Carbon footprint of forest fertilization

Applying fertilizer nutrients to planted southern pines is a proven technology for increasing forest productivity. A recent study shows that fertilization of southern pines is also beneficial with respect to greenhouse gas mitigation. In other words, fertilization increases carbon sequestration in forests and forest products by an amount that far outweighs CO2 emissions associated with fertilizer production, transport and application.

These results are presented in a paper titled “Carbon emissions and sequestration from fertilization of pine in the southeastern United States” (Forest Science 58(5):419-429). The authors are T.J. Albaugh, E.D. Vance, C. Gauldreault, T.R. Fox, H.L. Allen, J.L. Stape, and R.A. Rubiliar. This work was sponsored by NCASI, the National Aeronautics and Space Administration, the Department of Forestry and Environmental Resources at NC State University, and members of the Forest Productivity Cooperative. The abstract follows.

“We estimated net carbon emission and sequestration directly attributable to common forest fertilization practices for pine plantations in the southeast United States. We used data from the literature to estimate the carbon emissions associated with the production, transportation, and application of fertilizers used for mid-rotation and early rotation applications as well as the stem wood growth response to these applications. These data were scaled to a regional basis with data from the literature and newly acquired fertilizer application information. Product disposition projections were completed through 125 years (five 25-year rotations). On average, application of nitrogen with 28 kg of elemental phosphorus ha-1 to mid-rotation stands sequestered 19.2 Mg ha-1 carbon dioxide (CO2) equivalents as additional stem growth per CO2 equivalent of emissions associated with the fertilizer application. Maximum combined emissions from forest fertilization were 0.34 Tg year-1 CO2 equivalents in 2002, whereas maximum sequestration was 8.70 Tg year-1 CO2 equivalents in 2007. Sequestration lagged emissions because of the long (up to rotation length) stem wood growth response period. After 100 years, approximately 38% of the CO2 equivalent sequestration attributed to mid-rotation fertilization would still be in use or in a landfill, whereas 26% would have been emitted without capturing energy and 36% would have been used as an energy source. Carbon sequestration associated with forest fertilization was related to the area fertilized annually, which may have fluctuated with fertilizer material and wood product prices. Capturing economic value from the sequestered carbon would likely increase forest fertilization and consequently increase carbon sequestration.” 

  

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