A proposal for a workable analysis of Energy Return on Investment (EROI) in agroecosystems. Part I: Analytical approach

This paper presents a workable approach to the energy analysis of past and present agroecosystems aimed to contribute to their sustainability assessment. This analysis sees the agroecosystem as a set of energy loops between nature and society, and adopts a farm-operator standpoint at landscape level that involves setting specific system boundaries. This in turn entails a specific form to account for energy outputs as well as inputs. According to this conceptual approach, a clear distinction between Unharvested Phytomass, Land Produce and Final Produce is established, and also a sharp divide is adopted between the energy content of internal flows of Biomass Reused and external Societal Inputs when accounting for the amount of Total Inputs Consumed . Treating the conversion of solar radiation into local biomass as a gift of nature, enthalpy values of energy carriers are accounted for net Final Produce going outside as well as for Biomass Reused or Unharvested Phytomass , given that all these flows are evaluated from inside the agroecosystem. On the other hand, the external energy carriers are accounted for as embodied values by adding up direct and indirect energy carriers required to produce or deliver these Societal Inputs to the agroecosystem. The human Labour performed by the farm operators is treated as a special case of external input. It is accounted for the fraction of their energy intake devoted to perform agricultural work, by only using enthalpy or adding transport embodied values depending on the local or external origin of ingredients of the food basket. Following this line of reasoning we propose the definition of two different sets of agroecosystem’s Energy Returns On Energy Inputs (EROIs), depending on whether we use as numerator the Final Produce or the total phytomass harvested and unharvested included in the actual Net Primary Production. By comparing Final EROI with NPP act EROI we can obtain a proxy useful to assess whether the different paths taken by the energy throughputs may undermine or not biodiversity and soil fertility in agroecosystems. Then, by alternatively including or excluding Biomass Reused and External Inputs in the denominator, we split Final EROI into their respective energy returns to either internal or external inputs. This leads to a four interrelated EROIs whose meanings, shortcomings or ambiguities are examined respectively, in order to combine them all to draw the sociometabolic energy profiles of different sorts of agroecosystems along the socio-ecological transitions from traditional organic to industrial farm systems. The conceptual and quantitative relationships between the internal and external returns of Final EROI provide a method to decompose both dimensions in a way that clarifies their respective roles when comparing different agroecosystems, and reveals their capacity for increasing energy yields. This decomposition analysis also facilitates graphing their changing energy profiles through socio-ecological transitions along history. Finally, we suggest other related or derived indicators that can be useful for different purposes. With the bookkeeping proposed the energy analysis of farm systems is widened so as to highlight the role played by the biomass unharvested or internally reused in keeping the ecological services that biodiversity and soil fertility provide. This may also allow to test in agro-forest mosaics the Intermediate Disturbance Hypothesis long debated in ecology, by linking our energy analysis with landscape ecology metrics.Peer ReviewedPostprint (published version

From vineyards to feedlots: a fund-flow scanning of sociometabolic transition in the Vallès County (Catalonia) 1860-1956-1999

We analyse the changes to agricultural metabolism in four municipalities of Vallès County (Catalonia, Iberia) by accounting for their agroecosystemfunds and flows during the socioecological transition from organic to industrial farming between the late nineteenth and twentieth centuries. The choice of three different stages in this transition allows us to observe the transformation of its funds and flows over time, the links established between them and the effect on their energy profiles.We emphasize the relevance of the integration and consistency of agroecosystem funds for energy efficiency in agriculture and their role as underlying historical drivers of this socioecological transition. While readjustment to market conditions and availability and affordability of external inputs are considered the main drivers of the transition, we also highlight the role of societal energy and nutritional transitions. An analysis of advanced organic agriculture c. 1860 reveals the great effort required to reproduce soil fertility and livestock from the internal recirculation of biomass. Meanwhile, a balance between land produce and livestock densities enabled the integration of funds, with a positive impact on energy performance. The adoption of fossil fuels and synthetic fertilizers c. 1956 reduced somewhat the pressure exerted on the land by overcoming the former dependence on local biomass flows to reproduce the agroecosystem. Yet external inputs diminished sustainability. Partial dependence on external markets existed congruently with internal crop diversity and the predominance of organic over industrial farm management. A shift towards animal production and consumption led to a new specialization process c. 1999 that resulted in crop homogenization and agroecological landscape disintegration. The energy returns of this linear feed-food livestock bioconversion declined compared to earlier mixed farming. Huge energy flows driven by a globalized economy ran through this agroecosystem, provoking deep impacts at both a local and external scale

Agroecosystem energy transitions in the old and new worlds: trajectories and determinants at the regional scale

Energy efficiency in biomass production is a major challenge for a future transition to sustainable food and energy provision. This study uses methodologically consistent data on agroecosystem energy flows and different metrics of energetic efficiency from seven regional case studies in North America (USA and Canada) and Europe (Spain and Austria) to investigate energy transitions in Western agroecosystems from the late nineteenth to the late twentieth centuries. We quantify indicators such as external final energy return on investment (EFEROI, i.e., final produce per unit of external energy input), internal final EROI (IFEROI, final produce per unit of biomass reused locally), and final EROI (FEROI, final produce per unit of total inputs consumed). The transition is characterized by increasing final produce accompanied by increasing external energy inputs and stable local biomass reused. External inputs did not replace internal biomass reinvestments, but added to them. The results were declining EFEROI, stable or increasing IFEROI, and diverging trends in FEROI. The factors shaping agroecosystem energy profiles changed in the course of the transition: Under advanced organic and frontier agriculture of the late nineteenth and early twentieth centuries, population density and biogeographic conditions explained both agroecosystem productivity and energy inputs. In industrialized agroecosystems, biogeographic conditions and specific socio-economic factors influenced trends towards increased agroecosystem specialization. The share of livestock products in a region's final produce was the most important factor determining energy returns on investment

