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Pyrolysis temperature and feedstock type used to produce biochar influence the physicochemical properties of the obtained product, which in turn display a range of results when used as soil amendment. From soil carbon (C) seques- tration strategy to nutrient source, biochar is used to enhance soil properties and to improve agricultural production. However, contrasting effects are ob- served from biochar application to soil results from a wide range of biochar’s properties in combination with specific environmental conditions. Therefore, elucidation on the effect of pyrolysis conditions and feedstock type on biochar properties may provide basic information to the understanding of soil and bi- ochar interactions. In this study, biochar was produced from four different agricultural organic residues: Poultry litter, sugarcane straw, rice hull and sawdust pyrolysed at final temperatures of 350 ̊C, 450 ̊C, 550 ̊C and 650 ̊C. The effect of temperature and feedstock type on the variability of physico- chemical properties of biochars was evaluated through measurements of pH, electrical conductivity, cation exchange capacity, macronutrient content, proximate and elemental analyses, Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analyses. Additionally, an incubation trial was carried under controlled conditions to determine the effect of biochar stability on CO2-eq emissions. Results showed that increasing pyrolysis temperature supported biochar stability regardless of feedstock, however, agricultural properties varied widely both as an effect of temperature and feedstock. Ani- mal manure biochar showed higher potential as nutrient source rather than a C sequestration strategy. Improving the knowledge on the influence of pyro- lysis temperature and feedstock type on the final properties of biochar will enable the use of better tailored materials that correspond to the expected re- sults while considering its interactions with environmental conditions.
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Agricultural Sciences, 2017, 8, 914-933
ISSN Online: 2156-8561
ISSN Print: 2156-8553
10.4236/as.2017.89067 Sep. 5, 2017 914 Agricultural Sciences
Effect of Pyrolysis Temperature and
Feedstock Type on Agricultural Properties
and Stability of Biochars
Rafaela Feola Conz1,2, Thalita F. Abbruzzini1, Cristiano A. de Andrade3,
Debora M. B. P. Milori4, Carlos E. P. Cerri1
1Department of Soil Sciences, University of Sao Paulo, Piracicaba, Brazil
2Department of Environmental Systems Sciences, Institute of Agricultural Sciences, Swiss Federal Institute of Technology,
Zurich, Switzerland
3Brazilian Agricultural Research Corporation, Jaguariuna, Brazil
4Brazilian Agricultural Research Corporation, Sao Carlos, Brazil
yrolysis temperature and feedstock type used to produce biochar influence
the physicochemical properties of the
obtained product, which in turn display
a range of results when used as soil amendment. From soil carbon (C) seque
tration strategy to nutrient source, biochar is used to enhance soil properties
and to improve agricultural production. However, contrasting effects are o
served from biochar application to soil results from a wide range of biochar’s
properties in combination with specific environmental conditions. Therefore,
elucidation on the effect of pyrolysis conditions and feedstock type on biochar
properties may provide basic information to the understanding of soil and b
ochar interactions. In this study, biochar was produced from four different
agricultural organic residues: Poultry
litter, sugarcane straw, rice hull and
sawdust pyrolysed at final
temperatures of 350˚C, 450˚C, 550˚C and 650˚C.
The effect of temperature and feedstock type on the variability of physic
chemical properties of biochars was
evaluated through measurements of pH,
electrical conductivity, cation exchange capacity, macronutri
ent content,
proximate and elemental analyses, Fourier transform infrared spectroscopy
(FTIR) and thermogravimetric analyses. Additionally, an incubation trial was
carried under controlled conditions to determine the effect of biochar stability
on CO2-eq emissions. Results showed that increa
sing pyrolysis temperature
supported biochar stability regardless of feedstock, however, agricultural
properties varied widely both as an effect of temperature and feedstock. An
mal manure biochar showed higher potential as nutrient source rather than a
How to cite this paper:
Conz, R.F., Ab-
bruzzini, T
.F., de Andrade, C.A.,
.M.B.P. and Cerri, C.E.P. (2017)
Effect of
Pyrolysis Temperature and Feedstock Type
on Agricultural Properties
and Stability of
Agricultural Sciences
, 914-933.
July 14, 2017
August 31, 2017
September 5, 2017
Copyright © 201
7 by authors and
Research Publishing Inc.
This work is licensed under the Creative
Commons Attribution International
License (CC BY
Open Access
R. F. Conz et al.
10.4236/as.2017.89067 915 Agricultural Sciences
C sequestration strategy. Improving the knowledge on the influence of pyro-
lysis temperature and feedstock type on the final properties of biochar will
enable the use of better tailored materials that correspond to the expected r
sults while considering its interactions with environmental conditions.
Characterization, GHG, C Sequestration, Char, Organic C
1. Introduction
Pyrolysis of organic residues results in a highly stable and carbonaceous material
defined as biochar [1]. Pyrolysis reaction in high temperatures and low oxygen
concentration produces biochar high C content organized in aromatic and stable
structures, defined as fixed C, not available for microorganisms’ degradation [2].
Particularly for wood derived biochars, this accumulation of C and release of less
stable organic compounds, combined with lower feedstock macronutrient con-
tent, produces a highly and stable C containing biochar, ideal for increasing C
content of soil [3] [4]. This supports the use of such biochar as a C sequestration
strategy rather than a nutrient source. Biochar can contribute to the greenhouse
gas (GHG) mitigation not only due to its C sequestration potential [5] but also
displacing the use of fossil fuel, producing alternative energy source through
pyrolysis process [6]. As a global warming mitigation strategy, application of bi-
ochar in soil also showed decreasing N2O emissions. Evidence found in literature
shows more than 14% decrease in N2O emissions in biochar amended soil com-
pared to soil-only [7]. However, results are inconclusive and display variations
and the underlying mechanisms explaining the effect of biochar-soil interaction
include biochar properties and soil biotic and abiotic conditions [8].
Biochar produced from different feedstock type may, however, have varied
concentrations of nutrients of agricultural interest. In this sense, animal manure
derived biochar is shown to accumulate important elements, such as phosphorus
(P), calcium (Ca) and magnesium (Mg) [9] [10]. Thus, animal manure derived
biochar has higher potential to be used as a nutrient source in agricultural sys-
tems [11]. Macronutrients concentration in biochar increase during the pyroly-
sis process while volatile matter and water is released from biochar structure.
These latter compounds are represented by organic acids, and as pyrolysis tem-
perature increases, the release of such molecules and the accumulation of basic
elements such as Ca and Mg are the drivers of high pH in biochars. These prop-
erties support the use of biochar as soil amendment, as liming agent and nu-
trient source [12].
Higher soil aggregation was also observed for fine-textured soil where wood
and animal derived biochar was added [5], improving soil physical structure,
aeration and moisture ratio, consequently an improved environment for root
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10.4236/as.2017.89067 916 Agricultural Sciences
development. These mechanisms are often related to increased agricultural pro-
duction; however, results vary due to biochar properties and its interaction with
different environmental conditions [13].
It is clear that the use of the biochar can vary according to its properties,
which are defined as a function of the origin/type of biomass used and the va-
riables related to the pyrolysis process, such as time and temperature. Several
outcomes are observed from the interaction of biochar and soil particles [14].
These contrasting effects are caused by the various physicochemical properties
of biochar combined with environmental conditions. Thus, elucidation of the
effect of pyrolysis conditions and feedstock type on biochar structure and chem-
ical properties provide basic information to support the understanding of the
resultant interactions of biochar with soil. Moreover, this knowledge also enables
the selection of feedstock type and production conditions according to the envi-
ronmental conditions and desired amendments for particular situations.
The purpose of this study is to present potential uses for biochar in cultivated
soils considering the variation on biochar agricultural properties and C seques-
tration potential, as an effect of pyrolysis temperature and feedstock type. In this
sense, we specifically aim to 1) evaluate the effect of pyrolysis temperature and
feedstock type on relevant agricultural properties and C sequestration potential
of biochar and 2) investigate the effect of contrasting biochar on GHG emission
applied in tropical soil from Brazil.
2. Materials and Methods
2.1. Biochar Feedstock
Selected feedstock comprised contrasting organic residues derived from agricul-
tural production systems: poultry litter, rice hulls, sugar cane straw and sawdust.
Poultry litter (PL) was donated and collected from the poultry facility within
the Department of Genetics at the University of Sao Paulo“Luiz de Queiroz”
College of Agriculture (USP-ESALQ). These poultry are part of a sustainable
farming production project developed in the department, and the posture poul-
try are fed daily with grass. The manure sits on the ground of the facility and it is
mixed with sawdust weekly. Clean rice hull (RH) was collected in the same facil-
ity where the material is used as bedding for broiler.
Sugarcane straw (SC) was collected from a commercial sugarcane field. The
straw was left over the cultivated area after harvesting operation. The Depart-
ment of Forestry Sciences, in the Wood Technology and Management Labora-
tory, at USP-ESALQ, provided sawdust (SD). Pre-treatment included drying at
45˚C for 24 h and ground to less than 1 mm particle size, followed by characte-
rization analysis.
