Crop-Livestock Farming Systems Assessment in Europe

Two contrasting organic dairy systems were studied during the period 1998 to 2006. Ty Gwyn organic dairy farm is located in West Wales and is sub-divided into two separate dairy systems in the 1998/99 period. The total land area for both systems was approximately 95ha. The land was primarily sandy or silty-clay loam over gravel, with a smaller area of deep silty loam. The average annual rainfall on the farm was 1,253 mm. In each system the physical resources included three separate silage clamps, two slurry storage tanks, two calving boxes and a cubicle shed with the capacity for up to 60 cows during the 6-month winter housing period. These two contrasting organic dairy system established in 1998 and studied through until 2006 formed:

• The Baseline system (S0) known as the Purchased Concentrate (PC) system. The main objective of this system was to maximize the output within the standards for organic production in relation to production per cow and per unit area of land, by purchasing all concentrate feeds to supplement the home-grown forages utilized for both grazing and conservation.

• The Innovative mixed farming Strategy (S1) known as the Self Sufficient (SS) system. The main objective of this system was to provide all animal feed (both concentrate and forage) and on-farm nutrients for crop production within a closed system that aimed to maximize the level of self-sufficiency and long-term sustainability.

So, S0 represents a specialized livestock farm without any integration and S1 a integrated crop-livestock farm where crops are used to feed livestock.

The main evolutions between S0 and S1 are the introduction of cereals (barley and triticale) in rotation with temporary grassland, a decreasing of livestock density (1,7 to 1,3) due to the stop of concentrates purchased, a change in the feed ration (1430 kg of concentrates per cow per year to 388) and finally a change in the milk production (61 dairy cows producing 6343 kg milk (energy corrected) to 51 cows producing 5473 kg milk

Results

The comparison of the innovation scenario S1 with the baseline scenario S0 reveals that there is a clear improvement of the environmental performance for the resource-related, the nutrient-related, and the pollutant-related environmental impacts expressed by ha (functional unit = ha Utilized Agricultural Area). However, the scores for biodiversity remained similar

The assessment of the results by MJ digestible energy for S1 in comparison with S0 leads to a different judgement depending on the group of the impact categories. For the majority of the resource related impacts there is an increase of approx. 12 percentage points which is considered to be unfavourable. However for 3 out of 4 nutrients related impacts the results for S1 are considered to be similar. Only for aquatic eutrophication N there is a reduction considered favourable (figure below). Finally in the group of the pollutants related impacts the terrestrial human- and ecotoxicity categories are considered to be favourable or even very favourable in comparison with S0. The remaining impact categories have for S1 in tendency higher results than in S0. However, they are still judged to be similar.

Conclusion for Ty Gwyn

The LCA results for the case study Ty Gwyn largely reflect the expectations as a consequence of the two strategies employed. The baseline scenario S0 consisting of a high input strategy for organic dairy production uses more inputs and producing a higher amount of milk meaning that with respect to the function of agriculture of producing food and feed (per MJ DE) S0 performs environmentally better. However if the focus is on the preservation of livelihood expressed in the function of sustaining the agricultural land for future generations (per ha UAA*a) obviously the low-input, self-sufficient approach has the better environmental performance.

The farm is located in the municipality of Comano Terme, in the province of Trento (Trentino-Alto-Adige region), in Northern Italy at 550 m above sea level. The average annual temperature in the site is 10.5 C and total rainfall per year is 1,150 mm.

San Giuliano farm is a commercial farm in which 7-8 people work. It is a dairy farm with more than 500 housed livestock and around 100 ha of utilized agricultural area. Around 50 ha owned by other farms received the livestock manure. The farm produces high quality milk for a local cheese cooperative. They proceed to an “exchange of land” with arable farms producing potatoes, to avoid monoculture.

The 260 lactating cows (680 kg average body weight) are bred in a building with cubicle housing, with straw on concrete floor and automatic scraper. There are also 40 dry cows and 40 pregnant heifers (calving at 24 months, 550 kg average body weight). The 170 dairy followers are housed in deep litter system. Cows are fed with a total mixed ration. The farm has a total milk production of 2.6-2.7 million kg/year.

