Despite its prevalence in routine garden care, Roundup is a strong chemical and should be treated as such. If you have extra Roundup left over from a project, you can’t just dump it down the drain or toss it in a nearby field.
Glyphosate, the active ingredient in Roundup, was previously listed as a potential carcinogen. In 2020, the U.S. Environmental Protection Agency (EPA) updated its stance to say that glyphosate does not pose a health risk when used as directed. Regardless, disposing of this chemical irresponsibly is not only dangerous to the individual but also to the environment at large.
Controversy aside, Roundup is unlikely to disappear from shelves anytime soon. It continues to be one of the best herbicides available. Just be sure to follow the best practices I’ve outlined below for disposal if you opt to use glyphosate in your own lawn and garden.
What Can You Do With Leftover Roundup?
Ideally, you won’t have any leftover Roundup at all. I highly suggest purchasing the smallest product size available for your project. When diluting concentrated glyphosate, mix a little bit at a time to avoid having any left over.
If excess Roundup is unavoidable, the best option is to store it for later. Alternatively, you can safely and carefully dispose of leftover Roundup according to local guidelines.
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How To Dispose Of Roundup
For very small amounts of Roundup that cannot be stored for later use, I recommend finding a safe location to dispose of the excess product outdoors. Good locations include a gravel driveway, rock garden, or anywhere else without desirable plant growth. Dilute the Roundup with water before disposing of it in this way. Do not dump excess Roundup near in-ground drains or natural water sources.
To dispose of any significant amount of leftover Roundup (i.e., >1 cup), I recommend reaching out to your local hazardous waste disposal program. Depending on your municipality, you may have access to a nearby drop-off location or be able to schedule a pick-up service from your home.
Do not place empty Roundup containers in your household garbage or recycling before contacting your local waste management service. They will confirm whether safe disposal is possible and, if so, how to rinse and sort the empty packaging for collection.
Never reuse empty Roundup bottles. No amount of rinsing or cleaning will make this practice safe.
Storing Roundup
Proper storage will ensure your Roundup lasts as long as possible, eliminating the need to dispose of these chemicals in the first place. Roundup can maintain its efficacy for many years when stored correctly.
Always store chemicals in their original containers. Unless the safety label states otherwise, I recommend storing glyphosate-containing products in a cool location away from direct sunlight. Do not store anywhere that can drop below freezing — aim for a minimum temperature of 40°F year-round for the best results.
Unfortunately, Roundup that has been diluted can’t be stored for longer than a few hours. I always suggest mixing small amounts to prevent waste. Dispose of any excess the same way you would non-diluted Roundup.
Since expiration dates aren’t standard for most lawn care products, I always recommend testing stored Roundup before use. Apply the herbicide to a small, pre-chosen area according to the product label. If you do not see the expected results after 24 hours, the glyphosate inside has likely broken down. You will need to safely dispose of this bottle and purchase a new one.
Alternative Ways To Use Up Leftover Roundup
I’m a big believer in reducing, reusing, and recycling whenever possible. However, you need to be very, very careful when disposing of garden chemicals like glyphosate.
No matter how good your intentions are, using leftover Roundup in any way not described on the product label is not recommended. It is better for you and the environment as a whole to safely dispose of unused Roundup.
If you need to get rid of excess Roundup that is still within its viable shelf life, my top suggestion is to reach out to neighbors or local gardeners to see if anyone has a need for the product. This is a great way to minimize waste while still adhering to Roundup’s intended use.
Can You Pour Roundup Down The Drain?
One of the worst things you can do with excess Roundup is to pour it down a household drain. While this is a quick way to remove unwanted Roundup from your possession, it does nothing to actually dispose of the chemicals inside. No amount of dilution will make a difference, either.
Many people mistakenly believe that wastewater treatment centers remove any and all contaminants. According to the EPA, this isn’t true. Most treatment centers are only capable of removing very specific materials from the water and Roundup is not one of them.
There’s also the very important factor that not all drains lead to wastewater treatment centers in the first place. Unused Roundup poured into a street or storm drain is very likely to end up in a natural waterway like a stream or river.
How Long Does It Take For Roundup To Degrade?
Once applied to the soil, Roundup immediately starts to degrade. A peer-reviewed study published in Plants found that glyphosate’s average half-life in soil is between 7 and 60 days. Naturally occurring bacteria are the biggest contributors to glyphosate degradation in the soil.
According to Oregon State University, the measured half-life of glyphosate in dead foliage is 8 to 9 days. Keep this in mind when disposing of plant material previously treated with Roundup.
According to the Wisconsin Department of Natural Resources, the half-life for glyphosate in waterways is between 3 days and 19 weeks. Aquatic conditions — notably, the number of microbes in the water — play a large role in how quickly Roundup breaks down when it enters natural water systems.
Cleaning Spray Tank After Using Roundup
You shouldn’t leave Roundup in a chemical spray tank for longer than it takes to apply it. Even if the tank is used exclusively for glyphosate, excess Roundup can build up inside the tank and clog the attached spray nozzle.
For basic maintenance, I recommend cleaning the tank with warm water immediately after use. Fill the tank halfway and pump the water out through the nozzle. Be sure to spray onto a previously treated area because there will be some Roundup in the mixture.
An ammonia-based solution can be used for a more thorough cleaning. For the best results, follow the directions provided with your chosen cleaning solution.
You may also be interested in reading Does Roundup Go Bad Or Expire
Verdict: How To Dispose of Glyphosate Safely
With any luck, future research will reveal safer alternatives to Roundup that are equally as effective against weeds. In the meantime, however, knowing how to dispose of Roundup is just as important as knowing how to apply it.
Always follow the manufacturer’s directions when mixing and storing glyphosate-containing products. Prepare the minimum amount possible to avoid wasting products that cannot be stored for later use.
You should never place Roundup or its packaging in a standard trash or recycling bin unless approved by your local waste management service. Most areas accept and process hazardous chemicals like glyphosate separately from household garbage.
