4 Acidification of slurry

Life Cycle Assessment of Slurry Management Technologies

The life cycle assessment in this chapter is performed in order to answer the question: “What are the environmental benefits and disadvantages of acidification of slurry in the Infarm NH4+ plant compared to the reference scenario for slurry?”.

This is done by comparing the environmental impacts from the scenario for acidification of slurry in the Infarm NH4+ plant to the environmental impacts from the reference scenario in chapter 3. The Life Cycle Inventory data and the acidification scenario are described in Annex B.

The environmental impacts and conclusions in this chapter build to a great extent on data and information delivered by the producer of the technology, Infarm, or on data made for Infarm. The conclusions rely on this information, and the authors have not had the possibility of verifying the data.

4.1 System description

In the Infarm NH4+ Acidification plant, pig or cattle slurry is acidified by the addition of sulphuric acid (H₂SO₄). The sulphuric acid reduces the pH and the chemical equilibrium between ammonium (NH₄⁺) and ammonia (NH₃) is changed which means that it is primarily in the form of ammonium (NH₄⁺). As only ammonia (NH₃) evaporates, the pH of the slurry is a determining factor for the amount of nitrogen / ammonia that volatilize in the housing system, during storage and during application to fields. Moreover, acidification of the slurry has significance for other factors. For example the use of sulphuric acid for the acidification might be an advantage as it adds sulphur to the field which can have a fertiliser effect.

The system for acidification of slurry is shown in figure 4.1. The numbers in the figure refer to the number of the process (which appears in the figures with the results) and to the corresponding numbers of the process description in Annex B.

For fully understanding of the system for acidification, Annex B should be read before reading the results in section 4.2 below.

Figure 4.1. Flow diagram for the scenario for acidification of slurry.

Click here to see Figure 4.1

4.2 Results of the Impact Assessment

4.2.1 Overall results of the comparison

In figure 4.2, the environmental impacts from Acidification of pig slurry in an Infarm NH4+ plant has been compared to the environmental impacts from the reference system described in chapter 3. Figure 4.3 shows the results for dairy cow slurry.

The results are discussed in the following sections.

Figure 4.2. Environmental impacts for the system with acidification of slurry in an infarm NH4+ plant compared to the reference system (both based on soil type JB3) – pig slurry.

Click here to see Figure 4.2

Figure 4.3. Environmental impacts for the system with acidification of slurry in an infarm NH4+ plant compared to the reference system (both based on soil type JB3) – dairy cow slurry.

Click here to see Figure 4.3

4.2.2 Sensitivity analysis

Sensitivity analysis has been carried out for a number of possible variations of the acidification scenario and uncertainties related to the data. Some of the results of the sensitivity analyses are shown in figures in this section, as the influence are complex. For simple variations, the results of the sensitivity analyses are described in the text under each impact category in the following sections.

In this section, the results of sensitivity analysis are shown for:

The difference between soil type JB3 and JB6.
Uncertainty on the in-housing CH₄ emissions (based on IPCC data) and the consequence for the comparison.
Uncertainty on the reduction of the in-housing CH₄ by acidification of the slurry.
Uncertainty on the CH₄ emissions from storage.
The assumption that a future law might require that the farmers reduce the consumption of mineral N fertiliser in correspondence with the extra amount of N that the acidified slurry contains compared to non-treated slurry.

The significance of applying a 10 years horizon or 100 year horizon is shown in figure 4.2 and 4.3.

As can be seen from figure 4.4, the difference between soil type JB3 and JB6 has no significance for the overall conclusions. The same applies for dairy cow slurry. Accordingly it has been decided not to include the figures for dairy cow slurry.

The results of the sensitivity analyses are discussed under each impact category in the following sections.

It has not been possible to perform an extensive sensitivity analysis for the variations in slurry composition. However, it can be stated, that for the comparison between the system with acidified slurry and the reference system, the actual content of N and C in itself is not very important, as the emissions for acidified slurry is calculated relative to the reference slurry (in % of the reference slurry). Neither does the amount of water (or rather – the lack of water in the Danish Norm data) influence the overall results of the comparison. However, the C:N ratio is very significant for the dynamics of N after application, strongly influencing the fraction of N going to respectively the soil organic pool (higher with high C:N ratio), N harvest (lower with higher C:N ratio) and leaching (normally lower with higher C:N ratio).

