The fate of Cu and Zn along the feed-animal-excreta-effluent continuum in swine systems according to feed and effluent treatment strategies.

Copper (Cu) and zinc (Zn) have negative environmental impacts as they accumulate in the soil after pig manure is spread. Cu and Zn are essential elements in pig nutrition but due to their low retention rate, more than 90% of ingested Cu and Zn are excreted. A better understanding of the behaviour of these elements throughout the animal-manure-soil continuum according to feed composition and manure management chain is thus required to propose alternative ways to reduce these environmental impacts. The aim of this study was to determine the fate of Cu and Zn throughout this continuum by studying the effect of Cu and Zn contents in animal feed and in the manure management chain based on anaerobic digestion and composting. Faeces were collected from 24 finishing pigs fed with 4 different Cu and Zn dietary levels and sources of supplementation. Samples of faeces were exposed to mesophilic anaerobic digestion or to 5-week composting with straw. Concentrations of Cu and Zn in the faeces were highly dependent on dietary supplies and ranged from 38 to 188 mg Cu/kg DM and from 191 to 728 mg Zn/kg DM. Degradation of a significant fraction of organic matter during treatment led to a significant increase in Cu and Zn concentration relative to the product's dry matter (DM) content, which. Cu and Zn concentrations relative to DM content were twice as high after treatment whatever the content and the form of Cu and Zn dietary supplementation. Otherwise, effluent treatment tended to reduce the possible availability of Cu and Zn in final organic products according to water-extractible contents. This study clearly shows that feed management is the main lever for reducing the amount of Cu and Zn amount in pig effluents and hence in the soil. Appropriate treatment could also facilitate the supply of organic fertilisers to areas with soil deficiency, but feed strategies need to be adapted to the treatment chain to enable the production of good quality organic products that respect EU regulations.

Determination of the lipid content of organic waste using time-domain nuclear magnetic resonance.

Time-Domain Nuclear Magnetic Resonance (TD-NMR) was used to quantify the lipid contents of 48 different organic waste substrates. Results obtained from TD-NMR were compared to those from Soxhlet extraction, currently the prevalent method for organic waste characterization, especially in the field of anaerobic digestion. Two calibration methods were tested. The first was a self-calibration process using pure oils (NMR1) which showed good repeatability compared to Soxhlet extraction with a better coefficient of variation (5%). Analyses of volatile fatty acids (VFA) and long-chain fatty acids (LCFA) by chromatography were carried out to understand why the NMR1 method produced underestimations for some samples. Statistical analysis showed that the presence of saturated fatty acids had a significant effect on differences between the Soxhlet and NMR1 methods. The second calibration method applied chemometrics to TD-NMR raw data (NMR2), taking Soxhlet extraction values as references. It provided a good prediction of lipid content and avoided the lengthy calibration procedure usually required for this type of study. Last, the NMR2 method was shown to be highly suited to the quantification of lipids in organic waste, demonstrating better repeatability than the classic Soxhlet method.

The efficiency of biological aerobic treatment of piggery wastewater to control nitrogen, phosphorus, pathogen and gas emissions.

Due to the water pollution and in order to reduce the nitrogen load applied on soils, biological nitrogen removal treatment of piggery wastewaters was developed in Brittany (France), with 250-300 units running. Four types of treatment processes were built including a biological reactor allowing to remove about 60-70% of the nitrogen content as gas by nitrification/denitrification. The addition of different mechanical separators (screw-press, centrifuge decanter ...) led to concentration of phosphorus in an exportable solid phase, allowing a reduction up to 80% of the phosphorus applied locally on soils. Moreover, a reduction of the gaseous emissions was observed using this management process as compared to conventional management (storage + land spreading) including ammonia (up to 68%) and greenhouse gases (55%). Finally, the level of enteric and pathogenic bacteria was also decreased with the treatment process as compared to conventional management systems. However, in spite of these results, the significant cost of the treatment must be underlined and alternative systems including anaerobic digestion will have to be studied.