2. Aim and scope
This paper performs a review of a large portion of the existing
scientific literature that explicitly used life cycle assessment
(LCA) methodology, or a life-cycle approach, to estimate the environmental
impacts of biomass energy uses. Authors of this paper
assume that the reader already has a basic knowledge of LCA and
bioenergy production chains, so that general information on these
aspects is not provided here.
The main purpose of this work is to discuss and synthesize the
key issues and striking features emerged from a review process of
the wide scientific literature available, and analyzing the approaches
used by the different authors to face these issues, thusreporting the current state of the art. Contrarily to other bioenergy
review studies (Gnansounou et al., 2009; Larson, 2006; von Blottnitz
and Curran, 2007), in this paper there is not an attempt to
harmonize results across studies and report them in bars with
wide ranges (usually estimated by gathering data from papers located
in different areas and based on different data sources and
assumptions), but qualitative results will be rather discussed.
Qualitative results for energy balance, GHG balance and other environmental
impact categories are each described in specific sections.
References to studies showing quantitative results are
given in the text and specific figures and examples from reliable
studies are sometimes reported across this paper to reinforce and
enrich the results and the following discussion. Then, existing
methodological constraints and bottlenecks are described and discussed
in relation with policy maker’s requirements and normative
frameworks, so identifying existing shortcomings and future research
challenges.
This review covers a time period of approximately fifteen years,
in which a large numbers of studies have been published. In order
to narrow down the number of studies and focus the discussion on
the recent and future trends in LCA of bioenergy systems, but at
same time without disregarding older contributions, the literature
search was mainly based on the following criteria: before 2006,
only review papers and relevant case studies were included; from
2006 till date, both reviews and original research papers were
considered.
Only studies with a clear claim to be based on a life-cycle approach
to estimate environmental impacts are included. In addition,
only papers written in English and with good and reliable
supporting data and references were selected. Cost analysis and
economic assessments are out of the scope of this paper. The total
number of reviewed studies is 94, most of which (74) are papers
published in scientific journals and the remaining (20) are grey literature.
This set of studies does not include the complete literature
on LCA of bioenergy, but it does represent a thorough cross section
of public available papers. In the Appendix, detailed information
for each of the reviewed studies can be found in Tables A1 and
A2. All the results described in the following section are derived
from an interpretation and critical assessment of these tables.