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Published online 5 January 2006
Published in J Environ Qual 35:231-239 (2006)
DOI: 10.2134/jeq2005.0121
© 2006 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America
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TECHNICAL REPORTS

Greenhouse Gas Emissions from Conventional, Agri-Environmental Scheme, and Organic Irish Suckler-Beef Units

J. W. Casey* and N. M. Holden

Department of Biosystems Engineering (Bioresources Modelling Group), University College Dublin, Earlsfort Terrace, Dublin 2, Ireland

* Corresponding author (john.casey{at}ucd.ie)

Received for publication April 11, 2005.

   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
The problems of overproduction within the European Union countries and the environmental impact of agriculture have lead to the introduction of schemes that aim to reduce both. Beef (Bos taurus) production forms a large component of the Irish agricultural industry and accounts for more than one quarter of agricultural economic output. Recently, the European CAP (Common Agricultural Policy) has been re-evaluated to include supplementary measures that encompass the environmental role of agriculture rather than just the production role. A life cycle assessment (LCA) method was adopted to estimate emissions per kilogram of CO2 equivalent per kilogram of live weight (LW) leaving the farm gate per annum (kg CO2 kg–1 LW yr–1) and per hectare (kg CO2 ha–1 yr–1). Fifteen units engaged in suckler-beef production (five conventional, five in an Irish agri-environmental scheme, and five organic units) were evaluated for emissions per unit product and area. The average emissions from the conventional units were 13.0 kg CO2 kg–1 LW yr–1, from the agri-environmental scheme units 12.2 kg CO2 kg–1 LW yr–1, and from the organic units 11.1 kg CO2 kg LW yr–1. The average emissions per unit area from the conventional units was 5346 kg CO2 ha–1 yr–1, from the agri-environmental scheme units 4372 kg CO2 ha–1 yr–1, and from the organic units 2302 kg CO2 ha–1 yr–1. Results indicated that moving toward extensive production could reduce emissions per unit product and area but live weight production per hectare would be reduced.

Abbreviations: AES, agri-environmental scheme • CAP, Common Agricultural Policy • EF, emission factor • EU, European Union • FU, functional unit • GHG, greenhouse gas • ISO, International Standards Organisation • LCA, life cycle assessment • LW, live weight • REPS, rural environment protection scheme • TGE, total greenhouse gas emissions • TMR, total mixed ration


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
BEEF is the second most important sector of the Irish agricultural industry and accounts for more than one quarter of agricultural output (Central Statistics Office, 2004). The high quality of Irish beef is due to the fact that it is produced from grass, with the animals grazing outdoors in the summer and being fed silage and grain indoors in the winter (Moloney et al., 1999). Agriculture generates about 10% of the EU (European Union) GHG (greenhouse gas) emissions (EUROPA, 2005a) and nearly 30% of the emissions in Ireland (Department of Environment and Local Government, 2000). When the European Commission proposed a seven-point emergency plan to offset the problems of oversupply in the beef sector, measures designed to encourage extensification (a policy within the European Community by which land is farmed less intensively, Allwords, 2005) in beef production were strengthened (European Commission, 2000). These measures were designed to reduce environmental impact but not specifically GHG emissions. A question that remains is whether the EU extensification policy will lead to a reduction in GHG emissions per unit product and area from the beef sector.

