Sustainable N fertilizer production based on a loop: Straw - biogas – ‘Haber-Bosch’ process

Abstract

CONTEXT: A concept was presented to produce N fertilizer by digesting straw in a biogas plant and transporting bio-methane to a fertilizer plant through a gas grid substituting natural gas.OBJECTIVE: The rational was to find out if straw, a residue not infringing on food production and not needing extra cropland, converted to methane in a biogas reactor, is a viable option for ammonia synthesis.METHODS: Scenarios calculations were based on straw from 1 ha wheat producing 7 Mg of grain using 150 kg of fertilizer N. Removal rates of straw were 60 or 100%. Digestion residues were returned to fields within a radius of 50 km. Three scenarios with varying straw removal and low to high efficiency of the biogas and fertilizer plant were assessed.RESULTS AND CONCLUSIONS: A sensitivity analysis showed the combination of a medium to high efficient biogas and fertilizer plant using between 3.5 and 7 Mg straw covered the energy need for crop management, transportation of straw and digestate and N fertilizer production and still delivered a surplus of 838?9192 kWha ha-1. The amount of 1 Mg of straw enabled the production of 94 to 173 kg fertilizer N.SIGNIFICANCE: Use of straw can be a useful alternative for N fertilizer production making agriculture more sustainable.

Keywords

Straw digestion; Biogas-based N fertilizer; Total energy balance; Sensitivity; Recirculation

Published in

Agricultural Systems
2021, volume: 190, article number: 103100
Publisher: ELSEVIER SCI LTD

SLU Authors

• Kirchmann, Holger

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    

Global goals (SDG)

SDG2 Zero hunger
SDG7 Affordable and clean energy

UKÄ Subject classification

Agricultural Science

Publication identifier

• DOI: https://doi.org/10.1016/j.agsy.2021.103100

Permanent link to this page (URI)

https://res.slu.se/id/publ/112245