Widening the analysis of Energy Return on Investment (EROI) in agro-ecosystems: Socio-ecological transitions to industrialized farm systems (the Vallès County, Catalonia, c.1860 and 1999)

Assessing the energy trap of industrial agriculture in North America and Europe: 82 balances from 1830 to 2012

Early energy analyses of agriculture revealed that behind higher labor and land productivity of industrial farming, there was a decrease in energy returns on energy (EROI) invested, in comparison to more traditional organic agricultural systems. Studies on recent trends show that efficiency gains in production and use of inputs have again somewhat improved energy returns. However, most of these agricultural energy studies have focused only on external inputs at the crop level, concealing the important role of internal biomass flows that livestock and forestry recirculate within agroecosystems. Here, we synthesize the results of 82 farm systems in North America and Europe from 1830 to 2012 that for the first time show the changing energy profiles of agroecosystems, including livestock and forestry, with a multi-EROI approach that accounts for the energy returns on external inputs, on internal biomass reuses, and on all inputs invested. With this historical circular bioeconomic approach, we found a general trend towards much lower external returns, little or no increases in internal returns, and almost no improvement in total returns. This "energy trap" was driven by shifts towards a growing dependence of crop production on fossil-fueled external inputs, much more intensive livestock production based on feed grains, less forestry, and a structural disintegration of agroecosystem components by increasingly linear industrial farm managements. We conclude that overcoming the energy trap requires nature-based solutions to reduce current dependence on fossil-fueled external industrial inputs and increase the circularity and complexity of agroecosystems to provide healthier diets with less animal products.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13593-023-00925-5.

Edible Energy Production and Energy Return on Investment—Long-Term Analysis of Global Changes

The projected increase in the world’s population requires an increase in the production of edible energy that would meet the associated increased demand for food. However, food production is strongly dependent on the use of energy, mainly from fossil fuels, the extraction of which requires increasing input due to the depletion of the most easily accessible deposits. According to numerous estimations, the world’s energy production will be dependent on fossil fuels at least to 2050. Therefore, it is vital to increase the energy efficiency of production, including food production. One method to measure energy efficiency is the energy return on investment (EROI), which is the ratio of the amount of energy produced to the amount of energy consumed in the production process. The literature lacks comparable EROI calculations concerning global food production and the existing studies only include crop production. The aim of this study was to calculate the EROI of edible crop and animal production in the long term worldwide and to indicate the relationships resulting from its changes. The research takes into account edible crop and animal production in agriculture and the direct consumption of fossil fuels and electricity. The analysis showed that although the most underdeveloped regions have the highest EROI, the production of edible energy there is usually insufficient to meet the food needs of the population. On the other hand, the lowest EROI was observed in highly developed regions, where production ensures food self-sufficiency. However, the changes that have taken place in Europe since the 1990s indicate an opportunity to simultaneously reduce the direct use of energy in agriculture and increase the production of edible energy, thus improving the EROI.

An energy-landscape integrated analysis to evaluate agroecological scarcity

Agrarian landscapes theoretically provide ecosystem services that meet the demands of a wide range of socioecological processes. Consequently, any landscape agroecology approach must tackle the dynamic interaction of land-use distribution and associated social metabolism at different spatiotemporal scales. An agroecological scarcity case study explores how driven agricultural energy flows interact with landscape complexity in arid landscapes of 46 counties in the Qazvin Province (Iran). An Energy-Landscape Integrated Analysis (ELIA) was performed to correlate the energy reinvestment (E) and energy redistribution (I) present within the social metabolism network, with landscape complexity (Le) measured in terms of spatial patterns and related ecological processes. As well, a cluster analysis was run to establish agrarian landscape typologies based on the ELIA indicators. The results of this study provide an explicit sketch of the four strategies that society in Qazvin Province has developed within the dry environments that sustain it. Our findings confirm the hypothesis that there is a positive relationship between optimizing non-dissipative internal energy loops and landscape complexity, which can explain agroecosystem sustainability. This research enables us to define spatially informed agroecological transitions from a territorially explicit socioecological perspective and will make a significant contribution to decisions on agricultural policies given different land-use strategies, especially under scenarios of ecological scarcity.