2.2. Biochar Production
Prior to pyrolysis, selected feedstocks were dried at 105˚C to approximately 13%
moisture (w/w) to improve the reactor efficiency. Biochars were pyrolyzed in a
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10.4236/as.2017.89067 917 Agricultural Sciences
60 L static reactor in N2 saturated atmosphere with a heating rate of 10˚C·min−1.
The feedstock was placed individually in the reactor chamber and heated by six
electrical resistances to the temperatures of 350˚C, 450˚C, 550˚C and 650˚C.
Temperature was monitored by three sensors placed in the reactor, reaching its
interior atmosphere close to the chamber. The reaction time varied according to
each run and feedstock, and the completion was reached when the release of
gases from the reactor stopped. The biochars were removed from the chamber
12 h after the reaction time was completed in order to avoid spontaneous com-
bustion. The mass of all materials contained in the chamber reaction was deter-
mined in order to obtain biochar yield (Table 1).
2.3. Feedstock and Biochar Analysis
Feedstocks were analyzed accordingly to the same methodologies used for bio-
char, concerning the determinations of pH, electrical conductivity (EC), cation
exchange capacity (CEC), proximate and elemental analysis. Additionally,
feedstock samples were evaluated in relation to their devolatization characteris-
tics, through thermogravimetry analysis. Grind samples of 9 mg were placed in a
crucible with N2 gas flow with a heating rate of 10˚C·min−1, from 25˚C to 900˚C
(TGA-50, Shimadzu). Weight loss in respect to temperature increase was rec-
After pyrolysis of feedstock, biochars were maintained within plastic bags
tightly sealed. Prior to the analyses, air-dried biochars were ground with mortar
and pestle and sieved to achieve particle size of 150 - 850 µm. Proximate and
elemental analyses as well as pH and EC measurements were performed follow-
ing the methods recommended by the International Biochar Initiative Guideline
[15]. Measurements of pH and EC were performed in 20 ml of deionized water
mixed for 90 min with 1.0 g of sample [16]. pH-meter (Digimed DM-23) and
conductivity-meter (Digimed DM-32) were both previously calibrated with
standard solutions. CEC was determined using 0.5 g of biochar and 1 g of feeds-
tock. Samples were mixed with 100 ml of HCl (0.5 mol·L−1) in an orbital mixer
for 30 min. Samples were filtered in vacuum, while washed with 300 ml of deio-
nized water divided in 10 aliquots of 30 ml each. The residual solution was dis-
carded. Calcium acetate (0.5 mol·L−1, pH = 7.0) was added to the solid sam-
Table 1. Biochar yield after pyrolysis.
Yield (%)
Temperature (˚C)
350 450 550 650
Sugarcane Straw (SC) 41.5 37.6 34.6 32.8
Rice Hull (RH) 49.6 49.2 46.5 46.6
Poultry Litter (PL) 59.6 47.1 42.0 40.2
Sawdust (SD) 42.6 42.4 36.4 33.3
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10.4236/as.2017.89067 918 Agricultural Sciences
ples retained in the filter paper (Whatman 42) in 10 aliquots of 10 ml each. The
washing procedure using deionized water was repeated and the resultant solu-
tion was titrated using NaOH (0.1 mol·L−1) to determine the amount of H+
present in the solution.
Proximate analysis methods were conducted to calculate fixed C content [17]
[18]. Elemental analyses for determination of C, N and H contents were assessed
by dry combustion using a Perkin Elmer CNH 2400; Oxygen (O) content was
obtained by subtraction [19].
The nutrient content was analyzed only for the bio-carbon samples and the
procedure was based on the incineration of the samples in muffle, followed by
suspension in acidic solution and determination by Inductively Coupled Plasma
(ICP OESThermo Scientific iCAP 6300 series). Approximately 200 mg of bio-
char samples were placed in crucibles and ashed in a muffle furnace for 8 h at
500˚C. The samples were transferred to borosilicate tubes and added 5.0 ml of
HNO3, then placed on a digestion bloc to reach temperature of 120˚C. After
evaporation was complete and samples were cooled, 1.0 ml of HNO3 plus 4 ml of
30% H2O2 were added and heated at 120˚C to complete dryness. When cooled,
concentrated 1.43 ml HNO3 was added and vortexed, then deionized water was
added to complete 20 ml. The resultant solution was used for the determination
of total P, K, Mg, S, Ca, Fe, Cu, Mn, B, Zn contents through ICP [20].
Fourier-transform infrared spectroscopy (FTIR) analysis was performed in
feedstock using ground material mixed with KBr in a 1:500 ratio (w/w) and in
biochars with 1:1000. The mixture was compacted at 5 Mg to form pellets of 1.0
cm of diameter. Pellets were analyzed in a spectrometer (Perkin Elmer Spectrum
100) with 4 cm−1 resolution, measuring the absorbance from 400 to 4000 cm1.
Samples were corrected against a pure KBr pellet and the air as background
spectrum [21].
2.4. Incubation Experiment
Following characterization, sugarcane straw (SC) and poultry litter (PL) biochar
produced at 650˚C and 350˚C (SC350, SC650, PL350 and PL650) were selected
to conduct an incubation trial in biochar-treated soils. Based on the results from
the proximate analysis, these biochars presented higher and lower stability
(SC650, PL650 and SC350, PL350 respectively) [9]. This incubation trial was
performed to evaluate whether CO2-eq emission from biochar-treated soil follow
trends according to biochar stability properties.
Additionally, two contrasting tropical soils were selected to investigate the ef-
fect of contrasting soil texture on biochar stability: Quartzipsament and typic
Hapludox (Table 2).
Each soil respectively was collected from two different native vegetation areas
located near Anhembi, Brazil (22˚43'31.1''S and 48˚1'20.2''W) and in Piracicaba,
Brazil (22˚42'5.1''S and 47˚37'45.2''W). The soils were sampled at the 0 - 20 cm
layer, air-dried, homogenized, and sieved to 2 mm. Contrasting biochars were
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10.4236/as.2017.89067 919 Agricultural Sciences
Table 2. Soil properties for incubation experiment.
Soil type Quatzipsamment Hapludox typic
Sand (%) 90 40.6
Silt (%) 2.2 27.7
Clay (%) 7.8 31.7
pH (CaCl2) 4.0 ± 0.1 6.2 ± 0.1
C (%) 0.9 ± 0.1 1.9 ± 0.1
N (%) 0.1 ± 0.1 0.2 ± 0.1
P (mmolc·dm−3) 28.0 ± 1.4 4.0 ± 0.0
S (mmolc·dm−3) 9.5 ± 0.7 5.3 ± 0.6
K (mmolc·dm−3) 4.05 ± 0.1 <0.7
Ca (mmolc·dm−3) 96.5 ± 2.1 5.3 ±0.6
Mg (mmolc·dm−3) 20.0 ± 0.0 <1
Al (mmolc·dm−3) 0.0(1) 5.7 ± 0.6
CEC (mmolc·dm−3) 138.5 ± 2.2 69.0 ± 4.0
(1)Values of 0.0 were near the instrument detection.
applied in each soil. The selected materials were: sugarcane and poultry litter bi-
ochars pyrolysed at 350˚C and 650˚C. Both were added at a dose equivalent to
50 t·ha−1 of C [6] in 100 g of soil into a 500-ml jar with sealed lids and rubber
stopper where the syringe (50 ml) was used to removed gas samples. The sam-
pling was performed every day for the first 10 days and in intervals of 1, 2, 3 and
4 days after the 11th, 27th and 48th day; respectively until 56 days, during an in-
terval of 60 min. Moisture was maintained at 60% WHC and temperature at
25˚C, jars were placed inside an incubator without the lids. After collecting gas
samples, the CO2 and N2O concentrations were measured by gas chromatograph
(SRI 8610, SRI Instruments, Torrance USA) equipped in with an electron cap-
ture detector (ECD) for N2O and a flame ionization detector (FID) for CO2 de-
tection. These results were used to estimate the fluxes calculated using the equa-
tion proposed in [3]. N2O emissions were expressed in “carbon dioxide equiva-
lent”, considering the global warming potential (GWP) of 298 for N2O, com-
pared with the GWP of carbon dioxide [22]. Total GHG (N2O + CO2, in mg·kg−1
soil) emission was represented in terms of carbon dioxide equivalent (CO2-eq).
After incubation period, the mixture soil and biochar were evaluated for pH, EC,
total C and N according to [23]. Briefly, soil samples were dried at 40˚C, ground
to 1 mm sieve and mixed in water at 1:2.5 (w/w), shaken for 5 min and resting
for 1 h, followed by determination of pH with previously calibrated pH-meter
(Digimed DM-23) and soil samples were added in water in proportion of 1:2
(w/w), shaken for 1 hour and resting for 24 hours. The EC was determined with
an EC-meter (Digimed DM-32) previously calibrated. Total C and N were de-
termined in samples dried and sieved to 100 mesh by using an elemental analyz-
er (LECO-CN2000).
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10.4236/as.2017.89067 920 Agricultural Sciences
2.5. Statistical Analysis
The effects of temperature and feedstock type were compared amongst biochars’
properties using a 2-way analysis of variance (ANOVA) in a completely rando-
mized design, with one additional treatment (original biomass). Significant dif-
ferences in the factors were investigated using a Tukey’s test (
< 0.05) to com-
pare biochars produced with different feedstock type, and regression analysis to
evaluate biochar in different pyrolysis temperature. Each biochar, originated
from a single combination of feedstock and temperature, was compared with its
original biomass through Dunett’s test (
< 0.05).
