Characterization of Biochar Produced from
Different Feed Stocks for Waste Management
Dereje Dejene1* and Eyob Tilahun2
1Department of Natural Resource Management, Wolkite University, Ethiopia
2Department of Natural Resource Management, Debre Tabor University, Ethiopia
Submission: July 21, 2019;; Published: July 19, 2019
*Corresponding author: Dereje Dejene, Department of Natural Resource Management, Wolkite University, Ethiopia
How to cite this article: Dereje Dejene, Eyob Tilahun. Characterization of Biochar Produced from Different Feed Stocks for Waste Management. Int J Environ Sci Nat Res. 2019; 20(3): 556040. DOI:10.19080/IJESNR.2019.20.556040
The objective of this study was to characterize the biochar produced from different agricultural wastes to explore its potential use as organic soil amendments. The feedstock of Eucalyptus globules (EG), Acacia decarance (AD), farmyard manure (FYM) and rice straw (RS) were collected and biochar was produced by slow pyrolysis at 300oC in the furnace. The biochar chemical composition was determined using standard laboratory procedure. Characterization of biochar mainly focused on chemical properties (pH, carbon, phosphorus, cation exchange capacity, electrical conductivity, exchangeable basic cations). Higher carbon content was observed in biochar produced from AD (65.00%) compared with that of biochar produced from other feedstock type included in this study. pH value of Biochar produced from EG and RS showed moderately acidic (pH 5.94) and neutral (pH 6.6), respectively, whereas biochar produced from AD (pH 8.07 and FYM (pH 8.17) revealed moderately alkaline pH level. High and low EC values were recorded in biochar produced from FYM (4.70DS m-1) and EG (0.68DS m-1), respectively. The maximum concentration of exchangeable magnesium (20.95%), potassium (16.40%) and sodium (1.77%), EC and phosphorous (2288.75ppm) were testimony in biochar produced from FYM but calcium (39.50%) was from biochar produced from AD. Higher CEC(129.75cmolckg-1) was detected in biochar produced from EG followed by biochar produced from RS (127.5cmolc kg-1), AD (117cmolc kg-1), FYM (87.25cmolc kg-1). Generally, the current finding revealed that biochar from different feedstocks had different chemical properties, so this difference could contribute for soil fertility improvement as the result agricultural wastes is managed without pollution. But the current work was limited to the characterization of biochar. So, more detailed investigation on the rate and reclaiming the power of the biochar and other issues should be investigated.
Keywords: Biochar; Chemical characterization; Feedstock type; Agricultural waste management
Conversion of agricultural wastes into Biochar is not only save natural resources, but also protects environmental pollution. Varies study of biochar effects in different soil substrates have been scientifically examined during the last decade and most of those findings proved positive effects on plant growth and soil properties . Biochar has gotten high attention because of its potential use in many aspects like a soil amendment to improve soil quality , sequester carbon [3-6], inhibited loss of nitrogenous fertilizer, because biochar act as slow release fertilizer encapsulated  and filter potentially hazardous chemicals due to its strong sorption capacity to many contaminants .
Biochar from many sources of feedstock can be produced through the pyrolysis process in the absence of oxygen. Pyrolysis undergoes a variety of physical, chemical and molecular changes. volatilization during pyrolysis causes a significant loss in mass and therefore volume reduction and shrinking without
causing much change in the original structure of the feedstock . In addition, pyrolysis affects chemical properties of biochar like cation exchange capacity (CEC), pH and carbon content of biochar . Biochar quality and quantity is mainly influenced by its feedstock type as well as pyrolysis condition . Pyrolysis alters the nutrient content in the resulting biochar, which affects nutrient uptake by plants .
Several studies have been carried out to investigate the impacts of pyrolysis temperature on structural characteristics of biochar, sorption affinities to metals and physicochemical properties of different feedstocks . However, the information concerning chemical properties of biochar produced from Eucalyptus globules, Acacia decarance, farmyard manure, and rice straw are limited. In other hand burning of crop residues in the field is a common practice during land preparation and disposal of waste like Eucalyptus globules and Acacia decrance trees have been used in the study area for charcoal production. During this production processes leaves, and branches of the trees were imprudently disposed and burned. These practices
have been causing for environmental pollution and contribute to
greenhouse gas emission to the atmosphere. Conversion of crop
residue, eucalyptus and acacia tree byproduct biomass to biochar
can be an alternative and sustainable way of waste management.
However, information on the characteristics of biochar from this
feedstock type was not studied. Therefore, the objective of this
work was aimed to characterize biochar produced from different
feedstocks based on chemical properties.
The Eucalyptus and Acacia leave were collected from local
charcoal production left over, farmyard manure from Debre
Tabor University Tana-Guna Integrated Field Research Center
and Rice straw from Fogera National rice research center. The
feedstocks were kept in laboratory for air drying and the dried
feedstocks were chopped with the help of clean knife. The
prepared feedstock was placed in a ceramic crucible with a lid
and then pyrolyzed in a furnace with the temperature rising
to 300oC at a rate of 10oC/m and maintained at the highest
temperature for 2 hours and then followed by cooling to room
temperature inside the furnace. Afterward, the Biochar sample
was grounded and passes through a 2mm mesh sieve and then
transported to Bihar Dar Regional soil fertility improvement
laboratory. Composite biochar samples from each biochar
produced from different feedstock were prepared and analyzed
for selected chemical properties.
The pH of a biochar was determined in water at 1:2.5 biochar
to water ratio . Electrical conductivity was measured by a
conductivity meter on standard biochar paste extracts obtained
by Appling suction . Organic carbon of the biochar was
determined by following the wet digestion method as described
by . The available phosphorus was determined using the
standard Olsen extraction method . The exchangeable bases
(Calcium, Magnesium, Potassium and Sodium) in the biochar
were determined from the leachate of 1 molar ammonium
acetate (NH4OAc) solution at pH 7. Exchangeable Ca and Mg
were measured by atomic absorption spectrophotometer and, K
and Na was read using flame photometer as outlined by .
