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Cradle to grave Life Cycle Assessment of Lebanese biomass briquettes
Journal Pre-proof Cradle to grave Life Cycle Assessment of Lebanese biomass briquettes
Sabine Saba, Makram El Bachawati, Mike Malek PII:
S0959-6526(19)34721-3
DOI:
https://doi.org/10.1016/j.jclepro.2019.119851
Reference:
JCLP 119851
To appear in:
Journal of Cleaner Production
Received Date:
13 June 2019
Accepted Date:
21 December 2019
Please cite this article as: Sabine Saba, Makram El Bachawati, Mike Malek, Cradle to grave Life Cycle Assessment of Lebanese biomass briquettes, Journal of Cleaner Production (2019), https://doi.org/10.1016/j.jclepro.2019.119851
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier.
Journal Pre-proof
Cradle to grave Life Cycle Assessment of Lebanese biomass briquettes Sabine Saba1, Makram El Bachawati2, Mike Malek1 1University
of Balamand, Institute of the Environment, North Lebanon, PO Box: 100-Tripoli, Lebanon 2University of Balamand, Chemical Engineering Department, El Koura, North Lebanon, PO Box: 100Tripoli, Lebanon Co-authors e-mail address: [email protected]; [email protected] Corresponding author e-mail address: [email protected]
Abstract The bioenergy sector is showing a recent development in Lebanon, a Mediterranean country, where the valorization of forestry and agricultural waste through briquetting consists one of the mostly applied and targeted applications. This study aims at analyzing the life cycle environmental impacts of biomass briquettes produced from olive pruning residues and used for heating purposes in traditional Lebanese stoves. The biomass briquettes are mainly introduced as a replacement for the light fossil fuels widespread used in similar stoves for the same purpose. Consequently, this paper also extends the literature-found comparison of the consumption phases between biomass briquettes and light fossil fuels to a comparative gateto-gate LCA of these products. For the briquette itself, the results indicate that the "consumption" life cycle stage is the one that contributes to the most to all damage categories. Its contribution is 61%, 94%, 80% and 79% of the total contribution to "Human Health", "Ecosystem quality", "Climate change", and "Resources" damage categories respectively. When compared to light fossil fuels, biomass briquettes present overall better environmental results with exceptions for "Non-carcinogens" (6.28E-04 kg C2H3Cleq), "Aquatic ecotoxicity" (1.01E-02 kg TEG water), "Terrestrial ecotoxicity" (5.04E-02 kg TEG soil), and "Land occupation" (9.37E-03 m2org.able) impact categories. This overall outcome is mainly linked to the fact that biomass briquettes are used as a replacement to traditionally adopted energy sources while reducing burning activities in the field. Moreover, sensitivity and uncertainty analyses are also conducted to verify the robustness of the results. Keywords Life Cycle Assessment, Biomass, Biomass briquettes, Lebanon, Diesel, Sustainability 1
Introduction
Lebanon is heavily dependent on fossil fuel imports and has growing energy needs, and a high power deficit (UNDP-CEDRO, 2012). In 2009, the Lebanese government committed to the United Nations Framework Convention on Climate Change (UNFCCC), to increase its share of Renewable Energy (RE) to 12.0% of the total energy mix by 2020, thus reducing the country's dependence on fossil fuels (Bassil, 2010; LCEC, 2016). As a result, the National Renewable Energy Action Plan (NREAP) focused on three main areas to achieve this 12% goal: wind, solar and bioenergy (LCEC, 2016). Although the latter sector does not have many privileges in the government's long-term plans, a national bioenergy strategy for Lebanon has been developed (UNDP-CEDRO, 2012). This strategy identified biomass flows and streams
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Journal Pre-proof with potential for bioenergy production. Pruning tree residues have been revealed as one of the sources of bioenergy that can be valued. However, using these residues in raw form can be expensive and inefficient because of their low bulk density. One of the potential solutions that could be provided is briquetting. Briquetting consists in densifying a wide range of materials under high temperature and pressure in order to obtain a dense and homogeneous product. This is one of the favorable options for efficient use of biomass due to the improvement of the enhanced volumetric calorific value (Intelligent Energy Europe, 2008). Historically, briquetting was designed to solve the problem of excess waste, but today biomass briquettes is also used as a source of energy (Nježić et al., 2014). Nowadays, biomass briquettes are mainly used for heating and cooking activities, as well as for replacing light fossil fuels (diesel) or cut wood (Encinas et al., 2015). Different biomass products are used for the production of biomass briquettes and differ from country to country. For example, in China, raw materials mainly include rice husks, agricultural residues and sawdust (Hood, 2010). In India, maize stalks, wood chips, cotton stalks, coffee husks and forest residues are used (Tripathi et al., 1998). In Belarus, biomass comes mainly from the peat industry and is transformed into briquettes (Raslavičius, 2012). In Lebanon, biomass briquettes are mainly made from olive pomace or agricultural and forestry pruning residues (Encinas et al., 2015; Solano et al., 2016). In the same vein, many Lebanese plants producing biomass briquettes have recently been built. Caza of Koura, a region in northern Lebanon known for its vast olive groves, recently benefited from the construction of one of these biomass briquette plants. For several decades, farmers in Caza of Koura have depended on olive groves. However, after the pruning season, small residues (<2 cm) were a nuisance for farmers and were therefore mainly burned in the fields, increasing the risk of fire and constituting a wasted source of renewable energy. Very recently, biomass briquettes were introduced to the Caza of Koura market and were not a major source of heat until the new briquette plant was operated. In fact, a survey of 395 households in Caza of Koura ranked light fossil fuels as the third source of energy for heating during the 20162017 cold season after electricity and gas, and ranked the wood logs in the fourth row (Saba and Gebrayel, 2017). The recent takeoff of the briquette sector in the country raised several environmental concerns related to the use of biomass-based briquettes compared to light fossil fuels, as both products are used in similar stoves and are competitive in the marketplace. Literature is exhausted with studies on emissions of wood products, studies evaluating the impact of the combustion process and the types of heating stoves (Fachinger et al., 2017; Bäfver et al., 2011; Roy et al., 2013; AIRUSE, 2016), studies comparing briquettes, wood pellets, natural gas, coal or heavy fuel oil as sources of heat (Natural Resources Canada, 2013). Similarly, environmental impacts associated with electricity production from wood pellets are compared to coal using a full cradle-to-grave LCA (from the raw material extraction ('cradle') stage to the end-of-life ('grave') stage). Results showed reductions in eight of nine impact categories when co-firing wood pellets within existing coal-fired power stations (Morrison and Golden, 2017). Furthermore, the results of a study performed in Hong Kong showed that significant impacts on health, ecosystem, climate change and resources can be potentially 2
Journal Pre-proof avoided by using wood pellets instead of coal for energy generation (Hossain et al., 2016). More to the point, in a paper studying the life cycle environmental impacts of cornstalk briquettes fuel in China, results also show that when compared to coal, briquettes made out of cornstalks are more environmentally friendly (Wang et al., 2017). To date, no cradle-to-grave Life Cycle Assessment (LCA) have evaluated the environmental impacts of biomass briquettes from the "raw material extraction" stage to the "end-of-life" stage nor compared the environmental impacts of the "use" stage of biomass briquettes and light fossil fuels have been explored in the literature. The objective of this LCA study is therefore to evaluate, for the first time in Lebanon if not in the Middle East region, the environmental impacts associated with all life cycle stages of a biomass briquette, from raw material extraction to processing, manufacturing, distribution, use, and end-of-life. Moreover, this study aims to compare the environmental impacts of the "distribution" and "use" stages of this newly emerging bioenergy product in Lebanon and the light fossil fuels used for domestic heating in traditional Lebanese stoves. 2 2.1
Material and methods Goal and scope
The goal of this study is to evaluate all life cycle stages of a biomass briquette from the extraction of the raw materials until the end-of-life stage from an environmental perspective. Biomass briquettes are produced based on pruning residues obtained from olive groves and forests in the Caza of Koura – Lebanon and used for heating purposes in traditional Lebanese stoves. This study also encompasses a comparative gate-to-gate study of biomass briquettes and light fossil fuels. Moreover, as part of this study, the robustness of the results is weighed throughout a sensitivity analysis. The functional unit is defined as the “production of 1 MJ of useful heat energy” (Chen, 2009; Natural Resources Canada, 2013; Itten and Jungbluth, 2011; Jungbluth,1997). The calorific value of olive pruning residues and light fossil fuels is 19.3 MJ/kg and 45.5 MJ/kg respectively (Boutros and Nehme, 2016). Consequently, reference flows of 5.18E-02 kg of biomass briquettes and 2.20E-02 kg of light fossil fuels are considered to fulfill the functional unit. The cradle-to-grave LCA of biomass briquette is conducted and it includes mining of raw materials (pruning of olive residues using a manual process), road transport of workers to the field (passenger car), coarse field shredding, road transport of the shredded pruning olive residues from the field to the manufacturing site (truck), manufacturing process of briquette, packaging process, road transport of packed briquette from the manufacturing site to the retailer (truck), road transport of packed briquette from the retailer to the consumer (small truck), consumption phase (burning of biomass briquette), road transport of package to landfilling/recycling sites, and end-of-life phase of the package (landfilling and recycling). The packaging material as well as the transportation process of the packaging material to the manufacturing site are excluded from the scope of the study. Figure 1 shows the system boundaries of a biomass briquette defined based on the Caza of Koura case study.
