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  • Writer's pictureDr. Lee Anne Willson

Locking in future emissions

“Lock-in” was heard frequently at the Glasgow climate summit. It means building or buying something that will continue emitting greenhouse gases for years or decades to come, thus “locking-in” the emissions unless one is willing spend extra money to stop using it before the end of its natural lifetime.

The natural lifetimes of various emitters are shown in this chart, for sources of electricity, industrial processes, buildings and transportation. On a household scale, within the next seven years roughly half the residential cook-stoves now in use will likely be replaced, an opportunity to switch away from gas and towards high-efficiency induction cooking or at least to electric. Within 9 years, half the cars will be replaced, a chance to replace these with electric vehicles (EVs). Residential heating and cooling units have a lifetime of about 20 years, so half of them probably will be replaced within 10 years, another opportunity for a lower-emissions choice. On a city-wide scale, replacement of the Ames Power Plant or the switch from coal to gas will decide the emissions from these facilities for 30-50 years.

If Ames builds a new power plant to convert waste to energy, it will be locking in 30-50 years of emissions from burning the waste and the gas needed to burn it. If ISU converts its plant from coal to gas, as planned, it may also be locking in emissions for a long time. Is now the time to replace these facilities with alternatives, or is it better to plan for those replacements later? If we replace now, can we or should we plan for a reduced span of use?

Examples on a domestic scale

I used the Cool Climate Calculator ( to estimate where the emissions are coming from for our household. In the two main categories, the ones where they use gas bills, electric bills, and car miles to compute emissions, so are probably most accurate, I get this plot of tons/year:

When putting in my numbers, I chose 75% sustainable sources for electricity, from the Iowa average (57% wind) plus having a number of SunSmart shares. That makes natural gas (furnace, water heater, stove and gas fireplace) the biggest single source of greenhouse gas emissions, and car fuel (two combustion-engine cars that only run 3-4000 miles/year) as a close second. What can I do to shrink those two pieces?

Buying new – maximum lock-in

If I went out tomorrow and bought a brand-new car, I would be locking in about 15 years of emissions from that vehicle. Even if I were to replace it with an electric vehicle a couple of years from now, the emissions would still happen, because that car would continue in use by someone else for its normal lifetime.

The same issue arises if I purchase a new stove, furnace, or water heater, items with 10-20 year expected lifetimes. As part of my personal carbon-reduction quest, I plan for my next car to be an EV, my next stove to be an induction-top electric stove, my next water-heater to be an electric on-demand heater, and I would like to augment my furnace with a heat pump. In the meantime: Should I retire any of these items early?

Replacing what I have before it dies – when does that help?

I could choose to replace some of these high-emission items before they wear out. Assuming that I can afford it, would this be the right thing to do? There are costs, including carbon emissions, associated with constructing these items, and with disposing of them, so replacing them ahead of schedule is not emissions-free. Also, if the object would go on to a new home with someone else, is there a point in replacing it early?

Right now, I have an 8 year-old car with less than 25,000 miles on it. Should I retire it in favor of an electric vehicle? From the Berkeley Cool-Climate calculator result for our household, my car is emitting about 1 ton/year; at estimated prices for offsets of $6-$60/ton this suggests it would be cheaper to keep the car and buy offsets. On the other hand, if I buy a new EV, I am supporting the industry that is building EVs, and helping to bring the price down as the number of such vehicles increases. I’m also encouraging the installation of EV charging stations. I know someone who would like to replace her large car with a smaller one like mine. If I sold my car to her, this would reduce her emissions somewhat. On balance, this seems like a good choice from the climate perspective – reduce my emissions substantially, reduce hers somewhat, and not end up junking a perfectly good automobile.

We also have a gas stove, about 8 years old; it came with the house when we moved in three years ago. It is in fine condition. It doesn’t get a lot of use; with just two of us at home, I have moved a lot of my cooking to electric appliances (crock-pot, toaster-oven, microwave). I’m not thrilled when I see the indoor CO2 levels rise steeply when I use the gas stove, and would be happy to have a new induction/electric stove for safety reasons, even though it means I would need new cookware. On the other hand, I make minimal use of the gas stove, and it is only a small part of our gas bill. If it were to go to a new home, it would probably get a lot more use, thus contributing more emissions. It is probably about half-way through its natural lifetime in a domestic setting. My conclusion is that this is not a high priority for early replacement; and I could get bigger reductions by considering other options, such as a installing a heat pump (to reduce the use of gas for heating, and electricity for A/C), or an electric on-demand water heater. Here, again, I could purchase offsets until the time comes to replace these items.

These domestic examples show the kinds of considerations that go into dealing with potential lock-in: What to buy when replacing an item, whether to retire a high-emission item before it wears out, and when it may make more sense to continue using an item and instead invest in offsets.

Buying used – when is this a good strategy?

In the situation involving the purchase of a car, if I assess the availability of charging stations, and my low mileage per year, I might conclude that it is too soon for me to switch to electric, but that within five years or so this will become the better choice. In that event, if my current car died tomorrow, one option would

be to purchase a used internal combustion car – already locked-in to a certain level of emissions, but fewer years remaining than for a new car – and avoid supporting the manufacture of additional non-electric vehicles. This can be a win-win plan, if a stronger market for used items encouraging those who can afford it to upgrade to low-emissions alternatives.

City scale examples

The city has potential new lock-in in the Ames Power Plant, the buildings used by the city, the Cy-Ride system, other vehicles used by the city, water treatment (before and after use), and the management of our garbage.

One way for a city to make these decisions is to associate a dollar cost with the emissions. Then the cost per year one uses for choosing becomes can be visualized as a sum, and adding the cost of emissions can make a lower-emissions option more attractive:

Without calculating the cost of emissions, the lower example would appear cheaper (red, purple and yellow areas); including emissions (green) the lower example becomes the more expensive option.

Above, I mentioned purchasing offsets until it is time to replace an item with a low-emissions alternative. There are a number of ways to compute the carbon cost of emissions in dollars, and I will probably review them in a future blog. For the purpose of evaluating the options, I suggest for now estimating $50/ton until you have identified a specific offset to purchase. Another option for Ames residents is to reduce our household emissions by buying shares in SunSmart, and investment that ultimately pays for itself.


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