Valorization of Energetic Materials from Obsolete Military Ammunition Through Life Cycle Assessment (LCA): A Circular Economy Approach to Environmental Impact Reduction

Abstract

Military ammunition and derivative materials that have reached the end of their service life are classified as hazardous waste due to the presence of explosives, necessitating proper decommissioning. Valorization of such materials through the reuse of energetic components offers a sustainable alternative, aligning with circular economy principles. This study aims to assess the environmental impact of civilian emulsion explosives (EEs) formulated with nitrocellulose powder derived from recycled ammunition, comparing these findings to traditional EEs and EEs containing standard nitrocellulose powder. The Life Cycle Analysis (LCA) was performed using the CML Baseline v3.07 methodology combined with the Ecoinvent 3.8 database, utilizing inventory data obtained from Polish sources. The results indicate that incorporating nitrocellulose powder into conventional EEs increases the overall environmental impact by 4.5%, while utilizing recycled nitrocellulose powder reduces the impact by 4.99%. This highlights the environmental benefits of recycling energetic materials for use in civilian applications, as it not only reduces hazardous waste and reliance on virgin materials but also supports the principles of the circular economy. By closing the loop on material use, this approach promotes environmental sustainability and resource efficiency, aligning with broader goals of sustainable development.

1. Introduction

1.1. Transformation to a Circular Economy

Military ammunition and related derivative materials, such as explosives (e.g., TNT, RDX), structural components (e.g., casings, fuzes, primers), and chemical propellants (e.g., rocket fuels, oxidizers), are withdrawn from service when their lifespans have ended or they have become obsolete, subsequently being classified as hazardous waste. In addition, the replacement of the old weapon system with modern military technology has also led to a large accumulation of abandoned ammunition [1]. The energetic material present in military ammunition is usually in a usable state with a significant energy value; however, its direct reuse for military purposes is not cost-effective due to [2] the need to meet high safety standards and the high costs of its reuse. The disposal of these materials is necessary due to the potential for uncontrolled explosion and use in terrorist activities [2,3].

The accumulation of obsolete ammunition is exacerbated by the replacement of aging weapon systems with modern military technologies. For instance, in 2010, the U.S. Army planned to withdraw 450,000 tons of ammunition [1,2], while Germany, following reunification, had to dispose of 300,000 tons of munitions [4,5]. The disposal process, often costing approximately USD 1600 per ton, remains resource-intensive [6] and environmentally detrimental. Historically, methods such as ocean dumping and incineration have caused significant environmental damage, as evidenced by contamination in the Chesapeake Bay in the United States [7,8,9] and the Baltic Sea [7,8,9,10,11,12]. Simultaneously, the lack of innovative approaches in managing these materials results in the loss of valuable energetic resources that could otherwise be reused.

The linear model of raw material management, established during the early stages of industrialization, is characterized by the extraction of raw materials and fuels, their transformation into products, and the eventual disposal of these products as waste once they are no longer functional. This “take-make-dispose” consumption model operates on the assumption of an endless and economically viable availability of raw material resources. However, it fails to account for the finite nature of these resources and the detrimental environmental impact of production processes and waste generation.

The limitations of the linear consumption model have become increasingly apparent. It is no longer capable of addressing critical global challenges such as climate change, the unsustainable exploitation of natural resources, rising commodity prices, or the growing accumulation of waste [13,14,15,16,17,18]. This necessitates a transition toward more sustainable and circular approaches to resource management.

In recent decades, growing economic and environmental concerns have led to the development of a concept of sustainable economic growth, suggesting the need to replace the linear model with an alternative circular model to achieve economic, social, and environmental sustainability [18,19,20,21]. In July 2014, in the announced communication, the EU Commission recognized that it is necessary to modify the European sustainable development strategy, suggesting the acceptance of the idea of a circular economy that prefers zero waste [15,19,20,21,22,23]. A new closed-loop economic model is being implemented into the life cycle of products, materials, and resources, treating them at each stage of their life as secondary raw materials and not as waste [13,15]. The generated waste returns to the economic flow for further use, thanks to which we save energy and reduce the need for new production, the need for its disposal after decommissioning, and the amount of greenhouse gas emissions [13,17,21]. We are at the beginning of the transition to a circular economy that seems to be not only possible, but also profitable. The implementation of this idea will depend on decisions made in the field of legislation, which will make it possible to reduce problems related to the rational use of resources and limit the negative impact of manufactured products on the natural environment [13,16,17,21,24].

