Composting is a reallygreenthing to do, right? I’ve always thought so since my Grandfather taught me to do it in the early sixties. Large-scale composting is getting to be quite the rage.
TheCity of San Franciscoattracted a great deal of attention with it’s mandatory food scrap recycling program and lots of localwineriesare bragging about their use of that compost to fertilize their vineyards.
I just read today about how theLangley Parish Councilin England is setting up a village compost and “set an example to small villages as the UK strives to battle climate change.”
不幸的是,我最近了解到,他们和旧金山以及纳帕酒庄实际上可能正在促成气候变化。
Climate change science often ends up challenging things we think we know.
Inconvenience
The idea of composting is to provide plenty of moisture and oxygen so that microbes will digest the easily available organic matter and generate a great deal of metabolic heat in the process. What is left at the end is a sterilized source of more resistant organic matter that can enrich a soil.
Related Post:The Story of Our Waste
Compostingof wastes is done with very good intentions, but there is the inconvenient truth that even a very well run large-scale compost operation emits somemethane.
但如果你停下来想一想,你想要整个堆有足够的氧气(有氧条件),肯定会有一些微型场所会缺氧(厌氧条件),特别是当在这个过程的高峰期有巨大的氧气需求时。这就是甲烷产生的地方。
The Science
There are actually very few published scientific studies about greenhouse gas emissions from composts, but the two that I have been able to find show that around 2-3% of the original carbon in themanureorgreen wasteis emitted as methane (21X carbon dioxide in GHG potential) and there is also a littlenitrous oxideas well (310X carbon dioxide in GHG potential). That doesn’t sound at all bad until you do some math with the values in these publications.
The Math
If you think of it in terms of delivering a hundred pounds of nitrogen/acre (as you would for something like an organic vegetable crop) you would need to start with 8600 pounds (on a dry weight basis) ofcow manure(because there is a loss of mass and because the compost is only 1.7% nitrogen). The greenhouse gas emissions are the equivalent of 0.74 lbs CO2 per dry lb of manure. That means that the “carbon footprint” of the 100 lbs of N in compost fertilizer is 6,403 lbs CO2. That is 14.6 times as much as for synthetic urea fertilizer! It is the equivalent of burning 331 gallons of gasoline! (if you are interested you can see a moredetailed explanation).
现在怎么办呢?
When I first did these calculations I was shocked. I did them over and over to make sure I wasn’t in error. I’ve run this by a number of appropriate USDA scientists. They too were surprised, but confirmed my math. All of a sudden, compost isn’t looking like such a “green” fertilizer. I’ve tried to find out whether anyone has measured the emissions from San Francisco’s operation but haven’t had any luck.
我将在后面的帖子中讨论这个问题,但是有一些更好的选择将这些废物流作为碳中和能源。I wouldn’t worry about your back yardcompost, this is probably just an issue at a commercial scale.
Kensays
Environmental benefits or harms cannot be reduced to a single metric – even if climate change is the biggest threat we face.
堆肥将原本可能被扔进垃圾填埋场(或焚烧)的东西转化为有用的土壤有机物质。无论采取什么措施,碳都会被释放出来——正确的问题是,哪种选择能在付出这些代价的同时产生最适当的效益。
Portland Rootssays
The greenhouse gases are part of the natural cycle though, as opposed to being locked up in a toxic landfill. Maybe if we were wiser we would not only compost at the city level, but we would harness the heat and gases that it puts off for better use as well as generating electricity and fertilizer.
-Tyler
Steve Savagesays
Tyler,
完全正确。肥料和残羹剩饭作为燃料对社会更有价值,而不是有问题的肥料。This could be done with an anaerobic digester or in a fast pyrolysis system
Kensays
There’s no need for the two to be mutually exclusive – anaerobic digestion can produce compost-like materials as well as methane.
Kathrynsays
Landfills also produce massive amounts of methane. Why not harvest it like some landfills are doing.
Patricksays
Just as what Ken said, if we were to toss these same items into the trash, then it would produce the same amount of greenhouse gases, but nobody is getting use out of them. With the state of our landfills being overcrowded, anyway we can prevent things from ending up in the landfill help, whether it’s for composting or fuel as Steve suggests.
Steve Savagesays
My point isn’t that a city like SF shouldn’t to something with food scraps. Its that they should consider other options like methane digesters or pyrolysis. Some landfills also harvest the methane they generate which is a not as bad option
Chris M Balzsays
Regarding the nitrogen source, no produce farmers I ever knew use cow manure to boost nitrogen. They use it to build their soil. For nitrogen, chicken manure compost is popular.
Regarding the implied technique, power-intensive hot composting, it’s important to note that it’s not the only way to compost. Layered windrows that are never turned produce the best compost in my experience. Layered windrows may emit less greenhouse gases.
Even if there is a short-term greenhouse gas to creating compost, it may pay off well in the end in terms of that same metric. Getting more carbon into the soil, the basic premise of composting, can help poor soils such as desert soils develop positive feedback loops where they progressively capture more carbon instead of remaining barren.
