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In this work, a feasibility study was conducted with two purposes: i) estimates carbon dioxide emission and ii) identifies potential carbon dioxide (CO2) emission reduction through implementation of cleaner production (CP) strategies in a palm oil mill. The results indicated that the largest sources of CO2 in the studied plant were empty fruit bunch dumping (57%), followed by wastewater effluent generation (39.7%), and emission from the boiler (3%). The total CO2 emission was approximately 2.03 t CO2/t CPO produced. Co-composting system, biogas capture and biomass combustion were found to be options that could be implemented for significantly reducing CO2 up to 97%.
Application of new palm oil milling technology especially in the sterilization and clarification process was also found to be able to minimize the utility costs due to increased energy efficiency. The study concluded that application of CP strategies could reduce the total CO2 emission in a palm oil mill.
Abbreviation:
The economic development in Malaysia is largely influenced by the crude palm oil (CPO) industry.
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This can be clearly seen through the tremendous increase in the number of palm oil mills in Malaysia. In 2011, there were 426 operated mills (Wang et al., 2015) compared to only 149 mills in 1980.
CPO mills use significant amount of utilities and energy during the production process, thus generated waste and emission. For a typical palm oil mill, the main material inputs are fresh fruit bunch (FFB) from plantations, water for the process, steam generation, fuel and electricity. Although there are occasions when the power from the grid and diesel are needed as a boiler start-up fuel, the mills can still be considered over self-sufficient on energy. Electricity and steam for the mills are commonly produced from the use of fibres and shells as fuel (co-products of the CPO extraction process) (Subramania et al., 2008).
The process outputs from palm oil milling are CPO, palm kernels, fibres, shells, empty fruit bunch (EFB) and palm oil mill effluent (POME). Shells and fibres are considered valuable co-products because they are readily used as a fuel for electricity and steam production in the mills. EFB can be treated as solid wastes or co-products, which can be used for mulching or energy generation. POME is wastewater with high organic content and therefore best treated by anaerobic treatment (Yahaya & Lau Seng, 2013). It is heavily polluted with biodegradable organic materials, with a typical Chemical Oxygen Demand (COD) value of 51,000 mg/l (Bala et al., 2014) and it needs treatment prior to discharge.
Methane (CH4) is a greenhouse gas with a high global warming potential (GWP) and its release from anaerobic ponds is a major issue in palm oil production. Even though CH4 production is an environmental concern, it can also be considered a major source of biogas. Process outputs that have adverse environmental impacts include treated wastewater, CH4 from POME treatment and flue gas from the boiler. The main problem associated with using biomass is high concentration of particulate matters in the flue gas (Yusoff & Hansen, 2007). Carbon dioxide (CO2) from POME treatment and burning of fibres and shells in energy production can be considered CO2-neutral. FFB have annual crop yield and the carbon stored in products and co-products are released to atmosphere within a year. Therefore, the carbon balance in the atmosphere is neutral.
In 2007, palm oil waste emitted approximately 2.5 million t of CO2. It has also been reported that palm oil mills are fingered by climate change authorities as the second largest source of CH4 generator in the country, next to landfills (The Star, 2012). The CO2 emission rate for EFB dumping is approximately 245 kg CO2/t FFB processed. Based on the research by Stichnothe & Schuchardt, (2010), this is a conservative figure as the emission factor used to calculate the emission rate is based on 5% anaerobic conditions. It is estimated that there are 130 kg CO2/t FFB processed for POME in open ponds. The total emission for palm oil processing is estimated to be around 1.9 t CO2/t CPO produced. Therefore, the palm oil mill emission in Malaysia in 2008 was estimated to be around 33.63 million t CO2 per annum with CPO production of around 17.7 million in the same year. However, studies conducted by Malaysian Palm Oil Board (MPOB) in 2007 indicated that there was an emission of 0.97 t CO2/t CPO produced without considering emissions from EFB, which translated to 17.2 million t of CO2/y (Choo et al., 2007).
The palm oil industry has come under pressure to maintain low emissions if a large amount of CPO or bio-diesel from CPO is to be exported to western countries as a renewable energy source. The requirement that CPO production has to be sustainable with less emissions, no environmental pollution, implementation of recycling systems, efficient utilization of energy sources, minimization of soil erosion, less impacts on rain forests and etc. will arise in no time. Considering these aspects, palm oil mills have to implement new environmental friendly treatment technologies. It is just a matter of time before sustainability certification, which requires carbon footprint calculation, becomes mandatory in Malaysia for export of palm oil to other countries.
