Carbon Footprint of Crop Production and the Significance for Greenhouse Gas Reduction in the Agriculture Sector of China

Abstract

World agriculture is facing a great joint challenge of ensuring food security and mitigating greenhouse gas emissions under climate change. Characterizing the carbon footprints of crop production by life cycle analysis is be critical for identifying the key measures to mitigate greenhouse gas emission while sustaining crop productivity in the near future. In this chapter, the carbon footprints of bulk crop production; individual staple crops of rice, wheat, and maize; as well as vegetable crops from China were analyzed using data from either statistical archive or of questionnaire survey for quantification of all carbon costs in a whole life cycle. Although the overall carbon footprint of crop production sector of China is much higher than that of the UK and USA, rice and wheat have significantly higher carbon footprints than maize. The nitrogen-fertilizer-induced footprint was shown to be the biggest contributor to the total carbon footprint for all the crops (more than 60 %), leaving a big space for mitigation of luxury emissions of N2O with nitrogen use in excess. Although the carbon footprint has quickly increased since 1970s, crop production did not show a positive response to increasing carbon cost. While reducing nitrogen chemical fertilizer use is apparently a key option to cut down the highly carbon-intensive agriculture, substitution of rice or wheat with maize would offer a final option to ensure both high cereal production and low carbon cost in China's crop production sector. There is an urgent need to depict the variation of carbon footprints for different cropping and farming systems, climate conditions, and the threshold of nitrogen luxury emissions for a certain crop.