Comparing energy balances, greenhouse gas balances and biodiversity impacts
of contrasting farming systems with alternative land uses
H.L. Tuomisto
a,
⇑
, I.D. Hodge
b
, P. Riordan
a
, D.W. Macdonald
a
a
Wildlife Conservation Research Unit, University of Oxford, The Recanati-Kaplan Centre, Tubney House, Abingdon Road, Tubney, Oxon OX13 5QL, UK
b
Department of Land Economy, University of Cambridge, Cambridge CB3 9EP, UK
article info
Article history:
Received 15 June 2011
Received in revised form 8 December 2011
Accepted 4 January 2012
Available online 11 February 2012
Keywords:
Greenhouse gas emissions
Organic farming
Conventional farming
Integrated farming
Anaerobic digestion
Miscanthus
abstract
Life cycle assessment (LCA) is commonly used for comparing environmental impacts of contrasting farm-
ing systems. However, the interpretation of agricultural LCA studies may be flawed when the alternative
land use options are not properly taken into account. This study compared energy and greenhouse gas
(GHG) balances and biodiversity impacts of different farming systems by using LCA accompanied by
an assessment of alternative land uses. Farm area and food product output were set equal across all of
the farm models, and any land remaining available after the food crop production requirement had been
met was assumed to be used for other purposes. Three different management options for that land area
were compared: Miscanthus energy crop production, managed forest and natural forest. The results illus-
trate the significance of taking into account the alternative land use options and suggest that integrated
farming systems have potential to improve the energy and GHG balances and biodiversity compared to
both organic and conventional systems. Sensitivity analysis shows that the models are most sensitive for
crop and biogas yields and for the nitrous oxide emission factors. This paper provides an approach that
can be further developed for identifying land management systems that optimize food production and
environmental benefits.
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
Many studies have compared the environmental impacts of
organic and conventional farming (Feber et al., 2007; Mondelaers
et al., 2009; Williams et al., 2010). They show wide variation in the
environmental impacts within both organic and conventional sys-
tems. Arguably, the greatest weakness of organic farming is its low
yields, primarily resulting from lower levels of inputs, and higher
abundances of pests and weeds (Köpke et al., 2008). Thus, organic
farming requires more land for producing the same volume of out-
put than conventional farming. Therefore, it is important to identify
the specific practices that can provide environmental benefits and
develop integrated farming systems that utilise those practices
while maintaining relatively high levels of output per unit area.
Life cycle assessment (LCA) is commonly used for assessing envi-
ronmental impacts of agricultural production (Nemecek et al., 2011;
Stone et al., 2012; Thomassen et al., 2008; Williams et al., 2010). LCA
uses a ‘‘cradle-to-grave’’ approach in accounting simultaneously for
several environmental aspects of a product or service (ISO 14040,
2006). The impacts are allocated with respect to a unit of product
termed the functional unit (FU). Generally agricultural LCAs use
system boundaries from input production (e.g. fertilizers, pesticides
and fuels) up to the farm gate and the FU is a unit of the agricultural
product studied leaving the farm gate. Due to the complexity and
high land use impacts of agricultural systems, agricultural LCAs face
some specific challenges compared to industrial LCAs.
In agricultural LCA studies, there is scope for misinterpretations
if the alternative land use options are not taken into account. Thus,
some studies suggest that extensive farming systems are more
environmentally sound than intensive systems (Cederberg, 1998;
Hole et al., 2005). However, land is a limited resource for which
there are always alternative potential uses. By definition extensive
farming systems require more land to produce a given amount of
product than do intensive systems. Extensive systems may have
lower energy need per product unit due to low input use, but if
the alternative land use options are taken into account, it may be
found that the overall energy balance of the intensive system is
more favourable (Berlin and Uhlin, 2004).
If only a fraction of the land used in an intensive system is
needed to produce the same product output, the land saved can
be utilized for other purposes, e.g. bioenergy production. Therefore,
the intensive system might produce more energy than is needed
for the production process and that excess energy could be used,
for instance, to replace oil in heating, electricity production or
transportation fuels. After taking account of the alternative land
use options, the overall energy efficiency of the intensive farming
0308-521X/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.agsy.2012.01.004
⇑
Corresponding author. Tel.: +39 0332 786731; fax: +39 0332 785601.
E-mail address: htuomist@gmail.com (H.L. Tuomisto).
Agricultural Systems 108 (2012) 42–49
Contents lists available at SciVerse ScienceDirect
Agricultural Systems
journal homepage: www.elsevier.com/locate/agsy