Two-stage separation and acidification of pig slurry – Nutrient separation efficiency and agronomical implications

Athanasios Pantelopoulos,Helena Aronsson

doi:10.1016/j.jenvman.2020.111653

Athanasios Pantelopoulos, Helena Aronsson

Open Access

https://doi.org/10.1016/j.jenvman.2020.111653

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Abstract

Separation of slurries can facilitate the nutrient management on farms through nutrient partitioning between the liquid and the solid fraction. The distribution of nutrients in the slurry fractions depends largely on the type of separator used. The current study assessed the separation efficiency of a two-step separation treatment of pig slurry including in-series a screw press and a centrifuge followed by acidification (to pH 5.9) of the final liquid effluent. The system concentrated 73.8% of the slurry's Phosphorus (P) content, 52.6% of Total solids (TS) and 14.4% of total Nitrogen to the solid fraction. The apparent N recovery from ryegrass fertilized with the raw slurry and non-acidified liquid fractions was not decreased by the separation treatment. The acidified liquid fraction showed 28% and 9% higher apparent N recovery compared to the raw slurry and the non-acidified liquid effluent from the centrifuge respectively. The biochemical methane production potential (Bo) of the acidified liquid fraction was reduced by 50% and 25%, compared to the non-acidified counterpart and the raw slurry, respectively. The results highlight the potential of a double separation system coupled with acidification of the liquid fraction, to extract P into a solid fraction which can be transported outside the farm, and to increase N utilization from the liquid fraction when this is used as organic fertiliser on or nearby the farm. The study further highlights the potential to reduce CH4 emissions from slurry storage after mechanical separation and acidification of the liquid slurry fraction.

Highlights

In Europe alone, 1,300 million tons of manure are produced annu ally, and their utilization in agriculture can facilitate the efforts towards reduction of producers’ dependency on mineral fertilizers and sustain soil quality (Scarlat et al, 2018)
The composition of the raw pig slurry (RS) during the sampling period is presented in Table 1, as the mean of ten different sampling events performed from February to June 2018
This represents a typical value of the proportion of inorganic N to total N content in slurries since close to 60% of N excreted by pigs are via urine which is rapidly hydrolyzed to inorganic nitrogen (Sommer et al, 2013)

Summary

Introduction

In Europe alone, 1,300 million tons of manure are produced annu ally, and their utilization in agriculture can facilitate the efforts towards reduction of producers’ dependency on mineral fertilizers and sustain soil quality (Scarlat et al, 2018). Previous reports indicated that poorly managed manures contribute with 50% of the nitrogen (N) and 70% of the phosphorus (P) losses accountable for water quality degradation (Leip et al, 2015). This is important for eutrophicated areas, such as the Baltic Sea region, where nutrient surpluses in agriculture have been identified as the main contributor of non-source pollution leading to the eutrophication of the Baltic Sea (Svanback et al, 2019). The concentration of P and organic matter in the solid fraction, enhances nutrient management in the farm and

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