Modeling agricultural energy demand within the IMAGE 3.0 framework

Abstract

Growing international consensus on the need to mitigate global climate change recently led UNFCCC parties to commit to an increase in global mean surface temperature (MST) well below 2ᵒC compared to pre-industrial levels. In this context, integrated assessment models (IAMs) can provide valuable insights in the long-term impacts of human development on climate change. This thesis aims to model regional final energy demand (FED) for two main agricultural processes, irrigation and synthetic fertilizer production, within the IAM IMAGE 3.0. This is done in a new Agricultural Energy Demand (AED) module. The methodology for irrigation energy demand consists of two main components; water conveyance from a withdrawal source to the field; and subsequent distribution across the field by an application system. The former uses aquifer and groundwater table depths to determine specific energy consumption (SEC), the latter a region specific mix of three field application systems; surface irrigation, sprinkler and drip. These systems are characterized by zero, high and low SECs respectively. Since the production of ammonia dominates world synthetic fertilizer energy demands, it is modelled in more detail than other fertilizer types. At the heart of the ammonia energy demand methodology is a multinomial logit equation which assigns regional market shares to four ammonia plant types; natural gas, coal, heavy oil and solid biomass. SEC for each of these plant types is determined by a technological learning curve. Additionally, each plant type can be equipped with a carbon capture and storage (CCS) add-on, which reduces net CO2 emissions. Model runs are made for a new set of human development scenarios called the Shared Socioeconomic Pathways (SSPs). These include three plausible baseline scenarios and one that is constrained by the 2ᵒC MST limit described earlier. Main results: projected global agricultural energy demand is dominated by ammonia production in all scenarios, and energy demand is higher for irrigation than for the production of all other fertilizer types combined. The SSP1 Sustainability scenario projects the lowest global AED, while the SSP3 Regional Rivalry and RCP2.6 2degree scenarios project the highest. These differences are mainly explained by the varying energy demands for ammonia production. The high ammonia energy demand in the 2ᵒC MST limit scenario is explained by its high deployment of biomass plants, which have a high SEC but very low net CO2 emissions. At the moment, the AED module covers an estimated 58.5% of world total AED and 2.0% of grand total final energy demand.