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PARALLEL SESSION 3A: LAND USE CHANGE 8 th Int. Conference on LCA in the
Parallel session 3a: Land Use Change
Agri-Food Sector, 1-4 Oct 2012
Bioenergy production from perennial energy crops: a consequential
LCA of 12 bioenergy chains including land use changes
Lorie Hamelin 1* , Davide Tonini 2 , Thomas Astrup 2 , Henrik Wenzel 1
1
Institute of Chemical Engineering, Biotechnology and Environmental technology (KBM), University of Southern Denmark, Campusvej
55, 5230 Odense M., Denmark
2
Department of Environmental Engineering, Technical University of Denmark, Miljøvej, Building 113, 2800 Lyngby, Denmark.
Corresponding author. E-mail: loha@kbm.sdu.dk
ABSTRACT
In the endeavour of optimizing the sustainability of bioenergy production in Denmark, this consequential life cycle assessment
(LCA) evaluated the environmental impacts associated with the production of heat and electricity from one hectare of Danish arable
land cultivated with three perennial crops: ryegrass, willow and Miscanthus. For each, four conversion pathways were assessed
against a fossil fuel reference: I) anaerobic co-digestion with manure, II) gasification, III) combustion in small-to-medium scale
biomass combined heat and power (CHP) plants and IV) co-firing in large scale coal-fired CHP plants. Soil carbon changes, direct
and indirect land use changes as well as uncertainty analysis (sensitivity, MonteCarlo) were included in the LCA. Results showed
that global warming was the bottleneck impact, where only two scenarios, namely willow and Miscanthus co-firing, allowed for an
improvement as compared to the reference (-82 and -45 t CO2-eq. ha -1 , respectively).
Keywords: perennial crops, combustion, land use changes, gasification, anaerobic digestion
1. Introduction
The ambition of the energy policy in Denmark is to reach a 100% renewable energy system by 2050
(Lund et al., 2011). Several studies have been conducted to design and optimize such a system, and these all
highlight the indispensability of a biomass potential of around 35%–50% of the overall energy consumption
(Lund et al., 2011; Energinet.dk, 2010; Klimakommissionen, 2010). Though biomass is a renewable energy
source, it is not unlimited in supply, and does involve considerable environmental costs. One of the most
critical costs of bioenergy relates to its incidence on land use changes (LUC) (Searchinger et al., 2008; Edwards
et al., 2010), i.e. the conversion of land from one use (e.g. forest, grassland or food/feed crop cultivation)
to another use (e.g. energy crop cultivation). One way to minimize these LUC impacts could be through
favouring the cultivation of perennial energy crops (e.g. perennial ryegrass, willow and Miscanthus) instead
of annual crops (e.g. maize, barley, wheat, sugar beet). In fact, it is acknowledged that perennial energy
crops nowadays represent the most efficient and sustainable feedstock available for bioenergy production in
temperate regions (Bessou et al., 2011).
The goal of this study is to assess the environmental impacts associated with the production of bioenergy
(heat and electricity) from 1 hectare (ha) of Danish arable land cultivated with ryegrass, willow and
Miscanthus, considering four different biomass-to-energy (BtE) conversion pathways: i) anaerobic codigestion
with manure, ii) gasification, iii) combustion in small-to-medium scale biomass combined heat and
power (CHP) plants and iv) co-firing in large scale coal-fired CHP plants.
2. Methods
2.1. Life cycle assessment model
The environmental assessment presented in this study was performed using consequential life cycle assessment
(LCA). The functional unit upon which all input and output flows were expressed is 1 ha of agricultural
land used to grow the selected energy crops. The geographical scope considered for the LCA was
Denmark, i.e. the data inventory for crops cultivation and BtE plants were specific for Danish conditions.
Similarly, the legislative context of Denmark (e.g. fertilisation) was considered. The temporal scope considered
was 20 years, i.e. all assessed systems were operated for a 20 years duration. The life cycle impact assessment
was carried out according to the Danish EDIP 2003 method (Hauschild and Potting, 2005), to
which one impact category, “Phosphorous as resource”, was added based on the Impact 2002+ method (Jolliet
et al., 2003). Background LCA data were based on the Ecoinvent v.2.2 database, and the assessment was
facilitated with the LCA software SimaPro 7.3.3. Foreground LCA data essentially included Danish-specific
data for agricultural and energy conversion processes, and the impacts associated with capital goods (foreground
data only) as well as those related to transportation of the residues (i.e. ash and digestate) have been
excluded. The systems assessed considered three perennial crops (ryegrass, willow and Miscanthus) and four
BtE conversion technologies (anaerobic co-digestion, gasification, combustion in small-to-medium scale
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