Carbon footprint of farm systems from the Stratford and Waimate West Demonstration Farms

Transcription

1 Carbon footprint of farm systems from the Stratford and Waimate West Demonstration Farms June 2011 Carbon footprint analyses of Taranaki farm systems 21

2 Carbon footprint of farm systems from the Stratford and Waimate West Demonstration Farms MAF Sustainable Farming Fund Report for Part 3 SFF Project C08/007 June 2011 S F Ledgard 1, M Boyes 1 and G D Pitman 2 1 AgResearch Ruakura Research Centre, Hamilton 2 PGG Wrightson consultancy, Hawera DISCLAIMER: While all reasonable endeavour has been made to ensure the accuracy of the investigations and the information contained in this report, AgResearch expressly disclaims any and all liabilities contingent or otherwise that may arise from the use of the information. Carbon footprint analyses of Taranaki farm systems 1

3 Table of Contents 1. Executive Summary Introduction Methods Farm data Estimation of the carbon footprint of milk at the farm gate Estimation of GHG emissions using OVERSEER Results and Discussion Stratford Demonstration Farm Control farmlet systems Effect of molasses feeding Effect of increased stocking rate with off-farm feed and wintering-off Effect of on-farm crops Effect of increased stocking rate Effect of a high stocking rate with cows wintered off-farm Waimate West Demonstration Farm Effect of maize silage use Effect of high N fertiliser use and different stocking rates General Discussion Acknowledgements References Carbon footprint analyses of Taranaki farm systems 2

4 1. Executive Summary This report summarises an evaluation of the carbon footprint of milk (i.e. total greenhouse gas (GHG) emissions from all contributing on-farm and off-farm sources) for a range of farmlet studies from the Stratford and Waimate West Demonstration Farms. A Life Cycle Assessment approach was used that covered the cradle-to-farm-gate stage. The GHG emissions per hectare were strongly related to total milk production per hectare. However, a carbon footprint focuses on efficiency of GHG emissions i.e. total GHG emissions per kg of milksolids produced. The carbon footprint of the control farmlets averaged 10.7 and 10.8 kg CO 2 equivalents (CO 2 eq) per kg milksolids for the Stratford and Waimate West Demonstration Farms, respectively. A summary of the change in carbon footprint relative to the control farmlets from implementation of different farm inputs or practices is given in the table below. The largest reduction (-5%) in carbon footprint was in the molasses-supplemented farmlet, whereas the largest increases (+4 to +17%) in carbon footprint were associated with increased stocking rate or high N fertiliser use. There was little effect of wintering cows off farm or maize silage integration (whether grown on or off farm). kg CO 2 eq/kg milksolids Relative change Stratford Demonstration Farm 1. + Molasses % 2. Higher stocking + winter-off % 3. + cropping on-farm % 4. Increased stocking rate +0.8 to to +14.2% 5. Winter-off % Waimate West Demonstration Farm 6. Maize from off-farm % 7. Maize on-farm % 8. High N fertiliser rate +0.5 to to +17% The relative contributions from methane, N 2 O and CO 2 to the carbon footprint were 60-67%, 23-28% and 10-14%, respectively. This was dominated by animal feed intakerelated emissions of enteric and faecal methane and excreta N 2 O at about 80% of the total carbon footprint. Hot-spot analyses revealed that a key factor in reducing animal methane analyses was increasing per-cow milksolids production. Reduction in N 2 O emissions was associated with use of feeds with a low N concentration, whereas high N 2 O emissions were associated with high N fertiliser use. Carbon footprint analyses of Taranaki farm systems 3

5 Results were compared with analyses for on-farm greenhouse gas emissions calculated using the OVERSEER nutrient budget model. The OVERSEER model provides an estimate of specific on-farm emissions whereas the carbon footprint includes all off-farm practices and inputs that contribute to the total emissions in producing milk. Carbon footprint values were about 8% higher due in part to inclusion of all off-farm emissions (e.g. from replacement animals grazed off-farm and off-farm feed production). The largest differences between OVERSEER emissions and the carbon footprint were from practices involving brought-in feed sources and animals grazing off-farm. Thus, a carbon footprint approach is most appropriate for evaluating the total effect of alternative farm systems because it accounts for all sources that contribute to milk production for the whole farm system. Carbon footprint analyses of Taranaki farm systems 4

