Feedstock

Synthetic Route
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.

      
Conventional Fermentation Route
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.
photo: corn harvested for ethanol production
Waste 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.
photo: bagasse from sugar cane


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