最后,我认为需要牢记的基本点是,我们需要把尽可能多的碳带回土壤中。堆肥是目前最知名的一种方法。也许这篇文章能促进堆肥技术的改进。
CyranoWritersays
Steve:
GREAT post! May I have your permission to “quote” it in my Examiner.com article (I’m the Seattle Green Living Examiner)? I’m putting together an article on green living called “Now What? What to do when your efforts to be green… aren’t”. This is a great example.
另一个原因是华盛顿州的法律规定,收集雨水(技术上)是非法的。(科罗拉多州和犹他州也有类似的法律)。
Good work!
Dave Kuhns, web content writer, marketing consultant,
http://www.cyranowriter.com
http://www.examiner.com/x-17874-Seattle-Green-Living-Examiner
Richsays
Would it possible for you to do some more research and get back to us with a follow=up article, preferably with a less dramatic title and a little more science than a back-of-the-napkin calculation? Perhaps you could google “Stop Trashing the Planet” and read that first. Then look for Dr. Sally Brown’s PowerPoint “A Green House Gas Balance for Compost.” These two pieces alone might get you thinking about the carbon sequestration properties of composting and carbon-amended soil, the avoidance of landfill-generated methane (72 times more potent as a greenhouse gas, not 21 times), and life cycle analysis considerations that might help you look at composting in a more rational perspective. My apologies, I do not mean to be snide, but your argument is quite unfair, specious, and misleading to readers who would be much better served to be presented the full picture of composting and organic resource management in cyclical, not linear form.
Jeff Gagesays
Several metrics and situations have been ignored by this analysis, some of which are obvious and others that may not be. The obvious one is compost feedstocks are biogenic sources of CO2 unlike Urea. Less obvious, are that studies at UC San Diego done on emissions of Volatile Organic Compounds (VOC’s) compared leaving yard debris including grass on a lawn vs. large scale composting saw a significant reductions in VOC generation in largescale composting. Also research has shown methane is degraded before being emitted from compost pile surfaces, and nitrous oxide conversions generally happen at ambient soil temperatures, not active hot piles. I am all for Anaerobic then Aerobic controlled processing of organics, but there is no need to bash one for the other.
Danielsays
As some of the other commenters have said, anaerobic digestion solves this problem while also creating renewable energy out of the captured methane. What’s left in the AD after biogas production is complete is very high quality fertilizer, better quality than compost in fact because it has a higher concentration of nitrogen. However, only about half of the original volume in weight remains.
The gas can be burned in a turbine to produce electricity and heat, and it is not intermittent power like solar and wind.
The advantages of AD over composting are clear. These projects are economically and environmentally feasible, they just need more attention as a waste disposal and energy option for communities.
irissays
Well, the alternative to composting organic materials–landfilling–creates even MORE methane emissions because it ALL breaks down anaerobically. Plus, the breaking down of organics occurs automatically in nature… does that mean we should blame Mother?
Check outhttp://www.stoptrashingtheclimate.organdhttp://www.cool2012.comfor the science behind Zero Waste initiatives like composting.
gerard nixonsays
no one seems to get the point of source reduction! if we consumed less, there would be less waste to have to compost, landfill, burn, etc…..reduce, reuse, recycle….in that order.
John50says
Thunderbird 3: I love Firefox but it loads pages slowly. ,
Jamiesays
So this is true that compost releases some methane but your calculations are only semi accurate and the reason that they are only semi accurate is because the amount of methane released depends on the management used. Or in other words how often it is turned because if it is over turned it actually releases more methane but additionally if it is under turned it makes more methane so when it is turned more is released. If managed properly less methane is released and if you look at recent scientific journals you can find studies to support this. Therefore, your calculations do not take into account the management so they cannot possibly be entirely accurate.
Additionally though, your paper is very one sided I mean coming up with problems to compost is interesting but what is your solution? Because compost is still reducing methane and other greenhouse emissions by drastic amounts. Landfills are the number one producers of methane in the U.S.
Steve Savagesays
Jamie,
You are right that the details of the management of the compost are critical – the papers I sighted were from pretty typical compost operations. The manure one was 5 turns over 99 days. How would you rate that for quality? I’d be interested in knowing about the papers you mentioned.
我也同意,有机垃圾堆肥比填埋要好得多。如果你已经完成了所有的收集工作,那么还有两个更好的选择。厌氧消化器或快速热解系统可以利用废物中的剩余能量,这比少量的剩余氮对社会和环境更有价值。
My real argument with composting and even manure is that we are wasting good clean energy to make a problematic, pollution and greenhouse gas generating fertilizer. All nitrogen fertilizers have those potentials, but these bulky, high phosphorus, uncontrolled release fertilizers don’t have the flexibility of a synthetic fertilizer for minimizing those impacts. There are actually more natural ways to build organic matter in the soil than importing it at several tons/acre/year (continuous no-till farming with the use of cover crops)
My ideal would be to take the energy from the waste and use it to run a small-scale Haber-Bosch process to make “carbon-neutral, synthetic nitrogen”
Again, thanks for the good input.
davidsays
1) You would never apply an organic fert based on the same nutrient needs as a Chemical fert program
2) You would never apply a mature compost to fulfill a Nitrogen need. (You would apply the raw manure that has a much higher soluble N%)
3) Sending the waste to a landfill or a waste pile would be MUCH more an-aerobic, and release MUCH more CH4 into the atmosphere than even a large scale compost pile.
