"A raw material of feedstock should be renewable rather depleting wherever technically and economically practicable" (Green Chemistry Principles, Dr. Paul Anastas et al)

"[We should]…eliminate our contribution to systematic increases in concentrations of substances from the Earth's crust. This means substituting certain minerals that are scarce in nature with others that are more abundant, using all mined materials efficiently, and systematically reducing dependence on fossil fuels."  (The Natural Step, Promoters of Sustainable Development)

Every living organism must take material from the surrounding environment in order to survive. In some cases considerable changes in the environment may take place as a result, but these are normally part of renewable cycles.

Continued extraction of minerals, oil and gas from the Earth's crust, however, will result in steady depletion, as these resources are finite. In addition, "new" material is continually being added to the biosphere, affecting the on-going cycles. This is part of the problem the chemical industry is faced with.

Fossil Resources

Much of the chemical industry uses a relatively limited range of raw materials. The fossil fuels, coal oil and natural gas, are used to make fuels, but also form the basis for the manufacture of many bulk chemicals. An enormous number of common products are therefore ultimately petrochemical in origin.

Some common bulk chemicals manufactured from oil and gas:

Ammonia Benzene
Phenol Sulphuric Acid
Nitric acid Ethanoic Acid

Fossil reserves will continue to be important resources for many years to come, but much research and development has focussed on more efficient use, and recycling of the end products. The recycling of nylon is a good example of this.

Renewable Resources

If a resource is renewable, it will be replenished over a relatively short timescale. Plants have the potential to be more or less infinitely renewable as feedstock. Plant material, when used in this context, is usually referred to as biomass.
Chemicals, including many pharmaceuticals, have been made successfully from plant extracts for many years.

Ethanol, primarily a petrochemical product in the UK, is produced by fermentation link to ethanol production at production methods summary, p4 in most of the rest of the world.

Starch and Cellulose are important renewable resources for chemical production. Click here to find out more about these.

A general-purpose oil ("Bio Oil") from fast pyrolysis, already in use as a substitute for fuel oils, could become the basis for a future bio-refinery, similar to current petrochemical refineries in function. For more details on bio oil, click here

Glucose, the main building block of starch, is relatively easy to obtain from plant material, and can be used to synthesise a wide range of existing chemicals.

Thinking Plants

There are problems, however, with relying on plants to produce chemicals:

  • Apart from cellulose, plants themselves rarely contain individual chemicals in large amounts, so a lot of plant material is needed for simple extraction, with a consequent high volume of waste. This may be acceptable with products only needed in small quantities (eg specialised medicines), but not for high volume manufacture. This underlines the importance of synthetic routes from cellulose and glucose, materials present in substantial amounts.
  • Plants usually contain many complex materials, whereas the chemical industry works best with a more limited range of simpler substances.
  • Setting aside land for dedicated feedstock crops is not always desirable. In many cases the local population may gain little benefit, and valuable agricultural land may be used. Chemical manufacture from agricultural waste, where feasible, is a better alternative. Phenolic resins can be made using timber waste.
  • Traditional methods of production from biomass can be inefficient, as they cannot utilise enough all of the feedstock. Higher chemical yields may require genetically modified bacteria, as in the case of new methods for ethanol production.

diagram: fossil fuels add material to the biomass

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