Co-firing Of Coal Research Articles

Utilization of Palm Frond Waste as Fuel for Co-Firing Coal and Biomass in a Tangentially Pulverized Coal Boiler Using Computational Fluid Dynamic Analysis

Renewable energy sources are becoming increasingly crucial in the global energy industry and are acknowledged as a significant substitute for fossil fuels. Oil palm fronds are a type of biomass fuel that can be utilized as a substitute for fossil fuels in the combustion process of boilers. Co-firing (HT-FRD) is a beneficial technology for reducing exhaust gas emissions generated by coal-burning power stations. By utilizing computational fluid dynamics (CFD), this study has modeled and evaluated co-firing palm frond residue (HT-FRD) with hydrothermal treatment into a 315 MWe boiler. In the simulation, six different HT-FRD co-firing ratios, 0%, 5%, 15%, 25%, 35%, and 50%, were used to demonstrate the differences in combustion characteristics and emissions in the combustion chamber. The data indicate that HT-FRD co-firing can enhance temperature distribution, velocity, and unburned particles. All in all, co-firing conditions with 5–15% HT-FRD ratios appear to have the most favorable combustion temperature, velocity, and exhaust gas characteristics.

Effect of Potassium on the Co-Combustion Process of Coal Slime and Corn Stover

In this study, the combined combustion characteristics and gaseous product emissions of coal slime and corn stover were compared at different blending ratios. The TG-DTG curves indicate that the optimal performance is achieved when the corn straw blending ratio is 20%. Furthermore, the TG-FTIR coupling results demonstrated an increase in gas species as the blending ratio increased. The composition analysis of ash samples formed at various combustion temperatures using XRD and XRF indicated that a portion of KCl in the fuel was released as volatile matter, while another part reacted with Al2O3 and SiO2 components in the slime to form silica–aluminate compounds and other substances. Notably, interactions between the components of slime and potassium elements in corn stover primarily occurred within the temperature range of 800–1000 °C. These findings contribute to a comprehensive understanding of biomass and coal co-firing combustion chemistry, offering potential applications for enhancing energy efficiency and reducing emissions in industrial processes.

Numerical study on ammonia injection location of ammonia and low-rank coal cofiring in 1000 MWe ultra super critical carolina-type boiler

Global CO2 emissions from coal-fired power plants necessitate innovative solutions to reduce their environmental footprint. Ammonia cofiring has emerged as a promising solution for reducing CO2 emissions in these plants. The ammonia injection optimization is analyzed using computational fluid dynamics simulations in a 1000 MW Ultra Super Critical Coal Fired Power Plant, comparing four injection sites at a 20 % thermal energy cofiring ratio. Results indicated the bottom burner as the most effective location, achieving the lowest NOx emissions (102.20 mg/Nm3) compared to traditional coal-firing (131.78 mg/Nm3). A sensitivity analysis favored bottom and mid burner injections over equal distribution, leading to further investigations into varying injection locations and cofiring ratios (5%–60 %). Increased cofiring ratios decreased gross power output by 3.6 MW per percentage increase in cofiring, alongside shifts in flue gas properties and a complex NOx emission trend. Initially, NOx emissions decreased, with a 0.784 up to 20 % cofiring, but dramatically increased beyond, reaching a ratio of 3.744 at 60 % cofiring. This study reveals critical insights into emission management and highlights the need for improved derating strategies to mitigate acid corrosion risks, marking a significant step towards environmentally sustainable coal power generation.

Combustion characteristics on ammonia injection velocity and positions for ammonia co-firing with coal in a pilot-scale circulating fluidized bed combustor

Ammonia (NH3) co-firing with coal in thermal power plant offers a viable solution for reducing CO2 emissions. Optimizing the NH3 injection method is crucial to achieving comparable performance and pollutant emissions in NH3–coal co-firing compared to coal only combustion in a circulating fluidized bed combustion system. The impact of NH3 co-firing with coal on the injection velocity and location in related to the NH3 supply method was evaluated. Injection velocity was controlled by varying the number of ammonia supply ports and their heights (0.2 m and 1.8 m from the distributor). Injecting NH3 through one port at a high velocity of 2.4 m/s increases CO emissions while decreasing NO emissions due to the formation of a reducing environment. Conversely, utilizing two ports with low NH3 injection velocity of 1.2 m/s exhibited the opposite trend in CO and NO emissions, achieving the highest combustion efficiency without the formation of N-containing components. This injection velocity promotes better mixing of gases (air and NH3) and solids (bed materials and coal) without hindering coal combustion. Regarding greenhouse gases emissions, the part of CO2 emissions decreased by considering CO2 concentration and flue gas flow rate, while the part of N2O emissions significantly increased due to N-chemistry by > 5 times.