Again, as the acidified slurry is calculated relative to the untreated slurry, it is assumed that for most slurry types, it would not change the overall conclusions.

Figure 4.4. Sensitivity Analysis: Difference between soil type JB3 and JB6. Environmental impacts for the system with acidification of slurry in an infarm NH4+ plant compared to the reference system – pig slurry.

Click here to see Figure 4.4

Figure 4.5. Sensitivity Analysis: Consequences of choice of IPCC data for in-house CH4 emissions for a retention time > 1 month compared to data for a retention time < 1 month. Environmental impacts for the system with acidification of slurry in an infarm NH4+ plant compared to the reference system (both based on soil type JB3, 10 year time horizon for soil processes) – pig slurry.

Click here to see Figure 4.5

Figure 4.6. Sensitivity Analysis: Consequences of changes in the reduction of the in-house CH₄ emissions caused by the acidification of slurry. Environmental impacts for the system with acidification of slurry in an infarm NH4+ plant compared to the reference system (both based on soil type JB3, 10 year time horizon for soil processes) – pig slurry.

Click here to see Figure 4.6

Figure 4.7. Sensitivity Analysis: Consequences of changes in the reduction of the CH₄ emissions from storage caused by the acidification of slurry. Environmental impacts for the system with acidification of slurry in an infarm NH4+ plant compared to the reference system (both based on soil type JB3, 10 year time horizon for soil processes) – pig slurry.

Click here to see Figure 4.7

Figure 4.8. Sensitivity Analysis: Consequences of changing the law so it demands that the farmer reduces the consumption of mineral N fertiliser in correspondence with the extra amount of N that the acidified slurry contains compared to non-treated slurry. Environmental impacts for the system with acidification of slurry in an infarm NH4+ plant compared to the reference system (both based on soil type JB3, 10 year time horizon for soil processes) – pig slurry.

Click here to see Figure 4.8

Figure 4.9. Sensitivity Analysis: Consequences of changing the law so it demands that the farmer reduce the consumption of mineral N fertiliser in correspondence with the extra amount of N that the acidified slurry contains compared to non-treated slurry. Environmental impacts for the system with acidification of slurry in an infarm NH4+ plant compared to the reference system (both based on soil type JB3, 10 year time horizon for soil processes) – dairy cow slurry.

Click here to see Figure 4.9

4.2.3 Global warming

In figure 4.2 and 4.3 it is seen that the “acidification scenario” has a lower contribution to global warming. The lower contribution is due to a decrease of the CH₄ emissions in the housing units and during the outdoor storage (which probably is caused by microbial activity being inhibited to some extent at low pH). However, it should be emphasised that the decrease is based on a few laboratory measurements under laboratory conditions, rather than “real outdoor conditions”, and the magnitude of the relative decrease should be interpreted with care. The decrease could be higher: However, the decrease could also be lower, as described in Annex B.

As mentioned in Annex A, the uncertainty on the CH₄ emissions is high, and this has influence on the comparison. As mentioned, the IPCC (2006) model use a very rough partitioning in “storage < 1 month” and “storage > 1 month”. The emission factors (in kg CH₄ per kg VS) is 5.67 times higher for “storage > 1 month” than for “storage > 1 month” which is an unrealistic jump. In this study, the high emission factor from IPCC (2006) has been used as a conservative estimate. If the lower emission factor was used, the contribution from the housing units would be significantly smaller, and so would the relative reduction by the acidification of the slurry compared to the total contribution from the entire system. The sensitivity analysis for this is shown in figure 4.5. The uncertainty has significance for the absolute reduction, but less significance for the relative reduction. The choice of the higher IPCC value might overestimate the absolute net reduction by the acidification scenario in CO₂-equivalents (for global warming). This consideration is included in table 4.1 and 4.2 for the net reductions in section 4.3

