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Long-term plantations of perennial energy crops in marginal land
The cultivation of crops on unused, marginal or abandoned land is one of the criteria for the production of low-ILUC risk biofuels defined by the RED II. Perennial lignocellulosic crops such as giant reed, switchgrass and miscanthus are well adapted to grow on marginal and idle land, and can represent an additional source of biomass for advanced biofuels and bio-based products. The selection, cultivation and harvesting of perennial biomass crops was widely investigated by several international projects; in BECOOL, a series of long-established stands of different perennial crops were managed and monitored, observing their annual biomass yields for the entire duration of the project. These included plantations of switchgrass and giant reed established in 1998, 2002 and 2012 on marginal land in Greece, giant reed and switchgrass established in 2004 on an idle riverside land of 1.4 ha in central Italy, large fields of switchgrass established in 2010, and tall wheatgrass established in 2013 in Spain, and two hectares of eucalyptus established in 2013 in central Italy. Thanks to the continuation of the monitoring of those stands during BECOOL, it was possible to collect data and to draw conclusions on the long-term cumulative and average biomass yields of some of the most long-lived experimental perennial plantations available nowadays in Europe. In Italy, the mean yield of the 18 years old
plantation of giant reed was 20 dry t/ha over the period and in Greece, the mean yields of the 19 years-old plantation ranged from 7 to 17 t/ha depending on the level of irrigation. In both countries, the yields of the first ten years of the plantation were above the mean yield of the period. Figure 27 below shows that after the first years of high productivity (benefiting from initial NP fertilization and irrigation), the yields of giant reed decreased significantly, however a fertilization with 150 kg/Ha of nitrogen in 2016 was effective in raising up the yields again to 15-18 t/Ha. In the last year of observation (2021), the yields were still above 10 t/Ha in Italy and 6-8 t/Ha in Greece.
Fig 27. Annual and mean yields of giant reed in Italy (UNIBO) and in Greece under different irrigation levels (CRES).
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