LCA Food 2012 in Saint Malo, France! - Manifestations et colloques ...

PARALLEL SESSION 3A: LAND USE CHANGE 8 th Int. Conference on LCA in the
Agri-Food Sector, 1-4 Oct 2012
biomass CHP plants and co-firing in large scale coal-fired CHP plants). A total of 12 scenarios have therefore
been assessed. The system and boundary conditions are illustrated in Figure 1.
Figure 1. Illustration of the system boundary considered for all scenarios. Dotted lines indicate avoided processes,
and full lines indicate processes induced by the scenarios. (*) Not all the converted land is to be cultivated
in barley, and not all the Danish barley displaced is replaced, due to various market mechanisms.
For all BtE technologies, the energy produced was considered to be used for CHP production,
thereby substituting the production of marginal heat and power. In the present study, the marginal electricity
source was assumed to be from coal-fired power plants, and the marginal heat from natural gas based domestic
boiler. As illustrated in Figure 1, the digestate produced from anaerobic digestion was used as a fertiliser
(for N, P and K), which avoided marginal mineral N, P and K fertilisers to be produced and used, based on
the content of N, P and K of the digestate. The marginal N, P and K fertilisers considered were calcium ammonium
nitrate, diammonium phosphate and potassium chloride, respectively, conformingly with Hamelin et
al., (2012). Further, based on the model from Hamelin et al., (2011), it was considered that the manure portion
used for co-digestion would have otherwise been stored and applied on land, without digestion.
The three thermal bioenergy scenarios (i.e. gasification, combustion and co-firing) implied negligible
residual unconverted carbon that is found in the bottom ashes, fly ashes and eventual waste water. The
bottom ashes were assumed to be used for road construction, substituting for natural aggregates, while the fly
ashes were assumed to be utilised for backfilling of old salt mines with negligible environmental impacts
(not illustrated in Figure 1). Treatment of waste water was not included.
All bioenergy scenarios involved the use of Danish agricultural land in order to grow the energy crops.
Based on Weidema (2003), it is considered that the (Danish) land needed to grow the energy crops will be
taken from land under spring barley cultivation. Based on the consequential LCA logic, as well as on recent
studies (Searchinger et al., 2008; Kløverpris, 2008), this resulting drop in supply of Danish spring barley will
cause a relative increase in agricultural prices, which then provide incentives to increase the production
elsewhere. Such increased crop production may stem from both increased yield and land conversion to cropland,
the latter being also referred to as indirect land use change (iLUC) (Searchinger et al., 2008; Kløverpris,
2008). As illustrated in Fig. 1, and as in recent iLUC studies (e.g. Laborde et al., 2011; Tyner et al.,
2010), this study included the environmental impacts of the latter only.
2.2. Life cycle inventory (LCI) for crops and BtE technologies
The LCI of all crops was based on a recent Danish consequential LCI (Hamelin et al., 2012), which comprises
all processes involved during the cultivation stage, up to harvest, and include soil carbon changes. For
all crops, the fertilisation operations were performed in conformity with Danish regulations involving an
upper limit for the amount of N to be applied on the field, both as mineral fertiliser and animal slurry. Based
on Hamelin et al., (2012), the life-cycle considered for perennial ryegrass, willow and Miscanthus planta-
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