6 2. Introduction A previous New Zealand (NZ) carbon footprinting project examined the greenhouse gas (GHG) emissions throughout the life cycle of NZ milk processed into a range of products and delivered to overseas ports. That study illustrated that the cradle-to-farm-gate stage dominated GHG emissions at an average of 85% of the total for all stages examined (Hutchings and Ledgard, 2009). In that study, calculations for an average NZ dairy farm were determined using a weighted average for eight regions throughout NZ (Ledgard et al., 2008). Farm system practices can potentially influence the extent of GHG emissions and the carbon footprint for the cradle-to-farm-gate stage. Over several decades there have been a series of farmlet system trials carried out in Taranaki at the Stratford and Waimate West Demonstration Farms. A large amount of data was collected from these trials and this provides an ideal opportunity to carry our comparative carbon footprint analyses. A major benefit in studying systems based on farmlet trials is that it allows a comparison of different management practices or systems, while all other factors and inputs are held constant. Thus, it provides an accurate evaluation of system effects which cannot otherwise be studied using commercial dairy farms. A Sustainable Farming Fund (SFF) project is examining the environmental implications of the different Taranaki farm systems that have been evaluated. This report is part of that project and its aim is to present results from carbon footprint analyses of key farm systems evaluated on the Stratford and Waimate West Demonstration Farms. 3. Methods 3.1 Farm data Specific individual farmlet data from various farm system trials have been collected from the Stratford and Waimate West Demonstration Farms. This included data on animals and pasture as well as farm input information. The latter included information on electricity and fuel use as well as the source and level of other key farm inputs (such as various sources of brought-in feeds or fodder crops). Fertiliser and lime inputs were kept constant across farmlets and actual data was used for this analysis, whereas in some cases fertiliser requirements may be reduced from farm system changes e.g. brought-in feed results in nutrient inputs that can reduce fertiliser requirements. Carbon footprint analyses of Taranaki farm systems 5

7 Generic data was also obtained on off-farm practices e.g. typical characteristics and inputs for land where replacements were grazed off or where cows were wintered off. The farm systems used for this detailed evaluation were: Stratford Demonstration Farm: 1. Effect of molasses feeding comparison of farm systems 6 (control) and 7 (equivalent of 1423 kg DM/ha intake of molasses by cows) 2. Effect of increased stocking rate with off-farm silage/hay and wintering off comparison of farm systems 8 (control; 3.3 cows/ha) and 10 (4.0 cows/ha using 2.77 t DM/ha brought-in feed) 3. Effect of on-farm crops - comparison of farm systems 8 (control) and 11 (4% area in turnips and 7% in triticale for silage) 4. Effect of increased stocking rate - comparison of farm systems 13 (control; 3.2 cows/ha), 14 (stocking rate increased to 3.7 cows/ha) and 15 (stocking rate increased to 4.2 cows/ha) 5. Effect of high stocking rate and wintering-off - comparison of farm systems 18 (control; 3.2 cows/ha) and 19 (3.8 cows/ha and cows off-farm in winter) Waimate West Demonstration Farm: 6. Effect of high stocking rate with maize silage use - comparison of farm systems 6 (control; 3.8 cows/ha), 7 (5.0 cows/ha with 3.5 t DM intake/ha from brought-in maize silage and 686 kg DMI from brought-in pasture silage) and 8 (4.0 cows/ha with 23% of the on-farm area in maize silage production) 7. Effect of high N fertiliser use - comparison of farm systems 14 (control; 3.6 cows/ha and 101 kg fertiliser-n/ha/yr), 15 (3.8 cows/ha and 247 kg fertiliser- N/ha/yr) and 16 (4.2 cows/ha and 247 kg fertiliser-n/ha/yr). 3.2 Estimation of the carbon footprint of milk at the farm gate A version of the carbon footprint model from the previous study by Ledgard et al. (2008) was used to calculate the carbon footprint of milk covering the cradle-to-farm-gate stage. This model is essentially the same as in the previous model but has been updated for the latest IPCC factors for effluent and N 2 O associated with cropping. The model was further developed to account for detailed information on productivity and inputs for land used for off-farm grazing of dairy replacements and for wintering of dairy cows relevant to Taranaki. Separate LCAs were prepared for typical Taranaki crops for maize silage, turnips and triticale for use in the whole-system analyses. Additionally, an LCA was developed for molasses. Carbon footprint analyses of Taranaki farm systems 6