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Figure 1: System boundaries for biomass briquettes
Additionally, a gate-to-gate comparative LCA of biomass briquettes and light fossil fuels is conducted. A gate-to-gate LCA is a partial LCA method, looking at only one value-added process in the entire production chain. Gate-to-gate modules may also later be linked in their appropriate production chain to form a complete cradle-to-gate evaluation (Jiménez-González et al., 2000). For the biomass briquette, it includes road transport of packed briquette from manufacturing site to retail, road transport of packaged briquette from retail to consumer, and the consumption phase. As for the light fossil fuels, it accounts road and transoceanic transport from European countries to retail (based on personal communication with the Lebanese Ministry of Energy and Water), road transport from retail to consumer, electricity consumption of the fuel dispenser, and the consumption phase. 2.2 Life Cycle Inventory (LCI) 2.2.1 Raw Material extraction and manufacturing Biomass briquettes are produced from pruning residues of olive groves, public forests and agricultural waste. The biomass briquettes considered for this study (Figure 2) consist mainly of olive pruning residues since this is the major raw material used for the production of biomass briquettes as part of the SABioP project. A typical production process starts on field where pruning residues are shredded into wood chips. At the plant, chips are conveyed to the fine shredder (hammer mill) where they are reduced to particles of nominal top size of 2-3 mm. The resulting particles are then introduced into a rotary screen with a screw conveyor where large particles are trapped. A third conveyor transports the screened particles to the flash dryer which reduces moisture content from around 40% down to 12%. The dried material is then transported to the briquetting machine. The obtained biomass briquettes are then cooled over a receiving device, manually packed and temporarily stored at the plant before distribution to the retailer then to the consumer (Saba et al., 2018). 4
Journal Pre-proof The amount of material and processes used to produce 5.18E-02 kg of biomass briquettes are classified into primary and secondary data and presented in Table 1. Distances traveled and types of transportation used are depicted in Table 2. Distanced were then altered to ton per kilometer (tkm) by multiplying the distance travelled by the mass of the shipped material. LCI was modeled using the SimaPro 8.5.2.0 Analyst Multi user software (Goedkoop et al., 2013) and the Ecoinvent database. The version of the Ecoinvent database used is ecoinvent 3.3 (Ecoinvent, 2019). Ecoinvent 3.3 builds on previous versions of the database, based on ISO 14040 and 14044 standards, and encompasses around 17,000 LCI datasets in many areas such as energy supply, transport, agriculture, wood, waste treatment, amongst many others. Data collection is a tedious task and is the most demanding task when performing an LCA. Although SimaPro software contains many background data (secondary data), some processes or materials are not available. Therefore, it is useful to distinguish between foreground data (primary data) and background data (secondary data). Foreground data refers to specific data or real-time measurements to describe essential processes and model the system (El Bachawati, 2006b; Koura, 2017). For this study, foreground data (primary data), displayed in Tables 1 and 2, was obtained by a real-time measurement of electricity consumption and through questionnaire sent directly to the Caza of Koura biomass briquette plant ("Al Koura Plant for Biofuel Production"). As for background data (secondary data), this is data for the production of generic materials such as energy, transport and waste management. Usually, background data are not collected via a questionnaire, but they are available in databases or found in the literature. However, the use of background data requires great caution, as one must determine how well the data found in the databases match the requirements set in the goal and scope. In this study, the background data (Tables 1 and 2) are collected from the Ecoinvent database, in particular the European or global context.
Figure 2: Biomass briquettes
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Use phase
In the current study, the use stage is represented by a one-way road trip between the manufacturing plant and the retailer (distance of 6.8 km), a one-way trip between the retailer and the consumer, in addition to the burning process of 5.18E-02 kg of biomass briquette. 2.2.2
End-of-life alternatives
Two alternatives were considered for the disposal of the packaging of briquettes. The first alternative considers a recycling spot in Akkar – North of Lebanon and the second relates to landfilling at “Naameh landfill 7MW power plant” in Chouf – Lebanon. The end-of-life scenarios are based on previous work dedicated to explore the implications of two end-of-life allocation schemes. Furthermore, the transportation process between the briquetting plant located in Caza of Koura and the location of the landfilling/recycling spots are taken into consideration.
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Table 1: Amount of material and processes used to produce 5.18E-02 kg of biomass briquettes
Life Cycle Stage Pruning and field shredding Manufacturing Packaging
Material/Process Ecoinvent
Type of data
Amount
Diesel, low-sulfur {CH}| market for | Cut-off, S
Primary data*
2.09E-4 kg
Electricity, low voltage {RoW}| market for | Cut-off, S
Secondary data
1.44E-2 kWh
Wood, unspecified, standing/kg
Primary data
3.70E-3 kg
Polypropylene, granulate {GLO}| market for | Cut-off, S
Primary data
1.33E-1 g
Distribution Heat, district or industrial, other than natural gas {RoW}| Consumption
heat production, softwood chips from forest, at furnace 1000kW | Cut-off, S Recycling of polypropylene
End-of-life
Waste polypropylene {RoW}| treatment of waste polypropylene, sanitary landfill | Cut-off, S DummyWasteTreatment
Secondary data**
1.00E0 MJ
Secondary data
7.02E-2 g
Secondary data
2.49E-2 g
Secondary data
3.79E-2 g
** Primary Data: Specific data or real-time measurements ** Secondary data: Ecoinvent database
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Table 2: Distance traveled and type of transportation to produce 5.18E-02 kg of biomass briquettes
Life Cycle Stage Pruning and field shredding
Material/Process Ecoinvent
Type of data
Distance
Transport, passenger car, EURO 4 {RoW}| market for | Cut-off, S
Secondary data
Transport, freight, lorry 7.5-16 metric ton, EURO4 {GLO}| market for | Cut-off, S
Secondary data
Transport, freight, lorry >32 metric ton, EURO4 {GLO}| market for | Cut-off, S
Secondary data
6.8
Transport, freight, lorry >32 metric ton, EURO4 {GLO}| market for | Cut-off, S
Secondary data
Transport, freight, lorry 3.5-7.5 metric ton, EURO4 {RoW}| transport, freight, lorry 3.5-7.5 metric ton, EURO4 | Cut-off, S
Secondary data
Municipal waste collection service by 21 metric ton lorry {RoW}| market for municipal waste collection service by 21 metric ton lorry | Cut-off, S
Secondary data
0.00112*
km
tkm -
-
-
- - -
2.23E-3
tkm
km
9.04E-7
tkm
6.8
km
3.54E-4
tkm
6.8
km
1.77E-5
tkm
38.8
km
2.72E-6
tkm
93.4
km
2.32E-6
tkm
Manufacturing Packaging
Distribution
Consumption End-of-life
*: 0.082 kg of pruning residue is needed to produce 1 MJ of useful heat. Four workers work a total of 32 hours (one working day) to produce one tonne of pruning residue. The average distance of a round trip between the workers' house and the field is 13.6 km. Therefore, the allocation of the passenger car in respect to the functional unit is (0.082*13.6)/1000 = 0.00112 km.
