PHYSICO-CHEMICAL CHARACTERISATION OF CARBONISED …jestec.taylors.edu.my/Vol 14 issue 1 February 2019/14_1_02.pdf · residue points were located using GPS hand held device (Garmin

Journal of Engineering Science and Technology Vol. 14, No. 1 (2019) 012 - 026 © School of Engineering, Taylor’s University

12

PHYSICO-CHEMICAL CHARACTERISATION OF CARBONISED ORCHARD RESIDUES AND POTENTIAL

FOR IN SITU RE-UTILISATION: A CASE STUDY AT PULAU TEKAK BESAR, TASIK KENYIR

MOHAMMAD HARIZ A. R.*, MUHAMAD RADZALI M., NOOR SARINAH M. N., NUR ALYANI S., HASLIANA K.

Agrobiodiversity and Environment Research Center, Malaysian Agricultural

Research and Development Institute, P.O. Box 12301, 50774 Kuala Lumpur, Malaysia

*Corresponding Author: [email protected]

Abstract

Waste generated from plant pruning and cutting can be one of the major issues in

the development of new orchard area. This was also the challenge when new

orchard is developed in Pulau Tekak Besar, Tasik Kenyir, Terengganu, Malaysia.

In order to manage the waste rapidly, method of pyrolysis was selected to recycle

and re-utilise the abundance of plant biomass waste. A study was carried out to

evaluate the suitability of the system for field practice. Initial inventory obtained

biomass quantity of 1206 kg (d.w) from 18 point locations covering an area of

0.2267 hectare. The biomass was subsequently chopped and carbonised using a

conventional vertical kiln pyrolysis system. The total amount of final carbonised

product was 381.9 kg (d.w) with recovery average of 31.7% (w w-1 d.w). Further

characterisations identified that product from 8 points fulfil one of the important

criteria of biochar which is to have carbon contents of more than 50% while the

remaining can be described as pyrogenic carbonaceous material (PCM). Cation

exchange capacity (CEC) showed value of the carbonised materials are mostly

between 10.0 to 20.0 cmol kg-1, which is within the range of the soil CEC in the

area (7.4 to 21.0 cmol kg-1). The pH was alkaline ranging from 7.9 to 10.0, which

can be good sources to stabilise acidic soil of newly introduced plants in the area.

Overall study indicated suitability of the carbonised materials for in-situ

reutilisation, particularly with appropriate integration in soils. Further researches

are required to study the application rate and effectiveness in improving plant

growth and nutrient uptake.

Keywords: Pyrolysis, Waste inventory, Biochar, Pyrogenic-carbonaceous-

material (PCM).

Physico-Chemical Characterisation of Carbonised Orchard Residues and . . . . 13

Journal of Engineering Science and Technology February 2019, Vol. 14(1)

1. Introduction

Pulau Tekak Besar in Tasik Kenyir, Terengganu, Malaysia was developed as part

of an eco-tourism project under the commercial name of Kenyir Tropical Park

(KTP). It is an integrated orchard farm planted with multiple rare fruit species

covering an area of approximately 5.3 hectares. The development concept was

similar to forest farming system in which selected rare fruit species were cultivated

within the existing forest system. Preservation of the natural forest is the main

reason for such concept to be implemented. It offers sustainability by increasing

plant species diversity while maintaining land development activities at very

minimal level. Apart of Pulau Tekak Besar, KTP also covers Pulau Sungai Tekak

with a combined area of approximately 10 hectares.

The diversity of plant species has made KTP an attractive eco-tourism

destination. Inventory and surveys conducted have identified 43 species of plants

from 17 families naturally originating from the area [1]. There were in total another

76 species of rare fruits introduced from the families of Anacardiaceae, Clusiaceae,

Phyllanthaceae, Malvaceae, Euphorbiaceae and Sapindaceae making the islands

rich in plant diversity. In view of this, a systematic management approach is

required for the purpose of effective preservation and conservation of the area.

Biomass residue management is one of the important components in orchard

management and maintenance. It involves planning and pursuing an acceptable

method for reutilisation, recycling and disposal. The management strategy has

similar hierarchical approach to agricultural waste management. The process flow

followed standard methods of waste generation, collection, treatment and

utilisation [2]. The advancement of technology today has included the use of

geographical information system (GIS) as part of an effective waste management

system approach [3]. This is to ensure proper allocation and reallocation of the

biomass waste. GIS integrates the use of spatial data with non-spatial data [4],

including quantitative and qualitative aspects of data analysis [5].

