People like plastics and mild winters
12. Grocery bags and a surprising weather model
Note: The views expressed here are the author’s own and do not reflect the views of Energy Impact Partners.
Housekeeping
Last month, I had half of a career update. This month, I have the other half! I’ve joined the investment team at Energy Impact Partners. EIP is an investment firm operating a variety of funds, but my main focus is the Deep Decarbonization Frontier Fund. The Frontier Fund invests in early-stage, revolutionary technology companies that accelerate the transition to net-zero greenhouse gas emissions. If you’re building such a company, you know where to find me. Back in January, EIP announced an early close of the Frontier Fund, and I can’t wait to share more in time.
In the meantime, I get to say a rare thing in the world of venture capital in 2022: we’re hiring! Drop me a line if you’d like to chat.
Now back to our regularly scheduled programming.
Plastics
Plastic waste is a bad environmental problem, but it’s not obvious to me that it’s a huge climate problem. If you squint, single-use plastics are just oil that we’ve managed to keep in (or on) the ground. We mined and refined a mineral, formulated it into a product, and then someone used it and threw it away. Sure, that process required energy and produced emissions, but at least you didn’t just burn the oil.
Of course, at some volume of plastic production, those emissions do add up to a problem. Unfortunately, we’re basically there: estimates of plastic-related emissions are in the range of 1-2 gigatons CO₂e/year (a few percentage points of total GHGs) and rising.
Our reaction to the plastics problem has been to start transitioning to reusable products like cloth bags, biodegradable wrappers, metal straws, and so on, which feels like a good step. But it’s not clear to me that they’re actually a good idea. Reusable materials and alternative plastics are typically bulkier and more highly processed than their conventional counterparts. And while they may offer a less bad end-of-life waste problem, there may be significant environmental harm upstream of any consumer use.
To figure out which kind of material is less bad, you’d want to run a breakeven calculation that factors in all those things. Taking greenhouse gasses as our impact metric:
GHGs per functional unit (single use) = GHGs per functional unit (reusable)
Breaking it out into mass per “functional unit” (i.e., how much of a material constitutes a grocery bag), GHG footprint per unit mass, and number of uses, you get this:
(Mass/FU) * (GHGs/Mass) / (1 use) = (Mass/FU) * (GHGs/Mass) / (n uses)
In theory, all these variables are knowable, and you’re straightforwardly solving for n: how many reuses do you need for the reusable product’s environmental footprint to be worth it?
But in practice, it’s it’s hard to make broad statements about a material class for a bunch of reasons:
We have a wide variety of plastics, biopolymers, papers, and woven materials that are interchangeable to varying degrees.
These materials have a wide variety of applications, and those applications may be best suited to different materials.
There may be more than one way to make a given material, with differences in accompanying environmental impact.
Different materials may not yet be fully scaled up, which makes it harder to compare environmental impact directly with fully scaled up materials.
Which kinds of environmental impacts do you care about?
There are plenty of other nits that a sufficiently motivated person could pick.
So it warms my heart to see that people much smarter than me (Hannah Ritchie and Max Roser at Our World in Data) have gathered the hard numbers to pull off exactly this breakeven calculation along a number of dimensions:
Note: it’s not stated in the graphic, but the numbers of reuses are given relative to a standard LDPE (low-density polyethylene) single-use plastic bag. You know, this kind.
With this in hand, here are a few of my takeaways:
I expected reusable materials to be worse on GHG emissions, but I didn’t expect them to be worse along other environmental factors!
Cotton is rotten. Across the board, cotton is tens to thousands of times more damaging than single-use plastic.
Organic cotton is worse than conventional cotton. While I’m no expert on organic production, in other arenas like food, “organic” means more land and resource use per unit product.
Recycled plastics are worse than virgin material – along every dimension!
Biopolymers (including paper) can get to net-zero emissions. Not having dug into the numbers, I’m guessing the rough math is: carbon-negative feedstock + minimal production emissions + end-of-life biodegradation ≃ zero. But I have some doubts here.1
Maybe I’m just a bad guy, but I can’t think of any reusable grocery bag I’ve used more than 52 times.
Drop a comment or reply if you have others?
This isn’t to say that replacing today’s single-use plastics is a bad idea. It’s a good idea! The environmental and climate impacts are real. But it does raise the bar for potential solutions. They’ll need to do better than the highly optimized plastics we make today. Here’s what I’d look for in potential solutions:
Replaces at least one of the major plastics (PET, LDPE, HDPE, PP, PS, PVC) at scale
Does at least one of the following:
Decarbonizes ethylene production (much of plastic’s GHG impact traces back to ethylene refining)
Significantly outperforms at least one of the major plastics as a material (e.g., stronger, lighter, lower gas permeability)
Uses carbon-negative precursors
Avoids end-of-life biodegradation to methane
Has a pathway to cost parity or advantage
This is a tall order, and I’ve only seen a few ideas come close – for example, ReSource Chemical’s bio-derived PET replacement. If you think you can pull it off, shoot me a note. I want to believe we can conquer the plastics problem.
Weather
Sometimes people use the “frog in boiling water” fable to describe our lackluster response to climate change. I trust that you know it, but just so we’re all on the same page:
They say that if you put a frog into a pot of boiling water,
it will leap out right away to escape the danger.But, if you put a frog in a kettle that is filled with water that is cool and pleasant,
and then you gradually heat the kettle until it starts boiling,
the frog will not become aware of the threat until it is too late.
The frog's survival instincts are geared towards detecting sudden changes.
It’s a fine metaphor. But here’s one thing it leaves out: when the water first starts getting warmer, it’s actually kind of nice! You’re not a frog in boiling water, you’re a frog in a hot tub.
