson, H.B. and Bauer, N. 1960, Some aspects of phosphate adsorption by charcoal. Soil Science Society of America Proceedings 24, 340–346. Biochar Project from the UK Biochar Research Centre.Final Report Available, (2011). Bohemian, (2008), Agrichar: Carbon-negative Biofuel and Charcoal that Restores Soil Fertility. Chan, K.Y., van Zwieten, B.L., Meszaros, I., Downie, D., & Joseph, S. (2007). Agronomic values of greenwaste biochars as a soil amendments. Australian Journal of Soil Research, 45, 437–444. Dias, B.O., Silva, C.A., Higashikawa, F.S., Roig, A. and Sanchez- Monedero, M.A. 2010. Use of biochar as bulking agent for the composting of poultry manure; effect on organic matter degradation and humification. Bioresource Technology 101:1239–1246. Ernsting, A., & Smolker, R. (2009). Biochar for climate change mitigation: Fact or fiction. [Online] Available: www.biofuelwatch.org.uk/docs/biocharbriefing.pdf. February 2009. Retrieved via Internet Explorer Ver. 6, 2 June 2012 Fowles, M., 2007. Black carbon sequestration as an alternative to bioenergy. Biomass and Bioenergy 31: 426-432. Gaunt, J.L. and Lehmann, J. 2008. Energy balance and emissions associated with biochar sequestration and pyrolysis bioenergy production. Environmental Science and Technology 42: 4152-4158. Glaser, B. et al., (2001). The Terra Preta phenomenon: A model for sustainable agriculture in the humid tropics, Naturwissenschaften, 88, 37–41 . Glaser, B., Lehmann, J., & Zech, W. (2002). Ameliorating physical and chemical properties of highly weathered soils in the tropics with charcoal: A review. Biol Fertil Soils., 35, 219–230. Hans-Peter Schmidt und Claudio Niggli. Biochar Gardening – results. Journal for ecology,winegrowing and climate farming. (2011) pp. 5 Ketterings, Q.M. and Bigham, M., 2000. Soil color as an Indicator of slash-and-burn fire severity and soil fertility in Sumatra, Indonesia. Soil Science Society of America Journal 64, 1826-1833.

13

Kisetu, E., (2011/11), Lecture notes. Sokoine University of Agriculture, Department of Soil Science. Krull, E.S., Skjemstad, J.O., Baldock, J.A., 2004. Functions of soil organic matter and the effect on soil properties. In: Grains Research and Development Corporation, pp. 129. Krull, E.S., Swanston, C.W., Skjemstad, J.O. and McGowan, J.A., 2006, Importance of charcoal in determining the age and chemistry of organic carbon in surface soils, Journal Of Geophysical Research, pp.111. Laird, A.D., 2008. The charcoal Vision: A win-win-win scenario for simultaneously producing bioenergy, permanently sequestering carbon, while improving soil and water quality. Agronomy Journal 100, 178-181. Lal, R. 2004. Soil Carbon Sequestration Impacts on Global Climate Change and Food Security. Science 304:1623-1627. Lehmann, J., 2007a. A handful of carbon. Nature 447, 143-144. Lehmann, J., 2007b. Bio - energy in the black. Frontiers in Ecology and the Environment 5, 381-387. Lehmann, J., da Silva Jr, J.P., Rondon, M., Cravo, M.S., Greenwood, J., Nehls, T., Steiner, C. and Glaser, B.: 2002, ‘Slash-and-char – a feasible alternative for soil fertility management in the central Amazon?’, Proceedings of the 17th World Congress of Soil Science, (pp. 1–12) Bangkok, Thailand. Lehmann, J., J. Gaunt, and M. Rondon. 2006. Bio-char sequestration in terrestrial ecosystems - a review. Mitigation and Adaptation Strategies for Global Change 11:403-427. Lehman, J., J.P. Da Silva Jr, C. Steiner, T. Nehls, W. Zech and B. Glaser, 2003. Nutrient availability and leaching in an archaeological Anthrosol and a Ferralsol of the Central Amazon basin: fertilizer, manure and charcoal amendments. Plant and Soil, 249: 343-357. Liang, B., J. Lehmann, D. Solomon, J. Kinyangi, J. Grossman, B. O'Neill, et al. 2006. Black Carbon Increases Cation Exchange Capacity in Soils. Soil Science Society of America Journal. 70 (5): 1719-1730.

