Cutler J. Cleveland

Energy and the u.s. Economy: a biophysical perspective.

A series of hypotheses is presented about the relation of national energy use to national economic activity (both time series and cross-sectional) which offer a different perspective from standard economics for the assessment of historical and current economic events. The analysis incorporates nearly 100 years of time series data and 3 years of cross-sectional data on 87 sectors of the United States economy. Gross national product, labor productivity, and price levels are all correlated closely with various aspects of energy use, and these correlations are improved when corrections are made for energy quality. A large portion of the apparent increase in U.S. energy efficiency has been due to our ability to expand the relative use of high-quality fuels such as petroleum and electricity, and also to relative shifts in fuel use between sectors of the economy. The concept of energy return on investment is introduced as a major driving force in our economy, and data are provided which show a marked decline in energy return on investment for all our principal fuels in recent decades. Future economic growth will depend largely on the net energy yield of alternative fuel sources, and some standard economic models may need to be modified to account for the biophysical constraints on human economic activity.

Aggregation and the role of energy in the economy

Methods for investigating the role of energy in the economy involve aggregating different energy flows. A variety of methods have been proposed, but none has received universal acceptance. This paper shows that the method of aggregation has crucial effects on the results of the analysis. We review the principal assumptions and methods for aggregating energy flows: the basic heat equivalents approach, economic approaches using prices or marginal product for aggregation, emergy analysis, and thermodynamic approaches such as exergy. We argue that economic approaches such as the index or marginal product method are superior because they account for differences in quality among fuels. We apply various economic approaches in three case studies in the US economy. In the first, we account for energy quality to assess changes in the energy surplus delivered by the extraction of fossil fuels from 1954 to 1992. The second and third case studies examine the importance of energy quality in evaluating the relation between energy use and GDP. First, a quality-adjusted index of energy consumption is used in an econometric analysis of the causal relation between energy use and GDP from 1947 to 1996. Second, we account for energy quality in an econometric analysis of the factors that determine changes in the energy:GDP ratio from 1947 to 1996. Without adjusting for energy quality, the results imply that the energy surplus from petroleum extraction is increasing, that changes in GDP drive changes in energy use, and that GDP has been decoupled from between aggregate energy use. All of these conclusions are reversed when we account for changes in energy quality.

Hydrocarbons and the evolution of human culture

Most of the progress in human culture has required the exploitation of energy resources. About 100 years ago, the major source of energy shifted from recent solar to fossil hydrocarbons, including liquid and gaseous petroleum. Technology has generally led to a greater use of hydrocarbon fuels for most human activities, making civilization vulnerable to decreases in supply. At this time our knowledge is not sufficient for us to choose between the different estimates of, for example, resources of conventional oil.

Energy quality and energy surplus in the extraction of fossil fuels in the U.S.

Abstract The goal of net energy analysis is to assess the amount of useful energy delivered by an energy system, net of the energy costs of delivery. The standard technique of aggregating energy inputs and outputs by their thermal equivalents diminishes the ability of energy analysis to achieve that goal because different types of energy have different abilities to do work per heat equivalent. This paper describes physical and economic methods of calculating energy quality, and incorporates economic estimates of quality in the analysis of the energy return on investment (EROI) for the extraction of coal and petroleum resources in the U.S. from 1954 to 1987. EROI is the ratio of energy delivered to energy used in the delivery process. The quality-adjusted EROI is used to answer the following questions: (1) are coal and petroleum resources becoming more scarce in the U.S.?, (2) is societys capability of doing useful economic work changing?, and (3) is societys allocation of energy between the extraction of coal and petroleum optimal? The results indicate that petroleum and coal became more scarce in the 1970s, although the degree of scarcity depends on the type of quality factor used. The quality-adjusted EROI shed light on the coal-petroleum paradox: when energy inputs and outputs are measured in thermal equivalents, coal extraction has a much larger EROI than petroleum. The adjustment for energy quality reduces substantially the difference between the two fuels. The results also suggest that when corrections are made for energy quality, societys allocation of energy between coal and petroleum extraction meets the efficiency criteria described by neoclassical and biophysical economists.

THERMAL IMAGING REVEALS SIGNIFICANTLY SMALLER BRAZILIAN FREE-TAILED BAT COLONIES THAN PREVIOUSLY ESTIMATED

Abstract Using data collected with thermal imaging technology, we found a major reduction in population estimates of colony size in the Brazilian free-tailed bat (Tadarida brasiliensis) from 54 million, obtained in 1957 without this technology, to 4 million in 6 major cave colonies in the southwestern United States. The 1957 census was based on human visual observations of cave emergence flights that were subject to potentially high errors. The recent census was produced using an accurate, reproducible counting method and based on complete temporal records of colony emergences. Analysis of emergence flights from dusk through darkness also revealed patterns in group behavior that would be difficult to capture without thermal infrared technology. Flow patterns of bats during emergence flights exhibited characteristic single, double, or triple episodes, with the peak flow during the 1st episode. A consistent rhythmic pattern of flow episodes and pauses was revealed across colonies and was independent of emergence tempo.

