Investigating the integration between life cycle thinking, green chemistry principles and sustainability policies

. Green chemistry and life cycle assessment are two methodologies used in environmental studies, both theoretically and practically. The purpose of this analysis was to assess whether and how green chemistry principles could be integrated into the life cycle assessment methodology and to local and international industrial policies to achieve sustainability goals at the territorial level. First, some contributions that life-cycle thinking gives to green chemistry and vice versa are proposed, based on existing research. Data are provided using tables to summarise contents and graphs to outline interconnections, also considering the four steps of life cycle assessment, showing some available references of previous studies. Secondly, some possible points of integration between the 12 principles of green chemistry and environmental policies are listed. For each principle of green chemistry, a possible integration with international and local strategies is proposed. A list of references that might be useful to investigate possible patterns of study for territorial and industrial uses, is provided too. The results show that life cycle thinking and green chemistry can be integrated into theoretical and practical case studies, since many interconnections exist. These interconnections permit one to use the best characteristics of each method to improve the reliability of the other method and, finally, to solve environmental, industrial, and engineering problems with a more comprehensive approach. In addition, green chemistry principles can be easily associated with main environmental policies at the international, national, regional, and local levels. This allows one to use results, knowledge, and expertise of the green chemistry framework and apply them to industries, territories, and communities. The similarities highlighted in this analysis need further investigation in future studies since they can help decision making process in sustainability policies.


Introduction
Many tools and approaches have been proposed to promote and measure sustainable development, both by policy makers and by the academy 2 . However, different approaches may lead to different priorities and results 3 . Thus, integration or a combination of different tools offers a wider perspective on the effects of policies. Green chemistry (GC), defined as the design of chemical products and processes that reduce or eliminate the use or generation of hazardous substances, and life cycle assessment (LCA), defined as the compilation and evaluation of the input, output, and the potential environmental impacts of a product system throughout its life cycle, are two leading methodologies in the approach to environmental sustainability and accounting 4,5 .
The purpose of the present analysis was to assess whether and how green chemistry principles might be integrated into LCA methodology and local and international industrial policies to evaluate best priorities and achieve sustainability goals at the territorial level.

Materials and method
This study was conducted by analyzing existing publications in two leading databases, Scopus and Web of Science 6 in September 2020. A literature review was performed, using keywords, as "green chemistry", "life cycle assessment", "LCA", "life cycle thinking", "LCT", "policies". Relevant publications sorted were grouped into areas and briefly examined.
The analysis consisted of two parts. First, some contributions that life cycle thinking (LCT) may give to green chemistry, and vice versa, were proposed. Second, some possible points of integration between green chemistry and policies were listed. Data, contents, and available references were summarized using tables and graphs. The information collected provides some suggestions for further systematic reviews and for future research agenda.

Integration between green chemistry and life cycle thinking
The results of the literature review confirm that LCA and Green Chemistry can be integrated, combined and used together in theoretical studies and practical policies 7 .
In fact, some key features are shared in the two methodologies: the scientific method, the comprehensiveness approach, the key role of prevention, the minimisation of waste, the optimisation of processes, the effort to achieve environmental gains and more sustainable development preserving technical characteristics of products, services, and organisations. Figure 1 illustrates possible interconnections between the twelve green chemistry principles and the four phases of LCA defined by the ISO 14040 international standards. Each phase of LCA can be linked to many principles of Green Chemistry (GC).
In detail, novel system boundaries of LCA studies and original framework for interpreting results can be suggested by green chemistry approach. Moreover, data from green chemistry studies can be useful for populating inventory databases and impact assessment factors. On the other hand, Table 1 shows that, for each principle of green chemistry, some LCA studies have been performed. Some principles dealing with waste management (Principle 1 and 10 for example) have been deeply investigated through many LCA studies. Other principles are less investigated through LCT (i.e. 5 and 8). Therefore, integration and a combination between LCA and green chemistry are possible and desirable and new fields of research and exploring challenging perspectives are open. 2. Synthetic methods should be designed to maximise the incorporation of all materials used in the process into the final product (atom economy) LCA used at micro-level  possibility of implementation of micro-LCA 9 10 3. Wherever practicable, synthetic methodologies should be designed to use and generate substances that possess little or no toxicity to human health and the environment Accounting of Human Health impact using impact assessment models and characterisation factors 11 4. Chemical products should be designed to preserve efficacy of function while reducing toxicity Accounting of toxicity to water, air and soil (impact assessment models and characterisation factors) 12 5. The use of auxiliary substances (e.g. solvents, separating agents) should be made unnecessary wherever possible and innocuous when used Calculation of impacts of auxiliary substances in a life cycle perspective 13 6. Energy requirements should be recognized for their environmental and economic impacts and should be minimized Material, energy flow, global warming potential accounting, energy use and other impact assessment categories such as ionizing radiation, cumulative energy demand etc. 14 7. A raw material or feedstock should be renewable rather than depleting, wherever technically and economically practicable Use of renewable and non-renewable sources with a LCT approach 15 8. Unnecessary derivatization (blocking group, protection/deprotection, temporary modification of physical/chemical processes) should be avoided whenever possible Life cycle perspective in processes application 16 Principle of Green Chemistry LCA methodology 9. Catalytic reagents (as selective as possible) are superior to stoichiometric reagents LCA for analysis of syntheses and chemical reactions 17 10. Chemical products should be designed so that at the end of their function they do not persist in the environment and break down into innocuous degradation products Impact category of waste. LCA of overall waste management 18 11. Analytical methodologies need to be further developed to allow for real-time, in-process monitoring, and control prior to the formation of hazardous substances These methodologies allow the collection of inventory data 19 12. Substances and the form of a substance used in a chemical process should be chosen so as to minimize the potential for chemical accidents, including releases, explosions and fires Integration with health and safetyneed of integrating environmental aspects with safety ones 20

