Year after year, the Earth Overshoot Day (i.e., the day on which humanity consumes more resources than the Earth can produce in a year) keeps advancing, and in 2023, it was 2 August. We cannot continue on this trajectory, and we need to find a way to push this day back and bring it as close as possible to 31 December.
With this in mind, the valorization of biomass – whether terrestrial or aquatic – for the production of molecules and materials appears to be an effective way of mitigating the scarcity of fossil resources. However, this use of biomass only makes sense if it does not compete with the production of food resources for humans and animals, and if these molecules and materials are sustainable (e.g., recyclable, (bio)degradable) and respectful of both people and the environment. Similarly, the production processes used must respect the principles of green chemistry and, as far as possible, be part of a biorefinery and circular economy approach (also known as ‘circular bioeconomy’) to extract maximum value from biomass components while limiting the volumes of biomass mobilized.
Although attractive on paper, the circular bioeconomy concept is far more complex and costly to implement than petro-refining, due to the complexity (heterogeneity of biomass versus homogeneity of oil, gas) and high price of biomass. The challenge is therefore considerable, and can only be met within the framework of a global, integrated and multidisciplinary approach. Indeed, setting up value chains capable of producing bio-based products from biomass calls for the fractionation and transformation of biomass components into value-added end products. Such a strategy requires a wide range of theoretical and technical skills, including:
plant (or animal) biology
(bio)chemical, thermal or mechanical fractionation in an eco-extraction approach
biological engineering and biotechnology (e.g., molecular biology, fermentations)
(bio)chemistry
green chemistry
(bio)catalysis
polymer and materials chemistry
downstream processes (e.g., membrane technologies, distillation, sub/supercritical fluids)
chemical engineering
life-cycle analysis
techno-economic analysis…
Multi-disciplinary and integrated approaches that go from biomass to bio-based end products are rarely the subject of dedicated conferences, the latter being almost exclusively mono-thematic/mono-disciplinary. Convinced of the need to offer a venue where all specialists involved in circular bioeconomy and green chemistry could come together, Professor Richard A. Gross (Rensselaer Polytechnic Institute (RPI), Troy, NY, USA) and I created the ‘Biomass to biobased chemicals and materials’ Gordon Research Conference (GRC) which was first held in 2019. Among the nine themed sessions of the second edition held in Newry, ME, USA this year (28 May–2 June), several were devoted to lignocellulosic biomass- and plants-derived polymers and materials, as well as (bio)catalysts, with stunning presentations by renowned international scientists.
Although the articles published in this Green Materials issue were not presented at the GRC, they are perfectly in line with the concepts of biobased products, green chemistry and sustainable transformation processes.
Schiff bases have been the subject of investigations on their potential as antimicrobial, antiviral and anticancer drugs. They are also used as ligands for the formation of coordination complexes used as metal-based catalysts (e.g., Jacobsen’s catalysts). Wishing to offer a greener alternative to the toxic reagents (i.e., piperidine, pyridine, metal- and halogen-containing salts) commonly used for the synthesis of N-methyl imines, which are Schiff bases, Mihankhah and Khaligh1 developed a new route for the synthesis of these imines in ethanol (green solvent) and in the presence of poly(N-vinylimidazole) as immobilized organocatalyst (PVIm). The latter proved highly efficient (yields up to 85%) thanks to its weak base properties as well as good hydrogen acceptor, proton transfer and water-trapping abilities. Moreover, as PVIm is a solid in its pure form and not soluble in n-hexane, it is not only easy to handle but can also be used in many cycles.
Still in the field of catalysts, Gholamrezaeenya et al.2 described the use of copper ferrite nanoparticles (CuFe2O4) stabilized by clinoptilolite (CP) for the synthesis of benzodiazepines, a family of depressant drugs that are widely prescribed for the treatment of anxiety disorders, seizures, insomnia and so on. Easily synthesized by the successive (i) simple mixing of copper dinitrate and hydrated iron trinitrate in Camellia sinensis leaf extract, (ii) basification and (iii) calcination, this nanocatalyst proved highly effective and provided the targets in yields up to 98%. As in the previous case, the catalyst can be easily recovered and reused (at least five times) without significant loss of activity.
With the increasing demand for battery-powered vehicles, and the potential depletion and increasing cost of lithium, the search for alternatives to current lithium-based batteries has become a great challenge. To address the latter, Guaita et al.3 investigated the selective synthesis of novel sodium iron oxide (α-NaFeO2) using a sol–gel route. This synthetic procedure provided pure small α-NaFeO2 particles with high crystallinity that exhibit a discharge capacity of about 110 mAh/g (cycled from 1 to 4 V against sodium ions/sodium), making them a very promising component for cost-effective sodium-based batteries.
Composites are ubiquitous materials – composed of two main components: fibers and resin – that find applications in numerous sectors such as automotive, aerospace and building construction. There is a growing demand for sustainable biocomposites in which the fibers, the resin or both can be potentially bio-based. Several natural lignocellulosic fibers have been extensively studied as sustainable alternatives to fossil fibers – for example, hemp, flax, jute, sisal, pineapple, curauá and coir. Although quite resistant, these fibers provide optimal thermo-mechanical properties to the resulting biocomposites only if they are efficiently blended and have maximum chemical interactions with the resin. To improve the compatibility of coir fibers (CF) with a thermoplastic polyurethane (TPU), Tayfun et al.4 conducted four different modification routes (i.e., mercerization, amino-functional silylation, bio-based epoxy resin sizing and isocyanate treatment) on CF and studied their impact on the thermo-mechanical properties of the resulting biocomposites. Whatever the treatment, the interfacial adhesion was improved and all so prepared materials exhibited improved Shore hardness and tensile strength, the hydrophobic silane-grafted CF providing the biocomposites with the lower water uptake.
Polluted industrial waters are a major concern as they generally end up in rivers and eventually in the oceans, thus causing environmental pollution at the global scale. Treating these polluted waters is therefore of great importance to keep plants and animals from harmful chemicals. Among the many industries that produce such aqueous wastes, the dyeing industry is probably one of the major ones. In their article, Wattanasiriwech et al.5 explored the production of activated biochar from macadamia husk (MHC) and its capacity to adsorb malachite green dye (MG). By optimizing the adsorption process, they succeeded in removing >99% and 75% of the MG at MG concentrations of 40 ppm and 70–80 ppm, respectively. Moreover, for the latter concentration, they found out that impregnating MHC with zinc nitrate hexahydrate allowed the increase of MG removal >99% – that is, a removal capacity of 130 mg/g of MHC.
These five research articles are perfect examples of how we, research scientists, can use biomass and natural resources to make our whole industry greener by choosing sustainable raw materials, optimizing high-yielding and greener processes, and implementing depolluting technologies, as well as enhancing chemicals’ and biomaterials’ properties.
And you, how can your research make our world safer and greener?
