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Comparing land use impacts for petroleum and biofuels

08.01.2012  |  Thinnes, Billy,  Hydrocarbon Processing Staff, Houston, TX

Keywords: [land use] [oil sands] [biofuels] [oil] [Canada] [US] [surface mining] [carbon] [GHG emissions]

The biofuels industry claims its fuel is unfairly singled out by potential regulatory policies that focus on greenhouse gas (GHG) emissions associated with land use change. It argues that petroleum also causes land use change impacts and should be similarly judged in any such regulatory scheme. In an effort to contribute to the scientific analysis of this debate, an international research team, led by University of California–Davis research engineer Sonia Yeh, has published one of the first estimates of land use change GHG emissions from petroleum production.

The team’s findings conclude that emissions released from land disturbed by certain fossil fuel extraction methods can be comparable to, or are higher than, emissions from land disturbed by farming crop-based biofuels (when measured as tons of carbon emitted per unit of land disturbed). However, when measured per unit of energy produced, the land impacts of even the most high-impact fossil fuels are a tiny fraction of those of biofuels.

“We started this because of the current policy debates,” said Ms. Yeh, who acknowledged that regulators and researchers believed the land use impacts of petroleum production were minimal when compared to biofuels. She and her team, under contract with the California Air Resources Board, set out to test this belief. “It turns out that, while many researchers have looked at land use impacts of biofuels, few have looked at the land use impacts associated with oil.”

The research team focused on the land use impacts of heavy crude oil extracted in California and in Alberta’s Canadian oil sands (Fig. 1). The study examined conventional extraction methods, such as drilling, which occurs in California and Alberta, and nonconventional extraction methods in Alberta. Nonconventional extraction methods include surface strip mining of the bitumen soil and in-situ recovery, where steam is injected into a deep well. The researchers first estimated the amount of land impacted by the different processes, and then calculated the GHG emissions from the land disturbances.

  Fig. 1.  Oil sands operation in Athabasca, Alberta, Canada.
  Photo courtesy of NASA’s Earth Observatory.

To estimate the amount of land affected by conventional processes (about half of Alberta’s output is conventional), they applied a custom software program to Google Earth images of the land disturbances, such as well pads, pipelines, access roads and seismic surveys. They found that the land use impacts of conventional oil extraction methods are limited, compared to nonconventional oil sands processes.

Land disturbance

To estimate the land use impacts of oil sands processes, the study relies on the earlier findings of co-authors Sarah Jordaan and David Keith from the University of Calgary. Land disturbance for in-situ recovery includes central processing facilities and networks of seismic lines, roads, pipelines, well pads, and upstream land use disturbance for natural gas production (a key fuel used in the in-situ production process). In surface mining, a large area is cleared of all vegetation and then excavated. The total land disturbance includes a mine site, overburden storage, and “tailings” ponds, which not only cover large areas of land but are also high in chemical wastes and toxic substances. The team found that the impacts of the oil sands processes can be significant for three reasons.

First, the surface mining process disturbs enormous amounts of land rich in carbon deposits. Second, only 12% of the total oil sands surface mining area in Alberta is reported as reclaimed, which means the land impact is prolonged. Third, the use of tailings ponds makes the land unavailable for reclamation and carbon sequestration.

Improved restoration practices could significantly reduce GHG emissions and, therefore, the land and GHG impact, said Ms. Yeh. Companies can reduce emissions from tailings ponds by employing strategies to facilitate sedimentation, reduce tailings size, and more quickly return the land to its natural state. HP

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