A parsimonious model for calculating the greenhouse gas emissions of miscanthus cultivation using current commercial practice in the United Kingdom

Abstract

Life cycle assessment (LCA) is a widely recognized tool for the assessment of the potential environmental impacts associated with the life cycle of a product or service. The environmental impact category most commonly quantified in LCAs is global warming potential, a measure of greenhouse gas (GHG) emissions. For agricultural products such as miscanthus, the creation of an inventory can be labour‐intensive and is context‐specific. This impairs the transfer of results to comparable but not necessarily similar situations. Farmers and small‐ and medium‐sized enterprises cannot easily dedicate resources for this purpose (in particular when using marginal land) and often lack the expertise to do so. Simplified LCA models could offer a promising solution to this problem. They are simplified versions of more complex models that require only a few critical parameters to calculate representative results. This study develops such a model for the computation of GHG emissions associated with commercial miscanthus cultivation. The model focuses on rhizome‐based propagation and the indirect harvesting method (cutting to swath, swathing, baling). A parametric life cycle inventory (LCI) was established and used to identify the most influential parameters by means of a global sensitivity analysis (GSA). A simplified model for calculating GHG emissions associated with miscanthus cultivation was developed by fixing input parameters with a low relevance at their median impact values. Six of 38 parameters were identified as relevant parameters: soil carbon sequestration, harvestable yield, duration of cultivation period, quantities of nitrogen and potassium fertilizer applied, and distance between field and customer. The simplified model allows practitioners an easy assessment of the GHG emissions associated with the production and supply of miscanthus. It thus provides a wider audience facilitated access to LCA knowledge and promotes its use as a management and reporting tool in bio‐based industries.

Comparative LCA studies of simulated HMF biorefineries from maize and miscanthus as an example of first‐ and second‐generation biomass as a tool for process development

“…It includes soil preparation, crop establishment, fertilization, weed control, and harvest of the biomass. For miscanthus, a 20‐year cultivation period is taken (Lask, Kam, et al, 2021). Biomass yields were assumed in accordance with the geographical focus and account for natural yield variability.…”

“…On the one hand, the parameter carbon sequestration can easily dominate the variation in GHG emissions associated with miscanthus production. On the other hand, the values for carbon sequestration can range broadly from 0 to 2.2 t C ha −1 and year −1 (Lask, Kam, et al, 2021). To avoid that this parameter impedes the further assessment, a conservative approach of 0 t C ha −1 and year −1 was considered.…”

Implications of large‐scale miscanthus cultivation in water protection areas: A Life Cycle Assessment with model coupling for improved policy support

“…A conversion efficiency of 75% was adapted from the ecoinvent dataset ‘heat production, wood chips from industry, at furnace 5000 kW, CH’ (Wernet et al, 2016). The transportation distance from the farm to the heat plant was assumed to be on average 60 km (Lask et al, 2021). The biogenic CO 2 released during combustion was considered burden‐free, as the CO 2 has been withdrawn from the atmosphere during the growth of the miscanthus within the same year.…”

“…In comparison to annual crops, the rate of nitrate leaching to surface water and groundwater is lower in perennial crops (Brandes et al, 2018; Hussain et al, 2019; Manevski et al, 2018; Sarkar et al, 2011). Due to the minimal maintenance requirements, the impact on climate change of miscanthus biomass per kilogram dry matter is also lower compared to other crops (Lask et al, 2021; Poore & Nemecek, 2018). At the same time, it is a multipurpose biomass crop with high yield potential (Hastings et al, 2017; Lewandowski et al, 2016).…”

Evaluation of sugar feedstocks for bio‐based chemicals: A consequential, regionalized life cycle assessment

“…In this study, the method of Schmidt et al (2015) was used to account for iLUC emissions. It was chosen because it (i) has been applied in different studies on biofuels and biorefinery products (Corona et al, 2018; Lask et al, 2021; Prapaspongsa & Gheewala, 2017) and (ii) was previously used to support decision making by the Danish Environmental Protection Agency and the Danish Energy Agency (Høst‐Madsen et al, 2014; Schmidt & Munoz, 2014).…”