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Biochar for Carbon Sequestration, Reduction of Greenhouse Gas Emissions and Enhancement of Soil Fertility; A Review of the Materials Science


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When biomass is pyrolysed it produces a syngas, bio-oils and charcoal. When this charcoal (biochar) is applied to soils, research has shown that it can increase soil health, crop yields, reduce leaching of organic and inorganic fertilisers, and some evidence exists that it can reduce soil emissions of N 2 O and CH 4 ... Biochars have been found to be very stable in many soil environments, when compared to uncharred organic matter, and have considerable potential to sequester carbon from the atmosphere. Progress has been made in understanding the material properties of these chars that result in their efficacy. In this paper an overview of the literature will be presented along with recent results of research work carried out at the University of NSW and Cornell University. Areas where further work is required will be outlined.
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Proceedings of the Australian Combustion Symposium
December 9-11, 2007, University of Sydney
Biochar for Carbon Sequestration, Reduction of Greenhouse Gas
Emissions and Enhancement of Soil Fertility; A Review of the
Materials Science
S D Joseph1, *, A Downie, P Munroe, A Crosky, J Lehmann,2
1School of Material Science and Engineering, University of NSW, NSW 2052 Australia
2 Department of Crop and Soil Sciences, College of Agriculture and Life Sciences, Cornell University, Ithaca, NY
14853, USA;
When biomass is pyrolysed it produces a syngas, bio-oils and charcoal. When this charcoal (biochar) is applied to soils,
research has shown that it can increase soil health, crop yields, reduce leaching of organic and inorganic fertilisers, and
some evidence exists that it can reduce soil emissions of N2O and CH4... Biochars have been found to be very stable in
many soil environments, when compared to uncharred organic matter, and have considerable potential to sequester
carbon from the atmosphere. Progress has been made in understanding the material properties of these chars that result
in their efficacy. In this paper an overview of the literature will be presented along with recent results of research work
carried out at the University of NSW and Cornell University. Areas where further work is required will be outlined.
Keywords: Biochar, Biosequestration, Pyrolysis, Greenhouse gas emissions
1. Introduction
An intensification of agricultural production on a
global scale is necessary in order to secure the food
supply for an increasing world population. As a result,
more and more organic carbon is being removed from
the soil leading to dramatic soil degradation. Many of
Australia’s agricultural soils are already reaching
critically low levels of soil organic carbon. Intensive
agriculture and horticulture in Australia have depleted
organic carbon levels in soil from an estimated 3% to
less than 1% [1]. Organic carbon in the soil enables soil
biota to flourish, assisting the processes of nutrient
flow, increases cation exchange capacity, water and
nutrient retention.
One method of increasing soil health is through the
application of carbonized materials (biochars) that have
long term stability [2]. These materials, added as
pyrolysed organic matter, can be produced from
purpose grown biomass (wood and grasses) and
biomass waste streams such as paper sludge, manure or
greenwaste. Moreover, these chars appear to be able to
reduce the emissions of N2O and CH4.. [3] from soil.
Over the past 3 years considerable research has been
undertaken to measure the physical and chemical
properties of the biochars and relate these to their long
term stability, effect on soil health and improved crop
yields and reduction in emissions. An overview of the
available literature will be undertaken of chars
produced at temperatures between 400°C and 600°C,
along with a summary of the research carried out at
UNSW. This paper will not review the extensive
research carried out on activated carbon.
2. Characterisation of Feedstocks
Biochar has been produced from a wide range of
biomass feedstocks. For agronomic use these are
characterized by the relative proportion of lignin,
hemicellulose, cellulose, mineral content, protein,
carbohydrate and other extractives and their internal
structure. The relative proportion of these constituents
will influence the final chemical composition and
structure of the char (for a given set of process
Mineral matter in plants forms different functions
and occurs in different forms [4]. Potassium and
chlorine ions are highly mobile and will start to
vaporize at relatively low temperatures during thermal
decomposition. Calcium is mainly located in the cell
walls and the ions are bound to organic acids. Silicon
is bound in the cell walls as silica or as opal phytoliths.