The data on the factor by which acidification of slurry reduces the in-house CH₄ emissions are based on very few measurements and the uncertainty is rather high. The uncertainty on the reduction factor affects the contribution to global warming and to photochemical ozone formation. Sensitivity analyses have been carried out with a reduction factor of 7% and 80% and the results are shown in figure 4.6. Preliminary measurements indicate that the reduction is probably rather high, as the measurements on the reductions include CH₄ emissions from “enteric fermentation” from dairy cows. When comparing data for the CH₄ emissions from ”enteric fermentation” from dairy cows (Nielsen et al, 2008a, table 6.6) with the CH₄ emissions from “manure management” (Nielsen et al, 2008a, table 6.12) it can be seen that the CH₄ from the slurry is in the order of 13% of the total CH₄ emissions from dairy cows. As the CH₄ from the enteric fermentation is not included in this study (as slurry management does not influence this), it is likely, that the CH₄ reductions from the slurry in the housing units could be rather high. As no data have been available, a rough estimate has been used for the sensitivity analysis, assuming a reduction of 80% of the CH₄ emissions from the slurry. However, scientific research is needed in order to evaluate the reduction factor. From figure 4.6 it can be seen that the influence on the total contribution to global warming and photochemical ozone formation is noteworthy.

The data for the reduction of CH₄ emissions from storage of the slurry are also rather uncertain, as described in Annex B (section B.5). For the “base case” acidification scenario, it is assumed that acidification reduces the CH₄ emissions by 60%. Sensitivity analysis has been carried out for a reduction of 30% and 90% in figure 4.7. From figure 4.7 it is obvious, that improved scientific data is needed for the documentation of the CH₄ reductions from acidification, as it is important for the overall reductions.

As mentioned in Annex B, it is assumed that the N₂O emissions from application of acidified slurry to the field are at the same level as untreated slurry (i.e. the emission factor for N₂O per kg N). It is, however, an assumption without any reference to measurements or testing. It is likely that the N₂O emissions will be changed for acidified slurry, however, there is no indication of whether the emission factor is higher or lower than for untreated slurry. Scientific research is needed in the area.

The conclusion on global warming is, that preliminary results indicate a reduced production of CH₄ during storage of acidified slurry, but the magnitude of this is uncertain as the results build on a few measurements (“Der foreligger kun et særdeles spinkelt grundlag for at vurdere virkningen af forsuring på dannelsen af drivhusgasser”) as emphasized in the upcoming BAT-documentation (which have been sent for public hearing until 15 April 2009 (revised version of 23 March 2009 for pig slurry and revised version of 17 March 2009) (BAT (2009a) and BAT (2009b)). The reduction of global warming reduction could be counteracted by an increase from field emissions if the N₂O emissions from the application of acidified slurry are somewhat higher than N₂O from untreated slurry.

The acidification of slurry has a potential of reducing the contribution to global warming significantly compared to the reference system. As can be seen in table 4.1 and 4.2 in section 4.3, the reduction is probably in the magnitude of 10-30% of the total contributions to global warming from the slurry in the reference system. However, scientific research is needed on field study level, both in the area of CH₄ emissions from in-house storage and outdoor storage and in area of N₂O emission from application of acidified slurry before a clear conclusion on the magnitude of the overall reductions of the contribution to global warming can be made.

4.2.4 Acidification (the environmental impact)

When comparing the system with acidified slurry with the reference slurry in figure 4.2 and 4.3, it is apparent that the contribution to the environmental impact “Acidification” is significantly reduced for the system with acidified slurry. As described in section 3.3 the contribution to the environmental impact “Acidification” is totally dominated by NH₃ emissions and the acidification of slurry reduce the NH₃ emissions significantly.

Even when taking the uncertainties into consideration, it can be concluded that the reduced NH₃ emissions lead to a reduced contribution to the environmental impact “Acidification”.