The CO2-eq results obtained in the incubation experiment were submitted to
ANOVA and the mean of each treatment with biochar was compared with the
value of the control treatment (soil only) using Dunnett’s test (
< 0.05). All
analyses were performed using R software.
3. Results and Discussion
3.1. Effects of Feedstock Type and Pyrolysis Temperature on
Biochar Properties
3.1.1. Relevant Agricultural Properties
Chemical analyses assessed in the present study reflected different rates of
transformation for each biochar derived from contrasting feedstock. Electrical
conductivity (EC) results varied with greater influence of the type of material
rather than the pyrolysis temperature (Table 3). Our findings indicated that bi-
ochars can preserve the initial nutrient content, as also reported in [14]. Hence
poultry litter showed the highest EC values since animal derived feedstock
usually contain higher nutrient concentration [24]. In contrast with previous
studies [25] [26] [27] there was no increase in EC when increasing pyrolysis
temperature. Particularly for poultry litter biochars, the decrease in EC corrobo-
rated with literature when compared with its feedstock, which showed much
higher values [28].
Increases in pH have been observed in all pyrolyzed materials and this can be
explained by the effect of the temperature on the release volatile matter com-
posed by acid functional groups and concentrates ash contents consequently
elevating the pH [9]. Nonetheless, pH values followed the trend found in litera-
ture and increased with higher pyrolysis temperature (Table 3) [14] [29] [30],
except for sawdust. Poultry litter biochar exhibited the highest values, corrobo-
rating with the higher amount of basic salts found in its feedstock [31]. Values of
pH in sugarcane straw biochar were similar the data described by [29] between 8
and 10 and reflect the presence of basic elements concentrated in its composi-
tion. Particularly for rice hull, pH results exhibited lower values than what found
in the literature [21] and reasons for that could be due to the different metho-
dologies used to assess this property.
As a function of the loss of acidic functional groups by the action of the pyro-
lysis temperature, it was expected to reduce the CEC [30] [32] in comparison to
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10.4236/as.2017.89067 921 Agricultural Sciences
Table 3. Basic characteristics of biochar and respective feedstock.
Feedstock Temperature of Pyrolysis (˚C)
350 450 550 650
EC (mS·m−1)
SC(1) 1.8 1.2 b(2) 1.4 b 2.0 b*(3) 1.9 b* y = 0.3025 + 0.0027x
(r2 = 0.797;
= 0.0003)
RH 0.8 0.2 a 0.2 a 0.3 a 0.3 a ns(4)
PL 11.4 4.4 c 3.9 c 3.8 c 4.0 c y = 8.4609 − 0.0174x + 1.6 × 10−5x2
(r2 = 0.997;
= 0.0334)
SD 0.4 0.1 a 0.1 a 0.1 a 0.1 a ns
SC 7.8 8.7 d* 8.8 c* 9.1 c* 9.2 c* y = 8.0200 + 0.0018x
(r2 = 0.907;
< 0.0001)
RH 6.1 8.4 c* 8.3 b* 8.7 b* 8.7 b* y = 7.9275 + 0.0012x
(r2 = 0.617;
< 0.0001)
PL 7.3 8.2 b* 9.8 d* 9.8 d* 9.9 d* y = 1.5314 + 0.0404x − 3.5 × 10−5x2
(r2 = 0.931;
< 0.0001)
SD 4.0 7.6 a* 7.0 a* 7.4 a* 7.5 a* y = 11.2748 − 0.0164x − 1.6 × 10−5x2
(r2 = 0.625;
< 0.0001)
CEC (mmolc·kg−1)
SC 190 280 bc 200 c 166 b 169 b y = 878.896 − 2.436x − 0.0021x2
(r2 = 1.00;
= 0.0425)
RH 77 158 a 166 ab 171 b 165 ab ns
PL 597 320 c* 203 c* 106 b* 105 ab* y = 533.6833 − 0.6604x
(r2 = 0.929;
< 0.0001)
SD 303 207 ab 113 a* 86 a* 91 a* y = 901.9854 − 2.8627x − 0.0025x2
(r2 = 0.994;
= 0.0160)
(1)SC = sugarcane straw, RH = rice husk, PL = poultry litter, SD = sawdust. (2)Means followed by the same
letter are not different for biochars in the same pyrolysis temperature by Tukey’s test 5%. (3)Means followed
by an asterisk refer to differences between each biochar and its respective original biomass by Dunnett’s test
5%. (4)Regression analysis was not significant for linear model.
the respective original biomasses and with the increase of the temperature,
which was actually observed for poultry litter and sawdust (Table 3). The in-
verse relationship between CEC and pyrolysis temperature was also observed for
sugar cane straw. The actual values of CEC are similar to values reported in lite-
rature [32], particularly for straw derived biochar, between the ranges of 100 and
230 mmolc·kg−1 and the lowest for wood derived biochars in the range of 13 and
30 mmolc·kg−1. The higher mineral phase found in manure derived biochars
promotes the formation of O-containing functional groups on biochar surface
generating CEC, varying from 292 to 511 mmolc·kg−1 [27], which can be linked
with results from spectroscopic analysis showing the loss of oxygen functional
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10.4236/as.2017.89067 922 Agricultural Sciences
As regards the application of the biochar in the soil, it can be noticed from the
results of Table 3 that lower temperatures provide a higher cation exchange ca-
pacity. Nevertheless, CEC develops with surface oxidation [12], and could po-
tentially support CEC increase after application of biochar in the soil.
The sum of macronutrient content of animal derived biochars was higher
when compared to crop residues and wood derived materials (Table 4). Poultry
Table 4. Macronutrients contents (g·kg−1) in biochars and feedstock samples.
Material Temperature of Pyrolysis (˚C)
350 450 550 650
SC(1) 0.94 b(2) 1.67 c 1.99 c 2.73 c y = −1.0175 + 0.0057x
(r2 = 0.979;
< 0.0001)
RH 0.00(4) a 0.00 a 0.00 a 0.00 a ns(3)
PL 3.72 c 2.13 c 3.51 d 4.28 d y = 15.8519 − 0.0558x + 5.9 × 10−5x2
(r2 = 0.742;
< 0.0001)
SD 1.10 b 1.06 b 1.03 b 1.06 b ns
SC 6.75 c 9.87 c 10.58 c 13.65 c y = −0.4950 + 0.0214x
(r2 = 0.953;
< 0.0001)
RH 0.94 a 0.75 a 0.81 a 0.88 a ns
PL 3.13 b 1.78 b 2.48 b 3.05 b y = 13.7939 − 0.0476x + 4.8 × 10−5x2
(r2 = 0.796;
< 0.0001)
SD 0.25 a 0.25 a 0.26 a 0.27 a ns
SC 2.28 d 3.01 c 3.38 d 3.66 d y = −1.7685 + 0.0154x 1.1 × 10−5x2
(r2 = 0.997;
= 0.0005)
RH 0.22 a 0.18 a 0.19 a 0.21 a ns
PL 1.16 c 0.74 b 1.03 c 1.28 c y = 4.7262 – 0.0162x + 1.7 × 10−5x2
(r2 = 0.838;
< 0.0001)
SD 0.65 b 0.60 b 0.80 b 0.84 b y = 0.3300 + 7.7 × 10−4x
(r2 = 0.756;
= 0.0043)
SC 0.60 c 0.92 d 0.87 d 1.09 d y = 0.1542 + 0.0014x
(r2 = 0.810;
< 0.0001)
RH 0.10 a 0.06 a 0.09 a 0.09 a ns
PL 0.76 d 0.39 c 0.60 c 0.65 c y = 3.1042 − 0.0104x + 1.0 × 10−5x2
(r2 = 0.608;
< 0.0001)
SD 0.29 b 0.26 b 0.26 b 0.26 b ns
(1)SC = sugarcane straw, RH = rice husk, PL = poultry litter, SD = sawdust. (2)Means followed by the same
letter are not different for biochars in the same pyrolysis temperature by Tukeys test 5%. (3)Regression
analysis was not significant for linear and quadratic models. (4)Values of 0.00 were near the instrument de-
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10.4236/as.2017.89067 923 Agricultural Sciences
litter biochar showed the greatest values for macronutrients especially due to
high content of Ca, which explains the higher pH determined for this material
[25]. Contents of P and K found in the present study were lower than other re-
sults found in the literature, which could be due to differences in methodology
to determine concentration of elements, and heterogeneity of poultry litter
feedstock [10] [27]. Even though the concentrations dropped with temperature
increase, poultry litter biochar conserved higher amounts of the analyzed ele-
ments, when compared to the other materials studied, indicating its potential
use as fertilizer [28].
Sugarcane straw biochars showed intermediate concentration of macronu-
trient, and consistent increase in these elements when pyrolysis temperature rose
(Table 4). This material is characterized by higher content of K when compared
to the other macronutrients due to the higher concentration of such element in
its feedstock [29].
