Herbicides: Emissions
Why coal-fired phosphorus makes weedkillers carbon heavy
What this tab covers The greenhouse-gas footprint per tonne, split by lifecycle phase (feedstock, production, movement, use, end of life), the global total, other environmental impacts, levers and low-carbon routes, India's position, and where the investment opportunity lies. Emission intensity 20.7 kg CO2e per kg a.i. range about 10-30 depending on molecule and energy source (indicative) · 19.57 kg fossil CO2, 0.037 kg CH4 and 0.00036 kg N2O per kg a.i., converted with AR5 GWPs (CH4 28, N2O 265) Global emissions per year 40.0 Mt CO2e per year 2022 · about 1.9 Mt a.i. x 20.7 kg CO2e/kg (indicative)Per kg of herbicide active ingredient, cradle-to-gate. Intensity: Field to Market impact factors, based on Audsley et al. (2009) and Green (1987). Global total: derived from FAOSTAT use (indicative) and Field to Market factor.
Share of footprint by lifecycle phase
Feedstock 40% Production / process 54% Movement 6%Footprint by lifecycle phase
| Phase | Intensity | Share | Main sources of emissions | Notes | Source |
|---|---|---|---|---|---|
| Feedstock | about 8 kg CO2e per kg a.i. (indicative) | 40% | yellow phosphorus (electric furnaces on coal-heavy grids), chlorine, ammonia, methanol | glyphosate's phosphorus is the biggest single feedstock burden | indicative split |
| Production / process | about 11 kg CO2e per kg a.i. (indicative) | 54% | multistep batch synthesis, solvent recovery, coal steam and effluent evaporation | Chinese and Indian plants mostly use coal steam (indicative) | indicative split |
| Movement | about 1 kg CO2e per kg a.i. (indicative) | 6% | container shipping and road distribution, including water in formulations | indicative | |
| Use | outside cradle-to-gate; tractor diesel for spraying about 1-2 l/ha per pass (indicative) | – | application passes | Herbicides enable no-till, which saves fuel and may keep soil carbon; the net effect is debated | indicative |
| End of life | small | – | degradation in soil; plastic containers | glyphosate breaks down to AMPA; atrazine persists in groundwater | indicative |
Other environmental impacts
Toxicity to non-target plants and aquatic life, groundwater contamination (atrazine, metolachlor metabolites), drift damage (dicamba), human poisoning (paraquat), and herbicide-resistant weeds. Glyphosate wastewater in China is salty and phosphorus-rich.
Levers to cut emissions
- Precision spot spraying with cameras; John Deere reported about 59% average herbicide savings with See & Spray in 2024 (indicative)
- Low-carbon power for yellow phosphorus furnaces
- Single-isomer products such as L-glufosinate that halve the dose
- Integrated weed management: rotation, cover crops, harvest weed seed control
India
Indian technical plants in Gujarat and Maharashtra run largely on coal steam and grid power; companies such as UPL and PI Industries publish group Scope 1 and 2 targets in BRSR reports (indicative).
Emission figures are indicative global averages from the life-cycle studies named; actual footprints vary widely by site, energy mix and method.Low-carbon routes
| Route | Intensity | Cost premium | Status | Source |
|---|---|---|---|---|
| Precision and robotic weeding (camera spot-spray, laser weeding) | cuts herbicide use per hectare by half or more in trials (indicative) | high machine cost; pays back on large farms | commercial in the US, Brazil and Australia (Deere, Bilberry, Greeneye, Carbon Robotics) | indicative |
| Bioherbicides | not published | high | very small share; few products work at field scale | indicative |