29 June 2006

This "pioneering project in Spain" is promoted by the Ecoenergía Navarra group

The plant built by the Ecoenergía Navarra group in Artajona will process about 70,000 cubic metres of pig slurry. After a little over a year in operation, the plant was officially inaugurated yesterday, after this "pioneering project in Spain" was duly consolidated. After an innovative treatment, the plant uses pig slurry to produce dry fertiliser, energy, clean distilled water and, with the excess heat from the co-generation process (slurry treatment) grows tomatoes hydroponically (without soil) in a greenhouse. Over 12 million euros have been invested in this project which is supported by Sodena (with a 45% stake).

The goal of the new plant, located on an estate 2 km from Artajona, is to provide a solution for the treatment of slurries (a mixture of excrements and urine, in this case from pigs) which pose a major waste management problem for farms.

The slurry treatment process is based on a co-generation system that separates the water and volatiles (gases) from the other components of the slurry without destroying its valuable qualities as fertiliser. The process consist of seven stages.

The plant employs the latest technology with very powerful, 15-megawatt engines, similar to the ones used in ocean liners. The plant works year-round, stopping only for scheduled maintenance. It is expected to work 8,100 hours a year and, in addition to meeting the process’ energy needs, it will contribute 15 MWh of electricity to the Iberdrola electricity grid. Electricity generation is carried out by internal combustion engines using natural gas as fuel.

In addition to processing 70,000 cubic metres of slurry annually, this year the plant will also produce 300 tonnes of innocuous organic fertiliser and 250 tonnes of tomatoes (in a 49,000 square metre greenhouse); furthermore, it will generate over 120 million kilowatts of electric energy.

The company

Ecoenergía Navarra began operations in the second half of 2004 with the goal of processing the slurry from the Granja Villanueva in Artajona. The facilities were built by GHESA, which is also a shareholder.

The company group is formed by Sodena (main partner), Ecoenergía Navarra  and Ecoenergía Sistemas Alternativos, a company created to generate technological development in waste management and organic by-products and the use of residual heat. It owns the patent of the slurry treatment system used.

The presentation of the company was made by Sodena’s general manager, José María Aracama Yoldi; the chairman of Ecoenergía, Fernando González Gálvez; the ministers of Industry and Agriculture of the Government of Navarre, José Javier Armendáriz and Javier Echarte; the manager of Ecoenergía, Conrado Astráin; and the CEO of Ecoenergía, Carlos Amat. Amat pointed out that they are “ready to replicate this project in other areas of Spain.” Fernando González underscored the “three key components of this cooperation: a commitment to the environment, a commitment to renewable energies and a commitment to producing fertilisers in an agricultural area such as Artajona.”

Step by step

1. Arrival of slurry. The raw material from the farm is unloaded into tanks. From there, it is pumped to the separating and crushing facility.

2. Separation and crushing. The slurry is processed through a separator-compactor that separates the liquid from the solid matter. The solid phase obtained (75% moisture) is stored in a silo. The liquid phase (with a 3.5% content of solid matter) is sent to the evaporating plant.

3. Distillation and concentration. The water and volatiles (especially ammonia) in the liquid phase are separated. Before being put into the evaporator, the temperature of the slurry is raised to 100 °C. The slurry then goes to the first evaporator, where the first concentration takes place and then decanted into the second evaporator, and so on. This operation yields two phases: a concentrate with 80% moisture and a gaseous phase consisting of water and ammonia. The concentrate is transferred to the storage silo where it is mixed with the solid phase which is then sent to the dryer. The gas is piped to the next evaporation unit. The excess heat from the whole process is used to heat the greenhouse (tomato growing).

4. Chemical treatment. This process fixes the ammonia in the vapour produced in the first evaporator. The condensate is taken to a tank where sulphuric acid is added. The ensuing neutralising reaction produces a solution of ammonium sulphate and water. This way, the emission of ammonia into the air is avoided. The gas treatment produces electricity (15 MWh).

5. Bi-distillation and concentration. The ammonium sulphate solution obtained during the previous stage is taken to a second evaporator where it is concentrated. This produces clean, ammonia-free water and concentrated ammonium sulphate. The concentrate undergoes a drying process, while the clean water is recovered in air condensers to be used in the cogeneration cooling towers (distilled water).

6. Homogenising system. The concentrate from the first evaporator is stored in a silo together with the solids from the separator. A transport system that also works as a homogeniser takes these to the dryer.

7. Drying. The product from the storage silo is taken to a band dryer, where the product’s moisture level is reduced until a good quality organic fertiliser is obtained.