1 Introduction

The chemical industry is grappling with a notable issue concerning solvents, particularly organic variants used in synthesis and purification. These solvents ultimately become waste, leading to significant environmental harm. Managing waste solvents provides a means to mitigate the generation of hazardous waste, thus reducing the discharge of toxic substances into the environment. This objective is aligned with the overarching aim of developing environmentally sustainable products and processes. However, the management of waste solvents is further influenced by other factors such as economic considerations, logistics handling, adherence to legal guidelines, storage capacity, costs, and the availability of existing on-site technologies [1]. Hazardous waste typically encompasses noxious compounds like benzene, diethyl ether, nitromethane, and Adsorbable Organic Halogens (AOX) such as chloroform, tetrachloromethane, 1,2-dichloroethane, additionally, complex organic molecules like dioxins and furans, also demand attention. AOX refers to halogenated organic compounds, including chlorinated, brominated, and iodized, capable of adsorption on activated carbon [2]. Most AOX exhibit toxicity, mutagenicity, and carcinogenicity at elevated concentrations [3, 4]. They possess extended half-life periods and significant lipophilicity, enabling their accumulation within food chains. The European Commission added numerous adsorbable organic chlorines to the list of hazardous substances in 1976. Under the Stockholm Convention, twenty-three AOX compounds are categorized as persistent organic pollutants [5]. Although, multiple methods for treating chemical wastewater, only a handful are employed to recover AOX wastewater, e.g., distillation [6], nanofiltration [7], extraction [8], adsorption [9], electrocoagulation [10], and electrooxidation [11].

Distillation operates on the principle of varying substance volatility to achieve separation. The more volatile element evaporates by heating a mixture of volatile components, forming vapor that is then condensed to yield the distillate. Consequently, the mixture's boiling point gradually increases due to the declining presence of the more volatile component in the distillate and residual components. The distillation features typically contain a metal cylinder, termed a column, housing plates, or fillers, ensuring extensive vapor–liquid interaction. This technique is a prevalent physicochemical method for wastewater treatment. Its merits include efficient material recovery, potential organic disposal, recyclable distilled substances, concentrated contaminant collection, and reasonable investment costs adaptable to diverse industrial contexts [12]. However, this method is found to be less effective against azeotropic mixtures in which component boiling points closely align [13]. This inefficiency demands a substantial amount of energy and often necessitates additional treatment methods, such as incineration [14].

Life Cycle Assessment (LCA) strives to provide a thorough evaluation of the environmental consequences associated with products and services from a complete life cycle standpoint [15]. Over the past few decades, the LCA methodology has undergone growth and maturation [16]. Present endeavors focused on areas like databases, quality assurance, methodological consistency, and harmonization further propel this progress [17; 18]. LCA finds application across an extensive array of sectors by governmental bodies, non-governmental entities, and industries [19]. This utilization occurs independently or with the support of research institutions or consulting firms. However, the LCA methodology has limitations affecting LCA results [20]. LCA doesn't cover later product use impacts. Gathering inventory data is costly and uncertain, making it impractical to consider every aspect of a process. Choosing impact categories is subjective and narrows the sustainability perspective. Weighting methods and normalization are subjective, leading to differing stakeholder interpretations.

Researchers are increasingly focusing on the LCA methodology for distillation, with particular emphasis on its direction. Chao Guo et al. [21] conducted the LCA analysis to assess the environmental effects of extractive distillation. This process employed various ionic liquids (ILs) to separate a methanol/dimethyl carbonate mixture. The evaluation was executed through SimaPro 9.0 software. The investigation encompassed the climate change impacts of purifying 1 kg of 99.9 wt% DMC utilizing diverse IL types. The calculated range for CO2-equivalent emissions was between 6.58 × 10–1 and 2.09 × 100 kg CO2-eq. The quest for alternative materials in the manufacturing of distillation columns is the growing necessity to promote actively. Cunha et al. (2018) studied nine polymeric materials as potential replacements for stainless steel in column fabrication, in which high-density polyethylene (HDPE) and polypropylene (PP) showed promising results [22]. In another their study, they found that substituting stainless steel with PP generally leads to lower environmental impacts in nearly all categories based on the CML 2 method, with an average 86% reduction. Greater reductions may occur with renewable PP [23]. Distillation has gained growing prominence within the chemical industry, with its environmental consequences varying depending on the specific application. Nonetheless, assessments of distillation using the LCA method offer a comprehensive insight into its overall environmental footprint. This is a foundational step in determining whether to pursue or establish a "Net Zero Emissions" objective.

