A dairy cow produces about 54 kilograms of manure per day thats 120 pounds of manure. For farms with cows numbering in the thousands, thats a lot of manure. With increasing concerns about pollution arising from so much manure, some farmers have begun turning to an old technology methane digesters to help deal with the vast amounts of waste. But farmers are getting an added bonus: They can produce electricity, potentially saving hundreds to thousands of dollars a month in energy costs.
Farmer Albert Straus stands in front of the manure separator on his farm. The separator is part of a methane digester that produces energy and saves the farm $3,000 to $4,000 monthly in energy costs. Image courtesy of the Straus Family Creamery.
Methane digesters are enclosed tanks that use specific populations of naturally occurring bacteria to break down manure into methane and carbon dioxide in a low- to no-oxygen environment. This biogas, which is about 60 to 70 percent methane, can then be harvested to provide energy. The technology is fairly old and is proven to work, says Don Jones, an agricultural engineer at Purdue University in Indiana.
Indeed, municipal wastewater treatment plants have been using methane digesters to treat waste since at least the 1930s, says Allen Dusault of Sustainable Conservation in San Francisco. During World War II, when Europeans needed energy and had no way of transporting it, they utilized local animal waste to create methane. And in the 1970s, when energy prices skyrocketed and the environmental movement was going strong, people began to realize that animal manure could be a source of renewable energy, he says. Additionally, countries such as India and China have long used methane digesters in remote villagesas a source of cooking fuel and electricity.
More recently, the technology has been getting another look because there has been a growing concern about pollution from large farms, Dusault says. Typically, large farms will store liquid and solid manure produced by livestock in large waste ponds, and then pump the manure, which contains valuable nutrients needed for crop production, back out onto the fields as fertilizer. But the system has problems for large farms, including strong odors, pathogens in the manure, and the fact that heavy rains or storms can flood the ponds and land where manure has been spread, allowing manure to reach local water sources. Furthermore, people are realizing that methane a greenhouse gas more than 20 times more powerful than carbon dioxide from farms is contributing to greenhouse gas warming in the atmosphere, Dusault says.
The technology, which is available in various forms depending on the type and size of farm, keeps becoming more attractive as energy prices and environmental concerns rise. Digesters reduce the amount of the organic matter while treating the remaining material, so that the waste can be used as fertilizer without creating pollution. The digesters also reduce odors by more than 90 percent and can provide electricity.
Most methane digester systems collect waste in heated storage tanks or in the waste ponds. Either actively or passively, the systems separate out the solids from the biogas that is generated during anaerobic decomposition of the waste. The result is biogas that is pumped into a generator to produce electricity.
Farmers can either use that electricity and the byproduct (hot coolant water) for their farm needs, or they can send the power to the local electricity grid. If the digester is working efficiently, a typical dairy farm with 500 cows could produce 1,000 kilowatt-hours of electricity per day, according to Discovery Farms, a program affiliated with the University of Wisconsin in Madison.
At the 300-cow Straus Family Creamery just north of San Francisco, for example, a methane digester produces 5,000 gallons of hot water and some 3,300 kilowatts of electricity a month supplying all the electricity for the farm and saving the Straus family about $4,000 a month in electricity costs, says the farms owner Albert Straus. The Straus farm sends its energy into the grid, using a system called net-metering, where their electricity meters run backward when more energy is going out than coming in.
Methane digesters are not for everyone, however, Dusault says. We have found that these systems work better for bigger farms its an economies-of-scale issue, he says. Digesters cost anywhere from $250,000 to more than $1 million, depending on the type of system and number of animals, and seem to work best for dairy farms with more than 400 animals. However, large swine farms and smaller dairy farms can use them, especially if several neighboring dairies team up to use one system, as they have done near Tillamook, Ore., where the Port of Tillamook Bay runs a digester shared by six farms. Dusault also notes that grants are available through several state and federal agencies.
In addition to cost, running the technology requires more time and effort (especially for maintenance) than is reasonable to request of most farmers, says Jones of Purdue. Running these systems takes away from their primary job raising livestock so producing electricity wont likely be a high priority for farmers.
