Introduction

Nitrogen Fertilizers and Food Security

Synthetic fertilizers are a vital component of intensive agriculture and a necessity for global food production. Removal of nutrients by crops during growth necessitates the use of fertilizers to accelerate soil replenishment and so maintain the productivity of intensive agriculture. Of these, nitrogen fertilizers are especially important since available nitrogen is typically the limiting nutrient that inhibits soils from sustaining intensive crop growth (Yara, 2017). Without such synthetic fertilizers, it has been estimated that food production would only be sufficient to support half the global population (as of 2011) (Dawson and Hilton, 2011). With population growth predicted to continue in the medium- to long-term future (World Bank, 2018), food production is similarly expected to have to increase output. Simultaneously, the economic growth of less developed countries is resulting in more varied and calorie dense diets, similarly demanding higher productivity (Stewart and Roberts, 2012). Because of these challenges, the continued use of synthetic fertilizers within agriculture is expected for the foreseeable future.

Carbon Capture and Utilization

Continued fertilizer demand has further implications since practically all synthetic fertilizers are derived from fossil fuels. Processing of these fuels results in emission of greenhouse gases (GHGs) such as carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). Elevated atmospheric concentrations of GHGs have long been of serious concern. Their emission is a major cause of anthropogenic climate change phenomena (such as global warming), leading to environmental catastrophes such as droughts, glacial melting, rising sea levels, ocean acidification, etc. In the case of CO2, for example, current average global concentration is in excess of 410 ppm and, without abatement, is predicted to reach 750 ppm by 2100 (IPCC, 2018), leading to disastrous environmental effects. For this reason, there has been considerable motivation toward the widespread implementation of abatement strategies, including Carbon Capture and Storage (CCS) and Carbon Capture and Utilization (CCU). For CCS, CO2 is captured and stored in geological structures (e.g., depleted oil wells, gas fields, saline aquifers), potentially allowing expedient removal of large amounts of CO2 from the atmosphere (Leung et al., 2014). In contrast, for CCU the captured CO2 is processed into a variety of commercial products (e.g., methane, methanol, formaldehyde, polyurethanes, etc.) that offer an alternative to their fossil-derived equivalents (Styring and Jansen, 2011). Moving forward, it is believed that combined deployment of CCS and CCU (CCUS) (Mission Innovation, 2017) will be essential in order to achieve meaningful CO2 reductions within a sufficiently short timeframe to prevent irreversible damage due to climate change.