During the development phase, large amounts of residues consisting of plant

pruning, branches and decayed woody materials were generated from the area.

These residues were arranged in piles at specific locations and points within the

park to be disposed. Residues such as plant pruning and degraded wood waste

present a problem to the environment if improperly managed. It can be a major

source of pollution if contacts with water causing eutrophication, a phenomenon of

high biological and chemical oxygen demand [6]. Pulau Tekak Besar is basically a

man-made island surrounded by water body. Therefore, there is high probability of

phenomena such as eutrophication to occur. In other aspects, degraded woods also

may become a target of pest and disease. Insects such as termites and beetles attack

woods for shelter and foods [7]. Meanwhile, development of molds, decay and

stains may also occur which are caused by fungi, which grow suitably on mild

temperature and moisture [8].

In order to effectively manage the waste, a rapid and effective method of

pyrolysis was applied. It is a thermochemical process [9] in which organic materials

decompose at high temperature in absence or near absence of oxygen [10]. Under

this process, the biomass waste is pyrolised to form carbonised solid, liquid and

gaseous end products. Among other options such as composting and natural

degradation, pyrolysis was selected due to its effectiveness for short-term

processing time and ability to destroy diseases.

14 Mohammad Hariz A. R. et al.


Current technology available for a low cost pyrolysis includes a vertical drum-

kiln production unit [11]. The process is a bottom-up approach with ignition of

biomass begins at the bottom of the drum. It is useful for small scale and portable

application [12]. In Malaysia, drum kiln technology is widely used in coconut

charring process. This conventional technique is popular for coconut charcoal

producer in Teluk Intan, Perak. The pyrolysation technique, however, might be

slightly different in terms of its process compared to other countries.

The solid carbonised end product from pyrolysis can be characterised based on

certain criteria. As described in European Biochar Certificate [13], it can be

classified as either biochar or pyrogenic carbonaceous material (PCM), subject to

characteristics such as total carbon content, which must be more than 50%.

Although not being classified as biochar, PCM has similar carbonised features,

which are also suitable for use as soil conditioner. It can improve soil structure and

increase recalcitrant organic C in soil [14].

The challenge in managing orchard waste requires the introduction of new low cost

and rapid technique for processing of biomass waste. Other factors that are important

include logistics and practicality. There is also a need to evaluate the quality and

quantity of the products of processed waste biomass for potential reutilisation.

Carbonisation through pyrolysis is suggested since it fulfils all these criteria.

This paper evaluates a case study on the inventory of waste generation and

carbonisation from 18 selected locations in Pulau Tekak Besar, Tasik Kenyir, and

Terengganu, Malaysia. Characterisation of raw materials and carbonised products

were conducted based on physical and chemical attributes. Also discussed is the

potential use for in-situ application.

2. Materials and Methods

2.1. Waste collection and locations

The island of Pulau Tekak Besar is located in the north of Tasik Kenyir,

Terengganu, Malaysia (50 10’ 07”U and 1020 44’ 16”T) [15]. During waste

inventory conducted from January to June 2014, there were 69 orchard residue

and waste locations within the island. Standard method to identify the specific

plant species of the orchard wastes include analysis of the leaf type as one of the

parameters for identification. Since there are difficulties due to degraded leaf and

other small plant parts, GPS point characterisations were carried out. These

residue points were located using GPS hand held device (Garmin Rino®

530HCx). Each of the residue point was eventually plotted into map using

software Arc-GIS ver 10. In order to manage the waste effectively, the residue

locations were divided into 6 different zones (Fig. 1). In this study, 18 locations

of waste covering an area of 0.2267 hectare located at zone 5 and 6 were selected

for assessment and characterisation.

2.2. Inventory of waste

Amount of waste generated was being assessed at each point location. The residues

were chopped into small pieces and the total weight was determined. Samples were

collected for physico-chemical and moisture analysis.



2.3. Biochar production

The overall waste was pyrolised for approximately 5 to 6 hours. For ease of

practicality and low cost, production technique at Pulau Tekak Besar was carried

out using vertical drum-kiln method similar to previous work [16]. Upon

completion, the carbonised product was collected for characterisation.