8 Methane emissions (enteric, faecal and farm dairy effluent emissions) in the carbon footprint model are calculated using an energy based model which is essentially the same as that used for the NZ GHG Inventory. It is based on the Australian feeding standards but includes allowance for a range of management practices not specifically included in the NZ GHG Inventory. Nitrous oxide (N 2 O) emissions from animal excreta utilise estimates of feed intake as for methane and otherwise use all activity and emission factors from the NZ GHG Inventory (MfE 2007). The carbon footprint model includes CO 2 from all sources and it includes GHG emissions (methane, N 2 O and CO 2 ) from all off-farm sources that relate to milksolids production e.g. from replacement animals, off-farm cow grazing, off-farm supplementary feed sources. In all cases, methane, N 2 O and CO 2 emissions are expressed in CO 2 -equivalents (CO 2 eq) according to the latest GWP factors (IPCC 2007), in keeping with all other NZ carbon footprinting studies. All results presented for the carbon footprint refer to unallocated values (i.e. no allocation of GHG emissions between milk and meat (this is discussed in the General Discussion section). 3.3 Estimation of GHG emissions using OVERSEER The OVERSEER nutrient budgets model (version 5.4.4; hereafter called OVERSEER) was used to calculate GHG emissions for each farm in an earlier phase of this project (C08/007) and has been reported previously. The use of OVERSEER results in GHG emissions calculated within the farm boundary. Thus, it does not account for emissions associated with animals grazed off-farm e.g. replacement animals or cows grazed off over winter, and only partly accounts for other off-farm inputs such as brought-in feed. The Global Warming Potential (GWP) factors for methane and N 2 O in CO 2 -equivalents are the same as that used in the NZ GHG Inventory and based on earlier IPCC factors i.e. 21 and 310, respectively. 4. Results and Discussion For each of the Demonstration Farm sites, data are presented on the carbon footprint in kg CO 2 eq/kg milksolids for the cradle-to-farm-gate stage. In all cases, this refers to the total GHG emissions and there has been no allocation of emissions to milk and meat coproducts i.e. all emissions are allocated to milk. In the NZ dairy carbon footprint study (Ledgard et al. 2008), results for the average NZ dairy farm were allocated, with 86% to milk and 14% to meat, using a biophysical allocation approach. This project is focussed largely on the effects of different farm system practices on the carbon footprint and the use of allocation between milk and meat would have negligible effect on relative results between the different farm systems. Carbon footprint analyses of Taranaki farm systems 7

9 Results presented in the following sections have had emissions from refrigerant loss from milk vats excluded, for simplicity. In practice, these typically equate to approximately 50 kg CO 2 eq/ha/year and therefore represent less than 0.5% of the carbon footprint. Additionally, it will be unaffected by farmlet system. 4.1 Stratford Demonstration Farm Control farmlet systems Each farm system comparison included a control farmlet. Tables 1 and 2 present results from the different control farmlet systems for GHG emissions per hectare and per kg milksolids, respectively. The variation between trials reflects differences between years. This can be related predominantly to effects on annual milksolids production, which averaged 1002, 1059, 1091 and 1101 kg/ha/year for control farmlet trial numbers 6, 8, 13 and 18, respectively. These represent differences in years of trial conduct at 2005/06, 2001/ /05, 1998/ /01 and 1992/ /95, respectively. Table 1: Greenhouse gas emissions (kg CO 2 eq/ha/year) from different input sources for the Control farmlets at the Stratford Demonstration farm Control farmlet trial number Methane: enteric dung FDE N 2 O: excreta 1, fertiliser CO 2 : electricity fuel brought-in feed agri-chemicals lime P,K,S fertilisers N fertiliser TOTAL Carbon footprint analyses of Taranaki farm systems 8

10 Of the various sources contributing to the total GHG emissions, enteric methane (from cow rumen fermentation of feeds) was the largest at 61-64% (Table 1). Methane emissions from dung and FDE were relatively small at 0.6% and 2.2%, respectively. Nitrous oxide emissions (direct and indirect sources) from excreta and N fertiliser were 17-18% and 5-8%, respectively. Carbon dioxide emissions from electricity, fuel use, agri-chemicals, lime, non-n-fertilisers and N fertilisers averaged 1.3%, 0.9% <0.1%, 1.1%, 2.4% and 5.0%, respectively. Further analysis of this data indicated that the off-farm component associated with rearing of the replacement heifers contributed approximately 11% of the total carbon footprint (data not presented). Table 2: Carbon footprint of milk (kg CO 2 eq/kg milksolids) produced from the Control farmlets at the Stratford Demonstration farm Control farmlet trial number Methane: enteric dung FDE N 2 O: excreta fertiliser CO 2 : electricity fuel brought-in feed agri-chemicals lime P,K,S fertilisers N fertiliser TOTAL Carbon footprint analyses of Taranaki farm systems 9

