Published at : 28 Jun 2023
Volume : IJtech
Vol 14, No 4 (2023)
DOI : https://doi.org/10.14716/ijtech.v14i4.6015
Arief Ameir Rahman Setiawan | 1. Graduate School of Science and Technology, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, 305-8572, Japan, 2. Research Centre for Sustainable Production System and Life Cycle Assessment, National |
Ary Mauliva Hada Putri | Research Centre for Chemistry, National Research and Innovation Agency, 452 Bldg, Puspiptek, Tangerang Selatan, 15314, Indonesia |
Teuku Beuna Bardant | Research Centre for Chemistry, National Research and Innovation Agency, 452 Bldg, Puspiptek, Tangerang Selatan, 15314, Indonesia |
Roni Maryana | Research Centre for Chemistry, National Research and Innovation Agency, 452 Bldg, Puspiptek, Tangerang Selatan, 15314, Indonesia |
Yanni Sudiyani | Research Centre for Chemistry, National Research and Innovation Agency, 452 Bldg, Puspiptek, Tangerang Selatan, 15314, Indonesia |
Muryanto | Research Centre for Chemistry, National Research and Innovation Agency, 452 Bldg, Puspiptek, Tangerang Selatan, 15314, Indonesia |
Eka Triwahyuni | Research Centre for Chemistry, National Research and Innovation Agency, 452 Bldg, Puspiptek, Tangerang Selatan, 15314, Indonesia |
Deliana Dahnum | Research Centre for Chemistry, National Research and Innovation Agency, 452 Bldg, Puspiptek, Tangerang Selatan, 15314, Indonesia |
Nino Rinaldi | Research Centre for Chemistry, National Research and Innovation Agency, 452 Bldg, Puspiptek, Tangerang Selatan, 15314, Indonesia |
Yan Irawan | Research Centre for Chemistry, National Research and Innovation Agency, 452 Bldg, Puspiptek, Tangerang Selatan, 15314, Indonesia |
Tofael Ahamed | Faculty of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, 305-8572, Japan |
Ryozo Noguchi | Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan |
Black liquor combustion; Cellulose hydrolysis; Energy effectiveness; Utilization
In commercial scale best practice, as also simulated in this paper, the
fiber and shell were simulated to be burned as an energy source. Empty Fruit
Bunch (EFB) becomes the rest challenging waste to deal with. Utilization of EFB
ash for fertilizer is no longer an interesting option since many Crude Palm Oil
(CPO) producing countries not allowing EFB burning in plantation sites (Walker et al., 2018; Van-Dam, 2012). Thus, a special incinerator was required for
converting EFB into ash. Mulching EFB to the plantation land was the second
cheapest practice and claimed to improve soil deterioration management by
avoiding run-off and erosion (Afandi et al., 2017). Along with global concern for the
environmental impact of the production process, the Global Warming Potential
(GWP) of the process becomes a challenging issue. The GWP per ton of EFB, if stockpiled
on land surfaces as the open lagoon-like mulching practice, is 180.90 kg CO2
equivalent (Nasution et al., 2020).
Converting EFB into ethanol is one of the promising options due to its
potential availability, as acknowledged in a previous review (Hossain et al., 2017). The conversion path
proposed by this review was similar to this study, which is through Saccharomyces
cerevisiae fermentation. The review also briefly introduced commercializing
other fermentation products as a co-product, xylitol. Selling dried yeast is
also a co-product option. A preliminary study utilizing EFB hydrolysate for
producing dried Saccharomyces cerevisiae yeast gave promising results.
The production cost per kilogram of dried yeast was less than Rp 20,000.00 or
US$ 1.27 (Hermansyah et al., 2015).
The potential profit from co-product is an advantage for covering the extra
cost in EFB-to-ethanol conversion. The extra cost came from the lignocellulose
pre-treatment requirement. Some studies even observed the utilization of advanced
physical process assistance for pre-treatment, such as microwaves (Harahap et al., 2019) and ultrasound (Hermansyah et al., 2019). However, the
production cost is still challenging compared to starch-based raw materials.
A previous study used tofu waste as raw material and Aspergillus
niger as hydrolyzing agent (Febrianti et al.,
2017). The study reported that substrate conversion efficiency was up to
88%, but the obtained bioethanol was 7.69 g/L. Bioethanol production through
fermentation other than yeast was reported using Clostridium ljungdahlii
(Anggraini et al., 2019). The
bacteria used synthetic gas as a feed, but the obtained ethanol concentration
was 1.09 g/L. Similar to the previous study, the obtained ethanol concentration
was considered low, which led to a great challenge in it is
refinery feasibility.
This research proposed a
simulation for the integration of EFB into an ethanol conversion unit. A
comparative evaluation between two ways of integrating the conversion process
was conducted. Whether the EFB–to-Ethanol plant is integrated into a pulping
plant or integrated into an RBD palm oil production plant. The evaluation was based on their potential
energy-environment benefits. This is a step further from the Multi Criteria Decision Making (MCDM) technique applied in the assessment of composting for
organic waste management in the previous study (Shukor
et al., 2018). More calculated results based on reliable data
from the existing pilot plant were provided in this study to make it more
credible and traceable for validation.