2.4. Physico-chemical analysis

For moisture analysis, samples were analysed using MX-50 (AnD) moisture

analyser. One gram of sample was used for this analysis carried out in triplicate.

Samples of both raw material and carbonised product were ground followed by

analysis of pH, electrical conductivity (EC) and ash content. The pH and EC was

analysed with Eutech PC700 (Eutech Instruments) using 1:10 w:v ratio. Ash

content was determined according to AOAC [17]. Samples were also taken for

chemical characteristics on the elemental C, H, N and S using Vario El analyser

(Elementar). Additional analysis on elemental O was obtained as balance between

C,H,N,S and ash percentage. Cation exchange capacity (C.E.C) was conducted

using the barium acetate method [18]. Analysis of P and exchangeable cations (K,

Ca, Mg, and Na) were outsourced to Laboratory & Technical Service Centre,

MARDI Serdang. The exchangeable cations were determined by acid digestion

followed by the use of Inductively Coupled Plasma- Atomic Emission

Spectroscopy (ICP-AES, Perkin Elmer).

2.5. Statistical analysis

Statistical analysis was carried out to determine the significance between the

results. All analysis were carried out using one-way ANOVA and Tukey pairwise

test. The analysis was performed on MINITAB version 17.

3. Result and Discussion

3.1. Inventory of waste

Figure 1 showed the mapping of agro-forestry residues in Pulau Tekak Besar, Tasik

Kenyir. Out of 69 locations identified, 18 points with total area of 0.2267 hectare

were selected for inventory and case study. Selection of the area and locations were

based on the zoning area with higher density of waste composition points. In this

study, zone 5 and 6 are the area with the highest number of points. In zone 5, point

number 27, 29, 30, 32, 33, 34, 36, 37, 38 were selected while in zone 6, it was point

6, 7, 10, 13, 21, 22, 23, 25, 28.

Most of the waste biomass were left at the area during pruning and clearing

activities that were carried out for development phase of the park. The residues were

arranged in piles at specific locations. Since there were challenges in waste

characterisation, direct waste point characterisation was applied. Using this approach

the waste were divided into specific zones and identified by GPS points. The

uncertainties of the waste homogeneity at the specific waste GPS points were

estimated at ±15% based on expert judgement. The evaluation and sample collection,

however, were carried out with proper observation thus, only samples representing

the area were selected. The uncertainty is therefore, can be reduced in future if both

characterisation using GPS points and standard plant identification can be done.



Zoning of the waste area is important, particularly for the purpose of organising

the collection and re-utilisation of waste for specific purpose. Analysis using the

Arc-GIS evaluated zone 1, zone 2 and zone 3 with covered area of 0.64, 0.62 and

0.62 hectare, respectively. Zone 1 was the area where intensive development

activity occurred (Fig. 1). Zone 2 and zone 3 were the hilly area of the island.

Although there were structural developments in zone 4, the area was mostly plateau

and thus covered 1.2 hectare. The remaining of the zone 5 and zone 6 which were

mostly trees also constitute bigger zoning area at 1.2 and 1.0 hectare, respectively.

The division of the area into six zones, therefore, ensured that the waste

management activities were carried out more efficiently.

Fig. 1. GIS mapping of selected orchard residue

location at Zone 5 and 6, Pulau Tekak Besar.



Table 1 showed the characteristics of raw materials and carbonised product at

all selected location points under study. Mass of the initial raw material was found

to be 1206 kg (d.w) while the yield of the carbonised product was 381.9 kg (d.w).

The conversion rate of raw materials to product was calculated at average of 31.7%

(kg/kg d.w). The yield was in agreement with Brendova et al. [19] who used slow

pyrolysis process and reported biochar yield of 35 wt.%. Herath et al. [20] and

Sensoz et al. [21] also obtained similar yields.

While the average biochar yield was 31.7% (w/w d.w), carbonised product from

point 6, 7, and 23 recovered almost 45% (w/w d.w) from initial weight. The greater

yield may be due to variations in the temperature during production, particle size,

holding time and presence of foreign non-combustible substances (e.g., dirt). A

study conducted by Al-Wabel et al. [22] on the effects of different pyrolysis

temperature of conocarpus waste showed trend of yield reduction by approximately

20% when pyrolysis was conducted at two temperature difference of 200 oC and

400 oC. It was further elaborated, as highlighted earlier in the study by Yang et al.

