Greenhouse gas emissions

Results for GHG intensity of beef production in Europe vary between 7 and 49 kgCO2 / kg

LW (Table A-1 in Appendix A), using mid, averages or conventional figures when ranges

or various results are reported, when results are reported based only in CW (and the

carcass yield is not reported) it has been assumed as 58%. The maximum is for European

generic production from 100% beef systems when including the opportunity cost of land

(Nguyen et al., 2010a). North American studies, normally based on regional level or

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Enteric fermentation, soil and manure management are normally the most important

contributors in the GHG emissions from beef production systems. Differences in the

contribution from these sources can be attributed to different economic flows and also to

the range of emission factors reported in the literature. The GWP of CH4 and N2O used to

characterise these GHG may vary between studies, however this would not result in a

significant variance in the results obtained. A case study of the differences in using

different range of emissions factors has been described by Edward-Jones et al. (2009).

For example, in the study for Sweden completed by Cederberg et al. (2009a) and

involving a hybrid approach, enteric fermentation accounted for 55%, manure

management and application for 19%, feed production and delivery accounted for 23%,

and indirect N2O for 2%of the total GHG emissions of beef. In contrast, enteric

fermentation accounted for 17% and 44% for two different farms in Wales using a bottom-

up approach (Edward-Jones et al., 2009).

GHG emissions from land transformation is a relatively new issue in LCA of meat products

(and in LCA in general), although it was included in an early study by Subak (1999). Two

studies deal with land transformation in detail (Nguyen et al., 2010a; Cederberg et al.,

2011). Nguyen et al. (2010a) studied two issues: the opportunity cost of land associated

with the loss of carbon sequestration potential in beef systems in Europe, and the

increased demand of land for the production of feeds (in particular soy bean produced in

South America). They found that depending on the role of grasslands and croplands, land

used related emissions could be positive or negative. Highly and moderately productive

grasslands acted as carbon sink, whilst extensive use of croplands acted as a carbon

source. In their 100% beef cattle case, GHG emissions were 27.3 kg CO2e / kg CW and

84.1 kg CO2e / kg CW when land transformation was not and was included, respectively

(a threefold increase). Most studies of European beef production have assumed a carbon

balance in soil. Cederberg et al. (2011) considered the land transformation of tropical

rainforest to pasture land in Brazil, and reported the alarming figure of 726 kg CO2e / kg

CW for beef produced in newly deforested land using 20 years for the production period

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period the higher the emissions). In Cederberg et al. (2011), enteric fermentation and

manure management were minor relative contributors (although in magnitude similar with

other studies) in comparison to the GHG emissions from land transformation. These

studies basically included marginal production issues. Nguyen et al. (2010a) studied

marginal production of feed ingredients (in South America) and the consequences of

potential land transformation in Europe, whilst Cederberg et al. (2011) studied the

consequences of the marginal production of beef, taking into consideration that Brazil is

the top exporter of beef and that the associated growth is being driven by exports. The

contrast between marginal and average production is associated with the contrast

between consequential and attributional LCA, which are important issues in LCA studies

(Dalgaard et al., 2008; Thomassen et al., 2008a; Finnveden et al., 2009), and it seems

that they are extremely critical issues in LCA of livestock production.

Results for GHG intensity of lamb production vary considerably from 7.5 to 51.7 kgCO2 /

kg LW for cradle-to-farm-gate studies (Table A-2 in Appendix A). It should be noted that

the high extreme is from the study by Edward-Jones et al. (2009), which is based on one

case study with real data from a farm producing beef and lamb. Similar to beef systems,

enteric fermentation, and soil and manure management are normally the most important

contributors in the GHG emissions from lamb production systems. Differences in the

contribution from these can be attributed to different economic flows and also to the range

of emissions factors in the literature. The differences in using different emissions factors

has been studied by Edward-Jones et al. (2009).

Results for pig meat systems range between 1.6 and 15.7 kg CO2/ kg LW for cradle-to-

farm-gate studies. The highest result is from the only study including emissions

associated with land transformation in feed production and the opportunity cost of land

(Nguyen et al., 2010b). When not including the extremes, GHG emissions per live weight

are lower than for ruminant systems with emissions ranging from 1.5 to 4.9 kg CO2e /kg

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with 2.3 to 4.5 kg CO2e / kg LW. The study by Phong et al. (2011) is a very different case

for multiple output farms in the Mekong Delta.

The GHG emissions contribution from the different processes can vary from study to

study. The contribution of enteric fermentation to the GHG emissions of pig production is

considerably lower than in ruminants. In addition, the effect of previous generation is lower

than in ruminants. The contribution from different sources in the different pig systems

studied is similar. In the base case in Nguyen et al. (2010b), feed production and delivery

accounted for 61% of the GHG emissions, on-farm CH4 and N2O emissions (manure

management and enteric fermentation) for 35%, and on-farm energy use for 5% (only

counting positive GHG emissions, manure land spreading provides credits from the

avoidance of inorganic fertilisers production). In general, emissions associated with feed

production and manure management seem to be the most important contributors (Basset-

Mens and van der Werf, 2005; Dalgaard et al., 2007; Cederberg et al., 2009a; Pelletier et

al., 2010a; Stone et al., 2012).

GHG emissions from poultry meat systems seem to range between 1 and 2 kg CO2 / kg

LW at the farm gate, not taking into account the multiple output system presented in

Phong et al. (2011). Poultry systems do not have enteric emissions, normally the impact

of the previous generation is considered negligible (breeding stock produce a lot of

chicks), and the feed conversion ratios (FCR) are relatively low in comparison to other

land animals. There is an agreement that feed production is the most important life cycle

stage in the GHG emissions of poultry meat systems with example relative contributions

of 82% (Pelletier, 2008) and 83% (Cederberg et al., 2009a). Manure management can

provide negative emissions in some studies, as in Pelletier (2008), because of the

avoidance of inorganic fertiliser production. Two studies on poultry meat that are related

(Williams et al., 2006; Leinonen et al., 2012) included the effect of the breeding stock.

It should be noted that transport of feeds even in cases where studies focus solely on feed

production and delivery is not a major contributor in comparison to agricultural emissions

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comparison to agricultural emissions either (Dalgaard et al., 2007). In fact even when the

transport of meat produced in Brazil to Europe has been included, it has been shown that

transport was not an important contributor in comparison to other sources in livestock

production systems (Cederberg et al., 2009b). In general, transport does not seem an

important relative contributor in meat production systems, as these systems are mostly

characterised by emissions associated with agricultural processes (and/or land

transformation).