I don’t see a lot of methodology in that summary. I’ve seen a lot of assessments of paper usage that neglect to consider the fact that integrated pulp and paper mills can be net producers of energy at times. The part of the wood that doesn’t make it into paper is burned in recovery boilers to make steam and drive turbines. If you simply consider gross energy usage and don’t offset it with the renewable energy produced on site the numbers look bad. Here’s a paper describing the use of biomass in the pulp industry which gets 50% of its energy from biomass fuel. The carbon dioxide generated from biomass is carbon neutral and should not be considered a greenhouse gas.
I linked to the full paper a few posts back and would be interested in your thoughts on the methodology. I’ll give it a more thorough read myself.
Short answer to OP: yes.
Long answer: Usually, yes, technically, but it may not outweigh emissions from production of methane. And never producing the paper towel results in the same carbon being stored as wood anyway.
I work in the landfill gas and greenhouse gas sector and can tell you that there are a lot of variables involved in determining whether landfilling a paper towel results in more emissions or more sequestration. I’m talking mostly about US landfills, which may be the most regulated in the world. (For good reason – just look at a list of Superfund sites and you’ll see that many are landfill or dump sites.)
First, to address the sequestration issue: it’s not long term, like fossil fuels, but it’s not short term either. The sequestration is probably for more than 100 years, which is more or less the agreed upon standard for calling something sequestration. (If you think this standard is ridiculous, I suggest you take it up with the forestry industry, who claim sequestration for wood sequestered in wood products such as furniture and building materials, as well as growth of forests.) If you’re in a dry region, you can probably pull readable newspapers out of a 100 year old landfill, so it’s clear that not all that carbon is being converted to landfill gas. Even when the old landfill is used for greenspace or other redevelopment, most jurisdictions will not allow the landfill cap to be removed, thus preventing significant air intrusion. Actually, air intrusion would be a benefit from a greenhouse gas perspective because the methanogenic microbes are anaerobic. In an aerobic environment, the waste degrades into CO2 and not nearly as much methane.
There’s the obvious exception of waste incineration than snfaulkner points out, but at least those emissions are not anthropogenic .
Back to landfills. Have some fun playing with the EPA’s Waste Reduction Model: (https://www3.epa.gov/warm/). It allows you to estimate emissions from the end of life phase of waste, including being able to vary things like whether the landfill doesn’t have gas recovery (worse case) to whether it has gas recovery for energy (best case). Assuming the paper is mixed residential paper, the methane emissions exceed the carbon sequestration on the national average, but not at facilities with landfill gas to energy.
I’m deliberately not looking at lifecycle emissions so far, but those should be considered as well. Source reduction is a very good way to reduce emissions. If you’re using a hot air dryer rather than a paper towel, that paper towel doesn’t get produced, no energy is required to process the wood pulp, and the tree stays standing, reducing emissions significantly. Compare the emissions of the mixed paper to the same quantity of source reduced paper, and you’ll see that source reduction has much lower emissions. That’s because the tree is never harvested and 100% of the carbon remains sequestered there.
Take that page with a massive dose of salt. The “peaks at about 20 years” line is absolutely arbitrary. The 6 month delay is correct (enough), but gas production typically peaks the year after a landfill closes. Gas generation is a first order decay process for the carbon in the waste. As carbon accumulates (i.e. more waste is placed) there is more carbon to decay. Recently placed waste has essentially been experiencing that decay process for a shorter period and has more carbon to emit, but the old waste will continue to add to gas generation. Unless waste placement significantly declines in the last several years of a landfill’s life, the peak gas generation will be when it has the most waste but that waste has not decayed for long.
If you’re interested in seeing gas generation curves, you can play with the EPA’s LandGEM model. (https://www3.epa.gov/ttn/catc/products.html#software)
While WARM and LandGEM are not perfect models and I may have quibbles for specific applications, they’re solid enough to provide an understanding of the fundamentals.
The WARM model documentation provides some references. See the references under Landfilling and Landfill Carbon Storage here: (https://www3.epa.gov/epawaste/conserve/tools/warm/SWMGHGreport.html)
Hooker Chemical, thank you for the informative posts on landfill GHG emissions. I’ll have a look at your cites. I do, however, have a number of pertinent comments.