11 4.1.2 Effect of molasses feeding Molasses feeding resulted in a 14% increase in milksolids production per cow and per hectare. Total GHG emissions were 8.5% higher for the molasses farmlet on a per hectare basis (Table 3). Methane emissions constituted 63% of the total, whereas N 2 O made up 23-25% and CO %. Table 3: Total greenhouse gas emissions (kg CO 2 eq/ha/year) for control and molasses supplementation farmlet systems at the Stratford Demonstration Farm. Farmlet Trial no. Methane N 2 O CO 2 Total Control 6 7,071 2,812 1,297 11,180 +Molasses 7 7,673 2,753 1,709 12,135 On a per kg milksolids basis, the carbon footprint of milk was 5.1% lower for the molasses farmlet than the control farmlet (Figure 1). There was a 14% lower N 2 O contribution from the molasses farmlet due in part to the low N content of molasses making little contribution to N excretion and the associated N 2 O emissions. The methane contribution was 5% lower from the molasses farmlet, whereas the CO 2 contribution was 15% higher. The latter was due to CO 2 emissions associated with the production of molasses (assumed to be in Australia) and its transportation to NZ and to the farm. Emissions associated with molasses production were based on several international LCA studies of sugar production which included molasses as a co-product. A breakdown of the relative contributors to CO 2 emissions are given in Figure 2. This shows the specific contribution from molasses production and transportation at 3.2% of the total carbon footprint for the molasses farmlet. The relative contributions from the other sources were similar for both farmlets and were dominated by N fertiliser, which is mainly due to the manufacturing stage (Ledgard et al. 2011). Fertiliser containing P, K and S was the next largest contributor to CO 2 emissions at % of the total carbon footprint, due mainly to emissions from transportation of raw materials to NZ (Ledgard et al. 2011). Fuel use on farm and lime each contributed about 1% of the total carbon footprint, while electricity contributed %. Carbon footprint analyses of Taranaki farm systems 10

12 Figure 1: Carbon footprint of milk at the farm-gate (kg CO 2 eq/kg milksolids) for control and molasses supplementation farmlet systems at the Stratford Demonstration Farm. 12 Carbon footprint (kg CO 2 eq/kg milksolids) CO 2 N 2 O Methane 0 Control Molasses Figure 2: Contribution of various input sources to CO 2 emissions from the control and molasses supplementation farmlet systems at the Stratford Demonstration Farm. 1.5 Molasses CO 2 emissions (kg CO 2 eq/kg milksolids) Electricity Fuel Lime PKS fertiliser N fertiliser 0.0 Control Molasses Carbon footprint analyses of Taranaki farm systems 11

13 4.1.3 Effect of increased stocking rate with off-farm feed and winteringoff Increased stocking rate (from 3.3 to 4.0 cows/ha) through the use of brought-in pasture silage and hay and wintering cows off the farmlet resulted in a 23% increase in milksolids production per hectare and similar per-cow milk production. Similarly, total GHG emissions were 24% higher on a per hectare basis (Table 4). Methane emissions constituted 63-64% of the total, whereas N 2 O made up 24-26% and CO %. Table 4: Total greenhouse gas emissions (kg CO 2 eq/ha/year) for a control farmlet and a farmlet with increased stocking rate, brought-in off-farm feed and cow wintering-off at the Stratford Demonstration Farm. Farmlet Trial no. Methane N 2 O CO 2 Total Control 8 7,396 2,969 1,304 11,669 Increased stocking 10 9,209 3,528 1,721 14,458 On a per kg milksolids basis, the carbon footprint of milk was similar for both farmlets, being 0.3% lower for the higher stocking rate farmlet than the control farmlet (Figure 3). There was a 4% lower N 2 O contribution from the higher stocking rate farmlet due in part to the lower N content of the brought-in silage and hay resulting in lower N excretion per kg milksolids and lower associated N 2 O emissions. There was no difference between farmlets in methane contribution. However, the CO 2 contribution was 7% higher from the higher stocking rate farmlet. A breakdown of the relative contributors to CO 2 emissions are given in Figure 4. This shows a similar relative contribution from the various sources for both farmlets, with the largest difference between farmlets being 72% higher emissions from fuel use. The latter was due to extra fuel required for production and transport of silage and hay as well as the trucking of cows to and from the area of off-farm wintering. As discussed in the last section, the CO 2 emissions were dominated by fertiliser use (including on-farm and off-farm use) with similar smaller contributions associated with the use of lime, fuel and electricity. Carbon footprint analyses of Taranaki farm systems 12

