The ManureEcoMine pilot installation: advanced integration of technologies for the management of organics and nutrients in livestock waste.

Manure represents an exquisite mining opportunity for nutrient recovery (nitrogen and phosphorus), and for their reuse as renewable fertilisers. The ManureEcoMine proposes an integrated approach of technologies, operated in a pilot-scale installation treating swine manure (83.7%) and Ecofrit® (16.3%), a mix of vegetable residues. Thermophilic anaerobic digestion was performed for 150 days, the final organic loading rate was 4.6 kgCOD m-3 d-1, with a biogas production rate of 1.4 Nm3 m-3 d-1. The digester was coupled to an ammonia side-stream stripping column and a scrubbing unit for free ammonia inhibition reduction in the digester, and nitrogen recovery as ammonium sulphate. The stripped digestate was recirculated daily in the digester for 15 days (68% of the digester volume), increasing the gas production rate by 27%. Following a decanter centrifuge, the digestate liquid fraction was treated with an ultrafiltration membrane. The filtrate was fed into a struvite reactor, with a phosphorus recovery efficiency of 83% (as orthophosphate). Acidification of digestate could increment the soluble orthophosphate concentration up to four times, enhancing phosphorus enrichment in the liquid fraction and its recovery via struvite. A synergistic combination of manure processing steps was demonstrated to be technologically feasible to upgrade livestock waste into refined, concentrated fertilisers.

Waste lipids to energy: how to optimize methane production from long-chain fatty acids (LCFA).

The position of high-rate anaerobic technology (HR-AnWT) in the wastewater treatment and bioenergy market can be enhanced if the range of suitable substrates is expanded. Analyzing existing technologies, applications and problems, it is clear that, until now, wastewaters with high lipids content are not effectively treated by HR-AnWT. Nevertheless, waste lipids are ideal potential substrates for biogas production, since theoretically more methane can be produced, when compared with proteins or carbohydrates. In this minireview, the classical problems of lipids methanization in anaerobic processes are discussed and new concepts to enhance lipids degradation are presented. Reactors operation, feeding strategies and prospects of technological developments for wastewater treatment are discussed. Long-chain fatty acids (LCFA) degradation is accomplished by syntrophic communities of anaerobic bacteria and methanogenic archaea. For optimal performance these syntrophic communities need to be clustered in compact aggregates, which is often difficult to achieve with wastewaters that contain fats and lipids. Driving the methane production from lipids/LCFA at industrial scale without risk of overloading and inhibition is still a challenge that has the potential for filling a gap in the existing processes and technologies for biological methane production associated to waste and wastewater treatment.