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I live in a major metropolitan area in the United States, and we have a municipal recycling pick-up program. They advise us to wash food containers prior to putting them in our bins, and if an item takes "too much water" to wash, that it's better to throw it away instead. What are the differences in the ecological impact between using more water to wash-out a difficult-to-clean item (e.g. a plastic peanut butter jar) vs. throwing it away? My gut feeling was that it would objectively be better to use more water to wash an item so that it could (possibly) be recycled than it would be to conserve water and have it (ultimately) end up in a landfill, but I don't have any background to evaluate one way or the other.

Edit: I changed the title of the question in response to some answers and comments. It used to be "Is it more sustainable to save water or to recycle", which hid the assumption that I would use potable water, and which wasn't clear that I was asking about recycling waste (not water).

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    My take on this is that it's more sustainable to reduce. Use glass mason jars to get peanut butter at a co-op or bulk food store, and reuse the jar over and over again. Then you're not buying a new jar every time you want peanut butter. – lemontwist Feb 2 '13 at 13:20
  • The city you live in matters a lot here. If your cities water supply is mainly rainwater then wash all you want, but if it's aquifer then don't (and probably move elsewhere if you can, Americas aquifers are drying up at an alarming rate and you don't want to be caught out). – Turksarama Aug 24 at 23:00
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Do you know the rationale behind washing the containers? There's a large-scale system for, among others, plastic containers in place in Germany, and here you are explicitly advised not to wash the containers.

My gut reply would be to not wash the containers. This is based on the assumption that they will either be recycled, and no recycling plant can rely on you washing your peanut butter jars sufficiently for their purposes, and they can probably wash them more efficiently at their plant.

Or the plastic waste is incinerated (in this case the separate collection may be because plastic waste is high value fuel) and then it really doesn't matter.

A lot really depends on what actually happens with the plastics. Note that recycling can mean almost anything except landfill in the terms of the relevant laws: thermal recycling = incineration, material recycling = smelting and reuse.

While I see no sustainability argument for washing, there's a health aspect - containers with food remains can attract pests, stink, or be a reservoir for pathogens. Depending on where you live and how you store the packaging, this may be an issue (thx @WhirlWind for pointing this out!).

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    My knowledge of current recycling scenarios in the US is relatively abridged but I believe it used to be the case that lots would be inspected, unwashed, and too dirty lots would be discarded. I agree that washing done at home is the entire issue, and we'd do better to have it centrally done. Whether or not that's the case may depend on the recycling program. – Chris Travers Feb 6 '13 at 0:51
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    I have seen recycling fora mention rinsing containers is better because it keeps pests and odors away, while they are stored at home before disposing them. I find it's applicable to me, a small town ( in India),where there are no daily collection mechanisms. I have to store for months before I can find a way to responsibly dispose or make crafts to reuse them. Even otherwise, some advise it's better to collect similar waste of a bigger quantity, that means home storage. But, I have also wondered while rinsing whether the water is costlier, so I (should) use minimal water for a quick rinse. – Whirl Mind Sep 18 '17 at 7:13
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I guess the question presupposes a problem, namely that we are going to use potable water to wash plastic containers to be recycled. This is, IMO, a major problem with assuming that people should wash containers prior to recycling. There's really no reason that these need to be washed in ways that reduce our availability of potable water.

My sense is the same as yours but for a different reason. My feeling is that if we get to a point where potable water such an issue one can recycle water for the purpose of washing such containers (maybe using something like runoff from the washing machine). As they say, premature optimization is the root of all evil. I wouldn't worry about it. Short-run it's not a problem. Long-run it's not a problem without solutions.

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    In Germany I know that the city is quite happy for you to use potable water for dishing, even more than necessary. The water gets "recycled" in the treatment plant anyway, but the German people have become so efficient at saving water that the sewage pipes get clogged and the city has to do what the people don't: flush the pipes with great amounts of (potable) water. In a city like that, more important than using too much water is polluting that water with chemicals, which are harder or impossible to treat. That is to say, don't try to wash and recycle paint buckets... – Earthliŋ Feb 6 '13 at 8:40
  • Thanks for pointing out the presupposition that I would use potable water -- I changed the title to reflect the day-to-day dilemma. I'll start thinking about what we could do to use non-potable water in these cases. – Caleb Bell Feb 7 '13 at 22:32
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I have run into the same quandary. I resolved it by keeping a large bin in my sink that catches "grey water" or water already used for washing dishes and add a drop of biodegradable phosphate-free soap and lather it up and dunk it in the grey water as my pre-recycling rinse. Keeping a bin inside my sink and salvaging grey water really cuts down my water use. Soap will carry away any gunk from the dirty water. Sometimes I do a final rinse with one shot of potable water if the soap is too dense to rinse off in greywater bin. I hope that helps other people with this dilemma.

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This is not a problem if you use a basin to wash dishes. As I soap dishes it goes in an empty basin in one half the sink. I rinse the dishes in the basin one at a time and put in rack. As I do so the basin fills up with the soapy rinse water. I have a full basin at the end of the wash. I can use this water to wash a kitchen rag to wipe down counters and/or I can use this water to rinse off another load of dirty dishes and/or I can use this water to rinse out recyclable containers like the above-mentioned peanut butter jar. Then this water I pour into a greywater bucket to water plants outside. So this potable water has potentially five uses: rinsing, washing rag, rinsing dirty dishes, rinsing dirty recyclable containers, watering outdoor plants.

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In areas with commingled recycling, one of the arguments made for washing plastic and metal containers is contamination of paper and cardboard in the bin. One leaking unwashed can could taint the entirety of the paper and cardboard in the bin, making it unsuitable for recycling, plus the resulting mess may lead to things sticking together, making the automated sorting not work.

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