Cleaner production (CP) can be used as an approach to address environmental problems and increase energy efficiency within palm oil mills. Some of the current approaches to handle this problem are by analysing the existing environmental performance of the mills based on waste generation, environmental impact, adoption of clean technology and waste exchange. Then, possible solutions can be identified.
In this study, the assessment of the available clean technology options and the improvement of environmental performance were executed on the basis of CP. The areas identified within a palm oil mill that require attention could be categorized into two broad categories which were by-products in the form of waste that generate emissions without treatment and the palm oil milling processes.
Literature shows that the production process can be modernized for optimization purposes and thus new technologies have been developed for palm oil mills (Loh, 2010). These technologies include new sterilization processes that do not generate condensate that is commonly generated in conventional autoclave sterilization. The conventional sterilization process creates condensate as much as 0.20 m³/t FFB. Formation of condensate can be avoided almost completely with this new sterilization technique. Oil separation with zero dilution water can also avoid formation of condensate. The existing conventional oil recovery process at the palm oil mills involves clarification and separation process. The conventional process creates 0.45 m³ of wastewater for every ton of FFB. However, addition of dilution water is not necessary by using a new oil recovery technology, for example ECO-D system by Westfalia Company and this reduces effluent by up to 0.25 m³/t FFB.
It is clear that modernization of the production process has a significant impact on the absolute and related amount of POME and water in POME (m³/t FFB), composition (dry matter content, concentration of nutrients, liquid or sludge), utilization (type of biogas plant, size of composting plant) and treatment cost of POME. With increased efficiency of the sterilizer and stripping process, less energy is consumed for steam generation and operation of equipment, and the EFB generated also has less wastage. In recent years, palm oil mills have applied various technologies to improve POME treatment and reduce CH4 emissions. These include technologies for converting biogas into electricity or heat. Biogas capture technologies are also considered as a clean development mechanism (CDM) strategy, having the potential of generating significant revenues through sales of carbon credits. The efficiency of emission reduction through biogas capture varies widely depending on the technologies used (Chin et al., 2013).
Another alternative to improve POME treatment is to co-compost with EFB to generate high-quality compost with a good C: N ratio, which will significantly reduce POME. Schuchardt et al., (2007) demonstrated that this technology has the potential to significantly reduce POME. Other technologies, which contribute to reducing CH4 emissions from POME, include de-nitrification technologies and decanters prior to pond treatment that is able to remove a significant amount of suspended solids. No literatures are found on the practical applications and efficiency of these technologies. It is also difficult to obtain quantitative data on emission reduction efficiency using these technologies.
One of the solid residues from palm oil mills is EFB. This can be used as mulch in plantations, composted, landfilled or utilized as a biofuel, of which each of them has specific emission characteristics. Out of these applications, using EFB as mulch is most commonly practiced as it can potentially reduce carbon emission, reduce need for artificial fertilizers, improve carbon sequestration in the soil and increase soil organic matter. However, no quantitative data on the emission are available. Landfilling of EFB leads to CH4 emission due to anaerobic decomposition processes. Though mulching also has emissions, the scale of the impact is smaller than that of landfilling or dumping.
Due to significant establishment of palm oil mill in Malaysia, this study was conducted with the objective to demonstrate that CP strategies can help the industry to improve its environmental and economic performance. The feasibility of using CP strategy to reduce CO2 emission in a palm oil mill in Malaysia was studied. This study can serve as a local case study, helping future researchers and decision makers in development of the CPO industry.
The data collection in this study was done using four sequential steps, which included preliminary auditing, detailed auditing, generating potential options and feasibility studies. Firstly, a walk-through audit was conducted to observe the plant layout, mainly the location of the main processing areas, facilities and waste storage. The preliminary visit allowed a thorough understanding of the process flow and to ascertain types of data available. The preliminary issues were also identified. A detailed audit was then conducted considering every process step and activity of the plant. The assessment was conducted in the processing areas, where materials handling, materials consumption and waste generation together with their characteristics were studied.