Green chemistry and policies in a life cycle perspective
Green chemistry and LCT appear useful in evaluating improvements in environmental policies and promoting more sustainable strategies. In Table 2, a possible integration between the twelve principles of green chemistry (GCP) and policies is proposed. A preliminary list of references (Ref.) that might be useful to investigate possible patterns of study is provided too.

GCP International policies
Local policies Ref.

Policy of Prevention of waste
Stop the growing trend of waste production in city 21 2 Circular Economy Promotion of districts and industrial clusters 22,23 3 REACH framework and policies on chemicals Cooperation with regional Universities for new design of chemicals and products 24 4 Industrial strategies Cooperation with near firms to improve processes 25

REACH framework and policies on chemicals
Monitoring of material flows. Incentives for innovation at regional and national levels 26 6 Policies on Climate change Energy manager in private and public sector 27 7 Renewable resources support Local circular flows for biomaterials and biowaste [28][29] 8 Optimisation, technology, information technology Cooperation with Universities for new design and with factories to implement processes 30 9 Industrial policies, incentives Cooperation with Universities for new synthesis processes [31][32][33] 10 Plastic reduction policies End of waste framework 34 11 International monitoring of pollutants in atmosphere Monitoring of substances by local agencies and by enterprises 35 12 Policies for high-risk sites Local plans for emergency in high-risk factories 36 On the other hand, Figure 2 illustrates possible interconnections between environmental strategies and green chemistry principles and gives a visual suggestion of the comprehensive strategy.

Figure 2. Environmental strategies and twelve green chemistry principles (GC)
In a broader context, the combination of different environmental tools and frameworks is particularly interesting and desirable to have a more complete picture of the strategies analysed and to minimise rebound effects and promote fair communication 37 and true sustainability 38 .

Conclusions
Raw material shortages and planetary boundaries' awareness have promoted, in the last decades, international and local policies to become more and more environmentally sustainability oriented. Life cycle assessment is a leading method used globally for environmental studies in many fields, including organisations and territories. Moreover, green chemistry principles are scientifically robust and widely applied in the international community to improve environmental sustainability of products and processes. The possibility of integration between life cycle thinking and green chemistry is investigated through a brief literature review. This analysis shows that life cycle thinking can be profitably mingled with green chemistry principles, and vice-versa. These interconnections permit to use the best characteristics of each method to improve the reliability of the other method and finally, to assess environmental problem with a more comprehensive approach. Moreover, green chemistry principles can be easily connected to main strategies at international, national, regional, and local levels. This permits to use results, knowledge, and expertise of the green chemistry framework and to apply them to territories and communities in a life cycle perspective. Findings are usable and thought-provoking both for researchers and for decision makers. The combination of local policies, life cycle assessment and green chemistry needs further investigation since it might help decision making processes based on sustainability issues, technical data, and interdisciplinary consensus.