In the Netherlands, ammonia emissions, considering the emission level of 1980, have to be reduced by 50 % in the year 2000 and by 70% in 2005. Research experiments are testing the promising combination of particular pen design and urine produced at a lower pH value. The replacement of chalk (CaCO3) by a mix of acid salts results in acidified urine and manure produced by the pigs. Ammonia reduction of 37% have been measured in 3 growing-finishing periods from pigs fed with the acid salts diet (ammonia emissions of 1.25 kg per pig- place per year) compared to pigs fed on a regular diet (1.99 kg ammonia per pig-place per year). For the manure produced by the pigs fed the acid salts diet, the manure had a pH value of 5.30 compared to 7.44 for the regular diet. The feed conversion ratio was also improved with the treatment diet from 2.64 compared to 2.72 for the regular diet. The costs associated with the use of acid salts have been evaluated at f 10.20 per pig place per year.

However the ammonia emission difference obtained between acid salts and the conventional diet is not significant. So the reduction of 37% cannot be considered as other factors than the acidic diet could have caused that difference. More repetitions are needed to confirm that the difference is from the different diet. The additional costs of $7.32 CAN (f 10.20) consider the improvement in the feed conversion and the lower feed needed.