Composition,Use and Legislation of Spent Mushroom Substrate in the Netherlands

? In The Netherlands, 760,000 metric tons of Spent Mushroom Substrate (sold under the name Champost) were produced in 1993. The annual production is still rising. Analytical data concerning fertilizer elements like N, P, K, Ca and Mg, show that the composition of SMS has been fairly constant since the mid sixties. However, the last few years, dry matter, ash and phosphate content are decreasing due to reduced composting time and cropping cycle. Heavy metals and arsenic were not analyzed until 1983. In connection with manure surpluses in The Netherlands, a ‘Decree Use of Animal Manure’ was laid down as part of the Soil Protection Act, which dates from 1986. The Decree regulates the maximum quantity of manure that may be used, based on its phosphate content. The rules will be accentuated in the next few years. Since 1993, SMS falls under another item of the Soil Protection Act, the ‘Decree Use and Quality of Other Organic Fertilizers,’ controlling sewage sludge and all kinds of composts. The quantity that may be used depends on phosphate and heavy metal content. The total load of heavy metals, supplied per hectare, is controlled by limiting the amount of dry matter. Each year, 6 metric tons of dry matter may be used per hectare, provided that the compost is ‘clean’. To check phosphate and heavy metals, samples have to be analyzed regularly. In 1993, 620 samples have been analyzed. All compost fell within the category ‘clean’ and 17% was even characterized as ‘very clean.’ Production of vegetable, fruit and garden waste, a type of compost very competitive to SMS, is strongly increasing. Alternative ways of disposal of SMS will be discussed briefly.