1.2. The Promotion of Circular Economy in the Armed Forces

In alignment with the principles of the circular economy, a novel approach is being adopted for managing obsolete military ammunition by valorizing high-energy materials derived from decommissioned munitions. This approach involves utilizing these materials in civilian emulsion explosives as an alternative to their conventional destructive disposal [22]. The circular economy represents an innovative shift for the defense sector, promoting sustainability through various strategies, including the civilian application of expired military ammunition and related materials, the creation of closed material flow loops, the deceleration of material consumption rates, the reduction in overall material flow, maintaining industrial competitiveness, minimizing environmental impacts associated with traditional disposal methods and logistics, lowering the demand for emulsion explosive matrices by reducing production and transport requirements, enhancing efficiency and material safety, optimizing the use of critical strategic materials, and ensuring the security of supply chains [21,22,25,26].

Furthermore, efforts are underway to extend circular economy practices to other areas, such as military uniforms, food rations, equipment repairability, and reverse logistics, thereby broadening the scope of sustainability in the defense sector [21,27].

The too-slow procedure for implementing the circular economy model in the armed forces can be accelerated by respecting the adopted rules and mechanisms. It is important that, in the first stage of its implementation, the focus is on closing the loop of material flow at a low level. It has been estimated that this will allow for the elimination of at least 90% of hazardous substances that cause environmental degradation [26,27,28]. The interconnection of the phases of the model, process design and sourced product, remanufacturing, waste management, and cooperation between the defense sector and other economic actors is essential for the circular economy. The above activities will have a direct impact on the defense industry of EU countries, which should become greener in order to reduce the negative impact on the natural environment [22,24,25,26,27,28]. The European Defense Agency (EDA) is an organization tasked with evaluating current requirements and guiding the development of strategic actions. These actions include leveraging the principles of the circular economy to decarbonize the military sector and enhance energy efficiency, as well as promoting the generation of energy from renewable sources [22,28].

EDA activities support the implementation of the Environment, Energy, Climate Change program and the European Green Deal project on the transition of European Union countries to a circular economy and achieving climate neutrality by 2050, as well as a new action plan for the circular economy in the defense sector [22,27].

1.3. Applications in the National Economy Explosives Obtained from Withdrawn Military Ammunition and Related Materials

The reuse of energetic materials from phased-out munitions and related materials offers several key benefits. These include a significant reduction in environmental impact across all categories of disposed ammunition when compared to conventional disposal methods, largely due to the avoidance of combustion processes and the elimination of the need to neutralize their gaseous by-products. Additionally, materials recovered from ammunition and related sources can be effectively utilized in the production of civilian explosives [22,25,27,28].

Explosives, derived from the development of military ammunition and associated materials, encompass both crushing and propelling agents. These materials are widely employed as blasting agents in industries such as mining, construction, and demolition. To fulfill these roles effectively, explosives must possess specific explosive and functional properties, as well as sufficient durability. For mining applications, this durability often needs to extend over several months [14,16,17].

Their applications include average loads for breaking oversized rock formations, standalone explosive materials directly loaded into blast holes, and as components of explosive mixtures. Furthermore, significant attention has been directed toward the potential for reusing metallic components from ammunition as a source of raw materials, offering an avenue for resource recovery and sustainability [29,30,31].

Studies on emulsion explosive compositions based on ammonium nitrate and incorporating various energetic materials, such as single-base powders, double-base powders, and TNT, have demonstrated that these materials can be added in amounts up to 20% by mass without forming new chemical compounds, and that powdered compositions exhibit higher detonation velocities and greater sensitivity to shocks compared to single-component systems, as well as that energetic materials derived from ammunition are highly compatible with emulsion-based explosive compositions [32,33].

