Green synthesis, based on green chemistry, is replacing the traditional methods, aiming to contribute with an enhanced environmental sustainability, which can be achieved using nontoxic compounds from biological resources, such as natural extracts from plants. In this study, the life cycle assessment (LCA) of iron oxide nanoparticles prepared through the green synthesis and the coprecipitation method is reported by following a cradle-to-gate approach. The LCA allowed quantifying and normalized the environmental impacts produced by the green synthesis (1.0 × 10^–9), which used a Cymbopogon citratus (C. citratus) extract and sodium carbonate (Na₂CO₃). The impacts were also determined for the coprecipitation method (1.4 × 10^–8) using the iron(II) salt precursor and sodium hydroxide (NaOH). The contribution of C. citratus extract and Na₂CO₃ as the precursor and pH-stabilizing agents, respectively, was compared regarding the iron(II) and NaOH compounds. Environmental sustainability was evaluated in human toxicity, ecosystem quality, and resource depletion. The major environmental contribution was found in the marine aquatic ecotoxicity (7.6 × 10^–10 and 1.22 × 10^–8 for green synthesis and the coprecipitation method) due to the highest values for ethanol (3.5 × 10^–10) and electricity (1.4 × 10^–8) usage since fossil fuels and wastewater are involved in their production. The C. citratus extract (2.5 × 10^–12) presented a better environmental performance, whereas Na₂CO₃ (4.3 × 10^–11) showed a slight increase contribution compared to NaOH (4.1 × 10^–11). This is related to their fabrication, involving toxic compounds, land occupation, and excessive water usage. In general, the total environmental impacts are lower for the green synthesis, suggesting the implementation of environmentally friendlier compounds based on natural sources for the production of nanomaterials.

Biorefining is sustainable biomass processing to obtain energy, biofuels and high value products through processes and equipment for biomass transformation. The biorefinery concept has been identified as the most promising way to create a biomass-based industry. Microalgae are classified as promising candidates in biorefinery processes because they are particularly important for obtaining multiple products. This review article describes the biorefinery concept taking into account its different interpretations and comparing it with the traditional biomass transformation processes. It describes the general characteristics of microalgae, and their potential to be used as a raw material in the biorefinery process. The review focuses on the state of the art of products obtained from microalgae for the biofuel industry, mainly for biodiesel production, and the different methods to extract oil for biodiesel production as well as other products. Based on this information, several aspects are suggested to be taken into account for the development of a topology for a microalgae-based biorefinery.

New ways and technologies for synthesizing adsorbent materials have been emerging based on the green chemistry concept for the sustainable use of available resources. In this sense, the chitosan-based products arise as a promising technology alternative for application of several fields that include mitigation, prevention, and control of environmental issues. Nevertheless, there is a lack of information about the development and behavior of these topologies at the industrial scale. This study addressed the techno-economic and sensitivity analyses as decision-making tools to assess promising topologies for production of chitosan-based bio-adsorbents. From the data provided by process inventory, economic analysis of these routes was implemented. The evaluation allowed obtaining a start point market price for chitosan microbeads (64.40 $/t) and chitosan microbeads modified with TiO₂ nanoparticles (37 $/t). The economic analysis also showed that there is a vast potential to explore the chitosan market that enables generation of very profitable businesses from the implementation of those processes, considering the obtained economic performance indicators for both topologies. It is crucial to highlight that these indicators were slightly higher for chitosan microbead production. In addition, the sensitivity analysis indicated that the chitosan-TiO₂ process could resist higher fluctuations in the operating costs, which might indicate that this topology might be a reliable alternative between evaluated cases.