Carbon footprints of crops from organic and conventional arable crop rotations - using a life cycle assessment approach
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- 作者：Marie Trydeman Knudsen ; Andreas Meyer-Aurich ; J酶rgen E. Olesen ; Ngonidzashe Chirinda ; John E. Hermansen
- 关键词：Organic ; Crop rotations ; Biogas ; Conventional ; LCA ; Greenhouse gas emissions
- 刊名：Journal of Cleaner Production
- 出版年：1 February, 2014
- 年：2014
- 卷：64
- 期：Complete
- 页码：609-618
- 全文大小：820 K
文摘
Many current organic arable agriculture systems are challenged by a dependency on imported livestock manure from conventional agriculture. At the same time organic agriculture aims at being climate friendly. A life cycle assessment is used in this paper to compare the carbon footprints of different organic arable crop rotations with different sources of N supply. Data from long-term field experiments at three different locations in Denmark were used to analyse three different organic cropping systems (鈥楽lurry鈥? 鈥楤iogas鈥?and 鈥楳ulching鈥?, one conventional cropping system (鈥楥onventional鈥? and a 鈥淣o input鈥?system as reference systems. The 鈥楽lurry鈥?and 鈥楥onventional鈥?rotations received slurry and mineral fertilizer, respectively, whereas the 鈥楴o input鈥?was unfertilized. The 鈥楳ulching鈥?and 鈥楤iogas鈥?rotations had one year of grass-clover instead of a faba bean crop. The grass-clover biomass was incorporated in the soil in the 鈥楳ulching鈥?rotation and removed and used for biogas production in the 鈥楤iogas鈥?rotation (and residues from biogas production were simulated to be returned to the field).
A method was suggested for allocating effects of fertility building crops in life cycle assessments. The results showed significantly lower carbon footprint of the crops from the 鈥楤iogas鈥?rotation (assuming that biogas replaces fossil gas) whereas the remaining crop rotations had comparable carbon footprints per kg cash crop. The study showed considerable contributions caused by the green manure crop (grass-clover) and highlights the importance of analysing the whole crop rotation and including soil carbon changes when estimating carbon footprints of organic crops especially where green manure crops are included.