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Task 4. Bioenergy and Soil Fertility

Impact and Rationale. Impacts of large scale bioenergy production on soil fertility, which may be positive or negative, are important to consider in assessing the feasibility of large scale bioenergy production. These include:

Approach. Fertilizer demand associated with bioenergy production on the scale contemplated by the GSB project has received little attention. A key issue to be considered is how bioenergy production at this scale would impact depletion of global fertilizer stocks. We will seek to identify bioenergy crops and supply chains that would not significantly accelerate (or perhaps decelerate) fertilizer stock depletion, and may well also identify crops and supply chains that would accelerate such depletion. Rates of inorganic element application and/or removal upon harvest will be compiled for production of different bioenergy feedstocks, including representative row crops and cellulosic feedstocks. These data will then be used to calculate element requirements on a per ton or per unit product (e.g., per m3 of fuel) basis. It is anticipated that these requirements will be quite different for different feedstocks. In conjunction with considering nutrient loss and the potential for recycling of inorganic fertilizer components (Anex et al., 2007), we will evaluate whether various bioenergy production options would or would not meaningfully accelerate depletion of fertilizer reserves when implemented at large scale. Here again, coordination of work undertaken as part of the GSB project is expected to be coordinated with activities and researchers involved other projects and GSB sponsor organizations.

Use of biomass residues as bioenergy feedstocks will initially be considered with respect to sugar cane bagasse/trash, corn stover, and the fronds, trunks, and fruit bunches associated with palm oil production. These represent substantial potential sources of biomass, but also require careful attention to allowable residue removal rates and other management practices. Consideration of additional residues may be undertaken as the project progresses. However, at this time the goal of the GSB project is to examine issues related to harvesting a few representative and potentially important residues rather than performing a comprehensive inventory.

Land under perennial crops generally accumulates carbon and gains or regains fertility under proper management. There is considerable that these desirable impacts can be accelerated by harvest in temperate climates, although there are less data available for warmer climates. The project will examine the feasibility and opportunities for using bioenergy production to remediate degraded land, ideally in the context of both developed and developing countries. One can ask, for example:

In the next quarter century, what is the magnitude of fertility, carbon, food, and energy benefits from land that would produce more food if planted for a fraction of the time in perennial energy crops than if it were not?

Approaching such questions will entail integration with state-of-the-art models for solid carbon and soil fertility as impacted by management practices, likely drawing on data and analyses developed at multiple scales.

Leadership. Task 4 activities are being led by Heitor Cantarella, Agronomic Institute of Campinas, University of Campinas, Brazil. Co-leaders may be added in the future.

References

Last Updated August 14, 2012