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Council Finds Coal Cutbacks Vital to Lower CO2 Emissions in NW

Sep 19, 2007 - Clearing Up -

Retiring some existing coal-fired plants and replacing their output with cleaner resources is the key to maintaining or lowering carbon dioxide emissions from the regional electric sector, according to a new Northwest Power and Conservation Council paper.

State renewables portfolio standards, substantial energy conservation and summer-spill elimination are insufficient to significantly slow or reverse the rising trajectory of regional power-related CO2 emissions, according to "Carbon Dioxide Footprint of the Northwest Power System," released Sept. 13.

"CO2 production from electricity generation is dominated by existing coal-fired generating plants," the paper said. "To stabilize CO2 production at 2005 levels or to reduce CO2 production to 1990 levels would require substituting low CO2-producing resources or additional conservation for some of these existing coal-fired power plants.

"In addition, the scenario analysis shows that policy choices that are made for purposes other than CO2 reduction (in this case fish and wildlife policy) can also have significant effects on CO2 production; enough effect to negate policies such as renewables portfolio standards," it said.

The council analysis estimated that regional CO2 emissions from the Northwest electric system have risen from about 44 million tons in 1990--a popular baseline year for climate-change policies--to 67 million tons in 2005. Economic growth, added fossil-fueled generators, diminished hydro capabilities and closure of the Trojan nuclear plant near Portland all contributed to this trend, the council said.

The study also noted that had 2005 been a normal water year as was 1990, CO2 emissions in 2005 would have been about 59 millions tons, a 34-percent increase over 1990.

Looking ahead, the council projected that if regional resource development follows its 2004 plan emphasizing renewables, conservation and some natural gas, CO2 production by 2024 would amount to 71 million tons, representing a 20-percent gain over 2005, assuming normal water conditions in 2024.

"It's really easy to go up [with CO2 emissions] and it's really difficult to go down . . . is what appears to be happening," said council senior resource analyst Jeff King, at the Aug. 14 meeting of the council's Power Committee.

To return to 1990 CO2 levels or below, "you have to address the existing stock of coal-fired resources to achieve that kind of objective," he said. From 2015-2024, under the council's recommended resource portfolio, coal would account for 81 percent of Northwest power system CO2 production.

The Northwest, whose total capacity is close to two-thirds hydropower, fares well in CO2 emissions, relative to the greater West. Under normal water conditions in 2005, the region's power system would have emitted about 540 pounds of CO2 per megawatt-hour generated, compared to about 990 pounds/MWh for the Western Electricity Coordinating Council area, the council figured.

However, it noted, all regions possess "essentially the same set of future resource options," and consequently, "it will be difficult for the Northwest to maintain or reduce its CO2 emissions rate."

If state renewables portfolio standards were met in Washington, Oregon and Montana, and all summer spill were eliminated to enable more hydro generation, the growth rate of CO2 emissions would only be lowered an estimated 60 percent, the council found.

"Failure to achieve the conservation targets in the Fifth Power Plan, or removing the lower Snake River dams and replacing the power in a manner consistent with the Fifth Power Plan, could more than offset the potential savings from the scenarios that reduce CO2 production," the paper said.

The four federal dams on the lower Snake River generate about 1020 aMW of energy under current river operations, and provide 2650 MW of sustained-peaking capacity, according to the council.

The effect of their removal on regional CO2 emissions depends on the replacement resources, taken in the study to be 810 aMW from new and existing gas plants, and 170 aMW from existing coal units. This would raise average annual CO2 production 4.6 millions tons over the council plan's resource scenario from 2015-2024.

Making up the loss of the hydro generation from the lower Snake dams with a market-purchase scenario was considered but not reported. The council said this approach "would compromise system adequacy and reliability by reducing the amount of resource available to meet load."

Another potential scenario involves conservation and renewables as the main substitute resources, a notion promoted by the Northwest Energy Coalition, among others, in support of dam-breaching as a salmon-recovery measure.

This approach could delay some CO2 increases, but not stop or reverse it, the council paper said.

Tying the increased development of conservation and renewables to dam breaching is "misleading," it said, because this means discarding more than 1000 MW of "emission-free generation" that must eventually be replaced, "unless the supplies of renewables and conservation are considered unlimited."

However, given the difficulty of reducing CO2 emissions, discarding existing CO2-free power sources has to be considered "unproductive," it concluded.

Steve Weiss, policy analyst with NWEC, told the council's Power Committee last week that conservation and renewables as dam resource-replacements would not all be cost-effective, but added that he expected Congress to "make the region whole" and not increase costs specifically to Northwest electric ratepayers if it does authorize dam removal.

Weiss also said keeping the dams, in various spill scenarios, "doesn't change the CO2 problem very much."

The council asked its staff to forecast CO2 production using an assortment of future resource scenarios. The base case corresponded to the council's latest plan, while other scenarios were based on low conservation gains, high renewables development, or utility integrated resource plans.

Lower Snake dam removal and spill effects were also examined.

Under all these scenarios, regional CO2 emissions rose in 2024 from the 59 million tons emitted in 2005, an average water year. The lowest level was the high-renewables scenario, at 66 million tons in 2024, while the highest was the utility IRPs, at 77 million tons.

"The purpose of these alternative scenarios is to quantify the sensitivity of results to plausible changes in the power system and some related policies that have received attention," said the paper. "No new council position on any of these policies is intended by this analysis, nor should any be inferred."

Comments on the paper are due Oct. 19. The paper is available at [Mark Ohrenschall].


Updated: 2016/06/30

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