Organic production is increasingly perceived as a potential solution to many policy and environmental problems facing agriculture in both developed and developing countries (Lampkin, 1990). The problems of overproduction in the industrialized countries and the environmental impact of agriculture have lead to the introduction of schemes such as the new EU single-payment scheme (EUROPA, 2005b) and the AES (agri-environmental scheme, European Community, 1999). Increasingly, subsidization of agricultural production is being decoupled from the intensity at which the agricultural goods are produced. This has lead to greater emphasis being placed on the aesthetic quality and the environmental role of agriculture rather than just production. Europe's CAP was designed for regulation of production, trade, and processing of agricultural products in the EU. Recently, CAP has been re-evaluated to include supplementary measures, encompassing the environmental role of agriculture rather than just the production role. The AES became an accompanying measure to the CAP in 1992 with the intention of promoting farming methods that are compatible with the protection of the environment (European Community, 1999). In Ireland, AES was implemented as the REPS (rural environmental protection scheme), which was designed to reward farmers for carrying out activities in an environmentally friendly manner. Strict guidelines are set out for nutrient management: i.e., the permitted level of total N applied to the grassland area cannot exceed 260 kg ha–1; the permitted level of N applied from animal and other wastes on the same area cannot exceed 170 kg ha–1; the maximum level of chemical N that can be applied to grassland can never be greater than the planned level of N from animal and other wastes applied on the same area; and habitat conservation is required (Government of Ireland, 2000). The N limitations dictate the stocking density that the land can support. Adopting REPS is generally taken to result in extensification (lower yield per unit area from fewer inputs, therefore more area per unit product) because of the limitations placed on inputs and stocking densities. The scheme was developed before GHG emissions from agriculture were a serious consideration. Previous work by Casey and Holden (2005b) investigated milk production systems functioning conventionally and within the REPS framework. The work on beef production systems presented here considers what conventional, REPS, and organic systems of production mean in terms of GHG emissions. The consideration of emissions is not limited to the land area of the farm or the geopolitical boundary of Ireland. It encompasses all the estimated emissions associated with the system, wherever they occur.

An LCA type method was adopted to estimate GHG emissions because it defines a reproducible, objective method of delimiting the production system, and it can be used to define and quantify GHG emissions (Casey and Holden, 2005a). According to standard methodology (ISO, 1997), LCA is used to assess a particular system in a number of impact categories (e.g., energy consumption, acidification, ozone depletion, and land use), but the methodology has yielded successful results in terms of assessing changes within a single impact category. Therefore, LCA methodology can be used to ascertain whether a particular management decision will reduce GHG emissions or simply transfer them elsewhere in the system "emission basket." Casey and Holden (2005a, 2005b, 2005c), Phetteplace et al. (2001), Kramer et al. (1999), Flessa et al. (2002), and Ogino et al. (2004) have all used the methodology in a similar manner.

The objective of the work presented here was to assess the GHG emissions from case study suckler-beef units, including conventional, REPS, and organic production, to assess whether moving toward more extensive methods of production could reduce GHG emissions per kilogram of live weight leaving the farm and per area used for production.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
The LCA methodology requires the definition of a FU (functional unit) that is an attribute of the product or system, and is used as a quantitative scalar for comparison purposes. There can be more than one FU because a system may have a number of possible functions, but the FU must be definable and measurable (ISO, 1997). In the case of suckler-beef systems, the main product is live weight; therefore, the FU defined for this study was the production of 1 kg of liveweight during 1 yr. By scaling emissions relative to a FU of live weight and scaling to a 1-yr time frame, it is possible to get an accurate picture of both the emissions and the potential for emissions reduction (Casey and Holden, 2005c). Allocation to byproducts is not necessary with this FU because the live weight of animals leaving the production unit will be subject to the production of byproducts after post-processing, which is outside the system boundary of the study.

To facilitate comparison with area-based inventory studies, a second scalar was defined as the total land area used for the production, including that used for externally sourced concentrate feed, during 1 yr. The total land area to operate the suckler-beef unit was recorded for the units studied. The additional land area required to supply concentrate feed was calculated from yields of crops included and scaled to the required amount in area to supply the feed (Casey and Holden, 2005b).

