Sustainable land use and viability of biojet fuels

Abstract

Decarbonizing aviation requires, among other strategies, use of low-carbon liquid fuels, since electrified propulsion of large aircraft is not yet viable. However, commercialization of such ‘sustainable aviation fuels’ is lagging due to uncertainty about their potential. Here, we integrate land-use assessment, hydroclimate and ecosystem modelling and economic optimization in a systems framework to better characterize the biojet-fuel potential of cellulosic feedstocks. Planting 23.2 Mha of marginal agricultural lands in the United States—roughly the land area of Wyoming—with the grass miscanthus satisfies the country’s projected 2040 jet-fuel demand (30 billion gallons yr−1) at an average cost of US$4.1 gallon−1. Centred in the Midwest region, this marginal land base is a mix of croplands (7.2 Mha) and non-croplands (16 Mha), whose conversion into miscanthus delivers productive biomass, regional cooling without soil moisture loss and the lowest system greenhouse gas emissions (at US$50 tCO2e−1 carbon price). It is unsustainable to source the same quantity of miscanthus biomass through marginal land conversions in the Plains region. Sustainability considerations generate different land conversion patterns than expected from a purely economic vantage point. Integrated approaches, such as used here, are imperative to realistically evaluate the sustainability of bio-based alternative feedstocks. Aviation is a major contributor to climate change. This study assesses the potential of bioenergy crops planted in the US Midwest to meet projected US jet-fuel demand in 2040, finding that planting roughly 23.2 million hectares of marginal land with miscanthus would meet this need.