Ninety percent of micro plastics generation comes from laundry fibers. Fortunately, standard primary, plus secondary wastewater treatment removes 88-94 percent of this, lowering laundry’s total contribution to 25 percent. This can be further reduced by advanced wastewater treatment.
Of all the things humans can do to keep plastics out of our environment, the upgrading of sewage treatment systems around the country would likely provide the biggest bang for the buck. The technology exists, but wastewater treatment is sorely underfunded because it is invisible and unglamorous. (Are there any wastewater plants named after local philanthropists?) Additional plastic comes from spills and personal care products (scrubbing beads, which the US banned from off-the-shelf products in 2015). The remaining 60 percent of the plastic comes from run-off, including litter, automobile tires, and a surprising amount from worn highway markings and marine coatings.
Bottom line: Reduce consumption. Help fund or participate in plastic cleanup projects.
A LOCAL SURVEY
To get a closer look at this problem, tech editor Drew Frye went on a plastic hunt along the shores of Chesapeake Bay.
Composition. He spent several afternoons collecting plastic from Chesapeake Bay beaches. He also reviewed data collect from beaches worldwide. As expected, there were no chlorinated plastics present, because PVC sinks.
Most of the plastic were also well on their way to becoming micro-plastics, crumbling and cracking. They would have no value for recycling, since the polymer is too degraded to be useful. This is also why the plastic from many or most beach and ocean cleanup projects goes to waste-to-energy plants. If you made sweaters or bags from this plastic, they would fall apart.
Here’s what we found:
Plastic Type Collected (by weight)
| HDPE | 64 percent |
|---|---|
| PET | 19 percent |
| Urethane | 6 percent |
| PP | 5 percent |
| EVA | 4 percent |
| Nylon | 1 percent |
| Styrene | 1 percent |
THE INCINERATION OPTION
We followed a forum conversation that posed the question, “If I’m on an island beach, with no recycling available, am I better off leaving the trash or burning it in my campfire? Which is worse, the pollution from burning, or the microplastics it will become?” This also relates to the waste-to-energy recycling of plastics.
Of course, many chimed in that you should recycle the plastic. Yes, you can take it home with you. You could take it to recycling bins on the island… if there are any. You could put it in the trash. But don’t presume that those containers are recycled or dumped at a well-managed landfill.
Most islands don’t have landfill space. They either burn their waste or dump it in the sea. Frye watched the recycle containers on several Chesapeake Bay islands taken to the waste disposal facility, where they were burned in an open pile. They don’t have a landfill, or the money to fuel the incinerator or haul the waste to shore.
It appears that the recycle bins exist just to make the tourists feel good. When the tourists leave in the evening, the recycle containers go to the burn pile. Seeing this, we wondered if a portable incinerator might be the answer to our polluted plastic island scenario.
AIR POLLUTANTS
We’ve long been told that burning plastic was horrible, creating a toxic soup of air pollutants. But recognizing that beach plastics do not include chlorinated plastics, nearly all of the studies are inapplicable.
We found one EPA study done for the US Army that concluded there was no point in separating PET drink bottles from paper and waste in burn piles, because they burned cleaner than paper under those conditions. Most of the toxic pollution and nearly all of the polychlorinated dioxins come from burning PVC (pipe, vinyl, blister packs), which does not exist in beach plastic.
PVC contains 56-70% chlorine. For comparison, driftwood is variable, between 0.5-1.2% chlorine. (We tested some driftwood samples—the dry stuff, high on the beach, had the least amount of chlorine.) Coal can be as high as 0.2-0.3 percent chlorine. Our beach plastic contained about 1.4 percent chlorine, not much different from driftwood! Since the plastic was dried and cleaned, most of that came from wet sand inside the bottles.
Based on our research, pollutant and polychlorinated dioxin production when properly burning beach plastic is not significantly different from burning driftwood.
Ash. We found it took four hours to accumulate enough ash that removal was needed; most simple stoves are just designed to be dumped upside down. A common complaint is that plastic does not burn completely, leaving ugly lumps on the beach.
However, when burned in a rocket stove (see adjacent article) our collected plastic burned with just 0.26 percent ash, much less than the 2-3 percent typical of beach firewood. The ash from several kitchen garbage bags full of plastic barely filled our palm. A campfire, on the other hand, does not burn as completely, leaving coals and lumps of melted plastic.
Rocket stoves come in many forms, but they all operate the same way. They create turbulent air mixing in the combustion area, resulting in more efficient wood burning. They can be built from mud, masonry, or metal duct work. They can be insulated for high efficiency, or made of light metal for easy folding and portability.
Rocket stoves burn smoke-free, tolerate a strong breeze, and they burn far less fuel. They leave practically no ash or unburned residue. And because they run on small pieces of wood, they are ready for cooking in just a few minutes. A pot rack is usually integrated—you’ll need a pot skirt if it is windy (see page 8).
We built ours from 5 feet of 4-inch steel duct, about 6 feet of 2-foot wide aluminum flashing, and several pounds of perlite for insulation. A section of grill cut from a cookie cooling rack made a cooking surface.
Cobbled together from scraps, this Frankenstein stove is surprisingly efficient. It lights and comes up to temperature in 3-5 minutes, and just a hand full of twigs will boil 2 quarts of water in 8-10 minutes. There is no smoke, little smell, and the heat output is easily regulated.
We think a folding version could be a great addition to your beach cookout gear. Here are two websites, among many, that cover DIY designs:
• Good beach design that could be built without welding (www.instructables. com/Camping-Rocket-Stove/)
• Several more plans, to give you some ideas. www.morningchores. com/rocket-stove-plans/
To light, shove one scrap of burning paper into the combustion chamber to start the draft, followed by a mix of paper, twigs, and bigger stuff in the feed tube, being careful not to block the draft. For a cooking fire, feed three long broom stick-sized pieces into the feed tube, moving forward as need to regulate the fire. That’s all the wood you’ll need, even if you intend to burn plastic.
Draft can be controlled by a door on a separate air inlet, or by how fuel is placed in the feed tube. If there is smoke, increase the air. If flames come out the top, reduce the fueling rate.
Burning plastic can generate black smoke. This is not because of chemicals in the plastic, but rather because plastic is very energy- dense, like oil, and when thrown in an open fire the oxygen mixing is just not good enough. Oil or wax can do the same thing.
Eventually we learned that if we fed 1-2 wood sticks to maintain a steady burn, we could then feed a steady stream of plastic chips, some every few minutes, and bottles and maintain a steady, smoke-free burn. At this rate it took four hours to consume two kitchen bags of plastic.
During the burn we monitored temperatures in the combustion zone with an IR thermometer and found the ranged from 600-1100C, averaging about 800C. For comparison, open bonfires are about 400-550 C and steel starts to glow a dull red at about 480 C. As stated above, 800 C for 2 seconds is the minimum temperature to effectively destroy all smoke and dioxins.
Not a perfect incinerator. Feed is slow and attention is required to keep the fire in the optimum range, but it is far cleaner and more efficient than a campfire.
• If burned with sufficient oxygen, polyurethane is not that different from wood and paper. https://polyurethane. americanchemistry.com/Smoke-and- Toxicity.pdf
• The EPA studied burning PET bottles by the US Army. Although other plastics can be harmful, the conclusion was that inclusion of PET bottles probably reduced burn pit emissions. https:// pubmed.ncbi.nlm.nih.gov/22947082/
Important note: The above is ONLY for beach plastic containing primarily polyethylene terephthalate (PET) and polyethylene (HDPE and LDPE) and no chlorinated plastics. PVC cannot be burned cleanly.