[23], that decomposition of three main constituents of hemicellulose, cellulose and

lignin occurred at different temperatures, mostly within the scale of low pyrolysis

(<500 oC). Hemicellulose may decomposed at 220-315 oC, cellulose at 315-400 oC

and lignin from 200 700 oC. Slight difference in pyrolysis temperature below 400 oC may affect the rate at which these three constituents degrade. Other studies have

also shown the yield sharply reduced if the temperature varies between 300 oC to

400 oC. As identified in Rao and Sharma [24] and Lee et al. [25], these studies were

mostly observed on thermos-gravimetric study. Therefore, it can be explained in

this study that since self-charring field pyrolysis method was used, slightly lower

temperature differences of the pyrolysis may give higher overall yield. At the other

end, lower yield (lesser than 25%) as identified in Table 1 may be attributed to

higher pyrolysis temperature.

Table 1. Rate conversion and final composition (% w/w)

of carbonised products at selected agro residue location point.

Point

Location

Raw

materials

before

(kg f.w)

Raw

materials

before

(kg d.w)

Carbonised

produced

(kg f.w)

Carbonised

produced

(kg d.w)

Carbonised

/raw

materials

(%w/w f.w)

Carbonised

/raw

materials

(%w/w

d.w)

6 40 35.7 21.5 14.7 53.8 41.3 7 40 35.1 20 16.8 50.0 47.7

10 102 90.2 54 30.6 52.9 34.0

13 40 35.2 18 14.0 45.0 39.7 21 56 43.5 19 17.2 33.9 39.5

22 60 50.0 23 16.6 38.3 33.1

23 80 66.6 36 32.5 45.0 48.8 25 42 34.8 20 9.2 47.6 26.5

27 135 118.4 38 35.0 28.1 29.6

28 85 77.9 29 16.9 34.1 21.7 29 103 91.5 25 23.1 24.3 25.3

30 120 102.2 37 33.5 30.8 32.8 32 98 87.4 31 27.9 31.6 32.0

33 70 62.6 20 12.9 28.6 20.5

34 58 49.4 20 18.0 34.5 36.5 36 60 50.4 20 9.8 33.3 19.4

37 65 56.0 27 22.4 41.5 39.9

38 132 119.2 52 30.7 39.4 25.7

Total 1386 1206.0 510.5 381.9 36.8 31.7



Self-charring or self-heating is a process where the system undergoes pyrolysis

without depending on external heating. It means that the temperature cannot be

controlled and the carbonisation relies on the existing raw material itself to provide

the heat. In other words, self-heating is an exothermic process where the released

heat from pyrolysis increased the temperature of the adjacent or existing biomass

[26]. This creates a chain of carbonisation through slow pyrolysis. Figure 2 shows

the vertical drum-kiln design used in this study. It was a bottom up slow

pyrolysation process where self-heating process pyrolyse or carbonise the biomass

beginning from the bottom part in the upward direction. It may take up to 6 hours

for a complete carbonisation process.

Fig. 2. Schematic diagram of vertical drum

kiln pyrolysis with bottom up carbonisation.

3.2. Physico-chemical characteristics

There were variable differences in the amount of ash in the carbonised products

(Table 2). Charred carbonised product have higher percentage of ash compared to

raw materials. High ash content is associated to alkaline properties, which makes

the carbonised product a good liming source for soil application [27]. This

relationship of higher ash content with alkaline pH properties can be seen from

Table 2. The changes on ash and pH occurred during carbonisation where

devolatilization process contributed to the reduction in dry weight of the materials.

Transitional metals, however, do not volatilize but collectively form ash and its

percentage in the end product may be influenced by carbonisation temperature and

residence time [28]. Detailed analysis of the results in Table 2 showed that biochar

from several locations have a higher ash content compared to others (p < 0.05). In

view of this, comparison on the difference of carbon percentage will further define

the characteristics of each material.

The pH of the carbonised products become alkaline with highest value

approaching 10.0 for location point 13 (Table 2). In accordance with United States

Salinity Laboratory Staff [29], the results showed significant differences when



compared to other point sources (p < 0.05). Biochars were also classified based on

EC or salinity. The electrical conductivity of biochars (p < 0.05) from point 6, 10, 32,

37 and 38 are particularly low, while a few others are classified on the upper groups.

Lowest value obtained was 304.7 μS/cm while the highest is 8270 μS/cm. As earlier

evaluated by Nor Ayshah Alia et al. [15], for eventual application, alkaline properties

of the product may increase or correct soil pH of any introduced plants, at 4.0 to 4.8.

