Good or bad ethanol – what determines this?
Författare
Summary, in English
The purpose of this study is to describe how the energy efficiency and greenhouse gas (GHG) benefits of ethanol depend on local conditions and calculation methods. The following four parameters have been identified as crucial to the GHG benefits of ethanol: (i) energy efficiency and emissions of nitrous oxide during cultivation, (ii) what kind of fuel is used in ethanol plants, (iii) how efficiently by-products are utilised and their benefits credited, and (iv) the type of land used for cultivation.
To ensure that “good” ethanol is produced (with reference to GHG benefits), the following demands must be met:
- ethanol plants should use biomass and not fossil fuels
- cultivation of annual feedstock crops should be avoided on land rich in carbon (above and below ground), such as peat soils used as permanent grassland
- by-products should be utilised efficiently in order to maximise their energy and GHG benefits (and these benefits should be credited by system expansion, followed by economic allocation and physical allocation)
- nitrous oxide emissions should be kept to a minimum by means of efficient fertilisation strategies, and the commercial nitrogen fertiliser utilised should be produced in plants which have nitrous oxide gas cleaning
Current production of Swedish ethanol from wheat can be seen as “good” ethanol, reducing GHG emissions by some 80 % compared to petrol. Ethanol based on sugarcane from Brazil leads to a reduction of – on average – 85 %, while ethanol from maize in the USA leads to a reduction of only 20 % on average. The reason for this is that several ethanol plants in the USA are using coal (fossil fuel). There is potential for improvement of current ethanol production systems worldwide, leading to increased GHG benefits. On the
other hand, increased competition for land in future may increase the risk of cultivation of annual ethanol
crops on new farmland rich in carbon. This will reduce the GHG benefits of ethanol from annual crops.
When such changes of land use are included in life cycle assessments of biofuels, complementary data should also be presented showing that this is the actual case regarding the specific biofuel production system analysed.
To ensure that “good” ethanol is produced (with reference to GHG benefits), the following demands must be met:
- ethanol plants should use biomass and not fossil fuels
- cultivation of annual feedstock crops should be avoided on land rich in carbon (above and below ground), such as peat soils used as permanent grassland
- by-products should be utilised efficiently in order to maximise their energy and GHG benefits (and these benefits should be credited by system expansion, followed by economic allocation and physical allocation)
- nitrous oxide emissions should be kept to a minimum by means of efficient fertilisation strategies, and the commercial nitrogen fertiliser utilised should be produced in plants which have nitrous oxide gas cleaning
Current production of Swedish ethanol from wheat can be seen as “good” ethanol, reducing GHG emissions by some 80 % compared to petrol. Ethanol based on sugarcane from Brazil leads to a reduction of – on average – 85 %, while ethanol from maize in the USA leads to a reduction of only 20 % on average. The reason for this is that several ethanol plants in the USA are using coal (fossil fuel). There is potential for improvement of current ethanol production systems worldwide, leading to increased GHG benefits. On the
other hand, increased competition for land in future may increase the risk of cultivation of annual ethanol
crops on new farmland rich in carbon. This will reduce the GHG benefits of ethanol from annual crops.
When such changes of land use are included in life cycle assessments of biofuels, complementary data should also be presented showing that this is the actual case regarding the specific biofuel production system analysed.
Avdelning/ar
Publiceringsår
2008
Språk
Engelska
Fulltext
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Dokumenttyp
Rapport
Förlag
Lund University, Environmental and Energy Systems Studies
Ämne
- Energy Systems
Nyckelord
- energy balance
- life cycle assessment
- Ethanol
- biofuels
- greenhouse gases
Status
Published
Report number
65 B
ISBN/ISSN/Övrigt
- ISSN: 1102-3651