Valorizing agricultural residues in polymer composites is often presented as a way to tackle two problems at once: fossil plastics and unused crop residues. This review tests that claim against the evidence. It follows up a 2020 review by the first author and asks how far the directions proposed then have been pursued, validated and taken up by industry between 2021 and 2026. A PRISMA 2020-guided search identified 105 included studies, each coded for feedstock status (field residue, processing by-product, post-consumer residue or purpose-grown comparator), matrix class, valorization pathway, scale of demonstration and environmental assessment. Physical processing (milling) and chemical surface modification (mainly alkali treatment) dominated (87% of studies). Biological and chemical conversion into new polymers remained rare. Roughly half of the composites used non-biodegradable thermoset or thermoplastic matrices. Of the 105 coded studies, 102 were laboratory-only, two reported a scale-up step, one reported a life-cycle assessment, and none reported a techno-economic assessment. Across studies, mechanical optima clustered at 10–20 wt% residue, and the optimum depended on which property was measured. Six years on, the 2020 propositions have been confirmed technically at bench scale, but they have not been validated industrially. Market uptake is limited to low-transformation fillers in commodity polymers, and bioplastics still account for only about 0.5% of plastics production. The available life-cycle evidence suggests that composites are environmentally favourable mainly when they displace virgin polymer; avoid open burning; use little chemical treatment; and do not divert residues from soil, feed or established material uses. Claims of sustainability and circularity therefore need defined benchmarks, a stated legal status for the residue and attention to its intrinsic properties. On this basis, we propose a property-led and cascade-consistent research agenda.
This study evaluates how solvent substitution, heat integration, and water integration change potential supply-chain social exposure in an avocado oil biorefinery. An attributional social life cycle assessment applies the Social Impacts Weighting Method per kilogram of oil. Indicators are assessed separately. Relative to the baseline, isopropanol substitution increases four risk indicators by 23.6–92.1% and the economic-development opportunity indicator by 24.1%. Heat and water integration reduce the risk indicators by 15.3–29.1% and 9.8–22.8%, respectively. Both also reduce opportunity-related activity. These directions persist across the tested multifunctionality approaches with the specified inventories and supplier profiles. Resource-efficiency strategies, therefore, produce different social indicator profiles. Lower opportunity-related activity does not establish a social loss, and no net social ranking follows. The findings support supplier and process screening rather than claims about observed employment, welfare, or statistical superiority.
Cement production is associated with substantial environmental impacts and remains a major challenge for industrial decarbonization. This study applied a cradle-to-gate life cycle assessment (LCA) to compare three natural-gas-based Portland cement production scenarios in the Saudi context: a baseline without CO2 capture, monoethanolamine (MEA)-based post-combustion capture, and oxyfuel combustion with CO2 capture. Environmental impacts were quantified using ReCiPe 2016 Midpoint (H) across 18 impact categories. The baseline global warming potential (GWP) was 869.89 kg CO2-eq/t cement, decreasing to 477.87 kg CO2-eq/t with MEA capture and 436.60 kg CO2-eq/t with oxyfuel capture, corresponding to reductions of 45.1% and 49.8%, respectively. However, these reductions were accompanied by increases in all other midpoint impact categories, with water consumption rising by approximately 249% for MEA and 109% for oxyfuel. Marine eutrophication also increased by approximately 137% and 33%, respectively. Under the modelled conditions, oxyfuel achieved the lowest cradle-to-gate GWP, but neither capture technology consistently resulted in lower environmental impacts than the other across all assessed impact categories, indicating that CO2 capture technology selection in the Saudi cement context should consider environmental trade-offs alongside plant-specific conditions.
Rising fossil-fuel dependence and its associated environmental burden have intensified interest in third-generation algal biodiesel feedstocks. This study screened six locally sourced algal strains (Chlamydomonas hedleyi, Nostoc commune, Tetradesmus obliquus, Ulva intestinalis, Pterocladiella capillacea, and Sargassum latifolium) from Egyptian freshwater and marine sites for lipid content and fatty acid methyl ester (FAME) profiles, and then evaluated direct dry-biomass powder blending of the high-lipid green microalga T. obliquus with the red seaweed Pterocladiella capillacea at 1:1, 1:2, and 2:1 (w/w) ratios as a low-cost strategy for upgrading biodiesel feedstock quality. T. obliquus (TET) accumulated the highest lipid content among the monocultures (26.50% dry weight), while P. capillacea (PTE) led the macroalgae (7.80%). The gravimetric lipid yield of the blends followed a predictable mass-balance trend, peaking at 18.70% for the 2TET:1PTE ratio. GC-MS-based FAME profiling showed that blending shifted the fatty acid distribution from strongly saturated (up to 94.54% SFA in Nostoc commune) toward a more balanced saturated/unsaturated composition, with the 2PTE:1TET blend reaching 30.59% monounsaturated fatty acids. Biodiesel quality indices estimated from the FAME profiles indicated that all blends met the kinematic viscosity (4.52–4.71 mm2/s) and density (0.873–0.880 kg/L) limits of EN 14214, with cetane numbers (55.59–57.63) matching both the EN 14214 and ASTM D6751 standards. The 2:1 PET:TET blend offered the best overall trade-off, combining a low cold filter plugging point (1.73 °C), a moderate iodine value (71.20 g I2/100 g), and a favorable cetane number (57.63). These findings support direct biomass co-blending of a high-lipid microalga with an abundant, low-cost macroalga as a scalable route for tuning biodiesel fuel-quality indices without additional extraction or refining steps, although the estimated properties reported here require experimental engine-bench validation before industrial application.
The presence of ciprofloxacin (CPX)—a commonly used antibacterial drug belonging to the quinolones—has been identified as one of the major emerging pollutants within our environment, it can persist in the ecosystems and contribute to the growing problem of antibiotic resistance. Therefore, this study evaluates spherical Al2O3 having either alpha or gamma phase and containing no dopant or copper nanometer-sized particles (CuNPs). This study aims to assess their ability to remove CPX from aqueous systems. Kinetic investigations demonstrated that CPX uptake is very sensible to initial adsorbate concentration, pH value and temperature of the system. Adsorption by γ-Al2O3-based materials was generally higher than by α-Al2O3 ones. Kinetic data were evaluated using pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich models. Fitted equations depend on the experimental conditions investigated. The effects of adsorption onto the alumina particles were also examined under distilled water and ionic water conditions. Furthermore, the adsorbed amounts at equilibrium were modeled using Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm models. It was determined that the phase of alumina was significant in determining the adsorption capacity. γ-Al2O3 had the largest adsorption capacity towards CPX. Its adsorption capacity in kinetic tests was found to be 5.6 mg/g in distilled water, while its capacity was greater (12.9 mg/g) when tested in ionic water (CPX = 25 mg/L). However, the addition of CuNPs into the alumina spheres reduced their overall capacity to adsorb CPX, as evidenced by decreased values for their respective adsorption isotherms. Furthermore, equilibrium data were fitted using four isotherm models and the best fitting model depended on both the nature of the adsorbent and the characteristics of the liquid phase. Overall, this study suggests that γ-Al2O3-based sorbent systems are highly capable and potentially useful for removing antibiotics from contaminated waters.