Both are released during pyrolysis at much higher
temperatures than potassium. Magnesium is both
ionically and covalently bonded with organic molecules
and only vaporizes at high temperatures. Phosphorous
and sulphur are associated with complex organic
compounds within the cell and are relatively stable at
low pyrolysis temperatures. Nitrogen is associated with
a number of different organic molecules and can be
* Corresponding author:
Phone: (+61) 0408415477
Email: - 130 -
released at relatively low pyrolysis temperatures. Other
elements such as iron or manganese exist in a number
of organic and inorganic forms in the biomass and are
largely retained during pyrolysis.
Wood and related plants (e.g. bamboo, coconut
shells) are characterized by a very low ash composition
(<3%) and a very open porous structure. When wood is
pyrolysed it maintains its internal cellular structure
(Fig. 1). Animal manures and some other high mineral
ash residues are not very porous but increase their
porosity when pyrolysed. Husks (e.g. rice) can have
both high ash content and high porosity. They will
maintain their structure when pyrolysed.
2. Effect of Process Conditions on the
Properties of Biochars
A range of temperatures, heating rates, time at final
reaction temperature, pressures (1 to 10bar gauge) and
partial pressures of oxygen/steam are used to produce
biochars. The reactions conditions are one of the main
determinants of the yield of biochar and its physical
and chemical composition. Much research is still
required to fully characterize the affect of these
parameters but the following is a summary of findings
to date.
2.1 Properties between 400°C and 600°C
At temperatures near 400°C a cross-linked
amorphous aromatic structure is formed from the
reaction of volatile gases with the unreacted biomass.
This structure is porous and could contain randomly
curved sheets [5]. At the surfaces of the biochar there
are a range of functional groups that include pyranone,
phenolic, carboxylic, lactone and amine groups. Asada
[6] noted that the formation of free radicals in biochar
that is produced at a temperature below 600°C. These
radicals could be associated with aromatic and aliphatic
compounds, especially those that contain nitrogen and
Metals and non metals can be ionically or
covalently bonded with the aromatic compounds.
Mobile atoms such as potassium could be intercalated
in the carbon aromatic structure [7]. In high ash
biochars crystalline and amorphous mineral phases
exist between these aromatic structures. The
distribution of mineral phases is complex and varied
and depends on the structure of the original biomass.
As the temperature increases it is probable that the
composition and the structure of these metallic phases
will change [7]. Further work is required to fully
characterize these changes.
As the temperature increases above 450°C
microcrystalline graphene sheet formation occurs.
Kercher [8] has hypothesized that as the temperature
increases the disordered carbon decomposes and
becomes incorporated into the graphene sheets of the
turbostratic carbon. The rigid covalent structure of the
disordered carbon cannot rearrange during
decomposition to allow the non-uniform growth of
turbostratic crystallites. Instead, some graphene sheets
grow extensively, and other sheets become terminated
and pinned by structural defects [8]. The conversion of
low-density disordered carbon into high-density
graphene sheets causes the volumetric contraction
observed during carbonization. Kercher [8] found that
the graphene sheets had there maximum thickness
around 450°C. It is probable that the micro-crystal
structure and the defect structure of the biochars are
affected by the type, quantity and structure of the
mineral matter. For low ash biochars the electrical
conductivity of the biochar increases as the volume of
graphene sheets increases [9]. Higher mineral ash
biochars probably have higher conductivity especially
those that have high potassium ion contents due to the
mobility of the potassium ions. Further research is
required to determine the affect of mineral content on
the internal structure and electrical conductivity.
Final process temperature determines the average pore
size, the number of micro pores/unit mass and the total
surface area. Sousa [10] found for pinus elliotti biochar
that maximum concentration of pores and minimum
pore diameter occurred around 450°C (around 2µm).
The surface area of wood biochar at 400°C is
approximately 50-100m2/g and at 500°C 300-500m2/g
[11]. The cation exchange capacity (CEC) and pH of
fresh biochar from wood increases as the temperature
of pyrolysis rises [12].
There is a wide range of highly oxygenated volatile
compounds (e.g. levoglucosan,
hydroxyacetaldehyde, furfurals, and methoxyphenols)
that are retained on the surface of the pores of the
biochar at temperatures below 500°C. Some of these
compounds are water soluble. The quantity and
composition of the volatile organic compounds on the
pore surfaces change. At approximately 500°C phenolic
ethers, alkyl phenolics and heterocyclic ethers may be
deposited on the biochar surface [13]. As the
processing temperature increase the percentage of the
different functional groups in the carbon matrix
changes with the carboxylic and carboxylic anhydrides,
and lactones groups decomposing to CO2. In high ash
biochars amine functional groups are converted to
pyridine groups at higher temperatures [14].