14 Figure 3: Carbon footprint of milk at the farm-gate (kg CO 2 eq/kg milksolids) for a control farmlet and a high stocking rate farmlet with brought-in silage and hay and cow wintering-off at the Stratford Demonstration Farm CO 2 Carbon footprint (kg CO 2 eq/kg milksolids) N 2 O Methane 2 0 Control Higher stocking rate Figure 4: Contribution of various input sources to CO 2 emissions from a control farmlet and a high stocking rate farmlet with brought-in silage and hay and cow wintering-off at the Stratford Demonstration Farm. 1.5 CO 2 emissions (kg CO 2 eq/kg milksolids) Electricity Fuel Lime PKS fertiliser N fertiliser 0.0 Control Higher stocking rate Carbon footprint analyses of Taranaki farm systems 13

15 4.1.4 Effect of on-farm crops Integration of on-farm forage crops of turnips and triticale for silage and no change in stocking rate resulted in a 4.7% increase in milksolids production per cow and per hectare. Total GHG emissions were slightly higher in the cropped farmlet by 1.2% on a per hectare basis (Table 5). Methane emissions constituted 63-64% of the total, whereas N 2 O made up 25-26% and CO 2 11%. Table 5: Total greenhouse gas emissions (kg CO 2 eq/ha/year) for a control farmlet and a farmlet with on-farm forage crop production at the Stratford Demonstration Farm. Farmlet Trial no. Methane N 2 O CO 2 Total Control 8 7,396 2,969 1,304 11,669 + on-farm crops 11 7,535 2,922 1,349 11,806 On a per kg milksolids basis, the carbon footprint of milk was 3.3% lower for the cropped farmlet than the control farmlet (Figure 5). This was due in part to a 6% lower N 2 O contribution because of the lower N content of the turnips and triticale silage resulting in lower N excretion per kg milksolids and lower associated N 2 O emissions. The methane contribution was also 3% lower, whereas there was little difference in the CO 2 contribution in total or between the various contributors (Figure 6). Figure 5: Carbon footprint of milk at the farm-gate (kg CO 2 eq/kg milksolids) for a control farmlet and a farmlet with on-farm crop production at the Stratford Demonstration Farm. 12 Carbon footprint (kg CO 2 eq/kg milksolids) CO 2 N 2 O Methane 0 Control + Crops Carbon footprint analyses of Taranaki farm systems 14

16 Figure 6: Contribution of various input sources to CO 2 emissions from a control farmlet and a farmlet with on-farm crop production at the Stratford Demonstration Farm. 1.5 CO 2 emissions (kg CO 2 eq/kg milksolids) Electricity Fuel Lime PKS fertiliser N fertiliser 0.0 Control + Crops Effect of increased stocking rate Increasing stocking rate from 3.2 cows/ha in the control farmlet to 3.7 and 4.2 cows/ha had little effects on milksolids production per hectare, averaging 1091, 1066 and 1071 kg milksolids/ha/year, respectively. However, milksolids production per cow decreased with increasing stocking rate at 341, 288 and 255 kg/cow, respectively. Total GHG emissions per hectare increased by 5 and 12% with 3.7 and 4.2 cows/ha, respectively (Table 5). Methane, N 2 O and CO 2 emissions constituted 65, 25 and 10% of the total emissions, respectively, across all farmlets. Table 5: Total greenhouse gas emissions (kg CO 2 eq/ha/year) for three Stratford Demonstration Farm systems evaluating effects of increasing stocking rate. Farmlet Trial no. Methane N 2 O CO 2 Total Control (3.2 cows/ha) 13 7,397 2,830 1,213 11, cows/ha 14 7,826 2,989 1,195 12, cows/ha 15 8,394 3,201 1,226 12,821 Carbon footprint analyses of Taranaki farm systems 15