By contrast, rice hull and sawdust biochars showed very low concentration of
macronutrients, and little to no variability in the concentration of the elements,
when pyrolysis temperature rose (Table 4). Lower contents of nutrients in plant
straw and wood derived materials when compared to animal manure biochars,
regardless of pyrolysis temperature are showed in literature [30].
Nevertheless, the total amount of macronutrient determined has no relation
to the supply of available nutrients [12] when biochar is added in the soil. Simi-
larly, the initial concentration of nutrients in biochars feedstock did not secured
the concentration in its biochars after the pyrolysis process. Thus, neither feeds-
tock material nor pyrolysis temperature are good indicators of the final nutrient
concentration in the biochars [10].
Micronutrients contents showed little to no variability in relation to tempera-
ture increase, for the majority of biochar samples (Table 5), only differences for
the metallic micronutrients Fe, Mn and Zn.
Sugarcane straw biochar exhibited the highest concentration of micronu-
trients, especially due to the high amount of iron (Fe), that could be explained by
contamination with soil, since the straw was removed from the field and was not
washed before being placed inside the reactor chamber. Other element concen-
trated in sugarcane biochar was manganese (Mn), with linear increase as a func-
tion of temperature, reaching a maximum of 0.11 ppm when pyrolyzed at 650˚C.
Poultry litter exhibited the highest concentration of zinc (Zn) reaching 0.09
ppm, which is reflecting the common addition of Zn as a supplement in poultry
diet [33]. These results represent the potential use of biochars as soil amend-
3.1.2. Stability Indicators
Proximate analysis (Table 6) is an approach to evaluate recalcitrance of bio-
chars, and its components vary mostly between different feedstocks than due to
temperature increase [9]. For instance, large proportions of ash content are ex-
R. F. Conz et al.
10.4236/as.2017.89067 924 Agricultural Sciences
Table 5. Micronutrients contents (mg·kg1) in biochars and feedstock samples.
Material Temperature of Pyrolysis (˚C)
350 450 550 650
SC(1) 10.15 b(2) 5.88 b 6.24 b 3.68 b y = 26.0954 − 0.0615x + 4.3 × 10−5x2
(r2 = 0.869;
< 0.0001)
RH 0.08 a 0.06 a 0.02 a 0.06 a ns(3)
PL 0.44 a 0.34 a 0.45 a 0.56 a ns
SD 0.49 a 0.49 a 0.44 a 0.51 a ns
SC 0.07 b 0.08 b 0.08 c 0.11 c y = 0.0242 + 0.001x
(r2 = 0.778;
< 0.0001)
RH 0.04 a 0.04 a 0.02 a 0.04 a ns
PL 0.05 a 0.04 a 0.05 b 0.07 b y = 0.1939 0.0007x + 10−6x2
(r2 = 0.940;
= 0.0011)
SD 0.05 a 0.04 a 0.05 b 0.06 b y = 0.0267 4.0 × 10−5x
(r2 = 0.720;
< 0.0395)
SC 0.03 a 0.03 bc 0.03 a 0.04 b ns
RH 0.01 a 0.01 a 0.01 a 0.02 a ns
PL 0.09 b 0.05 c 0.08 b 0.08 c y = 0.3421 − 0.0011x + 10−6x2
(r2 = 0.493;
= 0.0001)
SD 0.03 a 0.02 ab 0.01 a 0.02 a ns
(1)SC = sugarcane straw, RH = rice husk, PL = poultry litter, SD = sawdust. (2)Means followed by the same
letter are not different for biochars in the same pyrolysis temperature by Tukeys test 5%. (3)Regression
analysis was not significant for linear and quadratic models.
Table 6. Proximate analysis if biochar and feedstock samples.
Material Temperature of Pyrolysis (˚C)
350 450 550 650
Volatile Matter (%)
SC(1) 90.6 50.1 b(2)* 45.2 b*(3) 44.0 c*
43.8 b* y = 55.8667 − 0.0201x
(r2 = 0.772;
= 0.0010)
RH 77.0 25.8 a* 26.5 a* 24.2 a*
28.0 a* ns(4)
PL 69.7 60.8 c* 46.9 bc* 45.7 c*
42.1 b* y = 139.0231 − 0.3163x + 2.6 × 10−4x2
(r2 = 0.944;
= 0.0002)
SD 93.6 54.0 b* 50.0 c* 35.3 b*
29.1 a* y = 86.8058 − 0.0894x
(r2 = 0.953;
< 0.0001)
Ash (%)
SC 8.5 24.2 b* 16.0 b* 17.0 b*
13.3 b* y = 60.2596 − 0.1447x + 1.1 × 10−4x2
(r2 = 0.848;
= 0.0055)
RH 19.5 40.4 c* 40.5 c* 42.0 c*
42.0 c* ns
R. F. Conz et al.
10.4236/as.2017.89067 925 Agricultural Sciences
PL 29.7 38.2 c* 51.0 d* 50.3 d*
48.8 d* y = −53.5375 + 0.3893x + 3.7 × 10−4x2
(r2 = 0.927;
< 0.0001)
SD 1.2 1.2 a 0.9 a 1.0 a 1.2 a ns
Fixed Carbon (%)
SC 0.0(5) 21.9 b* 35.2 c* 35.2 b*
38.7 c* y = −51.1921 + 0.2976x + 2.5 × 10−4x2
(r2 = 0.915;
= 0.0005)
RH 0.0 31.0 c* 29.5 b* 30.8 b*
27.2 b* ns
PL 0.0 0.0 a 1.0 a 2.8 a 7.5 a* y = −12.6417 + 0.0300x
(r2 = 0.967;
< 0.0001)
SD 0.0 41.5 d* 45.6 d* 60.3 c*
66.5 d* y = 8.5892 − 0.0897x
(r2 = 0.954;
< 0.0001)
(1)SC = sugarcane straw, RH = rice husk, PL = poultry litter, SD = sawdust. (2 )Means followed by the same
letter are not different for biochars in the same pyrolysis temperature by Tukey’s test 5%. (3)Means followed
by an asterisk refer to differences between each biochar and its respective original biomass by Dunnett test
5%. (4)Regression analysis was not significant for linear and quadratic models. (5)Values of 0.00 were near the
instrument detection.
hibited by poultry litter biochar, which corroborates with literature [9]. Animal
derived biochar composition reached approximately 50% of ash content and
between 45% and 60% of volatile matter similar to the results reported by [27]
Larger proportions of ash are found in crop residues than in wood derived
biochar due to higher nutrient concentration on the former feedstock [9]. Values
from 24% to 34% were found for rice straw decreasing with higher temperature
[21] and around 37% were also reported for rice husk biochar produced at
500˚C [32]. For sugarcane straw biochar, ash values found in the literature are
scarce but fall in the range of 11% to 13% increasing with temperature [29].
The unexpected decrease in ash content for this material might be explained
by the volatilization of elements such as P, K and S, which can occur at lower
temperatures as 500˚C [9]. The values reported for sawdust varied from more
than 10% to 1% according to the type of wood and the particle size of the mate-
rials [30] [34] [35]. Ash content increases in higher temperatures, due to the re-
lease of labile components, enhancing the mineral phase proportion. Fixed C is
regarded as the recalcitrant C remaining within biochar composition after ther-
mal degradation caused by pyrolysis [1]. Fixed C content is mostly influenced by
the type of feedstock than by pyrolysis temperature in the production process,
even though all materials showed increase in content of fixed C while tempera-
ture increased [30]. In this sense, the content of fixed C in biochar derived from
wood materials is relatively higher when compared to the different biochars,
particularly when compared to poultry manure (Table 6). The higher ash con-
tent in the feedstock, the less effect of increasing fixed C in higher temperature
[9]. Therefore, wood derived biochars produced at higher temperature have in-
creased potential to sequester C in soil by adding organic C in stable forms.
R. F. Conz et al.
10.4236/as.2017.89067 926 Agricultural Sciences
Increasing pyrolysis temperature decreased the concentration of O and H and
increased C of all materials. This reflects the decrease in surface reactivity and
thus higher stability of biochars. Although C content (Table 7) was initially sim-
ilar among feedstocks, the difference in concentration for each material became
larger after pyrolysis [9].
This is due to the fact that each material accumulates C at different rates with
increasing temperature, and most of plant based biochar show high quantities of
C in relation to other nutrients, which is the opposite trend found in biochars
derived from manures [12]. For instance, poultry litter (30% to 40%) showed
slightly decreasing content with increasing temperature. High ash materials,
such as animal manure biochar, have high inorganic C content bound to carbo-
Table 7. Elemental composition of biochar and feedstock samples.