14

Liang, B., Lehmann, J., Solomon, D., Sohi, J S., . Thies, E., Skjemstad, J.O., Luizao, F.J., Engelhard, M.H., Neves, E.G. and Wirick. S. 2008. Stability of biomass derived black carbon in soils. Geochimica et Cosmochimica Acta 72: 6096–6078. Matthews, J.A., 2008. Carbon negative biofuels. Energy Policy 36, 940-945. Mengel, D. D.,(2011), Department of Agronomy, Purdue University. "Fundamentals of Soil Cation Exchange Capacity". http://www.ces.purdue.edu/extmedia/AY/AY-238.html. Milne E., (Lead Author); Heimsath, A. (Topic Editor), (2009), "Soil organic carbon". In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). Mizuta, K., Matsumoto, T., Hatate, Y., Nishihara, K. and Nakanishi T.: 2004, Removal of nitratenitrogen from drinking water using bamboo powder charcoal, Bioresource Technology 95: 255–257. Ogawa, M., Okimori, Y., Takahashi, F., 2006. Carbon sequestration by carbonization of biomass and forestation: three case studies. Mitigation and Adaptation Strategies for Global Change 11, 429-444. Pietika¨inen, J., Kiikkila¨, O., and Fritze, H., (2000). Charcoal as a habitat for microbes and its effects on the microbial community of the underlying humus, Oikos, 89, 231–242. Ponamperuma, F.N. (1982). Straw as source nutrient for wetland rice. In S. Banta & C.V. Mendoza (Eds.), Organic matter and rice (pp 117-136). Los Banos, the Philippines: IRRI. Radovic, L.R., Moreno-Castilla, C. and Rivera-Utrilla, J. (2001), ‘Carbon materials as adsorbents in aqueous solutions’, In Radovic L.R. (ed.), Chemistry and Physics of Carbon, (pp. 227–405) NewYork, Marcel Dekker.

Rondon, M. A., Lehmann, J., Ramirez, J., & Hurtado, M. (2007). Biological nitrogen fixation by common beans (Phaseolus vulgaris L.) increases with bio-char additions. Biology and Fertility of Soils, 43, 699 -708. Sauerbeck, D. R. 2001. CO2 emissions and C sequestration by agriculture - perspecives and

limitations. Nutrient Cycling in Agroecosystems 60:253-266.

15

Senjen, R. (2009). Biochar, another dangerous techno fix. Friend of Earth Australia. [Online] available: www.foe.au.org. Retrieved via Internet Explorer Ver. 6, 2 June 2012. Skjemstad, J. O., D. C. Reicosky, A. R. Wilts, and J. A. McGowan. 2002. Charcoal carbon in US agricultural soils. Soil Science Society of America Journal 66 (4):1249-1255. Skjemstad, Jan. 2001. Charcoal and other resistant materials. Paper read at Net Ecosystem Exchange Workshop Proceedings, Canberra ACT 2601, Australia. Thies, J. and Suzuki, K., (2003). Amazonian dark earths: Biological measurements, In: Amazonian Dark Earths: Origin, Properties, Management, Lehmann, J. et al., Eds., Kluwer, Dordrecht, 287–332. Woolf, D., 2008. Biochar as a soil amendment: A review of the environmental implications. In: Swansea. Yin, B. et al., (2000). Bacterial functional redundancy along a soil reclamation gradient, Applied Environtal Microbiology., 66, 4361–4365.