The results of this study show that the obtainable energy yields
from anaerobic digestion of nature conservation grass are suffi-
cient to fully cover the energy requirements for the acquisition and
processing of the grass. By applying the average yields obtained
from 256 sampling points in Denmark harvested once or twice
per year, EROEI values ranging from 1.7 to 3.3 were estimated. On
national level a net energy gain of more than 600,000 GJ, corresponding
to ≈15% of the total Danish production of biogas in 2012,
can be achieved. As the aim of harvesting the biomass is to conserve
nature, the removed biomass can be considered a by-product
from this process. Thus it can be argued that the energy investments
of conducting nature conservation should be allocated fully
to nature conservation functions, since it is the primary reason for
the management of the grasslands. Estimating the energy balance,
considering only the remaining energy inputs, would increase the
EROEI and NEG values. This could favour the use of nature conservation
grass for biogas production in the final analysis.