Landfills, like this one at Hunter’s Point, produce methane, which can be used for electricity and fuel. Photo: kqedquest.

Trash that ends up at a landfill is the ugly stepsister of hipper, cooler compostable kitchen scraps and recyclable bottles and cans. But landfill trash has more of a future than you might think. As garbage decomposes, it gives off methane. Methane, when floating around in the atmosphere, is a harmful greenhouse gas; it traps 20 times more heat than CO2. But methane’s other moniker is natural gas, and is an important energy source. Methane from landfills can be captured and used to generate power and fuel vehicles—often the very same garbage trucks that brought the trash to the landfill in the first place.

Landfills are not just giant heaps of rotting trash. At the base and sides of a landfill, the trash is separated from the natural world by thick plastic liner, which prevents the effluvia from decomposing garbage from entering the environment and contaminating the groundwater. The trash itself is strategically stacked in layers of cells—landfills can be hundreds of feet deep. Within the landfill, different microbes break down the trash via anaerobic digestion. The microbes produce methane gas as a waste product. There are other gases produced too; this mix of gases produced by anaerobic microbes is called biogas.

Old landfills are punctuated by pipes that collect the biogas, which is then burned to prevent the gas from entering the atmosphere (and prevent the neighbors from smelling the stink). Open flares are just what they sound like—little burning flames of methane. Closed flares filter out the contaminants before the smoke is released. Flaring the biogas at the landfill is probably the most common way of dealing with it. But it is an unfortunate waste of a potentially valuable fuel source.

Newer landfills are built with methane collection in mind from the early stages of construction. Pipes can be buried in the landfill as it is filled with trash. Pipes can also be placed in wells drilled through the trash after the landfill has begun to be filled. A vacuum system collects the gas as the microbes produce it. The amount of gas a landfill produces depends on the volume of trash and the age of the landfill; eventually, the gas production will peak and then begin to taper off. Today’s big landfills, however, can produce biogas for decades.

The methane collected from landfills can generate electricity via a turbine or internal combustion engine. Often some of the electricity is used at the landfill to run equipment, and the rest is sold to the local utility.

Methane from biogas can be converted to compressed natural gas, which can be used as fuel for vehicles. In some areas, regulations stipulate that large fleets of vehicles (with more than about 50 trucks) are required to run on clean fuel. When biogas is converted to compressed natural gas, the vehicles can refuel at the landfill. Building a system that converts biogas into compressed natural gas is a big investment, but the fleet saves on fuel costs for decades. These kinds of biogas systems can be installed at anaerobic waste digesters at places like wastewater treatment plants, not just landfills.

Altamont Landfill has taken things a step further, converting landfill biogas into liquefied natural gas. First, impurities are removed, and then the gas is cooled down to a liquid state. This liquefied natural gas is used to fuel Waste Management’s garbage trucks. Altamont Landfill’s liquid natural gas system is the largest in the world.

Obviously, we should buy only what we need, recycle what we can, and be careful to compost everything that’s compostable. But it’s nice to know that something useful can come from plain old trash.

Oil wells creak in the Bakersfield twilight. Petroleum is not confined to Southern California and Central Valley; we have it in the Bay Area too. Photo by Andrew Alden.

Norma Desmond, the washed-up movie star of Sunset Boulevard, had some memorable lines. One of them was, "I've got oil wells in Bakersfield, pumping pumping pumping." We think of our petroleum as a Southern California thing, or at least no closer than the Great Valley. But petroleum—oil and gas, or both—is widespread around the state, including the Bay Area.

It wasn't just gold, water and agricultural soils that made California rich. Petroleum is one of our greatest natural assets, and the state still ranks fourth in oil production behind Louisiana, Texas and Alaska. While the forests of derricks that once dotted Los Angeles are now subdued and disguised, the Central Valley is still a proud petroleum region, with gas fields in the Sacramento Valley and oil fields in the San Joaquin Valley.

The oil and gas fields of the Central Valley intrude into the Bay Area from the Delta as far as Concord and the Suisun Bay to its north. Gas was produced from the hills north of Concord in the 1960s, and today the old Los Medanos gas field is used by PG&E for storage.

Photo (c) 2007 Andrew Alden

Before petroleum exploration became high-tech, the best way to find oil and gas was to look for natural seeps. An oily sheen on a stream, trickles of tar from a sunny sea cliff, and persistent odors like kerosene are typical signs. These are more common than most people think. Much rarer are actual tar flows like those at Carpinteria Beach near Santa Barbara.

