DISS ETH NO 21872
IMPROVING ECO-EFFICIENCY OF LOW-INPUT CROPPING SYSTEMS BY THE USE OF LIFE CYCLE ASSESSMENT AND INTEGRATIVE APPROACH
A thesis submitted to attain the degree of DOCTOR OF SCIENCES OF ETH ZURICH
(Dr Sc. ETH Zurich)
Presented by MICHAL ADAM KULAK
Master of Science (MSc) in Innovation and Design for Sustainability, Cranfield University Born on 30.12.1985
Citizen of Poland
Accepted on the recommendation of:
Prof. Emmanuel Frossard, ETH Zurich
Dr Thomas Nemecek, Agroscope
Prof. Steve Evans, University of Cambridge
2014
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3 TABLE OF CONTENTS
List of abbreviations ... 4
Abstract ... 5
Zusammenfassung ... 7
Résumé ... 9
General introduction ... 11
Chapter 1. How eco-efficient are low-input cropping systems in Western Europe and what can be done to improve their eco-efficiency? ... 23
Chapter 2. Life cycle assessment of several alternative bread supply chains in Europe ... 47
Chapter 3. Using LCA and integrative design for improving eco-efficiency. The case of Bread in France. ... 63
Discussion ... 77
References ... 91
Appendix A. Life Cycle Inventories for Chapter 2 ... 99
Appendix B. Life Cycle Inventories for Chapter 3 ... 110
Acknowledgements ... 116
4 LIST OF ABBREVIATIONS
AD Anaerobic digestion
FAO Food and Agriculture Organization of the United Nations
FU Functional Unit
GWP Global Warming Potential
LCA Life Cycle Assessment
LER Land Equivalent Ratio
LICS Low-Input Cropping Systems
N Nitrogen
NFT Nitrogen Fixing Trees
P Phosphorus
SI Sustainable Intensification
5 ABSTRACT
Low-input cropping systems (LICS) in Europe are characterised by mostly lower environmental impacts per unit of land compared to high-input agriculture, but their benefits remain unclear when productivity is taken into account. The research described in this thesis was conducted with two goals: i.) to assess the eco-efficiency of European low-input cereal-based cropping systems, where eco-efficiency is understood as the ratio of environmental impacts to production quantity and ii.) to identify factors limiting eco-efficiency and assess the potential for improvements.
The first part of the thesis provides a review of the current literature on the relationship between the application of agricultural inputs to cropping systems and environmental impacts quantified with the use of product Life Cycle Assessment (LCA). Various interventions are also reviewed that can improve this ratio. The empirical evidence shows that eco-efficient cropping systems require application of optimum instead of minimum quantities of external inputs. These optimum rates can be lowered by utilising positive synergies between crops to minimise waste of nutrients and water and by utilising locally produced organic waste; both from within the farm as well as from the surrounding sociotechnical environment. Strategies such as switching cultivars, mixing cultivars, no-tillage, intercropping or anaerobic digestion can improve eco-efficiency at the same level of agricultural inputs, but they will not be effective under all conditions. Choices of inputs and their levels need to be considered under the specific agro-climatic and socio-economic regimes.
In the second part of the study, environmental impacts of several cases of bread from LICS were compared to standard references with the use of LCA. The selection of cases covered two different European climatic zones: Temperate oceanic and Mediterranean and two different scales of production:
farms below 10 ha and over 70 ha. Primary data were collected directly from producers. Standard references were assumed to be breads made of cereals cultivated with standard methods, processed in industrial mill and bakery and distributed through the supermarket. The study produced highly variable results depending on farm management, year, location and organisation of the distribution chain.
Neither LICS nor on-farm processing was observed to guarantee reductions in environmental impacts, although numerous opportunities for system improvements were identified over the course of this analysis.
In the third part of the study, a structured, multi-stakeholder procedure was followed to identify opportunities for improvements in two cases from France. Results of LCA with highlights of processes responsible for the largest share of environmental impacts were disclosed to stakeholders during the collaborative design workshop. Teams of participants consisting of plant breeders, agronomists and representatives of farmer’s associations were asked to map out opportunities for system improvements. Improvement scenarios were consulted with producers and only approved
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solutions were considered in further LCA simulations. Conservative models revealed potential reduction of 47% in the Global Warming Potential per kg of bread at one farm and 40% reduction for aquatic eutrophication at the other one. Results suggest that in addition to biophysical limitations, farms may suffer from the lack of innovation, suboptimal management and the lack of access to reliable environmental information.
The research described in this thesis has shown that the level of farm-external inputs cannot be used as a proxy of environmental performance. Although there are visible trends between the application of inputs to cropping systems and environmental impacts of their products, final results are highly dependent on a number of other factors. LICS are not per se more eco-efficient than high-input agriculture. However, they can potentially have similar or better performance with their proper organisation. Although some of the limiting factors are external and independent of the farmer-such as the electricity mix of the country in which the production is located, eco-efficiency can be highly influenced by management decisions made by farmers. There is a scope for large improvements of eco- efficiency within LICS, but the supply of environmental information may be necessary to support making the right design decisions.
7 ZUSAMMENFASSUNG
Low-Input-Anbausysteme in Europa haben meistens geringere Umweltwirkungen pro Flächeneinheit als die High-Input-Landwirtschaft, ihre Vorteile sind jedoch nicht eindeutig, wenn die Produktivität berücksichtigt wird. Die in dieser Dissertation beschriebene Forschung befasste sich mit zwei Hauptzielen: i.) Die Beurteilung der Ökoeffizienz europäischer Low-Input-Systeme für den Getreideanbau, wobei unter Ökoeffizienz das Verhältnis von Umweltwirkungen zum Produktion zu verstehen ist. ii.) Die Identifizierung limitierender Faktoren und des Verbesserungspotenzials.
Der erste Teil der Dissertation besteht in einer systematischen Prüfung der aktuellen Literatur zum Verhältnis zwischen dem landwirtschaftlichen Input von Anbausystemen und den Umweltwirkungen, die mit Hilfe der Produkt-Ökobilanz (Life Cycle Assessment) quantifiziert werden. Es wurden auch zahlreiche Massnahmen untersucht, welche die Leistungsfähigkeit der Systeme verbessern können. Die empirischen Daten zeigen, dass eine gute Ökoeffizienz von Anbausystemen nicht mit einer minimalen, sondern mit einer optimalen Menge von Inputs erreicht wird. Diese optimale Inputmenge kann reduziert werden durch die Nutzung von Synergien zwischen verschiedenen Kulturen, welche die Nährstoff- und Wasserverluste verringern, sowie durch die Nutzung lokaler organischer Abfälle, die entweder im Landwirtschaftsbetrieb selber oder im nahen soziotechnischen Umfeld anfallen. Strategien wie Züchtung, Sortenmischungen, Direktsaat, Mischkulturen oder Biogasanlagen können die Ökoeffizienz bei gleichem Input verbessern, sind aber nicht unter allen Bedingungen wirksam. Welche Inputs in welcher Menge eingesetzt werden, hängt von den spezifischen agroklimatischen und sozioökonomischen Gegebenheiten ab.
