New frontiers and costs of recycling

By Catherine
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Written by Catherine Bolgar

open dumpster full of trash

Are we recycling all we could? Organic waste, such as food scraps and yard trimmings, accounts for between a quarter and a third of the solid waste generated in cities—the largest single municipal waste stream, according to Eric A. Goldstein, waste expert at the Natural Resources Defense Council in New York.

If you had to identify one key area of growth for recycling, it would be organics,” he says.

Organic waste in landfills becomes mummified or decomposes anaerobically (i.e. without oxygen), producing methane, a greenhouse gas whose impact on climate change is estimated to be 25 times greater than that of carbon dioxide.

Composted organic waste though becomes a natural fertilizer that helps soil retain moisture and hold carbon. A University of California Berkeley study found that a single application of compost led to a metric ton of carbon capture and storage per hectare annually, for three years.

However, “composting if done well isn’t cheap,” says Glenda Gies, principal of Glenda Gies & Associates Inc., an Ontario-based recycling consultancy. “It requires the right temperature, moisture levels and bacteria populations.”

There’s also the question of who’s responsible for the recycling. With plastic or electronics products, the brand is usually identifiable, even on discarded goods. The manufacturer may then be legally required to recycle them. But by the time organics become waste it’s no longer clear who the brand owner is, and recovery costs then pass to the municipality, consumer or business, “who have been reluctant to pay,” Ms. Gies says.

This hasn’t deterred some city and state authorities from taking a lead. San Francisco has introduced mandatory separate collection of compostable materials, which applies to all residences and businesses, says Kevin Drew, residential and special projects zero-waste coordinator at the city’s department of environment. Massachusetts banned food waste disposal by companies in 2014, sending organics to 49 processors.

Once there, organic waste is processed into methane through digesters (like at sewage treatment plants). And unlike landfills where the methane escapes, the digesters trap it and convert it into natural gas, while the residue is turned into compost. San Francisco and its service provider are building digesters, with the resulting gas used to fuel collection and transfer vehicles, Mr. Drew says.

There’s complete recovery of the energy and compost value in the waste,” he says. “I would argue that this program will be coming to every city in the world.”

colored clothingOther materials also have strong recycling potential. Only 15% of used clothes, towels, bedding and other textiles in the U.S. is donated or recycled, according to the Council for Textile Recycling, with the rest ending up in landfills. In the U.K., about 40% of clothing is re-used or recycled. But more can be done.

“There’s an enormous amount of textiles that are recoverable as clothing,” says Mr. Drew. “There are markets around the world that will take that material. We’re on a quest to recover more textiles.

Cost is key. With traditional recycling streams, such as paper, plastics and glass, changes in technology and commodity prices affect the willingness to recycle.

“Companies want to recycle to save money,” says John Daniel, president of Federal International Inc., a St. Louis recycling firm. “In general, companies will increase recycling to the point where it costs them money, and then they stop.”

Recycling bin with glassConsider glass recycling. When collected along with other waste materials, broken glass has to be sifted out at sorting facilities. This may have been worth doing when glass prices were high, but today, “at many facilities, it’s not cost effective to separate out that glass. A significant amount of glass put in recycling doesn’t get recycled,” he says.

Similarly, “when the price of oil was much higher, carpet was able to be recycled,” he notes. “Now it is almost impossible to recycle without the cost being higher than landfilling. The cost of recovering, transporting and processing the material is significantly higher than the value of the material.”

Virgin products may seem cheaper, Ms. Gies says. But if one were to factor in environmental costs—reflected in, say, greenhouse-gas taxes or obligations on manufacturers to recycle returned products—the resulting higher price might be more realistic, and potentially uncompetitive.

“The industry naturally will recover all material demand, provided it is cost effective,” Mr. Daniel explains. “As the price goes up, then recyclers have the ability to dive in deeper and start recovering higher-cost material. The best way to increase recycling rates is to improve the demand for products made from recycled materials. Our industry will take care of filling the supply.”

 

Catherine Bolgar is a former managing editor of The Wall Street Journal Europe. For more from Catherine Bolgar, contributors from the Economist Intelligence Unit along with industry experts, join the Future Realities discussion on LinkedIn.