The main objective of this study is to assess the application of circular economy principles in the management of obsolete military ammunition through the valorization of energetic materials. Specifically, the study investigates the environmental benefits of reusing nitrocellulose powder from recycled ammunition in civilian emulsion explosives (EEs). A key aspect of the study is the application of Life Cycle Assessment (LCA) methodology to quantify the environmental impacts of different circular economy strategies. This study addresses the lack of quantitative environmental analyses in the context of the circular economy. LCA modeling was employed to compare traditional ammunition disposal methods with circular alternatives, highlighting their potential to reduce hazardous waste, decrease dependence on virgin materials, and enhance environmental sustainability.

1.4. Review of Explosives Disposal Methods

Various methods have been developed over decades to address the disposal of explosives, each with distinct mechanisms, efficiencies, and environmental impacts.

• Controlled detonation in a closed chamber.

Detonation of explosives in bulk and shredded military ammunition in an amount of up to several kilograms is carried out in a closed chamber with a diameter of 1–2 m. Horizontal detonation chambers with lengths of 4 m or 8 m are used to neutralize TNT and pyrotechnic ammunition. The resulting gaseous products of detonation are subjected to a physicochemical process cleanup [25,34,35].

2.

Chemical conversion and degradation.

The initial attempts at chemically transforming demilitarized energetic materials date back to the 1920s. Among the most notable transformations are those involving the chemical modification of explosives and propellants. Two significant methods include the use of a mixture of potassium hydroxide (KOH) and humic acids, which produces Actosil fertilizer, and the application of supercritical water. The latter method, known as Supercritical Water Oxidation (SCWO), utilizes water at 374 °C and a pressure of 22.1 MPa to oxidize particularly hazardous explosive pyrotechnic compositions containing chlorine [2,3,4,6,25,36,37,38].

3.

Biological decomposition [6,25,39].

Blasting explosives are mainly organic compounds; hence, their biological biodegradation with the participation of bacteria or enzymes is possible. Biodegradation of the aqueous suspension of waste material in explosives, bacteria, and ion chlorate (VII), ClO₄⁻ can be seen as a chemical process carried out in a reactor. Typically, oxidation and biodegradation generally generate waste streams that require further processing. In the case of two-base rocket fuels, which contain in their composition toxic compounds of lead (Pb) and copper (Cu) as modifiers of the combustion process, it is necessary to use a chemical–biological method in the first stage of the decomposition process. The limitation of the biological biodegradation process is the need to adapt it to a specific energy material.

4.

Recycling [2,8,25,40,41,42,43].

The energetic materials used in military ammunition and related materials are crystalline substances, so after their removal from the shell, it is possible to purify them through recrystallization. The condition for their reuse in military ammunition is to subject them to an appropriate procedure. Economic reasons mean that this procedure is only cost-effective for the octogen.

The selection of a disposal method for explosives must consider factors such as demonstrated crushing and propelling properties, feasibility of implementation on a technical scale, and economic viability [25]. Despite various proposed disposal methods, their applicability remains limited by several factors, including the wide diversity of explosive types and quantities, the costs associated with the dismantling of military ammunition, the adverse environmental impact of gaseous decomposition products, the constrained energy yields achievable through combustion or controlled explosion, and the necessity to separate specific explosive components from mixtures that often include heavy metals, asbestos, and other hazardous substances.

1.5. Life Cycle Assessment (LCA) of Explosives as an Indicator of Their Overall Environmental Impact

The concept of the circular economy changes the life cycle of goods, materials, and resources, treating them in each subsequent life cycle as secondary raw materials and not as waste. The disposal is, in fact, the last phase of their life cycle [13,17,21]. Maintaining the highest value and utility of the product in the economy for as long as possible allows for reduced energy demand, new production and disposal after decommissioning, and greenhouse gas emissions [44].

