Abstract
This paper analyses the comparative advantage of using silage maize or grass as feedstock for anaerobic digestion to biogas from a greenhouse gas (GHG) mitigation point of view, taking into account site-specific yield potentials, management options, and land-use change effects. GHG emissions due to the production of biogas were calculated using a life-cycle assessment approach for three different site conditions with specific yield potentials and adjusted management options. While for the use of silage maize, GHG emissions per energy unit were the same for different yield potentials, and the emissions varied substantially for different grassland systems. Without land-use change effects, silage maize-based biogas had lower GHG emissions per energy unit compared to grass-based biogas. Taking land-use change into account, results in a comparative advantage of biogas production from grass-based feedstock produced on arable land compared to silage maize-based feedstock. However, under current frame conditions, it is quite unrealistic that grass production systems would be established on arable land at larger scale.
Highlights
The production of biogas from agricultural feedstock has been propagated as a promising pathway for reducing fossil CO2 emissions from energy use [1]
In grassland management the lowest emissions were found with the system with low intensity (Grass II, 2 cuts), while all other grassland management systems had higher greenhouse gas (GHG) emissions compared to silage maize
Our results show that the conversion of grassland to arable land for growing silage maize for biogas production leads to a remarkable additional net release of GHG, which are not compensated by substituting electric energy based on natural gas or the current energy mix (Table 7)
Summary
The production of biogas from agricultural feedstock has been propagated as a promising pathway for reducing fossil CO2 emissions from energy use [1]. The production and use of biogas from agricultural wastes and animal manure has the advantage that the energy of these resources can be utilized, which otherwise cannot be used efficiently. In 2015, about 8000 biogas plants digested agricultural feedstock in Germany [4]. The area dedicated for energy plants for biogas production in Germany summed up to more than 1.2 million ha, which is 7.5% of the total utilized agricultural area [5]. While silage maize is still the dominant energy crop in anaerobic digestion in Germany, efforts are being made to foster the use of other crops for the production of bioenergy. Feedstock costs per energy unit are often higher for feedstock from grassland compared to silage maize [7], which creates an incentive to use silage maize instead of feedstock from grassland for biomass digestion. The use of feedstock from grassland, especially from conservation areas, may complicate the fermentation process due to the structure of this feedstock [6,8,9,10], which creates another disincentive for the use of this feedstock for biogas production
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
