in mfa the term materials is often used in a broad sense so as to encompass all materialrelated flows arising at all stages of the material cycle it refers to both materials and products derived from natural resources that are used as inputs into human activities as well as residuals such as waste or pollutant emissions arising from their extraction and use and ecosystem inputs such as nutrients carbon dioxide and oxygen required for their extraction and use here the focus is on material resources that designate the usable materials or substances raw materials energy produced from natural resources