Electrical and thermal energy utilization was analysed to evaluate the current operating efficiencies and methods to minimize the loss. Calorific values (CV) and moisture contents of the key waste streams of the plant were analysed in order to determine energy inputs and evaluate the possibilities of operating the plant self-sufficiently in terms of energy. Possibilities of modifying the physical state of raw materials, recycling utilities and waste materials from the process were assessed during the audit. Other than reviewing the inventories on material and utility purchases, walk-through observation and communication with employees were also the major tools used in the audit. The recommendations or comments from the employees on CP improvements were considered important in identifying and prioritizing the final CP options.
Technical feasibility and environmental sustainability were the main evaluating criteria for selecting the key CP options. Information was also extracted from similar researches on palm oil processes and default values available in literatures for additional data required for carbon calculation purposes.
The feasibility of implementing CP strategies in a palm oil mill in Sabah, Malaysia was studied. The plant utilized conventional palm oil milling technology with a capacity of 60 t/h. Generally, the production involved a 7-step process, which included sterilization, stripping, digestion, pressing, clarification, purification, drying and storage. The first step of the CPO production involved sterilization of FFB. Steam produced by a biomass boiler was used in this step. Electricity generated via the biomass boiler and diesel was used for the boiler start-up. The condensate generated during the sterilization process contributed to POME.
The electricity generated was used for rotating the drums that strip fruits from the sterilized FFB during the stripping process. This was also the process where EFB was produced and disposed at an open area. Electricity was consumed during the digestion and pressing processes where it was required for the rotating shaft within the digester and screw press, which were used to extract oil. The decanter consumed electricity and the sludge produced was also a part of POME. Electricity was used for the drying process to produce kernels.
The CO2 emission for FFB processing from four main sources, namely total plant energy consumption, boiler flue gas, biogas generated from POME and EFB dumped in landfills or disposal sites was calculated. Water consumption was not included in this study, as it did not affect the COD level of POME. The transportation of FFB from the plantation location and transportation of EFB to landfills were not included as the distance was less than 2 km. Energy used in the plant consisted of power and heat generated by the boiler and turbine system that utilized a combination of diesel and biomass as fuel. Therefore, emission from the diesel used and flue gas from the boiler were included in the emission calculation for power and heat generation.
For the calculation of CO2 emission, default emission factors mainly from Intergovernmental Panel of Climate Change (IPCC) were used as they were in line with the guidelines adopted for this study. The focus of the calculation was on direct emission and default emission factors in accordance with the CO2 generated based on the types of waste produced and fossil fuel used. The CH4 content was multiplied by 21 as per the GWP of the gas in order to determine the CO2 equivalent for the CH4 generated. The formula used for quantifying emissions from diesel consumption according to the IPCC methodology is written as Equation (1):
CO2 Diesel (t) = M Diesel x EF Diesel (1)
Where:
M Diesel = Amount of diesel consumed (t)
EF Diesel = Emission factor of diesel (3.19 t CO2/t diesel)
Whereas, POME is treated via an open ponding system and thus the emission of POME treatment is based on this treatment system. The emission is calculated by multiplying the annual average COD concentration entering the open pond with the emission factor given by IPCC. Hence, the formula used for this study according to UNFCC can be written as Equation (2):
CO2 POME (kg) = M POME x COD POME x BO POME x MCF POME x GWP CH4 (2)
Where:
M POME = Volume of POME treated (m3)
COD POME = COD concentration of POME (kg/m3)
BO POME = Methane producing capacity of POME (0.21 kg CH4/kg COD)
MCF POME = Methane Correction Factor for POME treatment (0.8)
GWP CH4 = Global Warming Potential for methane (21)
In this study, the emission of EFB was based on the existing situation in which the EFB was disposed via dumping. As there were limitations in terms of data collection for the parameters required to determine the exact emission stemming from EFB dumping, the calculation was largely dependent on values provided by literatures. The emission was calculated by multiplying the annual FFB processed with the emission factor based on Stichnothe & Schuchardt, (2010). Hence, the formula used for this study can be written as Equation (3):
CO2 EFB (t) = M FFB x EF FFB (3)
Where:
M FFB = Amount of FFB processed (t)
EF FFB = Emission factor of FFB (0.245 t CO2/t FFB processed)
The emission from flue gas was quantified based on the amount of CO2 generated from the boiler fuel, per ton of CPO produced. As there were limitations in terms of data collection for the stack flue gas, the calculation was mainly based on values available in literatures. The gas emission was calculated by multiplying the averaged annual production of CPO with the emission factor. Based on the studies conducted by Subramania et al., (2008), it was estimated that approximately 60 kg of CO2 was generated per ton of CPO produced.