Cation exchange capacity was determined at a soil pH level of
7 after displacement by using normal ammonium acetate with
titrimetrically by distillation of ammonium that was displaced
by sodium .
Statistical analyses were performed with the SAS statistical
software version 9.2 software. The pH, EC, CEC, Ca, Na, Mg, K
and P values were analyzed using one-way analysis of variance
(p<0.05) and non-significant (p>0.05), were determined using
the LSD test.
The current study showed that presence of significant
difference in biochar yield production potential at (p<0.05).
Those different feedstock types have different biochar yield
production potential. The Higher biochar yield potential was
recorded in AD (25.64%) followed by FYM (21.55%), EG
(21.26%) and RS (9.67) (Table 1). The possible reason for the
difference in biochar yield production potential could be due
to difference in lignin, cellulose and hemicelluloses content
difference in feedstock. Similar finding is reported by . In the
other hand, lignocellulosic based biochar tends to have higher
fixed carbon content than manure-based biochar .
The highest pH was recorded in the biochar produced
from FYM (8.17) followed by AD (8.07), rice straw (6.40) and
EG (5.94). Biochar produced from FYM and Acacia decrance
showed moderately alkaline pH level, but biochar produced
from rice straw and Eucalyptus globules indicated moderately
acidic pH level. Generally, pH value of Biochar produced from
different feedstock has significant difference at (p<0.05) (Table
2). Variability of pH value in between biochar produced from
different feedstock type, but the pyrolysis temperature was same
for all feedstock type, so that the biochar reaction difference is
due to ash content difference in resulting biochar. This finding
agrees with that of Ronsse et al. . Higher pH values contain
higher ash contents and their ash fraction contains more
elements suitable for plant nutrients [23,24].
Biochar produced from different feedstock have significantly
influenced by different (p<0.05) in its electrical conductivity
(Table 2). The highest electrical conductivity value was obtained
from FYM biochar (4.70) and the lowest one was biochar
produced from Eucalyptus globules (0.68). A possible reason for the highest EC value of biochar could be due to an increase of
high soluble and exchangeable base cations as outlined by .
Maximum total carbon was produced from AD (65.50%)
followed by rice straw (40.90), EG (37.25) and FYM (23.25%).
Biochar produced from different feedstock have significant
influence at (p<0.05) within its total carbon (Table 2). Biochar
produced from manure feedstocks tend to have lower C content
than lignocellulosic based feedstocks, because manure-based
biochar’s are related to the feedstock containing more volatile
organic carbon compounds that are lost during the dry and
carbonation processes .
As presented in Table 3, there were significant difference at
(p<0.05) between feedstocks on exchangeable basic cations. FYM
biochar contained the highest Na, K and Mg content (1.77, 16.40
and 20.95%, respectively), while the highest Ca (39.50) was
found in AD Biochar. Nevertheless, EG and RS biochar presented
the lowest contents of Na, K, Ca and Mg (1.10, 4.38, 15.05 and
13.00%). The higher content of exchangeable basic cations in
AD and farmyard manure biochar indicated that the relevant
chemical components were concentrated in biochar during the
pyrolysis of feedstock as explained by . High calcium content
is likely connected with the bioconversion of organic matter into
Biochar causing an expected release of compounds as Ca that
reacts with carbonate or phosphate and precipitates .
Maximum concentration of P was observed at biochar
produced from farmyard manure (2288.75ppm) followed by
rice straw (1761.50), Acacia decrance (381ppm) and Eucalyptus
(339.9ppm) (Table 2). High content of P in the biochar could be
due to the charring of organic materials that can highly enhance P
availability from plant tissue by disproportionately volatilizing C
and by cleaving organic P bonds, resulting in a residue with high
soluble P salts associated with the charred material as outlined
(Knoepp et al. 2005). The amount of phosphorus produced from
different feedstock explained significant difference at (p<0.05)
As presented in Table 3, the cation exchange capacity of a
biochar produced from eucalyptus (129.75cmolc kg-1) and rice
straw (127.50cmolc kg-1) showed statistically non-significant
difference. But lower value and statistically significance
difference in biochar produced from FYM (87.25cmolc kg-1) was
observed. The analysis result of biochar revealed that biochar
produced from eucalyptus had high nutrient retention and water
adsorption capacity followed by rice straw, Acacia and FYM in
addition to the direct supply of nutrients as CEC values indicated.
Relatively high CEC value in biochar produced from eucalyptus
and rice straw could be due to high oxygen-containing functional
The characterizations of biochar from different feedstock
were explored by using the chemical properties of the biochar.
Biochar produced from the pyrolysis of four feedstock sample
at 300oC had a different biochar yield and chemical properties.
The chemical variability of a biochar could have a positive
contribution on soil conditioning, specifically biochar produced
from farmyard manure and Acacia decrance may have potential
to acid soil reclamation. However, the environmental pollution
and ecological disturbance caused by residue disposal and
burring cannot be ignored, because continuous disposable and
burning agricultural wastes cause environmental pollution
and contribute for greenhouse gas emission. The current study
was limited to characterization. So, the rate determination and reclaiming powers of the biochar produced from different
feedstock should be further studied.
The researchers would like to acknowledge Debre Tabor
University for providing the financial support. The authors
also would like to thank Mr. Antanh Abewa for the professional
assistance during proposal development. Authors’ deep
gratitude and appreciation extends to the Bahar Dar soil fertility
improvement, laboratory technicians for their tremendous help
in laboratory analysis of the soil samples.