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Life Cycle Impact assessment (LCIA)
The Life Cycle Impact Assessment (LCIA) aims to translate the findings of the inventory to an impact profile. IMPACT 2002+ methodology is selected as LCIA method because it brings all possible impact categories, highly required by the industry, to an endpoint (Jolliet et al., 2003). IMPACT 2002+ considers several midpoint categories, e.g. land occupation, global warming, and ozone depletion. 3 3.1
Results and Discussion Cradle-to-grave environmental impacts of biomass briquette
Figure 3 illustrates the contribution of the different life cycle stages of biomass briquettes to each of the 15 impact categories. A positive impact score means that the burdens are higher than the credits and the net effect is damaging for the environment while a negative impact score indicates that the credits are higher than the burdens and that the net effect is beneficial for the environment. For example, the negative impact score of the "consumption" life cycle stage is due to the applied consequential modeling in which the production of an intermediate exchange may result in a decrease in the production of another. This avoided production is displayed in the scaling vector with a negative sign. The results presented in Figure 3 reveal that "manufacturing" and "consumption" life cycles stages are the main contributors to most impact categories. Furthermore, the contribution of the "pruning and field shredding" life cycle stage is also significant especially for "carcinogens" and “respiratory organics” impact categories due to the road transport of workers to the field (40%), the road transport of the shredded pruning olive residues from the field to the manufacturing site (38%), and to the light fossil fuels (22%) used in the coarse field shredder. In addition, Figure 4 depicts the contribution of the different life cycle stages of biomass briquettes to all damage categories namely human health, ecosystem quality, climate change and resources. The contribution of the "manufacturing" life cycle stage is 38%, 5%, 19%, and 18% of the total contribution (positive and negative impact score) to the "Human Health", "Ecosystem quality", "Climate change", and "Resources" damage categories respectively. As for "consumption" life cycle stage, its contribution is 61%, 94%, 80%, and 79% of the total contribution to the "Human Health", "Ecosystem quality", "Climate change", and "Resources" damage categories respectively. Over the very few LCA studies for the wood briquettes in the literature, M. Brand et al. (2017) assessed the environmental impacts of briquettes "produced with different proportions of rice husk, rice straw and rice husk ash" in order to enhance the use of waste from rice cultivation and industrial processing. The outcomes of that study clearly showed that by integrating the rice straw, the energy properties of the biomass briquettes will improve, the calorific value would increase, and the ash content will dismiss (Brand et al., 2017). Moreover, the study done by M. Brand et al. highlighted that burning, packaging, drying of the shredded wood, and field coarse shredding processes are the main contributing processes.
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Figure 3: Contribution of the different life cycle stages of biomass briquette to the environmental impacts
Figure 4: Damage assessment of biomass briquettes on human health, ecosystem quality, climate change and resources
3.2
Comparative gate-to-gate assessment
Figure 5 compares the environmental impacts of the "distribution" life cycle stage (i.e. transportation from the manufacturing site to the retailer and from the retailer to the consumer), and the "consumption" life cycle stage (i.e. burning process) of biomass briquettes and light fossil fuels. In addition, Table 3 presents the numerical contribution of each process to each of the 15 impact categories studied. The findings were very satisfying as light fossil fuels contribute more than biomass briquettes for all impact categories except for "Noncarcinogens" (6.28E-04 kg C2H3Cleq), "Aquatic ecotoxicity" (1.01E-02 kg TEG water), "Terrestrial ecotoxicity" (5.04E-02 kg TEG soil), and "Land occupation" (9.37E-03 m2org.able) impact categories because of the burning process (Figure 6). The findings of this study are globally similar to those of Zhi et al. (2015) where it was demonstrated through a comparative LCA that the environmental effects of briquette are far lower than the environmental effects of lignite coal (Zhi et al., 2015).
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Figure 5: Comparative gate-to-gate life cycle environmental impacts of biomass briquettes and light fossil fuels
Figure 6: Comparative damage assessment of biomass briquettes and light fossil fuels
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Journal Pre-proof Table 3: Potential environmental impacts of biomass briquettes and light fossil fuels
Human health
Ecosystem quality
Climate change Resources
3.3
Impact category
Unit
Biomass briquettes
Light fossil fuels
Carcinogens
kg C2H3Cl eq
3.04E-04
1.22E-05
Non-carcinogens
kg C2H3Cl eq
3.17E-04
1.19E-03
Respiratory inorganics
kg PM2.5 eq
3.28E-05
3.06E-05
Ionizing radiation
Bq C-14 eq
6.13E-01
-2.61E-01
Ozone layer depletion
kg CFC-11 eq
1.70E-08
-8.09E-09
Respiratory organics
kg C2H4 eq
1.81E-05
-2.67E-06
Aquatic acidification
kg SO2 eq
2.28E-04
-3.08E-05
Aquatic ecotoxicity
kg TEG water
5.62E+00
7.27E+00
Aquatic eutrophication
kg PO4 P-lim
7.72E-06
1.44E-06
Terrestrial acid/nutri
kg SO2 eq
7.16E-04
1.89E-04
Terrestrial ecotoxicity
kg TEG soil
2.37E+00
2.54E+00
Land occupation
m2org.arable
1.56E-04
9.70E-03
Global warming
kg CO2 eq
9.21E-02
-4.17E-02
Mineral extraction
MJ surplus
1.98E-04
5.66E-05
Non-renewable energy
MJ primary
1.42E+00
-6.51E-01
Sensitivity analysis
Sensitivity analysis (SA) is a powerful tool to study the robustness of the results and their sensitivity to uncertainty factors such as methodological choices, initial assumptions or quality of the available data (El Bachawati et al., 2016a). In the current study, the SA was performed for the electricity grid and for the avoided products. For the electricity grid, two scenarios are envisaged. The scenario “Actual Lebanese Energy Mix” where electricity is produced by thermal power plants and hydroelectric power plants. The second scenario is the “Lebanese Energy Mix 2020” where electricity is produced by thermal power plants, hydroelectric power plants, photovoltaic cells, wind power, bioenergy and geothermal power plants. Based on the National Renewable Energy Action Plan report, targets for the increase of RE shares to 12% of the total Lebanese fuel mix are set for the year 2020 (Bassil, 2010; LCEC, 2016). As a result, the SA for the electricity grid was conducted. Results depicted that the actual Lebanese energy mix has the highest contribution for most of the impact categories compared to the Lebanese energy mix in 2020 except for "carcinogens", "non-carcinogens", "terrestrial ecotoxicity", "land occupation" and "mineral extraction" impact categories (Figure 7). Although several methods such as nitrifying-enriched activated sludge (NAS) approach can be very useful in reducing greenhouse gases (Sepehri, and Sarrafzadeh, 2018), the findings of this study confirm that increasing the share of RE (more than 12%) in the total energy production will improve the Lebanese electricity grid, will lower GHG emissions from the energy sector, and will reduce the life cycle environmental impacts. 12
Journal Pre-proof With respect to avoided products, it is worth mentioning that prior to the existence of biomass briquettes, farmers had adopted open burning as a means of eliminating size residues, resulting in increased air pollution and fire hazards. The introduction of biomass briquettes on the local market will be possible through the replacement of wood logs or light fossil fuels. As a result, increasing the number of biomass briquette users will reduce emissions from open-air combustion and avoid the use of equivalent calorific value derived from wood logs or light fossil fuels. Two scenarios are considered for the SA; the first one considers that biomass briquettes would replace 70% and 30% of the useful thermal energy obtained respectively from cut wood logs and light fossil fuels while the second scenario envisages a replacement level of 90% for cut wood logs and 10% for light fossil fuels. The default scenario considers that biomass briquettes replaced 50%-50% of the useful heat generated from cut wood logs and light fossil fuels. This hypothesis is based on a survey of 395 households in Caza of Koura, where almost the same number of people showed their willingness to switch from chopped wood logs and light fossil fuels to biomass briquettes (Saba and Gebrayel, 2017).. The results presented in Figure 8 show that the number of biomass briquette users strongly influences the environmental impacts. It is also remarkable that the second scenario (replacement level of 90% for cut wood logs and 10% for light fossil fuels) is the one that contributes the least to all impact categories. Consequently, this comparative LCA urge the replacement of cut wood logs and fossil fuel with biomass briquettes from an environmental point of view.