Figure 1: Images of char particles under the SEM a)
wood-based char, b) manure-based char.
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The proportion of different functional groups, the
surface porosity and the form of mineral matter changes
when biochars are reacted with oxygen, and/or steam
and/or CO2 at their final pyrolysis temperature. The
reactions of low mineral ash chars to oxidizing
environments should be different to high mineral ash
chars. Koutcheiko [22] measured an increase in the
pyridinic-N and quaternary-N and a decrease in the
amine functional groups and pyrrolic N when chicken
manure biochar was reacted with CO2.
2.2 Effects of Pressure, Particle Size, Time
and Atmosphere
There is very little consistent data on the effects of
the other process variables on the structure and
composition of biochars produced at high heating rates
(>50°C/minute) and/or higher pressure (>2
atmospheres). At high pressures (and in the presence of
steam) porosity can be high and density low due to the
rapid breakdown of the biopolymers [15]. The structure
of the amorphous biochar is different to that found in
pyrolysis carried out atmospheric temperatures in that
there is less cross linkage and a great proportion of
dimers and monomers [15]. Antal [16] notes that the
functional groups are similar for wood biochars made at
both high and low pressures under slower heating rates.
For most particulate wood biochars it appears that high
heating rates result in biochars that are amorphous,
have lower alkaline metal content [17] and that have
low porosity due to the formation of a melt phase [18].
3. Reaction of Biochars with Soils,
Microbes and Plants
There are complex interactions between water
within the pores and on the surface of the biochar, the
soil, plants, and micro-organisms. Sugimoto [23]
suggest that water has an ice like structure in the
nanopores of biochar produced above 400°C. Water is
probably in the supercooled state when adsorbed into
biochars produced above 450°C [24]. Turov [23] noted
that the interactions of water with carbon can be
considered as interactions of clusters or droplets
localized near oxygen containing groups. In those
entities water molecules interact with each other
stronger than with hydrophobic patches of the carbon
surface. Thus the kinetics and the energetics of
reactions that take place at the interface between
biochar and the water will be influenced by the charring
temperature and the distribution of functional groups.
Most biochar has been produced in pit, beehive or
vertical shaft kilns that have residence times ranging
from 24 hours up to 1 month. More recently reactors
have been developed that utilise residues that have a
relatively small particle size (<15mm) and have
reaction times that vary from seconds (for fast
pyrolysis) to 1 hour for slow pyrolysis. Very little
systematic research has been undertaken on the effect
of time and particle size on the composition and
structure of different biochars. Mathematical modeling
indicates that, for a given particle size, the shorter the
process time the greater is the concentration gradient of
carbon and the more volatile minerals across the
particle [19]. It is probable that the microcrystalline
graphene sheets will grow when the biochar is held for
long times at the final reaction temperature [8].
However, this needs to be verified experimentally.
When biochar is applied to wet soil there will be an
almost immediate change in the pH of the soil around
the biochar, increase in the soil porosity, dissolution of
organic and inorganic compounds, an exchange of
cations (and possibly anions) between the clay and silt
particles and the biochar and an adsorption of gases,
metals and other organic compounds on the biochar
Leaching and dissolution experiments ([25,26] indicate
that high ash biochars produced at temperatures below
550°C release potassium, sodium, phosphorous,
sulphur, sulphates inorganic carbonates and organic
compounds into moisture surrounding the biochar
particle. This dissolution may take place within the
first week of placing the biochar in the soil and there
may be an exchange of cations, anions and organic
compounds with the surrounding soil, microbes and
plants. Over a much longer period of time calcium,
magnesium, iron will dissolve out of the biochar. Much
lower concentrations of cations and anions are released
from low ash biochars (especially wood) than high ash
biochar (chicken manure).