The ISO 14040:2006 standard describes the principles and framework of a product’s Life Cycle Assessment (LCA) methodology for determining its potential impact on the environment, including the definition of the purpose and scope of LCA, Life Cycle Inventory (LCI) phase, Life Cycle Impact Assessment (LCIA) phase, LCA interpretation phase, and reporting and critical review of LCA and LCA limitations [44,45]. Life Cycle Assessment (LCA) methodology is used to assess the use of a product or resource throughout its life cycle to indicate precisely where inefficiencies occur and for an environmental impact analysis considering the total quantity of products and services necessary for its production and delivery [46]. In the case of explosives, the results of the analysis of the potential benefits of recycling are simplified by standardization for the most appropriate environmental impact categories [47]. Standardization is an additional activity in which the estimated life cycle impact of a product is expressed as fractions of the impact associated with a reference activity or specific conditions [44,45]. The LCA provides additional information by converting the inputs and outputs of inventory data into quantitative potential environmental impacts, confirming the analysis data for the combat ammunition-decommissioning process [15,17,21,23]. The optimal solution to the complex disposal problem requires a review of the entire life cycle of ammunition, and it is therefore recommended that it be possible to reverse-assemble it and recycle the components afterwards. This aspect should be taken into account by the manufacturer [15,17,23].

A Life Cycle Assessment framework for a product, process, or activity can combine the collaborative impact of supply chain partners resulting from the extraction and processing of raw materials; production, transport, and distribution; reuse, maintenance, recycling, and final disposal. This indicates that LCA is a holistic concept because it combines environmental impacts into a coherent framework [15,44,45].

The basic LCA modeling techniques used to estimate the impact of the supply chain production system are:

• “bottom-up” process models.

The LCA methodology is strictly defined by ISO standards defining the system boundaries set by the test objectives, taking into account individual impact assessments, e.g., carbon-equivalent emissions.

• “top-down” macroeconomic environmental models.

The Environmental Input-Out Methodology (ECI) is a type of LCA methodology that uses national or regional data relating to interprofessional trade flows concerning emissions at the level of a specific sector to estimate their impact on the natural environment [15,17,23,48].

A future-oriented product life cycle model is based on primary data from previous studies on the conventional disposal process and the production of explosive emulsions. The LCA model uses system expansion to calculate environmental loads that are omitted or avoided when energy material from ammunition is added to civilian explosives. The results of the LCA environmental life cycle analysis show that the valorization of energetic materials obtained from phased munitions and related materials within the circular economy significantly reduces the negative impact on the natural environment in all categories compared to conventional methods and the process and their disposal. The observed benefits result mainly from the avoidance of combustion processes and exhaust gas cleaning in the disposal of ammunition and the possibility of substituting in the production of civil explosive elements with energy material obtained from ammunition.

The currently growing production of civil explosives is caused by the demand for these materials by the mining industry and construction. Civilian explosive is an emulsion material prepared based on a matrix consisting of ammonium nitrate, water, mineral oil, emulsifier (polycarboxylate), and sensitizer. To reduce the environmental impact of the civil production of explosives, comparative studies were carried out on several explosive emulsion compositions, looking for the lowest impact on energy and the natural environment [49,50]. The impact was quantified from a life cycle perspective using the LCA methodology [45]. The conducted research has shown that the main factor contributing to the ten categories of their negative impact on the natural environment is the chemical composition of the explosive emulsion due to the production of ammonium nitrate. Growing environmental requirements have resulted in manufacturers of civil explosives being obliged to implement environmental management practices [50].

2. Materials and Methods

2.1. Goal and Scope Definition

The objective of this study is to assess and quantify the environmental impact of emulsion explosives (EEs) in the context of a circular economy approach. A comparative LCA analysis is conducted for three types of EEs with varying compositions to evaluate the environmental benefits of recycling energetic materials. The standard emulsion explosive is referred to as EE, while EEwR denotes an EE containing nitrocellulose powder and EER represents an EE incorporating nitrocellulose powder extracted from recalled ammunition, reflecting the CE principle of resource valorization by reusing waste materials in new applications. The functional unit is defined as 1000 kg of emulsion explosive material delivered to the mine and detonated. A modular approach was applied, referring to specific stages of the life cycle of emulsion explosive materials. The following stages of their life cycle were identified: A1—raw material acquisition, A2—in-plant transportation, A3—production, B1—transportation to the user, B2—loading, and C1—detonation of explosive materials. The system boundaries for EE are presented in Figure 1.