Figure 7: Sensitivity analysis for the actual Lebanese energy mix and the Lebanese energy mix in 2020
Figure 8: Sensitivity analysis for the avoided products
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Uncertainty analysis
At both LCI and LCIA stages, the uncertainty imported to the inventory could be due to the cumulative effects of inaccurate assumption; geographical or technological gaps; lack of temporal information; or incomplete data (Kohler, 2012; Björklund, 2002). Moreover, uncertainty analyses could also be conducted on landfill emissions at different time horizons to explore the effects of the time horizon on ozone layer depletion and global warming potential. Monte Carlo simulation was applied to estimate the uncertainties introduced in the LCI data and to express them as a probability distribution (Morgan, 1990). Monte Carlo, an integrated feature of the SimaPro 8.5.2.0 Analyst multi-user software, was operated with a 95% confidence interval, 1,000 runs and a stop factor of 0.005. Figure 9 depicts the uncertainty analysis for low voltage electricity. Results reveal that uncertainties were acceptable for all impact categories except for "Non-carcinogens", "Ionizing radiation", and "Aquatic eutrophication" impact categories where the uncertainty reaches 530%, 500%, and 287% respectively.
Figure 9: Uncertainty analysis for the electricity
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Conclusion
A cradle-to-grave LCA was performed for biomass briquettes from raw material extraction ('cradle') stage through materials processing, manufacturing, distribution, use, and end of life ('grave') stages. The results reveal that "manufacturing" and "consumption" life cycles stages are the main contributors to all impact categories except for "carcinogens" and “respiratory organics” impact categories. Therefore, increasing the share of renewable energy (over 12%) in total energy production will not only lower the GHG emissions but it will also reduce the life cycle environmental impacts. In line with this, the comparative gate-to-gate LCA depicts that the light fossil fuels contribute more than biomass briquettes for all impact categories except for "Non-carcinogens" (6.28E04 kg C2H3Cleq), "Aquatic ecotoxicity" (1.01E-02 kg TEG water), "Terrestrial ecotoxicity" (5.04E-02 kg TEG soil), and "Land occupation" (9.37E-03 m2org.able) impact categories because of the burning process. Thus by expanding the level of replacement of logs and light fossil fuels, the impacts on human health, resources, and climate change will be minimized and the quality of ecosystem will be improved. This overall outcome is mainly linked to the fact that biomass briquettes are used as a replacement to traditionally adopted energy sources while reducing burning activities in the field. Consequently, the introduction of biomass briquettes 14
Journal Pre-proof as a replacement of these two existing heating means would result in overall improved environmental properties. Additionally, in the near future, a research study on Lebanese stoves will be conducted to evaluate the best means to control emissions related to their use and thus reduce the environmental impact of the consumption stage. Finally, a cradle-to-grave LCA study will be performed to assess the environmental impacts of light fossil fuels from raw material extraction to the end-of-life stage. 5
Acknowledgement
This study is part of the Sustainable Action for Bioenergy Production (SABioP) project funded by The European Union (Contract Number: ENPI/2014/354 - 063) and implemented by The University of Balamand in partnership with Koura Municipalities Union and El Koura Development Council. This publication has been produced with the assistance of the European Union. The contents of this publication are the sole responsibility of the authors and can in no way be taken to reflect the views of the European Union. 6
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El Bachawati, M., Manneh, R., Belarbi, R., El Zakhem, H., 2016. Real-time temperature monitoring for traditional gravel ballasted and extensive green roofs: A Lebanese case study, Energy Build. 133, 197–205. http://dx.doi.org/10.1016/j.enbuild.2016.09.056. Encinas, E-E., Colomer, R., Pajares P-R., Martinez, F-M., 2015. Thermal Biomass for Lebanon. Retrieved from http://shoufcedar.org/wp/wpcontent/uploads/2017/05/Biomass_plan_Shouf_Biosphere_Reserve_Final_low_res_3227 033_201554000_40193440.pdf . (Accessed February 2019). Fachinger, F., Drewnick, F., Gieré, R., Borrmann, S., 2017. How the user can influence particulate emissions from residential wood and pellet stoves: Emission factors for different fuels and burning conditions. https://doi.org/10.1016/j.atmosenv.2017.03.027. Finnveden, G., Hauschild. MZ., Ekvall. T., Guinee. J., Heijungs. R., Hellweg. S., et al., 2009. Recent developments in Life Cycle Assessment. J Environ Manage (91), 1-21 Goedkoop, M., Oele, M., Leijting, J., Ponsioen, T, Meijer, E., 2013. Introduction to LCA with SimaPro. https://www.presustainability.com/download/SimaPro8IntroductionToLCA.pdf (accessed February 2019). Grover, P.D., Mishra, S.K., 1996. Biomass Briquetting: Technology and practices. Food and Agriculture Organization of the United Nations, Bangkok. https://www.fao.org/3/ad579e/ad579e00.pdf (accessed January 2019). Hood, H., 2010. Biomass briquetting in Sudan: a feasibility study. United States Agency for International Development. https://www.scribd.com/document/79478729/USAIDBriquetting-Feasibility-Study-Sudan (accessed on March 2019). Hossain, M. U., Leu, S., Poon, C. S., 2016. Sustainability analysis of pelletized bio-fuel derived from recycled wood product wastes in Hong Kong. https://doi.org/10.1016/j.jclepro.2015.11.069. Intelligent Energy Europe, 2008. Market of olive residues for energy, Croatia: Institute of Agriculture and Tourism Poreč Croatia. Itten, R., Stucki, M., Jungbluth, N., 2011. Life Cycle Assessment of Burning Different Solid Biomass Substrates. http://esu-services.ch/fileadmin/download/publicLCI/itten-2011solid-biomass-combustion.pdf (accessed March 2019). Jolliet, O., Margni, M., Charles, R. et al., 2003. IMPACT 2002+: A new life cycle impact assessment methodology. Int J LCA. 8: 324. https://doi.org/10.1007/BF02978505. Jiménez-González, C., Kim, S. & Overcash, M.R. Int. J. LCA (2000) 5: 153. https://doi.org/10.1007/BF02978615 Jungbluth, N., 1997. Life-Cycle-Assessment for Stoves and Ovens. UNS-Working Paper No. 16, Umweltnatur- und Umweltsozialwissenschaften (UNS), Eidgenössische Technische Hochschule, Zürich. 16
Journal Pre-proof Kohler N., Lützkendorf T. (2002). Integrated Life Cycle Analysis. Building Research & Information: 30(5), 338–348. Doi: https://doi.org/10.1080/09613210110117584 Koura, J., Manneh, R., Belarbi, R., El Khoury, V., El Bachawati, M., 2017. Seasonal variability of temperature profiles of vegetative and traditional gravel-ballasted roofs: A case study for Lebanon, Energy Build. 151:358-364. http://dx.doi.org/10.1016/j.enbuild.2017.06.066 LCEC Lebanese Center for Energy Conversation, 2016. The national renewable energy action plan for the republic of Lebanon 2016-2020. Lebanon: Lebanese Center for Energy Conversation. http://lcec.org.lb/Content/uploads/LCECOther/161214021429307~NREAP_DEC14.pdf. (accessed January 2019). Mitri, G., Saba, S., Karam, J., Sakr R., Abou Dagher, M., Malek, M., Nasrallah, G., 2016. Estimation of biomass quantities from forest pruning and residues of olive trees in the Caza of Koura. University of Balamand, Institute of the Environment. Morgan MG, Henrion M. (1990). Uncertainty. Cambridge university press. United Kingdom Morrison, B., Golden, J. S., 2017. Life cycle assessment of co-firing coal and wood pellets in the southeastern united states. https://doi.org/10.1016/j.jclepro.2017.03.026. Natural Resources Canada, 2013. Comparative life cycle assessment of Pellet, Natural Gas and Heavy Fuel Oil as Heat Energy Sources. http://hardwoodinitiative.fpinnovations.ca/files/publications-reports/reports/comparativelca-report.pdf (accessed March 2019). Nježić, Z., Cvetković, B., Kormanjoš, Š., Banjac, V., and Živković, J., 2014. Briquetting and pelleting the biomass – protection from fire and explosions. https://scindeksclanci.ceon.rs/data/pdf/0351-9465/2014/0351-94651401086N.pdf (accessed February 2019). Policy Paper for the Electricity Sector. Lebanese Republic Ministry of Energy and Water. Retrieved from http://climatechange.moe.gov.lb/viewfile.aspx?id=121 Raslavičius, L., 2012. Renewable energy https://doi.org/10.1016/j.rser.2012.04.056.