The direct and indirect use of fossil fuels and electricity in USA agriculture, 1910–1990

Abstract Industrial agriculture relies on large quantities of fossil fuels and electricity. The increase in energy prices in the 1980s prompted substantial investigation into the response of farmers to new energy conditions, and into the prospects for future food production in the face of scarcer and more expensive energy inputs. Previous attempts to model these relationships were hampered by a lack of consistent and reliable historical data on total energy use in USA agriculture. This analysis develops and applies a new methodology to calculate the direct and indirect use of fossil fuels and electricity on USA farms from 1910 to 1990. The data on energy use is used to construct indices of energy productivity over the same period. The results show a substantial overall increase in energy use from 1910 through the 1970s, and a shift from gasoline to diesel fuel and electricity. The use of all fuels declined in the 1980s. The measures of energy productivity show a substantial decline in through the 1970s, a trend consistent with the substitution of fossil fuels for animate power and with the low price of fossil fuels relative to other inputs. Energy productivity rose in the 1980s due to a diminution in the rate of energy use, a reduction in the number of harvested hectares, and larger farms. The results show a clear response of farmers to higher energy prices that resulted in technical and managerial changes that improved energy productivity.

Biophysical economics: Historical perspective and current research trends

Abstract Biophysical economics is characterized by a wide range of analysis from diverse fields who use basic ecological and thermodynamic principles to analyze the economic process. The history of biophysical thought is traced from the 18th-century Physiocrats to current empirical research, with emphasis on those individuals who contributed to the development of biophysical economic theory. Attention is also given to a critique of the neoclassical theory of natural resources from a biophysical perspective, and how recent empirical biophysical research highlights areas of neoclassical theory which could be improved by a more relatistic and systematic treatment of natural resources.

Energy and Sustainable Development at Global Environmental Summits: An Evolving Agenda

This paper presents a framework for understanding energy issues in the context of sustainable development. It posits that there are three important ways in which energy is related to sustainable development: (a) energy as a source of environmental stress, (b) energy as a principal motor of macroeconomic growth and (c) energy as a prerequisite for meeting basic human needs. These three dimensions correspond to the three dimensions of the often-used triangle of sustainable development: environmental, economic, and social. Using this framework, the paper traces how successive environmental summits at Stockholm (1972), Rio de Janeiro (1992) and Johannesburg (2002) have dealt with energy issues. It identifies a slow, surprising and important evolution of how energy issues have been treated at these global discussions. Energy has received increasing prominence at these meetings and become more firmly rooted in the framework of sustainable development. Stockholm was primarily concerned with the environmental dimension, Rio de Janeiro focused on both the environmental and economic dimensions, and the major headway made at Johannesburg was the meaningful addition of the social dimension and the linking of energy issues to the UNs Millennium Development Goals.

BRAZILIAN FREE‐TAILED BATS AS INSECT PEST REGULATORS IN TRANSGENIC AND CONVENTIONAL COTTON CROPS

During the past 12000 years agricultural systems have transitioned from natural habitats to conventional agricultural regions and recently to large areas of genetically engineered (GE) croplands. This GE revolution occurred for cotton in a span of slightly more than a decade during which a switch occurred in major cotton production areas from growing 100% conventional cotton to an environment in which 95% transgenics are grown. Ecological interactions between GE targeted insects and other insectivorous insects have been investigated. However, the relationships between ecological functions (such as herbivory and ecosystem transport) and agronomic benefits of avian or mammalian insectivores in the transgenic environment generally remain unclear, although the importance of some agricultural pest management services provided by insectivorous species such as the Brazilian free-tailed bat, Tadarida brasiliensis, have been recognized. We developed a dynamic model to predict regional-scale ecological functions in agricultural food webs by using the indicators of insect pest herbivory measured by cotton boll damage and insect emigration from cotton. In the south-central Texas Winter Garden agricultural region we find that the process of insectivory by bats has a considerable impact on both the ecology and valuation of harvest in Bacillus thuringiensis (Bt) transgenic and nontransgenic cotton crops. Predation on agricultural pests by insectivorous bats may enhance the economic value of agricultural systems by reducing the frequency of required spraying and delaying the ultimate need for new pesticides. In the Winter Garden region, the presence of large numbers of insectivorous bats yields a regional summer dispersion of adult pest insects from Bt cotton that is considerably reduced from the moth emigration when bats are absent in either transgenic or non-transgenic crops. This regional decrease of pest numbers impacts insect herbivory on a transcontinental scale. With a few exceptions, we find that the agronomics of both Bt and conventional cotton production is more profitable when large numbers of insectivorous bats are present.

Resource degradation, technical change, and the productivity of energy use in U.S. agriculture

Abstract Two important issues surrounding future food production are the reliance of industrial agriculture on large quantities of fossil fuels and the degree to which technical change and farm management can offset degradation in the form of soil erosion, groundwater depletion, reduced genetic diversity, pest resistance, and so on. This analysis uses new and more consistent data on energy use in U.S. agriculture to assess the forces that shape the productivity of energy use from 1950 to 1990. The results of an econometric model indicate that changes in the quantity of energy used per hectare, the average size of farms, the quantity of land harvested, the ratio of livestock to crop production, and weather influence the productivity of energy use (in order of decreasing importance). Energy productivity shows strong diminishing returns to increases in energy use per hectare of land. The model indirectly tests for the effects of of resource degradation and technical change on energy productivity. The results do not support the hypothesis that the effects of soil erosion and other forms of resource degradation have diminished the productivity of energy use in the U.S. farm sector, presumably due to advances in technology and behavioral responses on the part of farmers. The significant increase in energy productivity since 1980 is due to a sharp reduction in energy use per hectare, a reduction in the quantity of land utilized, and continuing increases in average farm size. These results are consistent with other empirical analyses of aggregate energy productivity in industrial agriculture that indicate an improvement in energy productivity in response to the energy price increases.