4) Before you dump numbers, ensure that you are not comparing apples to oranges (which in this case you are)
davidsays
读读你的回答。仅供参考,堆肥不能用作肥料。堆肥中有比营养需求更重要的东西。这是一种土壤改良剂。再一次,苹果对橘子。
Ed Scerbosays
如果不是让甲烷泄漏到大气中,而是像一些垃圾填埋场那样收集和使用呢?我确实意识到这会释放另一种温室气体二氧化碳,但至少会消耗非化石燃料能源,这是一件好事,而二氧化碳的温室效应比甲烷小得多,也是一件好事。
Lewis Michaelsays
Great article our neighborhood is currently fighting installation of a lg. commercial sludge composting facility and i would like to know how much nox gets produced during the anaerobic stages Can you help? thanks a bunch mike
Oscarsays
Such problems would not occur if composting was made on-site with capable and advanced equipment such as those manufactured byhttp://www.kollvik.com
shareefsays
What about converting the abandoned quarries into composting sites?Is it possible to fill huge urban green waste in air tight pits in the abandoned quarries?how much of methane gas will be formed inside?What about manure?can we tap this methane for cooking?
Steve Savagesays
Shareef,
Some land fills are designed to capture the methane that comes out of them. I suppose an abandoned quarry could serve that function if it wasn’t flooded. The best alternative for city food wastes and for manure is an anaerobic digester. It turns the carbon in the waste into methane for energy. The issue is that it is capital intensive and requires maintenance. As someone commented earlier, the fiber that comes out of the digester isn’t a good fertilizer, but it is a good soil amendment to build soil carbon in things like vegetable crops that can’t really be grown “no-till.”
Kaisays
Finally! When looking at options everything must be considered. Of course landfill is not an option but just because our grandfathers did it and because nature does it, it does not mean that it is the best. Anyone wanna sniff some volcane fumes? It’s from nature too.
asdfsays
I understand what you are saying. However, you are incorrect. If the waste is not composted it would entirely decompose anaerobically which is worse than if it was composted where it is only partially anaerobic and mainly aerobic.
Oliver Scheideggersays
However, if we didn’t create the waste in the first place, the waste would not decompose at all!
肖恩·帕克斯says
Sort of a mute point wouldn’t you say? There is always going to be waste the best option is to deal with it in the most effective way possible.
James Rizansays
沉默的意义?你说的是“争论点”吗?
tawnybillsays
Or dispose of it responsibly (see my post)
SwissBioFarmersays
I disagree on two key points: first, the baseline scenario for most manure is that it is being stored anaerobically in a manure pool until it either evaporates or gets brought out to the fields – in either case enormous methane emissions result that exceed those resulting from composting.
second, compost is made up of carbon which is stable for varying degrees of time, up to more than 100 years. That sequesters large amounts of CO2.
Add those two together and you end up with enormous GHG reductions from composting plus you end up with more fertile soils.
Tamara Aminsays
It’s good to note that a GWP of x21 for Methane over 100 years is on the lower end of estimates. Also, the GWP of methane changes over time (its life cycle is shorter than CO2). So the GWP of methane over 20 years is actually x56.
greghsays
现代垃圾填埋场的填埋层非常紧密,几乎没有气体能够逃逸。我的一个好朋友在当地3个垃圾填埋场从事甲烷收集系统的项目。当耗资3000万美元的项目在最后一个垃圾填埋场完成时,我们询问了这些系统的运行情况。我们惊讶地发现,在垃圾填埋场发现的甲烷仅够运行几座小型设施建筑。2022世界杯四强亚盘赔率在工程过程中,他们没有考虑到电池层的紧密排列会大大减缓气体排放过程。据我所知,商业堆肥还会产生甲烷、二氧化碳和一氧化二氮。如果人们真的想帮助地球,他们需要停止驾驶300多马力的耗油suv。每个人和他们的狗似乎都开着一辆道奇公羊在车道上。
111Dave111says
Decomposition occurs all the time, fall leaves, fallen branches, and trees.
这就是表层土壤存在的原因。
If your city is collecting yard waste, or you are,
You will, of course, ignore this alarmist.
tawnybillsays
如果将这些或任何有机废物喂给BSF幼鱼,成熟的幼鱼就会变成40%的蛋白质,30%的油和5%的溶解钙,这对于鸡、鱼和猪的食物来说是一个近乎完美的蛋白质/油比例。
This FB page explains how this could be integrated with addiction treatment or help at risk youth learn a lifetime marketable skill.
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