The pharmaceutical industry generates substantial AOX-contaminated wastewater, yet AOX in this context lacks thorough research, and the environmental efficiency of its removal methods remains unexplored. Understanding and addressing AOX's presence in pharmaceutical wastewater is vital to devise effective mitigation strategies. While previous studies on distillation have focused on specific phases, such as operation or production, this study fills a research gap by examining the 'gate-to-gate' environmental impacts of distillation, covering the entire process from manufacturing to operation for AOX removal in pharmaceutical wastewater. In addition to presenting a method for removing AOX compounds from industrial wastewater, this article assesses their environmental and human health impacts. The research also introduces innovative approaches to reduce the environmental impact of distillation, including material substitution, heat integration, and the integration of renewable energy. Furthermore, the study broadens the evaluation by considering the substitution of hard coal-generated electricity with alternative sources like solar, onshore wind, and offshore wind in the distillation process's environmental aspects.

2 Methodology

The approach employed in this research adhered to the procedures outlined in LCA according to ISO 14040:2006 [24] and ISO 14044:2006 [25] standards. Implementing LCA involves four key stages: defining goal and scope; conducting a life cycle inventory analysis; performing a life cycle impact assessment; and interpreting the result [19; 26; 18; 27].

2.1 Goal and scope

This study focused on using LCA to identify the environmental impact of distillation technology in the distillation tray column manufacturing process and the application of distillation to AOX-containing wastewater treatment. The system boundary of distillation technology for AOX treatment is shown in Fig. 1, indicated by dashed lines. The study covered the manufacturing and operational phases of the process, which included chemical intake and energy requirements, known as 'gate-to-gate' analysis. The manufacturing phase considered from the extraction of raw materials, through to the necessary steps to produce columns, for example dimensioning, cutting, molding, stamping, welding, assembly, and final details.

Fig. 1
figure 1

System boundary of distillation for AOX treatment

Full size image

The functional unit (FU) was specified as 1 kg of treated effluent containing less than 8 ppm AOX and less than 1000 mg O2/L COD. These are the respective emission limit values in the Hungarian Ministry of the Environment Regulation 28/2004 (XII. 25.) [28], and it is in accordance with the EU industrial emission limits in Directive 2010/75/EU [29].

This approach can be used with input effluents featuring varying AOX concentrations. However, determining whether the resulting effluent quality meets the permissible limits necessitates expert judgment and, if necessary, recommending supplementary treatment methods [30].

2.2 Life cycle inventory

Table 1 presents the summary of life cycle inventory data, while a comprehensive version of the life cycle inventory (LCI) can be found in Table S1 within the Supplementary Materials. The data of distillation column production was calculated based on published work by M. Brondani et al. [31] at the Chemical Engineering Laboratory and the Federal University of Santa Maria. The continuously operated column with a total weight of 362.67 kg and an operating pressure of 101.325 kPa. The distillation is expected to operate for 10 years, with an annual operating time of 8,000 h/year and an operating capacity of 15 L/h.

Table 1 Life cycle inventory data
Full size table

During the AOX treatment phase, the data on the composition of the pharmaceutical wastewater was obtained from the monitoring results submitted to Budapest Sewage Works Ltd. by the Environmental Protection Department of the pharmaceutical factory [32]. The AOX compound in pharmaceutical wastewater included Dichloromethane, Trichloroethylene, 1,2-Dichloroethane, Chloroform, Tetrachloroethylene, 1,1,2-Trichloroethane, and Carbon tetrachloride, as can be seen in Table 1. The optimization process within Aspen Plus software V10 involved utilizing the distillation column model. The outcomes of this model highlighted that the most efficient configuration for the distillation column entailed specific parameters: introducing the inlet stream at the 10th plate with conditions of 30 °C and 1 bar pressure; arranging 20 plates within the column; and establishing a reflux ratio of 10. The global energy mix composition was considered during the life cycle analysis.

2.3 Life cycle impact assessment

2.3.1 EF 3.0 method

The Environmental Footprint (EF) database supports applying rules for organization and product environmental footprints [34]. Following the European Commission's endorsement, the EF method is advised for evaluating environmental performance across products and organizations throughout their life cycles. This approach covers 28 impact categories, including climate change, human toxicity, ecotoxicity, and resource usage, focusing on human toxicity, ecotoxicity, and land use. The Comparative Toxic Unit (CTUh) measures human toxicity impact, expressed as cases per kilogram of emitted chemical per mass unit, indicating illness increase in the global human population. The CTUe metric (PAF.m3.year/kg) quantifies toxic impact on ecosystems by integrating Potentially Affected Fraction (PAF) over time. Climate change impact is assessed using Global Warming Potential, quantifying greenhouse gases (GHGs) over a 100-year span in CO2 equivalent kilograms.

