Green, renewable, or low-carbon? A framework for informed solvent selection in pharmaceutical sciences.

Pharmaceutical companies have largely committed to achieving net-zero goals with both short-term and long-term science-based targets. At the same time, drug quality, safety and regulatory compliance must continue to be met. While solvent sustainability has been widely discussed, distinctions between intrinsic hazard, feedstock origin, and lifecycle emissions remain unclear in pharmaceutical contexts. One of the largest contributors to environmental impacts within the pharmaceutical supply chain are solvents. These chemicals are a major source of greenhouse gases (GHGs), resource consumption, and waste in both manufacturing operations and analytical chemistry laboratories. Such words as "green", "renewable", and "low-carbon" are often used interchangeably to refer to environmentally friendly solvents, but they represent distinct aspects of sustainability that are commonly or casually confused. Renewable solvents sometimes labelled "bio-based" or "bio-derived," are produced from a replenishable source, typically biomass. Green describes solvents being of low hazard and environmentally compatible as defined in the 12 Principles of Green Chemistry. Low-carbon solvents are those which have a lower greenhouse-gas footprint than other comparable materials when considering total material life cycle, defined as cradle (raw material extraction) to gate (production) or grave (disposal). The confusion or combination of these descriptors may lead to the lack of full carbon accounting, an inefficient solvent replacement, and false sustainability reporting. This review proposes a structured framework to differentiate green, renewable, and low-carbon solvents and discusses their implications for pharmaceutical development and analytical chemistry.