Environmental impacts of bioenergy wood production from poplar short‐rotation coppice grown at a marginal agricultural site in Germany

Abstract

For avoiding competition with food production, marginal land is economically and environmentally highly attractive for biomass production with short-rotation coppices (SRCs) 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 lifetime (combining measurements and modeling approaches) by means of a holistic Life Cycle Assessment (LCA). We analyzed two coppicing rotation lengths (7 9 3 and 3 9 7 years) and seven 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 and 46 kg CO 2 -eq. GJ À1 (or 11-57 Mg CO 2 -eq. ha À1). However, if the produced wood chips substitute oil heating, up to 123 Mg CO 2 -eq. ha À1 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.

Environmental Effects over the First 2½ Rotation Periods of a Fertilised Poplar Short Rotation Coppice

“…Based on these results, fertilisation of young poplar plants is not necessary and can be deferred during the first years. Another marginal agricultural land in southern Germany did not confirm these results [13], which may be explained by a higher mean annual precipitation rate of 790 mm year −1 supporting a less restricted nutrient availability and a better growth. But the authors reported that the benefits of fertiliser-induced higher biomass yields did not counterbalance the negative environmental impacts as for example the leaching of NO 3 − , which had been identified as the main pathway for N loss from the sandy soil of our study site, primarily in the winter when high seepage rates emerged.…”

“…Fertilisation can increase the yield of woody biomass and thus its fossil fuel substitution potential [9,10]. However, it must be taken into account that due to intensive soil management, environmental impacts such as amplified NO 3 − leaching and greater emission of GHG from the soil may occur during the production of trees [11][12][13]. Alongside tillage and harvesting, N fertilisation has often been identified as the operation responsible for NO 3 − leaching and the emission of N 2 O [14,15].…”

Sustainability Assessment of Alternative Thinning Operations in Mediterranean Softwood Plantations

“…Previous studies have shown that the use of several indicators and the combination of different methods to calculate indicator values lead to a strong analytical power for embracing financial, technological, environmental and other aspects of a production system, e.g., [37]. In particular, the feature of Umberto to include 'own' indicators and data, as well as data from the database Ecoinvent turned out to be efficient and productive.…”

Natural climate solutions versus bioenergy: Can carbon benefits of natural succession compete with bioenergy from short rotation coppice?

“…), we apply the following extended equation: UE BM and UE fossil denote upstream emissions per energy unit of biomass and fossil fuel, respectively. Combustion emission factors are taken from IPCC Guidelines (IPCC, 2006a), and upstream emissions are based on literature data (Bradbury, Obeiter, Draucker, Wang, & Stevens, 2013;Brandt, 2011;EC, 2015;Giuntoli, Agostini, Edwards, & Marelli, 2015;Schweier et al, 2017;Scull et al, 2017). Depending on transport distances and modes, characteristics of fossil fuel deposits and other influencing factors, upstream emissions vary widely.…”