Ecosystem-based carbon footprinting of marine engineering projects

Dredging projects use large amounts of fuel, which leads to substantial carbon dioxide (CO₂) emissions. Until now, reducing the carbon footprint of dredging projects has mainly involved investigating the possibilities of dredging schemes and vessels that are more fuel efficient. A reduction in the order of 10–20% may be within reach, most of it is a win–win situation since fuel reduction will also reduce costs. A further reduction in carbon dioxide emissions may be possible on a project-by-project basis but will involve a trade-off between dredging costs and carbon dioxide emissions. Marine engineering projects also have an impact on primary production and formation of organic carbon and on sedimentation processes and burial of organic carbon in sediments. Both impacts influence carbon sequestration and can be a substantial or even overriding factor in the ‘carbon footprint’ of a project. The carbon footprint of a marine engineering project is often larger and more complex than previously anticipated. However, a more comprehensive carbon footprint also shows that a significant reduction in carbon dioxide emissions is possible when the designs and dredging and maintenance schemes stimulate sequestration of organic carbon in the wider environment.