There is some evidence to indicate that the residual
bio-oils on char produced from the very slow pyrolysis
of logs and branches have a much greater percentage of
low molecular weight compounds (this was the
conventional method of manufacturing wood alcohol)
[20]. Schnitzer [21] has carried out a detailed analysis
of the residual bio-oils on biochars derived from the
fast pyrolysis of chicken manure. They found that the
individual compounds identified were grouped into the
following six compound classes: (a) N-heterocyclics;
(b) substituted furans; (c) phenol and substituted
phenols; (d) benzene and substituted benzenes; (e)
carbocyclics; and (f) aliphatics. Prominent N-
heterocyclics in bio-oil were methyl-and ethyl-
substituted pyrroles, pyridines, pyrimidine, pyrazines,
and pteridine. The alkanes and alkenes ranged from n-
C7 to n-C18 and C7:1 to C18:1, respectively, and those in
the biochar from n-C7 to n-C19 and C7:1 to C19:1,
Many of the residual bio-oils on the biochar surface are
unstable and can react with water, air and with each
other to form new compounds [28]. Thus organic acids
may react with alcohols to form esters, organic acids
with olefins to form esters, aldehydes and water to form
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- 133 -
hydrates (referred to as glycols), aldehydes and
alcohols to form hemiacetals, aldehydes and proteins to
form dimers of the proteins.
Biochar, when placed in soil, can also adsorb heavy
metals and other dissolved organic compounds [13].
The adsorption processes appear to be complex and
depend on the concentration and distribution of mineral
phases, functional groups, radicals and defects on the
internal pore and external biochar surfaces.
Swiatkowski [14] have postulated that metals can be
absorbed on biochar that has been oxidized via a series
of acid base reactions.
Micro-organisms can start to grow on the surfaces
and in the pores on biochar within the first month of
being applied to soils containing composting material
[29]. The root hairs also penetrate the macropores of
the biochar and take in moisture and nutrients. Biochar
is also ingested by worms and are excreted with
coatings of organic compounds which provide food for
other micro-organisms. Examination of black carbons
in soil has shown that there is considerable interaction
between the clay minerals and the biochar [30]. This
organo-clay layer may reduce weathering of the
biochar. It is possible that binding can take place
through interaction between the clay minerals and the
functional groups on the surface.
4. Conclusions
Biochars produced from biomass are very complex.
Very little systematic analysis of the amorphous and
microcrystalline structure and chemical composition of
biochars produced from different biomass under a
range of process conditions have been undertaken.
There is only a basic understanding of how biochar
structure and composition improve soil fertility, crop
yields, GHG emissions and long term stability in soils.
Over the next 2 years extensive characterisation of
biochars made from high and low mineral ash biomass
under different process conditions will be undertaken
using a range of analytical techniques at UNSW and
Cornell University.
5. Acknowledgement
Funding for this research has been provided by the
Australian Research Council and the Department of
Environment, BESTEnergies Australia Pty Ltd and
Climate Change of the N.S.W. Government and
BESTEnergies Pty.
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... Among these methods, slow pyrolysis is traditional but most widely used method for bio-char production in industrial application. The carbonization stage in slow pyrolysis is under the moderate temperature range, which is usually 400-600 °C [20], so that the moisture and volatilization in biomass are released to form carbonized material [21,22]. The pore structure of carbonized material is small, and the specific surface area is generally below 100 m 2 /g [23], and it does not have excellent adsorption capacity as activated carbon [24]. ...
Full-text available
Using waste biomass to produce high-value activated carbon is an important way for biomass resource utilization. The energy and mass balance during carbonization and steam activation is crucial for the system operation and still not be systematically understood and calculated. In this work, a detailed model for two-step activated carbon production was established based on Aspen Plus. The effect of activation temperature, steam/bio-char ratio, and activation agent on the activation process was investigated. The results show that utilization of the heat duty of combustion of volatiles and sensible heat from flue gas could supply the necessary energy for carbonization, steam generator (boiler), and activation reactors. Steam/bio-char ratio could influence the activation process and the heat balance. The steam/bio-char ratio was controlled as 1–2, which was reasonable for activation carbon production. The increasing heat load provided the higher reaction temperature condition and the sensible heat of syngas. From the point of view of theory and practice, for the production of wooden activated carbon, the activation temperature of 800–900 °C is reasonable. Directly using hot flue gas of volatile combustion as activation agent was energy-saving and benefiting the production of syngas with higher heating value.
... The property of EC indicates a slightly higher salinity in PLB compared to those in SBB and SPB. Furthermore, higher mineral ash in biochar probably has higher electrical conductivity especially those that have high K + ion content as in PLB, due to the mobility of the K + ions (Joseph et al., 2007). As PL biochar is rich in minerals, it may be better suited as an alternative organic fertilizer and can acts as a potential soil amendment. ...