Metabolic Rift or Metabolic Shift? Dialectics, Nature, and the World-Historical Method

Abstract In the flowering of Red-Green Thought over the past two decades, metabolic rift thinking is surely one of its most colorful varieties. The metabolic rift has captured the imagination of critical environmental scholars, becoming a shorthand for capitalism’s troubled relations in the web of life. This article pursues an entwined critique and reconstruction: of metabolic rift thinking and the possibilities for a post-Cartesian perspective on historical change, the world-ecology conversation. Far from dismissing metabolic rift thinking, my intention is to affirm its dialectical core. At stake is not merely the mode of explanation within environmental sociology. The impasse of metabolic rift thinking is suggestive of wider problems across the environmental social sciences, now confronted by a double challenge. One of course is the widespread—and reasonable—sense of urgency to evolve modes of thought appropriate to an era of deepening biospheric instability. The second is the widely recognized—but inadequately internalized—understanding that humans are part of nature

A proposal for a workable analysis of Energy Return on Investment (EROI) in agroecosystems. Part I: Analytical approach

This paper presents a workable approach to the energy analysis of past and present agroecosystems aimed to contribute to their sustainability assessment. This analysis sees the agroecosystem as a set of energy loops between nature and society, and adopts a farm-operator standpoint at landscape level that involves setting specific system boundaries. This in turn entails a specific form to account for energy outputs as well as inputs. According to this conceptual approach, a clear distinction between Unharvested Phytomass, Land Produce and Final Produce is established, and also a sharp divide is adopted between the energy content of internal flows of Biomass Reused and external Societal Inputs when accounting for the amount of Total Inputs Consumed . Treating the conversion of solar radiation into local biomass as a gift of nature, enthalpy values of energy carriers are accounted for net Final Produce going outside as well as for Biomass Reused or Unharvested Phytomass , given that all these flows are evaluated from inside the agroecosystem. On the other hand, the external energy carriers are accounted for as embodied values by adding up direct and indirect energy carriers required to produce or deliver these Societal Inputs to the agroecosystem. The human Labour performed by the farm operators is treated as a special case of external input. It is accounted for the fraction of their energy intake devoted to perform agricultural work, by only using enthalpy or adding transport embodied values depending on the local or external origin of ingredients of the food basket. Following this line of reasoning we propose the definition of two different sets of agroecosystem’s Energy Returns On Energy Inputs (EROIs), depending on whether we use as numerator the Final Produce or the total phytomass harvested and unharvested included in the actual Net Primary Production. By comparing Final EROI with NPP act EROI we can obtain a proxy useful to assess whether the different paths taken by the energy throughputs may undermine or not biodiversity and soil fertility in agroecosystems. Then, by alternatively including or excluding Biomass Reused and External Inputs in the denominator, we split Final EROI into their respective energy returns to either internal or external inputs. This leads to a four interrelated EROIs whose meanings, shortcomings or ambiguities are examined respectively, in order to combine them all to draw the sociometabolic energy profiles of different sorts of agroecosystems along the socio-ecological transitions from traditional organic to industrial farm systems. The conceptual and quantitative relationships between the internal and external returns of Final EROI provide a method to decompose both dimensions in a way that clarifies their respective roles when comparing different agroecosystems, and reveals their capacity for increasing energy yields. This decomposition analysis also facilitates graphing their changing energy profiles through socio-ecological transitions along history. Finally, we suggest other related or derived indicators that can be useful for different purposes. With the bookkeeping proposed the energy analysis of farm systems is widened so as to highlight the role played by the biomass unharvested or internally reused in keeping the ecological services that biodiversity and soil fertility provide. This may also allow to test in agro-forest mosaics the Intermediate Disturbance Hypothesis long debated in ecology, by linking our energy analysis with landscape ecology metrics.Peer Reviewe

Opening the black box of energy throughputs in farm systems: a decomposition analysis between the energy returns to external inputs, internal biomass reuses and total inputs consumed (the Vallès County, Catalonia, c.1860 and 1999)

We present an energy analysis of past and present farm systems aimed to contribute to their sustainability assessment. Looking at agroecosystems as a set of energy loops between nature and society, and adopting a farm-operator standpoint at landscape level to set the system boundaries, enthalpy values of energy carriers are accounted for net Final Produce going outside as well as for Biomass Reused cycling inside, and External Inputs are accounted using embodied values. Human Labour is accounted for the fraction of the energy intake of labouring people devoted to perform farm work, considering the local or external origin of their food basket. In this approach the proportion of internal Biomass Reused becomes a hallmark of organic farm systems that tend to save External Inputs, whereas industrial farming and livestock breeding in feedlots tend to get rid of reuses replacing them with inputs coming from outside. Hence, decomposing the internal or external energy throughputs may bring to light their contrasting sociometabolic profiles. A Catalan case study in 1860 and 1990 is used as a test bench to show how revealing this decomposing analysis may be to plot the energy profiles of farm systems and their possible improvement pathways.Peer Reviewe