Comparative experimental study on the co-firing characteristics of water electrolysis gas (HHO) and lean coal/lignite with different injection modes in a one-dimensional furnace

Zero-carbon fuels (H2/NH3) replacing coal co-firing is a promising way to address carbon emissions. Hydrogen co-firing helps improve combustion stability at low loads and control pollutant emissions. This study used a safer water electrolysis gas (HHO) for the multi-coal co-firing adaptability test. The effects of HHO injection mode and flow rate on combustion intensity, flue gas emissions, and fly ash characteristics were investigated. The results showed that HHO and lean coal/lignite co-firing could significantly increase the combustion temperature. The maximum temperature increases after co-firing were 108 °C and 95 °C. As the HHO increased, the CO2 in lignite co-firing increased, and CO and unburnt carbon decreased, while the opposite results were observed for lean coal (LC). At the 2200L/h HHO co-firing, CO2 decreases by 14.46 % and 27.22 % for LC premixed co-firing (PC) and staged co-firing (SC). Compared to SC, PC is more conducive to promoting the complete combustion of coke. The NOX emissions of HHO/LC co-firing are lower than those of pure coal, reaching the lowest value of ∼ 9 ppm under SC. As the HHO increases, the NOX of Lignite-PC first increases and then slowly decreases, while Lignite-SC has the opposite effect. Although various NOX emission trends are observed under different conditions, the results are dominated by a common mechanism − the competition between NOX reduction caused by HHO gas and the increase in co-firing temperature on NOX generation. The NOX of SC is all lower than that of PC. The SO2 emission from the LC co-firing decreases with the increase of HHO, while the SO2 from lignite increases. The SO2 of LC-SC can be reduced from ∼ 142 ppm to 0 ppm. HHO gas injection inhibits the release and oxidation of sulfur in lean coal. The differences in coal types lead to different changes in SO2 of co-firing. HHO gas reduced the SO3 content of lignite fly ash by 38.01 %. The high-temperature reduction atmosphere promotes the decomposition of sulfates and increases SO2 emissions. HHO co-firing refines the particle size of fly ash. The ultra-fine and micron particle matter (PM) increases, and the content of PM>100μm in Lignite-SC decreased by 10.32 %.

Evaluating the potential of green hydrogen, ammonia and urea in Lao PDR energy transitions.

Abstract We report the results of a systematic evaluation of the redeployment of surplus hydropower electricity to produce green hydrogen (H2), ammonia (NH3) and urea (CH4N2O) in Lao PDR. Participatory system mapping (PSM) workshops convened across multiple Lao PDR ministries revealed both direct and indirect opportunities and risks as probable consequences of green H2, NH3 and urea production. Participants debated and prioritized green urea fertilizer to replace “grey” imports; coal co-firing; and fuel cells as the products that contribute to the opportunities and manage the risks identified by the PSM process. Techno-economic modelling indicates the levelized cost of urea (US$467/tonne) is competitive with Thai imports, associated with opportunities for trading carbon offsets. Carbon credits were not sufficient to offset the additional co-firing costs of coal generation, and fuel cells are a likely future enterprise. A targeted capacity building and training program was a central pillar of a systems-based dissemination strategy to develop necessary technical and planning skills and community and awareness raising. The collated research results represent an integrated foundation to draft the Lao PDR National green H2 and NH3 road map and action plan, and a cross-sectoral revision of energy transition development plans.

Progress on Biomass Coal Co-firing for Indonesia Power Plant

Abstract PT. PLN Indonesia Power (PLN IP) collaborated with other research institutions has conducted several studies to investigate the possibility of using biomass for co-firing with biomass in coal power plant. This review paper integrates results of the previous study results carried out by the authors. Biomass has some disguise disadvantageous such as low energy density, high alkaline metals, high volatile mater, handling difficulties, which may cause derating in power plant and some problem in the combustion facilities such as slagging, corrosion, abrasion, and agglomeration. The investigation carried out reveals that the use of multi-type biomass could eliminate the derating. The pre-treatment of the biomass such as drying and pelletizing could improve not only the energy density but also diminishing the slagging potential.