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Biochar produced from biomass with high nutrient content is essential for improving the quality of agricultural soils. An abundance of biomass is converted into biochar with high nutrient content, but studies on the conversion of pineapple and sago waste into biochar are still limited. This research aimed to produce biochar from pineapple leaf (PLB), sago bark (SBB), and sago pith (SPB) through the carbonization process with low temperature. The samples were carbonized using a laboratory electric oven at a low temperature of 350°C. The raw biomass and biochar produced were then subjected to elemental analysis and characterization. The mineral contents of carbonized biochar such as K, N, S, Mg, and Ca increased from those of the feedstock concentrations. For PLP, K element increased 24-fold from 2.44 ± 0.73% to 48.32 ± 9.92%, while N element increased from 6.13 ± 2.39% to 8.33 ± 5.34%. However, for both SBB and SPB, N and K nutrients increased by 2-fold. The study reveals that pineapple leaf biochar has the potentials to be used as an alternative soil amendment to elevate soil nutrient and quality.
... Biochar results from the thermal degradation of organic materials under little or no oxygen (pyrolysis), and is well known for its multiple functions in pollutants adsorption, soil remediation and fertility improvement, and climate change mitigation (Joseph et al., 2007;. The materials used for biochar production are often derived from plant biomass, such as trees and grass, as well as from the byproducts of packing, animal wastes, and construction materials, such as paperboard, paper mill sludge, wood waste, and fill materials (Li et al., 2013;Rajapaksha et al., 2016;. ...
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... Generally, it can be concluded that both the porosity and surface areas for all investigated materials depend on the temperature of conversion and accordingly on the process applied (Liu et al., 2017). Some authors suggest that biomass with a high content of lignin yields biochar with macroporous structures, while biomass with a high content of cellulose such as SBS (20-24%) mainly produces materials with smaller pore structures (Joseph et al., 2007). Additionally, the composition of the feedstock material affects the properties of the obtained product. ...
This work investigates the transport behaviour of selected organophosphorus pesticides, OPPs (chlorpyrifos, CP; chlorpyrifos-methyl, CPM; chlorfenvinphos, CF) through Danube alluvial sediment in the presence of hydrochars and biochars. The investigated hydrochar, obtained at three different temperatures (180 °C, 200 °Cand 220 °C), originated from sugar beet shreds (SBS) and Miscanthus×giganteus (MIS). Results are described by conventional advective-dispersive equation (ADE). Retardation coefficients (Rd) for all OPPs were in the range 6.2–16. Biodegradation was 4.15 and 1.80 for CPM and CP, respectively, while for CF biodegradation did not occur. The addition of carbon rich materials increases retardation of all OPPs in the range from 4 to 18 times depending on the material. Column experiment results indicated that biodegradation of OPPs occurred (up to λ = 13). In order to confirm that biodegradation occurred in the column experiments, we isolated OPPs degrading microorganisms for the first time from the alluvial sediment. A strain capable of degrading CP and CPM was isolated and identified as Bacillus megaterium BD5 based on biochemical properties, MALDI TOF and 16S rRNA analysis (99.54% identity). The results demonstrate that hydrochars, biochars and isolated degrading bacteria may be effective agents for reducing the mobility of or removing OPPs in contaminated soils or sediments.
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Converting feedstock into biochar is a popular approach to overcome the disposal problem, yet the role of waste type and pyrolysis temperature on biochar properties is not understood well. In this study, biochars were produced from various feedstock such as tea waste, apple wood, wheat straw and walnut shell at 300, 400, 500 and 600°C with 1-hour residence time. The results showed that increase in pyrolysis temperature significantly decreased biochar mass yield. The maximum and minimum mass yields were observed in walnut shell at 300˚C and apple-wood-derived biochars at 600˚C by 69 and 20%, respectively. The produced biochar had pH range between 5.3 to 9.7, and its pH value and ash content increased significantly with increasing pyrolysis temperature, except for walnut shell. Total concentrations of P, Ca, K, Na, Fe, Zn, Cu, and Mn and available concentrations of K, Ca, Mg, and P increased with pyrolysis temperature increasing in all samples, except at walnut shell-derived biochar. According to CHN analysis, by increasing pyrolysis temperature, the total carbon concentration increased but total nitrogen and hydrogen concentrations decreased. The pH value decreased with time until 72 hours, beyond which a near steady-state condition was attained. Relationships between pH and CaCO3-eq content of biochars were close and linear. The FT-IR spectra showed that aromatic C increased by increment in heating. Also, by increasing pyrolysis temperature, the mean pore diameter decreased but micropores volume increased and led to increase in the specific surface area of biochars. The results of this study suggest that biochars produced at 300 and 400˚C may have potential as fertilizer in calcareous soils because of low pH and EC, with high mass yield.
