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Model Simulation of Cumulative Carbon Sequestration by Switchgrass (Panicum Virgatum L.) in the Mediterranean Area Using the DAYCENT Model

Nocentini, Andrea, Di Virgilio, Nicola, Monti, Andrea
BioEnergy research 2015 v.8 no.4 pp. 1512-1522
Panicum virgatum, arable soils, basins, bioethanol, biomass, carbon dioxide, carbon sequestration, ecosystem services, energy crops, fossil fuels, grains, grasses, heathlands, land use change, pastures, shrublands, simulation models, soil organic carbon, Europe, Mediterranean region
Literature lacks large-scale studies on cumulative C storage capacity of perennial grasses in Europe. At the same time, there is raising interest toward growing biomass crops in Europe, especially under marginal lands of the Mediterranean basin. In the present study, we used the DAYCENT model to estimate the potential of switchgrass (Panicum virgatum L.) as a bioethanol crop to store soil C in the Mediterranean basin. Two scenarios were simulated: (i) cultivation only on heathlands, shrublands, and pastures (1.76 Mha) and (ii) cultivation on heathlands, shrublands, and pastures, plus 5 % of arable lands currently used for cereals (2.97 Mha in total). Cumulative biomass resulted in 184 and 303 Mt over 15 years, while soil organic carbon (SOC) storage values were 6.1 and 12.4 Mt, respectively. Mean annual biomass yield ranged between 5.6 and 9.4 Mg ha⁻¹, while annual SOC accumulation was 0.02 to 0.62 Mg ha⁻¹. Fossil fuel displacement resulted in 54 and 89 Mt of C, i.e., 198 and 327 Mt of equivalent CO₂ in the first and second scenarios, respectively. In the second scenario, switchgrass SOC storage was much more pronounced. However, a loss of 54 Mt of grain commodities was also caused by switchgrass cultivation on 5 % of arable lands with consequent indirect land use change (ILUC) effects. The latter were, however, quite low (16 %) when compared to environmental benefits as stored SOC.