2.2. Life Cycle Inventory, Impact Assessments, and Simapro Software

Inventory data covering stages A1 to B2 for all emulsion explosives (EEs) were obtained from a Polish company specializing in the production of explosive materials. These data, collected in 2022, are presented in detail in

Table 1. Life cycle inventory of EEs under study (stages A1–B2).

Stage	Assembly	Ecoinvent Database	Quantity
			EE	EEwR	EER
A1	Ammonium nitrate [kg]	Ammonium nitrate, market for ammonium nitrate	600	560	560
	Sodium nitrate, technical grade [kg]	Sodium nitrate, market for	200	170	170
	Water [kg]	Water, decarbonized, market for water	130	100	100
	Mineral oil [kg]	White mineral oil, at plant	50	50	50
	Nitrocellulose powder [kg]	Market for cellulose, nitric acid production, market for sulfuric acid; water, decarbonized, market for water	-	100	100
	Polycarboxylate [kg]	Polycarboxylates, market for	20	20	20
A2	In-house transport [tkm]	Transport, freight, lorry, all sizes, unregulated to generic market for transport, freight, lorry, unspecified	1	1	1
A3	Electricity [kWh]	Electricity, medium voltage, market group for	140.67	195.67	195.67
	Steam [GJ]	Steam production, in chemical industry	-	4.5	4.5
B1	Transport [tkm]	Transport, freight, lorry, all sizes, unregulated to generic market for transport, freight, lorry, unspecified	100	100	100
B2	Loading [kWh]	Electricity, medium voltage, market group for	2	2	2

.

However, the data for stage C1, including the theoretical detonation parameters shown in

Table 2. Life cycle inventory of EEs under study (stage C1); g—gas, l—liquid, s—solid.

Stage	Assembly	Quantity [g/1000 kg of Explosive]		Ecoinvent Database
		EE	EEwR/EER
C1	H2O (g)	454,320	431,460	Water
	N2 (g)	242,340	236,040	Nitrogen
	CO2 (g)	195,756	226,072	Carbon dioxide
	O2 (g)	33,056	0	Oxygen
	NO (g)	1000	2	Nitrogen monoxide
	CO (g)	5	43,400	Carbon monoxide
	H2 (g)	0	47	Hydrogen
	CH2O2 (g)	0	244	Formic acid
	NH3 (g)	0	36	Ammonia
	CH2O (g)	0	1	Formaldehyde
	CH3OH (g)	0	4	Methanol
	CH4 (g)	0	84	Methane
	C2H4 (g)	0	1	Ethylene
	Na2O (l)	72,912	62,000	Sodium oxide

, were estimated using the thermochemical code CHEETAH [51] with the BKWC set of Becker–Kistiakowsky–Wilson (BKW) parameters. When describing the thermodynamic state of detonation and explosion products, one widely used equation is the BKW equation of state. The equation in thermodynamic programs is used in the form:

$${\displaystyle \frac{pV}{nRT}}=1+xexp\left(\beta x\right)$$

(1)

where: $p$—pressure, $V$—molar gas volume, R—gas constant, $n$—number of moles of the gas, and $T$—temperature.

$$x={\displaystyle \frac{k}{V{\left(T+\theta \right)}^{\alpha }}},$$

(2)

$$k=\kappa {\sum }_i{n}_i{k}_i,$$

(3)

These equations contain four parameters selected experimentally: $\alpha$ [-], $\beta$ [-], $\kappa$ [-], and $\theta$ [K]. The values of these parameters allow the form of the equation to be adjusted to the thermodynamic properties of the reactive mixture that the equation is intended to describe. The $k_i$ values are volumes characterizing the individual properties of individual components.

