Steam Weeding

Basics

• Conventional Industrial Agriculture relies heavily on Pesticides that, while effective at controlling weeds, have a variety of drawbacks.
  • Short Term (Killing Beneficial Insects / A Similar Concept to Bycatch for things like Rodenticides etc) and Long Term ( Bio-Accumulation with past ones such as DDT etc)
  • Long Term Human Health Risks for Workers
    • The exposure for those consuming food produced in an area using pesticides/herbicides is minimal, and even then simple Fruit Washing / Vegetable Washing fixes that as well etc
    • HOWEVER if you are walking in a field with a Pesticide Sprayer or Fogger , and ESPECIALLY if you don't wear PPE your Accumulated Exposure will be insanely high, hence the Leukemia/Lymphoma rates, and recent lawsuits in the USA about WD-40 / Roundup (Herbicide) etc
  • High Cost
    • Even if the latter are handled with Pollution Control Measures for Agricultural Runoff / Soil Contamination / Measures for limiting Honeybee Deaths Attributable to Pesticide Use
    • Furthermore, from an Appropriate Materials standpoint, short of Nicotine Solution Pesticides / other Bio-Pesticides , most are incredibly complex to make and/or require intermediates like Phosphoric Acid or even Phosgene (that's right, the thing used as a chemical weapon ) so is probably a no-go
• Thus an alternate method is needed for Organic Agriculture , as well as Integrated Pest Management
• Traditionally, organic agriculture has relied on Tillage or Cover Cropping for weed control.
• While these methods avoid the use herbicides, they have their downsides.
  • Tillage can damage soil life and structure, resulting in a loss of valuable nutrients and Soil Organic Matter.

Cover crops may compete with cash crops for nutrients and water, although this depends; Bait Plants and Co-Cropping can be beneficial (Re: Kionhekwa )

• Flame Weeding have been used with success, but often rely on propane gas from fossil sources.
  • Also Flame Weeding cannot be used in areas with a high Wildfire Risk and the Rows cannot have Companion Planting etc, but rather Mulch or worse yet Bare Topsoil
• Steam Weeding has none of these limitations, and short of potentially messing up Soil Bacteria in treated zones is easy to accomplish, can be either highly selective with a Steam Wand and small nozzle, or even be scaled up to a Boom Arm sized unit. Pesticide Resistance is also not an issue
• Short of Water Availability (and to a lesser extent Fuel Availability / Electricity Cost it is also a cheap method

OSE Design

• Essentially a Pyrolysis / Gasification - powered steam weeder, which puts out superheated steam to kill weeds.
• This device can use all kinds of dry biomass for fuel. Pelletized biomass such as wood pellets should work well.
• The saturated steam from boiling water runs through a copper coil which is externally heated in the pyrolysis unit, creating the superheated steam. (Re: Flash Boiler
• Charcoal / Biochar is generated as a byproduct with Non-Char Burning Gasifier Designs, making the process carbon-negative.
  • Pyrolysis Oil could be collected in theory, but short of if done in a Sawdust Gas Filter / Charcoal Gas Filter / Activated Carbon Adsorber this would add a rather significant amount of Design Complexity
• A Pressurized Water Boiler could also be used, although this introduces the risk of a Boiler Explosion and the required risk management ( Boilermaker level Weld Quality Control etc) where pressure is not the main goal (Such as a boiler for a Steam Engine ), but rather Temperature and Volume

Components

• A Biomass Gasifier / Pyrolysis Kiln to work as the heat generation core
  • Looking into using a CHP Powercube would be especially interesting for Lifetrac mounted steamweeders
• A Flash Steam Generator
  • (Most Likely Copper ) Coiled Piping / other Heat Exchanger design pending further analysis (most likely of a Water Tube Boiler Configuration
• A small Electric Blower Fan for Forced Air to the TLUD (either could be required, or just be for startup / heat output boosting)
• An Arduino that controls:
  • The fan
  • The Boiler Feedwater System
  • The Steam Regulator
  • IO and Safety Systems (Although Redundant Controls akin to Safety Instrumented Systems may be a good idea)

Media

Large TLUD gasifier, built by Rob Diermair, Biochar Ontario.

Uses

• (Organic) Weeding
• Invasive Species Control
• As a Steam Generator for applications in need of High Volume High Temperature Steam / Working Fluids Such As:
  • Torrefaction / Pyrolysis / Gasification / Thermal Oxidation etc
  • Gas Stripping (Mainly an Open Source Chemical Stripping Column for Bio-Refinery Operations )
  • Soil Sterilization / Biomass Sterilization etc, albeit not to the pressure of an Autoclave

Internal Links

• Open Source Flash Steam Weeder
• Flame Weeding

External Links

• [*The Wikipedia Page on Thermal Weeding
• Soil Steaming Blog
• paper: A direct-fired steam weeder
• "food drying with superheated steam"
• Wikipedia: Soil Steam Sterilization
• Flame vs. Steam
• Green Steam