In addition to pH, values of EC from low to moderate are appropriate for soil

applications.

Table 2. Moisture content (%), ash (%), pH and electrical conductivity (EC) of

raw materials and carbonised products at selected agro residues location point.

Point

Location

Moisture

content %

Raw materials Carbonised products

Ash % pH EC (μS/cm)

Moisture

content

%

Ash % pH EC (μS/cm)

6 10.8 BCD 1.1 BC 5.2DE 180.7G 31.4CDE 4.1 DEF 8.5 CDE 360.0E

7 12.2 BCD 4.8 A 4.5HI 151.5G 16.2 FGH 4.9 CDE 9.9 A 1010.3DE

10 11.6 BCD 0.5C 4.5HI 410.3 CDE 43.3 ABC 4.6 DEF 8.6CD 304.7E

13 12.1 BCD 0.9 BC 4.5HI 383.7DE 22.4 EFG 3.4FGH 10.0A 982.7DE

21 22.4 A 2.0 BC 5.0EFG 1776.5B 9.6H 5.3 BCD 8.7C 4445.0 C

22 16.7 ABC 3.0 B 5.7 B 522.5 C 28.0 DEF 7.7 A 7.9EF 4145.0 C

23 16.7 ABC 1.9 BC 5.7 BC 437.0 CD 9.6H 6.1 BC 7.5F 5895.0B

25 17.1 AB 0.4C 4.8 EFGH 498.5 C 53.9A 5.5 BCD 8.0DEF 3495.0 C

27 12.3 BCD 1.0 BC 5.1DEF 524.5 C 7.8H 3.9 EFG 7.9EF 3710 C

28 8.3 D 1.0 BC 4.8 EFGH 136.0G 41.6ABC 3.6 EFG 9.0 BC 832.7DE

29 11.2 BCD 0.2C 4.2I 351.5DE 7.6H 4.3 DEF 8.6CD 1863.7D

30 14.8 BCD 1.0 BC 6.4 A 379.5DE 9.4H 6.0 BC 9.0 BC 1869.0D

32 10.8 BCD 2.1 BC 4.5HI 222.0FG 9.9GH 5.7 BCD 8.4 CDE 415.7E

33 10.6 BCD 0.7C 4.8FGH 113.3G 35.7CD 2.2H 9.0 BC 569.3DE

34 14.9 BCD 0.4C 4.6GH 320.3EF 9.8H 4.2DEF 8.0 DEF 8270.0 A

36 16.0 ABC 0.5C 5.3 CD 316.3EF 51.0 AB 6.3B 9.4 AB 1010.3DE

37 13.8 BCD 0.7C 4.7GH 328.7DEF 17.2 FGH 2.7GH 8.8 BC 348.3E

38 9.7 CD 1.4 BC 3.7J 8646.7 A 41.0 BC 3.2 FGH 8.8 BC 340.3E

Note: Statistical analysis using one-way ANOVA; Tukey pairwise analysis indicates that column that have the same letter are statistically similar

Elemental analysis in Table 3 shows percentage in carbon content when raw

materials were carbonised. The results obtained significance difference to each

other (p < 0.05). Average carbon content for raw materials varied between 41.1%

to 61.1%. However, carbon content of the carbonised product ranges between

24.5% to 83.4%. Tukey pairwise analysis showed carbonised material with more

than 50% C content belongs to the upper group while the rest falls in the lower

group. Pyrolisation of biomass have variable effects of increasing and decreasing

in the percentage of carbon content of final products. Study by Windeatt et al. [30]

on eight different agricultural residues showed increase in percentage of carbon

content in the end products when compared to the raw materials. Study by Ghani

et al. [31] also highlighted carbon content increases with the increasing of

pyrolisation temperature. Therefore, lower carbon content in the carbonized



products at several residue points in this study may have attributed to the conditions

during pyrolysis.

Table 3. Chemical characteristics of raw materials and

carbonised products at selected agro residues location point.