Photo (c) 2010 Andrew Alden

Oil seeps were discovered near Half Moon Bay and in the Santa Cruz Mountains in the 1800s. Asphalt and tar sand were mined from these areas for the streets of San Francisco.

Natural asphalt from the McKittrick tar seep. Photo by Andrew Alden

Later, conventional exploration opened up four districts of producing wells in the San Mateo Peninsula: the Half Moon Bay, La Honda and Oil Creek fields still yield oil today. The Moody Gulch field, which started as a tar pit in 1878, was shut down in 1960 and is now under Route 17.

Photo by Les Magoon, U.S. Geological Survey

Elsewhere in the Bay Area, oil and gas have been produced in Petaluma, Pinole and Livermore. Oil was reported in the Caldecott Tunnel excavations, which is to be expected as the tunnel penetrates our local piece of the Monterey Formation, a petroleum source rock of great extent.

Oil and gas are called fossil fuels, but maybe a better concept is that they are geological compost. They are the bodies of dead plankton, trapped in the mud with no oxygen to consume them. Instead their living substance breaks down and is transformed into simpler hydrocarbon compounds.

The simplest and lightest of these is methane, and that's refined and sold to us as "natural gas." But actual natural gas, the stuff bubbling up in tar pits, is a mixture of compounds. It won't smell like the gas in your stove—that smell is the odorant butyl mercaptan. It's more like the smell of crude oil—a tantalizing, sweeter version of your local gas station. If you don't know how crude oil smells, take a side trip to the oil fields on your way south, like this one just off Interstate 5 at Lost Hills.

Lost Hills oil field. Photo (c) 2010 Andrew Alden

The U.S. Geological Survey has a wealth of material on California's oil and gas seeps at walrus.wr.usgs.gov/seeps.

Cows at Fiscalini Farms in Modesto, California.

Three years ago, we visited a Central Valley dairy that was taking an innovative approach to its waste problem. Instead of collecting thousands of pounds of cow manure in open holding ponds, Joseph Gallo Farms uses it in a renewable energy technology known as a methane digester.

Methane gas is a natural byproduct of cow digestion. It's produced as bacteria inside their stomach break down food.  That process continues on the back end (so to speak) as cow manure decomposes.

Methane is also a powerful contributor to climate change – about 21 times stronger than carbon dioxide. The UN has estimated that 18 percent of greenhouse gases worldwide come from livestock. (Check out this story from KQED's Climate Watch for more on the sources of methane.)

By capturing methane, dairy digesters keep it out of the atmosphere. But they also create a source of renewable energy. Methane is a natural gas — it can be burned just like propane. So, Gallo Farms pipes the methane over to a generator, which produces enough electricity to run the farm and their cheese plant.

Since our visit, the story has taken an interesting turn. Both Gallo Farms and another dairy with a digester, Fiscalini Farms, are located in the San Joaquin Valley – an area with some of the worst air quality the country. The air district is consistently considered in "non-attainment" – which means they aren't meeting the federal limits on air pollution.

While both dairies' digesters are reducing one kind of pollution, greenhouse gases, they're actually adding to another kind.  Generators, like any other combustion engine, produce nitrous oxide pollution – or NOx – which is a component of smog. Given the smog problem in the valley, the local air district decided to put a pollution limit on the dairy digester generators.

Since then, both dairies have struggled to meet to the limits. Unlike pipeline-quality natural gas, the methane (or biogas) that comes from a digester varies in quality, which affects how much pollution is produced in the generator's exhaust. John Fiscalini of Fiscalini Farms has spent $200,000 on a pollution control device that reduces NOx pollution. But he says it's been a challenging process and he's concerned that other dairies have been discouraged by his experience with regulators.

For more on Fiscalini's story and more about the challenges facing dairy digesters, check out this week's radio story.

Listen to Cow Power Not Cutting It radio report online and check out the slideshow below for more on how dairy digesters work.

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NASA's Cassini spacecraft captured this image of sunlight
reflecting off of a lake on the surface of Saturn's moon Titan.
Credit: NASA/Cassini

The evidence for the existence of lakes on Titan has been building since 2004, when the Cassini spacecraft, and its Titan-landing probe Huygens, arrived in the Saturn system and began collecting data.

First it was imagery from the Huygens camera as it descended through Titan's thick, hazy atmosphere: what looked like dark, flat, featureless regions defining apparent coastlines along solid terrain, as well as dentritic patterns like river channels draining into them.

