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Q: We have been asked the following question twice during the first month of this web site:-
I see that you make a critical comment, "Some of the first generation examples of “irrigation treatment” in the UK were scientifically and/or environmentally unsound...."
A: Steve Last answers; I have been working in UK leachate treatment for 20 years. When I started there were many leachate irrigation systems which had been set up by landfill operators which were not scientifically designed at all. For example until the late 1980s, strong leachate was being sprayed on the grassed surface of old landfills, the grass was in a very poor often yellow condition and badly iron stained. During rainfall, contamination was washed into streams and watercourses. It was a cheap way to get rid of leachate, and in my view the operators made claims for the degree of treatment achieved, which when we took our own samples, were found wanting.
Over the years we have been proved right. Our Environment Agency has been given greater powers to intervene, and has closed many of the grass irrigation plots, uncontrolled woodland spraying schemes, etc.
We have now designed, and been involved in the building of, more than 60 biological leachate treatment plant schemes throughout the UK, which treat to high standards and fully comply with the EA discharge consents applied. Many were replacements for old irrigation systems (see www.leachate.co.uk ).
At many of our plants we have built polishing stage reed beds, and these have been very successful.
However, the poor reputation of the early types of treatment schemes that we call "landfill-irrigation" caused by the early use of very basic systems which were not scientifically designed, has lived on.
We would like to redress this by our work, because we think that although many leachates are very strong and highly technological solutions may be essential at some sites, many other sites have much more dilute leachates and are good sites for phytoremediation (plant irrigation) based treatment.
There is a danger that the Regulator will increasingly see the way forward very much more in terms as "high technology fits all solutions", and we don't think it does.
Landfills vary so much that a very wide ranging set of tools is needed if we are to provide the most appropriate sustainable solutions to all.
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Q: Which are the chemicals in landfill leachate which are of benefit to crop growth?
A: Landfill leachate contains several constituents which are required by plants to generate biomass, these are:-
- water
- macronutrients: nitrogen, potassium, calcium, magnesium and sulphur, and,
- micronutrients: (such as boron, iron, copper, chloride and zinc).
Q: Are these the only advantages?
A: No. Leachate application to plants can be used as a substitute for the water used normally in agriculture, and the inorganic fertiliser applications which would otherwise be needed.
This reduces the considerable demand for natural resources required to manufacture fertilisers and provide irrigation water. It also offers a method to reclaim these constituents, avoiding their direct disposal into watercourses or, following treatment, as solid residues back to landfill.
Bioenergy crops, which include SRC and certain fast growing grass species such as Phalaris and Miscanthus offer an advantage over food of fodder crops by avoiding any real or perceived risk of contamination of the food chain by leachate irrigation.
In addition, the UK government is committed under the Kyoto agreement to produce 10% of its power generation from renewable sources and the production of bioenergy and bioenergy feedstocks are therefore subject to various financial incentives
Q: Won’t the burning of biofuel crops cause more carbon dioxide emissions?
A: No. The carbon dioxide released into the atmosphere from the burning of crops is carbon (C) neutral. The carbon released into the atmosphere during combustion of the crop is only the same carbon that was removed from the atmosphere when the crop grew.
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