Traditional leather and its alternatives are typically obtained from animals and synthetic polymers. Leather can be considered a co-product of meat production with both livestock farming and the leather production process increasingly considered to be ethically questionable and environmentally unfriendly (e.g. deforestation for grazing, greenhouse gas emissions, use of hazardous substances in the tanning process). The production of synthetic leather materials from plastics such as polyvinyl chloride (PVC) or polyurethane (PU) also depend on chemicals derived from fossil fuels.