Can intensification reduce emission intensity of biofuel through optimized fertilizer use? Theory and the case of oil palm in Indonesia

Abstract

Closing yield gaps through higher fertilizer use increases direct greenhouse gas emissions but shares the burden over a larger production volume. Net greenhouse gas (GHG) footprints per unit product under agricultural intensification vary depending on the context, scale and accounting method. Life cycle analysis of footprints includes attributable emissions due to (i) land conversion ('fixed cost'); (ii) external inputs used ('variable cost'); (iii) crop production ('agronomic efficiency'); and (iv) postharvest transport and processing ('proportional' cost). The interplay between fixed and variable costs results in a nuanced opportunity for intermediate levels of intensification to minimize footprints. The fertilizer level that minimizes the footprint may differ from the economic optimum. The optimization problem can be solved algebraically for quadratic crop fertilizer response equations. We applied this theory to data of palm oil production and fertilizer use from 23 plantations across the Indonesian production range. The current EU threshold requiring at least 35% emission saving for biofuel use can never be achieved by palm oil if produced: (i) on peat soils, or (ii) on mineral soils where the C debt due to conversion is larger than 20 Mg C ha À1 , if the footprint is calculated using an emission ratio of N 2 O-N/N fertilizer of 4%. At current fertilizer price levels in Indonesia, the economically optimized N fertilizer rate is 344-394 kg N ha À1 , while the reported mean N fertilizer rate is 141 kg N ha . Sustainable weighting of ecology and economics would require a higher fertilizer/yield price ratio, depending on C debt. Increasing production by higher fertilizer use from current 67% to 80% of attainable yields would not decrease footprints in current production conditions.

Palm oil expansion in tropical forest margins or sustainability of production? Focal issues of regulations and private standards

“…While agricultural expansion into tropical forest areas has clashed with conservation goals for a long time (Tomich et al 1998), the palm oil debate increased in intensity when biofuel policies opened up loopholes in partial accounting for emissions in the mid 2000's. Emission reduction by fossil fuel substitution in importing countries could be accounted for, but the emissions caused elsewhere stayed outside of the accounting scheme (Searchinger et al 2009;van Noordwijk et al 2016). Actual use of palm oil as biodiesel has absorbed a relatively small part of the global production, but it has faced a recent increase to 45% of palm oil imported to Europe 1 .…”

Deforestation and agriculture in the tropics: carbon emissions and options for mitigation

“…Calculating the emissions intensity of crops is a useful tool to understand the impact of production and also to set targets for mitigation (Carlson et al 2016). Different outcomes in terms of the best options for mitigation can be found by using different accounting methods (van Noordwijk et al 2016), so using a number of approaches and comparing results can be useful for decision makers. The 'carbon debt' when establishing oil palm plantations in Indonesia has been discussed by van Noordwijk et al (Figure 5.1) (van Noordwijk et al 2016).…”

“…Different outcomes in terms of the best options for mitigation can be found by using different accounting methods (van Noordwijk et al 2016), so using a number of approaches and comparing results can be useful for decision makers. The 'carbon debt' when establishing oil palm plantations in Indonesia has been discussed by van Noordwijk et al (Figure 5.1) (van Noordwijk et al 2016). In this case an optimal fertilizer level is determined by the production levels at which net emission savings per unit of biofuel are maximized.…”

“…Palm oil produced on peat soils, and in some cases mineral soils was found not to meet the current EU emissions threshold for biofuel production, which requires at least 35% emissions savings compared to fossil fuels. In van Noordwijk et al (van Noordwijk et al 2016), an optimum fertilizer application rate can be identified for a given relationship between fertilizer and yield. Attention to other management choices can, however, shift the relationship between fertilizer and yield, as current fertilizer use on smallholder oil palm farms can be excessive and inefficient (Soliman et al 2016).…”

Is there life after hype for Jatropha? Exploring growth and yield in Indonesia

“…N 2 O emission from fertiliser is the major contributor (Reinhardt et al, 2007;Achten et al, 2010b;Van Noordwijk et al, 2016), with a greenhouse effect per molecule that is 320 times that of CO 2 (Zah et al, 2007). In the biodiesel production stage, transesterification accounts for 11 % (Achten et al, 2010b) and 17 % (Ndong et al, 2009) of total emissions.…”