For some parts of the world, this is the stage of climate change we’re in. Look no further than Boston. For a transplant like me, winter is miserable. It’s cold, the sun goes down at 3:30, and it snows 50 inches per year. It’s no wonder seasonal affective disorder affects millions. So in January 2020, when we had back-to-back 70 ºF days, I put on shorts and went for a run. It felt like the entire city was outside – the best days of a mild winter. Because I’m a climate weirdo, I felt guilty about it, but hey, it was great! Was the following summer hotter than normal? Sure, but you would have needed AC anyway.
A little while back, I came across a 2016 Nature paper showing that this phenomenon is basically happening across the US: because winters are getting warmer faster than summers are, “80% of Americans live in counties where weather has improved over the past four decades.” That’s right, improved!
As scientists do, the authors came up with a complex metric for something we can sense intuitively: “weather preference index,” or WPI. Here’s what WPI looks like over four decades: scattered, but trending upward.
You might wonder how they quantified something so subjective as weather preference across an entire population. The way they do this is pretty clever – assessing people’s revealed preferences by watching population growth by area while controlling for other factors:
As objective measures of the average American’s weather preferences, we used estimates of revealed preferences produced by a sizeable literature analysing the effects of local climate on population growth. These studies estimate change over time in population or net migration at the city, county or metropolitan-area level as a function of normal weather and a set of control variables. We used each study’s coefficients on weather-related variables to assign regression scores to our county-level weather data. With these values, we calculated an annual weather preference index (WPI) score for each county, an indicator of the average American’s revealed preference for different types of weather conditions. The WPI’s unit of measure is the ceteris paribus expected rate of population change associated with that year’s weather. In using these studies for our purposes, we assume that, all things being equal, Americans move to, and continue to reside in, places with local climates that they prefer.
I don’t know if I buy that it’s really possible to control for all other factors, but for now, let’s assume they’re right.
You might wonder what happens to WPI as climate change starts to set in – surely it doesn’t go up forever. And you’d be right. The authors also projected WPI out to 2100, and lo and behold, it goes down. This seems bad but makes sense: although the milder winters are nice up to a point, in time they will be outstripped by the downsides of climate change. As the authors note, “we estimate that 88% of the US public will experience weather at the end of the century that is less preferable than weather in the recent past.”
But here’s where things get interesting: to model the climate out to 2100 and inform projections of WPI, the authors used two well-known climate change scenarios: “RCP8.5” (shown in red) and “RCP4.5” (shown in blue). RCP8.5 refers to unabated emissions and 3.2–5.4 ºC warming by 2100 – a climate modeler’s version of “fuck around and find out.” RCP4.5 models emissions peaking around 2040 and then declining – a more intermediate scenario.
Now, this paper was published in 2016, and lots of things are different now. One of those is that we’ve started taking much more climate action as a society. RCP8.5 was never exactly the path we were on, and every day it gets a little less crazy to think that we’re heading toward RCP4.5.
Two things come out of this for me. First: This chart is a new way of illustrating what we’re working toward in the climate community. We’d like as much of the planet to be pleasant and livable for as long as possible. The mitigators are working to move us toward the blue line, and the adapters are hedging against the red. I don’t think I’ve ever seen someone show it like this before.
Second: Only in the worst-case scenario does the weather get worse in the US, and only in 2050 does it start to dip below baseline. In an intermediate scenario, we have better weather than we did in 1974 for the rest of the century.2 This is totally wild.
I tend to believe that quality of life will go up on average, despite the effects of climate change. But I generally think about it in terms of defending against threats: we’ve navigated environmental catastrophes before, and in time, I think we’ll pull it off again. But I didn’t expect that a good chunk of the US might just like the warmer weather better? There are more profound things I could say here, but I’ll leave you with this: despite everything bad about climate change, the weather may end up okay. We just might be frogs in a hot tub.
Elsewhere:
Thanks for reading!
Please share your thoughts and let me know where I mess up:
I suspect biodegradation actually ruins much of the emissions math: microbes eat organic matter, and if you’re lucky, they spit out CO₂. If you’re less lucky (or in a landfill), they’ll spit out some methane. It doesn’t take much methane (20-80x worse than CO₂) to dominate the carbon footprint and wash out the benefit of any CO₂ the biomaterial may have sequestered on the front end. If you’re deeper into biodegradation emissions, please shoot me a note!
Caveats! 1) The error bars on the projections are much larger than they are for the previous few decades – partly inherent unknowability of the future, partly climate uncertainty; 2) Climate change is felt mostly in extremes, not averages; 3) US ≠ world; 4) People have vastly different weather preferences; I don’t think skiers will be very happy with most these outcomes; 5) This isn’t to say today’s systems (e.g. agriculture) won’t break down; 6) Probably a million other things.
Super thought provoking article. Seems pretty disastrous the extent to which reusable bags are handed out for free as virtuous swag. Makes me wonder what a similar analysis would show for reusable water bottles vs plastic - I could see the case for greater average re-use of those vs bags, but perhaps a higher “equivalence threshold” between impacts of reusable vs single use bottles washes out any advantage
Hey Michael just making a note that there are some complaints about how this Danish study created/reported their models of cotton bag impact. For a summary see here from Leo Barasi: https://twitter.com/leobarasi/status/1569410910078357505 . The TLDR is that the impact of cotton used in the study relies on some arguable assumptions; with large sources of uncertainty. Modeling is hard! If we all paired our conclusions alongside metrics of our certainty in these conclusions, the world would perhaps be a different place.