The costing of carbon credits from ocean nourishment plants.

Ocean nourishment is a process for stimulating the sequestration of atmospheric carbon dioxide in the deep ocean by providing the nutrients needed to enhance the production of phytoplankton. The carbon dioxide sink thus created, can be used to generate tradeable carbon credits. The costs of sequestering carbon by the process of ocean nourishment have been estimated using as a basis, the previous experience in nitrogen fixing of Toyo Engineering Corporation. While there are uncertainties about the biological uptake efficiency, these introduce only a moderate uncertainty in our overall estimates of costs. The major determinants of the costs are the interest that must be paid on capital and the cost of the feedstock, natural gas. We have used for discussion purposes, an interest rate of 4-8% per annum and natural gas costs of US$0.5-$2 per GJ. The costs of carbon credits lie in the range US$6.70-$12.40 per tonne of carbon dioxide emissions sequestered. It should be noted that we have adopted the measure of carbon avoided by non-emission, because of the complex partitioning of anthropogenic carbon between the atmosphere, land and ocean.