Analysis of the cleaner production audit findings show that for a total of 343,940 t of FFB processed to produce 72,227 t of CPO annually, 75.5 t of diesel were consumed for generating electricity in the plant, while 226,312 m3 of POME and 45,697 t of EFB were generated from the processes. Table 1 shows the summary of CO2 emission produced in the palm oil mill. Based on the above calculation, the total emission was approximately 2,029 kg CO2/t CPO produced. The sources of CO2 emission and the respective percentages are illustrated in Fig. 2. It clearly shows that the major contributor to CO2 emission was EFB dumping (57%). Emission from POME was less than half the total emission whereas emission from diesel consumption and boiler was almost negligible.
The emission from POME in this study was also similar to the values found in the literatures (ISCC, 2011). Therefore, CP strategies focusing on solid and liquid wastes from CPO processing were emphasized compared to diesel consumption optimization. However, it should also be noted that most palm oil mills in Malaysia are practicing EFB mulching and thus emission of EFB might not be indicative of the current scenario in Malaysia (Hansen et al., 2010). IPCC states that about 14 - 180 kg CO2/t CPO were generated from EFB mulching which is much lesser than the value obtained in this study, which was 1,160 kg CO2/t CPO produced. Therefore, by considering mulching as the common scenario in Malaysia and using the maximum value of 180 kg CO2/t CPO for mulching, a total emission of 1.03 kg CO2/t CPO was estimated. This value was also considerably closer to the CO2 emission estimation by MPOB (0.97 kg CO2/t CPO).
Table 1: Summary of CO2 Emission Quantification
| Source of Emission | CO2 Emission (kg CO2/t CPO Produced) |
|---|---|
| Diesel Consumption | 3.3 |
| POME Generated | 805.2 |
| EFB Dumping | 1,160 |
| Boiler Flue Gas | 60 |
| Total | 2,028.5 |
Composting is an aerobic process and it requires presence of oxygen. In the presence of oxygen, microorganisms including bacteria and fungi break down organic matters into simpler substances. The effectiveness of the composting process is influenced by the environmental conditions present within the compost (temperature, moisture, organic matter, oxygen and the size and activity of microbial populations). It consists of co-composting of EFB, a solid waste generated during the palm oil extraction process that is normally left to decay anaerobically at the disposal site along with POME that is treated in the anaerobic open ponds.
Co-composting prevents production of CH4 associated with anaerobic decomposition of EFB and POME. During co-composting, wastewater from the plant is added to the composting process to maintain the moisture level throughout the process and provide additional nitrogen that increases the production rate of matured compost. The EFB and POME composition render the compost sufficiently rich in nutrients to partly substitute chemical fertilizers traditionally needed in plantations. Based on literatures, co-composting can significantly decrease CH4 emission from both solid and effluents. As shown in Fig. 3, there will be a 97% reduction in GWP if co-composting is used for waste management.
Furthermore, co-composting also produces fertilizers high in nutrient content that can be used in the plantations as a replacement of inorganic fertilizers. This can be for on-site consumption or sold for additional revenue. In addition, there is a palm oil plant utilizing co-composting through incentives gained as a CDM project in Malaysia. The project utilizes EFB and POME generated by an adjacent palm oil plant to generate compost to be used at nearby plantations. This reduces CH4 that can be produced through mulching of some EFB, disposal of EFB in unmanaged landfill sites and anaerobic POME treatment lagoons. It also reduces usage of fertilizers and operating cost of the palm oil mill. Co-composting is expected to achieve an annual CO2 emission reduction of 120,000 t.