Influence of rice husk dosage on PM emissions during the co-firing of coal with refuse derived fuel

A self-designed drop tube furnace (DTF) was constructed to investigate the particulate matter (PM) emissions generated from blending 0–30 wt% refuse derived fuel (RDF) and 0–20 wt% rice husks (RH) with bituminous coal during co-firing. The physiochemical characteristics of PM were determined using XRD, XRF, and SEM-EDS, and the creation of the liquid components at varying temperatures was investigated using theoretical thermodynamic calculations based on fuel composition and combustion atmospheres. The results demonstrated that blending 0–30 wt% RDF with coal did not result in significant PM emissions. PM0.5 and PM2.5 yields declined by 31.5% and 39.5%, respectively, with the addition of 20 wt% RH. By solely adding RDF, more Ca-Al-Si and K/Ca-Si formed viscous surfaces or particle bodies that could capture Ca/K vapor released from the volatiles of RDF in the gas bulk. Si-rich and Al-Si species from coal were consumed and transformed into Na/K-Ca-Al-Si to enhance the production of the liquid phase by the abundant Si in the volatiles of RH. Two possible paths of mineral transformations during co-firing were discussed to prove that alkali metals and alkaline earth metals preferentially condensed on Si-rich and Al-Si species to form liquid substances and capture the vapor and grains in the gas bulk, rather than combining with nonmetallic elements to generate precursors for PM generation via the evaporation–condensation mechanism. This study contributes to the search for an efficient pathway to realize simultaneous waste utilization and greenhouse gas reduction.

Slagging tendency analysis and evaluation of biomass and coal during co-firing

Co-firing of biomass and coal may cause slagging and fouling and impact the operational lifespan of the boilers. In this paper, eucalyptus bark (EB) and four kinds of coal were used as raw materials, and the degree of slagging was experimentally investigated by scanning electron microscope (SEM), X-ray fluorescence (XRF), and X-ray diffraction (XRD). Moreover, the technique for order preference by similarity to ideal solution (TOPSIS) method and the entropy weight (EW) method were used to establish a slagging evaluation model E-TOPSIS. The results showed that the co-firing of EB and coal caused an increase in ash particle size, particle sintering, and adhesion. XRD analysis confirmed that EB promoted the reaction of calcium compounds with quartz and enhanced the diffraction intensity of muscovite, anorthite, and calcite. The evaluation results of the E-TOPSIS showed that the slagging tendency of EB, IC, and ICEB was severe, which is aligned with the experimental results, and proves the accuracy of this method. The research results can provide a reference for predicting the slagging tendency of biomass and coal during co-firing.

A techno-economic and environmental analysis of co-firing implementation using coal and wood bark blend at circulating fluidized bed boiler

The study aimed to explore the effects of biomass co-firing of coal using acacia wood bark at circulating fluidized bed (CFB) boiler coal-fired power plant with 110 MWe capacity. The analysis focused on main equipment parameters, including the potential for slagging, fouling, corrosion, agglomeration, fuel cost, and specific environmental factors. Initially, coal and acacia wood bark fuel were blended at a 3% mass ratio, with calorific values of 8.59 MJ/kg and 16.59 MJ/kg, respectively. The corrosion due to chlorine and slagging potential when using wood bark was grouped into the minor and medium categories. The results showed that co-firing at approximately 3% mass ratio contributed to changes in the upper furnace temperature due to the variation in heating value, high total humidity, and a less homogeneous particle size distribution. Significant differences were also observed in the temperature of the lower furnace area, showing the presence of a foreign object covering the nozzle, which disturbed the ignition process. A comparison of the seal pot temperature showed imbalances as observed from the temperature indicators installed on both sides of boiler, with specific fuel consumption (SFC) increasing by approximately 0.17%. During the performance test, the price of acacia wood bark was 0.034 USD/kg, resulting in fuel cost of 0.023355 USD/kWh, adding 0.061 cent/kWh to coal firing cost. Despite co-firing, the byproducts of the combustion process, such as SO2 and NOx, still met environmental quality standards in accordance with government regulations. However, a comprehensive medium- and long-term impact evaluation study should be carried out to implement co-firing operations using acacia wood bark at coal-fired power plant. Based on the characteristics, such as low calorific value, with high ash, total moisture, and alkali, acacia wood bark showed an increased potential to cause slagging and fouling.

