The main feedstock for the synthetic process is ethene produced
by cracking ethane (obtained from natural gas) or naptha (from
crude oil). Synthetic ethanol is therefore a petrochemical product.
The supply of ethene in the UK is currently
plentiful; however as oil is a non-renewable resource, alternatives
will eventually have to be found.
Fermentation ethanol is produced from crop biomass, mainly sugar
cane, sugar beet, maize and corn. A considerable area of land is
needed to grow these crops, and plenty of sunshine is preferable.
Only part of the plant material is fermentable, but residues can
be used to make animal feeds and corn oil.
Biomass and Refuse
Newer methods that can make use of a greater proportion of plant
material are being developed. Agricultural waste, paper mill sludge,
forest residues and even domestic refuse can be used as feedstock.
If household waste is used, recyclable materials are first separated
and the remaining material is used to produce ethanol by conventional
fermentation. This combination of recycling and ethanol production
means that over 90% of the waste could be re-used in some way, reducing
considerably the need for landfill sites.
New biotechnology production of ethanol utilises waste biomass like
wood chip, corn stalks, rice hulls, and "bagasse" (sugar
cane residue) rather than crops grown specifically for the purpose
of ethanol production.