Another option that can be considered for effective waste management is separate treatment of POME and EFB. Biogas generated during anaerobic digestion of POME can be effectively captured and treated to be used as an alternative source of energy within the palm oil plant or sold. The commonly used biogas capture technologies are enclosed digester tanks or enclosed lagoons. Therefore, based on the calculated CO2 emission from POME of the plant, a 2 MW biogas plant could be set up to cater for the energy needs of the palm oil plant or sold to grid. Based on the studies conducted by Hansen et al., (2010), adding a small percentage of EFB to POME digestion yielded more biogas. The remaining EFB can be used to generate additional energy by an additional biomass power plant. Although this involves combustion of EFB, it has been found that emission from EFB incineration only causes a 4% drop in the potential emission reduction (Hansen et al., 2010).
There are 5% of palm oil plants in Malaysia that are implementing this technology currently. However, in most cases, either one technology is used as opposed to both in combination. One such CDM project is the Prolific Yield biomass energy plant. This plant has switched from using grid-connected electricity to produce its own electricity using EFB as a combustion fuel with excess electricity being sold to grid. The CO2 reduction achieved is around 78,000 t CO2 per annum for both replacement of grid connected electricity usage and also CH4 reduction using EFB as a fuel.
In 2010, the project had an internal rate of return (IRR) of 7.7% with CDM revenue, which was higher than the basic lending rate (BLR) of 5.6% at that time (BNM, 2010). With the introduction of sustainable energy development authority and the new tariffs of 0.10 USD/kWh, there are even more opportunities for financial gain for the plant through selling electricity to grid through renewable energy means. As for the biogas generation from POME, there is a palm oil plant currently utilizing this technology successfully in Malaysia, registered as a CDM project too. This project involves treatment of POME by installing a closed continuous-flow stirred tank anaerobic digester and biogas captures system. Biogas captured in the closed anaerobic digester is utilized for on-site electricity and sold to grid.
The CO2 reduction through biogas capture is around 47,651 t per annum. Through the sale of electricity to grid, the plant also managed to increase its revenue by around 710,480 USD per year at a tariff of 0.05 USD/kWh. With the current tariff increased up to 0.10 USD/kWh, this revenue will be doubled annually. Furthermore, through CDM incentives, the project has also achieved IRR of 15.5%, which is much higher than the respective BLR. At a CV of 50 MJ/kg, CH4 released from POME generated/t of CPO can produce 220 kWh of electricity at 40% gas engine efficiency (Hansen et al., 2010). For the plant that was studied in our study, if 50% of the electricity generated was sold, this translated to approximately 710,480 USD in profits. Thus, the potential CO2 reduction using this option could be around 132,851 t CO2 annually.
Apart from waste management, there are other areas for improvement in the palm oil milling process. The impact from fossil fuel usage in the studied plant was not significant, but potential reduction was possible through substituting diesel with renewable energy generated through biogas or biomass combustion. Besides, many new technologies in the area of sterilization and stripping have been introduced. Improved sterilizers lead to reduction of overall steam usage and water consumption. Besides, increased efficiency of softening and stripping of FFB helps reduce energy demand and wastage along with EFB. It is proposed that new continuous sterilization technology and zero dilution water for clarifying and separation method are to be used for reducing overall water consumption (Sivasothy et al., 2006). This will be reflected in increased COD loading in the same amount of POME and reduced auxiliary energy consumption.
This paper presents the evaluation of potential CP strategies in reducing CO2 emission in a palm oil mill. The result shows that approximately 2,029 kg CO2 were generated for producing 1 t of CPO, with EFB dumping being the main source of CO2 generation. Three potential CO2 reduction strategies were suggested for the studied plant. A co-composting system utilizing a combination of EFB and POME could potentially reduce the overall CO2 emission to 93 kg CO2/t CPO produced. Besides, biogas captured from POME and EFB combustion could potentially reduce 92% of total CO2 emission. Subsequently, the CO2 emission could be reduced to 160 kg CO2/t CPO produced. Increasing the energy efficiency of the processing equipment and substitution of diesel with renewable energy also could reduce the overall CO2 emission by 90%. The result of this study is a good indicator of the main sources of CO2 in a typical palm oil processing plant in Malaysia. Implementation of the proposed CP strategies is recommended for other palm oil mills.
Reducing Carbon Dioxide Emissions in Palm Oil Mills through Cleaner Production Strategies. (2024, Feb 22). Retrieved from https://studymoose.com/document/reducing-carbon-dioxide-emissions-in-palm-oil-mills-through-cleaner-production-strategies
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