Material Temperature of Pyrolysis
Feedstock 350˚C 450˚C 550˚C 650˚C
Carbon (%)
SC(1) 42.4 60.1 b(2)* 65.6 c*(3) 67.6 c* 69.4 c* y = 50.8267 + 0.0297x
(r2 = 0.917;
= 0.0001)
RH 36.1 32.8 a 48.6 b* 49.1 b* 49.5 b* y = 71.8981 + 0.4236x + 3.9 × 10−4x2
(r2 = 0.941;
< 0.0001)
PL 30.4 38.1 a* 29.8 a 35.3 a 32.6 a ns(4)
SD 45.6 71.6 c* 72.4 d* 79.8 d* 84.6 d* y = 53.9725 + 0.0463x
(r2 = 0.929;
< 0.0001)
Oxygen (%)
SC 50.5 35.8 b* 30.0 b* 29.2 b* 26.7 b* y = 44.4900 0.0281x
(r2 = 0.892;
= 0.0009)
RH 58.6 66.1 d* 49.4 c* 49.4 c* 49.0 c* y = 79.0567 0.0512x
(r2 = 0.617;
< 0.0001)
PL 62.0 55.9 c 68.5 d* 61.5 d 65.1 d y = 1.0937 + 0.2462x + 2.3 × 10−4x2
(r2 = 0.471;
= 0.0129)
SD 48.4 24.3 a* 22.9 a* 16.6 a* 12.4 a* y = 40.2542 0.0424x
(r2 = 0.951;
< 0.0001)
Hydrogen (%)
SC 6.1 2.4 b* 2.8 a* 2.2 b* 2.5 b* ns
RH 5.1 1.1 a* 2.0 c* 1.5 a* 1.5 a* y = 4.3064 + 0.0237x + 2.3 × 105x2
(r2 = 0.595;
= 0.0043)
PL 4.5 3.4 c* 1.7 a* 1.4 a* 0.9 a* y = 12.9610 0.0383x + 3.1 × 10−5x2
(r2 = 0.953;
= 0.0003)
SD 6.0 3.9 c* 4.1 b* 3.2 c* 2.8 b* y = 5.6183 0.0042x
(r2 = 0.815;
< 0.0001)
(1)SC = sugarcane straw, RH = rice husk, PL = poultry litter, SD = sawdust. (2)Means followed by the same
letter are not different for biochars in the same pyrolysis temperature by Tukey’s test 5%. (3)Means followed
by an asterisk refer to differences between each biochar and its respective original biomass by Dunnett test
5%. (4)Regression analysis was not significant for linear and quadratic models.
R. F. Conz et al.
10.4236/as.2017.89067 927 Agricultural Sciences
nates, which can decrease the C by 24% [9] [36]. Biochars derived from sugar-
cane straw exhibited total C values ranging from 67% to 73% [29] while for rice
hull biochar results varied from 36% to 39% [32]. For wood derived biochars, as
sawdust feedstock, total C content showed largest variation with increasing
temperature, ranging from 51% to 77%. Nitrogen content varied within feeds-
tock, exhibiting highest values for sugarcane straw (1.43%) and poultry litter bi-
ochars (1.46%), and the lowest for sawdust (0.3%) and rice hull biochars
(0.02%). However, contrary to literature [9], N regression analysis was not sig-
nificant for linear and quadratic models, showing no variability with tempera-
ture increase. Hydrogen and oxygen contents decreased in all biochars. This is
an indication of carbonization and aromatization of carbon structures during
pyrolysis reaction, and it is reflected in the lower reactivity of biochars as tem-
perature increases [37].
FTIR spectroscopy results of all biochars exhibited flattening of bands located
between 3200 and 3400 cm−1 with increasing temperature (Figure 1), indicating
less intensity of the O-H stretching due to dehydration [38].
All biochar samples showed decrease in the intensity of the band at 1700 cm−1
after pyrolysis process, which indicates the release of carbonyl and carboxyl or-
ganic groups, and is also associated to CEC reduction. Moreover, FTIR spec-
troscopy showed that with higher temperature the broadening and flattening for
all biochar spectra indicates loss of labile aliphatic compounds [25] and main-
tenance of more recalcitrant compounds, such as aromatic chains. Specifically to
the stretching at 2900 cm−1, all samples showed flattening representing the loss
of aliphatic C-H bond [21]. The pyrolysis of cellulose, hemicellulose and lignin
was indicated by the absence of functional groups, which was more noticeable
for the sugarcane straw and sawdust biochars, around 1030 cm−1 [10] [39].
The three main components of biomass; hemicellulose, cellulose and lignin
have different chemical structures and thus, correspondingly thermal stability
[40]. Thermogravimetric analysis (Figure 2) indicated the thermal decomposi-
Figure 1. FTIR spectra displayed for all treatments of all biochar samples and feedstock.
R. F. Conz et al.
10.4236/as.2017.89067 928 Agricultural Sciences
Figure 2. Results from thermogravimetric analysis in all treatments. TG (%) is the cumu-
lative mass loss in temperature increase, and DTG (dm/dt) is the derivative of the TG
tion behavior of lignocellulosic component for each biomass [39]. In all mate-
rials, the mass loss within the first stage of temperature increased, up to 105˚C,
indicating water release. The peaks observed between temperatures of 200˚C to
300˚C and 300˚C to 400˚C relate to the release of hemicellulose and cellulose,
respectively [34]. Lignin has a much higher molecular weight and during pyroly-
sis it decomposes over a wider range of temperature, contributing for the forma-
tion of condensed aromatic carbon in biochar’s structure [40]. The interval be-
tween 300˚C and 400˚C is the highest for all samples from 20% to 50% mass loss,
the highest value exhibited by sawdust and the lowest by poultry litter. Sugar-
cane straw and rice hull lost about 38% of its mass in the same range of temper-
This corroborates with high cellulose contents in wood materials and low in
animal manure. The cumulative mass loss was the lowest in poultry manure and
rice hull within the temperature range analyzed (from 25˚C to 900˚C), which
was also found by [11] [34].
3.1.3. Biochar Amended Soils and CO2-Eq Emission
In both soil types, the cumulative CO2-eq emissions in sugarcane straw and
poultry litter biochar amended soils presented similar results when each treat-
ment was compared to control (Table 8) excluding poultry litter biochar pyro-
lysed at 350˚C. As shown previously, biochar from poultry litter has higher ash
content and volatile matter in comparison with sugarcane straw biochars in both
pyrolysis temperatures (Table 6).
The higher proportion of volatile matter determined in the poultry litter bio-
char (Table 6) indicates higher amount of easily degradable source of C, enabl-
ing its use by the microorganisms, which in turn cause soil respiration to spike
when comparing to control treatment. In sandy soils, lower initial C content was
incremented, amongst other elements that were also added to the soil with poul-
R. F. Conz et al.
10.4236/as.2017.89067 929 Agricultural Sciences
Table 8. Cumulative CO2-eq emissions, total C and N and EC from clayey soil incubated
with sugarcane and poultry litter biochars pyrolysed at 350˚C and 650˚C.
Feedstock Pyrolysis
CO2 eq
N (%)
C (%)
Typic Hapludox
SC(1) 350˚C 153.94 ± 16.1 0.43 ± 0.01*(1) 5.38 ± 0.04* 134.70 ± 4.12*
650˚C 153.52 ± 24.55 0.40 ± 0.03* 5.40 ± 0.18* 114.30 ± 4.43
PL 350˚C 251.01 ± 43.89* 0.51 ± 0.02* 4.76 ± 0.09* 242.61 ± 19.37*
650 ˚C 163.12 ± 29.62 0.39 ± 0.01* 4.90 ± 0.09* 236.07 ± 18.40*
Control 185.55 ± 35.7 0.29 ± 0.01 2.92 ± 0.06 106.08 ± 19.42
SC 350˚C 163.45 ± 34.94 0.19 ± 0.01* 3.09 ± 0.21* 82.42 ± 2.31*
650˚C 129.82 ± 13.22 0.14 ± 0.03* 2.74 ± 0.06* 94.91 ± 1.40*
PL 350˚C 348.95 ± 47.49* 0.24 ± 0.01* 2.41 ± 0.11* 231.17 ± 11.44*
650˚C 103.05 ± 38.79 0.13 ± 0.01* 2.58 ± 0.14* 253.48 ± 6.87*
Control 136.01 ± 22.81 0.09 ± 0.01 0.74 ± 0.08 28.20 ± 5.16
(1)SC = sugarcane straw, PL = poultry litter. (2)Means followed by an asterisk refer to differences between
each biochar and its respective original biomass by Dunnett test 5%.
try litter biochar application, enabling microbial degradation which reflected in
higher CO2-eq emission. The lower reactivity of sandy soils, demonstrated by
lower CEC (Table 2), is unable to buffer the addition of biochar in the soil [41].
The higher CO2-eq emissions in poultry litter biochar amended soils is also re-
flected in the lower total C determined in the samples at the end of the incuba-
tion period. These aforementioned treatments showed the lowest levels of total
C, indicating that the C added with biochar was metabolized and emitted, while
the higher values, presented by sugarcane straw biochar treated soil corroborate
the persistence of highly stable C structures. As the less recalcitrant material,
poultry litter biochar at 350˚C, was a readily available C and N source for soil
microorganisms to perform mineralization.
4. Conclusions
This study demonstrated how pyrolysis reaction affects biochar properties de-
pending on the temperature range and the feedstock type. During pyrolysis,
contrasting feedstock showed similar trends, such as the increase in pH values,
and the concentration of macronutrients such as P, K, Ca and Mg. The extent of
these trends however, occurred differently. Stability indicators showed same re-
sults, where release of O and H, while accumulation of C were influenced by the
initial contents of such elements in each of the feedstocks.