Point

Location

Raw Materials Carbonised products

C [%] H [%] N [%] S [%] O [%] as

difference C [%] H [%] N [%] S [%]

O [%] as

difference

6 61.1A 6.0 BCD 1.0G 0.2 B 30.7 28.3FG 3.5 CDE 0.3 BCD 0.4 A 63.4

7 52.7C 5.1 EFG 1.0G 0.2 B 35.8 24.5G 3.2 DE 0.3 BCD 0.1 B 67.0

10 58.4 AB 5.9 BCD 1.7 EFG 0.2 B 33.3 31.6 EFG 4.8 A 0.4B 0.2 AB 58.5

13 38.9E 5.5 DEF 4.2 B 0.2 B 50.3 83.4 A 2.8 E 0.6A 0.1 B 9.7

21 56.9 B 6.6 AB 1.7 FG 0.1 B 32.6 32.1 EFG 3.9 ABCD 0.4BC 0.1 B 58.2

22 59.0 AB 6.1 BCD 2.4 DEF 0.1 B 29.4 29.9FG 3.3 CDE 0.2 DE 0.1 B 58.7

23 44.9D 7.0 A 1.4G 0.1 B 44.8 34.7 EFG 4.1 BCDE 0.3 BCDE 0.1 AB 58.0

25 56.9 B 6.3 ABC 2.3 DEF 0.1 B 34.0 35.9 EFG 4.1 ABCD 0.3BCD 0.1 B 54.1

27 57.3 B 6.1 BCD 2.5 DE 0.1 B 33.0 37.9 EFG 4.0 ABC 0.2 CDE 0.1 B 53.7

28 44.1D 6.1 BCD 5.3 A 0.1 B 43.4 44.6CDE 4.1 ABCD 0.2 DE 0.0 B 47.5

29 58.3 AB 5.7 CDE 2.6CD 0.2 B 33.1 38.8DEF 4.0 ABCD 0.2 CDE 0.1 B 52.3

30 45.3D 6.0 BCD 5.4 A 0.1 B 42.2 51.9 BCD 4.1 ABCD 0.2 DE 0.0 B 37.7

32 44.4D 6.2 ABCD 4.8 AB 0.1 B 42.4 52.9 BC 3.9 ABCD 0.3 BCD 0.0 B 37.7

33 59.4 AB 6.4 ABC 2.8CD 0.2 B 30.6 54.8 BC 3.7 BCDE 0.2 DE 0.0 B 38.9

34 45.5D 6.5 AB 4.6 AB 3.6 A 39.3 59.0 B 3.5 CDE 0.2 DE 0.0 B 33.1

36 44.1D 6.1BCD 3.4C 1.1 B 44.8 63.1 B 4.6 AB 0.2 CDE 0.0 B 25.7

37 41.9DE 4.8 FG 2.9CD 0.0 B 49.7 63.9 B 3.8 ABCDE 0.3 BCD 0.0 B 29.3

38 42.2DE 4.7 G 3.0CD 0.0 B 48.8 61.6 B 3.3 CDE 0.1 E 0.0 B 31.7

Note: Statistical analysis using one-way ANOVA; Tukey pairwise analysis indicates that column that

have the same letter are statistically similar.

The in-situ kiln used in the study is a bottom up self-charring pyrolysis where

manual termination of combustion is required at the end of the pyrolysis process. It

is possible that the process occurred with less efficiency thus affecting the elemental

C content of the end products. By definitions of European Biochar Certificate [13],

sample of the end product from 8 points (13, 30, 32, 33, 34, 36, 37, 38) fulfil one of

the important criteria of biochar due to carbon percentage of more than 50%.

However, the remaining point samples (6, 7, 10, 21, 22, 23, 25, 27, 28, 29) were still

higher in carbon, with percentage between 24% to 50%, which are still significantly

higher if compared to samples obtained through burn-to-ash or complete combustion

method. These black charring samples, having similar physical attribute to biochar,

are defined as pyrogenic carbonaceous material (PCM).

Additional analysis on the ratio of O/C and H/C was carried out to observe the

trends using the Van Krevelen diagram. Figures 3 and 4 showed the results of the

ratio analysis based on the earlier characterisations of biochar obtained from 8

points and PCM on the remaining 10 points. As observed in study by Tag et al.

[32], the graph obtained in Fig. 3 on samples with biochar characteristics showed

similar trends on raw material to biochar. The normal trends were observed where

raw materials were at the right top while the biochars at the left bottom (Fig. 3).

