A direct fired steam weeder
Paper published in Weed Research. Online posting of this paper is prohibited by the publisher. If you would like an eprint please contact me and I will send you one, or if you have access to Weed Research you can download the paper directly from the journal.
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Flame weeders are a valuable weed management tool for organic growers and potentially for non-organic producers if the number of registered herbicides continue to decrease. However, they have a number of problems including low energy efficiency, fire risk and reduced performance in windy conditions. Steam has been shown to be a superior means of heat transfer to weeds, and therefore steam weeders should outperform flame weeders. However, producing sufficient quantities of steam on tractor-mounted equipment has been problematic because the standard designs of pressurised steam boilers are ill-suited for agricultural use. The ‘direct-fired steam’ weeder described here, is considered to resolve this problem, by spraying water as a fine mist directly into hot exhaust gases from a burner, causing it to evaporate quickly, thus negating the needs for a pressurised system. This design is diesel powered but could also be run on renewable fuels such as vegetable oil, addressing concerns about the use of non-renewable ‘fossil fuels’ for thermal weeding. This approach is believed to be both effective in terms of steam generation and sufficiently practical and low enough in inherent risk for agricultural use. Production of commercial steam weeders based on this concept has commenced in New Zealand.
Keywords: thermal weeding, flame, steam, direct-fired, boiler, fire hazard, multiple fuel types.