Topic 10: Earth's Resources

What are natural resources

Natural resources form without human input. They include anything that comes from the earth, sea or air. We use them to provide energy for things like warmth, shelter, food and transport

Examples of natural products that are supplemented or replaced by agricultural and synthetic products

• Rubber is extracted from the sap of a tree, however man-made polymers have now been made which can replace rubber in uses such as tyres

• Wood has been replaced by plastics in many applications. For example laminate flooring is composed of a polymer resin and a man-made wood composite. Window frames are now mainly made from a polymer

• Cork is produced from the bark of a tree and can be used as a wine stopper. Synthetic corks, made of plastics, are now used in place of natural cork to prevent tainting of the wine by a chemical found in the bark

What does agriculture provide

Conditions where natural resources can be enhanced for our needs. For example, the development of fertilisers has meant we can produce a high yield of crops

Distinguish between finite and renewable resources

Renewable Resources:

• can be reformed at a similar rate to, or faster than, we use them

Examples:

• timber is a renewable resource, as trees can be planted following a harvest and only take a few years to regrow. Other examples include vegetable crops and sustainably caught fish

Finite (non-renewable) resources:

• can’t be formed quickly enough to be considered replaceable

• after they’ve been extracted, many finite resources undergo man-made processes to provide fuels and materials necessary for modern life

Examples:

• Include fossil fuels and nuclear fuels such as uranium and plutonium

• Minerals and metals found in ores in the earth are also non-renewable materials

What is sustainable development

development that meets the needs of current generations without compromising the ability of future generations to meet their own needs.

What is potable water

water that’s been treated or is naturally safe for humans to drink - it’s essential for life

Why is potable water not pure

Potable water is not pure water in the chemical sense because pure water only contains H₂O molecules whereas potable water can contain lots of other dissolved substances

What is fresh water

• Fresh water is water that doesn’t have much dissolved in it. For example:

In the United Kingdom, rain provides water with low levels of dissolved substances (freshwater) that can be collected as surface water (lakes, rivers, and reservoirs) or as groundwater (in rocks called aquifers that trap water underground)

What do the methods used to produce potable water depend on

The source of fresh water chosen depends on location. Surface water tends to dry up first, so in warm areas most of the domestic water supply comes from groundwater.

Steps to treat fresh water

1. Filtration - a wire mesh screens out large twigs etc, and then gravel and sand beds filter out any solid bits

2. Sterilisation - the water is sterilised to kill any harmful bacteria or microbes. This can be done by bubbling chlorine gas through it or by using ozone or ultraviolet

What is the definition of:

• Residue

• Filtrate

Residue - an insoluble solid that remains on the filter paper

Filtrate - the solution/water that has been filtered

What happens if supplies of fresh water are limited

If supplies of fresh water are limited, seawater must be treated by desalination to provide potable water. Desalination of seawater can be done by distillation or by processes that use membranes such as reverse osmosis.

These processes require large amounts of energy, so they're really expensive and not used if there are other sources available

What happens during reverse osmosis

Salty water is passed through a membrane that only allows water molecules to pass through. Ions and larger molecules are trapped by the membrane and so separated from the water

Sources of waste water

Urban lifestyles and industrial processes produce large amounts of wastewater that require treatment before being released into the environment

• Sewage and agricultural wastewater require removal of organic matter and harmful microbes

• Industrial wastewater also requires removal of organic matter and harmful chemicals

Stages of wastewater treatment

Screening -

• Before being treated, the sewage is screened - this involves removing any large bits of material (like twigs or plastic bags) as well as any grit

Sedimentation -

• The screened waste is allowed to stand in a settlement tank and undergoes sedimentation - the heavier suspended solids sink to the bottom to produce sludge, while the less dense effluent floats on the top

Aerobic digestion -

• The effluent in the settlement tank is removed and treated by biological aerobic digestion. This is when air is pumped through the water to encourage aerobic bacteria to break down any organic matter - including other microbes in the water

Anaerobic digestion -

• The sludge from the bottom of the settlement tank is also removed and transferred into large tanks. Here, it gets broken down by bacteria in a process called anaerobic digestion. Anaerobic digestion breaks down the organic matter in the sludge, releasing methane gas in the process. The methane gas can be used as an energy source, and the remaining digested waste can be used as a fertiliser

Advantage and disadvantage of producing potable water from wastewater compared to fresh water and sea water

Advantage - uses less energy than desalination

Disadvantage - requires more processing than treating fresh water so costs more or public may be against drinking recycled water

Is the supply or copper-rich ores limited or unlimited

limited and the demand for copper is growing!

What is the new way of extracting copper

low grade ores - ores that only contain small amounts of copper

What are the two methods used to extract copper from low grade ores

1. Bioleaching

• Uses bacteria which convert copper compounds in the ore into soluble copper compounds, separating out the copper from the ore in the process

2. Phytomining

• The plant absorbing copper through the roots

• The plant being harvested, dried and burned

• The metal compound being collected from the ash

• The metal being obtained from its compound by displacement or electrolysis

Advantages and disadvantages of Bioleaching and phytomining

Advantages:

• Conserves high-grade ores

• Avoids the large amount of digging, moving, and disposing of rock involved in traditional mining

• Conserves energy

• Less pollution

Disadvantages:

• The process is slow

• Sometimes electrolysis is used to purify the extracted metal which uses energy

Name the two methods used to extract copper from the copper compound obtained from phytomining or bioleaching

• Displacement using scrap iron

• Electrolysis

Why are life cycle assessments carried out?

to assess the environmental impact of a product

Name the four main stages of a life cycle assessment.

• Getting the raw materials

• Manufacturing and packaging

• Using the product

• Product disposal

Is it fairly easy to quantify the use of water, resources, energy sources and production of some waste.

yes

It is easy to allocate a numerical value to the polluting effect of a product when carrying out a LCA.

no

Is a life cycle assessment an objective process

no

compare LCAs for shopping bags made from plastic and paper

Plastic Bag:

• Raw materials - crude oil

• Manufacturing and packaging - the compounds needed to make the plastic are extracted from crude oil by fractional distillation, followed by cracking and then polymerisation. Waste is reduced as the other fractions of crude oil have other uses

• Using the product - can be reused. Can be used for other things as well as shopping, eg bin liners

• Product disposal - recyclable but not biodegradable and will take up space in landfill and pollute land

Paper Bag:

• Raw materials - timber

• Manufacturing and packaging - pulped timber is processed using lots of energy. Lots of waste is made

• Using the product - usually only used once

• Product disposal - biodegradable, non-toxic and can be recycled

Conclusion of comparing plastic bag and paper bag

Life cycle assessments have shown even though plastic bags aren’t biodegradable, they take less energy to make and have a longer lifespan than paper bags, so they may be less harmful to the environment