Relationships among slurry characteristics and gaseous emissions at different types of commercial Spanish pig farms

Amanda Becaccia,Paloma García-Rebollar,Miguel A Ibañez,Salvador Calvet,Fernando Estellés,Pablo Ferrer,Carlos Rodríguez,Carlos De Blas,Verónica Moset

doi:10.5424/sjar/2015131-6575

Abstract

This study aimed to analyse several factors of variation of slurry composition and to establish prediction equations for potential methane (CH4) and ammonia (NH3) emissions. Seventy-nine feed and slurry samples were collected at two seasons (summer and winter) from commercial pig farms sited at two Spanish regions (Centre and Mediterranean). Nursery, growing-fattening, gestating and lactating facilities were sampled. Feed and slurry composition were determined, and potential CH4 and NH3 emissions measured at laboratory. Feed nutrient contents were used as covariates in the analysis. Near infrared reflectance spectroscopy (NIRS) was evaluated as a predicting tool for slurry composition and potential gaseous emissions. A wide variability was found both in feed and slurry composition. Mediterranean farms had a higher pH (p<0.001) and ash (p=0.02) concentration than those located at the Centre of Spain. Also, type of farm affected ether extract content of the slurry (p=0.02), with highest values obtained for the youngest animal facilities. Results suggested a buffer effect of dietary fibre on slurry pH and a direct relationship (p<0.05) with fibre constituents of manure. Dietary protein content did not affect slurry nitrogen content but decreased (p=0.003) total and volatile solids concentration. Prediction models of potential NH3 emissions (R2=0.89) and CH4 yield (R2=0.61) were obtained from slurry composition. Predictions from NIRS showed a high accuracy for most slurry constituents (R2>0.90) and similar accuracy of prediction of potential NH3 and CH4 emissions (R2=0.84 and 0.68, respectively) to models using slurry characteristics, which can be of interest to estimate emissions from commercial farms and establish mitigation strategies or optimize biogas production.

Highlights

In the past, animal manure was regarded as a scarce and valuable source of plant nutrients to maintain soil fertility
The results indicate an important variability among the samples analysed
The coefficients of variation (CV) of chemical components varied from 35-50% to more than 80% in the case of total solids (TS), volatile solids (VS), NDICP and acid detergent lignin (ADL)

Summary

Introduction

Animal manure was regarded as a scarce and valuable source of plant nutrients to maintain soil fertility. At present there is an increasing concern about the impact of high levels of manure fertilization in different parts of the European Union, including some Spanish regions, where pig production is highly concentrated. According to the FAO Corporate Statistical Database (Faostat, 2014), world’s pig population has risen to almost 1 billion heads in 2012, and Spain is the sixth world pig producer. In this context, agriculture still plays an essential role in recycling manure nutrients, and new uses of manure have been developed in recent years (e.g. biogas production). The management of livestock manure contributed to about 19% of total CH4 emission, whereas slurry management in pig production emitted about 5.4% of total EU CH4 emissions (EEA, 2014b)

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Conclusion