4.2.5 Aquatic eutrophication (N)

As can be seen in figure 4.2 and 4.3 the contributions to aquatic eutrophication (N) for the acidified slurry scenario are at the same level as the reference scenario (at a 10 years perspective) or higher (at a 100 years perspective). This is due to a higher N content in the slurry, leading to a higher nitrate leaching. On a 10 year basis, the increase is counteracted by a subtraction of “crop production”. This is due to the assumption that application of acidified slurry to fields leads to a higher crop yield. The assumption is based on field tests combined with the fact that the acidified slurry has a higher content of N. As the Danish law is today, this does not lead to farmers having to subtract a higher amount of N in their accounts. Accordingly, they are allowed to apply the same amount of N in mineral fertilisers to the field as for untreated slurry. As a consequence the field receives more N, leading to a higher crop yield. As the systems have to be equal in order to be comparable a corresponding amount of crop is subtracted from the system with acidified slurry. The uncertainty on the extra production of crop yield is very high and conclusions on the “net environmental impacts” from the “replaced crop” should be taken with care.

Alternatively, the increased amount of N in the acidified slurry could be subtracted as “replaced mineral N fertiliser”. This would, however, require that the Danish law increased the “replacement value” for N in acidified slurry compared to untreated slurry, having the consequence that the farmer had to subtract a higher amount of N in the N accounts. In that case, there would probably be no increase in the crop yield (as the field would receive the same amount of N as in the reference scenario). The amount of replaced N fertiliser would increase, and the picture for aquatic eutrophication (N) would be approximately the same as when subtracting the crop yield, i.e. a slightly higher amount of aquatic eutrophication can be subtracted from the system.

A sensitivity analysis has been carried out for the assumption that a future law demands that the farmer reduce the consumption of mineral N fertiliser in correspondence with the extra amount of N that the acidified slurry contains compared to non-treated slurry. This is shown in figure 4.8. From this is can be seen that the amount of replaced mineral N fertiliser would save significant amounts of N leaching.

On a 100 years perspective, most of the initially accumulated organic matter from slurry and crop residues will be mineralised to, amongst others, mineral nitrogen. This nitrogen will to some extend go to leaching, as outlined in Annex A. Therefore the 100 year leaching levels are higher than the 10 year levels.

At figure 4.4 there is an interesting aspect: For JB6 soil, the totalcontribution to aquatic eutrophication is slightly lower from the acidified slurry than from the reference scenario. The N leaching from the field is still higher for the acidified slurry, however, this is counterbalanced by the reductions of NH₃ in the housing units and during storage (as the airborne NH₃ emissions also contribute to aquatic eutrophication to some extent).

When taking the replaced crop yield into consideration, there is no significant difference between the acidification scenario and the reference scenario on a 10 year basis due to uncertainties. On a 100 year basis, the contribution to nitrate leaching is increased by 10-30% when comparing with the contribution from the reference system.

4.2.6 Aquatic eutrophication (P)

The leaching of phosphorous from application of acidified slurry is assumed to be the same as for application of untreated slurry. As the content of phosphorous is the same, there is no change in the contributions to aquatic eutrophication (P).

4.2.7 Photochemical Ozone Formation (“smog”)

As described in section 3.3, the main contributor to photochemical ozone formation is the CH₄ emissions from the in-house storage of slurry and the outdoor storage of slurry, which means that the photochemical ozone formation in figure 4.2 and figure 4.3 has the same uncertainties as described under global warming.

As described in chapter 3, section 3.4.3 and in Annex A, there are significant uncertainties related to the in-house CH₄ emissions (based on data from IPCC). The sensitivity analysis for this is shown in figure 4.5. As can be seen from the figure, the change of the in-house CH₄ emission has influence on the contributions to global warming and photochemical ozone formation. The absolute reduction by introducing acidification of slurry is less, when the in-house CH₄ emission is calculated as the lower IPCC value, however, the relative reduction for the total systems is approximately at the same level, and as mentioned under global warming, the choice of the lower IPCC value for the in-house CH₄ emission is considered not to be crucial for the conclusions.

As described under global warming, the choice of the higher IPCC value might overestimate the absolute net reduction by the acidification scenario for the photochemical ozone formation in person.ppm.hr (for explanation, see section 3.4.7 regarding Photochemical Ozone Formation).

4.2.8 Respiratory inorganics (small particles)

As described in section 3.3, the contributions to respiratory inorganics are totally dominated by contributions from NH₃. Accordingly, the contributions to respiratory inorganics follow the pattern for acidification.

