Renewable Energy to examine ways of commercializing the use of this leftover material by converting it into biofuels. The unit also examined the potential use of poultry litter to generate energy and other products. Tyson's 2010 Sustainability Report said that it had reduced water use by 7.6 percent between October 2004 and 2009, and reduced wastewater related permit exceedances by 5.4 percent during 2007–2009. However, the company reported a 51.9 percent increase in violation notices related to wastewater, storm water, and drinking water. The company reduced landfill solid waste by 12.5 percent during 2008–2009. As of 2010, six of Tyson Foods' wastewater treatment facilities capture biogas via enclosed anaerobic lagoons. Four of the systems use the biogas as an alternative fuel to natural gas; during 2008–2009, the four facilities used 1.8 billion cubic feet of biogas, replacing 1.3 billion cubic feet of natural gas and saving the company approximately $9.1 million. According to Tyson's 2012 Sustainability Report, the company reduced total water use by 4.7 percent during 2011–2012, but normalized water use increased 1 percent over the same period. Through conservation efforts and closures, the company reduced water use by 10.9 percent between October 2004 and 2012. During 2010–2012, Tyson Foods reduced wastewater related permit exceedances by 48 percent and notices of violations by 86 percent. Tyson reduced greenhouse gas emissions by approximately 8 percent during 2010–2011, and the company cut 145 million truck miles via lightweight equipment purchases, packaging improvements, and use of rail transport. In 2013, Tyson paid nearly $4 million in fines due to eight separate incidents between 2006 and 2010 where it accidentally released anhydrous ammonia, an extremely hazardous substance which causes chemical-type burns. These releases killed at least one worker and injured nearly a dozen others. In Newsweek 2017 "green ranking", an environmental performance assessment of the largest public companies, Tyson Foods ranked number 223 in the U.S. and number 312 in the world. Tyson Foods worked with the World Resources Institute to set a goal for reducing greenhouse gas emissions 30 percent by 2030. The plan was accepted by the Science Based Targets initiative, a coalition of companies working to limit carbon emissions based on the goals of the Paris Agreement. According to Tyson's 2019 Sustainability Report, the company was on track to meet most of its sustainability goals and had decreased water use by 6.8 percent since 2015. Tyson Foods joined the United