It is essential to note that agricultural properties, that support the use of bio-
char as nutrient source, were improved in manure derived biochars, while C sta-
R. F. Conz et al.
10.4236/as.2017.89067 930 Agricultural Sciences
bility was lower. Contrastingly, wood derived biochars developed higher stability
and have potential to be applied as C sequestration strategy; however, did not
exhibit properties of agricultural interest. Biochars produced from crop residues
showed intermediary properties and have the potential to fulfill both functions
in soil. Specifically, the use of sugarcane straw biochar as C sequestration strate-
gy is encouraged in this study, considering that CO2-eq emissions of biochar
treated soils were similar to soil-only treatments. Further analysis should be car-
ried to investigate the potential of sugarcane biochar as a nutrient source in
cropping systems.
Overall these results demonstrate the potential of biochar as soil amendment,
the selection of biochar for agricultural purposes or as a C sequestration strategy,
however, must consider the biochar’s chemical properties along with the envi-
ronmental conditions and expected results after application.
We thank the São Paulo Research Foundation (FAPESP) and National Council
for Scientific and Technological Development (CNPq) for financial support, the
Department of Soil Science at the College of Agriculture “Luiz de Queiroz” and
the Center for Nuclear Energy in Agriculture from the University of São Paulo
for providing technical support.
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... Hydrophobic partitioning is one of the main mechanisms involved in pesticide sorption to biochars (Inyang and Dickenson, 2015;Liu et al., 2018;Wang et al., 2016). However, pesticide interactions with the biochar matrix are quite complex, depending on their both physical-chemical attributes (Siedt et al., 2021), such as solubility and ionization constant of the pesticide, hydrophobic/hydrophilic moieties of both pesticide and biochar, as well as other biochar's attributes, such as specific surface area (SSA), oxidation degree, aro maticity, porosity (size and amount), carbon content, and pH (Conz et al., 2017;Egbosiuba et al., 2020;Liu et al., 2018;Mandal et al., 2017a;Sun et al., 2012), which are directly affected by feedstock origin and pyrolysis conditions (Hassan et al., 2020;Novotny et al., 2015). SSA is claimed to be a key biochar factor dictating pesticide retention Mandal et al., 2017a), but pore volume and its geometry also seem to play an essential role (Mandal et al., 2017a;Xiao and Pignatello, 2015). ...
... Scanning electron microscopy (SEM) images (LEO 435VP) were collected by taking transversal sections after gold covering the samples (Sputter SCD 050 Baltec), which were preserved in liquid-N 2 . Further information on biochar manufacturing and attributes is fully detailed in Conz et al. (2017) and summarized in Table S2. ...
Agrowaste biochars [sugarcane straw (SS), rice husk (RH), poultry manure (PM), and sawdust (SW)] were synthesized at different pyrolysis temperatures (350, 450, 550, and 650 °C) to evaluate their potential to retain highly mobile herbicides, such as hexazinone and tebuthiuron that often contaminate water resources around sugarcane plantations. A new low field nuclear magnetic resonance approach based on diffusion in internal magnetic field decay (NMR-DDIF) was successfully used to determine biochar's porosity and specific surface area (SSA) to clear the findings of this work. SSA of pores with diameters >5.0 μm increased with pyrolysis temperatures and seemed to dictate biochar's retention, which was >70% of the applied amounts at 650 °C. These macropores appear to act as main arteries for herbicide intra-particle diffusion into smaller pores, thus enhancing herbicides retention. Biochar granulometry had little, but herbicide aging had a significant effect on sorption, mainly of tebuthiuron. However, soils amended with 10,000 kg ha−1 of the biochars showed low sorption potential. Therefore, higher than usual biochar rates or proper incorporation strategies, i.e., surface incorporation, will be needed to remediate areas contaminated with these highly mobile herbicides, thus precluding their leaching to groundwaters.
... Therefore, a lowering of the biochar yield is expected with the increase in pyrolysis temperature due to the formation of more gaseous products (Lin and Kuo, 2012;Dunnigan et al., 2018). A biochar yield of 24%-40% has been observed previously when sawdust is used as the feedstock (Lin and Kuo, 2012;Hodgson et al., 2016;Feola Conz et al., 2017) and when using paddy husk as feedstock a biochar yield of 25%-50% has been observed (Tripathi et al., 2016;Feola Conz et al., 2017;Dunnigan et al., 2018). In this study, the yields range from 23%-27% and 30%-38% for sawdust and paddy husk feedstocks respectively. ...
... Therefore, a lowering of the biochar yield is expected with the increase in pyrolysis temperature due to the formation of more gaseous products (Lin and Kuo, 2012;Dunnigan et al., 2018). A biochar yield of 24%-40% has been observed previously when sawdust is used as the feedstock (Lin and Kuo, 2012;Hodgson et al., 2016;Feola Conz et al., 2017) and when using paddy husk as feedstock a biochar yield of 25%-50% has been observed (Tripathi et al., 2016;Feola Conz et al., 2017;Dunnigan et al., 2018). In this study, the yields range from 23%-27% and 30%-38% for sawdust and paddy husk feedstocks respectively. ...
Direct flow of untreated stormwater containing Cu, Pb and Zn is of immediate concern to aquatic life in waterways. To date, most biochar used has been synthesized under controlled laboratory conditions using furnaces purged with inert gasses. In this study, the removal of Cu, Pb and Zn using biochar synthesized using paddy husk and sawdust feedstocks has used an industrial scale double chamber downdraft pyrolysis reactor. The effect of pyrolysis temperature and the effect of feedstock in the removal of Cu, Pb and Zn was evaluated by conducting batch adsorption experiments. Synthesized adsorbent materials were characterized using proximate analysis, zero-point charge, scanning electron microscopy, X-ray diffraction and Fourier Transform infrared spectroscopy. The biochar yield was in a lower range compared with the literature attributed to the higher heating rate (50 °C/min) in the pyrolizer. Maximum removal efficiencies were observed when the initial pH was at the value closest, when below the solubility limit for the heavy metals. The paddy husk biochar and sawdust biochar synthesized in the temperature range 350–450 °C and 450–550 °C performed best in the removal of the three heavy metals. Chemisorption was the main mechanism for the removal of the three heavy metals. The maximum adsorption capacities of Cu and Zn were 10.27 and 6.48 mg/g was achieved with paddy husk biochar and a maximum Pb adsorption capacity of 17.57 mg/g was achieved by sawdust biochar. Surface complexation, co-precipitation, p-electron interactions, physical adsorption and surface precipitation were the main mechanisms of removal of the three heavy metals.
... Về mặt lý thuyết, sự gia tăng nhiệt độ nhiệt phân có thể loại bỏ các nhóm chức có tính axit (như các nhóm quinon, chromene và diketone); do đó, biochars có xu hướng kiềm hơn (Mukherjee et al., 2011;Tsai, 2017). pH của than sinh học được sản xuất từ cây thân gỗ (tràm, tre) và lục bình có xu hướng tăng khi nhiệt độ tăng từ 500 o C đến 900 o C (Conz et al., 2017;Loc et al., 2018;Sun et al., 2017 Ở nghiệm thức đối chứng (không có than), nồng độ ban đầu là 1705,57±222,92 µg/L sau thời gian 60 phút, 120 phút, 180 phút và 300 phút đã giảm xuống với nồng độ còn lại lần lượt là 1400,53±58,50 µg/L, 1201,20±344,18 µg/L, 1122,67±162,11 µg/L và 1016,13±8,91 µg/L (Bảng 2). Mặc dù nồng độ chlorpyrifos ethyl có xu hướng giảm theo thời gian nhưng khác biệt không có ý nghĩa thống kê (p>0,05). ...
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Than sinh học trấu được sản xuất ở 500oC, 700oC và 900oC được sử dụng trong nghiên cứu để hấp phụ chlorpyrifos ethyl (CE) trong nước. Ba nghiệm thức than và đối chứng (không than) được bố trí với 3 lần lặp lại. Ở mỗi lần lặp lại, 1 g than được cho vào 200 mL dung dịch CE và lắc ở tốc độ 125 vòng/phút trong 60, 120, 180 và 300 phút. Sau đó, dung dịch được lọc qua giấy lọc rồi trữ để phân tích CE còn lại trong nước bằng phương pháp sắc ký. Kết quả cho thấy than sinh học trấu có khả năng hấp phụ CE nhanh trong 60 phút đầu, sau đó giảm dần và bão hòa ở 120 phút trong điều kiện lắc. Trung bình khả năng hấp phụ CE của than trấu được sản xuất ở 500oC, 700oC và 900oC trong 300 phút lần lượt là 303,4±24,10 µg/g, 328,59±1,47 µg/g và 323,68±3,82 µg/g. Nghiên cứu khả năng hấp phụ của than này đối với một số thuốc khác là cần thiết để đưa ra khả năng ứng dụng của than sinh học trấu trong hấp phụ thuốc bảo vệ thực vật.
... Sugarcane (Saccharum officinarum) straw was pyrolyzed at 450°C to produce the biochar used for us as an organic amendment. The complete details about the production and characterization of this biochar are presented elsewhere (Feola Conz et al., 2017). The contaminated soil was amended with 2.5, 5 and 10% (m:m) of biochar, as studied by Puga et al. (2016). ...
