My partner recently quantified energy use on two of his computers and learned that his 10-year-old Thinkpad consumes 35W when it isn't doing anything in particular, while the much newer Thinkpad he uses for work consumes more like 8W.

As a huge fan of old Thinkpads with strong environmental values and who also tries to avoid discarding old things that are still functional or buying new things I don't need (largely for environmental reasons), I'm at a bit of a loss for what to do with this information : (


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@dynamic The energy consumption of a laptop means very little in the grand scheme of things. Turn your air conditioner's thermostat up by a degree or drive a few miles less and keep it.


We don't have an air conditioner installed and I don't drive a car.

@dynamic Excellent! Take a shorter shower, then. One liter of hot water is equivalent to about 2 hours of run time on that laptop.

@dynamic Or just take heart in knowing you use about 1/10th the energy I do. I am at least on a 100% renewable electric plan. My biggest contribution to the environment is probably the fact that I moved to a 100% remote job even before lockdown came, so we dropped to 1 car which doesn't get much use. It was the electric car we gave up, though, because I was leasing it. But we have air conditioning and don't even open the windows at night because of allergies.

@dynamic the embedded carbon cost of that laptop is much higher than the difference of 35-8W, even over a year running a new one. keep what you have, upgrade when it is unrepairable.


Do you happen to have a reference on this?


Hmm... this part, "The same dynamic explains why newer laptops don’t show lower operational electricity consumption compared to older laptops." appears to be demonstrably false...

(Not that it is particularly relevant to the question of whether resource investment in computer manufacture offsets improvement in energy efficiency.)

@dynamic yeah sorry I don't think anyone does complete breakdowns of embedded carbon in stuff well, because it's too complex tbqh.

@dynamic if the carbon footprint of making a new laptop is on the order of 300 kg CO2e, the 27 W difference (which would require roughly 33 W of generated energy at the power plant) represent around 30 kg CO2e per year in Germany if you use it 6h every day.
So it would take 10 years to make it worth changing.
In France it would take almost a century...
So if you're in Germany and use it more than 6h a day, it's done its time, change it, otherwise keep it


Thanks. Where do you get the 300 kg CO2e number?


Hmm. Seems like another number I really need is the life expectancy of a new laptop. My working assumption is that the older Thinkpads last longer. They are certainly more user-serviceable.

@dynamic yeah, sorry, must have been tired, my reasoning did not make much sense... hopefully the numbers are still correct...
I think lifetime is hard to guess so it might be reasonable to just use how much you use the laptop and your energy mix to test whether the time is compatible with a potential laptop life expectancy...

@tfardet @dynamic Another complication here is that newer computers tend to be less maintainable, and in particular you have to throw out more of the computer rather than replacing parts piecemeal (battery, RAM, processor...)

@varx @tfardet

This makes me even more eager to quantify energy expenditure by a desktop computer.


Also, for reference, I am in the U.S. We're signed up for an electricity program through our city that is described as 100% Local Green, but it's not entirely clear what that means.

The sources of electricity are stated to be, "1) Zero emission sources, such as solar, wind, low impact hydropower2; and 2) Sources that destroy methane, such as anaerobic digestion," with the followup statement: "Other forms of biomass are explicitly not purchased by Green Energy Consumers Alliance, due to their positive emissions of CO2 during their life cycles."

I'm not entirely comfortable with their apparent assumption that intentionally setting up anaerobic digestion as a fuel source is a reasonable basis for saying that the energy is "methane destroying."


Also, if I recall correctly, I think that what the 100% means is not that that is now our electricity is actually generated but that 100% of what we pay goes toward development of these kinds of renewable sources, which... I have a hard time evaluating.

@dynamic @tfardet They list the specific power mix at . I'm pretty sure all the electricity has to come from renewable resources that exist today, not future projects.

It seems like to be considered "methane destroying" it should be methane that would have otherwise been released. If they can collect it and turn it into electricity the law probably already required it to be flared.

Both sides of my family are from Springfield MA by the way.