17 On a per kg milksolids basis, the carbon footprint of milk increased by 7.5 and 14% with the increase in stocking rate to 3.7 and 4.2 cows/ha, respectively (Figure 7). This was mainly associated with a decrease in milksolids production per cow resulting in relatively higher methane and animal excreta N 2 O emissions per kg milksolids. In contrast, the CO 2 emissions per kg milksolids were similar across all farmlets and showed a similar relative contribution from the various sources (data not shown, but similar to that for other control farmlets presented earlier). Figure 7: Carbon footprint of milk at the farm-gate (kg CO 2 eq/kg milksolids) for three farmlets with increasing stocking rate at the Stratford Demonstration Farm Carbon footprint (kg CO 2 eq/kg milksolids) CO 2 N 2 O Methane Control cows/ha cows/ha Effect of a high stocking rate with cows wintered off-farm Increasing stocking rate from 3.2 cows/ha in the control farmlet to 3.8 cows/ha with the cows wintered off-farm resulted in an increase in milksolids production per hectare by 9.1%. However, milksolids production per cow decreased by 8%. Total GHG emissions per hectare increased by 11.6% in the higher stocked farmlet compared to the control farmlet (Table 6). Methane emissions constituted 66-67% of the total, whereas N 2 O made up 23% and CO %. Carbon footprint analyses of Taranaki farm systems 16

18 Table 6: Total greenhouse gas emissions (kg CO 2 eq/ha/year) from a control farmlet and a farmlet with increased stocking rate and cows wintered-off at the Stratford Demonstration Farm. Farmlet Trial no. Methane N 2 O CO 2 Total Control (3.2 cows/ha) 18 7,381 2,603 1,180 11, cows/ha + winter-off 19 8,346 2,927 1,187 12,460 On a per kg milksolids basis, the carbon footprint of milk increased by 2% with the increase in stocking rate compared to the control farmlet (Figure 8). Methane and N 2 O emissions per kg milksolids increased by 3-4% with increased stocking rate. However, CO 2 emissions per kg milksolids decreased by 8% because less pasture silage was made on-farm and the fuel saving from this more than countered the fuel with cow transport for wintering-off. The relative contribution from the various input sources was slightly lower for the higher stocked farmlet in all cases, except for the imported barley where it was much lower because of the lower rate used compared to the control farmlet (Figure 9). Figure 8: Carbon footprint of milk at the farm-gate (kg CO 2 eq/kg milksolids) for a control farmlet and a farmlet with increased stocking rate and cows wintered off-farm at the Stratford Demonstration Farm. 12 Carbon footprint (kg CO 2 eq/kg milksolids) Control 3.8 cows/ha 3.2 cows/ha + winter-off CO 2 N 2 O Methane Carbon footprint analyses of Taranaki farm systems 17

19 Figure 9: Contribution of various input sources to CO 2 emissions from a control farmlet and a farmlet with increased stocking rate and cows wintered off-farm at the Stratford Demonstration Farm. 1.5 CO 2 emissions (kg CO 2 eq/kg milksolids) Control 3.8 cows/ha 3.2 cows/ha +winter-off Imported barley Electricity Fuel Lime PKS fertiliser N fertiliser 4.2 Waimate West Demonstration Farm Effect of maize silage use Increasing stocking rate from 3.8 cows/ha in the control farmlet to 5 cows/ha with brought-in maize and 4 cows/ha with on-farm maize resulted in average milksolids production per hectare of 1170, 1560 and 1240 kg milksolids/ha/year, respectively. Milksolids production per cow was similar across all farmlets at kg/cow. Total GHG emissions per hectare increased by 31 and 4% in the 5 and 4 cows/ha farmlets compared to the control farmlet, respectively (Table 7). Methane, N 2 O and CO 2 emissions constituted 62-65, and 11-12% of the total emissions, respectively, across all farmlets. Table 7: Total greenhouse gas emissions (kg CO 2 eq/ha/year) for a control farmlet and two farmlets with maize silage integration derived from off-farm or on-farm production at the Waimate West Demonstration Farm. Farmlet Trial no. Methane N 2 O CO 2 Total Control (3.8 cows/ha) 6 8,108 3,456 1,458 13,022 5 cows/ha; brought-in maize 7 10,863 4,122 2,037 17,022 4 cows/ha; on-farm maize 8 8,776 3,166 1,556 13,498 Carbon footprint analyses of Taranaki farm systems 18