In the baseline scenario S0, referred to 2010, San Giuliano was a typical dairy farm without any production of renewable energy. The utilized agricultural area cultivated by the farm was 95 ha. The agricultural area was composed of 37 ha with permanent grassland (12 irrigated + 25 not irrigated), 42 ha with maize (for silage), 6 ha Italian ryegrass and silage maize (double crop in one year) and 10 ha with potato. The fertilization was based on livestock manure (both cattle slurry and farmyard manure) plus mineral fertilisers such as urea on maize, complex NPK and ammonium nitrate on potato.

In the innovation scenario S1, referred to 2012, processing of livestock manure through anaerobic digestion was adopted. The raw digestate is partly dried and sold as fertiliser. Moreover, a photovoltaic system was installed on the roofs of farm buildings.

The biogas plant is active since 2011 and is treating mainly livestock manure (both the liquid and the solid manure produced in the farm) and some residues from the feeding of animals. Cattle slurry is scraped and sent to the biogas plant every 12 hours.

This is a mesophilic (35-38°C) continuous process, with 3 fermenters. The total capacity is 6,150 m3 and the total retention time more than 150 days. The power of the plant is 250 kWel, the heat produced by the CHP unit is used to dry part of the raw digestate.

1,095,000 Nm3 of biogas have been produced in one year. The biogas contains 52% of methane, consequently 5,454 MWh of primary energy entering CHP unit. The average production of electricity for one year is 2,127 MWhe, the biogas unit consuming 10% of electricity produced and having an electrical yield of 39%. The heat is mainly used for drying digestate, and a small part is used in winter to heat the farmer's house. Since 2014, a part of the heat is also used to heat the cows' drinking water.

In the innovation scenario S2, referred to next 2012 adapted, it was hypothesized that measures would result in a situation that all nutrients applied to the fields derive from the digestate and that no mineral fertilizer is necessary to support crop production. S2 is a 'technological' improved scenario based on the solid-liquid separation of the whole amount of the digestate. There is no more raw digestate in the farm but clarified fraction and dried digestate derived from the solid fraction of digestate. All the clarified fraction and part of the dried digestate are used internally to fertilize crops and the mineral fertilisers consumption is reduced to zero. Part of the clarified fraction is used on growing crops with a special spreader. The sale of dried digestate is three times higher compared to S1.

Results

Overlooking all results for the function of sustaining agriculturally productive land, i.e. per ha UAA*a, the innovation scenario S1 has only in the case of Ozone formation and Aquatic eutrophication N LCA results that are less favourable than for the baseline scenario S0. This is also valid for the refinement scenario S2. A closer look reveals that the results are very favourable for S1 and S2 compared to S0 for the resource-related impacts; for the nutrient-related impacts the results are contrasting, whereas for the pollutant-related impacts the results are similar or even favourable. Additionally for biodiversity the results of S1 and S2 are judged to be similar or even favourable in comparison with S0 (figure below).

The majority of the LCA results for the innovation (S1) and refinement (S2) scenario per MJ digestible energy are considered to be similar to the results of the baseline scenario S0. The exception are the results of categories GWP 100a and Ozone formation, which are judged to be favourable. GWP shows a reduction of the impact by 12 and 13 percentage points for S1 and S2, respectively compared to S0. The reasons are the decrease of greenhouse gases through the installation of a biogas and CHP plant as well as at the farm output measured in MJ DE was slightly increased.

A representative selection of impact categories are shown in figure below. For the other impact categories than GWP, the figure illustrates that there are only minor changes between the results of S0, S1, and S2.