A novel swirl burner with coal co-firing ammonia: Effect of extension length of the dual-channel ammonia pipe on combustion and NOx formation

The coal/ammonia co-firing technology for thermal power generation is a feasible method to effectively reduce CO2 emissions. However, the easy formation of NOx is one of the challenges faced by this technology owing to the high nitrogen content in ammonia. This study proposes a novel swirl burner with a scalable dual-channel ammonia pipe, and evaluates the combustion and NOx formation under different extension lengths of the dual-channel ammonia pipe (i.e., 0 m, 0.4 m, 0.8 m, 1.0 m, 1.2 m). The results show that the extension length of the dual-channel ammonia pipe significantly affects the flow, combustion, and NOx formation. When the extension length of the dual-channel ammonia pipe is above 0.8 m, the ammonia stream can completely penetrate the internal recirculation zone into the high CO environment, which contributes to promoting the ammonia pyrolysis and inhibiting the ammonia oxidation to form NOx. NOx emissions significantly decrease from 846 ppm to 146 ppm as the extension length of the dual-channel ammonia pipe from 0 m to 0.8 m, but change slightly as further increases from 0.8 m to 1.2 m. The carbon content in fly ash decreases from 4.53% to 3.40% as the extension length of the dual-channel ammonia pipe increases from 0 m to 1.0 m. Still, it increases from 3.40% to 3.70% as the extension length of the dual-channel ammonia pipe rises to 1.2 m. Overall, it is reasonable to set the extension length of the dual-channel ammonia pipe at 1.0 m in this studied condition, which can obtain low NOx and low carbon content in fly ash.

Experimental study of NH3 and coal Co-firing in a CFB and its nitrogen conversion

This study conducted co-firing experiments of NH3 and coal in a circulating fluidized bed combustor. The effects of NH3 co-firing ratio and combustion atmosphere of NH3 addition position on temperature, flue gas emissions, carbon content of the fly ash, NH3 content in fly ash were investigated. Results showed that NOx and N2O emissions increased with NH3 ratio increasing when adding NH3 in the reducing zone. A lower NOx increment was found within 0∼20 % NH3 ratio, increasing by 0.6 times compared to coal combustion. The NH3 content in fly ash was 2.74 mg/kg when NH3 ratio was 10 %. Compared to the reducing zone, adding NH3 into the oxidizing zone promoted the generation of more NOx and N2O, and simultaneously was detrimental to the burnout of NH3 and CO. Based on these findings, NH3 added in the reducing zone emerges as an optimized choice when NH3 and coal are co-fired in circulating fluidized bed. Extending the retention time of NH3 in the reducing zone was beneficial for controlling NOx and N2O, as well as promoting the burnout of NH3 and CO. Furthermore, fuel-N conversion analysis showed that over 96 % fuel-N was converted into harmless N2 when NH3 ratio exceeds 10 %.

Experimental study on the co-firing and NOx emission characteristics of bituminous coal and its medium temperature pyrolysis char

To address the issues of ignition difficulty, incomplete burnout, and high NOx emissions during coal char combustion in industrial applications, a series of co-firing experiments involving bituminous coal and its medium-temperature pyrolysis char were conducted using a micro fluidized bed analysis system. The experiments explored co-firing behaviors and NOx emission characteristics for five different fuel blending ratios in an environment with 21 % oxygen concentration, across temperatures between 923 K and 1223 K. The study delved into the synergistic effects of coal and char co-firing, as well as the influence of combustion temperature and fuel blend ratio on the co-firing efficiency and NOx emissions. The results show a synergistic effect in the co-firing of bituminous coal and char, influenced by reaction temperature and coal-to-char blend ratio, which evolves as combustion progresses. In the 923–1073 K range, initial coal addition to the blend enhances reactivity. However, as the reaction advances or coal content exceeds 75 %, this synergy shifts to an inhibitory effect. At temperatures above 1023 K, increased proportions of coal in the blend are associated with improved burnout rates, especially when the coal content is at or above 50 %. Moreover, at a combustion temperature of 1123K, there is a marked decrease in nitrogen oxide emissions, with coal blend ratio of 25 % and 50 % showing particular efficacy in reducing these emissions. These results provide valuable insights for the efficient and clean utilization of coal char in industrial combustion processes.

