- Created by: Benny52
- Created on: 04-12-18 18:46
Finite and Renewable Resources
- Natural resources form without human input - anything that comes from earth, sea or air - cotton, fuel. Some replaceable by synthetic products or improved on by man-made processes - rubber - natural product extracted from sap of tree, however man-made polymers made to replace rubber - used for tyres.
- Agri provides conditions where natural resources can be enhanced for our needs. Fertiliser development - can produce high yield of crops.
- Renewable resources reform at similar rate or faster than used - timber, fresh water, food.
- Finite resources not formed quick enough to be considered replaceable - fossil fuels, nuclear fuels (uranium, plutonium), minerals, metals found in ores. After extraction, finite resources undergo man-made processes to provide fuels & materials necessary - fractional distillation, metal ores reduced to form pure metal.
- Many modern materials made from raw finite resources - most plastics, metals & building materials. People have to balance social, economic & environmental effects of extracting. Mining metal ores - good - useful products made. Provides local jobs and brings £ into area. Bad for environment - scars landscape, produces lots of waste & destroys habitats.
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Reuse and Recycling
- Sustainable development - approach to development accounting for needs of present society and not damaging lives of future generations. Unsustainable to keep using finite resources. Extracting also unsustainable - amount of energy used & waste produced. Processing into useful materials unsustainable - uses energy from finite resources.
- Reduce use of finite resources - people use less. Things needed to make resource also reduced.
- Can't stop using finite resources altogether but chemists can develop & adapt processes that use less finite resources & reduce environmental damage - chemists developed catalysts - reduce amount of enegry needed for certain industrial processes.
- Copper - finite. Copper-rich ores in short supply. Improve sustainability by extracting from low-grade ores by:
- Bioleaching - bacteria used to convert copper compounds in ore to soluble copper compounds, separating copper from ore in process. The leachate (solution produced by process) contains copper ions - extracted by electrolysis or displacement with more reactive metal - scrap iron.
- Phytomining - plants grown in soil containing copper. Plants can't use or get rid of it so builds up in leaves. Plants harvested, dried and burned in furnace. Ash contains soluble copper compunds - copper extracted by electrolysis or displacement.
- Traditional methods of copper mining - damaging to environment. New methods have smaller impact but are slow.
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Reuse and Recycling 2
- Mining & extracting metals take lots of energy - most from burning fossil fuels.
- Recycling metals uses less energy, conserves finite amount of metals in earth & reduces waste sent to landfills. Usually recycled by melting then casting into shape of new product.
- Glass recycling - helps sustainability by reducing amount of energy needed to make new glass products & amount of waste created when used glass is thrown away.
- Glass bottles can be reused without reshaping.
- Other forms of glass can't be reused so are recycled. Glass separated by colour & chemical composition before recycled. Glass crushed & melted to be reshaped for use in glass products - bottles. Can be used for different use - insulatuing glass wool for wall insulation in homes.
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Life Cycle Assessments
- Looks at all stages of a product's life to assess its environmental impacts.
- Getting the Raw Materials: Extracting can damage local environment. Can also lead to pollution due to amount of energy needed. Raw materials - processed to extract desired materials and needs large amounts of energy.
- Manufacturing and Packaging: Both use lots of energy resources and can cause lots of pollution. Need to think about waste products and how to dispose of them. Chemical reactions used to make compounds from their raw materials can produce waste products. Some waste can be turned into other useful chemicals.
- Using the Product: Can damage environment. Burning fuels release greenhouse gases & other harmful substances. Fertilisers can leach into streams and rivers - damage to ecosystems. How long product is used for or no. of uses it gets is also factor - products that need lots of energy to produce but are used for ages mean less waste in long run.
- Product Disposal: Often disposed in landfills. Takes space and pollutes land & water. Energy used to transport waste to landfill - causes pollutants to be released into atmosphere. Products may be incinerated (burnt) - air pollution.
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Life Cycle Assessments 2
- Use of energy, some natural resources and amount of certain types of waste produced by product over its lifefime easily quantified. But effects of some pollutants is harder to give numerical value to. So producing LCA is not an objective method - takes into account values of person carrying out assessment - can be biased.
- Selective LCAs - only show some impacts so can be biased as they can be written to delibarately support claims of company to give them positive advertising.
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- Water that's been treated or is naturally safe for humans to drink. Chemists - potable water not pure (only contains H2O) - potable water can contain other dissolved substances. Important thing is level of dissolved salts aren't too high, it has pH between 6.5-8.5, and that there are no nasties like bacteria in it.
- Rainwater - type of fresh water - water that doesn't have much dissolved in it. When it rains, water can either collect as surface water (in lakes, rivers & reservoirs) or as groundwater (in aquifers - rocks that trap water underground). UK - source of fresh water used depends on location. Although it has low levels of dissolved substances, water from these fresh water sources need to be treated to make it safe. Process includes:
- Filtration - wire mesh screens out large twigs etc, & gravel & sand beds filter out other solid bits.
- Sterilisation - water sterilised to kill harmful bacterial & microbes. Done by bubbling chlorine gas through it or by using ozone or ultraviolet light.
- Some very dry countries - not enough surface or groundwater. Seawater treated by desalination to provide potable water. Distillation can be used to desalinate water.
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Potable Water 2
- Can test & purify sample of water in lab using distillation:
- First, test the pH of water using pH meter. If too high or low, you need to neutralise it. Do this by adding some acid or alkali until pH is 7.
- Set up equipment - beaker, condenser, Bunsen burner, thermometer, round bottomed flask, tripod, gauze.
- As water in flask heats, it'll evaporate and enter condenser as steam.
- Drop in temp. in condenser due to cold water around it wil cause steam to condense back into liquid water.
- Collect water running out of condenser in beaker.
- Retest pH of water to check it's neutral.
- Can tell whether there were salts in initial sample by looking to see if there are crystals in flask once water has been distilled.
- Seawater can also be treated by processes using membranes - reverse osmosis. Salty water passed through a membrane that only allows water molecules to pass through. Ions & larger molecules are trapped by membrane so separate from water.
- Distillation & reverse osmosis needs lots of energy - really expensive & not practical for producing large quantities of fresh water.
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Waste Water Treatment
- Water used for many things at home - bath, toilet, washing-up, etc. When water flushed down drain, it goes into sewers towards sewage treatment plants.
- Agricultural systems produce lots of waste water - nutrient run-off from fields & slurry from animal farms. Sewage from domestic or agricultural sources has to be treated to remove organic matter & harmful microbes before putting back into freshwater sources. Otherwise would make them polluted and would pose health risks. Industrial processes produce lots of waste water that has to be collected & treated. Industrial waste water can also contain harmful chemicals - has to undergo additional stages of treatment before safe to release.
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Waste Water Treatment 2
- Processes involved in treating waste water includes:
- Screening - involves removing large bits of material and grit.
- Sedimentation - sewage allowed to stand in settlement tank and heavier suspended solids sink to bottom - sludge - and lighter effluent floats on the top.
- Biological Aerobic Digestion - effluent removed and treated by this. Air is pumped through water to encourage aerobic bacteria to break down organic matter including other microbes in water. Its released back into environment
- Anaerobic Digestion - sludge temoved and transferred into large tanks. Broken down by bacteria by this process. Organic matter broken down in sludge releasing MH4 in process can be used as energy source and remaining digested waste - fertiliser
- For waste water containing toxic substances, additional stages of treatment may involve adding chemicals (e.g to precipitate metals), UV radiation or using membranes.
- Sewage treatment requires more processes than treating fresh water but uses less energy than desalination. However, people don't like idea of drinking water that was once sewage.
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