Chemical stabilization is an in-situ remediation that uses amendments to reduce contaminant availability in polluted soils. Rates of phosphate, lime, biochar, and biosolids were evaluated as affecting Pb speciation and mobility in soil samples of a mining area located in Vazante, state of Minas Gerais, Brazil. Chemical and mineralogical characterization, desorption kinetics, sequential extraction, leaching evaluation in columns and speciation using X-ray absorption near edge structure were performed. Pb adsorbed on bentonite and on anglesite were the predominant species in the unamended soil. The treatments with phosphate and lime transformed part of the Pb species to pyromorphite. Conversely, part of Pb species was transformed to Pb adsorbed on citrate in the soil amended with biochar, while PbCl2 was formed in soil samples amended with biosolids. Phosphate and lime increased the Pb extracted in the residual fraction, thus showing that more recalcitrant species, such as pyromorphite, were formed. Biosolids and biochar treatments decreased the Pb in the residual fraction, and the fraction associated to organic matter increased after the addition of biosolids. Phosphate and lime were effective to immobilize Pb and to decrease Pb desorption kinetics, but the organic amendments increased the desorption kinetics of Pb in all rates applied. The soil amended with phosphate decreased the Pb leached in the experiment with leaching columns.
... BC usually comprises stable matter, unstable matter, nutrientrich ash, and moisture. Pyrolyzed feedstock BC accumulates approximately 50% of the C in its original biomass (Conz et al., 2017). The high proportions of aromatic carbon in BC make it recalcitrant to microbial decomposition compared to other uncharred organic matter. ...
Biochar (BC) application has the potential to be integrated into a carbon-trading framework owing to its multiple environmental and economic benefits. Despite the increasing research attention over the past ten years, the mechanisms of BC-induced priming effects on soil organic carbon mineralization and their influencing factors have not been systematically considered. This review aims to document the recent progress in BC research by focusing on (1) how BC-induced priming effects change the soil environment, (2) the factors governing the mechanisms underlying BC amendment effects on soils, and (3) how BC amendments alter soil microbial communities and nutrient dynamics. Here, we carried out a detailed examination of the origins of different biochar, its pyrolysis conditions, and potential interactions with various factors that affect BC characteristics and mechanisms of C mineralization in primed soil. These findings clearly addressed the strong linkage between BC properties and abiotic factors that leads to change the soil microclimate, priming effects, and carbon stabilization. This review offers an overview of a fragmented body of evidence and the current state of understanding to support the application of BC in different soil environments with the aim of sustaining or improving the agricultural crop production.
... In general, water deficit leads to considerable decrease in plant photosynthetic performance (Jaleel et al., 2009). However, application of manure and biochar supply essential macro and micro nutrients to the soil solution and enhance utilization of nutrients by plants, which helps to enhance the photosynthesis performance (Feola Conz et al., 2017), as also observed in our study ( Table 2). The carbon dioxide assimilation, stomatal conductance and finally the chlorophyll content may increase due to the increase in photosynthesis and transpiration rate, and stomatal opening, and decrease in stomatal resistance (Misratia et al., 2013;Seema et al., 2018). ...
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Ecosystem degradation as a result of coal mining is a common phenomenon in various regions of the world, especially in arid and semi-arid zones. The implementation of appropriate revegetation techniques can be considered crucial to restore these degraded areas. In this regard, the additions of spent mushroom compost (SMC) and wood biochar (WB) to infertile and degraded soils have been reported to enhance soil fertility and plant growth under water (W) deficit conditions. However, the combined application of W, SMC and WB to coal mine degraded soils, to promote Althaea rosea growth and facilitate subsequent restoration, has not been explored yet. Hence, in the current study a pot experiment was carried out by growing A. rosea on coal mine spoils to assess the influence of different doses of W, SMC and WB on its morpho-physiological and biochemical growth responses. The results indicated that several plant growth traits like plant height, root length and dry biomass significantly improved with moderate W-SMC-WB doses. In addition, the simultaneous application of W-SMC-WB caused a significant decrease in hydrogen peroxide (H 2 O 2) (by 7-56%), superoxide anion (O 2 •-) (by 14-51%), malondialdehyde (MDA) (by 23-46%) and proline (Pro) contents (by 23-66%), as well as an increase in relative water content (by 10-27%), membrane stability index (by 2-24%), net photosynthesis rate (by 40-99%), total chlorophylls (by 43-113%) and carotenoids (by 31-115%), as compared to the control treatment. The addition of SMC and WB under low-W regime enhanced leaf water use efficiency, and soluble sugar content, also boosting the activity of superoxide dismutase, catalase, peroxidase and ascorbate peroxidase in leaf tissues, thus reducing the oxidative stress, as proved by low levels of H 2 O 2 , O 2 •-, MDA and Pro contents. Finest growth performance under optimum doses of W (60% field capacity), SMC (1.4%) and WB (0.8%) suggest that reveg-etation of A. rosea with the recommended W-SMC-WB doses would be a suitable and eco-friendly approach for ecological restoration in arid degraded areas.
Characterization of the biochar-derived dissolved organic matter (BDOM) is essential to understanding the environmental efficacy of biochar and the behavior of heavy metals. In this study, the binding properties of BDOM derived from different pyrolysis temperatures, wetland plants, and plant organs with Cu was investigated based on a multi-analytical approach. In general, the pyrolysis temperature exhibited a more significant impact on both the spectral characteristics of BDOM and Cu binding behavior than those of the feedstocks. With the pyrolysis temperature increased, the dissolved organic carbon, aromaticity, and fluorescence substance of BDOM decreased and the structure became more condensed. Humic-and tryptophan-like substance was more susceptible to the addition of Cu for BDOM pyrolyzed at 300 ℃ and 500 ℃, respectively. In addition, the more tyrosine-like substance is involved in Cu binding at higher pyrolysis temperature (500 ℃). However, the fluvic-like substance occurred preferentially with Cu than the other fluorophores. Moreover, the higher binding capacity for Cu was exhibited by the humic-like substance and by BDOM derived from the higher pyrolysis temperature and the lower elevation plants with the corresponding average stability constants (log KM) of 5.58, 5.36, and 5.16.
Sustainable soil and crop management are prerequisite to soil quality and food security. Intensive agricultural practices have led to greater soil degradation which have deleterious effects on soil microorganisms and their functions. Biochar is a stable organic amendment rich in C and benefits soils by improving their physical, chemical, and biological properties such as pH, electric conductivity, ion exchange capacity, water-holding capacity, and aggregate structural stability, and these changes in soil properties drive microbial and enzymatic activities and nutrient cycling. Biochar improves soil microbial activities by providing labile C, mineral nutrients, and habitat as microbes readily colonizes biochar surface. Biochar alters soil biological functions by inducing shift in microbial community structure and composition. Biochar also protects soil microbes from deleterious effects of various organic and inorganic pollutants. As the results of beneficial biochar–microbe interactions, biochar enhances the efficiency of various microorganisms such as plant growth–promoting rhizobacteria and phosphorus-solubilizing bacteria which improves crop productivity through multifarious traits. Therefore biochar–microbe interactions can be utilized to improve plant productivity and soil quality through a wide variety of mechanisms.
There has been an increased interest in the production of sustainable biochar in the past years, as biochar show versatile physicochemical properties and therefore can have a wide applicability in diverse fields. Comprehensive studies have been made to characterize biochar produced from various biomass materials, usingdifferent production technologies and under different process conditions. However, research is still lacking in correlating biochar properties needed for certain applications with (i) selection of feedstock, (ii) biochar production process and conditions and (iii) biochar upgrading and modification strategies. To produce biochar with the desired properties, there is a great need to establish and clarify such correlations, which can be used for further proper selection of feedstock, tuning and optimization of the production process and more efficient utilization of biochar. On the other hand, further elucidation of these correlations is also important for biochar-stakeholder and end-users for predicting physiochemical properties of biochar from certain feedstock and production conditions, assessing potential effects of biochar utilization and clearly address needs towards biochar critical properties. This review summarizes a wide range of literature published on the impact of feedstocks and production processes and reactions conditions on the biochar properties. In addition, this review reports and discusses the most important biochar properties required for the different potential applications. Based on this review, knowledge gaps and perspectives for future research have been identified regarding the characterization and production of biochar. This review has also highlighted the importance of assessing performance of biochar for certain applications.
