Estimation of the variability in global warming potential of worldwide crop production using a modular extrapolation approach

Greenhouse gas emissions from conventional and organic cropping systems in Spain. I. Herbaceous crops

“…The production of fertilizers was the main factor responsible for the differences observed, while C sequestration was similar between both types of management on an area basis. Our results for conventional grain production are in the lower range of global estimations by Nemecek et al (2012) and in accordance with studies under Mediterranean climate such as that of Biswas et al (2008). Legumes are usually cultivated in rotation with cereals, and their management is similar to theirs in very aspects, particularly machinery use (Table 1).…”

“…Straw and manure have a high content of easily decomposable C, which is associated to methane emissions in rice paddies and therefore to a high scaling factor according to IPCC (2006) methodology. Conventional rice emissions are in the lower range of the global estimations reported by Nemecek et al (2012), while organic rice emissions are in the upper range.…”

Greenhouse gas emissions from conventional and organic cropping systems in Spain. II. Fruit tree orchards

“…Product-based emissions of treenuts had averages of 972 and 955 g CO 2 e/kg under conventional and organic management. The calculated values agree with world average emissions for almonds and hazelnuts estimated by Nemecek et al (2012) and were lower than those associated to almond production in California reported by Venkat (2012). Higher emissions in California can be explained by a heavier use of water and pesticides and a lower productivity.…”

“…Although cover crops were adopted in only 64 % of the cases, internal carbon inputs represented more than half of total carbon inputs in organic citrus systems. Emissions per kilogram of product were relatively low in citrus fruits due to high yields, and average conventional crop emissions of 147 g CO 2 e/kg were comparable with the global estimation by Nemecek et al (2012), while emissions of organic citrus products averaged 83 g CO 2 e/kg. Both values are very similar to those obtained by Pergola et al (2013) in Sicily, despite these authors did not consider carbon sequestration.…”

“…2a). It is worth noting the great variability between cases, and especially the high carbon footprint of conventional banana production, of 641 g CO 2 e/kg, which was associated to a high consumption of fertilizers, and can be compared with 49 g/kg of organic bananas (data not shown) and with a global estimation of 250 g CO 2 e/kg (Nemecek et al 2012). …”