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| Titel |
Comparison of GHG fluxes from conventional and energy crop production from
adjacent fields in the UK, using novel technologies |
| VerfasserIn |
James Benjamin Keane, Phil Ineson, Sylvia Toet, James Stockdale, Harry Vallack, Emanuel Blei, Mark Bentley, Steve Howarth |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250133376
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| Publikation (Nr.) |
 EGU/EGU2016-13980.pdf |
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| Zusammenfassung |
| With combustion of fossil fuels driving anthropogenic climate change, allied to a diminishing
global reserve of these resources it is vital for alternative sources of energy production to be
investigated. One alternative is biomass; ethanol fermented from corn (Zea mays) or sugar
cane (Saccharum spp.) has long been used as a petroleum substitute, and oilseed
rape (OSR, Brassica napus) is the principal feedstock for biodiesel production in
Germany, the third biggest producer of this fuel globally. Diverting food crops
into energy production would seem counter-productive, given there exists genuine
concern regarding our ability to meet future global food demand, thus attention
has turned to utilising lignocellulosic material: woody tissue and non-food crop
by-products such as corn stover. For this reason species such as the perennial grass
Miscanthus (Miscanthus x giganteus) are being cultivated for energy production,
and these are referred to as second generation energy crops. They are attractive
since they do not deplete food supplies, have high yields, require less fertiliser
input than annual arable crops, and can be grown on marginal agricultural land. To
assess the effectiveness of a crop for bioenergy production, it is vital that accurate
quantification of greenhouse gas (GHG) fluxes is obtained for their cultivation in the
field. We will present data from a series of studies investigating the GHG fluxes
from the energy crops OSR and Miscanthus under various nutrient additions in a
comparison with conventional arable cropping at the same site in the United Kingdom
(UK).
A combination of methods were employed to measure fluxes of CO2, CH4 and N2O from
both soil and vegetation, at various temporal and spatial scales. Conventional manual
chambers were deployed on a monthly regime to quantify soil GHG fluxes, and were
supplemented with automated soil flux chambers measuring soil respiration at an hourly
frequency. Additionally, two novel automated chamber systems allowed, for the first time,
continuous ecosystem exchange of all three biogenic GHGs to be measured from OSR and
Miscanthus at high spatial resolution (< 1 m2).
Highest GHG emissions were seen from arable crops, but despite low fertiliser input,
tillage caused Miscanthus to be a net carbon source, and compost addition increased N2O
emissions. OSR represented a net carbon sink during its growth, but N2O emissions
resulting from application of mineral nitrogen fertiliser reduced this sink by 50%.
Automated measurements revealed a hitherto unreported temperature-independent
diurnal pattern in soil respiration under Miscanthus, which was in stark contrast to an
adjacent barley (Hordeum vulgare) crop. Consequently, the time of day at which any
comparison of soil respiration between these two crops is made strongly biases the
findings.
Our data highlight the delicate balance which energy crops must maintain in order to
ensure carbon-neutrality, and suggest that crops requiring fertiliser input will potentially
become a net GHG source once indirect emissions (e.g. from fertiliser production) are
accounted for. Furthermore, diurnal patterns of GHG flux should be assessed and used to
guide suitable future manual measurement regimes. |
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