The GWP (global warming potential index) was used to determine contribution to the greenhouse effect. The index is defined as the cumulative radiative forcing effect between the present moment and a selected time in the future caused by a unit mass of gas emitted in the present. The emissions are measured in terms of a reference gas, CO2 (IPCC, 1996a). The GWP of 1 kg CO2 (with a time span of 100 yr) is 1, 1 kg CH4 is 21, and 1 kg N2O is 310 (Audsley et al., 1997). The TGE (total greenhouse gas emissions) are determined as:

[1]
where mi is the mass (kg) of the emitted gas. The result is expressed in terms of kg CO2 equivalents (Heijungs et al., 1992). The total impact is expressed as TGE/LW (kg CO2 kg–1 LW yr–1) (Casey and Holden, 2005c) relative to product output and TGE/ha (kg CO2 ha–1 yr–1) (Casey and Holden, 2005b) relative to total land area used.

The system boundary is defined by the GHG emissions associated with live weight production up to the point of transportation away from the suckler-beef unit "cradle to farm gate." The system (Fig. 1 ) includes the physical limits of the beef units and their activities: (i) the emissions associated with the individual ingredients of the concentrate feed production, transport, and processing; (ii) emissions associated with N fertilizer production, transportation, and application; (iii) emissions associated with livestock and related manure management; (iv) emissions associated with electricity used, and diesel fuel for agricultural operations (e.g., fertilizer application, manure application, and forage production). As in previous studies, emissions associated with the production of medicines, insecticides, machines, buildings, and roads are excluded because of lack of data (Cederberg and Mattsson, 2000). Direct N2O emissions from cattle were excluded from the study as these are known to be negligible (Tiedje, 1988), and CO2 from enteric fermentation was also excluded because it is generally regarded as recycling from sustainably produced plant matter and thus makes no net addition to the atmosphere (IPCC, 1993). Geopolitical boundaries are not considered limits to the system.



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  		Fig. 1. Flowchart of the "cradle to farm gate" beef production system representing the processes included for describing a typical suckler-beef unit in Ireland with regard to: (i) concentrate feed, (ii) fertilizer, (iii) manure management, and (iv) electricity and diesel fuel use (adapted from Casey and Holden, 2005c).

 
No allocation was required for the LW FU because any subdivision of the product occurs outside the system boundary. There is a theoretical possibility that allocation should be applied to the area scalar since land area can have multiple functions during the time frame of production, but as there is no way of estimating this effect and we believe it to be very small, no allocation was applied.

The suckler-beef units all operated the same basic systems whereby animals were raised predominantly on grass, with silage and concentrates fed indoors when weather did not permit grazing. The animals were housed on slats, with the exception of the organic units for which partial shedding was used in combination with slatted shedding and outdoor wintering of cattle in some instances. In all cases, slurry stores were emptied by 1 June, with the exception of the organic units where manure spreading did not take place until September. To make the systems comparable, a 50/50 ratio was assumed for males vs. females produced on the units. There were no major differences in the breeds used across all the units with the exception of one of the organic units where the angus breed was reared.

Detailed questionnaires were circulated to 68 units in suckler-beef production in the southern half of Ireland; 26 replies were received, 15 of which provided suitable quality data. Site visits to the 15 units, A–O, were performed to ensure the high quality of the data supplied by cross-checking with farm records and field observation. Exact location details are not presented because the farmers were guaranteed anonymity. Units A–E functioned conventionally, F–J functioned within REPS, and K–O were organic accredited farms (accredited by the Irish Organic Farmers and Growers Association). Properties of each unit are presented in Table 1, the assumed diets fed are presented in Table 2, and the EFs (emission factors) used are presented in Table 3. The emissions from each suckler-beef unit were estimated using EF ranges collated by Casey and Holden (2005c).


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  		Table 1. Summary of the 15 case study suckler-beef units investigated, including five units under conventional production, five units in a rural environmental protection scheme (REPS), and five units under organic production.

 

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  		Table 2. Total greenhouse gas emissions (TGE) and data source associated with the supply of 1 Mg of concentrate feed to suckler-beef units in Ireland (contribution to total in parentheses).

 

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  		Table 3. Emission factor (EF) ranges and data sources used to calculate greenhouse gas emissions from the case study suckler-beef units (adapted from Casey and Holden, 2005b, 2005c).

