The project included an well to wheel assessment of the BTL production chain and asocio-economic assessment of farmer perceptions towards short rotation coppice plantations.
GHG assessment of SRC plantations
As part of the green house gas assessment of the BTL production chain, Lignovis calculated the GHG emissions of a commercial SRC production within the OPTFUEL project under WP 7. Based on the experiences from the establishment, management and harvesting of OPTFUEL SRC plantations, Lignovis developed a hands-on calculation tool for greenhouse gas assessment of large scale SRC production. As a result it can be concluded that SRC plantations show an exceptionally good climate gas balance in comparison to other energy crops.
Nitrogen fertilization with the subsequent emission of N2O accounts for the major part of GHG emissions of conventional agriculture. According to research results and experiences from OPTFUEL plantations, N-fertilization of SRC plantations is not
required as it does not provide significant growth benefits. Commercial SRC plantations are usually not fertilized (sufficient atmospheric input), which should be considered in all calculation models as this massively decreases the total GHG emissions.
However, direct and indirect N2O emissions, which are normal for every kind of agricultural land use system, still account for almost 50 % of the total CO2eq emissions for production of wood chips from SRC plantations. This is caused by microbial denitrification processes in the soil and through leaching and run-offs also in surface waters.
Figure 2: Total greenhouse gas emission of commercial SRC cultivation and harvesting
In total 2.5 g CO2eq are emitted for 1 MJ wood chips delivered at plant with a 50 km transport distance. Hence, wood from SRC plantations is the most CO2eq efficient way to produce dedicated feedstock for BTL facilities. There are still optimization potentials, especially regarding the harvesting and logistic chain.
Assessment and optimization of environmental benefits from SRC plantations
SRC plantations generally offer a higher biodiversity (flora & fauna) compared to conventional agriculture. In cooperation with a German NGO, the Nature and Biodiversity Conservation Union (NABU) a trial plantation with additional measurements has been set up, to further increase the SRC benefits.
The measures included:
- Create irregular structures with gaps
- Plant different poplar and willow clones in mixed patterns
- Flower strips on the edge and headlands
- Integration of domestic tree species in mixed patterns
- Partial harvesting of plantation
- Avoidance of pre-emergent herbicides application
The additional costs for management and harvesting as well as losses due to lower yields are currently surveyed. Also other OPTFUEL fields in Brandenburg have been used for an inventory of animal and plant species. The NABU research
project will continue until 2015.