Abstract
AbstractIt is important to demonstrate that replacing fossil fuel with bioenergy crops can reduce the national greenhouse gas (GHG) footprint. We compared field emissions of nitrous oxide (N2O), methane (CH4) and soil respiration rates from the C4 grass Miscanthus × giganteus and willow (salix) with emissions from annual arable crops grown for food production. The study was carried out in NE England on adjacent fields of willow, Miscanthus, wheat (Triticum aetivum) and oilseed rape (Brassica napus). N2O, CH4 fluxes and soil respiration rates were measured monthly using static chambers from June 2008 to November 2010. Net ecosystem exchange (NEE) of carbon dioxide (CO2) was measured by eddy covariance on Miscanthus from May 2008 and on willow from October 2009 until November 2010. The N2O fluxes were significantly smaller from the bioenergy crops than that of the annual crops. Average fluxes were 8 and 32 μg m−2 h−1 N2O‐N from wheat and oilseed rape, and 4 and 0.2 μg m−2 h−1 N2O‐N from Miscanthus and willow, respectively. Soil CH4 fluxes were negligible for all crops and soil respiration rates were similar for all crops. NEE of CO2 was larger for Miscanthus (−770 g C m−2 h−1) than willow (−602 g C m−2 h−1) in the growing season of 2010. N2O emissions from Miscanthus and willow were lower than for the wheat and oilseed rape which is most likely a result of regular fertilizer application and tillage in the annual arable cropping systems. Application of 15N‐labelled fertilizer to Miscanthus and oil seed rape resulted in a fertilizer‐induced increase in N2O emission in both crops. Denitrification rates (N2O + N2) were similar for soil under Miscanthus and oilseed rape. Thus, perennial bioenergy crops only emit less GHGs than annual crops when they receive no or very low rates of N fertilizer.
Highlights
To provide low-carbon (C) energy in the UK, Europe and worldwide, biomass is increasingly used as a renewable resource (Thornley et al, 2009)
N2O emissions were about a factor 5 larger from the annual crops than the perennial bioenergy crops. (Fig. 1a, note scale is an order of magnitude smaller on Fig. 1(a2) to clarify temporal variation of the bioenergy crops)
Mean N2O fluxes over the 21⁄2 years measuring period were 3.7 lg N2O-N mÀ2 hÀ1 from the Miscanthus field, 0.2 lg N2O-N mÀ2 hÀ1 from willow, 8.3 lg N2O-N mÀ2 hÀ1 from annual crop A (ACA) and 32.3 lg N2O-N mÀ2 hÀ1 from annual crop B (ACB) respectively (Fig. 1; (a1)
Summary
To provide low-carbon (C) energy in the UK, Europe and worldwide, biomass is increasingly used as a renewable resource (Thornley et al, 2009). The UK is a signatory to this agreement (Great Britain, 2008b) and the UK government has recently introduced plans, as the Climate Change Act 2008, to reduce greenhouse gas (GHG) emissions by 80% over 1990 levels by 2050 with specific progress to be made by 2020 to tackle climate change and energy security (Great Britain, 2008a) To meet these targets the UK bioenergy industry will have. SOILGHGEMISSIONSFROMBIOENERGYANDANNUALCROPS 409 are sensitive to soil conditions, have global warming potentials (GWPs) tens of times that of CO2 (IPCC, 2007) In temperate climates, such as the UK, the two bioenergy crops that are most promising alternatives to fossil fuels are Miscanthus 9 giganteus (a perennial rhizomatous C4 grass) and short rotation coppice (SRC) willow (C3). The development of second generation biofuel production, based on lignocellulose, is expected to be a major driving force for the expansion of these bioenergy crops
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
