Plasma Gasification: A Solution to the Waste Disposal Dilemma?
Waste not, Want not?
The source of this proverb is unknown, but I’m going to hazard a guess and say it wasn’t your average (modern) American. I say this because your average American runs through 56 tons of trash a year – including 500 plastic cups and 650 pounds of paper. If we were to start lining up all the garbage trucks that Americans fill in two years they would stretch from the earth to the moon! New York City alone produces enough trash each day to fill the Empire State Building.
Not only is the trash somewhat unsightly, it represents a problem from a climate perspective. The incineration and decomposition of solid waste (as occurs in landfills) produces greenhouse gases and threatens environmental stability.
A new technology called plasma gasification has the potential to “eat up” all this trash, leaving only energy and valuable materials (and producing no greenhouse gas emissions to boot). Too good to be true? Taiwan, Japan, England, and Canada don’t think so; they already have the technology up and running.
Where are we currently putting all of our municipal solid waste (technical for trash) if not in plasma plants? Well, the EPA calculated in 2005 that 32.1% of our waste is recovered by recycling procedures. However, this number does not include hazardous, industrial or construction waste – if it did, sources say the figure would be closer to 10%. The remaining 90% ends up either in landfills or incinerators.
Landfills (and their ugly cousins, dumps) are locations where trash is stored on and within a natural landscape. While dump are usually just holes in the ground where trash is buried, landfills use sophisticated methods of compacting, isolating, and maintaining trash deposits to maximize land use and minimize ecological damage. Landfill sites are carefully evaluated for their suitability (the composition of the underlying bedrock is a major concern) and must be meticulously sustained (for example, most landfills require a fresh, six inch covering of soil everyday). About 70% of US municipal waste ends up in landfills.
Despite careful planning and maintenance, landfills still emit large quantities of greenhouse gases. The anaerobic decomposition of solid waste releases methane and carbon dioxide roughly in equal parts. Landfills have consistently been the greatest man-made source of methane emissions over the past ten years (and second only to enteric fermentation). Although much of the methane can be reclaimed and put to use as a renewable, green energy source, and despite EPA encouragement, this has yet to be done on any large scale in the US.
Incinerators use combustion to reduce waste into ash, gas, and heat in a volume proportion of about nine to one. Incineration can handle types of waste deemed too dangerous to store in landfills, including biological and medical refuse. However, the (often toxic) ash produced by incineration and other thermal techniques must be landfilled as well, and in addition to emitting greenhouse gases, other emissions (such as dioxins) pose health and environmental risks. The Global Alliance for Incinerator Alternatives (GAIA), an international alliance of like-minded grassroot groups, points out that incinerators are usually located in poor and rural areas with little political influence – a violation of environmental justice.
New York City relies on a combination of incinerators and landfills to dispose of the daily 36,000 tons of trash generated. The majority of this total is contracted out to private industries – only 12,000 tons is handled by the Department of Sanitation. Since the closing of the Fresh Kills Landfill (a large landfill in Staten Island) in 2002, all the municipal waste now ends up in out-of-state locations, specifically in New Jersey, Pennsylvania, Virginia, Ohio, and South Carolina. Private contracts and transport costs carry a hefty price tag: $90 per ton of waste, a far cry from the average $35 that other states pay.
Work done by the Roosevelt Institution, a student-run think tank, here at Columbia highlights a new technology that appears to solve many – in particular New York City’s – waste disposal problems.
Plasma arc gasification is the next generation of thermal treatment techniques. By running a high voltage current through a pressurized, inert gas, tremendously high temperatures can be induced (up to 30,000 degree Fahrenheit – three times as hot as the surface of the sun) in an arc of plasma. This arc is capable of obliterating any type of waste – excluding some very rare, high-energy nuclear wastes – and converting them into elementary gases and an obsidian-like slag material. This process is highly exothermic so there is a surplus of energy produced; once the arc is initiated it “pays” for itself and then some.
The emissions from gasification, dubbed syngas, can be converted on-site into hydrogen and other valuable gases for sale. Startech, a leading developer of gasification technology, maintains that the combined sales of the power surplus and hydrogen production would allow plants to profit $15 from each ton of waste processed. This could help mitigate the $1.25 billion currently spent annually on the collection and disposal of the City’s trash (up from $658 million in 2000).
Plasma gasification plants already exist in Taiwan, Japan, Canada, and England and there are plans for additional facilities. There are two contracts in place for plants in Florida and another is being considered for Los Angeles.
A plant that processes 2,000 tons of waste a day, roughly what a city of one million inhabitants produces daily, costs $250 million to construct. This can be prohibitively expensive for municipalities (particularly one as strapped as New York City’s) but, as Angela Wong and co-authors for the Roosevelt Institution note, in ten years of operation time the City would be able to make up for the cost of construction.
I contacted Joseph Longo, the charismatic CEO of Startech (also the inventor of the trash compactor), to ask what obstacles remain in the way of plasma gasification’s widespread acceptance. I hinted at the powerful waste disposal lobby and high construction overhead but he thought the issue was more general than that.
He wondered why any environmentally “enlightened” country would rely on incineration and trash dumps. Papua New Guinea doesn’t use them; what do they know that we don’t? Fortunately, things are changing, he says, albeit slowly. In the meantime, we’ll have to stick to proverbs.