Linking Bioenergy and Ecological Services Along Field Margins: The HEDGE-BIOMASS Project

The increasing demand for energy and food, climate change and land availability are causing concerns over land-use conflicts within the “food- energy- environment trilemma”. The HEDGE-BIOMASS project addresses the promotion of a new perennial linear landscape element: bioenergy buffers. Bioenergy buffer strips (BBS) are narrow arable field margins and buffer strips along waterways converted to warm-season grasses and short-rotation woody crops for bioenergy applications. Within the HEDGE-BIOMASS project, an extensive review of scientific literature has been performed to identify the state of the art knowledge on perennial biomass crops with particular reference to their capacity to supply ecological services and to define the most suitable biomass supply chain management design. Implementing new bioenergy buffers could significantly enhance the pollination service and natural enemy control in arable crops by neighbouring presence of beneficial organisms on bioenergy buffer. A positive interaction between crop management and species richness was found in bioenergy crops for a long list of taxa. With regards to miscanthus and switchgrass, the deep-rooting system proved to be the main factor for improving water/nutrient use efficiency. Herbaceous BBS can promote positive alterations of C cycling pathways in terms of increased belowground carbon (C) allocation and belowground fine root biomass. Short-rotation woody crops in BBS, instead, increase the litter C and nitrogen (N) input to soil and start to act as net C sink few years after establishment. Several positive experiences have been reported in literature on removal efficiency of non-point source agricultural pollutants coming from adjacent agricultural fields. A 5-10 m wide herbaceous BBS can efficiently mitigate sediment, N and total phosphorus (P) runoff. However, if BBS are placed on flatland regions with slow runoff flow the risk of P delivery from buffers can be increased due to dissolved P remobilization from standing aboveground litter mediated by microbial processes. To the best of our knowledge, there is no data regarding denitrification processes in shallow groundwaters under BBS . Moreover, soil N2/N2O emission dynamics and annual N2O budget in BBS remain uncertain. Nevertheless, it has been reported that BBS can significantly reduce nitrate leaching compared with surrounding row-cropping systems from the second growing season. Regarding biomass yield achieved on BBS it emerged that no data are available for switchgrass and miscanthus while extensive literature is available for woody crops. We can assume that biomass yields of herbaceous buffers are similar to those reported for large scale cultivations because efficient mechanisms of nutrients up-take, trapping, filtration and infiltration occur usually in BBS. Warm-season grasses presented on average the highest values of greenhouse gas savings, particularly when biomass is used for electricity production by gasification. The width of the bioenergy buffer strip is a fundamental element to design effective systems. Unfortunately, from the logistic point of view, biomass harvesting and collection is limited by the linear arrangement of biomass crops along arable field margins. As a consequence of this restricted operating space, the intra- and extra-farm fragmentation of logisticoperations seems to be the main critical step of BBS management compared to the traditional large-scale bioenergy cultivation scenario. Within the framework of HEDGE-BIOMASS project a comprehensive assessmentof ecological services provided by bioenergy buffers is being carried out. Furthermore, a multicriteria spatial analysis combining GIS, Life Cycle Assessment and SWAT model, will be performed to at landscape level propose new bioenergy production scenarios along field margins. This research will develop an energy production strategy that offer an opportunity to rethink how and where bioenergy feedstocks can be sustainably produced and to optimize the trade-offs between the delivery of multiple ecological services and farmer incomes within limited land resources.