Simple incinerator cuts spray pack emissions
By John Allan
A NEW approach to pesticide pack disposal may be the last thing on the mind of farmers and sprayer operators struggling to catch up with delayed applications. But public pressure means a rethink is justified.
MAFFs new Green Code for pesticide use on the farm still allows thoroughly rinsed, drained pesticide packs to be burned – provided such burning meets the closely defined conditions of clean air legislation and local approvals.
To help farmers do that the British Agrochemical Association commissioned Silsoe College to find a financially and environmentally sensible method of high temperature on-farm incineration.
The resulting incinerator is a hybrid between a wire mesh garden incinerator and the punctured 210-litre steel drum already used on many farms. It achieves temperatures over 800C (1470F), which break down the organic constituents of plastic into harmless carbon-dioxide and water.
A good air flow is needed to ensure such a fierce fire and this is achieved by placing an expanded metal grid in the barrel 190mm (7.4in) above the ground. Eight 60mm (2.3in) diameter air holes are then equally spaced at 440mm (17in) above the ground, while 11 of 50mm (2in) are situated below grid level at 150mm (5.8in).
The air holes must be the right size. Too much air lowers the incineration temperature, while insufficient air increases the risk of black smoke pollution and prosecution.
Trials at Silsoe College alongside independent tests by the Fire Research Laboratory show plastic falling through the grid burns fiercely in the controlled air flow passing to the burning packs above the grid.
Provided rinsed plastic waste is burned the right way emissions are no worse than from burning an equivalent quantity of pine logs, according to trials at the Fire Research Laboratory.
"Pack disposal in this new-style incinerator is far preferable to burning on the ground, which doesnt allow enough air through the waste and carries a risk of producing black smoke," comments the BAAs Patrick Goldsworthy.
The BAAs new design for on-farm spray pack burners ensures emissions are no worse than from a heap of pine logs.
• BAA supports on-farm burning of empty plastic pesticide packs.
• Packs must be thoroughly rinsed and drained.
• High temperature burn needed.
• Burning on ground not hot enough.
• New farm incinerator design developed at Silsoe.