2.3.2 ReCiPe 2016 Endpoint (H)

The ReCiPe 2016 V1.06 addresses eighteen midpoint impact categories related to problems and three endpoint impact categories related to harms. These impacts are assessed from three global viewpoints: hierarchical (H), egalitarianism (E), and individualism (I). ReCiPe 2016 offers characterization factors that accurately represent global considerations. Within the ReCiPe2016 framework, the protection of endpoints revolves around three core areas: human health, ecosystem quality, and resource scarcity [35]. In human health, DALYs (disability-adjusted life years) are used to measure the years lost or the years a person spends disabled due to disease or accidents. Ecosystem quality is evaluated using a unit called "species.year", which combines the impact of species loss across terrestrial, freshwater, and marine ecosystems over time. Resource scarcity is quantified in dollars (USD), representing the additional costs associated with the future extraction of mineral and fossil resources. This study uses a hierarchical perspective to apply the ReCiPe 2016 Endpoint (H) V1.06 methodology. This perspective employs commonly used policy principles considering factors like timeframe and other relevant issues.

2.3.3 Uncertainty analysis

Uncertainty in LCAs is often overlooked, despite substantial efforts in defining sources and expressing uncertainty. This uncertainty stems from insufficient or inaccurate data [15]. Open-access LCA databases lack uncertainty details, presenting only average stock data in the LCI phase. Various uncertainty analysis methods exist for Life Cycle Inventory Assessment (LCIA), with Monte Carlo simulation being widely considered, now incorporated in software like SimaPro. Despite availability, it's sparingly used. This study deploys SimaPro V9.3.0.3 for uncertainty analysis, utilizing Monte Carlo Simulations (MCS) in 10,000 runs at a 95% confidence level to quantify uncertainty.

3 Results and discussion

Tables 2 and 3 show the results of the Life cycle impact assessment obtained using the EF 3.0 and ReCiPe 2016 Endpoint (H) method for the distillation column application in AOX treatment from pharmaceutical wastewater, respectively. The climate change impact of the investigated technology's manufacturing and operation phases was evaluated using the EF 3.0 method. The process emits 1.11 × 10–2 kg of CO2-eq per FU. This emission comprises 1.02 × 10–2 kg of CO2-Eq. (91.9%) from the operational process and 9.00 × 10–4 kg of CO2-Eq. (8.1%) from the production process. The median climate change impact, derived from distillation technology data through Monte Carlo Simulation based on the EF 3.0 method, registers at 1.11 × 10–2 kg of CO2-eq, with a standard deviation of 2.81 × 10–3. As illustrated in Fig. 2, the uncertainty simulations adhere to a normal distribution with a 95% confidence level. The Coefficient of Variation (CV) signifies the normalized dispersion within category indicator outcomes, while SD represents the Standard Deviation, and SEM corresponds to the Standard Error of the Mean. The uncertainty findings within the climate impact category reveal that CO2 emissions fall from 5.66 × 10–3 to 1.67 × 10–2 kg CO2-eq as shown in Fig. 2a.

Table 2 Results of Impact assessment results based on EF 3.0 method (adapted)
Full size table
Table 3 Results of Impact assessment results based on ReCiPe 2016 Endpoint (H) method
Full size table
Fig. 2
figure 2

Monte Carlo analysis of distillation column: a Climate change impact based on EF 3.0 method; b Human health impact, c Ecosystems impact, and d Resources impact based on ReCiPe 2016 Endpoint (H) method

Full size image

Based on the ReCiPe 2016 Endpoint (H) method, distillation has a 2.53 × 10–8 DALY impact on human health, with SD: 6.43 × 10–9. It means the number of days spent in disease is 9.23 × 10–6 days per FU by applying distillation. The MCS findings within the Human Health Impact category reveal that human health effects lie within the range of 1.56 × 10–8 to 4.10 × 10–8 DALY, as depicted in Fig. 5b. Distillation's effect on ecosystems is 5.98 × 10–11 species.years with 1.40 × 10–11 of SD value, signifying a loss of 5.98 × 10–11 species annually per functional unit when wastewater is treated via distillation. The additional cost due to resource scarcity for distillation technology is 1.69 × 10–3 dollars, accompanied by a SD of 6.16 × 10–4. The MCS results for Ecosystems and Resources Impact fall within the range of 3.36 × 10–11 to 8.87 × 10–11 species.yr and 4.68 × 10–4 to 2.89 × 10–3 USD, respectively.