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Journal Pre-proof Sepehri, A., Sarrafzadeh, M.-H, 2018. Effect of nitrifiers community on fouling mitigation and nitrification efficiency in a membrane bioreactor. Chemical Engineering and Processing Process Intensification. 128, 10–18. https://doi.org/10.1016/j.cep.2018.04.006. Solano D., Vinyes P., Arranz P., 2016. The biomass briquetting process. http://www.cedroundp.org/content/uploads/publication/161124125247966~Briquettingreportforweb.pdf (accessed on March 2019). Tripathi, A. K., Iyer, P. V. R., & Kandpal, T. C., 1998. A techno-economic evaluation of biomass briquetting in India. https://doi.org/10.1016/S0961-9534(97)10023-X. UNDP-CEDRO, 2012. National Bioenergy Strategy for Lebanon. Retrieved from http://www.cedroundp.org/content/uploads/publication/141003043844453~The%20National%20Bioenerg y%20Strategy%20for%20Lebanon.pdf (accessed on February 2019). Wang, Z., Lei, T., Yang, M., Li, Z., Qi, T., Xin, X., Ajayebi,A., Yan, X., 2017. Life cycle environmental impacts of cornstalk briquette fuel in china. https://doi.org/10.1016/j.apenergy.2017.01.071 . Zhi, J. H., Cheng, F. Q., Han, H. Z., & Yang, F. L., 2015. Comparative life cycle assessment on environment -friendly clean briquette and lignite. Materials Research Innovations, 19, S296; S2-102. doi: https://doi.org/10.1179/1432891715Z.0000000001319
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Declaration of interests ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
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1. Sabine Saba Conceptualization, Methodology, Formal Analysis, Writing - Review & Editing.
2. Makram El Bachawati Software, Formal Analysis, Data Curation, Writing - Original Draft, Writing - Review & Editing.
3. Mike Malek Methodology, Investigation, Writing - Original Draft.
Sabine Saba, Makram El Bachawati, Mike Malek PII:
S0959-6526(19)34721-3
DOI:
https://doi.org/10.1016/j.jclepro.2019.119851
Reference:
JCLP 119851
To appear in:
Journal of Cleaner Production
Received Date:
13 June 2019
Accepted Date:
21 December 2019
Please cite this article as: Sabine Saba, Makram El Bachawati, Mike Malek, Cradle to grave Life Cycle Assessment of Lebanese biomass briquettes, Journal of Cleaner Production (2019), https://doi.org/10.1016/j.jclepro.2019.119851
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier.
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Cradle to grave Life Cycle Assessment of Lebanese biomass briquettes Sabine Saba1, Makram El Bachawati2, Mike Malek1 1University
of Balamand, Institute of the Environment, North Lebanon, PO Box: 100-Tripoli, Lebanon 2University of Balamand, Chemical Engineering Department, El Koura, North Lebanon, PO Box: 100Tripoli, Lebanon Co-authors e-mail address: [email protected]; [email protected] Corresponding author e-mail address: [email protected]
Abstract The bioenergy sector is showing a recent development in Lebanon, a Mediterranean country, where the valorization of forestry and agricultural waste through briquetting consists one of the mostly applied and targeted applications. This study aims at analyzing the life cycle environmental impacts of biomass briquettes produced from olive pruning residues and used for heating purposes in traditional Lebanese stoves. The biomass briquettes are mainly introduced as a replacement for the light fossil fuels widespread used in similar stoves for the same purpose. Consequently, this paper also extends the literature-found comparison of the consumption phases between biomass briquettes and light fossil fuels to a comparative gateto-gate LCA of these products. For the briquette itself, the results indicate that the "consumption" life cycle stage is the one that contributes to the most to all damage categories. Its contribution is 61%, 94%, 80% and 79% of the total contribution to "Human Health", "Ecosystem quality", "Climate change", and "Resources" damage categories respectively. When compared to light fossil fuels, biomass briquettes present overall better environmental results with exceptions for "Non-carcinogens" (6.28E-04 kg C2H3Cleq), "Aquatic ecotoxicity" (1.01E-02 kg TEG water), "Terrestrial ecotoxicity" (5.04E-02 kg TEG soil), and "Land occupation" (9.37E-03 m2org.able) impact categories. This overall outcome is mainly linked to the fact that biomass briquettes are used as a replacement to traditionally adopted energy sources while reducing burning activities in the field. Moreover, sensitivity and uncertainty analyses are also conducted to verify the robustness of the results. Keywords Life Cycle Assessment, Biomass, Biomass briquettes, Lebanon, Diesel, Sustainability 1
Introduction
Lebanon is heavily dependent on fossil fuel imports and has growing energy needs, and a high power deficit (UNDP-CEDRO, 2012). In 2009, the Lebanese government committed to the United Nations Framework Convention on Climate Change (UNFCCC), to increase its share of Renewable Energy (RE) to 12.0% of the total energy mix by 2020, thus reducing the country's dependence on fossil fuels (Bassil, 2010; LCEC, 2016). As a result, the National Renewable Energy Action Plan (NREAP) focused on three main areas to achieve this 12% goal: wind, solar and bioenergy (LCEC, 2016). Although the latter sector does not have many privileges in the government's long-term plans, a national bioenergy strategy for Lebanon has been developed (UNDP-CEDRO, 2012). This strategy identified biomass flows and streams
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Journal Pre-proof with potential for bioenergy production. Pruning tree residues have been revealed as one of the sources of bioenergy that can be valued. However, using these residues in raw form can be expensive and inefficient because of their low bulk density. One of the potential solutions that could be provided is briquetting. Briquetting consists in densifying a wide range of materials under high temperature and pressure in order to obtain a dense and homogeneous product. This is one of the favorable options for efficient use of biomass due to the improvement of the enhanced volumetric calorific value (Intelligent Energy Europe, 2008). Historically, briquetting was designed to solve the problem of excess waste, but today biomass briquettes is also used as a source of energy (Nježić et al., 2014). Nowadays, biomass briquettes are mainly used for heating and cooking activities, as well as for replacing light fossil fuels (diesel) or cut wood (Encinas et al., 2015). Different biomass products are used for the production of biomass briquettes and differ from country to country. For example, in China, raw materials mainly include rice husks, agricultural residues and sawdust (Hood, 2010). In India, maize stalks, wood chips, cotton stalks, coffee husks and forest residues are used (Tripathi et al., 1998). In Belarus, biomass comes mainly from the peat industry and is transformed into briquettes (Raslavičius, 2012). In Lebanon, biomass briquettes are mainly made from olive pomace or agricultural and forestry pruning residues (Encinas et al., 2015; Solano et al., 2016). In the same vein, many Lebanese plants producing biomass briquettes have recently been built. Caza of Koura, a region in northern Lebanon known for its vast olive groves, recently benefited from the construction of one of these biomass briquette plants. For several decades, farmers in Caza of Koura have depended on olive groves. However, after the pruning season, small residues (<2 cm) were a nuisance for farmers and were therefore mainly burned in the fields, increasing the risk of fire and constituting a wasted source of renewable energy. Very recently, biomass briquettes were introduced to the Caza of Koura market and were not a major source of heat until the new briquette plant was operated. In fact, a survey of 395 households in Caza of Koura ranked light fossil fuels as the third source of energy for heating during the 20162017 cold season after electricity and gas, and ranked the wood logs in the fourth row (Saba and Gebrayel, 2017). The recent takeoff of the briquette sector in the country raised several environmental concerns related to the use of biomass-based briquettes compared to light fossil fuels, as both products are used in similar stoves and are competitive in the marketplace. Literature is exhausted with studies on emissions of wood products, studies evaluating the impact of the combustion process and the types of heating stoves (Fachinger et al., 2017; Bäfver et al., 2011; Roy et al., 2013; AIRUSE, 2016), studies comparing briquettes, wood pellets, natural gas, coal or heavy fuel oil as sources of heat (Natural Resources Canada, 2013). Similarly, environmental impacts associated with electricity production from wood pellets are compared to coal using a full cradle-to-grave LCA (from the raw material extraction ('cradle') stage to the end-of-life ('grave') stage). Results showed reductions in eight of nine impact categories when co-firing wood pellets within existing coal-fired power stations (Morrison and Golden, 2017). Furthermore, the results of a study performed in Hong Kong showed that significant impacts on health, ecosystem, climate change and resources can be potentially 2
