Energy Management and Operational Planning of an Ecological Engineering for Carbon Sequestration in Coastal Mariculture Environments in China

Abstract

China is now accelerating the development of an ecological engineering for carbon sequestration in coastal mariculture environments to cope with climate change. Artificial upwelling as the ecological engineering can mix surface water with bottom water and bring rich nutrients to the euphotic zone, enhance seaweed growth in the oligotrophic sea area, and then increase coastal carbon sequestration. However, one of the major obstacles of the artificial upwelling is the high energy consumption. This study focused on the development of energy management technology for air-lift artificial upwelling by optimizing air injection rate. The fundamental principle underlying this technology is that the mode and intensity of air injection are adjusted from the feedback of information on velocity variation in tidal currents, illumination, and temperature of the surface layer. A series of equations to control air injection was derived based on seaweed growth and solar power generation. Although this finding was originally developed for the air-lift artificial upwelling, it also can be used in other areas of engineering, such as water delivery, aeration, and oxygenation. The simulations show that using a variable air injection rate can lift more nitrogen nutrients of 28.2 mol than using a fixed air injection rate of 26.6 mol, mostly with the same energy cost. Using this control algorithm, the changed temperature and dissolved oxygen profiles prove the effective upwelling in the experiments and the average weights of kelp are 33.1 g in the experimental group and 10.1 g in the control group. The ecological engineering was successfully increasing crop yield for carbon sequestration in coastal mariculture environments.

Nutrient Removal from Chinese Coastal Waters by Large-Scale Seaweed Aquaculture Using Artificial Upwelling

“…The rising bubble plume transports the nutrient-rich bottom water or porewater to the surface, which can enhance the nutrient concentration in the euphotic layer. The detailed structure can be found in Lin et al (2019) [15]. In this experiment, the total area of kelp aquaculture is 48,000 m 2 , of which 8400 m 2 are attributable to the artificial upwelling distribution area.…”

“…Further work will have to determine the influence of the water turbidity, tidal current velocity, and other factors on the air-lift efficiency. Actually, we have done some preliminary research in this area, the detailed information can be found in Lin et al (2019) [15].…”

Review of Artificial Downwelling for Mitigating Hypoxia in Coastal Waters

“…It was supported strongly by the Japanese government and the local fisherman cooperative organizations, so the technology matured in regard to operation practice for the last ten years. However, there are also some drawbacks, including (1) it is not cost-effective in practice; (2) the working range of the DCG system is limited by the topography, therefore, if it is applied in enclosed and semi-enclosed water body, the DCG system will get very good effects; (3) The complex mechanical and electrical system and its active control system is needed as the reliability and safety is a big problem in the ocean [79]; (4) the long pipe may be twisted or broken.…”

Numerical Studies on the Suitable Position of Artificial Upwelling in a Semi-Enclosed Bay

“…An unstructured grid finite-volume coastal ocean model (FVCOM) was used to understand the effect of the artificial upwelling. This model was developed originally by Chen et al [23] and efficient in resolving complex estuaries and coastal oceans dynamics. The unstructured triangular grid system can successfully embody the islands and barriers with complex topographies.…”