PHYSICOCHEMICAL AND PHYTOTOXICITY ANALYSIS OF SAGO BARK WASTE COMPOST

Abstract

Sago bark (SB) waste is available abundantly as sago processing by-products in Sarawak. The release of SB waste into waterways could harm aquatic life and burning of SB will cause air pollution. In this work, SB waste is utilized via composting process to produce compost foragricultural use.The physicochemical characteristics and phytotoxicityof the prepared compost was evaluated monthly. SB compost was prepared by mixing SBwaste with chicken manure and empty fruit brunch (EFB) in ratio 6:6:1. The maturity and stability of compost in three months composting process was evaluated via physicochemical characterization of the composts in terms of pH, total ash content, total organic content and elemental analysis. The effect of the composts usage as growth medium and the phytotoxicitywas assessed towards aromatic lettuce via seed germination. Results showed that after three months, the composts colour were dark brown with earthy smell. The volume and weight of the compost was decreased.The total ash content and total organic matter of the SB compost were increased and decreased respectively during 3 months composting. Total C/N ratio was 21.63, 13.38 and 4.91 during first, second and third month respectively. The pH of the compost is alkaline after three months of composting. The germination index (GI) for studied vegetables was >100% after five days after germination.

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Proceedings of ISER 119th International Conference, Kuala Lumpur, Malaysia, 1st-2nd April 2018
49
PHYSICOCHEMICAL AND PHYTOTOXICITYANALYSIS OF
SAGOBARK WASTE COMPOST
1RAFEAHWAHI, 2EFFA RADIKABIDIN, 3ZAINABNGAINI
Resource Chemistry Programme, Faculty of Resource Science and Technology, Universiti Malaysia
Sarawak, 94300 Kota Samarahan, Sarawak
E-mail: wrafeah@unimas.my, effardka@gmail.com
Abstract - Sago bark (SB) waste is available abundantly as sago processing by-products in Sarawak. The release of SB waste
into waterways could harm aquatic life and burning of SB will cause air pollution. In this work, SB waste is utilized via
composting process to produce compost foragricultural use.The physicochemical characteristics and phytotoxicityof the
prepared compost was evaluated monthly. SB compost was prepared by mixing SBwaste with chicken manure and empty fruit
brunch (EFB) in ratio 6:6:1. The maturity and stability of compost in three months composting process was evaluated via
physicochemical characterization of the composts in terms of pH, total ash content, total organic content and elemental
analysis. The effect of the composts usage as growth medium and the phytotoxicitywas assessed towards aromatic lettuce via
seed germination. Results showed that after three months, the composts colour were dark brown with earthy smell. The volume
and weight of the compost was decreased.The total ash content and total organic matter of the SB compost were increased and
decreased respectively during 3 months composting. Total C/N ratio was 21.63, 13.38 and 4.91 during first, second and third
month respectively. The pH of the compost is alkaline after three months of composting. The germination index (GI) for
studied vegetables was >100% after five days after germination.
Keywords - Sago bark waste, agriculture waste, compost, physicochemical, maturity
I. INTRODUCTION
Sarawak is currently one of the world’s largest
exporter of sago products, with annual export of
approximately 43,000 tonnes [1]. It is estimated that
0.75 tonnes SB waste is generated for every tonne of
sago flour produced [2], which accounts for 32,250
tonnes of annual SB waste generation. SB waste is
normally incinerated for power generation in sago
mills, dumped directly into nearby rivers or left for
netural degradation outside sago mills [3]. More than
85% ofSB is left unutilized in sago processing mill,
giving opportunity for utilization of the waste as useful
products.
Previous research has shown that composting can help
in reducing the problems of agricultural waste, as well
as providing products that can be used for agricultural
purpose [4]. Composting is a controlled
decomposition of organic material to produce highly
stable and pathogenic free compost, which can be used
to improve soil structure or nutrient quantity [5].
Previous studies on composting revealed that the
composting conditions must be carefully maintained
in order to ensure the efficiency of the process, and a
matured compost is obtained at the end of the process
[6]. As the use of immature compost could lead to
unwanted alteration in soil physical properties and
plant growth [7], it is crucial to monitor the
physicochemical properties of the compost throughout
the composting process. In this work, investigated was
the physicochemical characteristics of SB compost
prepared in a three-month period. The seed
germination study was also conducted to study the
applicability of the prepared composts as plant growth
medium.
II. MATERIALS AND METHOD
A. Composting Process
SB waste was collected from Ubom Sago Mill SdnBhd
in Mukah, Sarawak, Malaysia. Samples were washed,
dried, ground and sieved into particle size range 0.1 to
0.5 cm prior to use. The composting process was
conducted inside rectangular containers (20.0 cm
length, 20.0 cm width, and 20.0 cm height). The
composts were prepared by mixing the SB with
chicken manure, and empty fruit brunch (EFB) as
bulking agent, in the ratio 6:6:1 (SB
waste:chickenmanure:EFB). The compost turning was
done once daily to ensure the moisture content were
kept between 50-70% [8]. Compost temperature was
taken daily before turning the compost.Compost
samples were taken monthly for analysis.
B. Physicochemical Analysis
The temperature of the compost was measured daily
before compost turning,using soil thermometer.The
changes in compost mass was measured by comparing
with the initial mass of the compost with the mass at
the end of each composting stage. The odour of
compost was analysed by the presence of lack sour or
ammonia odour, before and after the composting
process based on physical observation directly in the
compost pile [9]. The pH ofthe compost was measured
using pH meter in distilled water at a sample/water
ratio of 1:5 [10].Moistureand ashcontent was
determined following previous studies [11], [12].Total
organic carbon (TOC) and organic matter content
were determined by wet oxidation using the
Walkley–Black dichromate digestion method [10].
Total N was determined using an elemental analyzer
using CHN Analyser Flash EA 112 Series. The C/N