@freakazoid @dynamic what they say seems reasonable: biowate would rot and generate methane if left alone or landfilled and burning it directly is inefficient because of its high water content so anaerobic digestion indeed prevents methane release in the athmosphere and is energetically efficient.
Also nice to see they avoid burning biomass!
However, though I think it's great to use such provider, I think you should use MA grid's mix since that's how you get your electricity (~ 370 gCO2e/kWh)

@freakazoid @dynamic the reason being that you need the grid (and the fossil/nuclear plants on it) for stability, so you could most probably not get your electricity when you want, in the amount you want if not for it.
In that sense, you rely on your state's electricity mix for your electricity consumption.
Having a "green" energy provider is more like your contribution to the transition and the future (at least that how I see it).

@tfardet @freakazoid

What Tanguy is saying about using the full grid's mix makes sense to me. The source of the electrons doesn't magically change when you change what electricity plan you are subscribed to.

It isn't clear to me how different this is from what I'd originally said about the money being used to pay for development of green power. I've been kind of hazy on how the details of the plan work.

@tfardet @dynamic I am pretty sure the demand needs to be satisfied at the time it exists. But it will change the mix “attributed” to more flexible customers in the short term. Base generation includes hydro, though, so I don’t think that’s a particularly big deal.

Ultimately, the goal is to signal demand for more renewables, and using a 100% renewable plan seems like a decent way to do that. You’re acting as an early adopter.

@tfardet @freakazoid

I don't know a lot about industrial scale biogas production, but I do know that at the household scale you can use either aerobic or anaerobic composting to process organic materials.

For anaerobic composting, you saturate the stuff with water and it starts to bubble. Ideally you then harvest the biogas (I've only done this accidentally, but I believe the principle is the same for a household scale biogas digester).

For aerobic composting, you mix in lots of fibrous material (wood chips, hay, paper, etc.) to give the stuff structure and sometimes you mechanically churn it, although mechanical churning is not required, especially if you have invertebrates like worms or black soldier flies digging around in there.

I don't see any reason why aerobic composting couldn't also be used at an industrial scale.

@dynamic @freakazoid sure, aerobic composting can be done at industrial scales but it does not lead to energy production and can produce methane and other GHGs.
Furthermore, given current agricultural legislations and standard use, we would unfortunately overproduce compost compared to the agricultural demand if we converted all biomass into compost

@tfardet @freakazoid

My impression is that methane emissions from a properly managed aerobic composting system should be minimal, certainly much less than from a biogas digester, so framing biogas digestion systems as "methane destroying" still bothers me.

The introduction to this paper generally supports this impression:

The author's write: "Methane emission from composting has different ranges of production rates, from very low, near the detection limit of the equipment in industrial composting [16], [23], to the highest as 12% of initial carbon on static pile composting [27], [23]."


It's true that other emissions are involved in composting. The paper I cited in the previous toot points to N2O as the big culprit (other than CO2, of course). Again, aerobic composting reduces emissions compared to anaerobic, but it appears that this hasn't been quantified as well:

This paper ( points to something on the order of an 85% reduction on N2O production for one aerobic system, and 15% isn't nothing.


It seems to me that the big advantage of biogas over aerobic composting systems with regard to emissions is that while both of them ultimately produce CO2, the biogas system grabs energy along the way by staging the carbon first as CH4 that is burned for energy. This is a pretty good selling point, but is not what Somerville CCE is emphasizing by framing biogas as "methane destroying."

It's a different story if existing landfills (etc.) are being capped, and the methane emissions deflected to be used in energy production, but it's not clear that that is what they are talking about.

@dynamic yes, exactly, anaerobic digestion is more energy efficient while composting provides organic carbon that is better for soil life at the cost of major carbon (and therefore energy) loss...
If they compare anaerobic digestion to landfilling and most other current waste management, I still think their point is not too incorrect.
I do think we could use more compost in agriculture, it just requires organizational changes

@tfardet @freakazoid

The point about overproduction of compost relative to agricultural demand is an interesting one, and I'm not sure how easy or hard it is to get around that by first using the compost to grow non-edible biomass (e.g. incorporating hydroponics into sewage processing) and then composting that biomass for agricultural purposes. I believe this kind of system is better aligned with policy, but it occurs to me that the second biomass production step might also add a lot of bulk that then needs to be dealt with.