Im zweiten Teil der Studie wurden die Umweltwirkungen der Herstellung von Brot aus verschiedenen Low-Input-Betrieben mit Referenzstandards verglichen. Die Betriebe wurden so gewählt, dass zwei Klimazonen Europas (gemässigtes ozeanisches und mediterranes Klima) und zwei Betriebsgrössen (unter 10 ha und über 70 ha) vertreten waren. Die Basisdaten wurden direkt bei den Produzenten erhoben. Als Referenz galten Brote aus dem Supermarkt, wobei das Getreide mit Standard- Methoden produziert wurde. Die Studie ergab je nach Betriebsführung, Jahr, Standort und Organisation der Vertriebskette sehr unterschiedliche Resultate. Weder die Low-Input-Bewirtschaftung noch die Verarbeitung auf dem Landwirtschaftsbetrieb führte zu einer zuverlässigen Reduktion der Umweltwirkungen. Im Laufe der Analyse konnten jedoch zahlreiche Möglichkeiten identifiziert werden, mit denen sich Verbesserungen des Systems erzielen liessen.
Im dritten Teil der Studie wurden verschiedene Akteure einbezogen, um Verbesserungsmöglichkeiten für zwei Fallbeispiele in Frankreich zu finden. Dazu wurden den Akteuren im Rahmen eines partizipativen Design-Workshops die Ökobilanzen vorgelegt, bei denen die Prozesse mit den grössten Umweltwirkungen aufgeführt waren. Die Teilnehmerteams, bestehend aus
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Pflanzenzüchtern, Agronomen und Vertretern der Bauernverbände, erarbeiteten dann Möglichkeiten für Systemverbesserungen. Die Verbesserungsszenarien wurden Produzenten vorgelegt und nur für weitere Simulationen berücksichtigt, wenn sie deren Zustimmung fanden. Konservative Modelle ergaben eine potenzielle Reduktion des Treibhauspotentials pro Kilogramm Brot um mindestens 47%
beim einen Betrieb und eine Reduktion der aquatischen Eutrophierung um 40% beim anderen Betrieb.
Die Ergebnisse lassen vermuten, dass die Landwirtschaftsbetriebe nicht nur aufgrund von biophysikalischen Aspekten an Grenzen stossen, sondern auch durch fehlende Innovation, eine suboptimale Betriebsführung und ein Mangel an zuverlässigen Umweltinformationen.
Die in dieser Dissertation beschriebene Forschung zeigt, dass zwischen den Inputs von Anbausystemen und den Umweltwirkungen der erzeugten Produkte Zusammenhänge bestehen, die sich mit Ökobilanzen beschreiben lassen. Wenn die Inputs extrem reduziert werden, ist das Ergebnis aus Sicht der Ökoeffizienz nicht optimal. Die Ökoeffizienz hängt auch wesentlich von anderen Komponenten des Anbausystems sowie von der Verarbeitung, vom Vertrieb und vom soziotechnischen Umfeld ab.
Low-Input-Anbausysteme sind nicht per se ökoeffizienter als High-Input-Systeme. Sie können aber bei einer geeigneten Organisation bessere Ergebnisse erzielen. Zwar lassen sich nicht alle begrenzenden Faktoren mit der Betriebsführung beeinflussen, die Ökoeffizienz hängt aber doch stark von betriebsspezifischen Entscheidungen ab. Es besteht innerhalb der Low-Input-Landwirtschaft Spielraum für wesentliche Verbesserungen der Ökoeffizienz. Damit die richtigen Entscheidungen getroffen werden können, müssen jedoch ausreichende Umweltinformationen zur Verfügung stehen.
9 RÉSUMÉ
En Europe, les systèmes culturaux à faible niveau d’intrants se caractérisent par des impacts environnementaux généralement plus faibles par unité de surface par rapport à l’agriculture intensive, mais leurs performances environnementales restent inconnues. Les recherches décrites dans la présente thèse avaient deux objectifs principaux: i.) évaluer l’éco-efficience des systèmes de cultures de céréales européens à faibles intrants exprimée par le rapport entre production et impacts sur l’environnement et ii.) identifier les facteurs handicapants afin d’évaluer le potentiel d’amélioration.
La première partie de la thèse conduit une revue systématique de la littérature sur le rapport entre l’application des intrants agricoles dans les systèmes culturaux et l’impact environnemental quantifié grâce aux analyses de cycle de vie (Life Cycle Assessment, LCA). Différentes interventions sont également présentées, comme étant susceptibles d’améliorer les rendements. L’expérience montre que l’éco-efficience des systèmes culturaux implique l’application de quantités optimales et non minimales d’intrants externes. Ces quantités optimales peuvent être réduites en exploitant les synergies entre les cultures afin de minimiser les pertes d’éléments nutritifs et d’eau ainsi qu’en utilisant les déchets organiques locaux; à l’échelle de la ferme comme à l’échelle de l’environnement socio-technique proche. Les stratégies telles que la sélection, le mélange des variétés, le semis direct, les cultures intercalaires ou la digestion anaérobique peuvent accroître l’éco-efficience avec le même niveau d’intrants agricoles, mais elles ne fonctionnent pas dans toutes les conditions. Le choix des intrants et de leurs quantités doit tenir compte des régimes agroclimatiques et socio-économiques spécifiques.
La deuxième partie de l’étude consistait à comparer les impacts environnementaux de différents types de pains issus de l’agriculture à faibles intrants à des pains de référence. Les cas étudiés ont été sélectionnés dans deux zones climatiques européennes: la zone tempérée océanique et la zone méditerranéenne, pour deux niveaux de production différents: exploitations de moins de 10 ha et de plus de 70 ha. Les données de base ont été recueillies directement chez les producteurs. Les pains de référence étaient supposés être des pains faits à partir de céréales cultivées selon les méthodes modernes, fabriqués par des moulins et des boulangeries industriels et distribués en supermarchés.
L’étude a donné des résultats extrêmement variables suivant la gestion de la ferme, l’année, la situation géographique de l’exploitation et l’organisation de la chaîne de distribution. On a constaté que ni l’agriculture à faible niveau d’intrants, ni la transformation sur le site ne garantissaient la réduction des impacts environnementaux, bien que de nombreuses possibilités pour améliorer les systèmes aient pu être identifiées durant l’analyse.
La troisième partie de l’étude a suivi une procédure structurée, associant l’ensemble des parties intéressées afin d’identifier les possibilités d’amélioration dans deux cas en France. Les résultats d’analyses de cycles de vie joints aux processus-phares responsables de la majeure partie des impacts
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environnementaux ont été communiqués aux parties intéressées durant l’atelier de conception interdisciplinaire. On a demandé à des équipes de participants composées de sélectionneurs, d’agronomes et de représentants des associations d’agriculteurs d’esquisser les possibilités d’amélioration des systèmes. Les scénarios d’amélioration ont fait l’objet de concertations avec les producteurs et seules les solutions approuvées ont été retenues pour les simulations. Les modèles conservateurs ont indiqué des possibilités de réduction d’au moins 47% du potentiel de réchauffement climatique global par kilo de pain dans une exploitation et de 40% de réduction de l’eutrophisation aquatique dans une autre. Les résultats suggèrent qu’outre les limites biophysiques, les exploitations souffrent du manque d’innovation, d’un management insuffisant et du manque d’informations environnementales fiables.