It means that even when taking the uncertainties into consideration, it can be concluded that as acidification of slurry reduce NH₃ emissions this leads to a reduced contribution to the environmental impact “Respiratory inorganics”.

4.2.9 Non-renewable energy resources

The consumption of non-renewable energy resources is mainly due to transport, energy consumption during application of slurry and electricity. The consumption of electricity for the acidification plant increases the consumption of non-renewable energy resources compared to the reference system.

The increase in consumption of non-renewable energy resources caused by the electricity consumption by the acidification plant is partly counterbalanced by the energy use for the “replaced crop production” (due to the higher crop yield when applying acidified slurry as described under aquatic eutrophication (N)). As the uncertainty on the avoided energy consumption by the “replaced crop production” is rather high, the net consumption of non-renewable energy resources is somewhat uncertain. When taking the uncertainties into consideration, there is no significant difference between the acidification scenario and the reference scenario.

As mentioned above, a sensitivity analysis has been carried out assuming that the Danish Law is changed, leading to a requirement that the “fertiliser replacement value” reflects the actual content of N in the acidified slurry ex storage. As can be seen from figure 4.8 and 4.9 this does not change the conclusion regarding non-renewable energy resources.

A sensitivity analysis has been carried out for an acidification scenario with considerable higher electricity consumption by the acidification plant. As mentioned in Annex B, the electricity consumption for the acidification plant is 3 kWh per 1000 kg pig slurry and 1 kWh for 1000 kg dairy cow slurry. For at least one of the acidification plants at a pig farm, the energy consumption is considerably higher (Frandsen and Schelde, 2007), and in this case, the consumption of non-renewable energy resources by far exceeds the replaced amounts. The high energy consumption is, however, an exception according to the producer of the acidification plants, Infarm.

4.2.10 Consumption of phosphorus as a resource

There is no difference regarding the consumption of phosphorus as a resource between the Acidification Plant scenario and the reference scenario.

4.3 Conclusion

It should be emphasised that the data and conclusions in this report applies for Danish conditions only. Results cannot be immediately transferred to other countries due to differences in housing systems, retention time for the slurry in the housing units and in the outdoor storage, differences in how the slurry is stored (covered / uncovered), differences in temperatures, slurry composition (due to differences in the feeding of the animals), temperature, weather conditions (during and after application), soil types and many other factors.

The conclusions are only valid for the preconditions described in this report. For example, differences in application method to the field, uncovered outdoor storage or differences in the slurry composition will affects the results.

The results of the comparison are shown in table 4.1 and 4.2 (absolute values) and figure 4.10 and 4.11 (relative values).

The results of the comparative life cycle assessment show that:

Acidification of slurry reduces the NH₃ emissions significantly. As NH₃ gives the main contributions to the environmental impact categories “Acidification” and “Respiratory inorganics”, the total contributions to these are reduced considerably when comparing the acidification scenario to the reference. The contribution to “Acidification” is reduced by 40-90% compared to the contribution from the reference system for pig slurry and by 30-66% compared to the contribution from the reference system for dairy cow slurry. The contribution to “Respiratory inorganics” is reduced by 30-90% compared to the contribution from the reference system for pig slurry and by 20-70% compared to the contribution from the reference system for dairy cow slurry.
Acidification of slurry reduces the CH₄ emissions, probably due to that the biological activity is inhibited at the low pH. This leads to a reduction of the contributions to the environmental impacts “Global warming and “Photochemical ozone formation”. The contribution to “Global warming” is reduced by 10-36% compared to the contribution from the reference systems for pig and dairy cow slurry. The magnitude of the reductions is affected by a high uncertainty on the reductions of the CH₄ emissions and scientific research in the area is required in order to be able to give a clear picture of the magnitude of the reductions. Furthermore, it is not clarified whether acidification of slurry affects the N₂O emissions from field after application – research is also required in this area.
As the acidified slurry contains more N when applied to fields than untreated slurry (due to the reduced losses of NH₃ during storage), the contribution to nitrate leaching is higher for acidified slurry. The higher amount of N will lead to a higher crop yield. When comparing systems in life cycle assessments, it is very important that the outputs of the compared systems are equal (otherwise they are not comparable. For example, a system that produces 1 kg wheat shall not be compared to at system that produces 1 kg wheat plus 2 kg rye). In order to make the system for acidification of slurry equal to the reference system, a corresponding amount of crop yield has been subtracted from the system, which will to some extent counterbalance the higher nitrate leaching (however, these data are rather uncertain). When taking the replaced crop yield into consideration, there is no significant difference between the acidification scenario and the reference scenario on a 10 year basis due to uncertainties. On a 100 year basis, the contribution to nitrate leaching is increased by 10-30% when comparing with the contribution from the reference system.
Acidification of slurry does not affect “Aquatic phosphorous eutrophication” or the resource consumption of phosphorus, as acidification does not affect the content of phosphorus in the slurry.
The consumption of non-renewable energy resources is not significant higher for the acidification scenario as the extra consumption due to the electricity consumption is counterbalanced by the subtraction of the higher crop yield, as explained above.
Transport contributes to the consumption of non-renewable energy resources, and for the rest of the impact categories, the contribution from transport is not significant. As the transport is the same for the acidification scenario and the reference scenario, it has not significance for the comparison.
The difference between soil type JB3 and JB6 is only noteworthy for aquatic eutrophication (N) (nitrate leaching). The difference is not significant for the overall results.

