Is Boise’s composting good for the environment? Do I really pay before I get a cart?

A thorough analysis on the environmental impact of municipal composting programs doesn’t appear to exist.

Catherine Chertudi said she isn’t aware of such a study. Chertudi is the city of Boise’s solid waste programs manager and the city’s point person for a curbside composting program, which is getting started now. So she probably knows more than anyone in the Treasure Valley, maybe all of Idaho, about municipal composting and research that’s been done on the subject.

As Boise rolls out its program after more than a year of planning, complaints about it just won’t die. The most common criticism is cost. Most single-family residents will pay an extra $3.40 per month.

But some have questioned whether the program will actually yield the environmental benefit the city claims. Partly, this is because of the carts where people will throw their yard debris, food scraps and other compostables.

There’s no figure available for the total mass of plastic that went into building the 70,000 carts. Chertudi said they’re made of at least 30 percent post-consumer recycled plastic and are 100 percent recyclable.

Still, there’s no doubt that building the carts required a considerable investment of resources and produced a sizable amount of carbon and other emissions. Then there’s the emissions produced from transporting the carts from Arizona, where they were manufactured, to Boise and later to the homes that will use them.

So what’s the end result? Do the program’s environmental benefits outweigh the costs of getting it started?

That’s impossible to calculate because there are so many variables we can only guess at.

For example, will the carts — or the program — last long enough to justify that big upfront investment? Chertudi said each cart is guaranteed for 10 years, and similar garbage carts are known to last as long as 15 years. How many years before the program crosses over into beneficial territory?

The big variable in finding that threshold is the amount of stuff people throw in their compost carts instead of the trash. The city’s conservative projection is 95 tons per day to start, or about 27.5 percent of the garbage stream. That’s an educated guess, but it’s still just a guess.

Also, what is the environmental benefit of composting all of that stuff instead of dumping it in the landfill? Done right, composting actually increases carbon emissions. But in doing so, it reduces methane emissions produced when garbage rots in a landfill. As a trapper of environmental heat, methane is dozens of times more potent than carbon dioxide, though it doesn’t linger in the atmosphere as long as carbon does. Again though, there’s no solid number for just how much less methane Boise’s garbage will produce once the composting program gets rolling, because that calculation would rely on unproven variables, such as the total volume of trash diverted from the Ada County Landfill.

It’s important to remember that environment is only one reason for the city’s decision to start a composting program. Cost is the other big factor. An analysis of Boise’s total waste stream in 2014 found that more than 45 percent of all trash picked up from single family homes was compostable.

If a composting program kept just half of that compostable material out of the landfill, it would greatly extend the life of the landfill. That would delay the huge expense of siting, permitting and building a new one — a cost borne by taxpayers across Ada County.

Have more questions? Here are some answers:

Q: How much is this going to cost me?

Most households will pay an extra $3.40 per month, or $6.80 per bi-monthly billing cycle, for the new service. But many different pricing levels are in play, depending on the number and sizes of trash, recycling and composting carts customers order.

See the box below for a complete list of rates.

Q: Who has to pay?

Residents of any home inside Boise city limits that now use Republic Services’ plastic carts for garbage and recycling. Mostly, that’s single-family homes, but it includes duplexes and small apartment buildings with as many as seven units.

Businesses are part of the program for now.

Q: When do the new fees kick in?

June 1.

Q: When does composting service begin?

As soon as your cart arrives. Republic will pick up materials from the composting carts once a week on the same day as trash pickup.

See an interactive map here showing when homes in your neighborhood will get their carts.

Q: So the city will start charging me for composting before I get my cart?

Yes, if your cart arrives later than mid-June.

Q: What can I put in the composting cart?

Mainly, food scraps and yard debris. Here’s the full list from the city’s website: leaves and branches, grass clippings, fruits and vegetables, yard and garden cleanup, coffee grounds and filters, tea bags, eggshells, pine cones and needles.

No meat or dairy. Also, no poop of any kind.

The composting carts’ lids will have images stamped on them to remind people of what’s allowed and what isn’t.

Q: Can I use the compost?

Yes, if you’re a Boise resident. After about 100 days, composted materials should be mature and usable as an additive to yards and gardens. At that point, the city will package some percentage — maybe half — of the final product to sell to businesses that deal in garden and farm products.

The rest would be for city residents and use on ground owned by the city government. Boise plans to dispense the compost for free from three or four sites scattered around the city.

Q: Where else has this been done?

Thousands of composting programs are in place in cities, counties and neighborhoods across the United States, though citywide, curbside composting programs like the one Boise is starting are somewhat rare. Boise’s program is the first of its kind in Idaho.

This story was originally published June 6, 2017 at 11:56 AM with the headline "Is Boise’s composting good for the environment? Do I really pay before I get a cart?."