Monday, November 01, 2010

Phosphate Mining and Climate Change

While today's blog treads into the subject of phosphate mining in central Florida, the bigger picture involves all surface mining (e.g., mountain top removal for coal), and an even bigger picture of large land use development anywhere on our Planet. The following discussion is neither pro or anti mining or land development, but raises a question "Don't we need to talk about something?" -- where the "Something" is Climate Change.

In arguments (and legal fights) over mining or land development, the major environmental issues usually involve topics of water (pollution, use) and habitat loss, with wetlands being the focal point. Never (at least here in Florida) have we seen the subject of Climate Change even enter into the discussion of land use development (like mining).

According to the U.S. Army Corps of Engineers, phosphate mining has occurred on 1.32 million acres (~2,100 square miles) in central Florida. Additional mining is being requested for ~100,000 acres. And here is the problem -- in mining 1.42 million acres, has this resulted in a significant Climate Change event? Nobody really knows, because the question has never been asked.

In phosphate mining, has the greenhouse gas mass balance (i.e., the release of primarily CO2 through land clearing and soil disturbance and the carbon capture post-mining practices of land reclamation) been: (1) relatively carbon cycle neutral, or (2) resulted in large carbon deficits?

One science based scientific citation that can be used in an initial discussion is work performed by Kimble, Heath, Birdsey, and Lal (The Potential of U.S. Forests Soils to Sequester Carbon and Mitigate the Greenhouse Gas Effect). The below table presents an estimate for total carbon capture (above and below ground) associated with forests which would be representative of pre-mined phosphate lands.

Type of Forest

C in Biomass
C in Dead Mass

Soil Organic C
(1-m depth)(t/ha)2
Total Forest C

(1) Dead mass includes standing dead trees, down dread trees, and forest floor.
(2) Soil includes both mineral soil and organic soils (i.e., histosols).

Estimating the carbon released from mining 1.42 million acres (from the above proxy estimates from Kimble, et al.) results in ~548 million tons of CO2 released. Putting 548 million tons of CO2 into perspective -- would be the approximate CO2 release equivalents of:

-- Operating a coal power plant like TECO's Polk Power Station for 515 years.
-- Operating all coal fired power plants in Florida for ~8 years.
-- Operating all power plants in Florida (coal, oil, gas) for ~4 years.
-- Approximately 3 years of total volcanic activity on the Earth.

Of course, the above illustrations only reflect one part of the total greenhouse gas mass balance -- the initial emissions from land clearing and soil disturbance. According to landmark research on phosphate mined soils performed by the U.S. Department of Energy's Oak Ridge National Lab, carbon capture/sequestration on heavily forested post-mined lands and/or wetlands can be dramatic. However for lands reclaimed to pasture, the majority of the sequestered carbon is soon converted back to CO2 through respiration (Murray, Economics of Forest Carbon Sequestration, 2003).

In conclusion, it is believed that the topic of Climate Change needs to be on the "Table" whenever large land use applications (such as mining) are being decided. Clearly it is impossible to develop any type of "Actions" if the magnitude of the Climate Change concern is simply not known -- where in our opinion, the best actions are always voluntary and market based solutions.

As Mike Myers used to say on Saturday Night Live!, "feel free to discuss amongst yourselves."

(A draft of the letter to the U.S. Army Corps of Engineers is available for comments).

1 comment:

Anonymous said...

This is the first time I have seen a number for the amount of land that has been utilized for phosphate mining in Florida. However, it does not include Lime Stone mining, which is most likely a similar number of acres. Most of the mining pits in Florida invade the water table and therefore, the ground water, which exposes it to evaporation, at a rate of at least 20" of evaporation per year from the exposed pits. That is a great deal of water loss. Why is know one looking at this as well? It should be included in this study.