Table 4.1. Comparison of the impacts from the acidification scenario to the reference scenario for pig slurry. The number of digits is not an expression of the uncertainty. The uncertainty of the net contribution is based on an estimate with regard to the uncertainty on the data that forms the foundation for the LCA.

Environmental impact / resource consumption	Reference scenario	Acidification scenario	Net contribution i.e. ”Acidification scenario” minus ”Reference scenario”
Global warming (during 10 years) [kg CO₂ eq.]	From slurry: 284 kg From fertiliser: -36 kg Net: 248 kg	From slurry: 225 kg From fertiliser: -46 kg Net: 179 kg	-68 [-35 – 100] kg CO₂ eq. 12-36% reduction of contribution from slurry
Global warming (during 100 years) [kg CO₂ eq.]	From slurry: 304 kg From fertiliser: -47 kg Net: 257 kg	From slurry: 244 kg From fertiliser: -56 kg Net: 188 kg	-69 [-35 – 100] kg CO₂ eq. 11-34% reduction of contribution from slurry
Acidification [m² UES, i.e. area of unprotected ecosystem]	From slurry: 50.3 m² From fertiliser: -5.5 m² Net: 44.8 m²	From slurry: 19.0 m² From fertiliser: -6.5 m² Net: 12.5 m²	-32 [-19- -45] m² UES 40-90% reduction of contribution from slurry
N-eutrophication (aquatic) (during 10 years) [kg N - amount reaching aquatic recipients]	From slurry: 1.51 kg From fertiliser: -0.93 kg Net: 0.59 kg	From slurry: 1.54 kg From fertiliser ¹: -1.03 kg Net: 0.51 kg	-0.08 [0 - -0.16] kg N No significant difference due to uncertainties on “avoided crop” (see text)
N-eutrophication (aquatic) (during 100 years) [kg N - amount reaching aquatic recipients]	From slurry: 1.63 kg From fertiliser: -1.03 kg Net: 0.61 kg	From slurry: 1.90 kg From fertiliser: -1.13 kg Net: 0.77 kg	0.17 [0.08 – 0.34] kg N 5-20% increase of contribution from slurry
P-eutrophication (aquatic) [kg P - amount reaching aquatic recipients]	From slurry: 0.0069 kg From fertiliser: -0.0086 kg Difference not significant due to high uncertainties	From slurry: 0.0069 kg From fertiliser: -0.0086 kg Difference not significant due to high uncertainties	No difference
Photochemical ozone formation [person.ppm.hr - see section 3.4.7]	From slurry: 0.18 p.p.h From fertiliser: -0.014 p.p.h Net: 0.17 p.p.h	From slurry: 0.11 p.p.h From fertiliser: -0.017 p.p.h Net: 0.089 p.p.h	-0.075 pers.ppm.hr [-0.038- -0.11] 20-60% reduction of contribution from slurry
