The Department conducted the 2017 NYC Residential, School, and NYCHA (NYC Housing Authority) Waste Characterization Study over three seasons: spring, summer, and fall. This study builds on decades of research and analysis into the evolving composition of NYC's waste stream. The study team hand sorted samples into 70 main sort categories. Results are presented in absolute terms as the quantity by weight of each material type. The quantity of each material is calculated by applying the percent composition to the total quantity of DSNY collections for fiscal year 2017 (July 2016-June 2017).