The graph obtained in Fig. 4 for PCM however, was opposite to normal Van

Krevelen diagram for biochar. The figure shows that the raw materials were at the

left top while the PCM at the right top. One of the factor that contributed to this



trend was due to the lower C contents in the carbonised samples compared to the

raw materials (Table 3). Lower C contents resulted to higher O/C ratio for PCM

and thus, change the normal positions in the diagram. This observation may suggest

that pyrolysation of the 10 points PCM were not efficient where losses of carbon

occurred during the process. This affected the final C contents in the product. PCM

still however, contributes to positive effects if applied to soil. In-situ applications

of both carbonised biochar and PCM may increase soil carbon contents. It could

also reduce the decomposition of native organic C in soil [33].

Fig. 3. Van Krevelen diagram of raw material and

carbonised product from 8 points with biochar characteristics.

Fig. 4. Van Krevelen diagram of raw material and carbonised product

from 10 points with characteristics of pyrogenic carbonaceous material.

The trend of O/C and H/C of the raw materials can be observed from Figs. 3

and 4. It was identified that the value of O/C is between 0.50 to 1.29 while H/C is

between 0.09 to 0.15. The results are comparable to other biomass sources. Study

by Vassilev et al. [34] on wood and woody biomass groups obtained the values of

O/C between 0.65 to 0.79 and H/C between 0.11 to 0.17. The trends of the H/C

values are comparable however, the ranges of minimum and maximum for O/C

values are bigger in this study. Lower O/C can be contributed from higher carbon

percentages at 50% to 60% (Table 3). This characteristic was also observed in other

local biomass source. Rubber-wood saw dust for instance, which contains of 53.4%



carbon, has O/C value of 0.69 [35]. Variable differences in other characteristics

such as the percentage composition of cellulose and lignin can also contributed to

the O/C values. Couhert et al. [36] described bigger quantity of O in cellulose as

compared to lignin. This ultimately increases the ratio of O/C. A trend of higher

O/C value at above 1.0 can be observed from a local biomass of meranti-wood saw

dust, which has O/C value of 1.26 [37]. Therefore, a bigger range in the minimum

and maximum values obtained in this study is justifiable to represent the

characteristics of different types of local biomass sources.

From Table 4, C.E.C of the biochar mostly below 20 cmol/kg (p < 0.05).

Highest was measured at point 30 at 25.0 cmol/kg. Shenbagavalli and Mahimairaja

[38] reported ranges of C.E.C between 3.2 to 16.0 cmol/kg for 2 hours slow

pyrolysis of biomass waste using specially designed pyrolysis-stove. The C.E.C

value were quite similar to those obtained in this study although raw materials and

method of pyrolysis differs. In comparison, study on local biomass of coconut

shells and rice husk showed C.E.C value of 5.1 and 18.3 cmol/kg respectively [16].

Earlier study on the soil properties in Pulau Tekak Besar identified CEC value

within the range of 7.4 to 21.0 cmol/kg [15]. Therefore, the value obtained in this

study indicates that characteristics of CEC of the carbonised materials are almost

identical to the soil properties of Pulau Tekak Besar.

Table 4. CEC and chemical percentage of other macronutrients

of carbonised products at selected agro residues location point.

Point location CEC (cmol/kg) P [%] K [%] Ca [%] Mg [%] Na [%]

