Ghana's best shot at going green: sewage power

With solar and wind power costly and inadequate, Ghanaians are turning to some very alternative sources of energy – like human waste.

How might the world's poorest continent go green? Kwabena Otu-Danquah's job is to crack that riddle. The renewable energy czar for Ghana ranks among the handful of bureaucrats across Africa tasked with picking which forms of green energy might prove affordable on a continent where most people don't pay for the electricity they sometimes receive.

Last year the Ghanaian Parliament signed a pledge to derive 10 percent of the country's electricity from alternative sources come 2020. Mr. Otu-Danquah is still trying to figure out which alternatives.

Sun? Forget it. Solar costs 40 to 50 cents a kilowatt-hour, while Ghanaians pay just 5 to 10 cents for electricity from conventional sources. Wind? Too slow. Breeze ambles through this tropical doldrum at a leisurely average of five kilometers an hour (3.2 miles per hour). How about jatropha, a local flower Goldman Sachs pitched as the next fad biofuel? Ghana tried that. As growers mowed down farms to plant nuts for fuel, drought-battered countries to Ghana's north complained of food price spikes in some of the world's hungriest villages.

That's forced Ghana to consider a more imaginative set of choices. Among them, sewage. Flush with a $1.5 million grant from the Bill & Melinda Gates Foundation, local Waste Enterprisers Ltd. is building Ghana's first "fecal sludge-fed biodiesel plant." That's longhand for cooking human excrement into generator fuel, chief operating officer Tim Wade explains. The transformation would serve a dual purpose. Open sewers sweep 1,000 tons of slurry each day into the ocean off Accra, spewing an ocean-top brown slick that is visible on Google Earth. Outside the upland city of Kumasi, roughly 100 trucks dump tens of thousands of liters of septic tank sewage daily into what used to be a small pond.

Luckily, nobody bothers to treat that slop. Sewage treatment plants, as far as Mr. Wade is concerned, fritter away the good stuff. If all goes according to plan, next month one truck a day from Kumasi will dump its payload into a warm and massive vat that will skim lipids – fat – off the top. “That's your biodeisel,” he explains.

At $7 a gallon, he can sell the muck to local mining companies, who are keen to buy because they, too, have been required by Parliament to power 10 percent of their private electric plants from green sources. Normal diesel does sell for a few bucks cheaper, he admits, “But we're still optimizing the process.” If he can get costs down, Wade intends to build four plants in Accra and lecture subdivisions back home in Colorado on the folly of treating their waste.

Alternatives to the alternatives

There are more sanitary ways to make a megawatt in this country. Kwame Tufor came home from Florida to liquefy Ghana's coconut husks, cocoa pods, and palm nut shells into gas. But you'd need a lot of coconuts to turn a profit that way. So he and a business partner are eyeing an old paper farm the size of Brooklyn. Sometime between one 1970s coup and another, the owner ran out of money and political favor, abandoning acres of trees that were meant to be mulched into notepads 35 years ago.

Mr. Tufor intends to saw those trees down, replant them, then burn the timber and compress the smoke into a biofuel using dated World War II technology that's been dusted off by developing world power plants. At least 10 plants in China now gasify coal this way. Farmers in the Philippines run irrigation pumps on generators that gasify rice husks. If Tufor's $200 million project pans out, local farmers would also sell him their nutshells and cocoa pods for his incinerator.

Odder sources of energy are under review. They include leftovers. Ghana's trash, it seems, boasts curiously high food content – edibles account for 60 percent of this country's rubbish, according to senior researcher Robert Adu at England's De Montfort University, Leicester. He's finishing a technical proposal on how to goose a charge out of Ghana's garbage. One thing Ghana's got going for it: Locals love rice. One kilogram of the staple grain, Mr. Adu says, packs 17 kilojoules, a flicker compared with a kilo of kerosene, but great compared with a vegetable.

Subsidizing trash

Ghana's government offers a subsidy for companies that can produce renewable energy at a cost closer to the African pay scale. For Adu, that means it might just be profitable to feed tons of rotten groceries every day into a fire that would boil a tank of water whose steam would lurch a turbine forward. The trouble? How to cull the grub from the garbage. Trash separation schemes do exist; Adu says he's reading a book on them. He points to a plant in Germany that's mastered the technique through a process made profitable by sales of hot air, a byproduct, to heat homes in wintertime. If Adu goes that route, he'll have to find buyers looking to purchase hot air in the tropics.

Otu-Danquah isn't quite sure how this burst of invention will wind up: At the day's end, economics on what Ghanaians and their government can afford will surely dash some dreams. But the proposals make for more interesting reading, he says, than the stack of hackneyed solar plant schemes he's stuffed into a corner. Plus, some big break just might occur.

“When the time comes,” he says. “we will have learned our lessons and developed our own technology.” At the very least, he adds, Accra might enjoy cleaner streets and cleaner sewers.