Journal Pre-proof avoided by using wood pellets instead of coal for energy generation (Hossain et al., 2016). More to the point, in a paper studying the life cycle environmental impacts of cornstalk briquettes fuel in China, results also show that when compared to coal, briquettes made out of cornstalks are more environmentally friendly (Wang et al., 2017). To date, no cradle-to-grave Life Cycle Assessment (LCA) have evaluated the environmental impacts of biomass briquettes from the "raw material extraction" stage to the "end-of-life" stage nor compared the environmental impacts of the "use" stage of biomass briquettes and light fossil fuels have been explored in the literature. The objective of this LCA study is therefore to evaluate, for the first time in Lebanon if not in the Middle East region, the environmental impacts associated with all life cycle stages of a biomass briquette, from raw material extraction to processing, manufacturing, distribution, use, and end-of-life. Moreover, this study aims to compare the environmental impacts of the "distribution" and "use" stages of this newly emerging bioenergy product in Lebanon and the light fossil fuels used for domestic heating in traditional Lebanese stoves. 2 2.1
Material and methods Goal and scope
The goal of this study is to evaluate all life cycle stages of a biomass briquette from the extraction of the raw materials until the end-of-life stage from an environmental perspective. Biomass briquettes are produced based on pruning residues obtained from olive groves and forests in the Caza of Koura – Lebanon and used for heating purposes in traditional Lebanese stoves. This study also encompasses a comparative gate-to-gate study of biomass briquettes and light fossil fuels. Moreover, as part of this study, the robustness of the results is weighed throughout a sensitivity analysis. The functional unit is defined as the “production of 1 MJ of useful heat energy” (Chen, 2009; Natural Resources Canada, 2013; Itten and Jungbluth, 2011; Jungbluth,1997). The calorific value of olive pruning residues and light fossil fuels is 19.3 MJ/kg and 45.5 MJ/kg respectively (Boutros and Nehme, 2016). Consequently, reference flows of 5.18E-02 kg of biomass briquettes and 2.20E-02 kg of light fossil fuels are considered to fulfill the functional unit. The cradle-to-grave LCA of biomass briquette is conducted and it includes mining of raw materials (pruning of olive residues using a manual process), road transport of workers to the field (passenger car), coarse field shredding, road transport of the shredded pruning olive residues from the field to the manufacturing site (truck), manufacturing process of briquette, packaging process, road transport of packed briquette from the manufacturing site to the retailer (truck), road transport of packed briquette from the retailer to the consumer (small truck), consumption phase (burning of biomass briquette), road transport of package to landfilling/recycling sites, and end-of-life phase of the package (landfilling and recycling). The packaging material as well as the transportation process of the packaging material to the manufacturing site are excluded from the scope of the study. Figure 1 shows the system boundaries of a biomass briquette defined based on the Caza of Koura case study.
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Figure 1: System boundaries for biomass briquettes
Additionally, a gate-to-gate comparative LCA of biomass briquettes and light fossil fuels is conducted. A gate-to-gate LCA is a partial LCA method, looking at only one value-added process in the entire production chain. Gate-to-gate modules may also later be linked in their appropriate production chain to form a complete cradle-to-gate evaluation (Jiménez-González et al., 2000). For the biomass briquette, it includes road transport of packed briquette from manufacturing site to retail, road transport of packaged briquette from retail to consumer, and the consumption phase. As for the light fossil fuels, it accounts road and transoceanic transport from European countries to retail (based on personal communication with the Lebanese Ministry of Energy and Water), road transport from retail to consumer, electricity consumption of the fuel dispenser, and the consumption phase. 2.2 Life Cycle Inventory (LCI) 2.2.1 Raw Material extraction and manufacturing Biomass briquettes are produced from pruning residues of olive groves, public forests and agricultural waste. The biomass briquettes considered for this study (Figure 2) consist mainly of olive pruning residues since this is the major raw material used for the production of biomass briquettes as part of the SABioP project. A typical production process starts on field where pruning residues are shredded into wood chips. At the plant, chips are conveyed to the fine shredder (hammer mill) where they are reduced to particles of nominal top size of 2-3 mm. The resulting particles are then introduced into a rotary screen with a screw conveyor where large particles are trapped. A third conveyor transports the screened particles to the flash dryer which reduces moisture content from around 40% down to 12%. The dried material is then transported to the briquetting machine. The obtained biomass briquettes are then cooled over a receiving device, manually packed and temporarily stored at the plant before distribution to the retailer then to the consumer (Saba et al., 2018). 4
Journal Pre-proof The amount of material and processes used to produce 5.18E-02 kg of biomass briquettes are classified into primary and secondary data and presented in Table 1. Distances traveled and types of transportation used are depicted in Table 2. Distanced were then altered to ton per kilometer (tkm) by multiplying the distance travelled by the mass of the shipped material. LCI was modeled using the SimaPro 8.5.2.0 Analyst Multi user software (Goedkoop et al., 2013) and the Ecoinvent database. The version of the Ecoinvent database used is ecoinvent 3.3 (Ecoinvent, 2019). Ecoinvent 3.3 builds on previous versions of the database, based on ISO 14040 and 14044 standards, and encompasses around 17,000 LCI datasets in many areas such as energy supply, transport, agriculture, wood, waste treatment, amongst many others. Data collection is a tedious task and is the most demanding task when performing an LCA. Although SimaPro software contains many background data (secondary data), some processes or materials are not available. Therefore, it is useful to distinguish between foreground data (primary data) and background data (secondary data). Foreground data refers to specific data or real-time measurements to describe essential processes and model the system (El Bachawati, 2006b; Koura, 2017). For this study, foreground data (primary data), displayed in Tables 1 and 2, was obtained by a real-time measurement of electricity consumption and through questionnaire sent directly to the Caza of Koura biomass briquette plant ("Al Koura Plant for Biofuel Production"). As for background data (secondary data), this is data for the production of generic materials such as energy, transport and waste management. Usually, background data are not collected via a questionnaire, but they are available in databases or found in the literature. However, the use of background data requires great caution, as one must determine how well the data found in the databases match the requirements set in the goal and scope. In this study, the background data (Tables 1 and 2) are collected from the Ecoinvent database, in particular the European or global context.
