Redistributing Phosphorus in Animal Manure from a Livestock-Intensive Region to an Arable Region: Exploration of Environmental Consequences

Ola Stedje Hanserud,Helge Brattebø,Kari-Anne Lyng,Jerke W De Vries,Anne Falk Øgaard

doi:10.3390/su9040595

Abstract

Specialized agricultural production between regions has led to large regional differences in soil phosphorus (P) over time. Redistribution of surplus manure P from high livestock density regions to regions with arable farming can improve agricultural P use efficiency. In this paper, the central research question was whether more efficient P use through manure P redistribution comes at a price of increased environmental impacts when compared to a reference system. Secondly, we wanted to explore the influence on impacts of regions with different characteristics. For this purpose, a life cycle assessment was performed and two regions in Norway were used as a case study. Several technology options for redistribution were examined in a set of scenarios, including solid–liquid separation, with and without anaerobic digestion of manure before separation. The most promising scenario in terms of environmental impacts was anaerobic digestion with subsequent decanter centrifuge separation of the digestate. This scenario showed that redistribution can be done with net environmental impacts being similar to or lower than the reference situation, including transport. The findings emphasize the need to use explicit regional characteristics of the donor and recipient regions to study the impacts of geographical redistribution of surplus P in organic fertilizer residues.

Highlights

Animal manure is a key component in cycling phosphorus (P) between animals and crops
We explored the effect on all scenarios of (i) applying manure products at the recipient farm according to N content instead of P content, as N-based fertilizer application is more common practice, and (ii) optimal soil P levels at both the donor and recipient farm, which implies balanced fertilization (P fertilizer application equals removal of P in crop yields)
Better co-location of animal and crop farming would obviously reduce transport-related emissions associated with manure P redistribution, but this study indicates that other processes in the value chain may be more important for environmental impacts

Summary

Introduction

Animal manure is a key component in cycling phosphorus (P) between animals and crops. The P cycle between animals and crops has largely been broken by regional specialization in livestock production or arable farming [2,3]. Soil P accumulation due to high input of manure P is a current challenge in many Western European countries [8], and substantial soil P accumulation in agricultural production systems in general is found both in- and outside of Europe [9]. Specialist arable farming regions have to import mineral P fertilizer to compensate for P exports with crop products and lack of animal manure to maintain soil fertility. In order to reduce consumption of phosphate rock, reduce soil P accumulation and associated risk of P loss, and achieve healthier global P stewardship, more efficient use of P in agriculture is needed [9,11]

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