Experimental study on the influence of operating parameters on NOx and N2O emissions during co-firing of NH3 and coal in a CFB

Co-firing NH3 in a circulating fluidized bed (CFB) boiler holds promise as a technology for reducing CO2 emissions, yet NOx and N2O emissions remain a concern, and they are influenced by operation parameters. This study investigated the effect of NH3 co-firing ratio, operation oxygen concentration, bed temperature, and primary air fraction on NOx and N2O emissions in a CFB combustor. NOx and N2O concentrations along the furnace height were measured. The results indicated that the emissions of NOx and N2O increased when NH3 co-firing ratio increased. Their generation is mainly concentrated in the vicinity of the secondary air inlet. Elevating oxygen concentration facilitated NOx and N2O formation, in which N2O is more sensitive to oxygen. A 5 % operation oxygen concentration proved advantageous for limiting NOx and N2O emissions, as well as promoting NH3 burnout. Temperature exerted a greater influence on promoting NOx formation compared to operation oxygen concentration. As the primary air fraction increased, NOx initially decreased before rising, while N2O exhibited minimal change. A primary air fraction of approximately 0.58 might be a suitable choice for NOx emission control.

Review on Mercury Control during Co-Firing Coal and Biomass under O2/CO2 Atmosphere

Combining biomass co-firing with oxy-fuel combustion is a promising Bioenergy with Carbon Capture and Storage (BECCS) technology. It has the potential to achieve a large-scale reduction in carbon emissions from traditional power plants, making it a powerful tool for addressing global climate change. However, mercury in the fuel can be released into the flue gas during combustion, posing a significant threat to the environment and human health. More importantly, mercury can also cause the fracture of metal equipment via amalgamation, which is a major risk for the system. Therefore, compared to conventional coal-fired power plants, the requirements for the mercury concentration in BECCS systems are much stricter. This article reviews the latest progress in mercury control under oxy-fuel biomass co-firing conditions, clarifies the impact of biomass co-firing on mercury species transformation, reveals the influence mechanisms of various flue gas components on elemental mercury oxidation under oxy-fuel combustion conditions, evaluates the advantages and disadvantages of various mercury removal methods, and finally provides an outlook for mercury control in BECCS systems. Research shows that after biomass co-firing, the concentrations of chlorine and alkali metals in the flue gas increase, which is beneficial for homogeneous and heterogeneous mercury oxidation. The changes in the particulate matter content could affect the transformation of gaseous mercury to particulate mercury. The high concentrations of CO2 and H2O in oxy-fuel flue gas inhibit mercury oxidation, while the effects of NOx and SO2 are dual-sided. Higher concentrations of fly ash in oxy-fuel flue gas are conducive to the removal of Hg0. Additionally, under oxy-fuel conditions, CO2 and metal ions such as Fe2+ can inhibit the re-emission of mercury in WFGD systems. The development of efficient adsorbents and catalysts is the key to achieving deep mercury removal. Fully utilizing the advantages of chlorine, alkali metals, and CO2 in oxy-fuel biomass co-firing flue gas will be the future focus of deep mercury removal from BECCS systems.

A Determination Method for the Biomass Lower-Calorific-Value-Based Blending Ratio in Co-Firing Power Plants

The accurate measurement of the biomass lower-calorific-value-based blending ratio (BLBR) is the premise and key to scale development of the power generation technology from co-firing of biomass and coal. However, existing determination methods of BLBR are less accurate, which has impeded the scale utilization of the co-firing technology of biomass and coal. To accurately determine the BLBR, this research proposed a flue gas sampling system suitable for determining BLBR through 14C quantitative analysis and established a medium-scale experimental platform for BLBR determination. In addition, predictive models for the lower calorific values of coal and biomass fuels were built and the BLBR calculation model for co-firing power plants was deduced. Furthermore, experimental verification of the BLBR determination was also conducted. The results show that the lower calorific values of coal and biomass fuels are highly linearly positively correlated with the carbon content. The relative errors of the established prediction models for lower calorific values of biomass and coal are separately lower than 5% and 8%. The results indicate that the proposed BLBR determination method is accurate.

Prediction of the Slagging and Fouling of Indonesian Coal with Hard Wood from Central and East Java

Indonesia as an agricultural country has abundant biomass potential, especially wood waste in Java. The prospect of co-firing is considered ideal to overcome the problem of coal use in boilers. This is also in line with supporting the Indonesian government program in increasing the use of renewable energy. Samples of coal co-firing with wood waste from Central Java and East Java were selected for this study. Furthermore, blending between coal and wood biomass from Central and East Java with a composition ratio of (25%:75%) and (50%:50%). Furthermore, it is predicted based on the risk tendency of slagging and fouling. The risk of slagging, fouling, abrasion, and corrosion with theoretical index. In general, increasing the composition of coal blending with hardwood increases the tendency of slagging and fouling. However, blending coal with hardwood from Central Java at a mixture of (25%:75%) can be recommended because it has a low risk of slagging and fouling.

