Especially when assessing the environmental burdens associated with the produc­tion of bioenergy and related products, particular focus should be given to the impact due to land-use change.

Land-use, depending on the land management practices, can be accepted as the main cause of soil degradation. Perennial crop systems, such as SRC plantation systems, tend to accumulate soil organic carbon and can serve to remediate contaminated soil (Brandao et al. 2010). Land-use change to bioenergy production can occur in two ways: (i) directly, when uncultivated land and pasture are converted to produce energy crops, or (ii) indirectly, through displacing food and feed crop production to new land areas previously not used for cultivation. From an LCA perspective, direct land-use change is often straightforward and easy to include in the assessment (Reijnders and Huijbregts 2008), although there are often uncertainties in the levels of carbon stock changes due to variations in local conditions and a lack of reliable field trial data (Fig. 11.2).

Mills et al. (2005) define six factors affecting the accumulation of carbon within an ecosystem:

• Carbon (C) storage is a function of mean annual precipitation (MAP) and temperature. Soil carbon and tends to increase with an increase in mean annual precipitation (Dalal and Mayer 1987; Hontoria et al. 1999). This is most likely due to primary productivition being a function of rainfall (Knapp and Smith 2001) and organic matter inputs into the soil tend to be greater in mesic than in arid regions.

• Carbon storage will increase with an increase in woody biomass.

Cs : permanent C loss in living biomass

Cs : permanent C loss in litter and soil

• Frequent fires will lead to a decrease in Carbon storage in both biomass (Tilman et al. 2000) and soils (Bird et al. 2000).

• Tillage will reduce Carbon storage in biomass and soils (Tiessen et al. 1992; Gregorich et al. 1994; Aslam et al. 2000; Francis et al. 2001).

• The establishment or maintenance of a permanent cover of vegetation (e. g. pasture, thicket) will maintain or increase soil Carbon (Dalal and Chan 2001; Dominy and Haynes 2002). The effect of pasture establishment on the organic carbon storage capacity depends on the structure of the natural vegetation. Pastures may accumulate more carbon than natural grassland if a dense grass sward is established, but will have less carbon than woody systems.

• Any of the above effects will be dependent on changes to, and the inherent chemical and physical properties of the soil (Oades 1993; Zech et al. 1997; Percifal et al. 2000). The establishment of plantations on former grassland, for example, may be expected to reduce soil water content, improve soil aeration, and therefore reduce soil carbon storage (Birch 1958).

The possible change of carbon storage pools in the forest (i. e. trees, soil and litter) brought about by removing wood from forests should be considered, at least as a qualitative description (Schlamadinger et al. 1997). The most important carbon source in forest ecosystems are living vegetation (trees and other vegetation), dead organic matter and the forest soil (Jungmeier et al. 2003). In interpreting the carbon cycle, it is important to consider the following aspects: assumed rotation period of the forest ecosystem, changes to carbon storage pools, landfill by wood-based waste, and recycling (Fig. 11.3).