... Sorption of metal ions by porous materials is also favored when the material exhibits greater micropore development. Formation of specific pores in biochars is strongly dependent on the chemical composition, i.e., lignin-rich biomass is generally more likely to produce mesoporous structure, while cellulose-rich biomass forms mostly micropores (Joseph et al. 2007). ...
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Chromium removal from aqueous solutions has gained attention due to its hazardous impact on life organisms. In the present study, sorption processes were performed to examine the opportunity to apply biochar derived from waste tomato leaves and stems for Cr(III) ion removal. Biochars were produced through pyrolysis in a wide range of temperature (250–800 °C). The obtained biochars were investigated in detail by means of ultimate and proximate analyses, pH point of zero charge, FT–IR, scanning electron microscopy, and mercury porosimetry. Biochars are characterized by high amount of ash varying from 23 to 44% and as a result high pHpzc values of about 13. It was proven that increasing pyrolysis temperature positively affected sorption of Cr(III) ions. Mineral matter in the biochars plays a crucial role in the removal of Cr(III) ions from aqueous solution mainly due to their precipitation. The sorption capacity of biochar produced at 800 °C was 169.5 mg g−1, whereas at 250 °C only 62.2 mg g−1. It was found that biochar can be reused in sorption process after desorption using 0.1 M HCl, while the sorption capacity decreased 4-fold.
... Biochars also had higher total base cations than feedstocks, which showed that chemical compositions were concentrated in biochars during feedstocks pyrolysis. Joseph et al. (2007) concluded that K + higher contents in ash increased EC of biochar. Moreover, Al-Wabel et al. (2013) attributed biochars pH and ECinduced changes to more release elements due to increase in formation temperature. ...
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The aim of this study was to investigate the impact of incorporating Walnut leaves (WL) and their biochars produced at three temperatures (200, 400, and 600 °C) on fractionation, availability and maize indices in a naturally calcareous highly contaminated soil of Central Iran. A pot experiment was conducted considering soils treated with 0, 0.5, 1, and 2% (w/w) of WL and their derived biochars. After maize (Zea mays L.) planting, shoot and root dry matter and Pb and Zn concentration in shoots and roots and DTPA-extractable and fractions of Zn and Pb in soils were determined. Results showed showed that biochar amendments substantially modified the partitioning of Zn and Pb from easily available forms to less available forms. The results showed that DTPA-extractable of Zn and Pb and their bioaccumulation were reduced upon the addition of biochars produced at different temperatures and application rates in a calcareous soil. Treating soil with 2% biochar produced at 600 °C increased significantly shoot and root dry matter by 131.4% and 116.7%, respectively and reduced the bioavailability of Zn and Pb (DTPA-TEA extraction) by 49.1%, and 34.9%, respectively (P < 0.05) in comparison to the control. Therefore, biochars were able to reduce metals contamination in treatments and increase maize dry matter. Biochar decreased Zn and Pb concentration in plant tissues and promoted gradual maize growth responses through changing metals fractions. Therefore, biochar as a sorbent for contaminants can assist in maize to mitigate and phytostabilize Zn and Pb in highly contaminated soils.
Acute agriculture practice that increases production livable, improves adaptation, diminishes or removes greenhouse gases is the hallmarks of climate smart agriculture.
