Bitcoin and other cryptocurrencies are dangerous for climate change because they require massive amounts of electricity, and our grid is still supplied primarily by fossil fuels. Credit: David McBee, Pexels.

Dear EarthTalk: How is it that bitcoin, a virtual currency that few of us have heard of and no one I know uses, is becoming a major contributor to carbon emissions? – Troy Sussman, Bowie, MD

It’s hard to believe that bitcoin, the best known of a group of new “cryptocurrencies” that many believe to be the future of money, could be the final nail in the coffin causing irreversible climate change. But a recent study from University of Hawai’i at Manoa researchers found that “projected bitcoin usage, if it follows the rate of adoption of other broadly adopted technologies, could alone produce enough carbon dioxide (CO2) emissions to push warming above 2°C within less than three decades.” According to the Intergovernmental Panel on Climate Change (IPCC), we can only hope to avoid the most cataclysmic effects of global warming if we can limit the rise in average global temperature to 2°C.

The reason bitcoin and other cryptocurrencies generate so much CO2 is that they require massive amounts of electricity, and our grid is still supplied primarily by fossil fuels. Bitcoin transactions are recorded and processed by dispersed individuals known as “miners” who group them together in blocks and add them to larger “chains” which serve as public ledgers of transactions.

“The verification process by miners, who compete to decipher a computationally demanding proof-of-work in exchange for bitcoins, requires large amounts of electricity,” reports study co-author Randi Rollins. Rollins estimates that bitcoin transactions accounted for some 69 million metric tons of CO2 emission in 2017 alone — and expects bitcoin-related emissions to rise sharply in the near future as the payment technology is adopted by millions around the world. If society adopts bitcoin as quickly as it adopted previous wildly popular “technologies” (e.g. credit cards, dishwashers), increased electricity demands could overwhelm efforts to curtail greenhouse gas emissions.

“We cannot predict the future of Bitcoin, but if implemented at a rate even close to the slowest pace at which other technologies have been incorporated, it will spell very bad news for climate change and the people and species impacted by it,” says the study’s lead author Camilo Mora.

“With the ever-growing devastation created by hazardous climate conditions, humanity is coming to terms with the fact that climate change is as real and personal as it can be,” she adds. “Clearly, any further development of cryptocurrencies should critically aim to reduce electricity demand, if the potentially devastating consequences of 2°C of global warming are to be avoided.”

Critics of the report counter that the global electric power sector — not to mention computers and cryptocurrency “rigs” — are getting significantly more energy efficient every year. Also, bitcoin and other cryptocurrencies might not be as widely adopted as researchers assume. But isn’t it better we know now about the potential climate risks of bitcoin so we can work to direct the technology’s development in as environmentally friendly a way as possible? It certainly would be a shame to suffer the effects of runaway climate change after doing so much to lower our carbon footprints just because we neglected to hold cryptocurrencies to the same efficiency standards as the rest of the technologies we rely on.

Contacts: Bitcoin, bitcoin.org; “Bitcoin emissions alone could push global warming above 2°C,” Nature Climate Change, https://www.nature.com/articles/s41558-018-0321-8.


Even though greener options are widely available, 80 percent of dry cleaners still use potentially toxic “perc” to clean fabrics. Credit: Jeremy Brooks, FlickrCC.
Dear EarthTalk: Is so-called eco-friendly dry cleaning a reality? – Jane Krause, Garden City, NJ

Although some greener alternatives exist, most dry cleaners still use perchloroethylene (“perc” for short), a petroleum-based solvent that can be hazardous to the human central nervous system, with exposure causing headaches, nausea, dizziness and memory problems for some people.

Perc’s constituent components — phosgene, vinyl chloride, carbon tetrachloride and trichloroacetic acid (TCA) — have also been linked to a range of other health issues, including liver and kidney malfunction, reproductive abnormalities and even cancer. The U.S. Environmental Protection Agency (EPA) regulates perc under the Toxic Substances Control Act, the Clean Water Act and the Safe Drinking Water Act.

Luckily for consumers, safer alternatives to perc for dry cleaning are available. The most common comes from a company called GreenEarth Cleaning, whose products and process form the backbone of a large network of independent “green” dry cleaners across the United States. GreenEarth’s process uses biodegradable liquid silicone — essentially liquified sand — in place of petrochemicals. Since liquid silicone is chemically inert, it doesn’t chemically react with fabric fibers, and is safe to use on delicate garments — beads, lace, silk, cashmere — and won’t cause shrinkage.

And perhaps best of all, it breaks down into natural elements (sand, water and carbon dioxide) that are safe for air, water, soil and people. In fact, liquid silicone is so safe that it is often a base ingredient in many everyday shampoos, conditioners and lotions that we put right onto our skin with no ill effects.

From its humble beginnings in a lab back in 1998, GreenEarth’s system is now used by some 6,000 dry cleaners globally. You can find one near you via a zip code search on the company’s website.

