Conversion Technologies 97
that were employed. Life cycle assessment identifies generation and transfer of these
environmental impacts from one part of process to another and allows their quantifi-
cation. LCA therefore allows to identify the most crucial steps of the production and
disposal of a product or a service and to perform techno-economic analysis of alterna-
tive routes to minimise its environmental impacts without significantly affecting other
parameters like performance or cost. To perform LCA, the process is broken down into
its individual components and quantified. Usually, following stages of the process are
distinguished: materials extraction, processing and manufacturing, use, and disposal.
These stages are then broken down into fine details that become useful in identifying
‘hot spots’ of a process that generate most environmental impact. More sustainable alter-
natives or energy efficient processes can be then proposed and implemented for these
stages.
3.5.3 Environmental Assessment of Bioenergy Production Processes
A number of studies evaluated the environmental impact of bioenergy production pro-
cesses and identified processes that are most promising. It is beyond the scope of this
book to provide detailed analysis of each of these studies, especially taking into con-
sideration that studies of this kind should be related to local conditions, policies and
availability of resources. These factors vary tremendously from region to region and
as such can have huge impact on the analysis. There are however certain ‘hot spots’
of bioenergy production processes that have been highlighted and should be consid-
ered when developing renewable alternatives to current fossil fuel products. Four major
categories of potential environmental impacts can be distinguished for bioenergy pro-
duction processes:
3.5.3.1 Impacts Related to Land-Use Change
Production of dedicated feedstocks for bioenergy and biomaterials requires changes of
land use. These changes can have major impact on sustainability of the process and can
determine to what extent bioenergy production can make an impact on greenhouse gas
emissions. Although exact quantification of the effects of land-use change is a com-
plex issue and beyond the scope of this chapter, several examples will hopefully help to
understand the issue better. Many ecosystems such as rainforests, peatlands, savannas,
or grasslands contain significant amounts of sequestered carbon and act as a carbon
sink. Reallocation of these resources for the production of energy crops may result in
the release of this carbon to the atmosphere especially if the land-use change is per-
formed through slash and burn practices. The land-use change from original ecosystem
to bioenergy production will result in the formation of ‘bio-fuel carbon debt’ that would
require many years of bioenergy feedstock cultivation only to restore the carbon bal-
ance before the land-use change was implemented [44]. On the other hand, land-use
change that promotes accumulation of soil organic carbon can have a positive envi-
ronmental effect. For example, perennial rhizomatous energy grasses likeMiscanthus
or switchgrass provide a rarely mentioned alternative that can create a ‘carbon asset’
shortly upon land change due to accumulation of significant amount of carbon in the
soil. As long as the initial land use did not have an extraordinary carbon sequestration
capacity like rainforests, the conversion of land to rhizomatous perennial grasses can
bring benefits in terms of carbon sequestration.
