One of the possibilities to abate the environmental problems caused by pig manure surpluses is separation of the manure into clean water and an organo-mineral fertilizer. An efficient way to realise such a separation is by central processing in large plants. The process in such a plant comprises a large number of logically arranged basic treatment steps. In the Netherlands, practical application of large-scale central processing of pig manure has just been started. Two of these systems are discussed, the Promest system and the Memon system. Based on several studies the investment of a central treatment plant, with a processing capacity of 500,000 tonnes of raw pig manure annually, is estimated at approximately Dfl. 100,000,000. Gross operating costs are estimated at about Dfl. 60 per tonne of raw pig manure. The value of the fertilizer produced per tonne of raw pig manure is estimated at an amount between Dfl. 20 and Dfl. 35. Foreign markets have to be opened for utilisation of this fertilizer in agriculture. To improve such central processing systems, current research focuses on the improvement of existing systems, development of new systems, and production of more valuable products such as lysine.