Defining Sustainable Chemistry

I lost my elephant some days ago. Actually, it was an elephant keychain. This was a special present given by a Thai student who attended the Summer School on Sustainable Chemistry for Sustainable Development in July 2023, at Leuphana University, Germany, supported by the International Sustainable Chemistry Collaborative Centre (ISC3). This event focused on the foundations and applications of Sustainable Chemistry in tackling the climate crisis, a top priority requiring responsible and coordinated transnational actions on many fronts, including through high-level scientific knowledge. The chemical industry is fundamental for providing goods for other industries such as construction, pharmaceuticals, agriculture–food processing, and electronics, with a global material production capacity of around 2.3 billion tonnes in 2020 and sales of chemicals projected at almost $11.3 trillion annually by 2030. Such growth reflects the importance of the science and industrial applications, leading to remarkable opportunities to promote a better life for all, considering the United Nations (UN) Sustainable Development Goals (SDGs). However, there are also challenges and risks stemming from the energy demands, greenhouse gas emissions, and toxicity of many chemicals and their transformation products, as well as the lack of proper chemical and waste management programs in various countries.

Trying to find my keychain, I was asked to describe it: a vibrant red and green synthetic fabric, hand-made into an elephant that fits in a child’s hand. It was inevitable to connect this story with the Indian parable of the blind men who attempt to explain what an elephant is, each touching a different part of the animal, and disagreeing on their findings. I am reminded of this parable as I have been requested by many students, stakeholders, and sectors such as industries and public authorities to present an ultimate (and eager to be the definitive) definition of “Sustainable Chemistry” and its main keystones. Over the years, various concepts, terms, and definitions have emerged that, despite some differences, all trend in the same direction and broadly seek the same overall goals. The challenge is less about distinguishing and optimizing definitions than about operationalizing them.

Sustainable Chemistry is gaining momentum. For example, an August 2023 report from the US president’s National Science and Technology Council proposes “a consensus definition of Sustainable Chemistry” and “a working framework of attributes characterizing and considerations for evaluating Sustainable Chemistry.” It also mentions a landscape analysis of all US Sustainable Chemistry activities; the development of a strategic plan to characterize and assess it; coordinating efforts in the areas of regulation and research and development (R&D); and integrating Sustainable Chemistry into R&D through grants, awards, and loans, and increased workforce training and education.

According to this report, Sustainable Chemistry is the “chemistry that produces compounds or materials from building blocks, reagents, and catalysts that are readily-available and renewable, operates at optimal efficiency, and employs renewable energy sources; this includes the intentional design, manufacture, use, and end-of-life management of chemicals, materials, and products across their lifecycle that do not adversely impact human health and the environment, while promoting circularity, meeting societal needs, contributing to economic resilience, and aspiring to perpetually use elements, compounds, and materials without depletion of resources or accumulation of waste.” It is clear that this rationale was extensively negotiated but is much closer to a more traditional green chemistry definition, which is not a problem at all. On the contrary, if complete and widely adopted, green chemistry could bring about a revolution. In scientific terms, there is low novelty in the definition described in the report. Such ideas emerged in Europe and the US in the 1990s, and have been widely discussed in the literature and presented by other organizations since then. For some contemporary researchers and institutions, Sustainable Chemistry should not have a closed or hermetic explanation; instead, it should be open to new conditions, including nonchemistry-based alternatives and approaches from the social sciences.

Green chemistry, Sustainable Chemistry, circular chemistry, or even a nascent concept that could be named regenerative chemistry are platforms—or mostly academic philosophies, which are necessary intellectual exercises—with some differences, but with many convergent ambitions, visions, objectives, and methods, aiming at the design and use of healthier, fairer, safer, and more benign products and processes. This practical convergence should be our focus, not disagreements to defend tooth and nail a new version of chemistry to be called one’s own, with an expiration date. Societal trends and pressures, which one could argue prioritize appearance over substance, often contribute to the spectacle of disagreement over slogans. Such demands for new slogans, rather than actual practices, can sometimes be used as distractors, also opening up undesirable spaces for “green and sustainable washing,” misconceptions, and problems in chemistry communication, making it even more difficult for the scientific sectors, and the general public, to move forward with a greater and more positive impact. A more responsible approach to designate a field or movement collectively must incorporate the key factor of constant building together, mainly to make Sustainable Chemistry a reality.

The time for automatism of well-established institutions assuming a more conservative perspective for chemistry and its processes does not contribute to urgent and even radical transformation. To arrive at such a turning point for a fully operationalized reoriented chemical practice, it would be necessary to face a reality in which business-as-usual does not work anymore, counting on a critical mass with capacities, intentions, incentives, and technologies that can revolutionize a very complex functioning interconnected production chain to the core, not only as increments. Incremental changes are important steps, but there will have to be a tipping point when industry turns into a different, new, sustainable interconnected production chain.

As expected, there are many very good examples of chemical industries and other initiatives that have already embodied R&D in greener and more sustainable materials, processes, and services in several levels and formats—designing, developing, adopting, and even pushing advances in technosciences and regulation, as well as in education. For example, the tremendous advantages of establishing an integrated biorefinery as a zero-pollution, carbon-neutral or net zero emission system have been described in the literature but not yet completely implemented. Thus, based on a biorefinery approach to generate biobased products, bioethanol can be considered a green chemical (or renewable commodity), whose production is projected to increase to 132 billion liters by 2030. However, to be a Sustainable Chemical, many technical factors remain to be addressed—for example, the chemical nature and availability of nonedible feedstock; yield for the first and second generations of bioethanol; effectiveness of energy cogeneration using, for instance, bagasse; the high emission of CO2 derived from fermentation and cogeneration systems and ways to capture, reintegrate, or recirculate this by-product; and genetic and population dynamics of yeasts to achieve a more stable, consistent, and predictable fermentation performance.

And, critically, other factors beyond the technological must be taken into account, including environmental, economic, and even sociopolitical ones. Examples include the integrated techno-economic and environmental assessment of bioethanol generation to evaluate trade-offs; fossil-fuel–based mechanization of sugarcane production (or the absence of it); the geographic and production-line origin of the fertilizers imported by, e.g., the United States, European Union, and Brazil for crop cultivation; future regulatory constraints; and the potential decrease in the use of biofuels over the next decades with higher investments in electric or hydrogen-operated vehicles.

In times of urgency, formal definitions and common frameworks for Sustainable Chemistry can provide guidance, serving also as a tool for regulation and harmonization for those who feel lost and not grounded. However, a definitive definition does not have a long-term future. Sustainable Chemistry should always and will incorporate one fundamental element: the impulse of renovation. This could be done taking into account what should occur for vanguard science: genuine diversity of perspectives, freedom, and openness as preconditions for excellence. Last but not least: The elephant was found by my next-door neighbor. I did not lose my keys, tags, and electronic key for unlocking doors, and the keychain was always very close to me.