In the eco-mommy-blogosphere, one topic is most polarizing: diapers. The cloth and disposable camps come armed with decades of research into why any choice other than theirs is terrible for the planet. And no wonder: The average child wears around 4,000 diapers in its first two and a half years. Add in an aging population, and diapers are a $65-billion-dollar industry globally.

So who’s got it right? With impacts including carbon emissions, water usage, toxic chemicals, industrial waste, and disposal, this is a complex issue with no simple answers. Here’s the science you need to cut through the stench:

Cloth diaper revival

As more people become alarmed by the garbage crisis, cloth diapers have made a comeback. But they’re generally made of cotton, and even organic cotton production uses massive amounts of water. Manufacturing one kilogram of cotton fabric — roughly equivalent to 24 prefold diapers — requires 10,000 litres of water. (Prefolds are fabric pads used with waterproof diaper covers.)

Water consumption and carbon emissions from laundering are another major impact of cloth diapers. (More on this below.) Many cloth varieties can be used with disposable inserts, which reduce the cleaning required, but add to overall diaper waste. Some companies claim their inserts are flushable, but they’re not suitable for most sewage systems. Given that flushed wet wipes have caused the formation of giant “fatbergs” in sewers — the largest so far reportedly weighs 400 metric tonnes — it’s easy to imagine the damage flushed diaper liners could do.

One-child’s-worth of cotton diapers consumes between 48,000 and 126,000 litres of water.

From manufacture to disposal, one-child’s-worth of cotton diapers consumes between 48,000 and 126,000 litres of water. Disposables use less, but the amount is still substantial: between 35,000 and 75,000 litres per child. Alternatives to cotton like bamboo or hemp could prove more friendly to our climate and water supply, but more research is needed, according to a diaper life-cycle analysis led by Australian environmental engineer Kate O’Brien.

Disposable dilemma

Disposable diapers are typically made from absorbent softwood pulp and petroleum-derived polymers, lined with plastic and bound with glue. They dominate the market because they’re convenient. But the adhesives responsible for “ultra leak protection” come with ecological costs: they’re heavily processed fossil fuels. The additional plastics associated with packaging add up too, as do emissions from transportation.

Responding to consumer concern over waste, both the disposable and reusable diaper industries commissioned studies comparing them. According to one study backed by Procter & Gamble — a big player in the disposable market — diapers became lighter by more than 50% between 1988 and 2010, reducing environmental impacts from raw materials and manufacturing.

The adhesives responsible for “ultra leak protection” are heavily processed fossil fuels.

Researchers have also examined whether disposable diaper materials pose a human health risk. One recent study published in Reproductive Toxicology found all four diaper brands tested contained volatile organic compounds (VOCs) linked to asthma and cancer (as did 11 menstrual pad brands). Some of these chemicals can be absorbed by the reproductive system, and are linked to issues like early-onset puberty. Meanwhile, disposables-industry-funded studies maintain the diapers are completely safe.

Going green?

Most “green” disposables are made from either unbleached materials, recycled pulp, or both. That’s good, because diaper materials are most often bleached with chlorine, polluting waterways with the carcinogen dioxin. But buyer beware: You might see ECF (Elemental Chlorine Free) among the ecolabels, which means the diapers were bleached with a harmful chlorine derivative. Look for those labeled Totally Chlorine Free (TCF), which use safer alternatives.

Other green varieties replace petrochemical plastics with bamboo and corn. These have potential to reduce impacts, but can shift the environmental burden, since they’re still water, land, and energy-intensive to produce. One Australian study found that materials for compostable diapers require 1.4 times more land to produce than regular disposables.

Just because a label says “100% recycled,” doesn’t mean the company pays workers fairly.

