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ENVIROMENT AND ENERGY

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They are organic salts that have meltingpoints below 100C.

They are liquid at R.T.P.

They can dissolve a wide variety of inorganicand organic compounds.

Also, they have no vapour pressure and canbe re-used.

IONIC LIQUIDS

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Chromium plating is a highly hazardousprocess that makes use of chromic acid, ahighly toxic and cancer forming compound.

An ionic liquid produced from chromium(III)

chloride and choline chloride (vitamin B4) wasused to reduce its danger.

It has been shown to reduce the risks tochromium plating personnel as well as

increasing the overall currentefficiency of the

proces from 15%

with chromic acid

IONIC LIQUIDS:EXAMPLE

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Copper mining produced huge pilesof waste that still contained copper.Recently bacteria began to be usedto extract this remaining copper.

The process is termed bacterialleaching.

The bacteria create an acidicsolution, dissolving the copper from

what was waste ore. The copper isdisplaced by adding scrap iron.

The bacteria actually use Fe2+ andS2- ions in their metabolic

processes, not the copper. They

ROCK-MUNCHINGBACTERIA

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Gold is traditionally extracted from ore mixedwith oxide or sulphide ores of other metalsusing cyanide. However, the cyanide onlyextracts 10% of the gold and is very toxic to

all life.

Using bacterial leaching can raise thepercentage of gold extracted to 85- 100%.

However, Thiobacillus thio-oxidans prefers atemperature of about 30oC for optimumperformance, much lower than the regionwhere the gold mining takes place.

Thiobacillus thio-oxidans uses its unusual

ROCK-MUNCHING BACTERIA

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Biofuels are other alternatives to oil-basedfuels that can be produced from biomass.

Biofuels can be:

Biodiesel

Bioethanol

Biodiesel refers to fuels that can be used inplace of diesel and that are usually made fromvegetable oils or animal fats.

Other use of biomass:

BIOFUELS:DIESEL AND

ETHANOLFUELS

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Bioethanol is used as a potentialalternative to oil-based fuels thatmakes use of local resources andis less polluting.

Plants are being constructed toproduce ethanol, to be blendedwith petrol in proportions ranging

from 10% to 85%.Sources of ethanol:

sugar cane

sugar in maize

BIOFUELS:DIESEL ANDETHANOLFUELS

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A fuel cell is an electrochemical device similarto a battery.

A fuel cell is designed to use a continuousexternal supply of reactants.

A typical fuel cell is a hydrogen cell and thereactants are hydrogen and oxygen.

They are emission-free.

This technology has been recently used toprovide fuel for vehicles.

BATTERIES AND FUEL CELLS

VIDEO

http://www.youtube.com/watch?v=WZ0wJPi5aGshttp://www.youtube.com/watch?v=WZ0wJPi5aGs

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Audi A2

Audi A2 hasbeen built

that runs onhydrogen,achieving94 mpg, but

with alimitedrange.

Although,

the same

They aim tocut their CO2

emissions fromtheir vehiclesin half by useof hydrogen

poweredvehicles.

They tookdelivery of

their first

BATTERIES AND FUEL CELLS

Norwegian roadconstruction giant

Mesta

It has an electric

motor that is driven by

a bank of nickel metalhydride batteries that

recharge when the car

is coasting down hill

and switches to petrol

when acceleration is

required.

Toyota Priushybrid

petrol/electric car

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Hydrogen gas must be compressed in orderfor it to be stored at a small enough volumeon a vehicle. But this is an explosive process.

For an alternative approach, the followingshould be present:

A solid material to absorb the hydrogen

This way the hydrogen is bonded to the material

and is released by a chemical reaction whenneeded. The material itself can be recycled.

The elements of the storage material should beof the first two rows of the Periodic Table

So that the storage material doesnt make the fuel

OVERCOMING THEHYDROGEN STORAGE

PROBLEM

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Sodium aluminium hydride, NaAlH4, a solidknown to reversibly absorb hydrogenmolecules, is being investigated.

High temperatures are needed and this

hydride (and related hydrides) can only storeabout 5% by weight of hydrogen.

Doping this compound with titanium makesthe absorption and release of hydrogen muchmore efficient.

This is because the titanium acts as a catalyst,forming a compound called titanium aluminide

on the surface of the NaAlH4

HYDROGEN STORAGE

PROBLEM

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Sources of hydrogen:

Electrolysis of water,

but electricity is required for this process, and inmost countries that electricity still comes primarilyfrom power stations that burn fossil fuels.

The electrolysis of water usually requires 50% more

energy that is stored in the hydrogen produced.

from methane in natural gas,

but this process uses up natural resources andgenerates greenhouse gases.

This is why the fuel cell cannot be completely

SOURCING HYDROGEN

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Nuclear fuel can be viewed as a clean source of energy with zero emissionsof greenhouse gases.

In contrast, coal or gas fired power stations may release carbon dioxide,sulphur dioxide and oxides of nitrogen. Only sulphur dioxide is beingremoved at present. Biomass has the same problem, it burns to releaseCO2

Current use of fossil fuels amounts to 20 million fossil fuel years per year.A teraWatt hour of electricity produces about 20 tonnes of nuclear wastecompared to around 20 million tonnes of CO2 from fossil fuels.

Nuclear power stations generate radioactive waste products and we mustbe sure that these can be stored safely well beyond our lifetimes. These can

be contained most easily as solid waste and stored underground. There is concern that an accident at or a terrorist attack on a nuclear plant

would have much more devastating and long-term consequences than anaccident at or attack on a gas or oilfired power station or pipeline. UnlikeChernobyl, modern nuclear power plants are designed to be fail-safe butopponents of nuclear power argue that the risks are still too great.

Nuclear power is a cheap source of energy, but the cost of cleaning up andsecuring nuclear waste is prohibitive

NUCLEAR POWER,