 
Unlike previous studies of Irish livestock systems (Casey and Holden, 2005a, 2005b), where enteric methane emission was estimated using IPCC standard values, in this study it was calculated using an IPCC methodology (IPCC, 1996a). The calculation was facilitated by determining required daily dry matter intake, metabolizable energy, and gross energy, using a nutrition software package called RUMNUT (RUMNUT, 2004) to estimate a diet based on surveyed livestock performance. RUMNUT is based on relationships defined by a range of protein systems. It uses the metabolizable protein system (as recently revised from 1992 standards) (AFRC, 1992).

Four diets were defined by starting with information supplied by the farmers and consultation with feed suppliers around the country to identify the most popular concentrate feed supplied to the beef industry. This information is commercially sensitive and therefore we cannot disclose specific feeds from specific feed suppliers or users. The diets were refined to be viable using RUMNUT (Table 2). Diet 1 was assumed for all conventional and REPS units except units H and J, which used TMR (total mixed ration, which is a blend of all foodstuffs [forages and grains] in one feed [Ag-Bag International, 2005]) with Diets 2 and 3, respectively. The organic units were assumed to all use Diet 4. Animal LW and a CH4 conversion factor (Ym) of 0.06 were also used as inputs into the IPCC equations to calculate enteric CH4 emitted per day (IPCC, 1996a). Separate calculations were undertaken for a cow producing a calf, a male beef animal that becomes the final product, and a female animal that becomes the final product. The enteric methane emissions for the cow were calculated on an annual basis while the emissions from the beef animal were calculated for the whole life cycle of the animal and then annualized. A 10% range was applied to all enteric fermentation values to account for within-herd variations, given the fact that a number of CH4 conversion factors exist for a range of animal breeds in literature from 0.04 (Van der Honing et al., 1981) to 0.075 (Blaxter, 1989) depending on diet and animal performance across the units surveyed.

Emission factors for CH4 from slurry storage were applied using error ranges estimated from Husted (1994), which were selected as best suited to suckler-beef units with different winter periods and negligible slurry storage during the summer period. Range values for solid manure were adapted from Husted (1994) and applied to the organic units because organic manure management is markedly different from the other units analyzed. Ranges of values for N2O emissions from stored manure were adapted from the IPCC default value of 2% (mass basis, IPCC, 1996b). A range of N2O emissions have been suggested for manure excreted at pasture of 0.5–3.0% of total excreted N (Oenema et al., 1997; Anger et al., 2003; Yamulki et al., 1998), where total N produced was calculated for individual animals from estimates by Smith and Frost (2000) and total excreta from DARDNI (2003). Emissions of N2O are variable because those that are livestock-induced in pasture are related to the grass growth stage and the time of year. Methane emissions from dung at pasture (derived from Jarvis et al., 1995) were selected because they were most suited to the Irish situation. Ranges of values for southwest England for N2O and CH4 from slurry application were taken as ±50%. Chadwick et al. (1999) presented values for emissions from slurry and solid manure application. These United Kingdom data were considered to be most relevant to the Irish situation (Casey and Holden, 2005a). Range values for N2O emissions from N application were applied from IPCC guidelines (IPCC, 1996b). A range of ±50% was applied to CH4 emissions from pasture. The emissions associated with fertilizer production, shipping, trucking, electricity, and diesel fuel combustion were selected from the limited data available and a ±5% range was used to account for uncertainty.

The emissions associated with concentrate feed (allocation for the production process was applied) were adapted from Casey and Holden (2005c) for the diets presented in Table 2. To account for uncertainty, a ±5% range was used with these data. Feed consumed per unit was derived from concentrates fed per animal multiplied by the number of animals (Table 1) and was used to calculate an emission per unit by multiplying by the EF in Table 2.

