Researcher urges more effort on assessment of land and water impacts of oil sands production; reference point for other unconventional fuels
Bitumen production from the Canadian oil sands provides a point of reference that could be used to observe and better manage the land and water impacts of a rapid transition to unconventional fuels, suggests Dr. Sarah Jordaan of the Energy Technology Innovation Policy Research Group, Department of Earth and Planetary Sciences, Harvard University.
The production of bitumen, the hydrocarbon mixed in the sand, has grown from 0.7 to 1.6 million barrels per day since 2000 and is expected to double over the next 10 years, Jordaan notes in a paper published in the ACS journal Environmental Science & Technology. While greenhouse gas emissions from oil sands production are relatively well studied, there has been less discussion of water and land use impacts due to their inherently local nature and much greater complexity, she notes.
It is understood that oil sands technologies produce 10−20% more greenhouse gases than the average conventional fuel when calculating life cycle emissions from well to wheel, yet much less emphasis has been placed on quantifying water and land impacts.—Jordaan 2012
The two types of bitumen production—surface mining and thermal in situ production—have different land and water impacts. Land use of surface mining comprises mine sites, overburden storage, tailing ponds, and end pit lakes—i.e., a set of polygonal features. In situ development has a different footprint, mostly defined by linear features that extend across the lease area, such as networks of seismic lines, access roads, pipelines and well sites.
As of 2009, only 600 km2 of land were disturbed by surface mining, accounting for 0.3% of the area where oil sands resources are present, or less than 0.1% of the total land area of Alberta. Eighty percent of the resource is currently expected to be extracted using in situ technologies, affecting approximately 136,000 km2 (97% of the total oil sands area). While natural gas is used in surface mining, in situ recovery can use on the order of four times more than surface mining. The cumulative footprint of the future oil sands operations may extend over approximately the 140000 km2 during the course of the development, comprising of 20% of Alberta, and even more if the upstream footprint from the infrastructure required for natural gas production is included.
Surface mining results in the conversion of large tracts of land, whereas in situ recovery fragments landscapes, both of which result in ecological impacts...The conventional wisdom is that mining operations have a much larger landscape impact than in situ recovery—the latter has typically been viewed as more environmentally benign in terms of land use. This conclusion does not reflect landscape fragmentation caused by in situ projects and upstream natural gas production. The land impacts of in situ recovery may be comparable and even greater than that of surface mining when these are considered per unit of synthetic crude oil.—Jordaan 2012
Water use likewise varies with the extraction methodology, she notes. Water use for surface mining ranges from 2-3.5 barrels of water per barrel of bitumen produced, depending upon the study. In situ operators use brackish water where possible from underground aquifers. Where brackish water is used, then roughly 0.5 to 0.9 barrels of fresh water are used to produce one barrel of bitumen. More than 90% and 80−95% of water used can be recycled for in situ recovery and surface mining, respectively.
|A key learning point for emerging players in unconventional fuel production is the use of brackish water in oil sands operations to reduced fresh water use where constrained by water scarcity or policy.
Technologies can reduce impacts, although potentially with increased emissions and costs. Natural gas consumption—and the associated land footprint—can be reduced if bitumen is gasified to produce natural gas required for steam production. Nuclear and biomass have also been suggested as alternative energy inputs. Using solvent instead of steam, using electric heating, or using in situ combustion could reduce water use for in situ production. Water storage can mitigate water use of oil sands mining during low flow times.
While the land and water impacts of oil sands development are significant, it is important to keep them in perspective in comparison with other transportation fuel options. At the broadest level, the amount of land disturbed for oil sands is minimal when compared to first generation corn ethanol. Based on the heating values of the fuels, it would take all 66 million ha of Alberta approximately 210 years to produce the same amount of energy contained in the oil sands from corn ethanol in the US. This land area is roughly 5 times greater than the area that could be affected by the oil sands development. It should be noted that cellulosic ethanol and biodiesel from yellow grease both have negligible land disturbance in comparison to oil sands. Keeping this in mind, there are several challenges to comparing land and water use impacts of different transportation fuel pathways, mostly related to the choice of temporal scale and spatial resolution.—Jordaan 2012
There is no accepted methodology regarding the treatment of time for analyses of land impacts, Jordaan notes, adding that much like global warming potential, the choice of a time horizon is a policy decision, not a scientific one.
The ultimate goal of comparing the land and water impacts of energy technologies is to understand trade-offs related not only resource use, but also to larger scale landscapes and watersheds. Intensity metrics for land and water are limited not only temporally, but also spatially. They cannot capture cumulative effects of resource extraction that are necessary to under- standing the incremental impacts of development. Furthermore, the heterogeneity of landscapes and watersheds creates challenges in placing value on impacts. This highlights the need for more research, not only on the impacts, but also how to include societal values and at what scale values should be considered (e.g., regional versus national). Comparative analyses for water and land intensity of energy technologies are ultimately very useful, but we cannot determine impacts without understanding the regional implications.—Jordaan 2012
The transition to unconventional fossil fuels will ultimately change both the quality and availability of water and land resources, Jordaan concludes. Without proper assessment, she suggests, these transitions may not be managed adequately particularly if the growth is rapid, such as the case of oil sands.
As we transition to unconventional fuels, our impacts to land and water resources will change. There are two current challenges that need to be addressed, one is the need to better quantify impacts and the other is to better address those that are not currently well managed. A better understanding of how well technologies and policies address these impacts can inform governance in other areas with rapidly expanding unconventional fossil fuel production that is analogous to the case of oil sands, such as shale gas.—Jordaan 2012
Sarah M. Jordaan (2012) Land and Water Impacts of Oil Sands Production in Alberta. Environmental Science & Technology doi: 10.1021/es203682m