Les recherches décrites dans la présente thèse ont montré qu’il existe des liens visibles entre l’application d’intrants dans les systèmes culturaux et les impacts environnementaux de leurs produits, liens qui peuvent être mis en évidence grâce aux analyses de cycle de vie. Du point de vue de l’éco- efficience, il ne serait pas idéal de réduire la quantité des intrants à un niveau extrêmement bas. Le résultat final de l’éco-efficience dépend également largement d’une autre composante du système cultural, celle qui réunit fabrication, distribution et contexte socio-technique. Les systèmes culturaux à faible niveau d’intrants ne sont pas plus éco-efficients en soi que l’agriculture intensive. Cependant, avec une bonne organisation, ils peuvent avoir des performances similaires ou supérieures. Bien que certains facteurs limitants soient indépendants de l’agriculteur, une grande part de l’éco-efficience peut être influencée par les décisions de management spécifiques au site. Il est donc possible d’améliorer encore l’éco-efficience dans l’agriculture à faible niveau d’intrants, mais il est indispensable de réunir des informations sur l’environnement afin d’aider à prendre les bonnes décisions en termes de conception.
11 GENERAL INTRODUCTION
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13 Evolution of European cropping systems
Satisfaction of nutritional needs occupies significant portion of time and energy for all living organisms, but humans managed to reduce the required effort to the minimum. The invention of cropping systems was the first big step in this direction, allowing societies to switch from hunting and gathering towards the agriculturally based organisation. A cropping system is a part of an agricultural production system. It is defined by an area of land that is managed in a homogenous manner for plant cultivation: with the same crops, in the same rotation and using the same technical means (Sebillotte, 1990). Throughout the history, people constantly tried to increase their productivity – the amount of useful output relative to the amount of invested inputs. In the second part of the 20th century in Europe, the major and rapid improvements in land and labour productivity occurred when high yielding cultivars of wheat and hybrids of maize were developed in formal breeding programs (Kharkwal and Roy, 2004). These developments were coupled with the increased application of synthetic, water soluble fertilisers and pesticides. As a result, per hectare yields of wheat and barley in Western Europe have more than doubled between 1960s and 2000s and nearly tripled for maize (FAOSTAT, 2012b). Technological changes of the last century brought significant improvements in food security and labour productivity (Broadberry, 2009) and the area under agricultural production in Europe in the last 30 years could slightly decrease (FAOSTAT, 2013). Relatively high levels of fertilisers and pesticides applied in modern agriculture, however, raised numerous concerns over their negative externalities (Pretty et al., 2000, Pimentel et al., 1992). In 1990s, the global production of mineral, water soluble fertilisers had already been directly responsible for 1.2% of the world’s energy use and 1.2% of greenhouse gas emissions (Kongshaug, 1998). Releases of even more greenhouse gases follow their application to the fields.
Applying nitrogen, both in mineral and organic form, causes emission of nitrous oxide that is responsible for 4.8% of all anthropogenic greenhouse gas emissions (Baumert, 2005, IPCC, 2007, Smith et al., 2000).
Excessive supply of nutrients caused problems of water eutrophication and acidification in many parts of the world (Tilman et al., 2002). The excessive use of pesticides can have negative effects on human health and ecosystems (Hellweg and Geisler, 2003, RIVM, 1992). Phosphorus is constantly mined for
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agriculture in the form of the phosphate rock and its reserves are limited (Cordell et al., 2009) while global trends show further increases in the demand and supply of agricultural inputs.
Low-input cropping systems (LICS) and their environmental impacts
Concerns over the negative externalities of modern agriculture in Europe led to the renewed interested in traditional forms of farming. LICS is a part of a low-input farming system. Low-input farming system have been defined as a farming system, where consumption of “external inputs” is minimised and the use of internal resources maximised (Liebhardt et al., 1989, Parr et al., 1990, Gosme et al., 2010). In agriculture, “external inputs” are commonly understood as those coming from outside the farm: mainly fertilisers, pesticides and energy. The term “low-input farming” is often confused with
“organic farming”, but these two terms should not be used as synonyms. Organic farms can apply high quantities of organic fertilisers and plant protection products that are allowed within their certification schemes. LICSs, on the other hand, have relatively low material throughput, meaning that less physical inputs is applied per ha but also less is produced as compared to high-input systems. Low grain prices in 1990s paired with subsidies to less intensive modes of production stimulated the re-emergence of such systems in the European Union (EU). Despite lower expected yields, reducing inputs has been shown to allow European farmers maintaining their incomes (Loyce et al., 2012, Bouchard et al., 2008). This is partly due to reduced costs and partly that many farmers practicing low-input agriculture in Europe cultivate rare crops or ancient varieties profiting from price premiums that consumers are willing to pay for these foods (Piergiovanni, 2013, Bouchard et al., 2008). The European Environment Agency defines low-input farms in Europe as those spending less than €80 ha−1a−1 on fertilizers, crop protection and concentrated feedstuffs (EEA, 2005). It has been estimated, that the share of such farms within the total agricultural area of the EU-12 increased from 26% to 28% between 1990 and 2010 (EEA, 2005). Low- input systems have been supported by the European Common Agricultural Policy, largely based on the assumption that negative environmental impacts of arable intensification (Tilman et al., 2002, Stoate et al., 2001) can be reduced by switching to less intensive methods of farming. However, broader environmental consequences from switching back to low-input farming methods remain unclear. LICSs have been shown to cause less damage to vascular plant richness than high-input agriculture (Kleijn et
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al., 2009), although there are species of animals that prefer higher-intensity landscapes (Kleijn et al., 2001). Hodgson et al. (2010) demonstrated that benefits from increasing intensity in part of the agricultural landscape and sparing a fraction of land for biodiversity can be higher than low-intensity farming over the whole area. Tuomisto (2012b) arrived at the opposite conclusions, showing benefits of low-input farming even if the saved land, would be used for other uses, including the natural woodlands. There is evidence that the systematic use of techniques such as manuring, mulching and cover cropping which are practiced in LICSs can help to build up the lost soil organic matter (Johnston et al., 2009, Buyanovsky and Wagner, 1998), and therefore potentially provide carbon sequestration benefits. On the other hand, a relatively high amount of organic matter needs to be systematically applied to increase the soil carbon (Johnston et al., 2009) and this biomass needs to be produced somewhere else. Furthermore, there is an evidence of correlation between the level of nitrogen in the soil and the amount of soil organic matter (Conant et al., 2005). The shortage of nutrients within the LICS may stimulate the microbial communities, what enhances the decomposition of soil carbon and actually increase the release of CO2 instead of sequestering it (Leifeld, 2013). LICSs are also producing less food as compared to high-input agriculture. Rapid increases in food prices on the global market between 2005 and 2011 brought productivity issues back on political and research agendas. Even though the production of food in the European Union currently exceeds the needs of its citizens, questions arise about opportunity costs of low-input farming. It has been estimated, that the global agricultural production will have to increase by 70-100% in the near future to address the needs of growing and increasingly wealthy world population (Bruinsma, 2009, HM Government, 2011, Royal Society, 2009, Godfray et al., 2010). Given the fact that 18% of global anthropogenic greenhouse gas emissions is already attributed to land conversions (Baumert, 2005) there is a strong case for increasing production on the existing land to avoid further conversion of non-agricultural land and all the resulting negative environmental consequences. Model projections suggest that production increases on the existing land will have to be coupled in the future with significant reductions of impacts that agricultural systems have on the environment. This is due to the fact that emissions from today’s intensive (high- input) systems, if scaled up, would go beyond the capacity of the Earth to absorb them (Foley et al.,
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2011, Godfray, 2011, Tilman et al., 2011). This creates the need for developing new farming systems with higher levels of productivity per unit of land but lower impacts on the environment.