Environmental degradation due to heavy metals has been studied worldwide due to their non-biodegradable and persistent nature. Among various heavy metals, chromium (VI) (Cr (VI)) and cadmium (Cd (II)) are toxic and enter into aquatic systems from anthropogenic activities. Therefore, considerable efforts have been made for the growth of a well-organized and cost-effective method for the removal of heavy metals. Among various methods, biosorption is cost-effective, environmentally friendly, and readily available. Biochar is porous, carboneous material produced from biomass by thermal decomposition under a limited supply of oxygen at a temperature below 900 ℃. The biomass comprises mainly of 35–50% cellulose, 20–35% hemicellulose, and 10–25% lignin, extractives, and ash. These components are accountable for most of the unique properties of the biochar. Further, the conversion of biomasses into biochar depends upon feedstock, particle size, temperature, reaction time, etc. The biomass with high carbon and lignin content produces biochar with high yield. Biochar has huge affinity for pollutants due to porous arrangement and functional groups such as carboxyl, hydroxyl, and phenolic. Therefore, biochars have been modified with different materials including nanoparticles to improve the removal capacity for pollutants. The sorption efficiency of biochar was found to be improved after modification with nanoparticles. Biochar-based nanocomposite has superior physical and chemical properties that arise due to a combination of advantages of both constituent particles. Thus, the fabrication of biochar based nanomaterials has been reported for the removal of Cd (II) and Cr (VI) from aqueous systems.
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We examined the relationship between the carbonizing temperature of bamboo carbide made from Moso bamboo (Phyllostachys pubescens) and the removal effect of harmful gases and odorants, and the use of a bamboo charcoal as a countermeasure for "Sick Building Syndrome" or "Chemical Sensitivity" and the use as a deodorant. With regard to the carbonizing temperature of the bamboo charcoal, a temperature sensor was installed inside each bamboo material and the carbonizing temperature was controlled at 500, 700 and 1000°C. The removal effect was tested for formaldehyde, toluene and benzene that are known to cause "Sick Building Syndrome" or "Chemical Sensitivity" and for ammonia, indole, skatole and nonenal as odorants. The formaldehyde removal effect was only slightly different in the charcoal at all the carbonizing temperatures. The benzene, toluene, indole, skatole and nonenal removal effect were the highest for the bamboo charcoal carbonized at 1000°C and tended to increase as the carbonizing temperature of the bamboo charcoal increased. The removal effect for ammonia was the highest on the bamboo charcoal carbonized at 500°C. It is concluded that the effective carbonizing temperature is different for each chemical, and a charcoal must be specifically selected for use as an adsorbent or deodorant.
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Physico-chemical properties of a bioorganic char were modified by pyrolysis in the presence of NaOH, and with subsequent physical activation of carbonaceous species with CO2 a value-added activated carbon was fabricated. Bioorganic char is produced as a co-product during the production of bio-fuel from the pyrolysis of chicken litter. Untreated char contains approximately 37 wt% of C and approximately 43-45 wt% of inorganic minerals containing K, Ca, Fe, P, Cu, Mg, and Si. Carbonization and chemical activation of the char at 600 degrees C in the presence of NaOH in forming gas (4% H2 balanced with Ar) produced mainly demineralized activated carbon having BET (Brunauer, Emmett, and Teller) surface area of 486 m2/g and average pore size of 2.8 nm. Further physical activation with CO2 at 800 degrees C for 30 min resulted in activated carbon with BET surface area of 788 m2/g and average pore size of 2.2 nm. The mineral content was 10 wt%. X-ray photoelectron spectroscopy (XPS) indicated that the latter activation process reduced the pyrrolic- and/or pyridonic-N, increased pyridinic-N and formed quaternary-N at the expense of pyrrolic- and/or pyridonic-N found in the untreated char.
Conference Paper
We proposed pyrolysis as a promising optional technology for recycling waste products, especially sewage sludge and animal waste (manure). In this study, nutrient (nitrogen, phosphorous and potassium) leaching characteristics of carbon products mainly from sewage sludge and cattle waste were analyzed. Results are summarized as follows: 1) Electrical conductivity (EC) of carbon product solutes increase with time, and phosphate and sulfuric ions dissolve gradually from the carbon products of both sewage sludge and cattle waste; 2) Nitrogen decreases with manufacturing temperature and nutrient concentration of phosphorous and potassium are larger; Both phosphorous and potassium are citric soluble and easily available for crop production; and 3) The ratio of nitrogen to phosphorous and potassium can be controlled through the manufacturing temperature. These results provide valuable information for utilizing carbon products from waste products.
