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Agroenergy: environmental reasons and agronomic aspects

Uffe Jørgensen, Dep. of Agroecology and Environment, Aarhus University

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Today biomass is the worlds largest source of renewable energy

Wind and solar can’t do the job alone - We must and can utilise much more biomass to move

from a fossil to a renewable

based society

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International analyses show significant

potential for increased

bioenergy production

Dornburg et al., 2008

Today

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However, exploiting the bioenergy potential is not easy - interaction with food production, nature conservation etc

Dornburg et al., 2008

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Sustainability is a must!

 Land is limited

 Use residues

 Increase yields

 GHG balance must be highly positive

 Don’t clear virgin land

 Grow crops that build up soil carbon

 Analyse GHG on whole bioenergy chain

 Multiple ecosystem services

 Reduction of nutrient losses

 Reduction of pesticide use

 Biodiversity

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Perennial energy crops have better environmental profile than annual crops

70% lower nitrate leaching 60% lower pesticide use

60% higher GHG emission reduction

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Projected environmentally compatible energy crops in EU

EEA, 2008

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Free range pigs in miscanthus and willow to optimise land use, reduce nitrate

leaching and improve animal welfare

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How is the ideal energy crop?

 Perennial – high sustainability

 High biomass yield

 Long canopy duration

 C ₄ photosynthesis

 Resistant to pests and diseases

 High water use efficiency

 Sterile – non-invasive

 Max. 2 m high

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The ideal energy crop II

 Easy to harvest, transport and store

 Easy to convert into energy

 Biological conversion (ethanol, biogas etc.)

 Low lignin content

 Endoxylanase in cell walls

 Moist biomass

 Thermochemical conversion (CHP, BtL)

 Dry biomass

 High lignin content is good

 Low mineral content

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Do biofuels provide real GHG- mitigation?

From W-t-W-study, JRC

Biogas on manure counts double

on GHG-reduction

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Avoid dummy solutions –

search for win-win