Download or read book Environmental Impacts of Ocean Disposal of CO2 written by E. Eric Adams and published by . This book was released on 1996 with total page 375 pages. Available in PDF, EPUB and Kindle. Book excerpt: One option to reduce atmospheric CO 2 levels is to capture and sequester power plant CO2. Commercial CO2 capture technology, though expensive, exists today. However, the ability to dispose of large quantities of CO 2 is highly uncertain. The deep ocean is one of only a few possible CO2 disposal options (others are depleted oil and gas wells or deep, confined aquifers) and is a prime candidate because the deep ocean is vast and highly unsaturated in CO 2. Technically, the term 'disposal' is really a misnomer because the atmosphere and ocean eventually equilibrate on a time scale of 1000 years regardless of where the CO 2 is originally discharged. However, peak atmospheric CO 2 concentrations expected to occur in the next few centuries could be significantly reduced by ocean disposal. The magnitude of this reduction will depend upon the quantity of CO 2 injected in the ocean, as well as the depth and location of injection. Ocean disposal of CO2 will only make sense if the environmental impacts to the ocean are significantly less than the avoided impacts of atmospheric release. In this project, we examined these ocean impacts through a multi-disciplinary effort designed to summarize the current state of knowledge. In the process, we have developed a comprehensive method to assess the impacts of pH changes on passive marine organisms. This final report addresses the following six topics: CO2 loadings and scenarios, impacts of CO2 transport, near-field perturbations, far-field perturbations, environmental impacts of CO, release, and policy and legal implications of CO2 release. While there are several important environmental impacts of ocean disposal of CO2, the acidification around the release point may be the most important. However, the size and severity of the impacted area varies substantially with the injection scenario. We have quantified the impacts of various injection scenarios relative to each other through mortality measures. Based on available data, it appears possible to inject CO2 into the deep ocean in such a way as to yield negligible environmental impacts. The key conclusions of this research are: * The major environmental impact of ocean CO 2 disposal would derive from the lowering of pH caused by the reaction of CO, with seawater. Depending on the method of release, pH can be reduced to as low as about 4 very near the injection point from its ambient value of about 8. * Impacts would be felt primarily by those organisms which reside at depths of 1000 m or greater and are unable to avoid regions of low pH near the point of injection (e.g., zooplankton, bacteria and benthos). In comparison with the size of the world's oceans, the areas of acute impact would be very small for all injection scenarios. Nonetheless, there would be significant differences among scenarios, with the least impact predicted from those methods which disperse the CO2 as it is being injected and which keep it off the seabed. Based on available data, it appears possible to design a discharge system which effectively eliminates mortality by spreading the CO2 sufficiently in either the vertical or horizontal directions, e.g., by releasing it from either an inclined pipe towed * by a moving ship or a fixed pipe laid on the sea floor. The precautionary principle , suggests that future R&D efforts be focused on such methods. * At global scales, anthropogenic emissions of CO 2 that are occurring today will cause a gradual decline in average ocean pH of about 0.5 units over the next several centuries. Direct injection of CO 2 to the ocean will perturb the system by less than another 0.1 pH unit. The impacts from the combined pH changes will not cause mortality, but could cause sub-lethal impacts such as shifting population structure, decreased reproduction rates, etc. The regional impacts would be site-specific, as would the effectiveness of sequestration (tendency of the CO 2 to remain in the ocean). In general such chronic impacts will be harder to predict than the more acute impacts expected in the near-field. * Additional impacts of ocean CO 2 disposal were identified including increased concentrations of trace gases carried with the CO2, benthic disruption during outfall construction, disturbances to marine organisms caused by injection devices, plumes or hydrated CO 2 particles, and accidents associated with CO 2 transport. While such impacts, and possibly others, would need to be studied on a project-specific basis, they are expected to be minor. We also analyzed the possibility of a Lake Nyos-type of eruption, whereby large quantities of CO2-enriched seawater (or liquid CO 2 itself) stored in the ocean might accidentally rise to the surface, and result in asphyxiation; it was concluded that such an incident could not occur with ocean CO2 disposal. * The viability of ocean CO2 disposal as a greenhouse gas mitigation option may ultimately hinge on social and political considerations. Although there are no provisions which specifically prohibit ocean CO2 disposal, international acceptance will require several steps: the public must believe that the threat of global change is real, they must be convinced that there are no other easy mitigation options, and it must be demonstrated that the environmental impacts of ocean CO2 disposal are significantly less than the impacts of increased build-up of CO 2 in the atmosphere. Such acceptance can only occur if the public is included in the ongoing research and debate on this topic. The results presented in this report are just one piece of information that is required in doing a comprehensive analysis of the CO 2 ocean disposal option. Other important pieces include: effects of the localized impacts investigated here on larger ocean ecosystems, benefits of reduced atmospheric CO 2 emissions in terms of reduced risk of possible climate and ocean ecosystem change, and the cost of ocean disposal compared to alternate mitigation options. By doing objective and comprehensive studies of these issues, we are building a knowledge base that will allow informed decisions to be made if and when more stringent CO 2 emission controls are required.