“New innovation from scientists,” read the subject line from my Mom’s email. Attached was a link to a Youtube clip of a male scientist balling plastic bags, sealing them in a steel vessel, and pushing a button. After a couple of hours, the eager scientist cracked open the vessel, and poured out a dark, ominous looking fluid. “People don’t know that garbage can be made into gasoline” the scientist beamed. Apparently after some refining, this scientist had converted plastic bags into gasoline.
My response was immediate: “Don’t go investing your money just yet. Plastic bags are a by-product of gasoline production. It would take a lot of energy to turn plastic bags back into gasoline, probably more energy than you would make.” I had put the thought out of my head, until one day when I was breezing through a fashion magazine (yes, some scientists read those too) and there was a short article about another woman who was also claiming she could turn plastic bags into gasoline. The idea was obviously gaining momentum. Could my opinion on trash-to-gas be jaded?
Is our energy future bright?
There have been some serious endeavors in this “trash-to-gas” vein of research. In 2009, a major Houston-based garbage collecting company funded a large scale venture to convert garbage into fuel.1 More recently, the US Army invested $3 million in a Sacramento-based gasification project.2 The US Army claims this type of technology could meet their fuel needs over-seas, far from a fill-up station.
*While I focus on plasma gasification in this post, there are many different trash to gas technologies. For example, collecting volatile methane from farm waste is a commonly utilized trash-to-gas technology.
The trash-to-gas technology of the US Army is plasma gasification.* Sounds like something out of Back to the Future, doesn’t it? Most simply put, waste is heated to hell (1500 ˚C- 5000 ˚C), breaking every piece of trash down to its bare molecules. The upper limit of this heat range is just a dial below the temperature of the Sun (5600 ˚C). When you heat anything to that blazing temperature, you put an extreme amount of energy in it, breaking all of the bonds until just the small molecules are left. So, with enough scorching heat, you can obliterate all trash, whether its plastic bags, medical syringes, or hazardous waste, into CO, CO2, H2, CH4, and H2O.** These simple molecules can then be combusted in a power plant for energy.
**For the combustion savvy reader curious of the fate of metals, those leave the system as a small, manageable amount of slag.
And for those who are ever the skeptic (such as myself), how much energy does it takes to burn this trash at 1500 ˚C- 5000 ˚C? This energy intensive heating consumes 1200-1500 MJ/ton of trash, which means it requires about 20-40% of the energy that the process creates. This doesn’t sound so bad–the trash-to-gas conversion requires energy, but it still produces a positive energy output.
Unfortunately, there is an added complication.
“One problem: waste streams are very inconsistent,” says Dawn Santoianni, founder of the energy technology communication company, Tau Technical, “And if the waste streams are too wet or too dry, it takes too much energy to make energy.” In other words, and ideal power plants will have a consistent volume of trash, with a consistent dryness to it. And the composition of trash varies. Perhaps the trash is mostly dried Christmas trees in January, and mostly damp IC Light mango bottles in July. Maybe more trash is made the day after Christmas than on a random Tuesday. In order to keep the trash-to-gas plants purring like a kitten, the trash must be sorted, it must be dried, it must be processed, all before heading to the big torch. Add this additional trash processing, and suddenly your trash-to-gas energy output becomes close to a wash.
The unpredictability of waste stream content and volume sends investors back to coal to fill their energy portfolios. Thus, many of the trash-to-gas entrepreneurs rely heavily on government incentives.
As for the original idea of turning plastic bags into gasoline, “That seems highly unlikely,” says Santoianni. In addition to the energy lost during the sorting, drying, and combustion of the average trash-to-gas plant, additional energy would be needed to convert those small molecules back into gasoline. So while trash-to-power-plants would have a small but positive net energy output, trash-to-gasoline would have a negative net energy output.
Is our waste management future dim?
While the small energy output makes trash-to-gas technologies seem like a lost cause, this technology has a saving grace. For zero energy input, trash-to-gas can essentially make all your garbage disappear.
For those who have seen the film Idiocracy, a comedy about a dystopian future in which houses are built on toppling piles of trash, this technology is a beacon of hope. Plasma gasification (and other trash-to-gas technologies) can transform any piece of carbon into energy. This is enticing, especially when you consider plastic bottles and plastic bags can remain in the environment for hundreds to thousands of years.3 In 2012, 32 million tons of plastic were dumped in our nation’s landfills,4 and that volume is not shrinking. Trash-to-gas may eke out a small percentage of energy, but it could be a solution for much of our waste despairs.
This is a solution that many European countries have long understood. Despite the small amount of energy gasification promises, many European companies are seriously considering implementing this technology. So why has America not partaken in this promising waste management technology?
The reason is simple: America has plenty of land, Europe has much less land. In other words, America has the land for cheap dumps, while smaller European countries are forced to ration landfill space. In Europe, waste management is costly, so they must get innovative.
“It essentially comes down to economics,” says Santoianni. “A lot of brilliant waste-to-energy [ideas] are technically feasible, but not economically feasible.” It’s difficult to convince US regulators to force energy suppliers to buy the pricier but greener trash-to-gas option. And it’s equally difficult to convince US waste management companies to pony up the capital investment for trash-to-gas technology, when they can pull a larger profit by using cheap landfill space. Thus, the trash-to-gas technology may not be economically realistic in America until we raise the cost of landfilling.
Unfortunately, tossing trash into a car for fuel remains the optimistic fiction of Robert Zemeckis. But developing trash-to-gas technology gives us an ‘ace-in–the-hole’ solution to a dystopian future where everyone lives atop a giant, ever growing expanse of waste. And that’s a comforting thought.