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With a government keen on increasing recycling rates, there is an increasing tonnage of compost available but there is also a reluctance by the farming industry to be seen as providing a ready unquestioning home for this material.
“There is compost and compost,” according to Kathy Peebles, livestock development officer with Quality Meat Scotland, who said that while farm assurance schemes had no problem with green waste, which met Publically Available Specifications, there was no way that either animal waste nor waste collected from households would be acceptable.
From the other side of the equation, Peter Goldie, from Dundee City Council Waste Management team, said the growing problem was in disposing the material.
“The problem is getting farmers to take the compost. The site I look after is now generating more than 5,000 tonnes annually. We send it out to allotments but we could do with more farmers taking it.”
Will McManus from Zero Waste Scotland estimated there were now about 3 million tonnes of compost being generated in the UK annually.
This was ten times the figure of a decade ago, and he said the amount of waste being recycled into this type of organic fertiliser was still rising rapidly as local authorities sought to cut the amount of material going into landfills sites.
The local authority site in Dundee is one of about 20 such recycling units throughout Scotland, and McManus estimated that some 60% of the end product went onto agricultural land.
He accepted that there were concerns by some farmers over the potential bringing organisms such as Potato Cyst Nematode onto the farm but said that the maturing process and the requirements laid down in BSI PAS100 were sufficient to remove any problem.
Growers with such concerns should just go for “green waste” compost, which is made mostly from garden material compared with “food waste” where there might be potato peelings.
In fact, he said that some research had shown that the end product contained organisms that could “out compete” any nematodes in the soil so it could actually be used to clean up fields infested with PCN.
“All together, compost is a very safe fertiliser with very few Potential Toxic Elements.”
While it is classified as a fertiliser, McManus said the main benefit came from its ability to improve soil structure. This was because it contained twice as much lignin as farm yard manure.
The improved soil structure brought other benefits such as increasing the water capacity of the soil leaving more moisture available for the plant’s needs.
Although there has not been a great deal of scientific work on the qualities of composting carried out, some experiments had shown that a long term increase in yield of between 5-10% could be achieved.
He advised farmers to consider using it to substitute a percentage of their fertiliser needs. As such it was a very cost effective compound with pure fertiliser costs being far less than for artificial fertiliser. The potash contained in the compost was more available to plants than artificial fertiliser.
With prices for artificial fertiliser once again back on the increase, compost was a good buy, he reckoned.