Figure 2: Biomass briquettes
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Use phase
In the current study, the use stage is represented by a one-way road trip between the manufacturing plant and the retailer (distance of 6.8 km), a one-way trip between the retailer and the consumer, in addition to the burning process of 5.18E-02 kg of biomass briquette. 2.2.2
End-of-life alternatives
Two alternatives were considered for the disposal of the packaging of briquettes. The first alternative considers a recycling spot in Akkar – North of Lebanon and the second relates to landfilling at “Naameh landfill 7MW power plant” in Chouf – Lebanon. The end-of-life scenarios are based on previous work dedicated to explore the implications of two end-of-life allocation schemes. Furthermore, the transportation process between the briquetting plant located in Caza of Koura and the location of the landfilling/recycling spots are taken into consideration.
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Table 1: Amount of material and processes used to produce 5.18E-02 kg of biomass briquettes
Life Cycle Stage Pruning and field shredding Manufacturing Packaging
Material/Process Ecoinvent
Type of data
Amount
Diesel, low-sulfur {CH}| market for | Cut-off, S
Primary data*
2.09E-4 kg
Electricity, low voltage {RoW}| market for | Cut-off, S
Secondary data
1.44E-2 kWh
Wood, unspecified, standing/kg
Primary data
3.70E-3 kg
Polypropylene, granulate {GLO}| market for | Cut-off, S
Primary data
1.33E-1 g
Distribution Heat, district or industrial, other than natural gas {RoW}| Consumption
heat production, softwood chips from forest, at furnace 1000kW | Cut-off, S Recycling of polypropylene
End-of-life
Waste polypropylene {RoW}| treatment of waste polypropylene, sanitary landfill | Cut-off, S DummyWasteTreatment
Secondary data**
1.00E0 MJ
Secondary data
7.02E-2 g
Secondary data
2.49E-2 g
Secondary data
3.79E-2 g
** Primary Data: Specific data or real-time measurements ** Secondary data: Ecoinvent database
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Table 2: Distance traveled and type of transportation to produce 5.18E-02 kg of biomass briquettes
Life Cycle Stage Pruning and field shredding
Material/Process Ecoinvent
Type of data
Distance
Transport, passenger car, EURO 4 {RoW}| market for | Cut-off, S
Secondary data
Transport, freight, lorry 7.5-16 metric ton, EURO4 {GLO}| market for | Cut-off, S
Secondary data
Transport, freight, lorry >32 metric ton, EURO4 {GLO}| market for | Cut-off, S
Secondary data
6.8
Transport, freight, lorry >32 metric ton, EURO4 {GLO}| market for | Cut-off, S
Secondary data
Transport, freight, lorry 3.5-7.5 metric ton, EURO4 {RoW}| transport, freight, lorry 3.5-7.5 metric ton, EURO4 | Cut-off, S
Secondary data
Municipal waste collection service by 21 metric ton lorry {RoW}| market for municipal waste collection service by 21 metric ton lorry | Cut-off, S
Secondary data
0.00112*
km
tkm -
-
-
- - -
2.23E-3
tkm
km
9.04E-7
tkm
6.8
km
3.54E-4
tkm
6.8
km
1.77E-5
tkm
38.8
km
2.72E-6
tkm
93.4
km
2.32E-6
tkm
Manufacturing Packaging
Distribution
Consumption End-of-life
*: 0.082 kg of pruning residue is needed to produce 1 MJ of useful heat. Four workers work a total of 32 hours (one working day) to produce one tonne of pruning residue. The average distance of a round trip between the workers' house and the field is 13.6 km. Therefore, the allocation of the passenger car in respect to the functional unit is (0.082*13.6)/1000 = 0.00112 km.
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Life Cycle Impact assessment (LCIA)
The Life Cycle Impact Assessment (LCIA) aims to translate the findings of the inventory to an impact profile. IMPACT 2002+ methodology is selected as LCIA method because it brings all possible impact categories, highly required by the industry, to an endpoint (Jolliet et al., 2003). IMPACT 2002+ considers several midpoint categories, e.g. land occupation, global warming, and ozone depletion. 3 3.1
Results and Discussion Cradle-to-grave environmental impacts of biomass briquette
Figure 3 illustrates the contribution of the different life cycle stages of biomass briquettes to each of the 15 impact categories. A positive impact score means that the burdens are higher than the credits and the net effect is damaging for the environment while a negative impact score indicates that the credits are higher than the burdens and that the net effect is beneficial for the environment. For example, the negative impact score of the "consumption" life cycle stage is due to the applied consequential modeling in which the production of an intermediate exchange may result in a decrease in the production of another. This avoided production is displayed in the scaling vector with a negative sign. The results presented in Figure 3 reveal that "manufacturing" and "consumption" life cycles stages are the main contributors to most impact categories. Furthermore, the contribution of the "pruning and field shredding" life cycle stage is also significant especially for "carcinogens" and “respiratory organics” impact categories due to the road transport of workers to the field (40%), the road transport of the shredded pruning olive residues from the field to the manufacturing site (38%), and to the light fossil fuels (22%) used in the coarse field shredder. In addition, Figure 4 depicts the contribution of the different life cycle stages of biomass briquettes to all damage categories namely human health, ecosystem quality, climate change and resources. The contribution of the "manufacturing" life cycle stage is 38%, 5%, 19%, and 18% of the total contribution (positive and negative impact score) to the "Human Health", "Ecosystem quality", "Climate change", and "Resources" damage categories respectively. As for "consumption" life cycle stage, its contribution is 61%, 94%, 80%, and 79% of the total contribution to the "Human Health", "Ecosystem quality", "Climate change", and "Resources" damage categories respectively. Over the very few LCA studies for the wood briquettes in the literature, M. Brand et al. (2017) assessed the environmental impacts of briquettes "produced with different proportions of rice husk, rice straw and rice husk ash" in order to enhance the use of waste from rice cultivation and industrial processing. The outcomes of that study clearly showed that by integrating the rice straw, the energy properties of the biomass briquettes will improve, the calorific value would increase, and the ash content will dismiss (Brand et al., 2017). Moreover, the study done by M. Brand et al. highlighted that burning, packaging, drying of the shredded wood, and field coarse shredding processes are the main contributing processes.
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Figure 3: Contribution of the different life cycle stages of biomass briquette to the environmental impacts
Figure 4: Damage assessment of biomass briquettes on human health, ecosystem quality, climate change and resources
3.2
Comparative gate-to-gate assessment
Figure 5 compares the environmental impacts of the "distribution" life cycle stage (i.e. transportation from the manufacturing site to the retailer and from the retailer to the consumer), and the "consumption" life cycle stage (i.e. burning process) of biomass briquettes and light fossil fuels. In addition, Table 3 presents the numerical contribution of each process to each of the 15 impact categories studied. The findings were very satisfying as light fossil fuels contribute more than biomass briquettes for all impact categories except for "Noncarcinogens" (6.28E-04 kg C2H3Cleq), "Aquatic ecotoxicity" (1.01E-02 kg TEG water), "Terrestrial ecotoxicity" (5.04E-02 kg TEG soil), and "Land occupation" (9.37E-03 m2org.able) impact categories because of the burning process (Figure 6). The findings of this study are globally similar to those of Zhi et al. (2015) where it was demonstrated through a comparative LCA that the environmental effects of briquette are far lower than the environmental effects of lignite coal (Zhi et al., 2015).