Impact assessment in Life Cycle Assessment (LCA) represents a crucial phase in evaluating the potential environmental impacts associated with a product or service across its entire life cycle. In this study, the Life Cycle Impact Assessment (LCIA) was performed using the CML Baseline v3.07 methodology. This approach, developed by the Center for Environmental Sciences at the University of Leiden in the Netherlands, provides a comprehensive framework for quantifying environmental impacts and facilitating the comparison of different life cycle scenarios. It is based on European regional conditions and is one of the most commonly used sets of environmental indicators for LCA studies outside of North America. The CML-IA database contains characterization factors for all baseline characterization methods mentioned in the Handbook on LCA [52]. The impact categories under study are summarized in

Table 3. Impact categories of the CML baseline methodology.

Impact Category	Unit	Definition
Abiotic depletion	kg Sb eq	Depletion of non-renewable resources, such as metals and minerals, measured in antimony equivalents (Sb)
Abiotic depletion (fossil fuels)	MJ	Depletion of fossil fuels as an energy source, measured in megajoules (MJ)
Global warming (GWP100a)	kg CO2 eq	Potential for global warming due to greenhouse gas emissions, measured in CO2 equivalents
Ozone layer depletion (ODP)	kg CFC-11 eq	Impact on ozone layer degradation, measured in CFC-11 equivalents
Human toxicity	kg 1,4-DB eq	Negative effects of emissions on human health, measured in 1,4-dichlorobenzene (1,4-DB) equivalents
Fresh water aquatic ecotoxicity	kg 1,4-DB eq	Toxicity of emissions to freshwater aquatic organisms, measured in 1,4-DB equivalents
Marine aquatic ecotoxicity	kg 1,4-DB eq	Toxicity of emissions to marine aquatic organisms, measured in 1,4-DB equivalents
Terrestrial ecotoxicity	kg 1,4-DB eq	Toxicity of emissions to terrestrial organisms, measured in 1,4-DB equivalents
Photochemical oxidation	kg C2H4 eq	Formation of ground-level ozone (photochemical smog), measured in ethylene (C2H4) equivalents
Acidification	kg SO2 eq	Potential for environmental acidification (soil, water), measured in sulfur dioxide (SO2) equivalents
Eutrophication	kg PO43− eq	Enrichment of aquatic ecosystems with nutrients, leading to overgrowth of algae, measured in phosphate (PO43−) equivalents

. The CML Baseline methodology primarily focuses on midpoint indicators, which may limit its capacity to provide a holistic assessment of endpoint impacts, such as damage to human health or ecosystems. This approach restricts the ability to link specific environmental interventions to ultimate consequences, which can be a disadvantage in studies requiring a more comprehensive impact analysis. Compared to more comprehensive methodologies like ReCiPe or IMPACT 2002+, the CML Baseline offers a narrower scope for evaluating certain impact categories. The LCA analysis was performed using SimaPro v. 9.00.49, a professional software developed by PreConsultant. SimaPro is one of the most widely used and advanced tools for conducting LCA. It enables the calculation and analysis of environmental impacts, including carbon footprints, for products, services, and entire companies. The software provides a robust set of features, such as comprehensive tools for sustainability metrics, environmental performance analysis, and support for decision-making processes aimed at driving sustainable change. Furthermore, SimaPro integrates with multiple Life Cycle Inventory databases, thereby enhancing its utility for conducting detailed and precise LCA studies.

The analysis was supported by the use of the Ecoinvent 3.8 database, one of the most comprehensive and widely recognized LCI databases in the field. Ecoinvent provides access to over 15,000 datasets covering a wide range of industries, including energy supply, agriculture, transport, chemicals, and construction materials. The database offers different system models, such as allocation, cut-off by classification, and substitution models, which are essential for conducting detailed and accurate LCA studies. Additionally, Ecoinvent ensures compliance with ISO 14040 [53] and 14044 [54] standards, providing a reliable and standardized approach for LCA practitioners.

3. Results and Discussion

Table 4. Impact assessment results (characterization). The highest impact is presented in bold.