Recent advances in mathematical modelling and numerical analysis of the pyrolysis of char forming solid fuels have shed new light on the pyrolytic behaviour of these materials under fire conditions. A review of the pyrolysis models of lignocellulosic (wood-based) charring solid fuels developed over the past 60 years is presented in order of increasing complexity. The review, however, is limited to pyrolysis models developed for high temperature and high heating rate conditions and does not encompass the pyrolysis of wood-based materials under conditions pertinent to ‘steam pipe’ type problems encountered typically at low temperatures, low heating rates and relatively long residence times. The models can be broadly categorized into thermal and comprehensive type models. While thermal models predict the conversion of the virgin fuel into products based on a critical pyrolysis criterion and the energy balance, the comprehensive models describe the degradation of the fuel by a chemical kinetic scheme coupled with the conservation equations for the transport of heat and/or mass. A variety of kinetic schemes have been reported in the literature ranging from simple one-step global reactions to semi-global and multi-step reaction mechanisms. There has been much less uniformity in the description of the transport phenomena (i.e. heat and mass) in comprehensive models and different levels of approximation have been used. It is shown that the accuracy of pyrolysis models largely depends on the model parameters. Copyright © 2005 John Wiley & Sons, Ltd.
Laboratory experiments were conducted to examine the effect of charcoal addition on N2O emissions resulting from rewetting of air-dried soil. Rewetting the soil at 73% and 83% of the water-filled pore space (WFPS) caused a N2O emission peak 6 h after the rewetting, and the cumulative N2O emissions throughout the 120-h incubation period were 11 ± 1 and 13 ± 1 mg N m−2, respectively. However, rewetting at 64% WFPS did not cause detectable N2O emissions (−0.016 ± 0.082 mg N m−2), suggesting a severe sensitivity to soil moisture. When the soils were rewetted at 73% and 78% WFPS, the addition of charcoal to soil at 10 wt% supressed the N2O emissions by 89% . In contrast, the addition of the ash from the charcoal did not suppress the N2O emissions from soil rewetted at 73% WFPS. The addition of charcoal also significantly stimulated the N2O emissions from soil rewetted at 83% WFPS compared with the soil without charcoal addition (P < 0.01). Moreover, the addition of KCl and K2SO4 did not show a clear difference in the N2O emission pattern, although Cl− and , which were the major anions in the charcoal, had different effects on N2O-reducing activity. These results indicate that the suppression of N2O emissions by the addition of charcoal may not result in stimulation of the N2O-reducing activity in the soil because of changes in soil chemical properties.
Abstract Common,renewable energy strategies can at best off-set fossil fuel emissions of carbon dioxide, but are not able to reverse climate change. One promising approach of lowering carbon dioxide in the atmosphere while producing energy is bio-char bio-energy based on low-temperature pyrolysis. This bio-energy technology,relies on capturing the off-gases from thermal decomposition of wood or grasses to produce heat, electricity or bio-fuels. Bio-char is a ,significant by-product of this ,pyrolysis with remarkable ,environmental properties. Bio-char in soil was shown,to persist longer and to retain cations better than other forms of soil organic matter. The precise half-life of bio-char is still disputed, however, and will have important implications for the value of the technology including carbon trading. In addition, the cation retention of fresh bio-char is relatively low compared,to aged,bio-char in soil and it is not clear after what period of time,and under
The influence of organics on the structure of water adsorbed on activated carbons was studied using adsorption of nitrogen, benzene, and water, and by (1)H NMR spectroscopy with freezing out of bulk water with the presence of benzene-d(6) or chloroform-d. It was found that interactions of water with the activated carbon surface depend on both structural characteristics (contributions of micro- and mesopores, pore size distributions) of adsorbents and chemical properties (changed by oxidation or reduction) of the adsorbents. Moreover, the interfacial behavior of water is affected by water-insoluble organics such as benzene and chloroform. Changes in the Gibbs free energy of water adsorbed on carbons exposed to air, water, chloroform-d, or benzene-d(6) are related to textural properties of adsorbents and the degree of their oxidation. Since chloroform-d and benzene-d(6) are strongly adsorbed on activated carbons and immiscible with water they replace a significant portion of adsorbed water in micropores, on the walls of mesopores, and in the transport pores of carbons causing changes in the Gibbs free energy and other characteristics of water.
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K. Kercher, C. Dennis, D. Nagle, Carbon 41 (2003), pp.15-27
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M. J. Antal, and M. Grønli, Ind. Eng. Chem. Res. 42: pp. 1619-1640. [17] D. Keown, G. Favas, F. Hayashi., C. Li,Bioresource Technology 96 (2005),pp. 1570–1577
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D. Mohan, D. Gupta, S.K. Srivastava and S. Chander, Colloids Surf.: A. 177 (2001), pp. 169-181