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Environment: Landfill turns gas into energy

Posted: September 19, 2011 1:55 a.m.
Updated: September 19, 2011 1:55 a.m.

Ameresco plant specialist Jeffrey Bell displays a ball of chalk at the Ameresco Power Plant in the Chiquita Canyon Landfill in Castaic on Friday. The balls are used to separate impurities from raw methane gas taken from the landfill.

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Nearly a year after the Chiquita Canyon Landfill near Val Verde began turning methane into clean, renewable energy, the site is becoming a local green industry model.

Currently, the landfill produces six megawatts of power on average daily, kicking out enough electricity to become totally self-sufficient and generating a surplus of energy that it sells to supplement the state’s power grid.

The operations are run by Waste Connections Inc., which has been in the Santa Clarita Valley for almost 40 years.

It describes itself as an integrated solid-waste-services company providing solid-waste collection, transfer, disposal and recycling services in mostly secondary markets in the western and southern United States.

It sells its methane to Ameresco — one of the largest independent energy service companies in North America with headquarters in Framingham, Mass., and a California office in Temecula.

Ameresco, in turn, sells the electricity produced from the methane to local utility companies.  The electricity it generates at Chiquita is wired directly onto the state’s power grid at the landfill, earmarked for present use by the city of Pasadena.

Most of the money made by Waste Connections at Chiquita comes through “tipping fees,” which trash companies and people pay to dump their couches, soup cans, shampoo bottles and all other garbage.

“We sell Ameresco the gas and they take care of everything else and sell the electricity,” said Mike Dean, Waste Connections division vice president at Chiquita.

“It’s profitable,” he said. “We do it because it’s a good thing to do and because it’s a green thing to do, but it’s not a big money maker for us.”

When garbage is dumped at the site, it decomposes, giving off gases. The most significant of those gases is methane, a chemical compound that serves as the principal component of natural gas.

Before it was harnessed and processed for energy, landfill managers used to simply burn off methane.

“And, it’s a lot of energy,” Dean said. “In the past decade, or so, there’s been a lot of plants that take the methane and do something with it — generate electricity or clean it up and sell it as a quality pipeline gas.”

Chiquita went green about 10 months ago when it started capitalizing on its methane and, through Ameresco, began making its own electricity.

Capturing gas

At Chiquita, between Santa Clarita Valley and the Ventura County line, amid 600 acres of rolling dirt and refuse manicured with bulldozers, sits a cluster of tanks, as big as large sports utility vehicles, all connected with pipes you could just barely get your arms around.

A network of smaller perforated pipes — measuring more than 25 miles in length — is buried under the ground.

Gases, predominantly methane, are drawn out of the ground by a vacuum — the way soda is sucked through a straw — and funneled into wells.

Jeff Bell is the methane plant’s operator employed by Ameresco.

Every six minutes, he and his fellow Ameresco partner Jesus Vega monitor the oxygen level of each well to ensure it doesn’t pose a fire safety threat.

Almost half the gas “sucked” from the landfill is methane.

“When we get the gas from the landfill, it’s really dirty, saturated with silicone content and VOCs,” Bell said, referring to emissions released through the breakdown of plastics.

According to the Environmental Protection Agency, volatile organic compounds — or VOCs — are organic chemicals that have a high vapor pressure at ordinary, room-temperature conditions.

It’s this pressure that causes large numbers of its molecules to change from its liquid or solid forms directly into the air.

Many VOCs, according to the EPA, are dangerous to humans and harmful to the environment.

The gas captured at the Chiquita landfill is “blown” through pipes under 5 pounds of pressure per square inch and sent to “coolers, chillers and scrubbers” that remove VOCs and other impurities.

By comparison, tire pressure for cars and trucks is between 30 and 45 psi.

Before the VOCs are removed, however, plant operators first remove water from the gas.

“The gas goes through the chiller, and it’s getting cold and it’s knocking out all the water, because we want our gas to be as dry as possible,” Bell said, largely to avoid any of the gas-processing machinery becoming corroded.

The chiller produces 500 gallons of condensation water every 24 hours.

Bell was asked if that water could be recycled.

“It’s real dirty. It’s not just water water; it’s water that if you get a drip on you, you’re going to smell for the rest of the day. It’s real nasty dirty water saturated with all that methane,” he said.

The collected water is “sprayed” by injectors into a large flare inside a silo and “burned off” through evaporation.

The remaining dry gas is then sent to four SUV-sized vats containing 2,000 pounds of plastic beads that look like marbles made of chalk.

Emissions from landfill plastics broken down adhere to the plastic beads.

When the beads become coated with brown dirty residue they’re heated and washed.

At any one time, one of the four “plastic bead” vats is taken off line for about 16 hours so that the “media” beads can be heated to about 600F, cooled, purged and ultimately burned.

“It’s cleaning out the silicones, the VOCs,” Bell explained. “These are from plastics dumped in the landfill, anything from shampoo bottles to drywall.

“The reason we want to take VOCs out as much as we can is because when we heat it up and send it through our turbines it’s going to stick to our turbine blades like plastic,” he said. “We monitor our emissions continually through our turbine exhaust to ensure we meet California emission standards.”

Surplus methane — not sent to the turbines — is burned in a 50-foot silo, a feature that Dean says regularly entertains packs of Boy Scouts, Girl Scouts and elementary school classes visiting the landfill on field trips.

Clean methane

Once gas siphoned from the landfill is cleaned to leave only methane, it’s sent to two other SUV-sized vats containing charcoal filters that “dry the gas a little bit more” and ensure moisture doesn’t get into air compressors.

“We’re going to save in the long run, because we won’t have to shut down our unit due to corrosion caused by moisture,” Bell said.

The compressors take the air arriving at 5 psi and converts it to 260 psi.

“That’s quite a force,” Bell said. “We need 260 psi to run our turbines to produce electricity.”

The turbines at Chiquita produce between 5 and 6 megawatts of power a day depending on the atmospheric temperature.

A megawatt is the same as 1 million watts.

One megawatt can power an estimated 1,000 homes.

The self-generated electricity not used on site at the Chiquita landfill is sold by Ameresco and put on the state’s power “grid,” specifically earmarked for use by the city of Pasadena.

Dean says landfill-made electricity is profitable, but in realistic terms, just manages to pays for its own costs.

Recently, landfill owners at Waste Connections Inc. asked Los Angeles County planning officials to amend the firm’s conditional-use permit to table one of three county taxes it pays to operate the dump and extract methane for sale.

Very simply, the company was being taxed twice for the same methane-to-energy process.

Company officials argued the exemption would allow it to harness naturally occurring, energy-rich methane at the landfill and sell the gas.

The county, subsequently, amended the taxes it demanded of the landfill.

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