Co-design and ex ante assessment of cropping system prototypes including energy crops in Eastern France

Highlights

• Cropping systems including Miscanthus x giganteus showed the lowest GHG emissions.

• For high crop prices, cropping systems with food/feed crops were the most profitable.

• NoMisc prototype includes pluriannual/annual energy crops and annual food/feed crops.

• NoMisc prototype achieved the best trade-off between food and environmental issues.

Abstract

Producing biofuels from crops is controversial due to environmental issues and to food security threats linked with the dedication of land to energy crops rather than to food production. The 2009 European Renewable Energy Directive defined the reduction of greenhouse gas (GHG) emissions as an essential requirement for biofuels. Whatever their specific lifespans, energy crops have short- and long-term effects on the following crops, thus requiring assessment at cropping system level, which is rarely done in the literature.

This study aimed at designing and assessing cropping system prototypes (CSP) that include energy crops and food/feed crops in Bourgogne (France), before being implemented in the field (i.e. ex ante). CSP were first designed, using a prototyping approach involving scientists and farm advisors, and then ex ante assessed, using indicators covering the environment, energy, economic and food issues. They were compared with two cropping systems based on food/feed crops. Lastly, we analyzed the sensitivity of the CSP profitability to several scenarios of crop yields and prices (i.e. grain and forage prices for food and feed crops respectively).

CSP including Miscanthus x giganteus performed better in terms of GHG emissions, energy costs, nitrate losses and pesticide use than CSP that include only annual crops requiring more inputs, but achieved lower profitability and food production capacity. The cropping systems including only food/feed crops frequently achieved higher economic outcomes and food production capacity. Lastly, CSP combining pluriannual or annual energy crops and annual food/feed crops showed satisfactory trade-offs among environmental impacts and food production capacity.

Introduction

The production of biofuels from crops is criticized due to its environmental impact [[1], [2], [3], [4]] and to the food security threats [5] linked with the dedication of land to bioenergy rather than to food production. As a result, the European Union enforced sustainability criteria on biofuel production [6]. In particular, biofuels must release 35% less greenhouse gas (GHG), including losses in soil organic carbon (SOC), than the fossil fuels they replace. Moreover, the agricultural feedstock used to produce biofuels must satisfy European regulations aimed at reducing local environmental impacts such as nitrate losses.

Several studies dealing with energy and GHG emissions showed that bioenergy crops, such as giant reed (Arundo donax) or Miscanthus x giganteus, outperformed food crops [[7], [8], [9], [10], [11], [12]]. However, sensitivity analyses revealed a strong influence of yield estimates on profitability [13], land requirement [11], crop production costs [14], energy yields [15] and GHG emissions per ton of dry matter [15,16]. As observed for other crops, these studies used different methods and data for assessment. For instance, the yield of Miscanthus x giganteus (hereafter referred to as M. giganteus) either was drawn from experimental data [7,[10], [11], [12],17,18], or was estimated using models [9,14,[19], [20], [21]]. However, Lesur-Dumoulin et al. [22] reported that M. giganteus yields from commercial fields were lower and more variable than those obtained in experiments because of low shoot densities at the end of the establishment year, thus weakening previous assessment results.

In these studies, bioenergy crops were rarely considered as part of a cropping system, which is defined as the crop sequence (i.e. the order of apparition of crops in a field over a period of years, for instance corn followed by soybean) and the management techniques (e.g. cultivar choice, insect control strategy) for each crop in the crop sequence [23]. The introduction of a crop and its management in the cropping system indeed generate short-term effects on the following crop and long-term effects [[24], [25], [26]]. For example, after the removal of M. giganteus, tilling is lower in the following winter wheat (Triticum aestivum L.) crop than in a crop sequence based on annual crops [27]. The use of cereal straw for bioenergy production also has long-term effects, such as a decrease in SOC content [28]. Lastly, the introduction of a perennial grass or a Short Rotation Coppice (SRC) after an arable cropping system resulted in increased SOC [29]. Hence, the assessment of energy crops should be improved by taking into account their short-term and long-term effects on the cropping system in which they are included [30].

In the aim of assessing cropping systems including energy crops, a preliminary step of cropping system prototypes (CSP) design is required. There are two main approaches to design innovative CSP [31]: model-based design and a prototyping approach involving experts [32,33]. In the prototyping approach, the use of knowledge from both scientists and farm advisors from extension services in the design step, and the definition of an ambitious goal that the CSP need to fulfil, make it possible to explore a broader range of innovations than in the model-based design [34,35]. To our knowledge, the prototyping approach has not been used yet to design and assess cropping systems combining food/feed crops and energy crops.

This study aimed at designing (by using a prototyping approach) and assessing CSP that include energy crops and food/feed crops in the Bourgogne region (Eastern France), before being implemented in the field (i.e. ex ante). Energy crops included dedicated (e.g. M. giganteus) and non-dedicated crops, i.e. ‘multi-purpose’ crops (such as cereals or alfalfa – Medicago sativa-), these crops being totally or partly used to produce energy.