The continuous rise in crude oil prices and increasing environmental concerns have led to a sharp increase in global biodiesel production. With the growth of world biodiesel production, the issue of converting the main byproduct glycerin from biodiesel production processes into high-value-added chemicals has become a focus of research both domestically and internationally. Our research group has reported for the first time that glycerin can be efficiently reduced to formic acid in a hydrothermal reaction, which is then converted into high-value-added lactic acid with nearly 90% yield. Lactic acid can further be prepared into biodegradable polylactic acid plastics. This project has a simple process, convenient operation, fast reaction speed, and also reduces secondary pollution caused by waste alkali emissions from biodiesel production processes on the environment; it solves the problem of low-cost byproduct waste glycerin disposal faced by biodiesel factories, converting waste glycerin into high-value-added chemicals simultaneously, promoting the carbon cycle of nature, and has high application value. Application or Prospects: The production of biodiesel in China increased by 357% from 2002 to 2007, with an estimated output of about 200,000 tons in 2010. For every 9 kilograms of biodiesel produced, it is estimated that 1 kilogram of crude glycerin by-product can be obtained. Therefore, in 2010, China's biodiesel by-product waste glycerin reached 20,000 tons. At the same time, the market potential for polylactic acid plastics is estimated to be 9 billion pounds per year, making it one of the most promising biodegradable plastics. Currently, the world production of lactic acid is about 50,000 tons per year; the global demand for lactic acid exceeds 60,000 tons. With the increase in lactic acid production, polylactic acid plastics are expected to replace or partially replace materials such as polyethylene, polypropylene, and polystyrene in plastic products in the future, offering a very broad market prospect. For example, if it were to completely replace polyethylene, the annual production of lactic acid would need to exceed 50 million tons. Moreover, with the rapid development of China's economy, the demand for lactic acid will continue to increase significantly. Therefore, the application prospects for converting waste glycerin, a byproduct of the bioindustry, into lactic acid are broad. CO2 is the greenhouse gas with the greatest impact on global climate change, so researching technologies that rapidly and effectively reduce CO2 into organic resources has significant practical significance. On the other hand, waste glycerin is a major byproduct of biodiesel, and as the biodiesel industry develops, its low-cost main byproduct, waste glycerin, has become a challenge faced by biodiesel enterprises. This project utilizes environmentally friendly hydrothermal technology, using waste glycerin or isopropanol as reducing agents, and takes advantage of the characteristics of high-temperature and high-pressure water to catalytically convert CO2 into formic acid while simultaneously transforming waste glycerin into lactic acid.