Environmental Impact Assessment
Currently, many different methods are used to assess the environmental impacts and performance of livestock products. Life cycle assessment (LCA) is a welldeveloped internationally standardised method and management tool (ISO 14040 2006; ISO 14044 2006) for quantifying the emissions, resources consumed and environmental and health impacts of products throughout their entire life cycle, from raw material extraction through transport, manufacturing and use all the way to the end of their life (from cradle to grave). According to ISO 14040 (2006), LCA consists of four phases: (1) definition of goal and scope of the analysis, the functional unit, the impact categories and the system boundaries; (2) life cycle inventory (collection of data that identify the system inputs and outputs and discharges to the environment); (3) performance of impact assessment (calculating the contributions made by the material and energy inputs and outputs tabulated in the inventory phase to a specified suite of environmental impact categories, e.g. using the SimaPro 8.1 LCA software package); and (4) analysis and interpretation of results (aiming to identify hot spots and possibilities of decreasing environmental impacts of the system).
It is becoming increasingly common to express the environmental impacts of the production of human food commodities as carbon footprints (CFPs), taking into account all GHGs that are produced during the life cycle of a product. CFPs are expressed as CO2-equivalents (CO2-eq.), CH4 having a value of 25 and N2O a value of 298 (Forster et al. 2007). Ruminant products have higher CFP production compared with other food commodities (Williams et al. 2007); in fact, due to the nature of their diet (based primarily on forages) and digestive system, ruminants produce hydrogen and CH4 during the fermentative digestion of their feed. CH4 constitutes a loss of energy equivalent to 2–12 % of gross energy ingested (Johnson and Johnson 1995).
Limitations of the Standard Method of Sustainability Assessment
According to the LCA procedure, intensification of animal production is generally advocated to mitigate GHGs emissions compared with extensive grazing systems. In fact, intensive systems consider the use of selected breeds, with enhanced productivity, associated with significant reductions in CH4 emissions, related to larger use of concentrates rather than forages (Capper 2012). However, these results focus on emission of greenhouse gases of a single product: beef. On the contrary, for extensive farming systems, the outputs in LCA analysis have to refer not only to material products but also to other non-commodity outputs (OECD 2010) and nonmarketable public goods (Tscharntke et al. 2005), named “ecosystem services” (de Groot et al. 2002; Millennium Ecosystem Assessment 2005; Liu et al. 2010) and related to the multifunctional role of livestock, especially in marginal areas.