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Figure 5: Comparative gate-to-gate life cycle environmental impacts of biomass briquettes and light fossil fuels
Figure 6: Comparative damage assessment of biomass briquettes and light fossil fuels
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Human health
Ecosystem quality
Climate change Resources
3.3
Impact category
Unit
Biomass briquettes
Light fossil fuels
Carcinogens
kg C2H3Cl eq
3.04E-04
1.22E-05
Non-carcinogens
kg C2H3Cl eq
3.17E-04
1.19E-03
Respiratory inorganics
kg PM2.5 eq
3.28E-05
3.06E-05
Ionizing radiation
Bq C-14 eq
6.13E-01
-2.61E-01
Ozone layer depletion
kg CFC-11 eq
1.70E-08
-8.09E-09
Respiratory organics
kg C2H4 eq
1.81E-05
-2.67E-06
Aquatic acidification
kg SO2 eq
2.28E-04
-3.08E-05
Aquatic ecotoxicity
kg TEG water
5.62E+00
7.27E+00
Aquatic eutrophication
kg PO4 P-lim
7.72E-06
1.44E-06
Terrestrial acid/nutri
kg SO2 eq
7.16E-04
1.89E-04
Terrestrial ecotoxicity
kg TEG soil
2.37E+00
2.54E+00
Land occupation
m2org.arable
1.56E-04
9.70E-03
Global warming
kg CO2 eq
9.21E-02
-4.17E-02
Mineral extraction
MJ surplus
1.98E-04
5.66E-05
Non-renewable energy
MJ primary
1.42E+00
-6.51E-01
Sensitivity analysis
Sensitivity analysis (SA) is a powerful tool to study the robustness of the results and their sensitivity to uncertainty factors such as methodological choices, initial assumptions or quality of the available data (El Bachawati et al., 2016a). In the current study, the SA was performed for the electricity grid and for the avoided products. For the electricity grid, two scenarios are envisaged. The scenario “Actual Lebanese Energy Mix” where electricity is produced by thermal power plants and hydroelectric power plants. The second scenario is the “Lebanese Energy Mix 2020” where electricity is produced by thermal power plants, hydroelectric power plants, photovoltaic cells, wind power, bioenergy and geothermal power plants. Based on the National Renewable Energy Action Plan report, targets for the increase of RE shares to 12% of the total Lebanese fuel mix are set for the year 2020 (Bassil, 2010; LCEC, 2016). As a result, the SA for the electricity grid was conducted. Results depicted that the actual Lebanese energy mix has the highest contribution for most of the impact categories compared to the Lebanese energy mix in 2020 except for "carcinogens", "non-carcinogens", "terrestrial ecotoxicity", "land occupation" and "mineral extraction" impact categories (Figure 7). Although several methods such as nitrifying-enriched activated sludge (NAS) approach can be very useful in reducing greenhouse gases (Sepehri, and Sarrafzadeh, 2018), the findings of this study confirm that increasing the share of RE (more than 12%) in the total energy production will improve the Lebanese electricity grid, will lower GHG emissions from the energy sector, and will reduce the life cycle environmental impacts. 12
Journal Pre-proof With respect to avoided products, it is worth mentioning that prior to the existence of biomass briquettes, farmers had adopted open burning as a means of eliminating size residues, resulting in increased air pollution and fire hazards. The introduction of biomass briquettes on the local market will be possible through the replacement of wood logs or light fossil fuels. As a result, increasing the number of biomass briquette users will reduce emissions from open-air combustion and avoid the use of equivalent calorific value derived from wood logs or light fossil fuels. Two scenarios are considered for the SA; the first one considers that biomass briquettes would replace 70% and 30% of the useful thermal energy obtained respectively from cut wood logs and light fossil fuels while the second scenario envisages a replacement level of 90% for cut wood logs and 10% for light fossil fuels. The default scenario considers that biomass briquettes replaced 50%-50% of the useful heat generated from cut wood logs and light fossil fuels. This hypothesis is based on a survey of 395 households in Caza of Koura, where almost the same number of people showed their willingness to switch from chopped wood logs and light fossil fuels to biomass briquettes (Saba and Gebrayel, 2017).. The results presented in Figure 8 show that the number of biomass briquette users strongly influences the environmental impacts. It is also remarkable that the second scenario (replacement level of 90% for cut wood logs and 10% for light fossil fuels) is the one that contributes the least to all impact categories. Consequently, this comparative LCA urge the replacement of cut wood logs and fossil fuel with biomass briquettes from an environmental point of view.
Figure 7: Sensitivity analysis for the actual Lebanese energy mix and the Lebanese energy mix in 2020
Figure 8: Sensitivity analysis for the avoided products
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Uncertainty analysis
At both LCI and LCIA stages, the uncertainty imported to the inventory could be due to the cumulative effects of inaccurate assumption; geographical or technological gaps; lack of temporal information; or incomplete data (Kohler, 2012; Björklund, 2002). Moreover, uncertainty analyses could also be conducted on landfill emissions at different time horizons to explore the effects of the time horizon on ozone layer depletion and global warming potential. Monte Carlo simulation was applied to estimate the uncertainties introduced in the LCI data and to express them as a probability distribution (Morgan, 1990). Monte Carlo, an integrated feature of the SimaPro 8.5.2.0 Analyst multi-user software, was operated with a 95% confidence interval, 1,000 runs and a stop factor of 0.005. Figure 9 depicts the uncertainty analysis for low voltage electricity. Results reveal that uncertainties were acceptable for all impact categories except for "Non-carcinogens", "Ionizing radiation", and "Aquatic eutrophication" impact categories where the uncertainty reaches 530%, 500%, and 287% respectively.
Figure 9: Uncertainty analysis for the electricity
4
Conclusion
A cradle-to-grave LCA was performed for biomass briquettes from raw material extraction ('cradle') stage through materials processing, manufacturing, distribution, use, and end of life ('grave') stages. The results reveal that "manufacturing" and "consumption" life cycles stages are the main contributors to all impact categories except for "carcinogens" and “respiratory organics” impact categories. Therefore, increasing the share of renewable energy (over 12%) in total energy production will not only lower the GHG emissions but it will also reduce the life cycle environmental impacts. In line with this, the comparative gate-to-gate LCA depicts that the light fossil fuels contribute more than biomass briquettes for all impact categories except for "Non-carcinogens" (6.28E04 kg C2H3Cleq), "Aquatic ecotoxicity" (1.01E-02 kg TEG water), "Terrestrial ecotoxicity" (5.04E-02 kg TEG soil), and "Land occupation" (9.37E-03 m2org.able) impact categories because of the burning process. Thus by expanding the level of replacement of logs and light fossil fuels, the impacts on human health, resources, and climate change will be minimized and the quality of ecosystem will be improved. This overall outcome is mainly linked to the fact that biomass briquettes are used as a replacement to traditionally adopted energy sources while reducing burning activities in the field. Consequently, the introduction of biomass briquettes 14
Journal Pre-proof as a replacement of these two existing heating means would result in overall improved environmental properties. Additionally, in the near future, a research study on Lebanese stoves will be conducted to evaluate the best means to control emissions related to their use and thus reduce the environmental impact of the consumption stage. Finally, a cradle-to-grave LCA study will be performed to assess the environmental impacts of light fossil fuels from raw material extraction to the end-of-life stage. 5
Acknowledgement
This study is part of the Sustainable Action for Bioenergy Production (SABioP) project funded by The European Union (Contract Number: ENPI/2014/354 - 063) and implemented by The University of Balamand in partnership with Koura Municipalities Union and El Koura Development Council. This publication has been produced with the assistance of the European Union. The contents of this publication are the sole responsibility of the authors and can in no way be taken to reflect the views of the European Union. 6
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Declaration of interests ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
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1. Sabine Saba Conceptualization, Methodology, Formal Analysis, Writing - Review & Editing.
2. Makram El Bachawati Software, Formal Analysis, Data Curation, Writing - Original Draft, Writing - Review & Editing.
3. Mike Malek Methodology, Investigation, Writing - Original Draft.