Environmental impacts of bioenergy wood production from poplar short-rotation coppice grown at a marginal agricultural site in Germany
For avoiding competition with food production, marginal land is economically and environmentally highly attractive for biomass production with short-rotation coppices (SRC) of fast-growing tree species such as poplars. Herein, we evaluated the environmental impacts of technological, agronomic and environmental aspects of bioenergy production from hybrid poplar SRC cultivation on marginal land in southern Germany. For this purpose different management regimes were considered within a 21-year
... time (combining measurements and modeling approaches) by means of a holistic Life Cycle Assessment (LCA). We analyzed two coppicing rotation lengths (7x3 and 3x7 years) and seven Accepted Article This article is protected by copyright. All rights reserved. nitrogen fertilization rates and included all processes starting from site preparation, planting and coppicing, wood chipping and heat production up to final stump removal. The 7-year rotation cycles clearly resulted in higher biomass yields and reduced environmental impacts such as nitrate (NO 3 ) leaching and soil nitrous oxide (N 2 O) emissions. Fertilization rates were positively related to enhanced biomass accumulation, but these benefits did not counterbalance the negative impacts on the environment due to increased nitrate leaching and N 2 O emissions. Greenhouse gas (GHG) emissions associated with the heat production from poplar SRC on marginal land ranged between 8-46 kg CO 2 -eq. GJ -1 (or 11-57 Mg CO 2 -eq. ha -1 ). However, if the produced wood chips substitute oil heating, up to 123 Mg CO 2 -eq.ha -1 can be saved, if produced in a 7-year rotation without fertilization. Dissecting the entire bioenergy production chain, our study shows that environmental impacts occurred mainly during combustion and storage of wood chips, while technological aspects of establishment, harvesting and transportation played a negligible role. GHG. On the right side the ranges of GWP from fossil sources (Cherubini et al., 2009; Ecoinvent, 2010 ) are shown. (b) Relative contribution of each process to the decline in GWP saving potentials starting from Field-GHG. An overview of the here presented production chains can be found in Table 1 .