The contribution of distillation manufacturing and operation phases based on the ReCiPe 2016 Endpoint (H) method is described in Fig. 3. The results show that the operation phase occupies the dominant position in all three damage categories, accounting for over 90%, in which its contribution to human health, ecosystem, and resources is 90.5%, 93.5%, and 97.0%, respectively.

Fig. 3
figure 3

The percentage contribution of manufacturing and operation phases based on ReCiPe 2016 Endpoint (H) method

Full size image

The five highest-impact potential materials from inputs are water, methanol, dichloromethane, steel, and electricity. The percentage contribution of these for human health, ecosystems, and resources damage categories based on ReCiPe 2016 Endpoint (H) method is shown in Fig. 4. Dichloromethane significantly impacts both the human health and ecosystems categories, while methanol holds a substantial role in the resource category, with contribution percentages of 31.3%, 27.5%, and 70.6%, respectively. The damage category is notably influenced by specific energy consumption, which accounts for substantial proportions: 30.0% for human health, 21.8% for ecosystems, and 9.0% for resources. Water also plays a pivotal role in the overall impact, with repercussions of 23.2% on ecosystems and 9.8% on human health. Although steel constitutes 80% of the total material volume for distillation column production, its contribution to the three damage categories remains under 6%. As a result, prioritizing assessments for mitigating environmental impact during manufacturing and operation phases should focus on these materials. By curbing the utilization of these materials and substituting them with environmentally friendly or renewable energy sources featuring lower environmental impacts in their production processes, positive environmental enhancements can be achieved.

Fig. 4
figure 4

The percentage contribution of materials based on ReCiPe 2016 Endpoint (H) method

Full size image

The ReCiPe 2016 Endpoint (H) modelling outcomes demonstrate that steel, dichloromethane, and methanol contribute to 54.1%, 19.0%, and 9.62% of human carcinogenicity in that order. Methanol constitutes 0.443 wt% of the feed stream's weight, whereas AOX compounds are present at a concentration of 0.102 wt%, with dichloromethane being among them. Methanol plays a substantial role, accounting for more than 70% of the damage to resource availability, as seen in Fig. 4. This is primarily due to conventional methods of methanol production, which rely on fossil fuels like coal, petroleum oil, coke oven gas, and natural gas [36]. Additionally, resource damage pertains to two environmental issues: scarcity of mineral resources and scarcity of fossil resources. Producing methanol from coal necessitates considerable energy and water usage, resulting in noteworthy greenhouse gas emissions. The extent of GHGs from methanol production varies based on process design and input materials, spanning from 20.9 to 45.4 kg CO2/GJ [37]. To mitigate the impact of methanol and dichloromethane, effective wastewater purification technologies, optimization of reuse practices, and the minimization of harmful substances released into the environment offer promising solutions. Researching sustainable methanol production methods and alternative materials for column construction, especially the outer structure, presents ongoing challenges in future studies.

Resizing the distillation process can yield significant reductions in its negative environmental impact. The distillation is projected to run for 10 years, operating for 8,000 h/year at a capacity of 15 L/hour. In this production, for every 1 kg of treated effluent, approximately 9.00 × 10–4 kg of CO2-eq is emitted. Another study by Miranda et al. [38] examined distillation with an efficiency of 10,944 kg/L, operating for 7,920 h per year over 10 years. The assessment utilized the LCA method using GaBi 6.0 software. The results revealed that despite 40 times increase in distillation weight, the emissions of CO2 per 1 kg of treated effluent were reduced by 4.7 times, reaching only 1.94 × 10–4 kg of CO2-eq.

The distillation procedure consumes a significant amount of energy and emits notable levels of CO2. Strategies such as harnessing waste heat, heat-integrated systems, adopting high-efficiency generation methods, and integrating renewable energy can effectively reduce energy consumption. The CO2 emissions associated with the current crude oil distillation process and an improved unit featuring an integrated gas turbine were calculated by M. Gadalla et al. [39]. The findings indicate that modifying the process conditions alone can lead to a 22% reduction in total CO2 emissions from the existing crude oil unit. Furthermore, incorporating a gas turbine increases the potential reduction to 48%. Notably, this transition yields substantial reductions in operating costs and energy consumption, achieved with relatively modest capital investment and a short payback period. The optimized distillation process featuring an integrated gas turbine can lead to a substantial 19.4% decrease in total energy consumption.