The possible error associated with the calculation of TGE/FU (for all FUs) was assessed by taking 2000 random combinations of EF values from within EF ranges assumed for each suckler-beef unit to obtain an estimated distribution. Thus, using all minimum or maximum EF values would give an estimate of the extremes of emissions that might occur. Sampling within this space provided an estimate of the possible error associated with the EF uncertainty. Differences between beef units were assessed using a paired t-test (H0: there is no significant difference between the average TGE/FU for any two suckler-beef units) to examine whether trends in average TGE/FU reflected a response that accounted for the uncertainty in the EF values. The significance of TGE/FU differences between the three types of beef-suckler units was assessed using one-way ANOVA (H0: there is no significant difference between TGE/FUs for conventional, REPS, and organic beef-suckler units).


   RESULTS AND DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
CONCLUSIONS
 REFERENCES
 
Conventional Beef-Suckler Units
Of the conventional units surveyed, Unit A had the highest TGE/LW (Table 4). Comparing Unit A with Unit C, which had the lowest TGE/LW of the conventional units surveyed, it is evident that Unit A is using too much fertilizer and may be slightly overfeeding female stock for the LW return (all comparisons are relative to the findings of Drennan, 1999). If Unit A were to lower fertilizer input and lower the concentrate feed input to the female stock, reductions in TGE/LW could be attained. Unit E operates efficiently in terms of balancing inputs with output. Unit C has the highest TGE/ha of all the units surveyed, but the lowest TGE/LW of the conventional producers. This unit is associated with the highest stocking density, largest number of animals, and a large output per hectare compared with the other conventional units.


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  		Table 4. Summary of estimated range of CO2-equivalent contribution of the main emissions components total greenhouse gas emissions (TGE)/ha and TGE/live weight (LW) for each suckler-beef unit.

 
Rural Environmental Protection Scheme Beef-Suckler Units
Of the REPS units surveyed, Unit J has the lowest TGE/LW. This may be attributed to the efficiency with which the unit is operated with moderate output of LW per hectare (Table 1) coupled with proficient use of inputs. The TGE/ha was not the lowest because the stocking density was not among the lowest of the units surveyed. Unit G had the highest TGE/ha of the REPS units. This was because the large concentrate feed use and high stocking rate caused a TGE penalty.

Units F and H had similar outputs per hectare. The lower emissions achieved by Unit F in both TGE/LW and TGE/ha may be due to the shortened life of the male animals on Unit F (579 vs. 730 d, Table 1), which yielded emissions 1% lower for TGE/LW and 4% lower for TGE/ha. This may be because shortening the life span of an animal should reduce manure-related emissions, feed-related emissions, and winter-housing-related emissions. The daily emissions per animal increase up to a certain age, thus a short-lived animal accumulates lower average daily emissions.

Organic Beef-Suckler Units
Of the organic units surveyed, Unit M had the largest TGE/ha. This unit has the longest days at grass, the highest stocking rate, and lightest animals sold at the youngest age. The unit produces angus beef, an early maturing breed that is usually produced for quality rather than weight (Sakowski et al., 2001), therefore the moderately high TGE/LW arises because of the lower weight per animal. The TGE/ha value may be largely attributable to the higher stocking density than the other organic units. Increasing LW gain per animal by feeding more concentrate might reduce emissions. While not the focus of this study, the emissions from Unit M raise the issue of how society should balance the quality of food against the environmental impact of its production.

Unit L has the lowest TGE/LW of all the units surveyed, which can be attributed to the total absence of concentrate feed; but this unit also had heavy animals compared with other organic units. Unit N yielded the lowest TGE/ha. This unit was associated with the lowest stocking density recorded for all the units surveyed, the most days at grass for organic units, and relatively few animals. Unit K produced the highest TGE/ha of the organic units because of its very high LW per hectare. Overall, the lower emissions from the organic units reflects the low output per hectare, low input of concentrates and nutrients, and very short wintering periods achieved with low stocking densities.