Impact Category	Unit	EE	EEwR	EER
Abiotic depletion	kg Sb eq	0.03	0.04	0.03
Abiotic depletion (fossil fuels)	MJ	24,208.13	33,073.60	30,932.71
Global warming (GWP100a)	kg CO2 eq	2274.26	2587.38	2297.77
Ozone layer depletion (ODP)	kg CFC-11 eq	0.00015	0.00015	0.00014
Human toxicity	kg 1,4-DB eq	1650.62	1612.60	1504.90
Fresh water aquatic ecotox.	kg 1,4-DB eq	965.57	951.46	881.01
Marine aquatic ecotoxicity	kg 1,4-DB eq	1,711,885.21	1,792,395.48	1,617,389.47
Terrestrial ecotoxicity	kg 1,4-DB eq	2.53	2.69	2.46
Photochemical oxidation	kg C2H4 eq	−0.14	2.05	2.01
Acidification	kg SO2 eq	9.65	9.72	9.15
Eutrophication	kg PO43− eq	105.82	102.95	102.65

and

Table 5. Impact assessment results (normalization). The highest impact is presented in bold.

Impact Category	EE	EEwR	EER
Abiotic depletion	1.59 × 10−10	1.83 × 10−10	1.42 × 10−10
Abiotic depletion (fossil fuels)	6.37 × 10−11	8.70 × 10−11	8.14 × 10−11
Global warming (GWP100a)	5.44 × 10−11	6.18 × 10−11	5.50 × 10−11
Ozone layer depletion (ODP)	6.54 × 10−13	6.48 × 10−13	6.34 × 10−13
Human toxicity	6.40 × 10−10	6.26 × 10−10	5.84 × 10−10
Fresh water aquatic ecotox.	4.08 × 10−10	4.03 × 10−10	3.73 × 10−10
Marine aquatic ecotoxicity	8.83 × 10−9	9.25 × 10−9	8.35 × 10−9
Terrestrial ecotoxicity	2.32 × 10−12	2.47 × 10−12	2.26× 10−12
Photochemical oxidation	−3.68 × 10−12	5.59 × 10−11	5.49 × 10−11
Acidification	4.05 × 10−11	4.07 × 10−11	3.84 × 10−11
Eutrophication	6.69 ×10−10	6.51 × 10−10	6.49 × 10−10

present the results for the characterization and normalization phases of LCA, respectively. The data indicate that marine aquatic ecotoxicity potential (MAETP) is the dominant contributor to the environmental profiles across both characterized and normalized emissions. The EEwR and EER formulations demonstrate the lowest impacts on ozone depletion, with values comparable to those of the standard EE. However, the standard EE exhibits the least negative impact on photochemical oxidation, whereas significantly higher impacts are observed for EEwR and EER in this category.

Normalization is a tool in impact assessment used to express characterization factors in a standardized manner, enabling the comparison of different impact categories. In this study, the highest and the lowest impacts were observed in the same categories for the characterized and normalized results.

Analyzing the different stages of the life cycle (A1, A3, and C1) (Figure 2), it is evident that the greatest contribution to marine aquatic ecotoxicity potential (MAETP) occurs during stages A1 and A3, while the detonation of materials (stage C1) has the most significant impact on eutrophication potential (EP). In stage A1, the material containing recycled nitrocellulose powder (EER) demonstrates the lowest impact on MAETP among the materials tested. During stage A2, the standard EE material exhibits a lower impact on MAETP compared to EEwR and EER. This is attributed to the reduced electricity consumption and the absence of steam usage in the production process. In stage C1, corresponding to detonation, the highest impact on EP is observed for all materials, although EEwR and EER exhibit slightly lower values, with reductions of approximately 2.78% for both materials compared to the standard EE.

The ozone layer depletion potential (ODP) was identified as the category with the lowest environmental impact in the LCA study during stages A1 and A3 for all analyzed materials (Figure 3). A reduction in the use of water, ammonium nitrate, and sodium nitrate, combined with the incorporation of nitrocellulose powder into the EE composition, contributed to a decrease in ODP. The use of recycled nitrocellulose powder further mitigated the impact in this category. However, in stage A3, which pertains to production processes, the ODP impact for EEwR and EER materials was slightly higher due to the increased use of steam and greater electricity consumption.

In the detonation stage (C1), the impact values for the EEwR and EER materials were identical. Among the environmental categories, the detonation process had the greatest influence on eutrophication potential, as illustrated in Figure 2 and Figure 4. Based on the data in Figure 2 and

Table 6. Impact assessment results (normalization) for the C1 stage.

