I use up batteries (both recyclable and not) at an exceedingly slow rate. Stockpiling batteries for proper disposal is not realistic as I will do so for years, if not decades. All the more so, since I live in a very tiny place.

If I do my errands in a milk-run, stopping off at a box store to dispose of (say) a pair of AA batteries, I wondered whether the environmental cost of restarting the car was worse than simply putting the batteries in the garbage. I am cognizant that starting a car uses a lot of fuel, probably equating to 30 seconds of idling. It makes me wonder about the whole wisdom of it all.

I realize that it is a complex question, since it entails speculative quantification of complex factors. But are there any big factors that render the choice clear?

The natural follow-on question would be at what volume of spent batteries would it be worthwhile to stop the car. This is a tougher question, as it is more nuanced than simply looking for big factors that clearly indicate which of two options is better.

  • I am cognizant that starting a car uses a lot of fuel, probably equating to 30 seconds of idling. Do you have a source for this? There have a been a few discussions here on that topic, and it seems starting your car uses less gas than idling for about 10 seconds.
    – LShaver
    Commented Jun 24, 2018 at 16:25
  • 1
    Another thought -- perhaps other places you already go accept batteries? My office recycles batteries, so I bring mine there. A university I attended collected batteries at libraries. Ask around -- bringing a pair or two whenever you go will solve both problems!
    – LShaver
    Commented Jun 24, 2018 at 16:27
  • I thought starting an engine equates roughly to 30 seconds of idling because of old wisdom about turning off the car if you intend to idle for more than half a minutes. I looked at your link, and the 10-second rule also seemed to be without a source. But the fuel cost is more than just starting, is slowing down, parking, unparking, weaving out to the road again, and re-accelerating. It pales in comparison to other driving inefficiencies, but again, I'm wondering about whether this can be compared to the harm done by a pair of AA batteries in the land fill, and whether one is clearly worse. Commented Jun 24, 2018 at 16:48
  • About going to where I've done before, I dispose of batteries so rarely that, not only am I unable to recall the last disposal, but the company arrangements and the companies themselves have changed. Commented Jun 24, 2018 at 16:49
  • That answer links to one on Physics.SE which calculates the idling vs restarting time to about 3 seconds for a Honda Civic. 10 seconds was the (very) conservative estimate for a broader range of vehicles. Also, where do you live? Your municipal solid waste collector's website can likely provide guidance on how to dispose of batteries. I once lived in a municipality where we could put them directly in our recycling bins to be sorted.
    – LShaver
    Commented Jun 24, 2018 at 17:03

2 Answers 2


There is much more at stake here that just the car fuel. Batteries contain all kinds of metals that have to be mined and processed, that are a danger when released into the environment (e.g. seeping out of landfills), and that can be re-used when the batteries are properly recycled.

Just collect your spent batteries and then once of twice a year, hand them in at a proper place for recycling. Especially if you are already doing other shopping nearby, my opinion (I don't have hard data about all the life cycle factors involved here) is you're doing the second best thing*.

* The first best being to reduce your battery usage (reduce - reuse - recycle)

  • I already minimize battery usage. This is the 1st time I've run a disposal battery to the ground in so many years that I can't even recall. That's the problem -- accumulating the batteries for disposal doesn't really make sense because I will hang on to them possibly for the rest of my life. They'll likely leak before I have a decent amount. It seems to make sense to return them right away, but does the car resultign car exhaust (not the cost of the fuel) do more environmental harm? Batteries leaking into landfill create focused local damage while car exhaust creates dispersed global damage. Commented Jun 24, 2018 at 14:56
  • Disposing of batteries every 0.5-1 year is OK if you use many batteries and are comparing with the alternative of making the trip more frequently. But the trip to dispose of batteries should depend on how many you've accumulated -- not frequency per year. If it doesn't make sense to make the trip with (say) 10 batteries, then it doesn't matter whether you reach 10 batteries in 2 months or 20 years. Commented Jun 24, 2018 at 15:18
  • Similarly, if the trip is justifiable after 50 batteries, it doesn't matter when you reach 50 batteries. But determing the minimum threshold quantity at which you should make the trip is extremely complicated. This also ignores the fact you can't keep spent batteries forever. Commented Jun 24, 2018 at 15:19

Not having room to store spent batteries sounds implausible. This requires a value of 'tiny' that implies you don't store a day's food, have only one change of clothes, and roll up the tatami mats each morning so you have room to dress.

Figure out a way to cache spent batteries until you get a worthwhile number.

  • A can on top of the fridge, or on a bookcase that isn't stuffed yet.
  • A bag hung on a doorknob on the back side of a closet door.
  • A new shelf added just below ceiling level for containers that don't get accessed very often
  • In the same box where you keep new batteries. Mark the spent ones with a felt tip.
  • A container with lid that you keep in the car where you accumulate the batteries.

If you are in an apartment set up spot in the laundry facility and collect not just yours, but all the batteries for the building

  • 1
    The gist of the question was to get some considerations on what threshold quantity of batteries would make a trip worthwhile. Commented Sep 4, 2018 at 2:14

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