The concept of eco-efficiency and its relevance to agricultural systems
Relationships between levels of production and environmental impacts of a production system can be described by its eco-efficiency. World Business Council for Sustainable Development defined eco- efficiency as being achieved by the provision of “competitively priced goods and services that satisfy human needs and bring quality of life, while progressively reducing ecological impacts and resource intensity throughout the life cycle, to a level at least in line with the Earth’s estimated carrying capacity”
(Schmidheiny, 1992). Large-scale improvements in eco-efficiency of businesses present one of the visions for the transition of global society towards sustainability (Elkington, 1998, Hawken et al., 2010).
Huppes and Ishikawa (2005) distinguished four basic types of eco-efficiency (Table 1). In this thesis, under the term improving eco-efficiency I understand reducing environmental intensity of a production system or increasing environmental productivity. The extent to which eco-efficiency of current economic systems will have to be improved over the next 40 years has been intensively debated since 1970s (Reijnders, 1998). Model predictions have produced variable but always significant numbers with estimates varying between factor 4 and 50. From the macro-economic perspective, food and agriculture in high-income countries are among the least eco-efficient sectors of the economy. Consumption of agricultural products is already responsible for 20% to 50% of all major environmental impacts (Tukker et al., 2006), while the value added by agricultural production in industrialised economies accounts for less than 3 % of GDP (World Bank, 2013). Food is a basic human need and maintaining the production of diverse and nutritious products is an imperative of food security. There is therefore a strong case for improving the eco-efficiency of agricultural systems and in particular, the food production eco- efficiency.
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Table 1. Four basic types of eco-efficiency according to Huppes and Ishikawa (2005).
Environmental productivity:
Production value per unit of environmental impact
Improvement cost:
Cost per unit of environmental improvement Environmental intensity:
Environmental impact per unit of production value
Environmental cost-effectiveness:
Environmental improvement per unit of cost)
Methods for measuring eco-efficiency that can be applied to agriculture
The use of various methods has been reported in the previous literature for measuring eco-efficiency in agriculture, including approaches such as Data Envelopment Analysis (Beltran-Esteve et al., 2012, Picazo-Tadeo et al., 2011, Shortall and Barnes, 2013, Azad and Ancev, 2010), accounting of nitrogen or nutrient use efficiencies (Carberry et al., 2013, Kuosmanen and Kuosmanen, 2013, Tilman et al., 2001) or Life Cycle Assessment (Jan et al., 2012). Life Cycle Assessment (LCA) is a method that allows to consider the broadest system boundary and the broadest range of environmental impacts (Finnveden and Moberg, 2005). The use of holistic methods and consideration of the widest possible scales and timeframes is necessary for the fair assessment of all production systems, but agricultural systems in particular. Environmental impacts from agriculture have spatial rather than point or linear character and are highly dispersed. Taking nitrous oxide emissions as an example, the production of adipic acid that is used in nylon production is the single biggest industrial source of nitrous oxide emissions, with all world emissions coming from only 255 to 600 point sources. Nitrous oxide emissions measured at any given point in the fields are relatively small. Nevertheless, the global area of farmland makes agriculture responsible for the majority of this greenhouse gas’s emission while industry including nylon production makes up only 20% (Penman et al., 2000). The second reason is that considering the broad range of environmental impacts is necessary to avoid burden shifting. The relationship between carbon footprint and pesticide application presents an illustrative example. The production and application of glyphosate is not particularly greenhouse gas intensive (Hischier et al., 2010), cropping systems with glyphosate applications can therefore be characterised by lower GWP per product unit than those with low or no
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use of pesticides if the pesticide application allows for some yield increase. However, following their release to the environment, pesticides have negative effects on human toxicity and ecosystems what is not incorporated in carbon footprint but would be revealed in toxicity-related impact categories (Hellweg and Geisler, 2003). The application of Life Cycle Assessment is regulated by international standards (ISO, 2006a, ISO, 2006b) and several voluntary initiatives throughout the agri-food sector have been undertaken to further unify the procedure and reduce the uncertainty of derived results, such as the ENVI-FOOD protocol (Camillo et al., 2012).
The role of design in improving eco-efficiency
The first environmental policies were directed at preventing some specific emissions from entering the environment or cleaning up those that have entered it (so-called “end-of-pipe” solutions). Today, it is recognised that most of the environmental impacts of products, services and systems can be addressed before the harmful substances are released or even formulated - through interventions at the design stage (Graedel and Allenby, 1995). Ecodesign can be defined as a development process considering complete life cycle of a product or service, where environmental impacts at all stages of the life cycle are addressed to develop products and services with the lowest possible environmental impacts (Glavič and Lukman, 2007, ISO/TR14062, 2002). Brezet (1997) distinguished four types of ecodesign innovations, depending on the extent of changes: i.) product improvement, ii.) redesign, iii.) product function and iv) system innovation. Product function innovation is not restricted to the product itself, but the way its function is fulfilled, while system innovation includes changes in the entire technological system (products, supply chains, infrastructure and institutional networks). Ecodesign support tools based on LCA are increasingly applied in industry with the aim of reducing environmental impacts of products, so far mostly by large firms and specifically from the electric and electronic sectors (Kobayashi et al., 2005, Aoe, 2007, Toshiba, 2012, Takagi, 2000, Saling et al., 2002, Knight and Jenkins, 2009). LCA- based eco-design tools have also been used by companies from the agri-food sector (Schenker and Lundquist, 2010, Dutilh, 1998) but innovations at the agricultural stage remain rarely reported, despite the significance of impacts that agricultural systems have on the environment. McDevitt and Milà i Canals (2011) used LCA to identify breeding priorities for UK oat that would lead to the highest
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reductions of environmental impacts along the whole product life cycle. This led to the conclusion, that some of the biggest environmental improvements of porridge can be achieved by modifying crop viscosity and flake liquid absorption and the reduction of cooking time. De Jonge (2004) evaluated eco- efficiency improvement of fungicide by the internal Research and Development (R&D) investments of a chemical company, demonstrating threefold reduction in life cycle human toxicity over time, eightfold in terrestrial eco-toxicity and sevenfold in aquatic eco-toxicity while providing the same crop protection function. Kulak et al. (2013) used LCA to identify crops that would allow for the biggest savings of greenhouse gas emissions while cultivating at the peri-urban community farm in London. The analysis showed that some crops, like beans and courgettes have the capacity to provide large reductions of greenhouse gas emissions, while others, like strawberries are better to be supplied from the conventional, supermarket-based food supply system. Hayer et al. (2012) demonstrated with the use of LCA, that the eco-efficiency of French cropping systems within the same region can be influenced by choices of cropping sequences.
