The blog formerly known as   Fake Plastic Fish

November 25, 2008

Contest Answer – BioBags okay for compost only.

A week ago, I showed this photo from the SF Green Festival and asked what was wrong with this picture. No one offered the specific answer I was looking for, but many gave great partial attempts.

Ken O. noticed that all the bin liners are biodegradable, and he’s right. In fact, they are all corn-based BioBags. Lara S. gave an excellent answer, “the plastic bags are unnecessary and shouldn’t be there (compostable or not… it’s a waste).” If these bins were at our homes, most of us could do without any liners at all. Michael and I don’t use any kind of garbage bags at our house these days… compostable or not.

But for a big 3-day event where there is quite a bit of solid waste (despite being a zero-waste event!) it’s more practical to swap out some kind of liner than to move many, many bins around.

So here’s what happened: these green BioBags were the first thing I noticed when I entered the convention hall. A green BioBag in each bin. And of course, my assumption was that the BioBag would travel with whatever it contained: a BioBag to the compost facility, a BioBag to the recycler, and a BioBag to the landfill. And my biggest concern was that BioBags should not go to the landfill.

Now, this opinion is the exact reverse of what I thought over a year ago when I first started Fake Plastic Fish. In fact, I argued vociferously that BioBags were better than re-used plastic grocery bags for garbage. My reasoning was that since BioBags are made from a renewable resource, it’s less harmful to landfill them (since we can grow more corn) than to landfill plastic bags which are made from non-renewable fossil fuels.

Of course, I now understand that in anaerobic landfill conditions, bio-based bags will break down and create methane gas, which is a far more powerful greenhouse gas than CO2. BioBags are not benign in the landfill, as I thought, but probably worse than plastic bags. (Not to mention the fossil fuels used to grow that “renewable” corn.)

So, back to Green Festival. Before checking out any of the booths; before finding any of my friends; before getting food (I was starving), I set out to find out who was in charge of this mess and set them straight. I was as self-righteous two weeks ago about BioBags not being landfilled as I was over a year ago that they should be!

And when I did find the culprits out back, I was happily put in my place.

A whole team was out there removing the contents from the green BioBags, sorting it into huge containers, then reusing the BioBags if possible or putting them in with the compost. In fact, when I asked the guy in charge about the bags, he seemed as aghast as I was at the thought of landfilling them. “Oh, no!” he said, “They’re worse in the landfill than plastic bags!” And, of course, the bags would not be sent to the recycling center to clog up the sorting machines either.

I’ve grown to love being wrong. I love how this blog constantly gives me a chance to show my ignorance. I love the feedback from you guys and the “Aha!” moments I have (as Oprah would say) when I realize I’ve been up to my self-righteous act again. It’s how I learn… not just environmental information but where my own blind spots are. Man, I have a lot of them.

So maybe there is no right answer about landfills and plastic bags and garbage. The best solution I know of is to reduce our waste as much as possible so we don’t have to make these kinds of choices in the first place. To me, even thought they’re not going to the landfill, it’s sad to see so many brand new bags used for a weekend and composted. We’re moving towards zero waste, but we have a long way to go. Still, it’s a fallible imperfect perfect world, with each of us doing our best, getting better only as quickly as we can.

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Cindia Kalo

Problems also arise when rubbish in wheelie bins is not contained as the ‘tip and shake’ process of emptying the wheelie bins into the truck results in loose items blowing out and littering the streets, causing more environmental problems. Smaller, lightweight items really do need to be contained in a wrapped newspaper or bin liner bags.


While I think there some elements of truth to your thesis..I have to suggest that a little knowledge is dangerous. BioBag’s in an aerobic environment will degrade. SOme m ethane like all living plants, humans, squirrels, etc..give off methane gas as part of natural decomposition. Methane is a relatively potent greenhouse gas with a high global warming potential of 72 (averaged over 20 years) or 25 (averaged over 100 years).[1] Methane in the atmosphere is eventually oxidized, producing carbon dioxide and water. As a result, methane in the atmosphere has a half life of seven years. The abundance of methane… Read more »


This is great to know, as I have been really pushing BioBags on the family lately. We use our to line our small compost bin, which then we empty into a larger bin in our apartment complex, and then Sunset Scavenger picks it up for SF’s city-sponsored compost program.