Figure 1 Brief scheme for the
first archetype, when 2nd G Bioethanol integrated into RBD palm oil plant.
Yellow boxes were units for pulping process. Red boxes were units for the RBD palm
oil process
The water, steam, and electricity requirement in the oil
extraction was then calculated. The oil needs to be refined to meet the
commercial requirement by eliminating free fatty acids and fruit wax. The
chemical and energy requirement was also calculated. The process adopted in
this research was the physical process with phosphoric acid as a wax coagulant
and the color adjustment by using bleaching earth. The physical process has a
higher global yield, uses fewer chemicals, and produces less effluent. Most big
companies where the data originated use certified seedlings from the Indonesian
Oil Palm Research Institute (IOPRI). Only a small amount of plantations use
seedling private seedling companies in Indonesia or certified imports from
Malaysia and other parts of the world (Harsono et
al., 2012). Thus, the amount of wax in palm oil fruit in the
observed CPO plant is almost equal. Only small deviations were reported for the
required energy and required phosphoric acid and bleaching earth for the RBD palm
oil process.
The required energy for operating RBD palm
oil plant supplies was simulated using a cogeneration system based on a
back-pressure steam turbine (BPT). This cogeneration system uses fiber and
shell as fuel, which comes from the oil extraction process. Furthermore, the
plant adopted in this study was calculated to meet energetically
self-sufficient so that the electricity produced could feed both the mills
(considered electrified mills) and the process equipment such as pumps,
agitators, and conveyors, among others and in addition to lighting
installations.
2.1.2. EFB-to-ethanol
integrated with EFB pulping plant scenario
In this simulation scenario, all four aforementioned units
were applied in EFB-to-ethanol integrated with EFB pulping plant, except the
RBD palm oil unit. The scheme can be observed in Figure 2. In this scheme, the
energy supply was solely from the black liquor combustion. The main difference
in energy supply can be seen in energy lines which only came from the
reboiler.
The
amount of lignin production was adjusted to the amount of lignin converted into
syn-gas. The produced syn-gas was calculated to equal the required syn-gas for
the lime kiln. Through a series of iteration calculations, energetically
self-sufficient design can be achieved. The setting value for iteration was to
meet a similar amount of ethanol produced from the first scenario. Thus, the
performance of both scenarios can easily be compared. The calculation required
energy included electricity for both the pulping mills (considered electrified
mills) and the process equipment, i.e, pumps, agitators, and conveyors, among
others and in addition to lighting installations.
3.1. General simulation
comparison
The total required energy as steam and electricity for producing 255.6
kg ethanol was 1.293 MW, as shown in Table 2. This amount of energy can be
supplied from the excess energy produced by the RBD Palm oil plant with a
capacity of 5 tons FFB or pulping plant with a capacity of 22.15 tons EFB. This
excess energy was sufficient without any additional fuel required (zero net
energy). EFB-to-ethanol plant integrated into RBD palm
oil plant scenario was preferable in energy
analysis. This is due to the flexibility of energy supply from fiber and kernel
combustion. The excess energy from these combustions was 1.06 MW, or equal to
82% of the required energy for ethanol production. The other 18% of energy came
from dried black liquor combustion from the pulping unit. This dried black
liquor needs to be completely burned for soda regeneration.
Table 1 General comparison of EFB-to-ethanol when integrated into RBD palm
oil plant or pulping plant
Parameters |
Unit |
RBD palm oil |
Pulp |
|
Material input | ||||
Fresh fruit bunch |
kg |
5000 |
0 |
|
Wet EFB available (Moist
73%) |
kg |
2632.81 |
22,151.01 |
|
Fraction of EFB used for ethanol |
% |
58.42 |
2.64 |
|
EFB used for ethanol |
kg |
1538.20 |
1538.20 |
|
Fraction of BL to lignin then syn-gas |
% |
2.55 |
2.55 |
|
Product output | ||||
Wet EFB excess (Moist 73%) (back to the farm) |
|
1,094.62 |
0 |
|
RBD palm oil |
kg |
1,126.92 |
0 |
|
liter |
1,444.77 |
0 |
| |
Wet Pulp (Moist 40%) |
kg |
0 |
17,379.43 |
|
Pulp (Atmospheric dried) |
kg |
0 |
10,427.65 |
|
Ethanol fuel grade (97%v) |
kg |
255.55 |
255.55 |
|
liter |
319.44 |
319.44 |
| |
Additional chemical requirement | ||||
Water |
m3 |
20.88 |
191,32 |
|
Bleaching earth |
kg |
10.76 |
0 |
|
H3PO4 |
kg |
0.57 |
0 |
|
Yeast |
kg |
7.179 |
7.179 |
|
Micronutrient (urea + NPK) |
kg |
13.04 |
13.04 |
|
Enzyme and additives (buffer & surfactant) |
liter |
170.08 |
170.08 |
|
Soda make up |
kg |
29.83 |
429.55 |
|
Lime makeup |
kg |
40.93 |
630.34 |
|
H2SO4 and CO2 |
kg |
4.37 |
62.86 |
|
The total required energy as
steam and electricity for producing 255.6 kg ethanol was 1.293 MW, as shown in
Table 2. EFB-to-ethanol plant integrated into RBD palm oil plant scenario was
preferable in energy analysis. This is due to the flexibility of energy supply
from fiber and kernel combustion. The excess energy from the combustion was
1.06 MW, or equal to 82% of the required energy for ethanol production. The
other 18% of energy came from dried black liquor combustion from the pulping
unit. This dried black liquor needs to be completely burned for soda
regeneration.
