La cantidad de residuos orgánicos producidos por animales de granja implica graves problemas de contaminación por un lado, y de pérdidas económicas para las granjas de producción de ganado por otro. Para el caso de los cerdos, Dimitri Muraviev, junto con otros investigadores, propone un nuevo sistema de tratamiento intergal de los residuos producidos en las granjas.

Artículo: Pawelczyk, A, Muraviev, D. The integrated treatment for purification of liquid pig wastes. PRZEMYSL CHEMICZNY. (2003), Vol 82, Is 8-9.

Livestock agriculture in Europe has developed into an efficient industry over the latter half of the twentieth century. Most livestock-associated organic by-products or "wastes" are animal manures. At present the annual production of pig manure in, for example, Germany, Spain, UK and The Netherlands is estimated to be around 50, 45, 9.25 and 16.1 million tones. The projection of livestock numbers up to the year 2010 for the EU-15 shows that, although the total number of pigs in EU countries (without Eastern Europe) will decline from 120.3 million in 1990 to 115.6 million in 2010, a substantial increase of pigs population is expected in Spain (from 16 to 21.4 millions), France (from 12.4 to 17.4 millions) and some other countries. At present some regions exhibit increasing environmental problems including air and water pollution.

For example, in NW France a small area (only 7% of the agricultural land of the country) is responsible for nearly 60% of French pig production and more than 20% of dairy production. In NE Spain 2000 pig farms are located in the area with the radius of 50 km. Similar situation is observed in Eastern Europe, where the majority of pigs are concentrated at either huge complexes or farm clusters.

Quantitative estimates of both environmental impacts and economical potential of by-products ("wastes") associated with industrial pig production show that 115.6 million pigs excrete 208 million tons of manure and release in the air over 800,000 tons of ammonia nitrogen per year. This account for approximately 20% of the total ammonia imported by Western European countries in 1998. The synthesis of this amount of ammonia requires consumption of approximately 32 million Giga-joules of energy. An average phosphorus (P) and nitrogen (N) content in the pig manure is 1.4 and 2.6 kg/ton, respectively. This means that the above number of pigs will excrete 290,000 tons of P and 540,000 tons of N per year. Comparison of the first figure with amount of phosphoric acid produced in Western Europe in 1998 (recalculated to P content) shows that it accounts for more than 40%. The potential biogas productivity of anaerobically-treated 208 million tons of manure is around 3 billion cubic meters of renewable gas fuel (equivalent to 1.8 million ton of petroleum). Even partial recovery and utilizations of valuable components of animal wastes will substantially improve the economical efficiency of the treatment technology.

The proposed approach is based on Integrated Treatment Technology (see Figure) , which includes 1) air treatment, 2) liquid treatment, and 3) solid treatment stages interconnected with each other. The air treatment stage is to substantially decrease uncontrolled disposal of contaminated indoor air of animal farms and emissions from manure storage and composting facilities by using a system of dust, ammonia (ion exchange) and VOC - H2S selective (compost) filters. The regeneration of ion-exchange filter (IEF) produces sufficiently concentrated aqueous ammonia solution (which will be also used to absorb air-stripped ammonia) to be utilized as a liquid fertilizer. The liquid waste treatment stages include improved manure flushing system, anaerobic reactor, air stripper, phosphates crystalliser, and aerobic/anoxic biofilter or aerobic/anoxic reactor. They are characterized by high efficiency of removal of undesired and recovery of valuable constituents of the slurry to produce decontaminated recyclable water, biogas and inorganic fertilisers. These stages representing the main part of ITT operate along with air treatment stages (IEF) in either continuous or semi-continuous mode. The gas flux from air stripper containing ammonia is used to fortify aqueous ammonia solution obtained after regeneration of IEF. The solids separated after anaerobic and aerobic treatment steps are directed to the compost production.

SCHEMATIC FLOWSHEET OF AIR & MANURE ITT SYSTEM






Dmitri Muraviev
Departamento de Química
Universitat Autònoma de Barcelona