Physicochemical and Phytotoxicity Analysis of SagoBark Waste Compost
Proceedings of ISER 119th International Conference, Kuala Lumpur, Malaysia, 1st-2nd April 2018
50
ratio was calculated from the measured values of total
carbon and total N from CHN Analyser. The
phosphorus content was determined by using Olsen
method analysed by UV/VIS spectrophotometer at the
wavelength 880 nm referring to [13].All analyses were
conducted in triplicates.
C. Germination Study
Germination study was carried out in triplicates,
following the method of [14]. The treatments
wereconducted to observe the relative seed
germination (RSG), relative root growth (RGG) and
germination index (GI), whichwere calculated based
on equation below[15].
RSG (%) = 
 × 100% (Eq. 1)
GI (%) =  × 
 ×  × 100% (Eq. 2)
RGG (%) = 
 (Eq. 3)
[Note: N = number of germinated seed, L = root
length]
III. RESULTS AND DISCUSSION
A. Physicochemical Analysis
The monitored temperature(Figure 1) showed that this
compost is in the mesophilic range (25 – 34.6oC),
whereby temperature changes during composting is
mainly divided into two phases which are
namelymesophilic phase (<45oC) and thermophilic
phase (>45oC) [16]. The pattern of the temperature is
related to the main component of sago bark which is
lignin. Particularly, rich-lignin plant is difficult to
biodegrade due to the lignocellulosic nature of the
substrate in compost [17]. The lignin content and its
distribution in SB cells acted as physical or chemical
barrier during composting, which slowed down the
process [18].However, the heat production of the
compost also dependson the size of the pile, its
moisture content, aeration, and the C/N ratio of the
compost materials [19].
The compost mass decreased dramatically during
three months composting, with percent mass loss
range46-60% (Table 1). The compost mass losses is
associated to organic matter degradation.In addition,
carbon dioxide and water vapor loses during
composting can amount to half the weight of the initial
materials, thus the mass and volume of the final
product is decreased [20].
The pH (Table 1) decrease from 8.4 in the first month
to 8.6 in the third month of composting. A normal pH
measurement for compost is between 6.5-8 because
the low acidification, the microbes will active as it
related to an anaerobic condition inside the compost
[21].The ash content (Table 1) increased from 50 to
63%, due to the mineralization process of organic
matter in SB. As the organic matter decreased, the
total ash content of compost increased as well as
reduces the weight of the pile and C/N ratio.The range
of total organic matter after 3 months (SB3) of
composting was 37%, which was within the
recommended range[22]. The C/N ratio of SB3 was
4.91% (Table 1), which can be regarded as
maturedenough to be applied for agricultural purpose
[23]. Visual inspection showed that the composts were
dark brown to black in color and has an earthy smell
(Table 2). The compost is regarded as mature when the
color is dark brown and has earthy wood smell.
B. Seed Germination
Table 3 showed relative seed germination (RSG),
relative root growth (RRG) and germination index
(GI) of leafy vegetables tested with SB compost after 5
days of germination. The germination index is very
important to the seed as it will indicate the presence of
phytotoxins for which it could vary with the plant
growths [25]. Result showed that RSG and RRG value
for the vegetables with both SB compost higher
compare to the control. The RRG indicates that water
spinach (Ipomea aquatic) in SB3 (237.03%) has the
highest growth followed by SB1 (198.75%) and SB2
(186.27%). Table 1
Physico-chemical parameters during composting (SB1: first
month; SB2: second month; SB3: third month).
Compost
SB1
SB2
SB3
Mass (g)
194.18
170.74
142.62
pH
8.40
8.60
8.60
TOC
(%)
67.75
53.40
46.13
TN (%)
1.40
1.97
5.49
C/N
Ratio
21.63
13.38
4.91
Ash (%)
50.03
56.64
62.64
TOM
(%)
49.97
43.36
37.36
TP (%)
0.25
0.24
0.26
[TN: Total nitrogen; TOC: Total organic carbon;
TOM: Total Organic Matter; TP: Total phosphorus]

Physicochemical and Phytotoxicity Analysis of SagoBark Waste Compost
Proceedings of ISER 119th International Conference, Kuala Lumpur, Malaysia, 1st-2nd April 2018
51
Table 2
Visual inspection for odor and color of composts.
Compost
SB1
SB2
SB3
Colour
Brown
Dark
brown
Blackish
brown
Odour
Woody
earthy
Woody
earthy
Woody
earthy
Table 3
Seed germination of compost.
CONCLUSION
After 3 months of composting process, C/N ratio
decreased which reached 4.91 in the third month from
21.63 in the first month. The increase in ash content at
the end of the composting process, 62.64%, indicates
the mineralization process of starting organic matter
and resulting in high concentration of mineral
elements in the composts. The mass losses associated
to organic matter degradation. Seed germination study
of SB compostgives more than 100% germination
index which proved that SB compost is free from
toxicity.
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