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Politecnico di Milano ingegneria per l'ambiente e il territorio - environmental and land planning engineering 2021
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This document explores key concepts in green and sustainable chemistry, covering GMOs, renewable energies (biomass, solar, hydrogen), and sustainable production methods. It details benefits of reducing sulfur in fuels, enzymatic catalysis for pharmaceuticals, and efficient microwave chemistry. Discussions also include bioplastics, biorefineries, and the advantages of heterogeneous catalysis and supercritical CO2 extraction. The text emphasizes minimizing waste, improving atom economy, and utilizing renewable resources as core principles for environmental engineering and sustainable chemical practices.
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- Genetically Modified Organisms (GMOs): Involve modifying genetic makeup by inserting new DNA (not RNA) into organisms, driven by genetic engineering to achieve specific traits and produce proteins.
- Renewable Resources: Defined by rapid natural regeneration, they include biomass, hydropower, geothermal, wind, and solar. These sources offer cleaner energy with less pollution, though they can have reliability challenges compared to non-renewables.
- Sulfur in Fuels: Its reduction is crucial to prevent acid rain, corrosion, and toxicity. Methods include using biofuels, flue gas desulfurization with limestone or NaOH, pre-combustion with hydrogen, and basic additives during combustion.
- Hydrogen Energy: Presents advantages as a renewable, clean, non-toxic, and efficient energy source, but faces hurdles such as high cost, storage complexities, safety concerns, and current reliance on fossil fuels for its production.
- Supercritical Fluids: Substances above critical temperature and pressure, offering tunable properties and advantages like increased mass transport. Supercritical CO2 is preferred for extracting apolar organic products (like fragrances) over polar supercritical water due to polarity matching and lower operational requirements.
- Enzymatic Catalysis: Essential for synthesizing pharmacologically active molecules due to enzyme specificity, enabling greener processes with less waste, selective reactions, and kinetic resolution (e.g., in penicillin synthesis).
- Bioplastics: Materials that are biobased, biodegradable, or both. Starch-based bioplastics are compostable and degrade into CO2 and water. Bio-PE, derived from biomass, can be blended with starch to combine biodegradability with mechanical strength.
- Sustainable Production of Chemicals: Bio-butanol can be produced from diverse bio-feedstocks via fermentation of glycerol (from oil plants), lignocellulose (via hydrolysis), sugary biomass, or catalytic conversion of syngas.
- Lignocellulosic Materials: Serve as a source for 'Second Generation Biofuels,' which come from low-value biomass (e.g., wood, agricultural waste), reducing competition with food crops and offering higher yields with less waste and land use.
- Heterogeneous vs. Homogeneous Catalysis: Heterogeneous catalysis is preferred from a green chemistry perspective due to easier catalyst separation, reuse, and significantly less waste generation compared to homogeneous systems.
- Green Chemistry Principles: Focus on maximizing reaction efficiency, minimizing waste, avoiding hazardous solvents (or using environmentally friendly ones), employing catalysts, and using renewable resources to reduce environmental impact. Renewable natural molecules are not inherently green if their production is unsustainable.
- Biodiesel Benefits: Offers cleaner combustion with lower particulate and sulfur emissions compared to petroleum diesel. It's considered a renewable resource with a more stable price, although its production processes can sometimes involve fossil fuels.
- Microwave Chemistry: An advantageous technology for green chemistry due to direct energy transfer to molecules, leading to efficient, faster reactions with reduced solvent use, lower energy consumption, and less waste.
- Biorefineries: Utilize biomass to produce materials, fuels, and energy, valorizing liquid and solid waste. In paper manufacturing, a major biorefinery application, processing wastes are used to generate energy, significantly reducing the facility's energy demand.
- Building Blocks: There's a shift towards using C-building blocks (e.g., C6 hexoses like glucaric acid, FDCA, sorbitol) derived from natural resources (starch, hemicellulose, cellulose) through biorefineries, moving away from petrochemical sources.
- Adipic Acid Production: Traditional methods generate significant waste, including N2O (a potent greenhouse gas), making it an environmental concern. Greener alternatives, while potentially less efficient in yield, aim to reduce hazardous co-products.
- Waste Reduction Strategies: The international community emphasizes green chemistry principles to maximize efficiency, minimize waste, and promote renewable resources, recycling, and sustainable practices across energy, chemical, and agricultural sectors.
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This course covers a significant emerging field in modern chemistry, which focuses upon the reinvention of chemistry to reduce impact on human health and environment of industrial products and processes. Examples of successful green chemistry developments will be highlighted. Themes woven throughout the course…