Biomass production in plantations: Land constraints increase dependency on irrigation water

Yvonne Jans,Göran Berndes,Dieter Gerten,Jens Heinke,Wolfgang Lucht

doi:10.1111/gcbb.12530

Abstract

AbstractIntegrated assessment model scenarios project rising deployment of biomass‐using energy systems in climate change mitigation scenarios. But there is concern that bioenergy deployment will increase competition for land and water resources and obstruct objectives such as nature protection, the preservation of carbon‐rich ecosystems, and food security. To study the relative importance of water and land availability as biophysical constraints to bioenergy deployment at a global scale, we use a process‐detailed, spatially explicit biosphere model to simulate rain‐fed and irrigated biomass plantation supply along with the corresponding water consumption for different scenarios concerning availability of land and water resources. We find that global plantation supplies are mainly limited by land availability and only secondarily by freshwater availability. As a theoretical upper limit, if all suitable lands on Earth, besides land currently used in agriculture, were available for bioenergy plantations (“Food first” scenario), total plantation supply would be in the range 2,010–2,300 EJ/year depending on water availability and use. Excluding all currently protected areas reduces the supply by 60%. Excluding also areas where conversion to biomass plantations causes carbon emissions that might be considered unacceptably high will reduce the total plantation supply further. For example, excluding all areas where soil and vegetation carbon stocks exceed 150 tC/ha (“Carbon threshold savanna” scenario) reduces the supply to 170–290 EJ/year. With decreasing land availability, the amount of water available for irrigation becomes vitally important. In the least restrictive land availability scenario (“Food first”), up to 77% of global plantation biomass supply is obtained without additional irrigation. This share is reduced to 31% for the most restrictive “Carbon threshold savanna” scenario. The results highlight the critical—and geographically varying—importance of co‐managing land and water resources if substantial contributions of bioenergy are to be reached in mitigation portfolios.

Highlights

Visions on a circular and bio‐based economy have been formulated in response to concerns about resource scarcity and impacts associated with unsustainable use of renewable and nonrenewable resources (Geissdoerfer, Savaget, Bocken, & Hultink, 2017; German Bioeconomy Council, 2018; Ghisellini, Cialani, & Ulgiati, 2016; Gregson, Crang, Fuller, & Holmes, 2015; Hetemäki et al, 2017; Hobson, 2016; Hobson & Lynch, 2016; Priefer, Jörissen, & Frör, 2017)
Intergovernmental Panel on Climate Change (IPCC) WG3 reported in the Fifth Assessment Report that widespread deployment of bioenergy with CO2 capture and storage (BECCS) in climate stabilization scenarios indicate that this option can become important if the needed technologies and resources are available (Edenhofer et al, 2014)
The effect of constraining the availability of water resources depends on land availability, for example, a doubling of the ecological flow requirements to 60% of renewable freshwater resources reduces the supply from irrigated biomass plantations significantly more (37%) in the CTS scenario compared to FF

Summary

| INTRODUCTION

Visions on a circular and bio‐based economy have been formulated in response to concerns about resource scarcity and impacts associated with unsustainable use of renewable and nonrenewable resources (Geissdoerfer, Savaget, Bocken, & Hultink, 2017; German Bioeconomy Council, 2018; Ghisellini, Cialani, & Ulgiati, 2016; Gregson, Crang, Fuller, & Holmes, 2015; Hetemäki et al, 2017; Hobson, 2016; Hobson & Lynch, 2016; Priefer, Jörissen, & Frör, 2017). Population development (Bodirsky et al, 2015; Lutz, 2013), the evolution of consumer behavior, for example, diet (Wirsenius, Azar, & Berndes, 2010), and economic and technological development (Azar, Lindgren, Larson, & Möllersten, 2006) together determine future biomass demands for food and other bio‐ based products Side factors such as crop yields, water use efficiency, and adaptation to specific growing conditions (Beddington et al, 2012; Müller et al, 2015; Neumann, Verburg, Stehfest, & Müller, 2010) determine how this biomass demand in turn translates into demands for land, water, and other resources. Our scenarios should be understood as indicative of how different degrees of access to, and management of, land and water resources influence the plantation supply achievable at global and regional level

| MATERIALS AND METHODS

| RESULTS

H M L RF CTS

Findings

| DISCUSSION