Integrative approaches to eco-design
Most of the past eco-design innovations in agriculture focused on optimisation of single elements of the cropping system design, such as the pesticide (de Jonge, 2004) or a cultivar (McDevitt and Milà i Canals, 2011). However, the final environmental performance of the cropping system will be determined by multiple processes. By optimising only one component of the system in question, only incremental improvements in eco-efficiency can be achieved. Whole System Design (Integrative Design) is an approach that has its roots in the field of industrial design. It emphasises the need to look at the whole system instead of its parts to achieve significant improvements in system efficiency (Stasinopoulos et al., 2009). The concept implies the need for the integration of actors and the use of trans-disciplinary skills in a design process to provide radical improvements (Charnley et al., 2011). Case studies of application showed factor 10 improvements in energy efficiency of a building (Lovins, 2010) or radical reductions in fuel use of a hydrogen-based vehicle (Charnley et al., 2011). Anarow et al., (2003) gave Integrated Pest Management (IPM) as an example from agriculture. The approach is based on the knowledge of life cycles of pests and encourages large number of small strategic interventions that cumulatively result in
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an effective pest control. Integrated Nutrient Management can be used as another example, an approach to farm management that encourages increasing the utilisation of nutrients within cropping system and decreasing losses through utilising interactions between all the environmental components involved in nutrient cycling, as well as considering of the socio-economic aspects to ensure technology adoption (Frossard et al., 2009).
The potential role of integrative design in improving eco-efficiency of low-input cropping systems
Eco-efficiency improvement (understood as increasing environmental productivity or reducing environmental intensity as defined in Table 1) can be achieved in three ways: i.) by reducing environmental impacts while maintaining productivity, ii.) by increasing production while maintaining environmental impacts or iii.) by the combination of both approaches. Literature gives numerous examples of integrated solutions for increasing production in a cropping system in a sustainable manner (sustainable intensification). These include such approaches as Conservation Agriculture (CA) (Murray, 2012, Pretty, 2009, World Bank, 2004), diversification of species (Cassman, 1999, Murray, 2012), integrated pest and nutrient managements (FAO, 2011, Frossard et al., 2009, Murray, 2012, Pretty, 2009, World Bank, 2004), agroforestry systems (Cassman, 1999, Dore et al., 2011, FAO, 2011, Pretty, 2009), precision agriculture (Cassman, 1999, World Bank, 2004), reintegrating crop and livestock production (Dore et al., 2011, FAO, 2011, Pretty, 2009, Pretty, 2011, Vayssières et al., 2011) or mixing cultivars and species (Dore et al., 2011, FAO, 2011). The current literature however lacks critical, systematic assessments of their performance. The cases of local food (Edwards-Jones et al., 2008) or organic food (Tuomisto et al., 2012b) demonstrated that human perceptions of what sustainable systems might look like can be different to the picture shown by the quantification of resource flows.
21 Goal and objectives of the thesis
The goals of this study were twofold: i.) to assess the eco-efficiency of low-input cropping systems in Europe in relation to standard methods of production and ii.) to quantify the potential improvements that can be achieved through the application of integrative design approach supported by LCA.
The study had following objectives to fulfil these goals:
1. To review the existing evidence on the ratio of production to environmental impacts in European low-input cropping systems and strategies that can bring improvements.
2. To quantify environmental impacts of products from several real-life low-input cropping systems and to compare these systems to current patterns of crop production in Europe.
3. To develop and apply a new methodology coupling benefits of integrative approaches to cropping system design and LCA and to quantify the improvement potential in case study systems.
22 Structure of the thesis
The thesis consists of three chapters and a general discussion.
Chapter one addresses the first objective of the research project. This chapter provides a review of literature on relationships between the reduction of external inputs to cropping systems and their eco- efficiency, measured as the ratio of environmental impacts assessed by LCA to the quantity of product.
The second chapter addresses the second objective. It describes the application of product LCA to evaluate eco-efficiency of several low-input producers from Europe aiming at implementing eco- innovations at the level of food supply chain and at producing bread with low environmental impacts.
Results per kg of bread at the consumer table are compared to product equivalents from supermarket- based supply chains.
The third chapter addresses the third objective. It describes the methodology that can be applied for improving eco-efficiency of farming systems based on the collaboration of researchers and farmers and the use of LCA as an information support tool. The application of methodology was tested through collaboration with two producers from France. In the method, LCA allows to locate hot-spots requiring the greatest attention to improve environmental performance and new ideas are generated through interdisciplinary discussions. The stakeholder feedback allows ruling out the solutions that would not be accepted by producers and their customers.
The three chapters are followed by a cross-sectional discussion. It starts by highlighting the contributions of the thesis to the current state of knowledge. This is followed by the discussion on limitations of different aspects of the method that can be improved in the future as well as its advantages. The thesis is summarised by concluding remarks.
23 CHAPTER 1.
HOW ECO-EFFICIENT ARE LOW-INPUT CROPPING SYSTEMS IN WESTERN EUROPE AND WHAT CAN BE DONE TO IMPROVE THEIR ECO-EFFICIENCY?
This chapter is an adapted version of the following publication:
KULAK, M., NEMECEK, T., FROSSARD, E. & GAILLARD, G. 2013. How Eco-Efficient Are Low-Input Cropping Systems in Western Europe, and What Can Be Done to Improve Their Eco-Efficiency? Sustainability, 5, 3722-3743.
24
25 1. Introduction
Common Agricultural Policy and a number of national policies were introduced in XXth century Europe to increase food security. This goal has been achieved with remarkable success in the western part of the continent, where it has been paired with the rapid economic growth. Today, Western Europe is one of the world’s most agriculturally productive regions, whose mean wheat yield between 1990 and 2011 was 2.5 times higher than the global average, and almost 3 times higher than Eastern Europe’s (FAOSTAT, 2013). Agricultural developments significantly increased land productivity whilst reducing labour requirements (Eurostat, 2013). These productivity gains, however, were achieved at some external cost. It is well recognised that agricultural intensification was coupled with the increased use of synthetic fertilisers, pesticides and irrigation water, and that this created a number of sustainability challenges (Stoate et al., 2001, Tilman et al., 2002). Concerns over the nutrient pollution and loss of ecosystem services caused by intensive production resulted in a renewed interest in, and public support for, more extensive modes of production, such as LICSs. Although losses from pests and diseases in LICSs can be partially mitigated by cultivating crops and varieties that have higher resistance (Loyce et al., 2012), overall yield is expected to be lower because of the lower absolute yield potential (Gosme et al., 2010).
Due to the concerns over the ability of humanity to feed itself in the future, researchers from the Food and Agriculture Organization of the United Nations (FAO) and a number of other organisations called for an increase in global food production on existing agricultural land with a simultaneous reduction of its impacts on the environment (IAASTD, 2009, Royal Society, 2009, Murray, 2012, HM Government, 2011). The term ‘intensification’ emphasises the necessity of achieving productivity increases, but global sustainable intensification (SI) does not mean that yields must be increased in all regions (Garnett et al., 2013). Western Europe is among the few areas in the world with relatively high levels of food security and the highest levels of domestic supply quantity of agricultural goods (FAOSTAT, 2012a). As intensive agricultural systems have already caused significant damage to the environment in this region (Stoate et al., 2001), it is therefore reasonable to seek for improvements in eco-efficiency of European agriculture rather than further sole yield increases.
