Chapter 1
Introduction
JAMES H. CLARK
Chemistry—Past, Present and Future
The Costs of Waste
The Greening of Chemistry
Sustainable development,
Cleaner production,
Atom economy,
E factor,
Principles of Green Chemistry,
Life-cycle assessment
Chemistry—Past, Present and Future
Chemical products make an invaluable contribution to the quality of
our lives and play a fundamental role in almost every aspect of
modern society.
• Pharmaceuticals products
In twentieth century, World population: from to 6 billion, Life
expectancy: almost 60%↑
• Crop protection and growth enhancement chemicals
• The enormous populations demand western levels
• The public image of the chemical industry has badly deteriorated in
the last ten years . . .
• In some of the major centres of chemicals manufacturing more
people gave positive than negative views, but for many European
countries the ratio of unfavourable to favourable views was
alarmingly high.
Chemistry—Past, Present and Future
Figure Trends in the favourability to the chemical industry of the
general public (smoothed plots) (based on MORI Opinion Poll figures in
the period 1980–2000).
In the UK, a steady decline in public perception of the chemicals
industries over many years is clearly evident. It is especially
disturbing to analyse the survey data more closely and to note that
the 16–24 year age group has the lowest opinion of the chemicals
industries.
Chemistry—Past, Present and Future
Figure Trend in the number of applications to study chemistry in UK universities
(source: UCAS Universities and Colleges Admissions Services ).
At present, the poor image of chemistry is adversely affecting
demand. In the UK, the number of applicants to read chemistry at
university has been falling steadily for several years
The number of applicants to read chemical engineering is even more
alarming (<1000 in the year 2000 in the UK)
View of twentieth century chemical manufacturing
• (1) Start with a petroleum-based feedstock.
• (2) Dissolve it in a solvent.
• (3) Add a reagent.
• (4) React to form an intermediate chemical.
• (5) Repeat (2)–(4) several times until the final product is obtained;
discard all waste and spent reagent; recycle solvent where
economically viable.
• (6) Transport the product worldwide, often for long-term storage.
• (7) Release the product into the ecosystem without proper
evaluation of its long-term effects.
The recipe for the twenty-first century
• (1) Design the molecule to have minimal impact on the
environment (short residence time, biodegradable).
• (2) Manufacture from a renewable feedstock (. carbohydrate).
• (3) Use a long-life catalyst.
• (4) Use no solvent or a totally recyclable benign solvent.
• (5) Use the smallest possible number of steps in the synthesis.
• (6) Manufacture the product as required and as close as possible
to where it is required.
• We must train the new generation of chemists to think of the
environmental, social and economic factors in chemicals
manufacturing.
The Costs of Waste
• In the mid-1990s in the USA, for example, only about
300 or so of the 75000 commercial substances in use
were classified as hazardous.
• Compliance with existing environmental laws will cost
new EU member states well over €10 billion; a similar
amount is spent each year in the USA to treat and
dispose of waste.
• Cost of waste can easily amount to 40% of the overall
production costs for a typical speciality chemical product.
Production costs
Figure Production costs for speciality chemicals.
The Costs of Waste
Figure The costs of waste.
The Greening of Chemistry
Figure Options for waste management within a chemical manufacturing process.
Hierarchy of waste management techniques
• Prevention, by far the most desirable option
• Recycling, the next most favourable option
• Disposal, the least desirable option
• Cleaner production:
‘The continuous application of an integrated preventative
environmental strategy to processes and products to reduce
risks to humans and the environment. For production
processes, cleaner production includes conserving raw
materials, and reducing the quality and toxicity of all emissions
and wastes before they leave a process.’
Atom economy
Table ‘Atom accounts’ for a typical partial oxidation reaction using chromate
Element Fate Atom utilisation
C Product(s) Up to 100%
H Product(s) + waste acid <100%
Cr Chromium waste 0%
Na Salt waste 0%
S Salt waste (after acid neutralisation) 0%
O Product(s) + waste <<100%
Atom economy: how many atoms of the starting material are
converted to useful products and how many to waste.
A typical oxidation reaction: an alcohol → a carboxylic acid
chromium (VI) as the stoichiometric oxidant
Environmental factor
It is used to quantify the effects of production process to the
environment
Idea: All other compounds formed other than the target product
are considered to be WASTE.
Atom Economy and environmental effects
Where does the waste come from?
EnvironmentalEnvironmental
factor factor
E=
The amount of waste
The amount of
target product
The more waste formed
The more serious the
pollution
If the atom
Utilization=100%
E=0
Environmental factor
Environmental factor
Table Relative efficiencies of different chemicals manufacturing sectors
• Areas traditionally thought of as being dirty (oil refining & bulk chemical
production) are relatively clean - they need to be since margins per Kg are low.
• Newer industries with higher profit margins and employing more complex
chemistry produce much more waste relatively.
Industry sector Product tonnage By-product weight / product weight
Oil Refining 106 - 108 <
Bulk Chemicals 104 - 106 1 - 5
Fine Chemicals 102 - 104 5 – 50+
Pharmaceuticals 10 - 103 25 - 100+
Environmental quotient (EQ)
E-----Environmental factor
Q-----The extent of hazardousness of the waste to the environment
obtained from the performance of the waste in the environment.
EQ＝E×Q
The E factor just gives the ratio of the waste and the target
product.
But the environmental pollution is strongly associated with
the harmful performance of the waste.
Energy Efficiency
Table Global ‘lost work’ in major chemical processes
Process
Theoretical work potential (kJ·mol-1 final product)
Raw
materials
Final
producta
Thermodynamic
efficiency (%)
Natural gas + air → methanol 1136 717 63
Natural gas + air → hydrogen 409 236 58
Ammonia (from natural gas + air)
→ nitric acid
995 43 4
Copper ore → copper 1537 130 9
Bauxite →aluminium 4703 888 19
a Excludes any ‘steam credit’.
Energy efficiency via ‘lost work’
Biomass utilisation
Figure Biomass utilisation in 2040.
Biomass utilisation
Table From fossil to green
Energy source
Percentage of energy sources
1990a 2040b
Oil 38 17
Coal 20 18
Gas 16 14
Biomass 16 19
Hydro 5 5
Nuclear 5 6
Solar — 14
Wind — 7
Based on an energy consumption of a ×1020J; b 1×1021J.
We seek to satisfy our need and not our greed
life-cycle assessment
The life-cycle of a product can be considered as:
Pre-manufacturing (materials acquisition)
↓
Manufacturing (processing and formulation)
↓
Product delivery (packaging and distribution)
↓
Product use
↓
End of (first) life
We can no longer afford single-use products.
life-cycle assessment
Figure Life-cycle assessment for chemical products (E = energy
input; C = consumables input; W = waste).
Pollution prevention options
Figure Pollution prevention options in the life-cycle of a chemical product.
Pollution prevention options
Pollution prevention options can be considered at every stage in
the life-cycle of a chemical product .
• Adopt a life-cycle perspective regarding chemical products
and processes
• Realise that the activities of your suppliers and customers
determine, in part, the greenness of your product
• For non-dissipative products, consider recyclability
• For dissipative products (. pharmaceuticals, crop-
protection chemicals), consider the environmental impact of
product delivery
• Perform green process design as well as green product
design
