Carbon and phosphorus footprint of the cotton production in Xinjiang, China, in comparison to an alternative fibre (Apocynum) from Central Asia

Abstract

Agriculture significantly contributes to greenhouse gas emissions and thus to climate change, directly through farm operations and indirectly through the energy needed to produce input materials, most prominently fertiliser, as well as through nitrous oxide (N2O) emissions from soils. Agriculture is the largest consumer of phosphorus, which is a non-renewable resource. Cotton accounts for one third of all natural and synthetic fibres of the total textile production. Today, Xinjiang, China, has become one of the most important cotton producers with highest yields worldwide. The aim of this study was to calculate the carbon (climate footprint and energy footprint) and phosphorus footprint of this high yielding cotton production and compare it to a theoretical production of an alternative fibre from Apocynum (local name: Kendyr or Kutra), which is a bast fibre plant native in Xinjiang and Central Asia. The data of the cotton production was collected through farm interviews during six years in Xinjiang. The data for Apocynum was compiled by literature from field experiments in the former Soviet Union. Cotton fibres, mainly due to high fertiliser inputs, caused a climate footprint of 4.43 kg CO2e/kg fibre, an energy footprint of 30.90 MJ/kg fibre, and a phosphorus footprint of 101 g P/kg fibre. The footprints of Apocynum are significantly lower with a climate footprint of 1.93 kg CO2e/kg fibre, an energy footprint of 21.85 MJ/kg fibre, and a phosphorus footprint of 1.6 g P/kg fibre. In cotton production, 63.9% of the climate footprint and 68.4% of the energy footprint are attributed to fertiliser production. Soil emissions of N2O account for another 22.2% of the climate footprint of cotton. The biggest potential to reduce carbon and phosphorus footprints of cotton production lie in reduced fertiliser application and re-use of plant residues. In the case of Apocynum, 65.1% of the climate footprint and 64.1% of the energy footprint are attributed to chemical treatment of the fibres in the extraction process.