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Do-it-yourself Gold Recovery, Biofuel From Coffee Cups

by Marc S. Reisch
August 23, 2010 | A version of this story appeared in Volume 88, Issue 34


Golden Computers:
Credit: Shutterstock
Recycling beats electrochemistry.
Credit: Shutterstock
Recycling beats electrochemistry.

I recently spent a weekend helping my son ready a few shipments of retired cell phones and computers to send to electronics recycling centers. Some of those old electronics still have some street value, and others have parts that can be reused. If our efforts pan out, we’ll make a few hundred bucks.

Never mind that the original purchase price for these items probably totaled a few thousand dollars. We’re doing the right thing by keeping the stuff, including the heavy metals contained in them, out of a landfill. However, had we been a bit more enterprising, we could instead have mined our collection for gold, which is now selling for well over $1,000 per ounce.

All those jumper pins, processor slots, and various connectors are plated with a few micrometers of gold. And it’s not fool’s gold—iron pyrite—but the genuine element, used because of its excellent thermal and electrical conductivity and resistance to oxidation. Tom’s Hardware, an Internet-based publication, points out that the computer industry uses several hundred tons of the metal every year.

In fact, Tom’s recently published an excellent primer by Yannick Guerrini on how modern-day ’49ers can EXTRACT REAL GOLD from the dross of outdated electronics (‑gold-motherboard-chemistry.html). And don’t worry, Tom’s does warn would-be gold diggers not to attempt such a recovery effort at home—at least not without heavy gloves, proper ventilation, and adult supervision.

Suffice it to say, Guerrini’s instructions depend on electrochemistry and require a battery charger big enough to crank the engine on my Dodge Caravan. His directions also require the use of sulfuric acid, hydrochloric acid, sodium hypochlorite, and sodium metabisulfite. In the end, Guerrini explains how to use an oxy-butane torch to fuse the gold powder extracted from a pile of old electronic components into a little gold ball.

At current prices, though, that shiny bauble is “worth two or three dollars,” Guerrini admits. So until I’m granted the Midas touch, I’ll stick with recycling.

My fervor for recycling is also shared by two overcaffeinated microbiologists at the University of Manitoba who were inspired to come up with a way to transmute DISCARDED COFFEE CUPS into biofuels.

Tim Hortons Cups:
Credit: Tim Hortons
Fueling patrons even when empty.
Credit: Tim Hortons
Fueling patrons even when empty.

“We see a lot of cups being thrown away,” Richard Sparling told Canadian Broadcasting Corp. Online News in a story that appeared on July 5. And because the cups were just being trashed, Sparling and colleague David Levin decided to try a little biological alchemy. The cups “would make excellent food for the bacteria that we use to make biofuels, such as ethanol or even hydrogen,” Sparling said.

So, “on a whim,” Sparling and Levin started their project in 2009 and have since been collecting discarded drink containers from bins set up outside Tim Hortons outlets on the Manitoba campus.

So far, the scientists say, they can generate about 1.3 L of ethanol from 100 coffee cups with a “designer” bacterial brew modeled on Clostridium thermocellum and C. termitidis, which is taken from the gut of an African termite. The bacteria, the scientists have found, seem to prefer the Tim Hortons cups to those of other brands, such as Starbucks.

“It’s not that they don’t like the Starbucks cups; it just takes them a little bit longer to break them down,” Levin said. He suggested the difference was in the paper used to make the drink containers. Newscripts, however, wonders whether higher caffeine residue in one brand’s cup over another could make all the difference.


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