In the Netherlands the high densities of farm livestock pose a number of problems, particularly with regard to waste disposal. Nitrogen compounds leaching out of animal waste form one of the most serious environmental contaminants. Modified housing systems, such as the use of plastic netting floors for broilers (which speeds up dehydration), often can largely eliminate the release of ammonium gas which gives rise to air pollution. However, this only defers the problem because subsequent application of the droppings to the land, where they become rehydrated, results in the rapid production of ammonia and nitrates through microbial activity. Research at Delft University identified bacteria capable of converting the nitrogen in ammonia to molecular nitrogen gas under aerobic conditions. Subsequent development work at the Spelderholt Institute has established a considerable potential for application. The addition of cultures of the bacteria to the feed is a promising future technology.