Another green alternative to dry cleaning is so-called professional wet cleaning, whereby fabric is laundered in a computer-controlled washer and dryer that uses water along with specialized soaps and conditioners instead of solvent–and spins its contents much more slowly than a typical home washing machine. The result is that it’s much gentler on fragile clothing.

Yet another eco-friendly choice is liquid carbon dioxide (CO2) cleaning, which uses pressurized CO2 in combination with other gentle cleaning agents to dissolve dirt, fats and oils in clothing instead of perc.

One often-overlooked option is simply to hand-wash delicate clothes and fabrics in Woolite or some other non-toxic detergent, and then hang them to dry. If you need your hand-washed clothes to have a finished pressed look, you can take them to a standard cleaner for pressing only.

Despite the existence of greener alternatives, four out of five dry cleaners still use perc. Consumers should beware of dry cleaners that advertise their process as organic, given that perc can be considered organic because its petroleum-based chemicals do come out of the ground. If you aren’t sure about that neighborhood dry cleaner, ask them a few questions to find out what makes them consider themselves green. Just because they might recycle hangers or plastic bags doesn’t get them off the hook as polluters if they use perc or other hazardous substances or processes.

Contacts: GreenEarth, www.greenearthcleaning.com; EPA’s “Outdoor Air – Industry, Business, and Home: Dry Cleaning Operations,” archive.epa.gov/airquality/community/web/html/drycleaning.html.


Greener carpet is made from wool, jute or cotton and emits little if any VOCs. Credit: Dominika Gregu?ová, Pexels.
Dear EarthTalk: I need to replace the wall-to-wall carpeting in my basement. Any tips for finding something new that won’t aggravate my allergies or otherwise pollute my indoor air? — Jasper Manheim, Los Angeles, CA

Carpeting is an oft-overlooked culprit when it comes to compromised indoor air quality, but the chemicals used to produce it are typically far from natural. According to the non-profit Environmental Working Group (EWG), most carpeting is made from synthetic fibers derived from non-renewable petroleum-based sources and emits harmful volatile organic compounds (VOCs) into the air.

Meanwhile, carpet backing is typically made from synthetic rubber derived from styrene and butadiene, also respiratory irritants. And that new carpet smell we know so well comes from the off-gassing of 4-PCH, a potent VOC byproduct of the synthetic rubber manufacturing process known to cause respiratory problems, eye irritation and rashes. EWG adds that it can also react with other chemicals to produce formaldehyde, a known human carcinogen.

Likewise, the glues and sealants used to install most wall-to-wall carpeting come chock full of more VOCs and in some cases, toxic petroleum-based solvents. To add insult to injury, the waterproofing and anti-microbial treatments now common in everyday carpeting have been linked to cancer, birth defects and hormone disruption. Last but not least, carpet padding is typically made from scraps of polyurethane recycled from older furniture and mattresses — and, as such, likely contains carcinogenic chemical flame retardants now banned in new furniture.

Well, that’s all well and good, but what choices do we have? Actually, lots. Carpeting labeled with the Carpet & Rug Institute’s “Green Label Plus” or UL Environment’s “Greenguard” emits low amounts of VOCs and as such is safer for you and your family. Wool is the most common eco-friendly choice, but jute and cotton varieties are coming on strong. Stay away from stain fighting, waterproofing or antimicrobial treatments. For carpet padding, go with felt rather than synthetic rubber. And make sure to use low-emitting, non-solvent adhesives and/or fasteners during installation.

No matter what kind of carpeting you end up with, make sure to vacuum it regularly — the American Lung Association recommends at least 3x/week with a HEPA filter-equipped vacuum — to remove dust, allergens and pollutants that you (or your pets) might track in. “Carpets are…the perfect environment to harbor dust mites, mold and mildew, which are all common allergens,” reports EWG.

One way to avoid all of these issues entirely is to forego carpeting altogether and go with tile, wood, cork or natural linoleum flooring with low-VOC sealant. They don’t off-gas VOCs or harbor allergens and pollutants, and they’re easy to clean while lasting decades longer than carpeting anyway. Throw down a few wool area rugs (easily cleaned outside) and you’ll be good — and green — to go.

Now what to do with the old carpeting is another question entirely. Carpeting is difficult to recycle as it’s made from multiple components with different chemical makeups, so your local curbside recycling hauler is unlikely to take it away for you. The non-profit Carpet America Recovery Effort (CARE) is working to develop the infrastructure needed to recycle carpet efficiently across the U.S. In the meantime, you can search on Earth911 for a carpet recycler near you.

Contacts: EWG, www.ewg.org; Green Label Plus, carpet-rug.org/testing/green-label-plus; Greenguard, greenguard.org; CARE, carpetrecovery.org; Earth911, search.earth911.com.

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