Extensification Effects
The result of the paired t-tests indicated that the 15 suckler-beef units were all significantly different from each other (p < 0.05) in terms of TGE/LW and TGE/ha (Table 4). The ANOVA result indicated that there was a significant difference between the three types of suckler-beef units (p < 0.01) in terms of TGE/LW and TGE/ha. On average, the organic units had significantly lower GHG emissions than the conventional and REPS units, and the REPS units had significantly lower emissions than the conventional units. These results suggest that, in general, extensifying beef production will result in lower GHG emissions per unit produced and per unit area. The average TGE/LW from the conventional units was 12.98 kg CO2 kg–1 LW yr–1. The average TGE/LW was lower for the REPS units (12.20 kg CO2 kg–1 LW yr–1), and lower again for the organic units surveyed (11.13 kg CO2 kg–1 LW yr–1). Using average values for the classes of suckler-beef units surveyed, the conventional units had 14% greater GHG emissions than the organic units with respect to TGE/LW and 57% greater GHG emissions in terms of TGE/ha. The REPS units had, on average, 6% greater GHG emissions than the organic units on a LW basis and 18% greater on an area basis. Based on the units surveyed, moving from a conventional or REPS farming system to an organic farming system should lead to a reduction in GHG emissions in terms of both LW and area.

The relationship between GHG emissions and farming intensity of the suckler-beef units can be expressed in terms of grazing intensity (Fig. 2 ), N fertilizer rate (excluding Units K–O because no fertilizer was used) (Fig. 3 ), total concentrates fed per unit (Fig. 4 ), and area per unit output (Fig. 5 ). These are similar intensity measures to those considered by Casey and Holden (2005b) when examining the intensity of dairy production. Significant linear correlations were found between TGE/LW and grazing intensity (r = 0.5, p < 0.05; Fig. 2a) and TGE/LW and fertilizer (r = 0.9, p < 0.05; Fig. 3a), but no significant relationship was found with concentrate feed per unit (r = 0.2, p > 0.05; Fig. 4a). A significant relationship was found between LW per unit area and TGE/LW (r = 0.6, p = <0.05; Fig. 5a). Overall, as intensity increases, there is an increase in TGE/LW, and the relationship is reflected in three of the four intensity measures used. Significant linear correlations were found between TGE/ha and grazing intensity (r = 0.9, p < 0.05; Fig. 2b) and TGE/ha and fertilizer rate (r = 0.8, p 0.05; Fig. 3b). The emergence of a significant relationship between TGE/ha and concentrates fed (r = 0.6, p < 0.05; Fig. 4b) reflects the additional area, beyond the beef unit, required to produce the crops from which the concentrates were derived. Live-weight output per hectare was significantly correlated with TGE/ha (r = 0.99, p < 0.05; Fig. 5b). Overall, as intensity of production increases, there is an increase in TGE/ha.



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  		Fig. 2. The relationship between (a) total greenhouse gas emissions (TGE)/live weight* and (b) TGE/ha* and stocking density. ({blacksquare} Conventional farms A–E; • REPS farms F–J; {blacktriangleup} organic farms K–O.) *Gradient parameter significant at p < 0.05. Significant differences were found between the stocking densities at which the farms functioned (p < 0.05).

 


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  		Fig. 3. The relationship between (a) total greenhouse gas emissions (TGE)/live weight * and (b) TGE/ha* and rate of N fertilizer applied. ({blacksquare} Conventional farms A–E; • REPS farms F–J; {blacktriangleup} organic farms K–O.) *Gradient parameter significant at p < 0.05. Significant differences were found between the amounts of fertilizer applied to each farm (p < 0.05).

 


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  		Fig. 4. The relationship between (a) total greenhouse gas emissions (TGE)/live weight{dagger} and (b) TGE/ha* and concentrate fed. ({blacksquare} Conventional farms A–E; • REPS farms F–J; {blacktriangleup} organic farms K–O.) {dagger}Gradient parameter not significant at p > 0.05. *Gradient parameter significant at p < 0.05. Significant differences were found between the amounts of concentrate consumed per animal on each farm (p < 0.05).