26 The objectives of this chapter are twofold:
1) to review the evidence from LCA regarding the effect of reducing agricultural inputs on eco-efficiency;
and
2.) to identify interventions for improving eco-efficiency of LICSs.
Eco-efficiency can be expressed in quantitative terms as a relationship between environmental impact and the production value (Table 1). In this study, we looked at the changes in the quantity of product, assuming that the rate of change in product quantity at a constant price will correspond to the rate of change in monetary value. At present, Life Cycle Assessment (LCA) is the most standardised and widely applied method allowing to quantify environmental impacts of products, services and activities throughout their life cycles (Finnveden et al., 2009). LCA can be applied to evaluate cropping systems by using the ratio of quantitative environmental indicators to productive functional units, thereby allowing the systematic comparison of eco-efficiency between systems. LCA is widely applied in the agri-food sector (Corson and Van der Werf, 2012) with the most common use being the comparison of environmental impacts at farm scale between organic and conventional farming systems, as illustrated in a recent meta-analysis dedicated to this subject (Tuomisto et al., 2012b). To date, far less research has been devoted to the evaluation of cropping systems with different levels of external inputs, and to identifying practical solutions for their improvement.
2. Methodology
Goal and scope definition is the first step of every LCA study (ISO, 2006a), as it determines the assumptions and methodological choices. For the purpose of achieving the first objective of this chapter, we selected studies that were solely dedicated to comparing cropping systems at different fertilisation levels. Since LCAs are spatially explicit (Roches et al., 2010), we included only those with the study subject located in Western Europe. In Haas et al.’s study (2001), we excluded the impact categories of biodiversity, landscape image and animal husbandry, since these were expressed per farm, and were therefore not related to any uniform product-related functional unit that would allow to make
27
conclusions over eco-efficiency. We also excluded results for the impact categories of groundwater quality and surface-water quality, as they were calculated as a function of nutrient use, and hence provided no additional information to the impact category ‘eutrophication’. Due to the differing approaches that were used across studies to characterise land-use impacts, we used the impact category “land occupation” to ensure comparability. Defined as the surface area of agricultural land that must be occupied for one year to deliver the given functional unit, land occupation was calculated on the basis of yield. To better illustrate the relationship between external input levels and eco-efficiency, we compiled LCA results for bread-wheat production from two independent studies (Brentrup et al., 2004, Nemecek et al., 2011a,b) in a graphic form. To allow comparability, original eutrophication units from Nemecek et al. (2011a,b) which were nitrogen equivalents were converted to phosphorus equivalents using conversion factors from Hauschild and Wenzel (1998). We also employed Agri-LCI models from Cranfield University (Williams et al., 2006, Cranfield University, 2006) to estimate the environmental impacts of wheat production in the UK at fertilisation levels corresponding to those of Brentrup et al. (2004), and included these results for comparison. The list of potential strategies for improving eco-efficiency was compiled from review articles on sustainable intensification (FAO, 2011, Flavell, 2010, Royal Society, 2009, Murray, 2012, World Bank, 2004, Pretty, 2009, Cassman, 1999, Dore et al., 2011, Pretty, 1997, Vayssières et al., 2011), and those for which LCA studies could be found were included in the review. Based on previous knowledge, we supplemented the list with nutrient-recycling technologies. It is worth mentioning that the list of techniques reviewed in this chapter is exemplary, and other, more effective techniques may exist for improving cropping system eco-efficiency. We used Agri-LCI models to simulate the consequences of reduction in tillage. For simplicity’s sake, we limited the comparison to one impact category (‘net greenhouse-gas balance’) while discussing the environmental impacts of various feedstocks for anaerobic digestion. In the final part of the chapter, we addressed some limitations of LCA methodology for assessing the performance of low-input systems.
28 3. Environmental impacts of LICSs
Table 2 gives an overview of LCA studies from Western Europe on cropping systems with different levels of external inputs. The study of Haas et al. (2001) showed a reduction in all environmental impacts except for land occupation per tonne of harvested grass when external input levels were reduced. However, the relative differences in mean yield in the study were relatively low:
11.8 t ha-1 in the intensive, 10.5 t ha-1 in the extensified and 10.7 t ha-1 in the organic system. Although it is known that mineral fertilisers were used in the intensive and not in the extensified and organic systems, the rates of application of organic fertilisers were not reported. Brentrup et al.'s study (2004) was based on a long-term field trial from the Rothamsted research station in the UK. Environmental impacts at seven different nitrogen (N) fertilisation levels were investigated, from 0 to 288 kg N ha-1, with other inputs kept at constant rates. Environmental impacts per tonne of wheat were shown to decrease here proportionally to decreasing levels of N for two of the analysed impact categories: ‘Global Warming Potential’ and ‘Eutrophication Potential’. Despite this, energy use and acidification were shown to decrease and increase again when levels of N were too low. At a very high fertilisation level, land occupation could be reduced by reducing N, but was generally observed to be increasing together with reduced inputs due to reduced yields. Charles et. al. (2006) performed a study in Switzerland in which four fertilisation treatments for wheat were analysed: 100 kg N ha-1,140 kg N ha-1,180 kg N ha-1, and 220 kg N ha-1, with P and K adjusted proportionally to nitrogen levels. All impact categories except for land occupation, eutrophication and aquatic ecotoxicity were shown to decrease per tonne of wheat grain when N was reduced. Functional unit (FU) represents the function (product or service) of the analysed system, based on which the comparison in LCA study is made (ISO, 2006a). When 1 t of wheat with constant protein content was used as a FU, nearly all environmental impacts increased along with a reduction in N, owing to the positive relationship between N fertilisation and protein content of grains.
Nemecek et al., (2011b) showed that all impact categories except for land occupation were reduced or unaffected in a cash-crop rotation and a feed-crop rotation. In the grassland systems investigated, however, energy use, acidification, eutrophication, aquatic ecotoxicity, terrestrial ecotoxicity and human toxicity all increased along with a reduction in fertilisation, and decreased again at very low levels of
29
fertilisation, while for ozone formation and the Global Warming Potential (GWP) the opposite result was found -the highest environmental impacts were at the highest and lowest fertilisation levels. Modelled cropping systems for winter wheat and barley showed increases per product unit for nearly all impact categories considered, except for those related to toxicity, and – in the case of rapeseed – ozone formation. When ‘Swiss Franc of revenue’ was used as a FU, the result was more favourable for low- input production, partially owing to the direct payments for this type of cultivation in Switzerland.
Glendining et al., (2009) coupled LCA models from Williams et al., (2006) with the economic valuation of ecosystem services. The starting point of the analysis was current levels of intensity in the UK, and several scenarios for nationwide reductions in inputs to wheat production were examined. The study showed that environmental damage to ecosystem services will increase for all products analysed if farmers in the UK reduce input levels. This was owed to increasing land requirements, and agricultural land use was assigned a high environmental cost due to the potential damage caused to natural ecosystems in case of agricultural expansion. Goglio et al., (2012) investigated cropping systems for first- generation bioenergy production with different levels of external inputs in Italy, showing that environmental impacts per MJ of energy produced can be lowest at low levels of external inputs.