20 On a per kg milksolids basis, the carbon footprint of milk was 2% lower in both maizesupplemented farmlets compared to the control (Figure 10). The N 2 O emissions per kg milksolids were 11 and 14% lower in the 5 and 4 cows/ha farmlets compared to the control farmlet, respectively. This was mainly due to the low N concentration in maize silage compared to pasture resulting in less N excreted per kg milksolids and less excreta N 2 O emissions. In contrast, methane emissions per kg milksolids were similar across farmlets whereas the CO 2 emissions per kg milksolids increased by up to 5% for the brought-in maize farmlet. A breakdown of the CO 2 emissions (Figure 11) showed a similar relative contribution from the various sources for all farmlets, with the largest difference between farmlets being 65% higher emissions from fuel use in the brought-in maize farmlet. The latter was due to extra fuel required for production, harvesting and transport of maize silage. Figure 10: Carbon footprint of milk at the farm-gate (kg CO 2 eq/kg milksolids) for a control farmlet and farmlets with increased stocking rate using brought-in or on-farm maize silage at the Waimate West Demonstration Farm. 12 Carbon footprint (kg CO 2 eq/kg milksolids) Control 5 cows/ha 4 cows/ha 3.8 cows/ha brought-in maize on-farm maize CO 2 N 2 O Methane Carbon footprint analyses of Taranaki farm systems 19

21 Figure 11: Contribution of various input sources to CO 2 emissions from a control farmlet and farmlets with increased stocking rate using brought-in or on-farm maize silage at the Waimate West Demonstration Farm. 1.5 CO 2 emissions (kg CO 2 eq/kg milksolids) Electricity Fuel Lime PKS fertiliser N fertiliser 0.0 Control 5 cows/ha 4 cows/ha 3.8 cows/ha brought-in on-farm maize maize Effect of high N fertiliser use and different stocking rates Increasing stocking rate from 3.6 cows/ha in the control farmlet to 3.8 or 4.2 cows/ha with high N fertiliser use (247 kg N/ha/year compared to 101 kg N/ha/year in the control farmlet) resulted in average milksolids production per hectare of 1102, 1288 and 1138 kg milksolids/ha/year, respectively. The corresponding milksolids production per cow was 306, 339 and 271 kg/cow, respectively. Total GHG emissions per hectare increased by 22 and 21% in the 3.8 and 4.2 cows/ha high-n farmlets compared to the control farmlet, respectively (Table 8). Methane, N 2 O and CO 2 emissions constituted 60-66, and 10-13% of the total emissions, respectively, across all farmlets. Table 8: Total greenhouse gas emissions (kg CO 2 eq/ha/year) for a control farmlet and two farmlets with maize silage integration derived from off-farm or on-farm production at the Waimate West Demonstration Farm. Farmlet Trial no. Methane N 2 O CO 2 Total Control (3.6 cows/ha; 101 kg N/ha/year) 14 7,638 2,841 1,105 11, cows/ha; 247 kg N/ha/year 15 8,530 3,872 1,736 14, cows/ha; 247 kg N/ha/year 16 8,341 3,867 1,751 13,959 Carbon footprint analyses of Taranaki farm systems 20

22 On a per kg milksolids basis, the carbon footprint of milk was 4-17% higher in the high N farmlets compared to the control lower-n farmlet (Figure 12). The N 2 O emissions per kg milksolids were 17 and 32% higher in the high-n farmlets compared to the control farmlet, respectively. This was due to the direct and indirect emissions associated with N fertiliser use and effects of differences in N excreted /kg milksolids with stocking rate. In contrast, methane emissions per kg milksolids were 5% above or below the control, whereas the CO 2 emissions per kg milksolids increased by 34-53% compared to the control farmlet. A breakdown of the CO 2 emissions (Figure 13) showed a similar relative contribution from the various sources for all farmlets, except for the N fertiliser contribution which was % higher for the high-n farmlets. The latter was due to the high energy use and related CO 2 emissions associated with manufacturing of N fertiliser (Ledgard et al. 2011). Figure 12: Carbon footprint of milk at the farm-gate (kg CO 2 eq/kg milksolids) for a control farmlet (receiving 101 kg fertiliser-n/ha/year) and high N (247 kg fertiliser- N/ha/year) farmlets at 3.8 or 4.2 cows/ha at the Waimate West Demonstration Farm. Carbon footprint (kg CO 2 eq/kg milksolids) CO 2 N 2 O Methane Control 101N 247N 247N 3.6 cows/ha 3.8 cows/ha 4.2 cows/ha Carbon footprint analyses of Taranaki farm systems 21