The incorporation of electricity generated from alternative energy systems into distillation has the potential to lower costs, reduce reliance on fossil fuels, and mitigate adverse effects on human health, ecosystems, and resources. The Net Zero Emissions by 2050 Scenario (NZE) [40] is an International Energy Agency (IEA) plan for the global energy sector to achieve net zero CO2 emissions by 2050, with advanced economies leading. Wind and solar power are key in the NZE. Onshore wind is established with a global supply chain, while offshore wind rapidly grows due to strong sea winds. Meeting NZE's wind energy goals requires increased support for both onshore and offshore farms. Solar energy is also surging globally, especially in Europe. Therefore, this research focuses on the impact of renewable energy: solar, offshore wind, and onshore wind. Substituting hard coal with solar energy, offshore wind, and onshore wind can lead to a significant reduction in climate change impact by 64.3%, 62.9%, and 62.8%, respectively. Figure 5 illustrates the results of the environmental impact evaluation for the distillation process combined with energy alternatives for AOX treatment, using the ReCiPe 2016 Endpoint (H) method. While the disparity between the three renewable energy sources is not substantial, it's evident that these sources offer distinct benefits in terms of their impact on human health and ecosystems, reducing this impact by approximately 1.5 to 1.7 times compared to hard coal. When evaluating the human health impact of hard coal as 100.0%, the corresponding values for solar energy, onshore wind, and offshore wind would be 61.7%, 60.0%, and 59.7%, respectively. Just like its effect on the ecosystem, the impact of solar energy is diminished to 68.3%, while onshore and offshore wind energy registers an impact of 67.0%. The transition to renewable energy doesn't bring about significant changes in resource impact, as energy only constitutes 9.0% of the overall resource impact, as illustrated in Fig. 5. Compared to hard coal, the shift to solar energy led to a mere 4.9% reduction in resource impact, while adopting two variants of wind energy—offshore and onshore—led to a slightly higher reduction of 5.5%. When considering the comprehensive assessment of impacts on human health, ecosystems, and resources, it becomes evident that wind energy has a lesser impact compared to solar energy. To be more precise, onshore wind energy can be identified as having the smallest impact.

Fig. 5
figure 5

Results of environmental impact assessment of distillation process energy alternatives based on ReCiPe 2016 Endpoint (H) method

Full size image

4 Conclusion

The 'gate-to-gate' LCA has been presented to study the environmental implications of distillation technology from manufacturing to operation for AOX removal from pharmaceutical process wastewater. Notably energy-intensive, the distillation process contributes significantly to CO2 emissions, releasing 1.11 × 10–2 kg CO2-eq per functional unit using the EF 3.0 method. An uncertainty analysis of climate impact demonstrates a range from 5.66 × 10–3 to 1.67 × 10–2 kg CO2-eq, accompanied by a standard deviation of 2.81 × 10–3 kg CO2-eq. Employing the ReCiPe 2016 Endpoint (H) method, the operational phase predominates across three damage categories, accounting for over 90%. Its impact on human health, ecosystems, and resources registers at 90.5%, 93.5%, and 97.0%, respectively.

To address environmental impacts during the manufacturing and operational stages requires specific actions directed at water, methanol, dichloromethane, steel, and electricity. Substituting these materials with more environmentally friendly alternatives or adopting renewable energy sources characterized by lower production-related environmental effects can result in favorable improvements. Transitioning from hard coal to solar, offshore wind, or onshore wind energy stands out as a notable measure to reduce climate change impact by around one-third.

Finally, it's essential to acknowledge certain limitations. This study focuses on the manufacturing to operational phases of the distillation column, while the stages involving material extraction, packaging, transportation, maintenance, and disposal are excluded due to data limitations. These omitted phases can significantly impact the environment and potentially skew the results. Additionally, the assumption is that the distillation process will run for ten years, with an 8,000 h/year operational duration and 15 L/h capacity. However, the actual operating duration heavily depends on the maintenance process, which consumes energy and chemicals. Therefore, future in-depth investigations into this issue should encompass a broader range of ‘gate-to-gate' or 'cradle-to-grave' analyses of the distillation column.