Respiratory Inorganics [kg PM2.5 eq, i.e. kg equivalents of 2.5 µm size particles]	From slurry: 0.29 kg From fertiliser: - 0.05 kg Net: 0.24 kg	From slurry: 0.12 kg From fertiliser: - 0.06 kg Net: 0.06 kg	-0.18 [-0.09 – -0.26] kg PM2.5 30-90% reduction of contribution from slurry
Non-renewable energy [MJ primary energy]	From slurry: 151 MJ From fertiliser: - 369 MJ Net: -217 MJ	From slurry: 202 MJ From fertiliser ¹: - 406 MJ Net: -204 MJ	13 [ 0 – 39 ] MJ 0-26% increase of contribution from slurry
Phosphorus Resources [kg P]	From slurry: 0 kg From fertiliser: - 1.3 kg Net: - 1.3 kg	From slurry: 0 kg From fertiliser: - 1.3 kg Net: - 1.3 kg	No difference
Carbon stored in soil during 10 years [kg C] (Corresponding to this amount of CO₂-eq.)	From slurry: 7.5 kg C From fertiliser: - 3.9 kg C Net: 3.6 kg C From slurry: 27.6 kg CO₂ From fertiliser: -14.3 kg CO₂ Net: 13.2 kg CO₂	From slurry: 11.0 kg C From fertiliser: - 3.9 kg C Net: 7.1 kg C From slurry: 40.5 kg CO₂ From fertiliser: -14.3 kg CO₂ Net: 26.1 kg CO₂	3.5 [2.5 – 4.9 ] kg C 12.9 [ 9.2 - 18] kg CO2 33-65% increase of contribution from slurry
Carbon stored in soil during 100 years [kg C] (Corresponding to this amount of CO₂-eq.)	From slurry: 2.1 kg C From fertiliser: - 1.1 kg C Net: 1.0 kg C From slurry: 7.8 kg CO₂ From fertiliser: -4.0 kg CO₂ Net: 3.8 kg CO₂	From slurry: 5.9 kg C From fertiliser: - 1.1 kg C Net: 4.8 kg C From slurry: 21.6 kg CO₂ From fertiliser: -4.0 kg CO₂ Net: 17.6 kg CO₂	3.8 [2.7 – 5.3] kg C 13.7 [ 9.8 – 19.2] kg CO₂ 126 – 246% increase of contribution from slurry

¹This includes also the avoided N-eutrophication from the “replaced crop production”. As application of acidificed slurry increase the crop production, this crop is subtracted from the system. There is a large uncertainty onthis factor.

Table 4.2. Comparison of the impacts from the acidification scenario to the reference scenario for dairy cow slurry. The number of digits is not an expression of the uncertainty. The uncertainty of the net contribution is based on an estimate with regard to the uncertainty on the data thatforms the foundation for the LCA.