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Purpose The production of Technosols is a sustainable strategy to reuse urban wastes and to regenerate degraded sites. However, little is known regarding the role of the activity of enzymes associated with carbon and nutrients cycling on organic degradation and microbial activity in these soils. Methods A controlled experiment was conducted with Technosols made from construction wastes, wood chips, and compost or compost plus biochar, in order to evaluate their organic matter (OM) degradation potential and functioning through the activity of enzymes and microbial community composition. Results The Technosols had organic carbon contents from 13 to 30 g kg⁻¹, carbon-to-nitrogen ratio from 10 to 20, and available phosphorus from 92 to 376 mg kg⁻¹. The Technosols with biochar and compost had alkaline pH and higher contents of organic carbon and available phosphorus compared to Technosols with compost alone. The mixture of wood chips and compost presented the highest enzyme activities, and might be the most appropriate for Technosol’s production. The mixture of concrete and excavation waste with compost and compost plus biochar displayed a potential for OM decomposition comparable to that of wood chips with compost plus biochar. These results suggest that the bacterial and archaeal fingerprint is similar among the Technosols, although differences are observed in the relative abundances of their taxa. Conclusions Substrate composition affects the processes of OM transformation, microbial biomass activity, and composition. The mixture of wood chips and compost presented the highest enzyme activities during the incubation period, and might be the most appropriate for its application as a Technosol. The mixture of concrete and excavation waste with either compost or compost plus biochar displayed a potential for organic matter decomposition that was comparable to that of the mixture of wood chips with compost plus biochar. The microbial communities in these Technosols are not significantly different yet, but the bioavailability of nutrients derived from the changes in the soil matrix (by adding construction waste and biochar) is influencing soil enzymatic activity.
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We examined the physico-chemical properties of the biochar produced from orange peel, residual wood, and water treatment sludge at different pyrolytic temperatures from 300 to 700'C In the peel biochar (OPB) and wood biochar (RWB), pH and carbon content tended to increase with increasing pyrolytic temperature and were higher than those in the sludge biochar (WSB). The electrical conductivity of the OPB was the highest, while specific surface area of the RWB was the highest among the three types of biochar. The specific surface area was relatively high in any biochar. Any biochar surface displayed by scanningelectron-micrographs revealed many hollow channels and very heterogeneous forms. Unlike the WSB, surface functional groups of the OPB and RWB were similar in intensity and shape. From characteristic results of pH, specific surface area, and functional groups, the biochar derived from orange peel, residual wood, and water treatment sludge may have a possibility to be used as an environmental-cost effective soil amendment and adsorbent.
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The stability and decomposition of biochar are fundamental to understand its persistence in soil, its contribution to carbon (C) sequestration, and thus its role in the global C cycle. Our current knowledge about the degradability of biochar, however, is limited. Using 128 observations of biochar-derived CO2 from 24 studies with stable (13C) and radioactive (14C) carbon isotopes, we meta-analyzed the biochar decomposition in soil and estimated its mean residence time (MRT). The decomposed amount of biochar increased logarithmically with experimental duration, and the decomposition rate decreased with time. The biochar decomposition rate varied significantly with experimental duration, feedstock, pyrolysis temperature, and soil clay content. The MRTs of labile and recalcitrant biochar C pools were estimated to be about 108 days and 556 years with pool sizes of 3% and 97%, respectively. These results show that only a small part of biochar is bioavailable and that the remaining 97% contribute directly to long-term C sequestration in soil. The second database (116 observations from 21 studies) was used to evaluate the priming effects after biochar addition. Biochar slightly retarded the mineralization of soil organic matter (SOM; overall mean: 3.8%, 95% CI=8.1–0.8%) compared to the soil without biochar addition. Significant negative priming was common for studies with a duration shorter than half a year (8.6%), crop-derived biochar (20.3%), fast pyrolysis (18.9%), the lowest pyrolysis temperature (18.5%), and small application amounts (11.9%). In contrast, biochar addition to sandy soils strongly stimulated SOM mineralization by 20.8%. This indicates that biochar stimulates microbial activities especially in soils with low fertility. Furthermore, abiotic and biotic processes, as well as the characteristics of biochar and soils, affecting biochar decomposition are discussed. We conclude that biochar can persist in soils on a centennial scale and that it has a positive effect on SOM dynamics and thus on C sequestration.
Biochar soil amendments are often considered as a soil carbon (C) sequestration strategy that can have beneficial impacts on a range of soil properties and plant production. We investigated the impact of two distinct types of biochar on soil chemical properties, microbial communities, soil aggregation and aggregate-associated C within two California agricultural soils in a laboratory incubation study (60 weeks). Water stable aggregation and associated C were examined via wet-sieving to obtain four aggregate size classes: large macroaggregates (2000-8000 μm), small macroaggregates (250-2000 μm), microaggregates (53-250 μm) and silt and clay fraction (< 53 μm). Biochars enhanced aggregation in the finer textured Yolo soil, with 217% and 126% average increases in mean weight diameter for a softwood biochar (pyrolyzed at 600-700 °C with algal digestate) and a walnut shell biochar gasified at 900 °C), respectively. The increase in aggregate stability was associated with an increase in physically-protected C incorporated into macroaggregates. Both biochars had substantial impacts on microbial community composition in both soils, but only increased microbial biomass in Yolo soil. In the coarser textured Vina soil, neither biochar had an effect on aggregation and the subsequent lack of soil organic matter (SOM) stabilization in macroaggregates was associated with a significant loss of soil C in both biochar treatments over the course of the incubation. Our results suggest that biochar can increase the physical-protection of SOM in Yolo soil by enhancing the proportion of C stored within macroaggregates and thus offers a novel mechanism by which biochar may contribute to soil C sequestration. Better understanding of these drivers and identifying soil conditions that determine whether biochar will physically protect SOM vs. stimulate soil C loss must be considered in managing agroecosystems for both mitigation of, and adaptation to, climate change.
Pyrogenic carbon (C) is produced by incomplete combustion of fuels including organic matter (OM). Certain ranges in the combustion continuum are termed ‘black carbon' (BC). Because of its assumed persistence, surface soils in large parts of the world contain BC with up to 80% of surface soil organic C (SOC) stocks and up to 32% of subsoil SOC in agricultural soils consisting of BC. High SOC stocks and high levels of soil fertility in some ancient soils containing charcoal (e.g., terra preta de Índio) have recently been used as strategies for soil applications of biochar, an engineered BC material similar to charcoal but with the purposeful use as a soil conditioner (1) to mitigate increases in atmospheric carbon dioxide (CO2) by SOC sequestration and (2) to enhance soil fertility. However, effects of biochar on soils and crop productivity cannot be generalized as they are biochar-, plant- and site-specific. For example, the largest potential increases in crop yields were reported in areas with highly weathered soils, such as those characterizing much of the humid tropics. Soils of high inherent fertility, characterizing much of the world's important agricultural areas, appear to be less likely to benefit from biochar. It has been hypothesized that both liming and aggregating/moistening effects of biochar improved crop productivity. Meta-analyses of biochar effects on SOC sequestration have not yet been reported. To effectively mitigate climate change by SOC sequestration, a net removal of C and storage in soil relative to atmospheric CO2 must occur and persist for several hundred years to a few millennia. At deeper soil depths, SOC is characterized by long turnover times, enhanced stabilization, and less vulnerability to loss by decomposition and erosion. In fact, some studies have reported preferential long-term accumulation of BC at deeper depths. Thus, it is hypothesized that surface applied biochar-C (1) must be translocated to subsoil layers and (2) result in deepening of SOC distribution for a notable contribution to climate change mitigation. Detailed studies are needed to understand how surface-applied biochar can move to deeper soil depths, and how its application affects organic C input to deeper soil depths. Based on this knowledge, biochar systems for climate change mitigation through SOC sequestration can be designed. It is critically important to identify mechanisms underlying the sometimes observed negative effects of biochar application on biomass, yield and SOC as biochar may persist in soils for long periods of time as well as the impacts on downstream environments and the net climate impact when biochar particles become airborne.
Biochar has been increasingly used as a method for C sequestration and soil improvement. To understand how feedstock and pyrolysis conditions affect biochar characteristics, we investigated two wood-based biochars (bamboo and elm) and five crop-residue-based biochars (wheat straw, rice straw, maize straw, rice husk, and coconut shell), which were pyrolyzed at 500 or 700 °C and remained at that temperature for 4, 8, and 16 h under oxygen-limited conditions. For a given feedstock, increasing pyrolysis temperature from 500 to 700 °C resulted in increases in ash content, BET surface area, pH, and total P and Ca contents (P < 0.05) and decreases in yield, cation exchange capacity (CEC), total acid, and total N (P < 0.01). Prolonging residence time (from 4 to 8 or 16 h), the BET surface area and ash content of biochars increased (P < 0.05), whereas the yield decreased (P < 0.01). Fourier-transform infrared spectroscopy (FTIR) analysis showed that more recalcitrant and aromatic structures were formed in the biochars with increased temperature. The three straw-based biochars consistently exhibited far greater ash percentage (14.5–40.3 wt %), CEC (14.1–34.8 cmol kg–1), and the contents of total N (0.24–2.81 wt %), P (0.60–8.41 wt %), Ca (0.63–1.48 wt %), and Mg (0.24–0.63 wt %) and generally had higher yield (19.0–37.6 wt %), pH (9.2–11.1), and contents of total acid (0.15–0.53 mmol g–1), C (41.7–55.1 wt %), Na (0.27–6.72 wt %), and K (6.56–28.1 wt %) than the two wood-based biochars. The BET surface area of straw-based biochars with 700 °C pyrolysis temperature could be mostly as high as 112–378 m2 g–1, a comparable level with that of wood-based biochars. Despite the high variability in biochar properties, these results demonstrate that biochars from crop straw may be more effective and desirable for improving soil fertility and C sequestration in Chinese vast soils.