Life Cycle Assessments Flashcards
What is the purpose of a life cycle assessment (LCA)?
It is used to assess the environmental impact of a product at different stages of its life
What are the four stages of an LCA?
- Extracting and processing raw materials.
- Manufacturing and packaging.
- Using the product.
- Disposing of the product.
What environmental impacts occur during raw material extraction?
Direct damage to the environment, such as deforestation or mining, and pollution from energy-intensive processes
What are three main issues during manufacturing and packaging?
- High energy use
- Pollutant release (e.g., carbon monoxide)
- Waste production
How does the use of a product affect its environmental impact?
It depends on how polluting the product is during use and how long it lasts
What are two main disposal methods and their impacts?
- Landfill: Takes up space and can pollute ecosystems
- Incineration: Releases pollutants into the air
Compare plastic bags and paper bags during raw material extraction
- Plastic bags: Made from crude oil (a finite resource).
- Paper bags: Made from wood (deforestation)
Compare plastic bags and paper bags during disposal
Plastic bags - Non-biodegradable, can harm wildlife
Paper bags - Biodegradable and non-toxic.
What are two major limitations of LCAs?
- They are complex and hard to quantify accurately
- They can be manipulated for positive advertising
What is potable water?
Water that is safe to drink
What are the three criteria for potable water?
- Low levels of dissolved substances.
- A pH between 6.5 and 8.5.
- No microorganisms like bacteria or fungi.
What are two types of fresh water sources?
- Surface water: Lakes, rivers, reservoirs
- Groundwater: Aquifers (permeable rock trapping water)
Why might surface water not always be reliable?
It can dry up in hot, sunny weather because it’s exposed to the sun
What are the three steps to treat fresh water?
- Wire mesh filtration: Removes large debris.
- Sand and gravel filtration: Removes smaller particles.
- Sterilization: Kills microorganisms using chlorine gas, ozone, or ultraviolet light
What is desalination, and when is it used?
- The extraction of potable water from sea water
- Used in areas with low rainfall
Describe the distillation process for desalinating seawater
Boiled to produce water vapor, which is then condensed into pure water
How does reverse osmosis desalinate seawater?
Salty water is passed through a semi-permeable membrane that only allows water molecules through, trapping larger molecules and ions
What are the limitations of desalination?
- Requires lots of energy.
- Is expensive.
- Impractical for producing large quantities of potable water
What is an aquifer?
A layer of permeable rock underground that traps fresh water
What are the three main sources of wastewater?
- Domestic: Household waste (e.g., showers, sinks, toilets).
- Agricultural: Nutrient runoff and animal waste.
- Industrial: Wastewater from factories containing harmful chemicals.
Why does wastewater need to be treated?
To remove organic matter, harmful microbes, and toxic chemicals to make it safe for disposal or reuse
What is the first step in sewage treatment?
- Screening: Large debris like twigs and plastic bottles are removed using a mesh
What happens during sedimentation in sewage treatment?
- Heavy solids sink to the bottom, forming sludge.
- The lighter liquid (effluent) remains at the top and is separated.
How is organic matter broken down in sewage treatment?
- Effluent: Broken down by aerobic digestion (oxygen is pumped in).
- Sludge: Broken down by anaerobic digestion (sealed tank with no oxygen)
What are the products of anaerobic digestion in sludge treatment?
- Methane: Used as an energy source.
- Digested waste: Used as a nutrient-rich fertilizer.
How is toxic wastewater treated?
- Adding chemicals to precipitate out metals.
- Using UV radiation to break down harmful substances.
Why is wastewater treatment preferred over seawater desalination?
- Easier
- Requires less energy
- Cheaper than desalination
What is effluent, and what happens to it after treatment?
- Is the lighter liquid from sedimentation.
- After aerobic digestion, it is safe to release into the environment
What is sludge, and how is it treated?
- The heavier solid waste from sedimentation.
- It undergoes anaerobic digestion, producing methane and fertilizer
Name two countries or regions where wastewater treatment is crucial for drinking water
- Singapore
- other areas with limited water supplies