Figure 1 illustrates the relationships between nitrogen application to bread wheat and environmental impacts per tonne of harvested grain across different studies. It is worth mentioning that wheat has a strong response to N fertilisation, and results for less N demanding crops would probably be more favourable for low-input production. The results from both Williams et al. (2006) and Brentrup et al. (2004) reveal an optimum point for energy use at the moderate application rates, between 100 and 200 kg, although there is a difference of a factor of 2 between the absolute values. Both studies show that reducing or increasing nitrogen below or above an optimum level will cause diminishing of eco-efficiency. Nemecek et al. (2011b) revealed a reduction in energy demand with increased fertilisation rates, although the absolute levels of applied nitrogen remained below 200 kg N ha-1. There is a clear difference between organic and mineral fertilisation, with the latter being characterised by higher energy demand. Brentrup et al. (2004) revealed a close-to-linear relationship between increased nitrogen levels and GWP, while in Williams et al. (2006) GWP remains constant at lower levels, followed by a rapid increase at higher levels of fertilisation. Large differences between studies at lower
30
fertilisation levels are presumably due to differences in modelling assumptions for greenhouse-gas emissions from unfertilised soils. Although more dispersed, results of Nemecek et. al. (2011b) show increases along with increased fertilisation. In both Williams et al. (2006) and Brentrup et al. (2004), the eutrophication potential appears to remain steady or decrease slightly with increasing fertilisation at lower rates, then increase at higher rates above 200 kg N per ha. Nemecek et al.’s (2011b) results show a much higher Eutrophication Potential for organic fertilisation. Although Acidification Potential increases proportionally to nitrogen application in Williams et al.'s model (2006), according to Brentrup et al. (2004) it decreases slightly before increasing again. Nemecek et al.'s study (2011b) reveals higher results for the organically fertilised cases. The non-linearity of results shows the importance of factors other than quantity of N for eco-efficiency results.
31
Table 2: Effects of reducing external inputs on LCA results for agricultural products (GWP = Global Warming Potential; AP = Acidification Potential; EP = Eutrophication Potential; AEP = Aquatic Ecotoxicity Potential; TEP = Terrestrial Ecotoxicity Potential; DM = dry matter; ns = non-significant; incr. = increased; red. = reduced)
Goal of
study
Cou ntry
Crop Input data
Type of input tested
Product related functional unit
Effect of reducing inputs on Life Cycle Impact categories Energy use Land
occupatio n
GWP AP EP Ozone
formation
AEP TEP Human
toxicity Env.
cost Haas et al.
(2001)
To compare intensive, extensified and organic grassland farming
DE Hay Represe-
ntative farms
Fertilising, stocking rate
1 t DM red. incr./
red.
red. red. red.
Brentrup et al.
(2004)
To examine different intensity levels (as N application rates)
UK Winter wheat
Field trials
Nitrogen input
1 t wheat red./
incr.
red./
incr.
red. red./
incr.
red.
Charles et al., (2006)
To estimate environment ally optimum fertilisation intensity
CH Winter wheat
Field trials
Fertilisers 1 t wheat red. incr. red. red. incr. red. incr. red. red.
1 t pr.
adjusted wheat*
incr. incr. incr./red. incr. incr. incr. incr. red. red.
Nemecek et al., (2011b)
To examine effects of reduced fertilisation, plant- protection and soil- cultivation intensity (frequency of operations)
CH Cash- crop rotation
Field trials
Fertilisers 1 kg DM red. incr. red. ns Ns ns red. red. red.
Feed- crop rotation
Field trials
Fertilisers 1 kg DM red. incr. red. ns red. red. ns ns ns
Hay Field
trials
Number of cuts, nitrogen input
1 MJ incr./
red.
incr. red./
incr.
/red.
incr./red. incr./
red.
red./
incr./red.
incr./red. incr.
/red.
incr./re d.
Winter wheat
Modelle d system
Pesticide 1 kg DM incr. incr. incr. incr. incr. incr. incr. red. red.
1 Swiss Franc
red. incr. incr. incr. incr. incr. incr. red. red.
* Wheat grain with constant protein concentration
31
32
Table 2: Effects of reducing external inputs on LCA results for agricultural products (continued from previous page). (GWP = Global Warming Potential; AP = Acidification Potential; EP = Eutrophication Potential;
AEP = Aquatic Ecotoxicity Potential; TEP = Terrestrial Ecotoxicity Potential; DM = dry matter; ns = non-significant; incr. – increased; red. – reduced) Goal of study Coun
try
Crop Input data Type of input tested
Product- related functional unit
Effect of reducing inputs on Life Cycle Impact categories Energy use Land
occupa tion
GWP AP EP Ozone
formati on
AEP TEP Human
toxicity
Env.
cost Nemecek
et al.
(2011b)
To examine effects of reduced fertilisation, plant- protection and soil- cultivation intensity (frequency of operations)
CH Winter barley
Modelled system
Pesticide 1 kg DM incr. incr. incr. incr. incr. incr. incr. red. red.
1 Swiss Franc
red. incr. incr. red. incr. ns red. red. red.
Rape- seed
Modelled system
Pesticide 1 kg DM red. incr. incr. incr. incr. red. incr. red. red.
1 Swiss Franc
red. red. red. incr. incr. red. incr. red. red.
Glendining et al.
(2009)
To estimate the optimum level of all inputs for maximising Total Factor Productivity
UK Winter wheat
Modelled scenarios
Cost 1 t grain incr.
Rape- seed,
1 t incr.
potato 1 t incr.
Goglio et al. (2012)
To evaluate environment al impacts of cropping systems for bioenergy production
IT Bioene rgy crop rotatio n
Field trials Fertilisers, pesticides
1 GJ of energy
red.** red. red. red.
** The study reports increased net energy yields together with reduced levels of inputs – a result of reduced energy use.
32
33
Fig. 1: The influence of fertilisation rates on LCA results for bread wheat across Western European studies
4. Improving eco-efficiency.
As demonstrated in the previous paragraph, when input levels are too low, improvements in eco-efficiency can be achieved by increasing them to the optimum level. The mean N fertilisation rate for arable crops in Western Europe between 2002 and 2010 was 123 kg N ha -1 (FAOSTAT, 2013). Taking wheat production as an example (Fig. 1), this appears to be within or even slightly below the optimum levels for eco-efficiency. This could lead to the conclusions that current fertiliser application levels are optimal, and that further reductions in inputs would generally increase the level of damage to ecosystem services (Glendining et al., 2009). Viewing eco-efficiency as a function of input levels, however, is an oversimplification, since inputs to the production process can also be substituted. The substitution of inputs will influence eco-efficiency, it is therefore possible to manipulate this value by switching between different types of inputs instead of
34
increasing them. Changing the crop from wheat to another crop less dependent on nitrogen fertilisation provides more output from the same rate of natural resources invested, thereby improving eco-efficiency.