 


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  		Fig. 5. The relationship between (a) total greenhouse gas emissions (TGE)/live weight* and (b) TGE/ha* and output of live weight per hectare. ({blacksquare} Conventional farms A–E; • REPS farms F–J; {blacktriangleup} organic farms K–O.) *Gradient parameter significant at p < 0.05. Significant differences were found between the amount of live weight produced per hectare on each farm (p < 0.05).

 
A comparison with LCA studies by different authors is extremely difficult due to enormous differences in assumptions used to formulate the LCA assessment (de Boer, 2003). Studies have been conducted, however, by Ogino et al. (2004), Cederberg (2002), and Subak (1999) using beef production. To try to compare the values presented by these three studies with this study is extremely difficult due to differences in production methods and system boundary assumptions.

The Role of Diet
The use of the different assumed diets (Table 2) did not have much effect on TGE for each unit. Diets 2 and 3 (Table 1) had emissions 25 and 15% lower, respectively, per megagram than Diet 1, but this did not translate into relative emissions reductions of similar magnitude. The organic units are not allowed to use conventional concentrate feed; therefore, organic units used Diet 4 (Table 2). The barley was assumed to be either grown on the farms or purchased locally. The emissions associated with rolling the barley were incorporated into the diesel fuel use on the organic farms. The emissions associated were 67% lower per Mg than Diet 1 (Table 2). Dietary manipulation by using locally sourced ingredients was shown by Casey and Holden (2005c) to have little effect on total GHG emissions. The TGE/LW from Units H and J are among the lowest of the REPS and conventional units with the exception of Units F and G. This indicates that small reductions might be achieved by feeding a TMR with predominantly locally sourced ingredients, but there are many more interactions that have to be considered in terms of adequate LW production per hectare, correct use of artificial fertilizer, and correct manure management.

Productivity
There is a small drop in productivity when moving from conventional (average 412 kg LW ha–1) to REPS management (average 359 kg LW ha–1), and a greater drop with the move to a fully organic system (average 206 kg LW ha–1). A reduction of 50% in LW output per hectare was the average result of moving to an organic system. Therefore, while organic production will reduce GHG emissions, it would not permit the same national production of beef if widely adopted. Moving from a conventional to a REPS system gave reductions on the order of 13% in terms of LW per hectare (Table 4) and reductions of 6% as TGE/LW and 18% as TGE/ha. Farming within the REPS specifications has the added advantage of further benefiting the environment (e.g., specific slurry spreading dates that reduce runoff potential, fencing of water courses to reduce pollution, management of hedgerows to preserve bird and other habitats) without greatly affecting LW production per hectare. On average, the REPS units fed 15% more concentrate feed to compensate for lower herbage production due to a 49% lower fertilizer usage compared with the conventional units surveyed. Farming within the REPS specifications limits inorganic N inputs but not concentrate fed. Moving toward a widespread adoption of REPS production would reduce GHG emissions while allowing a relatively high level of LW production per hectare to be maintained.


   CONCLUSIONS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
REFERENCES
 
The LCA type approach proved successful in quantifying the emissions from the units surveyed in a comparative framework that could be readily analyzed. This type of study had not been previously performed for suckler-beef units and the results indicate that moving from conventional suckler-beef production to an AES production system would reduce GHG emissions in terms of both product and area. An even greater reduction in emissions could be achieved by organic suckler-beef production but at the cost of a large drop in LW production per hectare. A shift toward more extensive beef production is occurring in Europe in line with European agricultural policy, and therefore a reduction in GHG emissions from the sector should follow.


   ACKNOWLEDGMENTS
 
This work was supported by the Environmental Protection Agency (Ireland) under the Environmental Research Technological Development and Innovation Programme and was funded by the National Development Plan (2000-2006). We would also like to thank the farmers that participated in the survey.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 




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The SCI Journals Agronomy Journal Crop Science
Journal of Natural Resources
and Life Sciences Education		 Vadose Zone Journal
Soil Science Society of America Journal Journal of Plant Registrations The Plant Genome