Energetic assessment of the agricultural production system. A review

Abstract

Energy holds a key role in farm systems. Cultivation is based on the conversion of solar energy into biomass of interest. Fossil energy allows mechanized and high-yield agricultural production system, but has a strong impact on climate change, and its supply is compromised in the next decades. Energy flows stand between two worlds: while energy is a strategic component of the economy, it is also a thermodynamic state variable for describing ecosystems. This situation reemphasizes the need for energy flow analysis in farm systems. There is a great variety in the approaches used to compute energy flows at farm scales. Yet, their main characteristics and the ways they handle farm sustainability issues need to be clarified. This review identifies ten kinds of energetic approaches, i.e., (i) conventional energy analysis, (ii) pluri-energy analysis, (iii) agroecological energy analysis, (iv) exergy analysis, (v) cumulative exergy consumption, (vi) extended exergy account, (vii) cumulative exergy extraction from the natural environment, (viii) eco-exergy, (ix) cosmic exergy analysis, and (x) emergy assessment. These approaches are analyzed through key features to discuss their ability to address resources' efficiency issues and identify promising outcomes for energy assessment of farms. This analysis emphasizes the lack of clear definition of system boundaries in farm-scale studies. In addition, most of the studies mainly focus on socio-economic flows through a sectoral perspective. Yet, internal biomass flows that play a role in maintaining agroecosystem functionality can also be considered according to a circular/systemic perspective. Then, integration of soil organic matter in the energy balance leads to significant changes in energy efficiency evaluation playing a function of biotic energy storage in the farm system. Hence, some recommendations are provided to perform an exhaustive energetic assessment of farm systems as well as future lines of research to be investigated.

Historical Transition of a Farming System towards Industrialization: A Danish Agricultural Case Study Comparing Sustainability in the 1840s and 2019

“…Thus, modelling the KE system, the system boundaries as defined by the funds and flows accounting for the energy transformation and circulation from an agroecological perspective, as described by Díez, Cussó [6]. The main stocks present in the KE system are a crop livestock system based on historical and current data, with subsystems allowing for the presence of internal flows of energy as described by Hercher-Pasteur, Loiseau [20]. The farmer as the manager or steward of the agroecosystem is part of the external input to the farming system, together with inputs in form of fertilizer, fuel, electricity, heating, and fodder for livestock production.…”

“…Furthermore, as described by Tello, Galán, Cunfer et al [52], manure as energy (calculations based on Danish numbers, see [53]) recycled in the system, is also part of the internal flows on this Danish farm. Even if many industrialized system studies exclude human labor [20], the human labor is included in this study, both to enquire about the difference between the KE 1840 and KE 2019 system, but also because, without human labor, there would be no production.…”

“…In the second part, the energetic indicators used by Hercher-Pasteur, Loiseau [20], with an anthropic consideration of the system, are regarded as an important qualitative approach to compare sustainability in the system over time. More concrete, the methodology we used follows the flow-fund approach, describing the relationships between elements contributing to the agricultural system as proposed and developed by Cattaneo, Marull [32], including the adoption of the social metabolism concept [32,54].…”

“…The particularly great economic success of the conversion of Danish agriculture to animal production can be found in the design and distribution of the cooperative dairy movement [17]. Since the industrial revolution, innovations such as modern machinery and inorganic fertilizers have helped to reduce the labor force, or even appropriated human labor and draft animals [6,18,19], but at the same time resulted in a dependency between human activity and fossil energy use to maintain agricultural systems [18][19][20]. These system changes came along with broader societal change, altogether constituting a new phase of Danish social ecology [21].…”

Analysis of methodological bases of energy-economic assessment of agricultural technologies and projects

“…Due to the climatic features of most regions of the country, more than 1 million tons of fuel is spent on heating rooms and drying agricultural products. The total energy costs for the production of 1 ton of conventional grain unit in Russia in comparison with the United States are more than 5 times higher [1][2][3][4][5]. This alone significantly reduces the potential for competitiveness of agricultural products of Russian farmers.…”