4.1. Reduced tillage, conservation tillage and no-till farming
Crop-production technologies that reduce tillage and leave at least 30% of crop residues on the soil surface are referred to as conservation tillage (Jarecki and Lal, 2003). Reduction in tillage is an essential component of a wider set of practices known as Conservation Agriculture (Govaerts et al., 2009). A more specific system of sowing crops with less than 5 cm of disturbance to the soil structure and in which 30 – 100% of the soil surface is covered with plant residues is known as no-till, direct drilling or zero tillage (Soane et al., 2012). In the past, the adoption of no-till farming was believed to sequester atmospheric carbon and mitigate climate change (Lal, 2004, West and Post, 2002). Numerous LCA studies have been conducted that incorporate these effects into the greenhouse gas balance, mainly in the context of biofuel production (Kim and Dale, 2005, Borzęcka-Walker et al., 2013, Syp et al., 2012, Gelfand et al., 2013). Recently, however, these assumptions have been called into question, since no differences in carbon pool between the soil under no-till and conventional cultivation can systematically be observed when the entire soil profile is measured (Baker et al., 2007, Blanco-Canqui and Lal, 2008). Table 3 reviews the results of LCA studies on the effects of no-tillage cultivation without assuming carbon sequestration benefits. Based on the results of a field experiment conducted in Switzerland, (Nemecek et al., 2011b) showed that introducing no-till practices can reduce some environmental impacts such as human toxicity, but also increase others, like terrestrial ecotoxicity due to the necessity for the application of pesticides, and in addition may have no effect on eutrophication and GWP per product unit. The yield in the cropping-system experiment increased by 4% over that of conventional tillage, but this may be partially owing to the increase in N and P fertilisation. Williams et al., (2006) model assumes the need to increase various pesticides by 18% in order to maintain the same yield levels when adopting reduced- tillage practices. Modelling the switch from conventional to reduced-tillage practices reveals slight increases in the environmental impacts.
In Iriarte et al. ’s study (2011) on rapeseed production in Chile, no-till practices reduced ozone formation potential by 40%, but increased aquatic ecotoxicity by 650% due to the application of glyphosate. Studies conducted by Tuomisto et al. (2012a) and Van Der Werf (2004) revealed slight reductions in the environmental impacts.
All LCA studies considered here assumed no decrease in yields after the application of no-tillage systems. The adoption of these techniques could therefore be of interest to farmers, as they enable savings in diesel and labour associated with soil preparation. It should be borne in mind, however, that yields can also decline substantially following the adoption of no-tillage methods, especially when weed control by herbicides is not sufficient. Soane et al. (2012) performed a meta-analysis of experiments conducted in Europe, in which yields from no-till and plough-based farming would be compared. Their findings indicate that whilst the adoption of no-tillage in conventional agriculture can increase yields in dry regions of south-western Europe, no-till would most likely cause reductions in yield in northern Europe, with its higher annual rainfall. The key benefit of no-tillage is improved water retention of the soil. The adoption of this technique, however, requires effective weed control. This presents an important limiting factor for most European low-input farmers, especially those that have certificates of organic farming that forbid the use of synthetic pesticides.
35
Table 3. Review of LCA results for no-tillage. (GWP = Global Warming Potential; OF = Ozone Formation; EP = Eutrophication Potential; AP = Acidification Potential; AEP = Aquatic Ecotoxicity Potential; TEP = Terrestrial Ecotoxicity Potential; HT = Human Toxicity; ARU = Abiotic Resource Use; OD = Ozone Depletion; MEP = Marine Ecotoxicity Potential; RAD = Radioactive Radiation; DM = Dry Matter; ns = non- significant)
Study Countr y
Crops Function
al unit
Variables altered: Effect on impact category:
(FU) Type of tillage
Fertilisatio n
Pesticides Yield Energy use
GW P
OF EP AP AEP TEP HT ARU OD MEP RAD
Nemecek et al.
(2011b)
CH Crop rotation with wheat, silage maize, sugar beet and peas
1 t DM no-till N +7 % P +3 % K 0 %
+60% +4% -12% ns -21% ns -10% -19% +125% -31%
Williams et al.
(2006)
UK Winter wheat, average of crop rotations in the UK
1 t wheat reduced tillage
no change +18% no
change
+7% +4% +2% +3% +5%
Iriarte et al. (2011)
Chile Rapeseed 1 t
rapeseed
no-till no change 0.4 kg glyphosate in no-till;
others reduced by a factor of 4
no change
-8% +8% -40% ns +1% +650% +1% -3% -9% -15% +1% -1%
Tuomisto et al.
(2012a)
UK Winter wheat 1 t wheat reduced
tillage
no change +18% no
change
-4% -2%
no-till -14% -7%
van der Werf et al. (2004)
FR Hemp 1 ha* reduced
tillage
no change no change no change
-16% -6% -1 % -13% ns
*Change per ha corresponds to the change per product unit, as no difference in yield was considered.
35
36 4.2. Legumes and crop rotations
Crop rotation can potentially improve yields in LICSs without increasing environmental burdens. This is mainly due to two effects: i.) the elimination or reduction of crop-specific pathogens (phytosanitary effects) or weeds, and ii.) Symbiotic or Biological Nitrogen Fixation (SNF/BNF) by leguminous crops. Some legumes can also improve phosphorus availability for the plants following them in the rotation (Hocking et al., 2002, Muchane et al., 2010, Pypers et al., 2007), whilst others, such as alfalfa (Medicago sativa) can improve water uptake from the subsoil for the subsequent crops (Gaiser et al., 2012). None of these mechanisms requires the investment of additional non-renewable resources, nor do any of them cause substantial emissions to the environment. Several LCA studies evaluated the effects of introducing legumes into cropping systems (Table 4). Nemecek et al. (2008) quantified the effects of introducing peas into several crop rotations across Europe. Experiments in Germany and France showed a reduction in environmental impacts for most of the impact categories considered, due to the replacement of nitrogen fertilisers. The gross margin was also higher with grain legumes, despite the slightly lower grain yield which made these reductions even greater when quantified per financial FU. By contrast, the experiment showed an increase in GWP, eutrophication potential, terrestrial ecotoxicity, human toxicity, and land use per unit of harvested dry matter. This was because of the combined effect of lower physical yield from introduced crops and increased nitrate leaching. Nevertheless, most of the impact categories showed net reductions when quantified per unit of gross margin, owing to the higher financial yield. In a cropping system used in Spain, grain legumes were introduced into low-input crop rotation with sunflower. This led to increases in most of the environmental impacts considered, since no mineral fertiliser was replaced in the process. In one of the modelled scenarios, Tuomisto et al., (2012a) demonstrated that replacing all mineral fertiliser by leys in conventional crop rotation in the UK would reduce energy demand by 40% and GWP by 26%, despite the reduction in absolute grain yield.
As previously mentioned, the ability of leguminous crops to fix nitrogen is not the only benefit of growing crops in rotation.
Numerous experiments have shown that soybean yields are increased when this crop is grown in rotation with non-leguminous crops (Chen et al., 2001, Crookston et al., 1991, Howard et al., 1998, Long and Todd, 2001, West et al., 1996). Changing from soybean to another crop breaks the lifecycle of soybean cyst nematodes. Crop rotation was also shown to suppress ‘take-all’, a major disease of wheat caused by the pathogen Gaeumannomyces graminis var tritici (Kirkegaard et al., 2008) and responsible for losses in temperate climates. Some wheat pathogens such as Rhizoctonia solani, however, have a wide host range (Cook et al., 2002), and not all other crops will be effective in suppressing them. There are also pathogens such as Bipolaris sorokiniana that require several years without the host plant to be effective (Kirkegaard et al., 2008).
