Abstract: Although endowed with abundant tidal resource, China’s tidal power generation industry has been largely lagging compared with other renewable energy alternatives such as small hydropower, photovoltaic power, wind power and biomass power. To probe the reasons behind this stagnancy, an emergy evaluation was conducted for the 4.1 MW Jiangxia Tidal Power Station (JTPS), the largest tidal power station in China and the fourth in the world. The evaluation results indicate that the total emergy use of this production system was 5.08×10^19 sej to generate 2.61×10¹³ J of electricity in 2014, of which renewable resources accounted for 17.77%. Thus, the transformity of electricity produced by this plant is 1.95×10⁶ sej·J^-1. The environmental loading ratio (ELR) and the emergy sustainability index (ESI) of the JTPS were 4.63 and 0.12 respectively, exhibiting a poorer environmental performance than other renewable energy power plants except photovoltaic power. These results reveal that tidal energy is a kind of lower quality and more decentralized energy and its current exploitation presents low environmental competitiveness. In such context, the development of tidal power in China should proceed with cautions and avoid largescale blind development. Nevertheless, R&D is needed to promote the technology development and ultimately utilize abundant tidal resource in an efficient and sustainable way.

Key words: Callosobruchus chinensis, protease inhibitor, chymotrypsin-like enzyme, total protease, trypsin-like enzyme