Landscape social-metabolism in food-energy-water systems: Agricultural transformation of the Upper Snake River Basin

This paper applies a social metabolism framework and energy flow analysis for evaluating agroecosystem and land use transitions in food-energy-water systems using the Upper Snake River Basin (USBR), Idaho, USA as a case-study. The study area is one of the primary agricultural regions of the State of Idaho. Dairy products are the primary agricultural outputs of the region; therefore, we modified a biomass accounting framework to explicitly incorporate the role of manure in the agroecosystem. Despite the increase of cropland between 2002 and 2012 in the basin, a decrease in energy input was observed for crop production. An increase in the industrial energy inputs for dairy production, on the other hand, showed that the basin is a clear example of a metabolic industrialized farm system - an example of land use intensification. We compare the energy return on investments (EROIs) as an indicator of agroecosystem transition for both crop and dairy production during the period 2002 to 2012. Contrary to our expectations, the analysis suggests that livestock production is a relatively energy efficient process in land management in the basin. This is due to the reuse of nutrient by-products from livestock as well as the refuse and residues from crop farming. At the same time, the findings provide insights on the percentage of manure to be reinvested as compost that would improve energy production efficiency. However, the reuse of manure, as it is managed in the basin, may have a negative implication on the nutrient balance of the agroecosystem that needs further investigation. Nonetheless, there is market potential for the reuse and reinvestment of biomass to make energy production in the basin more efficient.

Pastures and Cash Crops: Biomass Flows in the Socio-Metabolic Transition of Twentieth-Century Colombian Agriculture

This article aims to situate a national case study of the global periphery at the core of the debate on the socio-ecological transition by drawing on new data of biomass flows in twentieth-century Colombia. We draw up a century-long annual series converting a wide set of indicators from Net Primary Production (NPP) into the final socioeconomic uses of biomass, distinguishing around 200 different categories of crops, forests, and pastures. Our calculations draw on FAOSTAT and several corpuses of national statistics. The results show a fall of 10% in total NPP related to land-use changes involving forest conversion. Throughout the twentieth century, pasture was the most relevant among domestic extraction. Allocations of cash crops to industrial processing rose while the figure for staple crops for primary food consumption stagnated. The critical role of cattle throughout all periods and the higher yields of the industrial cash crops are behind this profile. This might also mean the start of a new trend of using pasture land for more profitable export crops, which establishes a new inner frontier of land-use intensification. Lastly, the article points out the phases of the socio-metabolic transition of biomass, explores the changes in biomass flows by looking at the history of the main drivers, and identifies the socio-ecological impacts of deforestation and industrial agribusiness.

At the core of the socio-ecological transition: Agroecosystem energy fluxes in Austria 1830-2010

Analyses of energy efficiency in biomass production offer important insights in the context of sustainable land management and biomass production. However, much of the previous research on the topic has focused on the energy efficiency of either food or energy provision. Only recently, comprehensive analyses at the total agroecosystem level have been operationalized, studying long-term change in agroecosystem energetics in the course of the socio-ecological transition. We contribute to this line of research by offering an empirical assessment of agroecosystem energetics for the case of Austria, covering the period 1830-2010 at an annual resolution. We present a quantitative assessment of energy inputs, outputs and internal energy fluxes of Austria's agroecosystem, including crop production, livestock production and forestry, as well as energy return on investment indicators. We identify three major periods: (1) "pre-industrial land-use intensification" (1830-1914) is characterized by moderate agricultural growth based on increased biomass recirculation, declining wood harvest, and, probably, slightly declining energy returns on investments. (2) From 1918 to 1985, "industrialization of land use and the green revolution" exhibits a substitution of labor by modern energy inputs, while livestock continued to rely greatly on domestic biomass. (3) "Industrialized extensification and environmental awareness" (1986-2010) features increasing energy efficiency due to declines in livestock numbers, a shift towards forestry, and a rising amount of final products from croplands at stable energy inputs. We discuss these periods in the context of changes in both ecological impacts and social metabolism, and identify trade-offs among food and bioenergy provision.