When it comes to disposables claiming recycled materials, check the percentage. Huggies Pure & Natural has been widely criticized for only using recycled material in its packaging (and just 20% at that). Seventh Generation fessed up to dying diapers “eco-friendly” brown. And just because a label says “100% recycled,” doesn’t mean the company pays workers fairly or minimizes pollution in its factories. Look for companies that are genuinely invested in a fair and circular economy, with certifications like Cradle to Cradle.

Regarding potentially hazardous chemicals, a recent study by the French agency for environmental health found that “green” diapers also contained harmful chemicals like dioxin, formaldehyde, and VOCs.

500 years is a long time

Diapers make up an average of 4 to 10% of our collective solid waste. By one measure, disposables amount to 10 kilograms of waste per week, compared to 0.11 kilograms for cloth diapers. And the hard truth is, every disposable diaper that ends up in the landfill will be there for a very long time: an estimated five centuries.

As Sherry Schiff, a groundwater expert at the University of Waterloo, points out in an online essay, diapers put materials that require sewage treatment into a landfill. With contaminants like E. coli bacteria in our landfills, we risk harming our water supply, or those dealing with the mess. Read the fine print on disposables or on your municipality’s website, and you’ll see the request to flush human waste down the toilet before disposing. Whether that’s a realistic expectation of consumers already opting for convenience is another question. (Though many moms vouch for a bidet-style “diaper sprayer.”)

Even biodegradable materials like softwood pulp need special conditions to break down.

But what about biodegradable varieties? It’s a moot point if they’re in the landfill, research shows, as even biodegradable materials like softwood pulp need special conditions to break down. Eventually diapers may be compostable, but more work needs to be done. If you’re lucky, you live in one of the few places that does “compost” diapers, like the City of Toronto, though the word is a simplification. Diapers are picked up curbside from green bins and processed: agitated in hot water so plastic materials separate from organic waste and pulp, which go on to compost in an anaerobic digester, using microbes. All plastics and synthetics go to the landfill.

Composting also requires land. The City of Toronto is running out of space in its landfill for waste and compost, and many alternative waste facilities aren’t equipped to handle human waste. Nor is curbside diaper pickup cheap.

The verdict

“Cloth nappies washed in cold water in full loads and line-dried have the lowest environmental impact,” O’Brien explained over email. But if you’re not going this route, the overall impacts of cloth and disposables come out even, though each system makes its impacts in different ways.

The good news with cloth diapering is caregivers have more control over their environmental impact. Cloth diapers’ biggest resource-draws are the water and energy used in production and washing. Tumble drying cloth diapers boosts their contributions to global warming by 43%. Renewable energy and efficient washing machines can tip the scale further for cloth diapers. Bonus points if they’re used on more than one child. For disposables, the only substantive way to reduce their impact is to use fewer, O’Brien points out. (Google “elimination communication,” and brace yourself for the mommy blogosphere).

Cloth nappies washed in cold water in full loads and line-dried have the lowest environmental impact.

Those daunted by cold-water washing and hang-drying can focus on mitigating the environmental impacts that concern them most. If you care about water usage, use a front-loading machine for cloth diapers, or opt for disposables that use less water in their manufacture (bamboo holds a lot of potential). If it’s toxic chemicals in our landfills and water supply, look for cloth diapers certified for meeting the Global Organic Textile Standard (GOTS), which addresses both environmental and labour issues. Or choose disposable varieties that say “unbleached,” “chlorine-free,” or “glueless.”

Concerned about carbon emissions? Wash cloth diapers with cold or solar-heated water and hang dry. And don’t use commercial diaper services: the transportation emissions can cancel out the benefits. If the sheer volume of resources and waste weigh you down, go cloth or get creative in using fewer diapers.

Considering green disposable alternatives add significant cost to a necessity many already struggle to cover, it’s important to note the science says not to stress too much. Your energy may be better spent demanding local government invest in diverting organic waste from landfills, and supporting energy-efficient homes. “Nappies are visible, and the debate is loud,” says O’Brien. “As if this is the only environmental impact of a new human on the planet.”