6 15.0 AB 0.01 BC 0.15 EFGH 0.27 G 0.18 CDE 0.05 BCD

7 20.0 A 0.03 BC 0.44 AB 0.47 B 0.17 DE 0.04 BCDE

10 15.0 AB 0.07 A 0.42 ABC 0.45 BC 0.17 DE 0.06 BCD 13 17.5 AB 0.01 C 0.25 CDEFGH 0.12 H 0.11G 0.05 BCDE

21 15.0 AB 0.02 BC 0.56 A 0.40 BCD 0.29 B 0.09 A

22 2.5 B 0.02 BC 0.26 CDEFG 0.27 G 0.22 C 0.06 ABC 23 11.7 AB 0.02 BC 0.32 BCDE 0.25 G 0.20 CD 0.07 AB

25 20.0 A 0.02 BC 0.34 BCD 0.25 G 0.16 EF 0.04 BCDE

27 17.5 AB 0.02 BC 0.27 CDEFG 0.40 BCD 0.12 FG 0.04 BCDE

28 15.0 AB 0.03 B 0.58 A 0.80 A 0.42 A 0.04 BCDE

29 23.3 A 0.03 BC 0.30 BCDEF 0.31EFG 0.15 EFG 0.07 AB

30 25.0 A 0.02 BC 0.29 BCDEF 0.32 DEFG 0.18 CDE 0.02 DE 32 10.0 AB 0.02 BC 0.08 H 0.40 BCDE 0.17 DE 0.03 CDE

33 11.7 AB 0.01 C 0.15 FGH 0.06 H 0.01H 0.02 DE

34 17.5 AB 0.02 BC 0.33 BCD 0.30 FG 0.16 EF 0.02 DE 36 18.3 AB 0.01 C 0.25 CDEFG 0.06 H 0.05 H 0.04 BCDE

37 11.7 AB 0.02 BC 0.19 DEFGH 0.14 H 0.11FG 0.03 CDE

38 13.3 AB 0.01 C 0.11GH 0.37 CDEF 0.18 CDE 0.01E

Note: Statistical analysis using one-way ANOVA; Tukey pairwise analysis indicates that column that

have the same letter are statistically similar.

Carbonised products, mainly biochar have minimal C.E.C when initially

produced but its value increased over time in soil due to surface oxidation [39].

Higher C.E.C value increases the capacity of the soil combinations to control the

leaching of positively charged ammonium ions after fertiliser or manure application

[40]. In view of this, it is possible that initial C.E.C value of 10-20 cmol/kg may

eventually increase over several period of time once applied to soil.

Results for available P and exchangeable K, Ca, Mg and Na obtained in this

study (Table 4) were relatively low although statistically significant (p < 0.05) in

comparison to different waste points. Values were initially obtained as ppm but



converted to percentage for standardization. Since the biomass used in this study is

from orchard and forest pruning, it is possible that the amount of macronutrients to

be lower in value as compared to other waste agricultural products. Although

percentage of macro nutrients is low, it is still important to maintain nutrient

balance in an ecosystem.

Comparison between macronutrients in Table 4 showed that the carbonised

products are higher in percentage of K and Ca. In view of this, Oram et al. [41]

describes the added advantage of biochar of having more available form of K. This

may result to more availability and absorptivity of the nutrient in plant.

Nutrient conservation can be achieved through appropriate processing and re-

utilising of biomass. Silver et al. [42] suggested that forest trimmings or prunings

could increase nutrient uptake and reduce competition for nutrients. Therefore, it

must be emphasized that in-situ re-utilisation of pyrolysis products of biomass

harvests from pruning is one of the mechanism to achieve this aim. Pyrolisis,

through method of slash-and-char can be the best alternative to slash-and-burn [43].

It avoids destruction of forests and functioned as carbon and nutrient conservation

technique in comparison to conventional slash-and-burn [44].

The overall results suggest that carbonisation of biomass waste is suitable for

application in the area where new orchard is being developed. Although vertical

drum-kiln technique is already common especially in coconut industry in Malaysia,

its applicability and advantage to convert orchard waste into useful carbonised

products were thoroughly discussed in this paper. The carbonised products, which

consist of both biochar and PCM, has been the subject of interest due to its

additional benefits and suitability as organic amendment in soil. Further study is

required for determination its effectiveness on plant nutrient uptake particularly in

relation to microclimate and soil environment in Pulau Tekak Besar.

4. Conclusion

From the above discussions, carbonisation of orchard residue is a potential method

to retain higher carbon contents of biomass. This was observed through 8 sample

points of having more than 50% C while several other points still contain higher

percentage. Ratio of carbonised/raw materials, which is in average of 31.7% (w w-

1 d.w), is higher compared to conventional method of slash-and-burn, which

ultimately account for the amount of ash after burning. Other attributes of

carbonised products such as C.E.C value between 10.0 to 20.0 cmol kg-1 is

compatible to existing soil condition in the study area of Pulau Tekak Besar.

Salinity of the carbonised products between 304.7 μS/cm and 8270 μS/cm are

suitable for plants. It can be concluded that carbonised product of pyrolysis can be

useful for soil application and in-situ reutilisation. It is also an alternative method

for effective biomass or solid waste management in any orchard area. Study on the

effects of the carbonised products on specific plant growth can be carried out to

determine its effectiveness and efficacies.

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Documents

PHYSICO-CHEMICAL CHARACTERISATION OF CARBONISED …jestec.taylors.edu.my/Vol 14 issue 1 February 2019/14_1_02.pdf · residue points were located using GPS hand held device (Garmin