• Open Access

Efficient use of reactive nitrogen for cultivation of bioenergy: less is more

Authors

  • I. CALLESEN,

    1. Biosystems Division, Risø National Laboratory for Sustainable Energy, Technical University of Denmark – DTU, PO Box 49, Frederiksborgvej 399, DK-4000 Roskilde, Denmark
    2. DTU Management Engineering, Produktionstorvet, DTU – Building 424, 2800 Kgs. Lyngby, Denmark
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  • M. S. CARTER,

    1. Biosystems Division, Risø National Laboratory for Sustainable Energy, Technical University of Denmark – DTU, PO Box 49, Frederiksborgvej 399, DK-4000 Roskilde, Denmark
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  • H. ØSTERGÅRD

    1. Biosystems Division, Risø National Laboratory for Sustainable Energy, Technical University of Denmark – DTU, PO Box 49, Frederiksborgvej 399, DK-4000 Roskilde, Denmark
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I. Callesen, Biosystems Division, Risø National Laboratory for Sustainable Energy, Technical University of Denmark – DTU, Building 309, PO Box 49, Frederiksborgvej 399, DK-4000 Roskilde, Denmark, tel. +454525 4672, fax+45 4593 3435, e-mail: inca@man.dtu.dk

Abstract

A further increase in nitrogen (N) intensive biomass supplies to substitute fossil carbon sources implies inclusion of additional reactive nitrogen (Nr) into the biosphere. A Danish model study compared low-intensity managed seminatural beech forest and a winter wheat system with respect to N losses and greenhouse gas (GHG) emissions. Losses of reactive N to air and groundwater per unit of energy produced were four to six times higher for the winter wheat system. The energy efficiency was an order of magnitude higher in the forest system, whereas the related GHG emission reduction by fossil coal substitution differed by <25%. The question is whether a low or a high intensity of cultivation yields the best overall ecosystem service performance? Given the detrimental effect of excess reactive N on natural ecosystems, we suggest that bioenergy production from unfertilized forest with seminatural structure and function should be preferred over N-intensive crop production.

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