Notes on chapters 20, 21, 22 PDF

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Cement, plastic, paper...

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Lecture Note 20 A. Admin 1. Reading quiz due Sunday 1159 pm 2. Final exam questions due April 28th 3. Muddiest points for chapter 17 due today B. Ch 20 – Cement • What is cement, mortar and concrete • Who uses it • How is it made • Energy and emissions  Process efficiency effects  Material efficiency effects 1. Cement vs. Concrete • Cement – the binder, akin to flour  Limestone (CaCO3) + heat = lime (CaO) + CO2  Lime + water + sand = cement - CO2  Lime + silica + alumina + water = Portland cement • Concrete – a composite, akin to a cookie:  Aggregate (gravel) – ~ 75% of mass  Cement  Water • Mortar – akin to frosting  Like concrete but with lime & sand as aggregate  Softer 2. How are cement and concrete made

Source of most energy use and emissions is production 3. Uses and demand

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Almost all concrete is reinforced with steel bars  Largest single use of steel Demand now and in the future

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75% increase by 2050

4. Little intl trade in cement • Raw materials easily available everywhere • Low value for materials • “Make your own”

5. Energy and emissions • Min theoretical = 1.8 GJ/tonne • BAT = 2.9 GJ/tonne • Global avg = 5 GJ/tonne • Production to increase by 75% by 2050 • Can use waste as fuel • Substitute other materials for cement  10-20% done now 6. Recycling vs. Downcycling • True recycling would require > 1 GJ/tonne • Instead, crush it and use as aggregate  Lower performance  More variable  Cheaper  Better than landfill • May be a place for CCS 7. Outlook for Process Improvements alone • Demand to increase 75% by 2050 • All things considered, best case scenario is an 18% INCREASE in emissions by implementing process improvements alone 8. Other option: Less cement, same service = “material efficiency” • Use less cement when making concrete  In low performance applications

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Designing structures that require less concrete  Equivalent of tesselation Substituting other materials Delaying the end of life of concrete structures Re-using concrete components

C. Ch 21 – Plastic • What are plastics • Who uses it • How is it made • Energy and emissions  Process efficiency effects  Material efficiency effects 1. What are plastics • Polymers – “many mers” • Mer – the repeating unit • Most polymers consist of intertangled, interconnected long chains of carbon 2. Types of plastics • ThermosetsNOT recyclable • Thermoplasticsrecyclable 3. How are thermoplastics made Start with oil Energy required ~ 80 MJ/kg = 80 GJ/tonne Emissions ~ 2-3 kg CO2/kg 4. Bioplastics • Can make from some plants as the basic building blocks are similar to oil • Biodegradable (some) • Land use • Debate concerning energy savings and net effects on GHG  Release of Nitrous Oxide from corn growing • >300x worse than CO2 5. Over 50,000 different polymers • Chosen for combination of properties  Strength, resistance, stiffness, etc. • Chemistry determines properties • Processing determines geometry 6. Uses of and demand for plastics

7. Process efficiency? • Energy efficiency in production  15% possible • Downstream options akin to metals • Recycling options  Best during production • Already happens

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Improve separation from other waste Improved sorting

8. Recycling Once it hits the general population • Types of recycling  Primary (at production)  Secondary • Grind, clean, convert back to resin • Lower quality  Tertiary • Pyrolysis to produce new feedstocks  Quarternary • Burn 9. Material Efficiency? • Less material by design • Reduce yield losses • Divert scrap • Reuse • Longer life 10. Summary Reducing variety of plastics would help, but is hard to see happening Use as fuel Reuse plastic packaging or replace Life extension of products with plastics as major component C. Ch 22 - Paper • A closer look at paper • Who uses it • How is it made • Energy and emissions  Process efficiency effects  Material efficiency effects 1. Paper up close plant fibers wire screen 2. Use and demand

3. Making paper

4. Mixing in recycled paper

5. Recycling • 40% of all waste stream is paper  72 Mt per yr in US • 35% of harvested trees are to make paper

 16B paper coffee cups in ‘06 in US

6. Energy flow

Emissions ~ 1 tonne CO2/tonne paper 7. Process efficiencies efficiencies increasing

cost May get to 40% reduction per tonne

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8. Material efficiencies Using lighter paper Printing on demand Removing print to allow paper re-use Substituting e-readers for paper.

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9. Summary Processes are efficient already Recycling is good, can get a bit better Demand will double before 2050 Cannot get to 50% emissions decline Need to become more material efficient or use demand reduction...