Environmental impact / resource consumption	Reference scenario	Acidification scenario	Net contribution i.e. ”Acidification scenario” minus ”Reference scenario”
Global warming (during 10 years) [kg CO₂ eq.]	From slurry: 326 kg From fertiliser: -40 kg Net: 286 kg	From slurry: 265 kg From fertiliser: -46 kg Net: 219 kg	-67 [-33 – 100] kg CO₂ eq. 10-30% reduction of contribution from slurry
Global warming (during 100 years) [kg CO₂ eq.]	From slurry: 355 kg From fertiliser: -51 kg Net: 304 kg	From slurry: 293 kg From fertiliser: -57 kg Net: 237 kg	-67 [-33 – 100] kg CO₂ eq. 10-30% reduction of contribution from slurry
Acidification [m² UES, i.e. area of unprotected ecosystem]	From slurry: 43.3 m² From fertiliser: -5.9 m² Net: 37 m²	From slurry: 23.0 m² From fertiliser: -6.6 m² Net: 16.8 m²	-20 [-12- -28] m² UES 30-66% reduction of contribution from slurry
N-eutrophication (aquatic) (during 10 years) [kg N - amount reaching aquatic recipients]	From slurry: 1.55 kg From fertiliser: -1.00 kg Net: 0.55 kg	From slurry: 1.55 kg From fertiliser ¹: -1.06kg Net: 0.49 kg	-0.06 [-0.12 - 0] kg N No significant difference due to uncertainties on “avoided crop” (see text)
N-eutrophication (aquatic) (during 100 years) [kg N - amount reaching aquatic recipients]	From slurry: 1.79 kg From fertiliser: -1.11 kg Net: 0.68 kg	From slurry: 2.18 kg From fertiliser: -1.17 kg Net: 1.01 kg	0.32 [0.16 – 0.49] kg N 10-30% increase of contribution from slurry
P-eutrophication (aquatic) [kg P - amount reaching aquatic recipients]	From slurry: 0.0063 kg From fertiliser: -0.0089 kg Difference not significant due to high uncertainties	From slurry: 0.0063 kg From fertiliser: -0.0089 kg Difference not significant due to high uncertainties	No difference
Photochemical ozone formation [person.ppm.hr - see section 3.4.7]	From slurry: 0.16 p.p.h From fertiliser: -0.02 p.p.h Net: 0.14 p.p.h	From slurry: 0.09 p.p.h From fertiliser: -0.017 p.p.h Net: 0.077 p.p.h	-0.067 pers.ppm.hr [-0.033- -0.10] 20-60% reduction of contribution from slurry
Respiratory Inorganics [kg PM2.5 eq, i.e. kg equivalents of 2.5 µm size particles]	From slurry: 0.25 kg From fertiliser: - 0.05 kg Net: 0.20 kg	From slurry: 0.14 kg From fertiliser: - 0.06 kg Net: 0.08 kg	-0.11 [-0.06 – -0.17] kg PM2.5 20-70% reduction of contribution from slurry
Non-renewable energy [MJ primary energy]	From slurry: 132 MJ From fertiliser: - 410 MJ Net: -279 MJ	From slurry: 161 MJ From fertiliser ¹: - 435 MJ Net: -275 MJ	4 [ -6 – +14 ] MJ No significant difference
Phosphorus Resources [kg P]	From slurry: 0 kg From fertiliser: - 1.5 kg Net: - 1.5 kg	From slurry: 0 kg From fertiliser: - 1.5 kg Net: - 1.5 kg	No difference
Carbon stored in soil during 10 years [kg C] (Corresponding to this amount of CO₂-eq.)	From slurry: 11.2 kg C From fertiliser: - 4.2 kg C Net: 7.0 kg C From slurry: 40.9 kg CO₂ From fertiliser: -15.5 kg CO₂ Net: 25.5 kg CO₂	From slurry: 15.8 kg C From fertiliser: - 4.2 kg C Net: 11.6 kg C From slurry: 57.9 kg CO₂ From fertiliser: -15.5 kg CO₂ Net: 42.4 kg CO₂	4.6 [3.3 – 6.5] kg C 17.0 [ 12.1 – 23.8] kg CO₂ 30 – 60% increase of contribution from slurry
Carbon stored in soil during 100 years [kg C] (Corresponding to this amount of CO₂-eq.)	From slurry: 3.2 kg C From fertiliser: - 1.2 kg C Net: 2.0 kg C From slurry: 11.6 kg CO₂ From fertiliser: -4.4 kg CO₂ Net: 7.3 kg CO₂	From slurry: 8.0 kg C From fertiliser: - 1.2 kg C Net: 6.8 kg C From slurry: 29.3 kg CO₂ From fertiliser: -4.4 kg CO₂ Net: 25.0 kg CO₂	4.8 [3.5 – 6.8] kg C 17.7 [ 12.6 – 24.8] kg CO₂ 100 – 200% increase of contribution from slurry

Figure 4.10. Environmental impacts for the system with acidification of slurry in an infarm NH4+ plant compared to the reference system (both based on soil type JB3) – pig slurry.

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Figure 4.11. Environmental impacts for the system with acidification of slurry in an infarm NH4+ plant compared to the reference system (both based on soil type JB3) – dairy cow slurry.

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