Economic and environmental performance of miscanthus cultivated on marginal land for biogas production

Abstract

Environmental issues surrounding conventional annual biogas crops have led to growing interest in alternative crops, such as miscanthus. In addition to the better environmental performance, miscanthus can be grown on marginal land where no competition with feed and food crops is anticipated. On marginal land however, biomass yields are significantly lower than on good agricultural land. This raises the question of the economic and environmental sustainability of miscanthus cultivated on marginal land for biogas production. This study assessed the environmental and economic performance of miscanthus cultivated on marginal land for biogas production by conducting a Life‐Cycle Assessment and complementary Life‐Cycle Cost analysis. The functional unit chosen was 1 GJ of electricity (GJel.). The substitution of a fossil reference was included using a system expansion approach. Electricity generated by the combustion of miscanthus‐based biogas in a combined heat and power has considerably lower impacts on the environment than the fossil reference in most of the categories assessed. In the impact category “climate change”, the substitution of the marginal German electricity mix leads to a carbon mitigation potential of 256 kg CO2e/GJel.. At 45.12 €/GJel., the costs of miscanthus‐based biogas generation and utilization are considerably lower than those of maize (61.30 €/GJel.). The results of this study clearly show that it can make economic and environmental sense to cultivate miscanthus on marginal land as a substrate for biogas production. The economic sustainability is however limited by the biomass yield. By contrast, there are no clear thresholds limiting the environmental performance. The decision needs to be made on a case‐by‐case basis depending on site‐specific conditions such as local biodiversity.

Downscaling of agricultural market impacts under bioeconomy development to the regional and the farm level—An example of Baden‐Wuerttemberg

“…On the one hand, regions with a high share of unused grassland cultivate PBC without changing the production. For these regions, the implementation of PBC with a special focus on marginal land could be useful (Wagner et al, ). On the other hand, regions with an already intensive grassland utilization further increase this intensity of utilization.…”

Integrated lignocellulosic value chains in a growing bioeconomy: Status quo and perspectives

“…Perennial lignocellulose crops, such as miscanthus, switchgrass and poplar, are suitable for lands with such constraints because genotypes have been identified that are tolerant to abiotic stresses (e.g., drought, salinity, cold) frequently occurring on marginal land (Clifton‐Brown et al, ; Lewandowski et al, ). However, Wagner et al () conclude that careful assessment of the specific prevailing conditions should be performed because biodiversity may be higher in some marginal lands under their existing vegetation than under PBC. PBC can have an environmentally beneficial performance. They only require soil cultivation once in a plantation lifetime of about 20 years, in the establishment phase.…”

“…It can be provided from sustainable forestry and from agricultural production, with agricultural residues and perennial biomass crops (PBC) being the most favourable resources (Clifton‐Brown et al, ; Fabbrini et al, ; Hoeber et al, ). PBC can be integrated into existing farming systems using less favourable land or land marginal for food crop production, with the additional provision of various ecological benefits (Wagner et al, ).…”

Status quo and perspectives of biogas production for energy and material utilization

“…The substitution of 1 GJ of the marginal German electricity mix for instance, which was used as the fossil reference, results in a carbon mitigation potential of 934 kg CO 2 eq. (Wagner et al, ). In addition, Kiesel et al () compared the environmental performance of biogas produced using maize and miscanthus as substrate.…”

“…They reduce the risks of biomass production because they deliver more stable yields over the years than annual crops, which are more influenced in their establishment and growth by precipitation and temperature conditions (Ehmann, Bach, Laopeamthong, Bilbao, & Lewandowski, 2017;Lewandowski, 2016). Both Wagner et al, (2019) and Mangold, Lewandowski, & Kiesel (2019a) take up this point of positive ecological effects of alternative substrates in their contributions and exemplify it with miscanthus. Although miscanthus has so far mainly been used for heat production and material applications, targeted use in biogas plants can also be important in the context of taking ecological effects into account, especially as the methane hectare yields of miscanthus can keep up with those of silage maize .…”