Availability of inputs
Land is not the only factor of production needed by BECCS deployment: the cultivation of new energy crops is likely to lead to increased agricultural demand for water and nitrogen fertilizer. A study of the use of switchgrass for BECCS feedstock estimated that 200 million ha (about half the total cropland in the US) would be needed to remove 3.7 GtCO2/year; the process would consume 20 per cent of global fertilizer production, itself a major source of emissions, and require 4 trillion m3/year of water, an amount equal to current total global water withdrawals for irrigation.65 Furthermore, CCS itself requires the use of water; one estimate suggested that the amount of water required to sequester 12 GtCO2/year would be equivalent to approximately 3 per cent of total water consumption currently associated with human activities – though some water could be recycled from storage operations.66
In fact, estimates of the total water footprint of BECCS vary widely, and are highly dependent on the biomass type and region of production. Three different studies estimated, respectively, water demand of 0.72 trillion m3, 3.6–9.7 trillion m3 and 5.3–24.4 trillion m3 to sequester 12 GtCO2/year.67 Excessive water withdrawals for BECCS feedstock production could also lead to freshwater ecosystem degradation and aquatic biodiversity loss; even if withdrawals are lower, water pollution from fertilizer use is likely.
65 Reviewed in US National Research Council (2015), Climate Intervention.
66 Smith, P., Davis, S. J., Creutzig, F., Fuss, S., Minx, J., Gabrielle, B., Kato, E., Jackson, R. B., Cowie, A., Kriegler, E., van Vuuren, D. P., Rogelj, J., Ciais, P., Milne, J., Canadell, J. G., McCollum, D., Peters, G., Andrew, R., Krey, V., Shrestha, G., Friedlingstein, P., Gasser, T., Grübler, A., Heidug, W. K., Jonas, M., Jones, C. D., Kraxner, F., Littleton, E., Lowe, J., Moreira, J. R., Nakicenovic, N., Obersteiner, M., Patwardhan. A., Rogner, M., Rubin, E., Sharifi. A., Torvanger, A., Yamagata. Y., Edmonds, J. and Yongsung, C. (2016), ‘Biophysical and economic limits to negative CO2 emissions’, Nature Climate Change, 6(1), pp. 42–50, doi: 10.1038/Nclimate2870.
67 Fajardy et al. (2019), BECCS Deployment: A Reality Check.