Amaya 5

As Yogi Berra once said “What gets us into trouble is not what we don’t know, It’s what we know for sure that just ain’t so.”

Beth Terry

Condo Blues — are you allowed to use grocery bags instead of actual trash bags? Maybe, since you don’t have any grocery bags yourself (because you are so conscientious about bringing reusable bags shopping) you could ask your less conscientious friends for their used plastic bags or put an ad on Freecycle for them. Just a thought. There are also garbage bags made from recycled plastic. Like I said, there’s no perfect answer here. Fortunately in Oakland, we are not required to bag our garbage, so we don’t use any bags at all. And really, the only garbage we have… Read more »

Condo Blues

OK, Now I’m confused and think I’m screwed either way I go. My city requires that I bag my trash. If I use a regular trash bag it won’t biodegrade in the bandfill. Now I find that if I use a biobag it give off methane in the landfill. We don’t generate much trash at all approx a small grocery bag of trash every 2 weeks or more (I’m using this as for size purposes only, I have reusable grocery store bags.) so what’s the better choice? Paper bags aren’t an option BTW.

Beth Terry

Hi Juli. I’m not an expert, but I do know that in a properly maintained compost pile, oxygen will be part of the mix, so aerobic decomposition will take place. Most modern landfills, on other hand, are sealed off from the air, so anaerobic decomposition occurs instead.

Here’s a page that compares both aerobic and anaerobic composting methods. The reference to “noxious gases” in the anaerobic section includes methane.

Indeed, in my first attempt with the compost tumbler, I didn’t tumble it enough and I got some noxious smelling greenhouse gases!


Hi Beth,

I am still confused about anaerobic vs. aerobic decomposition. Would a decomposing bio-bag not produce methane gas in a compost bin?


Hi Beth –
I have to say that in our area, the Monterey Peninsula – I am of the opinion that the compostable bags are great for our landfill. We have a forward-thinking operation at our local MRWMD landfill that is lined with pipes that collect the methane generated by decomposing items and powers the whole facility as well as selling the electricity back to the grid! Wish all dumps were so classy!


I sell prints of my paintings. In the past, when one was sold, it was rolled in newsprint and the roll was pasted together with scraps of Japanese paper. But a hot-shot sales rep advised me to upgrade the packaging to a more professional look so I mounted the prints on acid-free board and put them in clear bags like the kind that come with hand-made greeting cards. Once I found Fake Plastic Fish, my plastic-conscience bothered me until recently when my supplier for the bags,, started using biodegradable plastic bags hooray! I’ll now include an advisory on how… Read more »


My question about the use of biodegradable bags has always been why the putrefying products inside them (animal waste, veggies if you’re not composting, whatever) wouldn’t, you know, be merrily putrefying and releasing methane within the bags, just as they would within non-biodegradable bags. It’s not like the bio bags were just going to fall apart the minute they hit the landfill.

Of course, I was looking for an excuse to justify my continued use of (mostly scavenged) supermarket bags for the trash can.

Bryan Bell

Getting rid of garbage in a responsible way is an evolving science. We do this for a living and are always adjusting the materials we use to transport waste.


Beth, thanks for straightening out me too. I was so convinced that bio bags were the answer but now I know better. Thank goodness for the intelligence of the person in charge of the trash at your green fest.

Lara S.

Wow you’re right, it hadn’t occurred to me that methane would be produced. I too love being wrong. It’s the best way to learn, though I tend to be stubborn sometimes… Here in Argentina compostable plastics are not available at all. Walmart used to give away “compostable bags” (the ones made of petrol but which break down faster)… I think they stopped, though. I think that kind of plastic should only be used for things in which there can’t be a reusable alternative. Maybe some medical supplies could be made of it. Hope you feel well soon! Remember to eat… Read more »

Green Bean

Sweet. Love being wrong in those kinds of situtations. :)

Beth Terry

Viv — these particular bags are green and say “BioBag” on them.

knutty knitter

I’ve not ever seen biodegradable bags – how do you tell?

viv in nz