Process Optimization and Robustness Analysis of Ammonia–Coal Co-Firing in a Pilot-Scale Fluidized Bed Reactor

A computational fluid dynamics (CFD) model was coupled with an advanced statistical strategy combining the response surface method (RSM) and the propagation of error (PoE) approach to optimize and test the robustness of the co-firing of ammonia (NH3) and coal in a fluidized bed reactor for coal phase-out processes. The CFD model was validated under experimental results collected from a pilot fluidized bed reactor. A 3k full factorial design of nine computer simulations was performed using air staging and NH3 co-firing ratio as input factors. The selected responses were NO, NH3 and CO2 emissions generation. The findings were that the design of experiments (DoE) method allowed for determining the best operating conditions to achieve optimal operation. The optimization process identified the best-operating conditions to reach stable operation while minimizing harmful emissions. Through the implementation of desirability function and robustness, the optimal operating conditions that set the optimized responses for single optimization showed not to always imply the most stable set of values to operate the system. Robust operating conditions showed that maximum performance was attained at high air staging levels (around 40%) and through a balanced NH3 co-firing ratio (around 30%). The results of the combined multi-optimization process performance should provide engineers, researchers and professionals the ability to make smarter decisions in both pilot and industrial environments for emissions reduction for decarbonization in energy production processes.

Potential Torrefaction of Tropical Forest Fruits Waste

Biomass torrefaction can improve the quality of raw biomass as fuel. Tropical forest fruit waste that is not managed properly will become waste that contributes to increasing greenhouse gas emissions. Conversion of tropical forest fruit waste into biomass fuel by torrefaction can be used as coal co-firing. In this research, torrefaction was carried out on the biomass from the cocoa pod shell, coffee husks, and mangosteen pod shell. The samples used in this study came from tropical forest fruits in Lampung Province. Samples were chopped and dried using the hot sun. The samples were then torrefied in a tubular reactor at temperatures of 250, 275, and 300°C and their calorific values were tested. Torrefaction at 275°C has increased the calorific value of tropical forest fruit waste to exceed the calorific value of sub-bituminous A. Torrefaction of tropical forest fruit waste has the potential to be used as fuel for co-firing coal in power plants. Thus, it can indirectly reduce the rate of CO2 emissions from power generation and waste accumulation. In addition, it also has the potential to become a competitive sustainable export commodity.

Optimizing biomass supply for cofiring at power plants to minimize environmental impact: A case of oil palm empty fruit bunches in West Java

This study addresses the supply flow optimization to reduce global warming in a cofiring system, using the example of oil palm empty fruit bunches converted into pellets for use in power plants in Indonesia. Four oil palm mills, seven pellet plants and five coal power plants in the West Java Region were considered in this study to select the optimal supply chain. The study was performed using a life cycle assessment (LCA) for evaluating impact of single firing of coal and linear programming (LP) for optimizing the impact reduction of cofiring of coal and pellets. Our study indicates that the optimal environmental reduction can be achieved by constructing six of the seven pellet plants, which can substitute up to 1 % of the coal supply in five power plants. Accordingly, the emissions could be decreased by an average of 0.018 kg CO2eq/kWh for the power plants, which is equal to 0.2 Mt CO2eq/y or a 1.57 % reduction per year. By varying the emission factor of the pellet plants, our analysis showed a tolerable range in which the supply would not be affected. The sensitivity analysis at a 1 % cofiring rate showed that the increase in biomass supply from the oil palm mills had the highest reduction, whereas the reduction in transportation emissions provided much less impact. By adjusting the cofiring rate, the impact would not change after the 3 % cofiring rate because of the limited availability of Empty Fruit Bunch (EFB) feedstock. However, if sufficient supply could be provided, the environmental impact would be further reduced significantly. Furthermore, the scenario expansion indicated that only three pellet plants would be required for the minimum economic scale of production, although the environmental impact increased by 0.47 % compared to using six pellet plants. Therefore, this study can be used to determine the optimal supply chain scenarios by constructing an appropriate number of economically feasible pellet plants according to the biomass demand and cofiring rate of the power plant.