Impact Category	EE	EEwR/EER
Abiotic depletion	0	0
Abiotic depletion (fossil fuels)	0	0
Global warming (GWP100a)	4.68 × 10−12	5.46 × 10−12
Ozone layer depletion (ODP)	0	0
Human toxicity	0	1.72 × 10−15
Fresh water aquatic ecotox.	0	3.49 × 10−15
Marine aquatic ecotoxicity	0	8.41 × 10−18
Terrestrial ecotoxicity	0	8.6 × 10−16
Photochemical oxidation	1.2 × 10−11	4.58 × 10−11
Acidification	3.18 × 10−12	2.48 × 10−13
Eutrophication	6.45 × 10−10	6.27 × 10−10

, EEwR and EER materials exhibited a smaller impact compared to EE only in the acidification potential category. However, their impact on photochemical oxidation potential was more than four times higher than that of EE. The incorporation of nitrocellulose powder into the composition of EE introduced additional environmental impacts, notably in categories such as human toxicity, freshwater aquatic ecotoxicity, marine aquatic ecotoxicity potential (MAETP), and terrestrial ecotoxicity.

The process contribution analysis (Figure 5) indicated that ammonium and sodium nitrates were the most significant contributors to the overall environmental burden. Notably, in the case of EEwR material, nitrocellulose accounted for 22.37% of the total impact. This contribution was reduced to 4.3% when recycled nitrocellulose powder was incorporated, as seen in the EER material, highlighting the potential environmental benefits of material recycling and its alignment with the principles of the circular economy. On the other hand, electricity consumption and polycarboxylates demonstrated the least impact on the overall environmental performance, underscoring their relatively low influence on the analyzed systems.

4. Conclusions

The disposal of explosives and products containing them, such as military ammunition and propellants, presents a significant challenge for modern waste management and recycling technologies. Traditional disposal methods, including dumping and open-pit combustion, are no longer viable due to stringent environmental protection regulations. Research and practical applications have demonstrated that the valorization of energetic materials by integrating them into civilian explosives offers a superior environmental solution, providing substantial energy, environmental, and toxicological benefits.

Life Cycle Assessment has emerged as a robust and widely accepted methodology for evaluating the environmental performance of products and processes. It plays a critical role in supporting cleaner production practices and promoting sustainable supply chains. In the context of military ammunition and related materials, LCA has proven particularly valuable in comparing conventional disposal methods with innovative, closed-loop approaches, highlighting the environmental advantages of circular economy practices.

The LCA study performed for three EEs revealed several key findings:

• All materials affect the MAETP the most, with the use of recycled nitrocellulose powder reducing the impact.
• Both EEwR and EER materials demonstrate the lowest impact on ozone depletion comparable to EE. However, EE exhibits the lowest negative impact on photochemical oxidation, with an impact comparable to EEwR and EER materials.
• The analysis of particular elements of LCA highlights the significant impact of certain stages on environmental profiles, with the detonation process notably affecting eutrophication potential.
• Individual process contributions show that ammonium and sodium nitrates significantly impact the overall environmental profile, while recycled nitrocellulose powder diminishes its impact in EEwR and EER materials.

The study concludes that the addition of nitrocellulose powder to traditional EE increases the overall environmental impact by 4.5%. In contrast, substituting the same amount with recycled nitrocellulose powder reduces the overall environmental impact by 4.99% compared to traditional EE and by 9.51% compared to EEwR materials. These findings underscore the environmental advantages of utilizing recycled energetic materials, aligning with CE goals [55] such as minimizing waste and resource consumption, while promoting more sustainable practices in the management of military related wastes.

Future study should compare the characteristics of older and modern ammunition to identify variations in composition, energy release, and environmental impact. These differences could significantly influence LCA results and the overall environmental profile, highlighting the need to adapt recycling technologies to the specific properties of contemporary ammunition. In addition, research should also consider the development of Dynamic LCA and hybrid models that integrate LCA with economic analyses to more comprehensively address the temporal and economic aspects of ammunition’s environmental impact.