Clifton-Brown, J. C., Breuer, J., Jones, M. B. (2007). Carbon mitigation by the energy crop, Miscanthus. Global Change Biology. 13 (11), 2296-2307 Sponsorship: EU JOUB-0069 / AIR-CT92-0294 RAE2008Biomass crops mitigate carbon emissions by both fossil fuel substitution and sequestration of carbon in the soil. We grew Miscanthus x giganteus for 16 years at a site in southern Ireland to (i) compare methods of propagation, (ii) compare response to fertilizer application and quantify nutrient offtakes, (iii) measure long-term annual biomass yields, (iv) estimate carbon sequestration to the soil and (v) quantify the carbon mitigation by the crop. There was no significant difference in the yield between plants established from rhizome cuttings or by micro-propagation. Annual off-takes of N and P were easily met by soil reserves, but soil K reserves were low in unfertilized plots. Potassium deficiency was associated with lower harvestable yield. Yields increased for 5 years following establishment but after 10 years showed some decline which could not be accounted for by the climate driven growth model MISCANMOD. Measured yields were normalized to estimate both autumn (at first frost) and spring harvests (15 March of the subsequent year). Average autumn and spring yields over the 15 harvest years were 13.4?1.1 and 9.0?0.7 t DW ha?1 yr?1 respectively. Below ground biomass in February 2002 was 20.6?4.6 t DW ha?1. Miscanthus derived soil organic carbon sequestration detected by a change in 13C signal was 8.9?2.4 t C ha?1 over 15 years. We estimate total carbon mitigation by this crop over 15 years ranged from 5.2 to 7.2 t C ha?1 yr?1 depending on the harvest time.Peer reviewe

Bioenergy from crops is expected to make a considerable contribution to climate change mitigation. However, bioenergy is not necessarily carbon neutral because emissions of CO 2 , N 2 O and CH 4 during crop production may reduce or completely counterbalance CO 2 savings of the substituted fossil fuels. These greenhouse gases (GHGs) need to be included into the carbon footprint calculation of different bioenergy crops under a range of soil conditions and management practices. This review compiles existing knowledge on agronomic and environmental constraints and GHG balances of the major European bioenergy crops, although it focuses on dedicated perennial crops such as Miscanthus and short rotation coppice species. Such second-generation crops account for only 3% of the current European bioenergy production, but field data suggest they emit 40% to >99% less N 2 O than conventional annual crops. This is a result of lower fertilizer requirements as well as a higher N-use efficiency, due to effective N-recycling. Perennial energy crops have the potential to sequester additional carbon in soil biomass if established on former cropland (0.44 Mg soil C ha À1 yr À1 for poplar and willow and 0.66 Mg soil C ha À1 yr À1 for Miscanthus). However, there was no positive or even negative effects on the C balance if energy crops are established on former grassland. Increased bioenergy production may also result in direct and indirect land-use changes with potential high C losses when native vegetation is converted to annual crops. Although dedicated perennial energy crops have a high potential to improve the GHG balance of bioenergy production, several agronomic and economic constraints still have to be overcome.Keywords: biofuel, carbon debt, carbon footprint, land management, methane, Miscanthus, nitrous oxide, short rotation coppice, soil organic carbon Greenhouse gas saving with bioenergy -a European perspectiveThe European Union has committed to increase the proportion of renewable energy from 9% in 2010 to 20% of Correspondence: Axel Don,

The substantial stocks of carbon sequestered in temperate grassland ecosystems are located largely below ground in roots and soil. Organic C in the soil is located in discrete pools, but the characteristics of these pools are still uncertain. Carbon sequestration can be determined directly by measuring changes in C pools, indirectly by using 13 C as a tracer, or by simulation modelling. All these methods have their limitations, but long-term estimates rely almost exclusively on modelling. Measured and modelled rates of C sequestration range from 0 to > 8 Mg C ha − 1 yr − 1 . Management practices, climate and elevated CO 2 strongly influence C sequestration rates and their influence on future C stocks in grassland soils is considered. Currently there is significant potential to increase C sequestration in temperate grassland systems by changes in management, but climate change and increasing CO 2 concentrations in future will also have significant impacts. Global warming may negate any storage stimulated by changed management and elevated CO 2 , although there is increasing evidence that the reverse could be the case.

John C. Clifton-Brown, Paul F. Stampfl, Michael B. Jones (2004). Miscanthus biomass production for energy in Europe and its potential contribution to decreasing fossil fuel carbon emissions. Global Change Biology, 10 (4)509-518 RAE2008Field trials throughout Europe over the past 15 years have confirmed the potential for high biomass production from Miscanthus, a giant perennial rhizomatous grass with C4 photosynthesis. However, policies to promote the utilization of biomass crops require yield estimates that can be scaled up to regional, national and continental areas. The only way in which this information can be reliably provided is through the use of productivity models. Here, we describe MISCANMOD, a productivity model, which was used in conjunction with a GIS to plot potential, non-water-limited yields across Europe. Modelled rainfed yields were also calculated using a water balance approach based on FAO estimates of plant available water in the soil. The observed yields were consistent with modelled yields at 20 trial sites across Europe. We estimate that if Miscanthus was grown on 10% of suitable land area in the European Union (EU15), 231 TWh yr?1 of electricity could be generated, which is 9% of the gross electricity production in 2000. Using the same scenario, the total carbon mitigation could be 76 Mt C yr?1, which is about 9% of the EU total C emissions for the 1990 Kyoto Protocol baseline levels.Peer reviewe

HighlightsThe impact of grazing on SOC is climate-dependent.Grazing increases SOC for C4 but decreases it for C3 and C3-C4 mixed grasslands.Grazing increases TN and BD but has no effect on soil pH.