Table 2 Energy Utilization
Comparison of EFB-to-ethanol when integrated into RBD palm oil plant or pulping plant
(basic calculation: 255.6 kg of ethanol production capacity)
Parameters |
Unit |
RBD Palm Oil |
Pulp |
Required
electricity for EFB-to-ethanol plant |
MW |
0.14 | |
Required steam for EFB-to-ethanol plant |
MW |
1.153 | |
Total excess power
from black liquor combustion in the boiler (after excluding power consumed
for pulping plat), per ton of dried black liquor |
MW/tons |
0.1 |
0.1 |
Required
EFB to be processed for zero net energy |
tons
EFB |
2.6 |
22.15 |
Total produced dried black liquor |
tons |
1.00 |
14.90 |
Total
excess power from fiber and kernel combustion in the boiler (after excluding
power consumed for RBD Palm Oil plant) per ton of combined fiber and kernel. |
MW/tons |
1.06 |
0 |
Total
produced fiber and kernel |
tons |
1.033 |
0 |
Pollutant
component |
Source |
Amount
(kg) | |
RBD
Palm Oil |
Pulp | ||
To
water treatment plant | |||
Spent
bleaching earth, PFDA and Palm Oil
Mill Effluent (POME) |
Palm oil
extraction plant & oil refining |
5,418.67 |
|
Lignin and
spent yeast |
Distillation
bottom. |
2,847.35 |
2,847.35 |
CaCO3,
NaOH |
Causticization
lime kiln, scrubber and
gas separator |
1,491.98 |
22,890.71 |
Lignin and
NaOH |
Pulp washing |
7,647.26 |
94,303.02 |
To
environment/gas treatment | |||
Multi-stage
evaporator and lignin drier |
water vapor |
5,198.64 |
77,543.36 |
Causticization
and lime kiln |
CO2
and SOx |
6.43 |
177.40 |
The 2nd
generation bioethanol production process has its own appeal since its product
is used as a gasoline substitute and industrial chemicals on one end and
utilizes cheap, abundant, non-food raw material at the other end. In this
context, this study aimed to analyze EFB utilization as ethanol raw material
and as the possibility of converting the potential excess energy in RBD palm
oil production or pulping process into financial profit and reduce waste
simultaneously. This would encourage a reduction in dependence on fossil fuels
(consequently reducing GHG emissions) and improve the system's energy
performance. Integrating an EFB-to-ethanol unit into the RBD palm oil plant with a
capacity of 5 tons FFB processed daily could recycle 58.4% of EFB waste,
increasing income 18.47% of the basic income from selling RBD palm oil solely. This was
achieved by utilizing all the energy potency stored in fiber and kernel to
supply the required energy. To implement the integration, the RBD palm oil plant required almost fourfold processed water
and dealing with threefold wastewater with different pollutants. The types of
operation unit that needed to be installed was also more miscellaneous compared
to the integration of the EFB-to-ethanol unit into the EFB pulping plant. The integration of the EFB-to-ethanol unit into the
EFB pulping plant only required an additional distillation unit and
saccharification-fermentation tank to be installed. The required process water,
the pulping process, and the wastewater treatment unit only had an increasing
workload of 2-5 % which is usually compromised in the original pulping plant
design. This small additional investment gave extra income of 1.9% of the pulp
sales. However, the pulping production capacity needs to be 22.15 tons of
processed EFB daily for the ethanol to be comparable with the aforementioned
RBD palm oil integration. This is due to the small amount
of potential excess energy in dried black liquor. The results outlined in this paper are based on the
integration of technological considerations adopted in each scenario.
Therefore, limitations of the present research would be economical and
feasibility, especially in economic comparison for selling kernel or dried
black liquor as a side product, and logistic aspects regarding the cost of
sending EFB and/or black liquor to farms, industrial users, or municipalities.
Once these limitations have been overcome with data survey and market study,
plants like both proposed scenarios might reach a feasible economic stage and
play an important role in transitioning towards a circular economy that
promotes sustainability. Thus, it is recommended that a more detailed
socio-economic analysis should as well be considered in a future study. The study's main conclusion may be presented in a
short conclusions section, which may stand alone. It should not repeat the
results but provide significant findings and contributions to the study.
The
first author would express sincere gratitude to the Indonesia Endowment Funds
for Education for providing scholarships to pursue PhD program at University of
Tsukuba. This research is also part of project by Research Center for
Chemistry, National Research and Innovation Agency (BRIN) supported by the
Indonesia Endowment Funds for Education (LPDP) – Ministry of Finance of the
Republic of Indonesia for research grant No. KEP-02/LPDP/LPDP.4/2022 of 2022.
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