Landscape Agroecology. The Dysfunctionalities of Industrial Agriculture and the Loss of the Circular Bioeconomy in the Barcelona Region, 1956–2009

The paper analyses how between 1956 and 2009 the agrarian metabolism of the Barcelona Metropolitan Region (BMR) has become less functional, losing circularity in biomass flows and in relationship to its landscape. We do so by adopting a Multi-Energy Return on Investment (EROI) and flow-fund (MuSIASEM) analyses and the nexus with landscape functional structure. The study of agricultural flows of Final Produce, Biomass Reused and External Inputs is integrated with that of land use, livestock, power capacity, and population changes between 1956 (at the beginning of agrarian industrialization) and 2009 (fully industrialized agriculture). A multi-scale analysis is conducted at the landscape scale (seven counties within the Barcelona metropolitan region) as well as for the functions deployed, within an agroecosystem, by the mutual interactions between its funds (landscape, land-uses, livestock, and farming population). A complex nexus between land, livestock, dietary patterns, and energy needs is shown; we conclude that, from the perspective of the circular bioeconomy the agrarian sector has gone worse hand in hand with the landscape functional structure. Therefore, a novel perspective in landscape agroecology is opened.

Can Agriculture Balance Its Energy Consumption and Continue to Produce Food? A Framework for Assessing Energy Neutrality Applied to French Agriculture

In the context of energy transition, agriculture is facing a double challenge, which is to reduce its fossil fuel dependency and provide—in addition to food—bioenergy to society for substitution to fossil fuels. The feasibility of this challenge depends on whether agriculture can achieve energy neutrality, meaning to balance its consumption of external energy by energy recovery from internal sources. Livestock feed is a major determinant in this balance. We use France as a demonstration case of the changing role of feed in the long-term agricultural energy metabolism and the challenge of reaching energy neutrality. Results show that current agriculture is structurally energy deficient to such an extent that its functional energy requirements almost equal its final produce. The energy recovery potential from crop residues and manure could at best cover the primary biomass equivalent of the external energy inputs to agriculture. Only a suppression of feed from cropland combined with very high energy recovery from agricultural residues could allow achieving energy neutrality and making agriculture a net energy source to society.

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.

Regional specialization and market integration: agroecosystem energy transitions in Upper Austria

We investigate agroecosystem energy flows in two Upper Austrian regions, the lowland region Sankt Florian and the prealpine region Grünburg, at five time points between 1830 and 2000. Energetic agroecosystem productivity (energy contents of crops, livestock products, and wood per unit area) is compared to different types of energy inputs, i.e., external inputs from society (labor, industrial inputs, and external biomass inputs) and biomass reused from the local agroecosystem (feed, litter, and seeds). Energy transfers between different compartments of the agroecosystem (agricultural land, forest, and livestock) are also quantified. This allows for delineating an agroecosystem energy transition: In the first stage of this transition, i.e., in the nineteenth century, agroecosystem productivity was low (final produce ranged between 14 and 27 GJ/ha/yr), and local biomass reused made up 97% of total energy inputs in both regions (25-61 GJ/ha/yr). In this period, agroecosystem productivity increase was achieved primarily through more recycling of energy flows within the agroecosystems. In the second stage of the agroecosystem energy transition, i.e., after World War II, external energy inputs increased by factors 2.5 (Sankt Florian) and 5.0 (Grünburg), partly replacing local energy transfers. Final produce per area increased by factors 6.1 (Sankt Florian) and 2.9 (Grünburg). The difference in the resulting energy returns on investment (EROI) owes to regional specialization on cropping versus livestock rearing and to increasing market integration. Our results suggest that sustainable land-use intensification may benefit from some regional specialization harnessing local production potentials based on a mix of local and external inputs.