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[li]I stated at the beginning that the short answer to the OP is “no”. Your statement in #23 that the short answer to the OP is “yes” is unfounded and could only be justified by the dual assumptions that (a) more carbon is contained in the paper towel than was emitted in its total production and transportation lifecycle, and (b) sufficiently long sequestering capabilities of landfills. Both of those have to be true, and from previous cites it appears that (a) is clearly false, and (b) is at best highly dubious.[/li][/ul]
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[li]You didn’t actually refute the Wikipedia numbers I quoted for landfill emissions except to say the “peak at 20 years” is an arbitrary assessment, which indeed it may be. But the mere fact that significant emissions do occur weakens any such argument even further, aside from the fact that paper towels appear to be a net source of carbon from the production lifecycle even if perfectly sequestered forever. But beyond the silly paper towel thing, the landfill question is an interesting one, which leads me to this …[/li][/ul]
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[li]You cited the forestry industry for claiming that 100 years is the “agreed-upon standard” for sequestration. But what the forestry industry likes to claim is not relevant. What is relevant are the achievable emissions reductions relative to the IPCC’s Representative Concentration Pathway models that show us the climate impacts of different emissions scenarios over time. IOW, 100-year sequestration (assuming it was total and was achievable) might be just the salvation that we need, or it might be totally useless, depending entirely on the degree of political will and technological deployment possible to curtail emissions and keep temperature rise contained to the necessary limits. And it seems to me that even if we could reduce net industrial emissions to zero in 100 years, which is very unlikely, the last thing we would want even then is for CH4 and CO2 to come bubbling out of the ground and start the driving up GHGs once again.[/li][/ul]
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[li]For the record, your quote in #25 wasn’t from me.[/li][/ul]
I’m not looking at (a) in a lifecycle sense for purposes of the short answer. The OP asks if paper towels are a form of carbon sequestration, and in the strict sense, they are. Carbon in the towel ends up stored in the landfill. As I go on to point out, the amount of carbon there does not necessarily outweigh the carbon emitted in production or carbon equivalent from anaerobic decomposition. I certainly don’t suggest it for the long term benefit of our climate.
There have been some good studies with the long term stability of carbon in landfills related to issue (b). Carbon storage depends on the material type. If you look at the Barlaz studies in the WARM documentation, you can see that newsprint has one of the highest storage factors for long term storage, which I suspect contributes to the stories of pulling readable newspapers from landfills. I suspect paper towels to be at the lower end of that storage factor, but that’s speculation.
Some amount of carbon will be stored for the long term. Some plant structures don’t break down well, such as lignin, cellulose, and hemi-cellulose. The landfill doesn’t change that. Eventually, the methanogens die out and the landfill becomes a “dry tomb.” The dry tomb effect is important if the land is ever going to be repurposed because without the waste is unstable until it reaches the dry tomb stage. Creating the dry tomb and a stable landfill is the reason they get thick clay caps or membrane covers.
I’m not seeking to refute anything specific about the Wikipedia cite other than the 20 year issue. It’s something that was quoted that sent up a red flag as I read it because it’s typically wrong and may signal greater issues with the article. Still, the core concept that methane and CO2 are generated from waste in anaerobic conditions is correct.
Reading through the article, it’s not bad. The article should be clearer that it’s talking about sanitary landfills, which are the standard practice in the US and elsewhere. Other create the anaerobic environment as effectively and gas generation is lower for it. It’s also amusing to see that Waste Management’s marketing materials made it into the article. They’re hardly the only people recovering gas for energy but you wouldn’t know that from the article.
It’s not the forestry industry that came up with the 100 year threshold, but it’s become practice to use the 100 year global warming potential and forestry is happy to follow along. Obviously, trees won’t sequester carbon forever, but they’re what most people think about when they think of sequestration. I believe that the 100 year sequestration period is partially driven by that GWP period as well. The 100 year storage threshold is also part of California’s forestry offset protocol for its Cap and Trade program.
My sincere apologies. I butchered the tags and misattributed the quote.