Green Chemistry

Renewable feedstocks

A raw material or feedstock should be renewable rather than depleting whenever technically and economically practicable.

Typically, chemistry uses reactants supplied by a chemical manufacturer in little white plastic bottles, or pumped in tankers depending on the scale. It is easy to forget how these chemicals were made from raw materials extracted from the Earth. Green Chemistry places a specific emphasis on renewable resources, and highlights the finite nature of the petrochemicals and minerals from which many chemicals are made.

Dependence on crude oil

Our historical and continued dependence on fossil fuels (crude oil, coal and natural gas) as a key source of carbon and energy in the production of pharmaceuticals is not sustainable. The chemical industry heavily relies on petrochemicals for its products, with resources split 50%-50% between energy and materials, making complete decarbonisation challenging. This dependence has significant environmental implications, including greenhouse gas emissions and the depletion of finite fossil fuel resources. In fact, the chemical industry is responsible for about 5% of global CO2 emissions (Gabrielli et al., 2023). To mitigate the effects of climate change the chemical industry needs to transition from fossil-based to renewable energy, and from fossil-based chemicals to renewable chemicals, as is commensurate with global net-zero strategies and the UN Sustainable Development Goals.

World and European energy use by source, courtesy of Our World in Data, licensed under Creative Commons.

Although renewable energy sources such as wind and solar power are replacing fossil fuels for energy, a source of renewable materials from which to make pharmaceuticals from is needed. The most promising option is to use biomass, which is converted into useful chemicals in a biorefinery.

Biomass: Renewable material obtained from plants or animals. Examples include whole biomass such as straw and wood, extracted substances, notably vegetable oils, and refined products such as sugars. Waste biomass (e.g. from food such as fruit peels) and agricultural residues (straw for example) avoids direct conflict with food production.

Biorefinery: A manufacturing plant that converts biomass into chemicals and/or fuels. It is analogous to an oil refinery, which converts crude oil and natural gas into other products. The most common biorefinery process is the fermentation of sugars to bioethanol (fuel).

Elemental sustainability

Within the chemical sector, including pharmaceuticals, there is a heavy reliance on petroleum feedstocks, but also various metals and other elements. The renewable energy revolution is shifting the balance even more towards metals, especially those needed for battery technology. If high demand for critical raw materials, particularly in catalysis and energy storage, goes unabated, we will run out of economically viable sources of essential materials. While we continue to mine virgin ores, labour conditions and the resulting environmental pollution and health impacts in some regions have been heavily criticised, yet demand only increases. All these factors raise serious questions over the sustainability of many vital elements.

Periodic table indicating the supply risk of the elements. Atomic number of each element are shown. An interactive periodic table is available from the RSC.

The EU has prioritised critical raw materials based on their economic importance as well as supply risk.

Supply risk measures the disruption that would be caused by the interrupted supply of a material (into the EU). This depends on the relative quantity of imports and the number of global producers of a material.

Economic importance depends on the value of the end-use applications of the materials. High value products like electronics require specific rare elements. The availability of economically-viable substitute materials is factored into this assessment, as ranked on the following chart.

Critical raw materials defined by supply risk and economic importance.

The materials of most concern are those vital to the economy with a high supply risk. The rare earth metals and platinum group metals are unsurprising examples, but also some less glamorous elements such as boron and magnesium also meet this criteria. The EU is entirely reliant on imports of these elements.

Rare earth elements are used in renewable energy generation (e.g. wind turbines) and energy storage (batteries).
Platinum group metals (platinum, palladium, ruthenium, rhodium, osmium, and iridium) find use as reaction catalysts and in electronic components.
Boron is used in magnets and some types of glass.
Magnesium features in a number of alloys and is used in steel-making.

Palladium, boron, and magnesium also have prominent uses in the chemistry required for pharmaceutical production. Please use the Royal Society of Chemistry's interactive periodic table to learn more about individual elements, their properties and their supply risk.

Elemental sustainability strategy

Broadly speaking, there are two options to improve elemental sustainability:

We can recycle materials more completely with improved waste collection and with greater efficiency to preserve the quality of those materials. A circular economy is the principle that materials are reclaimed and reused (indefinitely), therefore minimising the extraction of raw materials.
Secondly, we can replace some elements with more abundant materials, and invent alternative technologies to protect against supply risk and the depletion of finite resources. This is a topic of much interest in the field of catalysis, where conventional metal catalysts tend to be expensive and based on relatively rare elements.