Calculating the sustainability of products based on their efficiency and function

When a product is described as sustainable, it is often used qualitatively to suggest it has a lower environmental impact than other products. However, these assessments lack regional or local context. Using washing machines and water use as an example, common sustainability assessments would not consider the regional availability of water or competing water demands such as for essential food growth. Considering these aspects is important if we are to determine how much of a specific activity or product/service use is permissible without compromising local, regional, or even global safe operating limits. An assessment approach that considers the efficiency and purpose of a product/service is therefore needed. Based on the approach presented in this paper, in the UK, a typical washing machine is sustainable with respect to water use given water availability, but its carbon emissions are unsustainable given the country's net positive carbon footprint. This research can be used to communicate the environmental sustainability of products in a definitive way, avoiding subjective or misleading claims, and to enable comparisons between products

Circular economy design considerations for research and process development in the chemical sciences

A circular economy will look to chemistry to provide the basis of innovative products, made from renewable feedstocks and designed to be reused, recycled, or the feedstock renewed through natural processes. The substances that products are made of will increasingly be treated as a resource equal to the raw materials, and not just disposed of. This perspective discusses the role of chemists in a world without waste

Solvent effects in palladium catalysed cross-coupling reactions

Palladium catalysed cross-couplings reactions have been a dominant method in synthetic chemistry for decades. Despite this, the role of the solvent is often taken for granted and poorly understood. Regulations affecting some the most frequently used solvents for cross-coupling reactions are accelerating current trends towards using new types of solvents. In this review, the fundamental interactions between solvent and catalyst are explained so that it may inform the rational selection of high performance and safe solvents. The popular cross-coupling methodologies are addressed (Suzuki, Stille, Kumada, Negishi, Hiyama, Heck, Sonogashira, and Buchwald–Hartwig reactions) and novel solvents introduced

N-Butylpyrrolidinone as a dipolar aprotic solvent for organic synthesis

Dipolar aprotic solvents such as N-methylpyrrolidinone (or 1-methyl-2-pyrrolidone (NMP)) are under increasing pressure from environmental regulation. NMP is a known reproductive toxin and has been placed on the EU “Substances of Very High Concern” list. Accordingly there is an urgent need for non-toxic alternatives to the dipolar aprotic solvents. N-Butylpyrrolidinone, although structurally similar to NMP, is not mutagenic or reprotoxic, yet retains many of the characteristics of a dipolar aprotic solvent. This work introduces N-butylpyrrolidinone as a new solvent for cross-coupling reactions and other syntheses typically requiring a conventional dipolar aprotic solvent

A circular economy metric to determine sustainable resource use illustrated with neodymium for wind turbines

The finite capacity of the Earth to provide the resources needed to make products is beginning to dictate policy decisions and citizen behaviours. Herein a methodology is proposed that considers the function (i.e., efficiency and durability) of a product as a way of normalising and hence justifying its resource use. Titled ‘Performance-weighted abiotic Resource Depletion’ (PwRD), this approach allows the resource use of different products to be directly compared, analogous to an absolute sustainability assessment. The PwRD metric quantifies concerns over the supply risk of elements and indicates reasonable actions to sustain a circular economy. This new format of circularity indicator is explained with the case study of neodymium for wind turbine magnets. Individual products as well as larger infrastructure projects such as wind farms can be assessed. It was found that the electrical energy produced by a wind turbine in the USA does not justify the quantity of neodymium required. Demand for the function of products is a variable in PwRD and is equally important as resource use in sustaining a circular economy. In regions of low electricity demand per capita such as the Philippines and Pakistan, the same quantity of neodymium as used in a wind turbine installed in the USA was found to be acceptable for sustaining a circular economy

Cyrene™, a Sustainable Solution for Graffiti Paint Removal

Graffiti can create detrimental aesthetic and environmental damage to city infrastructure and cultural heritage and requires improved removal methods. Incumbent laser, mechanical and chemical removal techniques are often not effective, are expensive or damage the substrate. Solvents are generally hazardous and not always effective because of the insolubility of the graffiti paint. This study proposes a simple strategy for safe and effective graffiti removal, using the bio-based, non-toxic and biodegradable solvent dihydrolevoglucosenone (Cyrene™). The results showed that the type of substrate influenced the cleaning performance; in benchmark studies a non-porous substrate was easy to clean, while porous ceramic showed the presence of residual paint and yellowing when the conventional polar aprotic solvents were used. Cyrene, however, showed good removability of graffiti paint from both glazed and porous substrates, with little paint remaining in the pores of ceramic tiles. The paint suffered a reversible change in colour and a selective solubility of its components when using N-methyl-2-pyrrolidone; no changes occurred when Cyrene was used. While N-methyl-2-pyrrolidone and N,N′-dimethylformamide were only effective when neat, a Cyrene–water mixture showed some cleaning results. The performance of Cyrene was validated with Hansen solubility parameters and represents a greener and more sustainable solvent for paint removal

Safer bio-based solvents to replace toluene and tetrahydrofuran for the biocatalyzed synthesis of polyesters

With increased awareness of environmental issues caused by traditional petrochemical processes, both academia and industry are making enormous efforts towards the development of sustainable practices using renewable biomass as a feedstock. In this work, the biocatalyzed synthesis of polyesters derived from renewable monomers was performed in safer, bio-derivable organic solvents. Candida antarctica lipase B (CaLB), an enzyme belonging to the Ser-hydrolase family (adsorbed on methacrylic resin, also known as Novozym 435) was tested for its performance in the synthesis of adipate- and furandicarboxylate-based polyesters. In addition, the traditional solvents toluene and tetrahydrofuran were compared with a series of green solvents, 2,2,5,5-tetramethyloxolane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran and pinacolone for the enzymatic polymerizations. We can conclude that the monomer conversions and molecular masses of the obtained polyesters in all the tested alternative solvents were suitable, and in some cases superior, with CaLB immobilized via physisorption on acrylic resin being the optimal biocatalyst for all reactions. Strikingly, it was found that for the majority of the new solvents, lower reaction temperatures gave comparable monomer conversions and polymers with similar molecular weights whilst pinacolone yielded better polymers with Mn > 2000 Da and conversions of over 80%