Photos courtesy of iStock

Sewers paved with gold

By Catherine
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Written by Catherine Bolgar

The future gold rush might be to a sewer near you. Municipal sewage contains many metals, including gold, silver and platinum. Concentrations vary by metal, but municipal sewage tends to contain about one part per million of gold. This “isn’t a lot, but for gold it’s significant,” says Kathleen Smith, research geologist at the U.S. Geological Survey, and an expert on metals in biosolids.

Biosolids (treated sewage sludge) are more commonly understood as fertilizer. “It’s high in phosphorus and slow-release nitrogen,” Dr. Smith says. Around half the roughly seven million dry tonnes of biosolids collected at U.S. wastewater treatment plants is recycled as fertilizer, including in public lands and forests.

But while copper and zinc, for example, are essential for plants and animals, these metals may become toxic in high concentrations, hence the need to monitor and regulate the chemical and metal content in waste.

It’s not just the regulated metals such as copper and zinc that now attract attention. “The presence of some valuable metals—such as gold, silver, platinum, and palladium—is [also] of interest, due to their concentration levels,” Dr. Smith says.

In the mining industry, sought-after metals are dispersed. “You have to spend a lot of money and move a lot of rock to get at the metals,” Dr. Smith explains. Recovering metals from sludge, however, is easier. It also complements traditional mining and can be undertaken in any market.

From a sustainability point of view, we’re…trying to find a way to extract metals from [waste streams] that contain large amounts of metals, versus just throwing them in a landfill and dealing with the effects of having the metals dispersed in the environment,” Dr. Smith says.

There’s also money to be made. Arizona State University researchers calculate that a million-strong community produces $13 million worth of metals in biosolids annually. The most lucrative elements—silver, copper, gold, phosphorus, iron, palladium, manganese, zinc, iridium, aluminum, cadmium, titanium, gallium and chromium—have an estimated combined value of $280 per ton ($308 per tonne) of sewage.

A 1978 analysis of incinerated sludge in Palo Alto, California found 30 parts per million of gold and 660 parts per million of silver in the city’s annual ash pile, worth some $2.5 million; since then the gold price alone has risen six-fold.

Knowing the total concentrations of metals in the biosolids is just the first step,” Dr. Smith notes.  The challenge is to release and recover the metals in the correct form to interest the market. “It’s not as easy as multiplying the concentration of the metals by their market value.”

Scientists at the Swiss Federal Institute of Technology Zurich, for example, are working on a thermal-chemical process to decontaminate sludge, remove harmful heavy metals, and retain the phosphorus as fertilizer.

Meanwhile, JBR Recovery Ltd., in West Bromwich, U.K., has developed a commercially-viable method to recover silver and other precious metals from industrial sludge. Simon Meddings, JBR’s managing director, explains the process. First, a rotary kiln uses combustible silver-bearing waste to dry out most of the moisture. A high-carbon ash is produced—increasing the volume of metals to 10% to 15% from around 0.2%—and placed into a lead-based blast furnace. The lead collects the precious metals, and slag is dispersed through a tap hole at the front of the furnace. The alloy of lead and precious metals then goes into a cupellation furnace, which oxidizes the lead, allowing it to be poured off the top. The remaining bath of molten metal—around 98% pure silver with gold and other platinum group metals present—is cast into bars. These go into moebius cells where an electrical current refines the silver to 99.9%, and collects and refines the gold and platinum separately.

Sludge suppliers are paid according to how much precious metal is extracted and sold, less treatment and refining charges. The photographic industry and chemical production plants are major customers (photographs and x-rays in particular having high metals content).

Nonetheless, many large companies overlook their waste streams, and simply contract waste management companies to dispose of their sludge.

You’d be surprised how much ends up in landfill,” Mr. Meddings says. “People are not aware of the value in it.” They might take more interest “if they know they can get a financial rebate.”

 

Catherine Bolgar is a former managing editor of The Wall Street Journal Europe. For more from Catherine Bolgar, contributors from the Economist Intelligence Unit along with industry experts, join the Future Realities discussion.

Photos courtesy of iStock