H2020 Project DEPURGAN: Pig Farm Revolution

Already identified as a serious environmental problem in several regions of Europe, China, Russia, and the United States, pig manure management has become a social and environmental issue that urgently requires a definitive solution in the pig sector. Two main factors have contributed to this situation in recent decades: i) the number of confined animals has increased on larger farms, resulting in more manure production than the available land where pigs are raised can assimilate; and ii) stricter European and national directives have limited the disposal of manure as fertilizer, which used to be the traditional solution in the past, due to soil nitrification.

Consequently, pig farm owners must pay waste treatment companies to manage their slurry (€3-3.5/m³, with transport costs accounting for up to 60% of the total) or, alternatively, larger farms invest in their own treatment equipment to comply with these regulations.

Over the past few decades, the negative environmental impacts of livestock production and manure management have been controlled through stricter regulations for manure storage and distribution. However, the intensification of livestock production has led to larger herds on fewer farms and industrial-scale operations producing large quantities of manure in centralized locations. As intensive livestock farming is under increasing pressure to minimize the environmental impact of its operations, several processes have been evaluated as Best Available Technologies (BAT) for manure treatment, while simultaneously improving the utilization of nutrient resources. However, most state-of-the-art (SAT) solutions are currently neither technologically nor economically viable, and more importantly, they are often subject to national subsidies to be profitable. EUROGAN is based in Spain (one of the world's largest pork producers and exporters) and has been operating in the livestock sector since 1964. Driven by real customer demand and with the aim of exploiting the potential of the slurry business, our company has recently patented an innovative slurry treatment process that: 1. Minimizes the concentration of contaminants in slurry (nitrogen, phosphorus, metals, bacteria, viruses, etc.); 2. Treats slurry at its source; 3. Is technically and economically viable for farmers, as it is not subject to national subsidies; 4. Maximizes slurry recovery (energy recovery and fertilizers).

The DEPURGAN project seeks to commercialize an efficient pig slurry treatment process, with an initial investment four times lower than other solutions and highly competitive operating costs. Its innovation is based on the use of an optimized electrocoagulation reactor that allows for nitrogen reduction, while producing a solid fraction of waste with high calorific potential as biomass, and a liquid NPK effluent ready for use as fertilizer.

DEPURGAN will have a treatment capacity of 20 m³/h and includes a combination of: i) solid/liquid separation using a centrifuge, ii) high-efficiency electrocoagulation, iii) final fertilizer synthesis, and biomass pelleting. The system will be introduced into the pig sector as a comprehensive solution that will treat slurry at its source, reduce contaminants in the liquid fraction, providing an odorless and colorless liquid phase, and its economic viability will be independent of national subsidies.

Electrocoagulation is similar to a physicochemical treatment, but uses electrical energy flowing through the medium instead of other mechanical or chemical agents, which is why it has been defined as an electrochemical process. The increase in pH at the cathode promotes the formation of insoluble hydroxides (Al(OH)3, Fe(OH)3) that precipitate, trapping solid particles and organic material that form flocs, which are continuously extracted from the system. In parallel, different physicochemical processes take place inside the reactor that eliminate contaminants: ionization, precipitation, emulsion breaking, electrolysis, free radical formation, compound breaking, and emulsion separation. The electrical discharge, together with strong oxidative radicals, as well as a high pH, produce a biocidal effect that also destroys pathogens in the electrolytic cell.

The system's results could be commercialized: The liquid fraction can be used for fertigation. The separated solid fraction, which accounts for approximately 5-10% of the total pig slurry treated, can be converted into dry pelleted biomass for use in central heating system installations or as a marketable product.