Then it was imagery from Cassini's smog-penetrating infrared cameras showing numerous systems that looked for all the moon like giant lakes—on the order of size of Earth's Great Lakes. Cassini radar bouncing off the surfaces suggested that they were exceptionally flat, as one expects a watery surface to be.

Then there was confirmation of surface liquid in Titan's Southern Hemisphere—but not in the north, where the lake-like shapes were by far more numerous…an apparent land o' lakes.

Finally, what scientists hoped to see appeared, in a flash: sunlight, reflecting off of a Titanian lake called Kraken Mare, came shining through the moon's haze and was captured by Cassini's infrared camera. It's the same kind of reflection you see when sunlight blazes off the surface of the ocean before sunset. Astronauts see the same thing from Earth orbit, looking down at the ocean-lined limb of the Earth when the Sun is at the right position over it.

It required the right conditions; the Sun had to be in just the right position relative to the lake for the reflection to be seen. Ever seen the light of the setting Sun reflecting off the window of a distant house, though only for a moment when the geometry is just right? And only recently did the Sun rise over Kraken Mare's extreme northern latitude, after the 15-year dark of a Titanian arctic winter.

Titan is the only Solar System object known to have surface liquid, other than Earth. Jupiter's moon Europa is thought to harbor a vast ocean of liquid water, but under its outer crust of ice. Another of Saturn's moon's, Enceladus, also appears to hold liquid water inside, but its surface is as dry as the Earth's Moon. And yes, the Moon was recently confirmed to have surface water—but it's all frozen and mixed in with the lunar soil in a sort of dry cryo-mud.

The difference with Titan, however, is that its surface liquid is not water at all, but methane. It's too cold on Titan's surface for liquid water to exist there—but Titan's atmospheric pressure and temperature are right for methane to exist in its liquid state. So while on Earth we know methane as a greenhouse gas emitted by decomposing plants and the guts of cows—to name a couple of sources—on Titan it is the stuff of cloud, of rain, of river, and of lake.

What a wild world!

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Methane concentrations revealing a plume in Mars' northern
hemisphere during its summer season. Credit: NASA

We've known about the existence of methane gas on Mars for several years now, from independent observations.  Further observations have led to the detection of "plumes" or clouds of methane gas apparently emanating from specific locations on Mars.  One plume is estimated to contain 19,000 metric tons of the stuff.

Why is this exciting news? If you know anything about the source of most of Earth's atmospheric methane gas, you already know the answer:  possible life.  Not, I should say, necessarily life on Mars, but maybe a strong piece of evidence in that direction.

On Earth, methane (CH₄) is produced by living organisms—mostly by the activity of microbes, but some by the digestive processes in larger organisms (yes, like humans, and cows).  Methane is the major constituent of natural gas, which fuels gas powered ovens and heaters in homes, as well as natural gas power plants.  Methane is also produced by decaying organic matter—that's where "swamp gas" comes from.

On Mars, methane gas cannot exist for long in the atmosphere; it is relatively quickly broken down by solar radiation.  So, the methane detected in Mars' atmosphere must be replenished by something, continually.

So the big question right now is, where is the methane coming from? Under the surface of Mars, almost certainly.  By biological processes—life—underground? Could be.  By non-biological means? Could be, too; methane can be produced through inorganic chemical processes.  We don't know yet.  The next step in finding out more will be the Mars Science Laboratory, a large rover scheduled to be launched to Mars sometime in the near future.

In one form or another, humans have been trying to see, or find, life on Mars for a long time.  Percival Lowell squinted at Mars' small, blurry disk through his 24-inch telescope in Flagstaff, and perceived markings he saw to be vast canal complexes, ostensibly built by a desert Martian civilization thirsty for water harvested from their planet's polar ice caps. This led to much of the science fiction relating to life on Mars in the 20^th Century.

Earth-bound telescopes noted seasonal changes in Mars' color and brightness, and some attributed this to possible seasonal growth of Martian vegetation—though it was later found that these variations were the effects of seasonal planet-wide dust storms.

The Viking landers' primary mission in the 1970's was to search for life.  They didn't find any by scratching around Mars' surface and testing the soils there.

The 1990's saw the controversy over microscopic structures in meteorites found on Earth but determined to have originated on Mars.  Some argued that these structures were fossils of Martian microbes that lived on Mars long ago.  Whether these findings were in fact fossils and not just geologic structures was never conclusive.

