Now and then I hear battery-operated versions of various machines touted as “environmentally friendly” because they produce zero emissions. Of course, a moment’s thought shows that this is not true–or not necessarily true, anyway. A battery stores energy, and if the energy in question came from a coal-fired power-plant then the battery-powered machine is responsible for a a lot of emissions. Those emissions are simply somewhere else.
But is that the only caveat batteries carry? Between personal electronics and new “greener” technologies such as hybrid and plug-in electric cars, batteries are a huge part of the modern energy landscape–and yet, I realized, I didn’t really know much about how they work or what problems they might cause. I set out to learn the basics, and here I pass them on.
As I’ve been saying for years, rechargeable batteries only store energy, they don’t create it. Of course, nothing except whatever started the Big Bang creates energy, that’s part of the First Law of Thermodynamics, but a gallon of gas is an energy source in a way that a battery isn’t. Most people know this, but don’t seem to really think about it. For example, plug-in hybrid cars receive praise for their wonderful gas mileage even though that’s the wrong measure of efficiency for those cars. Such a hybrid could be an absolute energy guzzler, sucking down kilowatts, and still use very little gas. And if the electricity comes from a coal-fired power plant, the carbon footprint of a plug-in could actually be higher than for a traditional car of the same weight and engine type.
But batteries do not store energy the same way a jug stores water. For one thing, electricity, by nature, moves. You can’t keep it in a box any more than you can shine a light into a closet, close the door, and expect the brightness to still be there when you get back. Instead, a battery converts chemical energy into electricity–and back again, if it’s rechargeable. That means that beyond asking where the energy comes from, we also have to ask what happens to it inside the battery and whether storing the energy is actually a good option.
I had a really hard time tracking down information, here, in part because I didn’t understand the right questions to ask. In turns out the answers are both very technical and very specific to each battery type–turns out “a battery” is something like “a sandwich” in that all the members of the category look recognizably similar and all accomplish roughly the same thing, yet the insides of two batteries might have no more to do with each other than do peanut butter and roast beef. I didn’t research all possible types of batteries, and I am very far from being an electrician, but I can give you the questions I’ve found–and a few examples of some answers.
- How efficient is the battery?
- Can old batteries be recycled into new batteries indefinitely?
- What is the environmental impact of building and eventually disposing of the battery?
- How does the battery compare with relevant energy alternatives?
How efficient is the battery–and its charger?
When you put energy into a battery, how much of it do you get back out again? The answer depends on the battery type, its age and condition, and how it is being charged, but it’s never 100%. First of all, every time energy changes form, some of it dissipates, as per the Second Law of Thermodynamics. Charging a battery converts electrical energy into chemical energy, so some is lost in that process. Some is lost again when the battery is used, converting chemical energy to electricity. And of course charging a battery requires a charger, which is also not 100% efficient for a similar reason. For example, depending on its initial state of discharge, an eight-hour charge cycle for a lead-acid battery could be anywhere from 36% to 64% efficient. That means that if you’re charging car batteries to do a job that you could just as easily accomplish with an extension cord, you could find yourself using almost three times as much electricity as you really need. The picture gets worse if you leave the charger attached too long; these batteries accept less and less charge the closer to full they get and the electricity they don’t except just makes the battery hot. It’s wasted.
Can old batteries be recycled into new batteries indefinitely?
Not all batteries are rechargeable. It is possible to make a crude battery out of half a grapefruit and those don’t need an initial charging–the energy is present in the relationship between the fruit juice and the electrodes. If commercially available batteries also don’t need an initial charge, then they are, essentially, a form of fuel and we need to ask the same questions about them as we would with any other fuel–like, are we going to run out?
I was unable to answer this question, because internet searches on charging non-rechargeable batteries yield websites all about how to recharge non-rechargeable batteries (which, by the way, is a bad idea. We tried by accident some years ago and very nearly killed out cat in the process). But it doesn’t really matter because the important question–are we going to run out–applies to all batteries regardless of when or if they are charged. To put it simply, any battery made of something that cannot be recycled back into the same type of battery indefinitely is unsustainable long-term.
As far as I can gather, at least the primary materials in many popular battery types, such as lead or lithium, are closed-loop recyclable in theory. These are metals, and metals are pretty simple to work with. But that doesn’t mean they are being recycled. The issue is whether the price of the material is actually high enough to pay for the processing. With the exception of lead, it generally isn’t. In some cases, even the carbon footprint of recycling could be larger than that for mining, though I have not seen an analysis of that. Sometimes batteries are recycled at a financial loss for environmental reasons, but this isn’t closed-loop recycling. Recycled lithium might be sold for use as a lubricant, for example. Even in the best case scenario, most batteries also have non-recyclable components, such as plastic, that recycling centers simply incinerate.
What is the environmental impact of building and eventually disposing of the battery?
Potential environmental impacts include the life-cycle carbon footprint of the battery (how much carbon dioxide-equivalent greenhouse gas it is responsible for, from mining through final disposal), physical disruption of the land associated with mining, and any toxicity related to disposal. Again, the answer depends on battery type, but we just don’t have all the answers. For example, cadmium in the ocean might have come from batteries, but then again it might not have. Life cycle energy analyses have not been done for all battery types, and some of those that have been done may be out of date. Generally, lead-acid batteries have the lowest energy footprint and are the most recyclable, but they are also quite toxic if not recycled.
How does the battery compare with relevant energy alternatives?
This question is the big one. In some circumstances, batteries are clearly the best option around. They make small-scale solar or wind power generation practical, for example. Without them, these systems would only deliver when the sun shone or the wind blew. In other circumstances, since as in the duel between a lead-acid battery and an extension cord imagined earlier, they are clearly wasteful. Still other times, they fall into a gray area of very nuanced decision-making.
Any time energy changes form, some of it is lost. Part of overall energy efficiency is therefore keeping the number of transformations as low as possible. For example, if you have several gallons of gasoline and want to boil water, your best bet is to use some kind of gasoline-burning stove. Using the gas to power a generator to make electricity to run an electric stone is wasteful because it involves so many more transformations. If everything else is equal,therefore, any kind of heating device, from stoves to baseboards to clothes dryers, are better run on gas than on electricity, if the electricity was generated by burning fossil fuel (as it often is). But everything is not always equal.
For example, how energy-efficient is gas delivery? If it has to come a long distance by truck (in which case it will probably be propane, not gasoline), the calculation might even out. The situation gets even more complex with motors since the relative weight of different designs and the circumstances of operation all come into play. For example, a battery-powered car does have emissions, it simply has them at the power station not at the tail-pipe. But if the car drives into an area that is very vulnerable to pollution, leaving the emissions behind at the plant might be important.
What does it all mean?
The bottom line is that batteries are not a panacea. In fact, they make thinking about environmental issues much more complicated. They’re handy tools for “green-washing,” as long as the public believes that battery power always means pollution-free. But they are also important tools for increasing overall energy efficiency and sustainability, especially if used in concert with electricity generation from renewable sources.
The important thing to remember is that we can’t create energy, nor do we get to decide how much energy a given task requires. If you want to accelerate a two-ton vehicle up to sixty miles an hour, that will take X amount of energy whether you use a gas engine or an electric motor to do it. The electric version might well be better in some respects, and if so then that is definitely the version we should pick. But mobilizing that energy always comes with some cost, somewhere, and if we can’t see what the cost is, we need to start asking questions..
The only way to truly go “zero emissions” is to use less energy in any form.