Conclusion for San Giuliano

The introduction of a biogas plant and a photovoltaic device in the innovation scenario S1 has led to important reductions for several resource related impacts, e.g. non renewable energy demand, global warming potential, and use of phosphorous resources as well as for aquatic eutrophication P per ha UAA*a. With little disadvantages such as the increase of the environmental impact for aquatic eutrophication N and most other impact categories remaining similar to the baseline S0 we conclude that the stronger integration of the animal and crop production through the biogas plant has led to the desired reduction of the environmental burden. When analysed for the productive function, i.e. per MJ digestible energy, the advantages are also present, but less dominant as the differences in the productive outcome are not as pronounced between S0, S1 and S2.

The refinement scenario S2 with an optimisation of the digestate treating process did not have the hoped for environmental improvements. In conclusion this means, that for further improvements the refining has to be rethought.

The case study is a commercial farm located in the south west of France. The climate there is oceanic with temperate summer, with average annual precipitation of 700 mm/yr (with a winter rainfall from November to March of 500 mm), and average annual temperature of 15°C. Soils are mainly clay and limestone. The farms has 220 sows and an agricultural surface of 70 ha.

This case study is partly real and partly modeled. It is interesting because it allows to show the environmental progress coming from an increasing integration between crops and animal production.

We have 3 steps.

Baseline S0 is a virtual scenario without any integration. On one hand, we have a specialized pig farm without area which produces only pigs with all the feed being purchased. The slurry is fully exported but without any value-creation. It is considered as a waste. On the other hand, we have a specialized crop farm which produces cereals, grains... which are sold on the market. The crops are fertilized with purchased mineral fertilizers.

The LCA will calculate the sum of the impacts of these 2 farms which do not interact (degree-zero of the integration) and will use as functional units (i) the sum of the farmed areas (ie just the area of the crop farm because there is no area for the pig farm) and (ii) the sum of the sold productions (pigs+crops) expressed as DE.

The innovative scenario S1 corresponds to the actual farm. On this farm, we have a pig enterprise (same size and same technical characteristics than the previous pig farm) and crop areas (same area than the previous crop farm). These crops produce a large part of the feed needed by the pigs, so we have less crops sold than for S0 but we have at the same time less purchased feed. The pigs produce slurry which fertilize the crops so we have less purchased mineral fertilizer and also less slurry exported. In addition, photovoltaic electricity is produced.

The LCA will calculate the whole impacts of this farm and will use as FU the farmed area (the same than in S0) and the sold DE (lower than in S0 because of the self consumption of a large part of the crops).

The innovative scenario S2 Is a virtual scenario which optimizes the integration between pig and crop farming. It consists first in a decreasing of the pig production to match exactly the quantity of slurry with the capacity of spreading (depending of the needs of the crops). In this case, there is not exported slurry. It consists also in an improvement of the quality of the effluents by separation phase and composting. As in S1, photovoltaic electricity is produced.

The LCA will calculate the whole impacts of this farm and will use as FU the farmed area (the same than in S0) and the sold DE (lower than in S0 because of the self consumption of a large part of the crops and because a lower pig production).

Results

Between S0 and S1 or S2, the evolution is positive for all the selected impacts categories with FU=area. We can see also that there are no differences between S1 and S2 (figure below).

But when we take the sold DE as FU, the results are less positive. The environmental burden is worse in S1 and S2 compared to S0 for GWP, about equal for NRE and eutrophication P but are even better for eutrophication N and terrestrial ecotoxicity (figure below).

Conclusion

The contribution analysis shows that the main benefit for the environment resulted from the innovation of substituting purchased feed by locally produced pig feed. For all five impact categories assessed, the main reduction was due to the input group ‘Feedstuff concentrates'. The replacement of mineral fertiliser by farmyard manure contributed to an improvement of the environmental performance in the two innovation scenarios, but this improvement was lower compared to the benefits of replacing purchased feed by own feed. Overall, the decisive factor is the important drop in the agricultural production of the two innovation scenarios resulting in 68% (S1) and 65% (S2) of DE produced in S0.

The production of photovoltaic energy was beneficial in terms of credits for non-renewable energy, GHG emissions and aquatic eutrophication P avoided elsewhere but we must say that this improvement is not linked to the integration of crops and animals: it would be fully possible to install photovoltaic panels in the 2 specialized farms of S0 as well.