23 Figure 13: Contribution of various input sources to CO 2 emissions from a control farmlet (receiving 101 kg fertiliser-n/ha/year) and high N (247 kg fertiliser-n/ha/year) farmlets at 3.8 or 4.2 cows/ha at the Waimate West Demonstration Farm. CO 2 emissions (kg CO 2 eq/kg milksolids) Electricity Fuel Lime PKS fertiliser N fertiliser 0.0 Control 101N 247N 247N 3.6 cows/ha 3.8 cows/ha 4.2 cows/ha 5. General Discussion The GHG emissions per hectare were strongly related to total milk production per hectare. However, a carbon footprint focuses on the efficiency of GHG emissions i.e. total GHG emissions per kg of milksolids produced. A summary of the relative effects of the different farmlet systems compared to control farmlets showed little effect on carbon footprint from cows wintering off farm or maize silage integration (whether grown on or off farm) (Table 9). The largest reduction (-5%) in carbon footprint was in the molasses-supplemented farmlet, whereas the largest increases (+4 to +17%) in carbon footprint were associated with increased stocking rate or high N fertiliser use. Carbon footprint analyses of Taranaki farm systems 22

24 Table 9. Summary of the effects of different farm system changes on the carbon footprint of milk at the farm-gate relative to a standard control farmlet system. kg CO 2 eq/kg milksolids Relative change Stratford Demonstration Farm 1. + Molasses % 2. Higher stocking + winter-off % 3. + cropping on-farm % 4. Increased stocking rate +0.8 to to +14.2% 5. Winter-off % Waimate West Demonstration Farm 6. Maize from off-farm % 7. Maize on-farm % 8. High N fertiliser rate +0.5 to to +17% The carbon footprint analyses across the range of farmlet systems showed the significance of non-co 2 GHGs, with the relative contributions from methane, N 2 O and CO 2 at 60-67%, 23-28% and 10-14%, respectively. This was dominated by animal feed intake-related emissions of enteric and faecal methane and excreta N 2 O at about 80% of the total carbon footprint. Hot-spot analyses revealed that a key factor in reducing animal methane analyses was increasing per-cow milksolids production. Reduction in N 2 O emissions was associated with use of feeds with a low N concentration, whereas high N 2 O emissions were associated with high N fertiliser use. Comparison of GHG emissions associated with the carbon footprint analyses versus OVERSEER analyses showed that estimates were higher by kg CO 2 eq/kg milksolids for the carbon footprint (Figure 14). The carbon footprint analysis used a more recent GWP factor for methane of 25 CO 2 -eq/kg compared to 21 CO 2 -eq/kg in OVERSEER, which will also tend to have resulted in higher overall estimates. However, higher total GHG emission values are expected from carbon footprint analyses because they include GHG emissions associated with the dairy replacement animals grazed off farm (at about 11% of the total carbon footprint) as well as a more complete analysis of some external inputs to the farm e.g. brought-in feeds. Thus, the difference between carbon footprint and OVERSEER estimates was greatest in treatments involving cow wintering off-farm and maize silage sourced from off-farm. Carbon footprint analyses of Taranaki farm systems 23

25 Figure 14: Comparison of total GHG emissions estimated using carbon footprint or OVERSEER analyses across all Stratford and Waimate West Demonstration Farm systems. 13 1:1 Carbon footprint OVERSEER 6. Acknowledgements We thank all the Taranaki farmers who contributed time and their farm data for use in this project. We also thank Joe Clough for his role in overseeing the Waimate Demonstration Farm and providing data for use in this project. 7. References Hutchings J and Ledgard S Drivers, methods, results and challenges Fonterra carbon footprint study. Conference on carbon footprinting of products and services. University of Bath, England. IPCC, Fourth Assessment Report, Climate Change IN PRESS, C U (Ed.). Cambridge, UK. Ledgard S F, Basset-Mens C, Boyes M and Clark H, Carbon footprint measurement - Milestone 6: Carbon footprint for a range of milk suppliers in New Zealand. Report to Fonterra. AgResearch, Hamilton. 41p. Carbon footprint analyses of Taranaki farm systems 24

26 Ledgard S F, Boyes M and Brentrup F Life cycle assessment of local and imported fertilisers used on New Zealand farms. In: Adding to the knowledge base for the nutrient manager. (Eds Currie LD and Christensen CL), Occasional Report No. 24, Fertilizer and Lime Research Centre, Massey University, Palmerston North, New Zealand. (in press). MfE, New Zealand s Greenhouse Gas Inventory The National Inventory Report and Common Reporting Format Tables. Ministry for the Environment, Wellington, New Zealand. Wheeler D M, Ledgard S F and DeKlein C A M Using the OVERSEER nutrient budget model to estimate on-farm greenhouse gas emissions. Australian Journal of Experimental Agriculture 48(2): Carbon footprint analyses of Taranaki farm systems 25