@tfardet @freakazoid

By the way, you might be interested in reading about Boston's sewage treatment plant at Deer Island. It uses biogas digestion to generate methane, and the nutrients are converted into a pelletized fertilizer which is then sold.

@dynamic @tfardet Any biomass can be gasified and/or burned. It’s just a question of the quality and therefore economic efficiency of the process. It’s usually not worth transporting biogas because of its low heating value, so it often just gets burned or otherwise utilized on site. You can then capture the CO2 if you want and use it for something else, or sequester it.

@tfardet @dynamic Using pure oxygen for gasification improves the heating value of the output gas and reduces NOx formation, so maybe it would be advantageous to collocate an air liquification plant, especially if the system puts out enough energy to power it. You could use the Fischer-Tropsch process to produce liquid hydrocarbons, or generate hydrogen using the water gas shift reaction and use it to generate ammonia or whatever. Use the CO2 to make concrete.

@tfardet @dynamic I want to put all this stuff in a simulation game. I’ve gotten close using Factorio mods, but not as close as I’d like.

@freakazoid @dynamic I'm not very familiar with other methods than anaerobic digestion and composting, is it possible to separate the nutrients (N, P, K...) from the carbon afterwards?

@tfardet @dynamic Potassium and phosphorus will be left over in the ash. Other than animal manure, compost tends not to be a good source of fixed nitrogen, because it gets used up fairly quickly during the composting process. So animal manure for fertilizer tends to be very lightly composted, if at all.

@tfardet @dynamic Your best bet for nutrients is probably municipal sewage. As bacteria in the sewage start turning uric acid from urine into ammonia, it lowers the pH, and the ammonia combines with magnesium and phosphorus and precipitates out as magnesium ammonium phosphate, a useful fertilizer when it's not clogging your pipes and sewage treatment plant. Deliberately precipitating it (potentially adding magnesium) helps keep your treatment plant flowing and produces a useful product.

@tfardet @dynamic You can make this yourself very easily with urine just by putting it in a jar and sealing it. There's not enough magnesium to precipitate it all out, but you can get soluble forms of magnesium as powders marketed as supplements. I haven't yet done this experiment because my wife isn't too keen on my having jars of urine around.

@freakazoid @dynamic yes, I'm familiar with these processes, what I wondered was regarding the methods you mentioned earlier (gasification, the Fischer-Tropsch process, thermal depolymerization): what final products do you get from these and can you separate N, K, P from the rest into forms that would be usable as fertilizer?

@freakazoid @tfardet

I thought making concrete was a CO2 source, not sink?

@dynamic @tfardet There are carbon-negative processes, but it remains to be seen if they can be made economic. You use magnesium silicates instead of lime, from olivine, talc, or serpentine. Those will naturally absorb carbon as they weather, so using them to make carbon-neutral concrete acts like an acceleration of the weathering process with a useful by-product. It's mainly a question of whether it's worthwhile compared to other means of accelerating the weathering process.

@dynamic @tfardet Incidentally, there are enough of those minerals to absorb all carbon on the planet and kill off all plant life and everything depending on it. Which will happen long before we have to worry about the sun stripping away all our water. So if we're still around we're going to have to start adding CO₂ back to the atmosphere. Which will be a lot easier if we've left a bunch of fossil fuels in the ground!

@dynamic @freakazoid @tfardet it's concrete generated from CO2 using carbon capture: you prevent the release of the CO2 in the atmosphere and trap the carbon by making it into a solid material

@freakazoid @dynamic I don't know whether that's a direct response to my point so just in case, I meant that directly burning biomass such as green or kitchen waste is not great because, given it's high water content, you end up losing most of the energy due to the water's the latent heat of vaporization...

@tfardet @dynamic Oh, sure. You usually have to dry it out first. There are some processes such as thermal depolymerization that benefit from moisture because they require steam, but even those tend to require that the moisture content be carefully controlled. And of course if you have to leave it out in the sun to dry that takes space, attracts pests, and you lose some of the energy content to decomposition.

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