Combining livestock and tree crops to improve sustainability in agriculture: a case study using the Life Cycle Assessment (LCA) approach

Highlights

• Reducing agriculture's environmental impact is fundamental for global sustainability.

• Animals rearing has a high impact, partly due to land use for grazing.

• Grazing in orchards eliminates the additional land use due to grazing.

• Grazing provides weeding and fertilization, dramatically reducing the orchard's impact.

• Combining animals and orchards reduces the environmental impact of both.

Abstract

Agriculture contributes significantly to GHG emissions and global warming and reducing its environmental impact is fundamental for global sustainability. Extensive rearing systems for poultry production, such as free-range systems, are considered with great interest due to their positive effects on meat quality and animal welfare and health, but their environmental impact is still debated, in part because of the high land-use impacts due to the land requirements for grazing. However, it is possible to combine orchards and animals in the same area, thus eliminating additional land use for grazing. This study investigated the environmental impact of combining free-range poultry and olive orchards using a cradle to gate Life Cycle Assessment (LCA) approach. The impact assessment was developed using the ‘Eco-Indicator 99 method. Feed production was the process with the highest impact on the poultry system (96% and 84% of the total normalized impact, respectively, for poultry inside and outside the orchard). The land-use category had the highest impact, both for the poultry (62 and 67%, respectively, inside and outside the orchard) and for the olive (99 and 70%, respectively, for grazed and non-grazed orchards) systems. Grazing poultry in the olive orchard and eliminating the land use due to grazing (accounted for in the orchard LCA) decreased the land-use impact of the poultry system by 18% and reduced the overall impact by approximately 12%. By providing weed control and fertilization in the orchard, grazing also dramatically reduced the impact of the olive orchard for all of the categories considered, except for land use, which had the highest impact (70%). Therefore, the overall impact reduction with the chickens grazing in orchards was approximately 30%; however, this impact reduction approached 100% if land use was not considered. Additional benefits of combining poultry and orchard that are not considered in the LCA are briefly discussed. Although this was a case study with olives and poultry, the results are applicable to other combinations of livestock and crops, and show that such combinations provide significant reductions in the environmental impacts of agriculture. The results can be useful when developing guidelines to improve sustainability in agriculture.

Introduction

Climate change is one of the most important concerns for the international environmental policy. To reduce emissions and to develop proper mitigation and adaptation measures, governments need information and data on the most important source of greenhouse gas emissions. Emissions of CO₂, CH₄ and N₂O from agriculture account for one-fifth of the annual forcing of climate change, or for one-third when land use changes are included (Cole et al., 1997). Agriculture is the main producer of CH₄, mostly due to livestock (Mosier et al., 1998) and of N₂O, mostly due to N fertilization of crops (Forster et al., 2007), two gases with about 23 and 300 times the global warming potential of CO₂. Livestock alone accounts for 18% of global green-house gas emissions (FAO, 2006), or perhaps even more (Goodland and Anhang, 2009, Herrero et al., 2011). In the last decades, the environmental impacts of agriculture and animal production have been increasingly acknowledged. Modern agriculture must combine high productivity with a low impact to sustainably feed the growing world population. With increasing wealth in developing countries people will consume more meat; therefore, meat consumption, and consequently the high environmental impact from livestock production, is expected to increase at a greater rate than the population growth rate.

In this scenario, chicken meat, mainly due to the high efficiency in converting feed into meat, is particularly interesting because of its lower environmental impact relative to other meats (Williams et al., 2006).

Free-range chickens have a higher meat quality than chickens from intensive systems with no grazing (Castellini et al., 2006b), and at the same time, they also enjoy better health and animal welfare (Castellini et al., 2008). In fact, selection for a high growth rate and high feed conversion efficiency negatively affected animal welfare (Bessei, 2006) by impairing health status and behavior (Bokkers and Koene, 2003, Turner et al., 2003). A modern broiler is approximately 2.5 kg at 42 d, and the breast represents approximately 25% of the whole body (Groot Koerkamp et al., 2003), favoring skeletal imbalances (Kestin et al., 1992, Kestin et al., 2001, Corr et al., 2003a, Corr et al., 2003b) and other metabolic and muscle disorders (Branciari et al., 2009, Branciari et al., 2014). Accordingly, welfare and health issues are major concerns in intensive poultry systems (EU, 2000); organic and free-range production systems have been developed in response to such problems (EU, 1999).

The production system affects not only the animal welfare but also economic, qualitative, and ecological traits (Hermansen et al., 2004). While some authors found that free-range poultry has lower environmental impacts (Castellini et al., 2006a, Castellini et al., 2012b, Boggia et al., 2010), or that there are serious concerns surrounding the long-term sustainability of intensive poultry systems (Veleva et al., 2001, Tilman et al., 2002, Cerutti et al., 2011, Acosta–Alba et al., 2012, Lindsey, 2012, Zhang et al., 2012), others found that intensive systems are more sustainable (Bokkers and De Boer, 2009). Most of the discrepancies are due to the type of raw data used and to the methods used for measuring the impact (e.g., Life Cycle Assessment (LCA), emergy, or ecological footprint). Indeed, even if all of the methods are effective in representing the environmental features of a given activity, each method has both positive and negative aspects (Bastianoni et al., 2010). The factor that always plays a major role in the environmental impacts of these systems is the higher feed consumption per kilogram of meat of free-range birds (i.e., in free-range systems slower-growing animals are usually used, which have lower feed conversion efficiencies). Moreover, in free-range systems, birds need grazing space, which increases the amount of land used. In fact, although grazing provides bioactive compounds and increases meat quality (Fanatico et al., 2006), the energy and protein supplied for the birds’ diets are usually low (Walker and Gordon, 2003, Buchanan et al., 2007, Rivera-Ferre et al., 2007), and the additional land use due to grazing in free-range systems is not compensated for by a proportional reduction in land use for feed production.

However, there is no reason why chickens should occupy pastureland that is not already productive. In the past, it was common to rear chickens in fruit orchards (Bertoni, 1906, Donno, 1937). Trees have been shown to benefit chickens in terms of protection from predators (i.e., especially raptors), sun, wind, the elements and extreme temperatures, thus reducing animal losses and increasing the time and amount of grazing (Bubier and Bradshaw, 1998, Mirabito and Lubac, 2001, Dal Bosco et al., 2014a). Therefore, combining free-range animals with orchards, rather than grazing otherwise unproductive pastures, results in less land use and provides other environmental benefits in the orchard (i.e., reduced need for fertilization and weed control). According to the International Fund for Agricultural Development (IFAD), the integrated crop-livestock farming system “represents a winning combination that (a) reduces erosion; (b) increases crop yields, soil biological activity and nutrient recycling; (c) intensifies land use, improving profits; and (d) can therefore help reduce poverty and malnutrition and strengthen environmental sustainability” (IFAD, 2010).

While several older papers describe the benefits and the techniques of poultry rearing in orchards (e.g., Bertoni, 1906, Donno, 1937), a comparison of the environmental impact of free-range chickens reared in an orchard vs. rearing in a pasture solely for chickens has not been performed.

In the present work, we performed this analysis using the Life Cycle Assessment (LCA) to compare free-range chickens reared in olive orchards vs. pure pastureland (i.e., dedicated only to chickens and otherwise unproductive). We also performed the LCA for the olive orchard, with and without grazing chickens. All of the main phases of the systems' life cycle were considered, from the production of raw materials to the final product at the farm gate, i.e. from cradle to gate, for both poultry and olive production. This is the first time the environmental impact of an integrated livestock-orchard system has been evaluated.