The determination that liquid water once flowed on the surface of Mars, and still exists under its surface at least as ice, is pretty much scientific fact today.  Evidence of past liquid flows have been imaged and mapped from space, and the Phoenix lander found water ice in the north polar regions last year.  And there's the rover Opportunity that has confirmed gray hematite, a mineral that forms in the presence of water.

It's almost certain that there are no Martian cows grazing the rusty desert plains out there.  But there seems to be a lot of evidence for the possibility that something is going on below Mars' surface—perhaps the presence of liquid water, perhaps the presence of some form of life.  We don't know yet, but it sure feels like we're onto something here….

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To learn more about the travels of sewage, I took a tour of the Las Gallinas Valley Sanitary District treatment plant led by Plant Manager Matt Pierce. The plant has been in operation for about 50 years and serves over 30,000 residents in north San Rafael.

After leaving sinks and showers throughout the District, wastewater travels through a network of pipes and pump stations. Once the sewage arrives at Las Gallinas, it passes through an inlet screen and a grit chamber, which together remove much of the dense, inorganic material-"like diamond rings," Matt jokes.

A lot of what happens at the plant is not that different from what happens in your compost pile: "It's basically bacteria at work," Matt points out. (The much bigger challenge for sanitation districts these days are all the unnatural things we're putting down the drain: household chemicals, personal care products, pharmaceuticals.)

From the grit chamber the sewage heads into a series of clarifiers, where gravity causes the organic solids to settle out. The biosolids pass through a thickener and then an anaerobic digester-the most, ahem, aromatic stop on our tour. After further thickening in storage ponds, the sludge is injected into a disposal field.

Meanwhile, the liquid from the clarifiers travels through two biofilters, where rotating arms spray the water over rock beds. The organic matter in the wastewater is a feast for microbial slime living on the rocks. In the nitrification tower, more microorganisms break down the ammonia in the water. In the final stages of treatment, the wastewater is chlorinated to kill any remaining bacteria, then dechlorinated since the chlorine is toxic to many aquatic species. Finally, the treated water is sprayed onto District fields or discharged into Miller Creek where it flows to San Pablo Bay.

The District has done a lot to minimize the environmental impacts of its operations. The plant is powered by a field of solar panels. The methane released in the sludge treatment process is captured and used to generate power and heat the digester. Some of the treated wastewater supports acres of fresh and saltwater wetlands-in fact the District's land is a favorite local gem for walkers and birders. And in a partnership with the Marin Municipal Water District, more than a million gallons of treated wastewater are recycled daily for landscape irrigation and other projects.

There are plans to make even fuller use of the reclaimed water. The Bay Institute-in partnership with the Sonoma County Water Agency, Las Gallinas, and three other North Bay sanitation agencies-has developed a plan to use recycled water for wetland and creek restoration and for agricultural irrigation. Legislation sponsored by Congressman Mike Thompson to establish the program passed the House late last year; Senator Dianne Feinstein has introduced similar legislation that we are hopeful will pass this year.

With California's growing demands for water, such creative means to conserve and recycle are critical to helping prevent this precious resource from just going "down the drain."


Ann Dickinson is Communications Manager for The Bay Institute (www.bay.org), a nonprofit research, education, and advocacy organization dedicated to protecting and restoring San Francisco Bay and its watershed, "from the Sierra to the sea."

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The 2006 Word of the Year was "carbon netural" in the The New Oxford English Dictionary. But there's still a lot of debate about what it means. Many people compare the U.S. carbon offset market to the Wild West. Since there is no regulation, how do you know what you're buying?

There are several guides to carbon offsets that have been created by non-profit organizations, designed to help the average consumer (see related resources). But part of the problem is that many people are still debating what a carbon offset should be. And that's a debate that can be found in the blogosphere.

One place you can find it is on the Grist.org blog which has many bloggers writing about green issues. Forestry offset projects, which sell credits based on the fact that trees sequester– or hold carbon dioxide, have come under fire. You can read about a few of the critiques here, here and here.

Another blog, Treehugger.com, has followed the issue as well. They posted this comparison of offset providers to help their readers do their homework and this more in depth guide on the issues buyers should be aware of.

Of course, one of the earliest debates over offsets was whether offsets would act as "indulgences", distracting consumers from making concrete changes in their lifestyles to reduce their carbon footprint. Terrapass, one offset retailer, has tried to investigate this by surveying their customers. They found that the majority of them had already had green habits. Still, the virtues of offsets are a matter of personal opinion.

You may listen to the "Cashing in on Carbon" radio report online, as well as find additional links and resources.

Lauren Sommer is an Associate Media Producer for QUEST.

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