Tag Archives: carbon dioxide

A Stinky Subject

This isn’t about sex, murder, war, politics, or Donald Trump, so if that’s all that interests you, you may as well stop reading now.  It’s about landfill gas recapture and utilization, a subject that makes my engineering friends yawn but fascinates me.

It links my interests in environmental toxins, garbage disposal, and multi-purpose innovation to address commonly acknowledged problems.  While the political scientists debate whether the Earth is undergoing “climate change” and, if so, whether humankind is causing it, I’m looking at litter in the streets; noting the extraordinary growth of plastic and single use packaging; and throwing away heaps of junk mail in post office recycling bins.  At least the PO has recycling bins, a forward shift in consciousness, according to me, within the past ten years.  Not only does the post office subsidize this mountain of murdered trees by reduced rates, but my various alma maters and professional organizations are the worst perpetrators of this global plot to deforest the planet and speed up the global warming agenda.  One would think the ivory-tower elitists would be the first to rail against this glut of self-serving propaganda, but alas, they can’t afford to support their tenured positions and building campaigns with mere tuitions.  They must perpetually dun their graduates—and their graduates’ offspring—for money, if only to prove how cost-ineffective and eco-unfriendly they are.

So, rather than spend money supporting those who can’t support themselves, I choose to educate myself without cost in ways to reduce all my problems and the world’s problems at the same time.  A tall order, perhaps, and maybe a futile one, considering the stinky subject of landfill.  Nobody wants to touch it, unless, of course they can get government funding.

To get government funding, one is obliged to package the idea in terms that make the government look good.  For instance, did you know the United States has 2000 regulated landfills, the most in the world?  By 2006, the US generated 413 million tons of municipal solid waste, and 64% went into landfill.  70 percent of this was composed of food, paper, and corrugated cardboard, and 15 percent was of petrochemicals, mostly plastic.

Biogas, including carbon dioxide and methane, are emitted from decomposition of organic materials in landfill.  Aerobic decomposition of waste generally leads to the production of carbon dioxide (CO2), and anaerobic decomposition produces methane (CH4). Methane is also known as natural gas. MSW (municipal solid waste) landfill gas is comprised of 45-60% methane and 40-60% CO2.

Methane is believed to be at least 24 times more potent than carbon dioxide in its global warming effects.  About 50 million tons of methane are generated annually by municipal solid waste, but only 5 million tons are captured.

Landfills generate a maximum of methane at five years, then the amount begins to decline.  Landfill gas utilization is a process by which methane is captured and used to generate electricity or heat, or upgraded for inclusion in commercial natural gas products.  In 2006, there were 325 landfills in the US that collected biogas, up from 231 in 1999.  California had the most:  65 landfill gas facilities, followed by Illinois, Michigan, New York, and Pennsylvania.  In 2001, there were 955 landfills that recovered biogas, with the most in the United States, followed by Germany and the United Kingdom.  In the United Kingdom, the number of facilities went from 329 in 2005 to 519 in 2009.

There are two methods for capture of methane from landfill, closed and open capture.  Closed capture refers to gas extraction from landfills that have been closed and can be capped.  It is considered more efficient than capture from open landfills, at 84% and 67% respectively.  Methods for capture including drilling wells either vertically or horizontally.  Equipment needed for utilization depends on the size of the landfill.  Smaller facilities can employ reciprocating engines; medium-sized facilities can use turbines; and steam cycles are used for the largest deposits.

General Motors has significantly reduced its energy costs by using landfill gas to power some of its production facilities.  As of August, 2016, the General Motors Orion plant in the Orion Township of Michigan boasted that landfill gas was supplying 54% of its electricity.  The gas comes from two open landfills nearby, owned by Waste Management and Republic Services, respectively.  The GM plant also has a 350 kW solar array.

There are incentives from the Treasury Department, Department of Energy, the Agriculture Department, and the Department of Commerce for landfill gas extraction.  Landfill gas is considered a renewable form of energy.  The US EPA operates a landfill Methane Outreach Program.

Opponents of landfill gas utilization include such organizations as the Energy Justice Network, which claims that landfill gas has contaminants that are either inherently toxic or combine into toxic substances when burned.  Although “non-methane organic compounds” (NMOCs) comprise less than one percent of landfill gas, there are also non-organic toxic substances, such as mercury and tritium, in minute amounts.  Also, when halogens–like chlorine, fluorine, and bromine– are combusted with hydrocarbons, they can produce dioxins and furans, some of the most toxic substances known.  While other sources state that a burning temperature of 850 degrees centigrade can destroy dioxins, Energy Justice Network claims these can be re-formed in the cooling process.

At the same time, Energy Justice Network admits that methane is responsible for 10.6 percent of global warming from US human sources, with 35.8 percent of this from landfill gas.  It also claims that if landfill gas is to be utilized for energy, boilers offer the safest mode, with turbines, then internal combustion engines less desirable.