Environment, Power, and Society

For the past three decades the quantity of petroleum (both oil and oil plus gas) found per foot of drilling effort in the United States for any given year can be expressed as a secular decrease of about 2 percent per year combined with an inverse function of drilling effort for that year. Extrapolation of energy costs and gains from petroleum drilling and extraction indicates that drilling for domestic petroleum could cease to be a net source of energy by about 2004 at low drilling rates and by 2000 or sooner at high drilling rates, and that the net yield will be less at higher drilling rates.

https://science.sciencemag.org/content/sci/211/4482/576.full.pdf

Petroleum drilling and production in the United States: yield per effort and net energy analysis.

Shrimp farming in mangrove areas has grown dramatically in Asia and Latin America over the past decade. As a result, demand for resources required for farming, such as feed, seed, and clean water, has increased substantially. This study focuses on semiintensive shrimp culture as practiced on the Caribbean coast of Colombia. We estimated the spatial ecosystem support that is required to produce the food inputs, nursery areas, and clean water to the shrimp farms, as well as to process wastes. We also made an estimate of the natural and human-made resources necessary to run a typical semiintensive shrimp farm. The results show that a semiintensive shrimp farm needs a spatial ecosystem support—the ecological footprint—that is 35–190 times larger than the surface area of the farm. A typical such shrimp farm appropriates about 295 J of ecological work for each joule of edible shrimp protein produced. The corresponding figure for industrial energy is 40:1. More than 80% of the ecological primary production required to feed the shrimps is derived from external ecosystems. In 1990 an area of 874–2300 km2 of mangrove was required to supply shrimp postlarvae to the farms in Colombia, corresponding to a total area equivalent to about 20–50% of the country’s total mangrove area. The results were compared with similar estimates for other food production systems, particularly aquacultural ones. The comparison indicates that shrimp farming ranks as one of the most resource-intensive food production systems, characterizing it as an ecologically unsustainable throughput system. Based on the results, we discuss local, national, and regional appropriation of ecological support by the semiintensive shrimp farms. Suggestions are made for how shrimp farming could be transformed into a food production system that is less environmentally degrading and less dependent on external support areas.

Ecological limitations and appropriation of ecosystem support by shrimp farming in Colombia

Technologies play a critical role in mediating the impact o f the human enterprise on the ecosphere. Consequently, the adoption of more biophysically efficient technologies is essential i f the sustainability o f the human enterprise is to improve as populations and per capita consumption demands increase. Within this context, the biophysical efficiency o f two salmon production technology systems were analysed and compared using ecological footprint and energy analysis. The two systems evaluated are the vessel-based commercial salmon fishery and the salmon farming industry, as both exist in Bri t ish Columbia, Canada. In addition, the relative efficiency o f the three harvesting technologies employed within the commercial fishery were also evaluated. The ecological footprint analyses entailed quantifying the marine and terrestrial ecosystem support areas needed to grow salmon, sustain labour inputs, and assimilate CO2 equivalent to the greenhouse gases that result from industrial energy and material inputs. The energy analyses focussed exclusively on the direct and indirect industrial energy inputs to both systems. The results o f both the ecological footprint and energy analyses indicate that salmon farming is the least biophysically efficient, and hence least sustainable system for producing salmon currently operating in Brit ish Columbia. On a speciesspecific basis, farmed chinook salmon (Oncorhynchus tshawytscha) appropriated .the largest total area o f ecosystem support at 16 ha/tonne. This was followed by farmed Atlantic salmon (Salmo salar) at 12.7 ha/tonne, and commercially caught chinook and coho salmon (Oncorhynchus kisutch) at 11 ha/tonne and 10.2 ha/tonne, respectively. Commercially caught sockeye (Oncorhynchus nerka), chum (Oncorhynchus ketd), and pink salmon (Oncorhynchus gorbuscha) had the smallest total ecological footprints at 5.7, 5.2 and 5 ha/tonne, respectively. Results o f the energy analyses followed a similar pattern. Farmed chinook salmon required a total fossil fuel equivalent industrial energy input o f about 117 GJ/tonne while at the other extreme, total energy inputs to commercially harvested pink salmon amounted to only 22 GJ/tonne. Within both systems, however, opportunities exist to improve the biophysical efficiency o f salmon production. Final ly , amongst the three commercial fishing technologies evaluated, purse seining was approximately twice as efficient at harvesting an average tonne o f salmon as were either gillnetting or trolling.

Salmon and sustainability : the biophysical cost of producing salmon through the commercial salmon fishery and the intensive salmon culture industry

Managing aquaculture for sustainability in tropical Lake Kariba, Zimbabwe

Procedures are developed and summarized that allow the calculation of the energy required to manufacture and install capital equipment, such as the material needed for a coalfired power plant. Three methods are available, each with certain strengths and weaknessess The first uses both literature value and national manufacturing statistics, the second uses a previously developed technique that disaggregates energy use according to how much each industry buys from all other industries, and the third technique is based on the average national relation between energy use and dollar flow. The most important differences between estimates of energy use by the different techniques relates to the inclusion or exclusion of labor and indirect expenditures rather than to differences in the data bases of the three techniques.

Efficiency of energy delivery systems: II. Estimating energy costs of capital equipment

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Efficiency of energy delivery systems: II. Estimating energy costs of capital equipment