For methane digester systems to be truly widespread, he says, third-party specialists need to perform the routine maintenance and checks for farmers. Dusault agrees, adding that farmers need financial incentives to make it worth their while, such as deals where utility companies would pay farmers market prices for their electricity that is going into the grid something only certain states and utilities do.
Progressive farmers, such as Straus and the dozens of other farmers throughout the United States who are utilizing methane digesters, are the anomalies, Dusault says. However, were on the cutting edge here, and 20 to 30 years from now, I think this will be standard practice.
Now that the technology is up and running on his farm, Straus says that his family will keep working on being self-sustaining. Knowing that he is doing something beneficial for the land is a good feeling, he says and theyre saving money.
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bread basket to fuel pump
In the aftermath of Hurricane Katrinas strike on New Orleans last fall, Josh Tickell drove his VeggieVan into town to bring as much relief as he could. He was delivering not only food but also something more scarce: energy in the form of vegetable-based fuel.
Josh Tickell took his biodiesel-fueled Veggie Van, shown here, to Louisiana after Hurricane Katrina to deliver biodiesel and other relief aid. Tickell advocates the use of biodiesel made entirely from cooking oil, whether it is processed fresh soybean oil, used restaurant oil or rendered animal parts. Image courtesy of Josh Tickell.
Tickell, a Los Angeles-based activist who has been bitten by the biodiesel bug, created his diesel-engine VeggieVan in 1997, to promote the benefits of biofuel on cross-country tours. Those benefits, he says, include a cleaner burning fuel and a more sustainable fuel economy. Powered by biodiesel made from vegetable oil in his own van, Tickell helped arrange for other biodiesel-powered trucks and ships to get into the Gulf Coast region with biodiesel fuel, along with other supplies.
Usually made from chemically processed soybean or rapeseed oil, biodiesel is most often used in a mixture with petroleum diesel. And although do-it-yourselfers may make it sound as easy as dumping a bottle of canola oil in the tank, commercial use requires a few more steps and some high costs, making biodiesel a minor player in the energy market.
Still, Bruce Anderson of Woodruff Energy, located in southern New Jersey, says that the companys customer base has steadily grown over the last two years. The company sells biodiesel that powers the 50-plus vehicles of the Atlantic County Utilities Authority (including dump trucks and other heavy-duty vehicles) and the school bus fleet for Pittsgrove Township, among its other customers, with about 33,000 gallons per month of a biodiesel mixture called B20. The name refers to the percentage of biodiesel in the composite fuel in this case, 20 percent vegetable-based and 80 percent petroleum-based diesel.
The demand for biodiesel is growing, Anderson says, including among farmers in his region who use B5 or B20 biodiesel for their tractors and other equipment during the summer working season. Woodruff Energy is even considering expanding its use of B5 biodiesel to provide it as heating fuel for its customers next year, he says.
The allure is a cleaner fuel that produces less emissions, including about 12 percent fewer particulates than petroleum products for B20 biodiesel, for example, according to results published by the U.S. Environmental Protection Agency in 2001. Less soot also means a cleaner engine, and biodiesel lubricates engines more than petroleum.
Biofuel promoters say that biodiesel and regular diesel function exactly the same, though filters should be replaced more often at first. However, some manufacturers say that biodiesel fuel may harm engines. Equipment company John Deere, for example, promotes the use of B5 biodiesel in its tractors and other products, but warns that pure vegetable oil will leave deposits on injectors and in an engines combustion chamber.
Even though the chemical process to make biodiesel is a century old, it still requires careful tracking of processing plants and mixers for quality control. Also, some suppliers must make an expensive switch to clean tanks to store pure vegetable oil at temperatures warmer than 4.5 degrees Celsius (40 degrees Fahrenheit).
In general, biodiesel remains more expensive, even at the 5 percent mix. Adding processed soybean oil to regular diesel fuel can bring the price up dramatically, according to the Energy Information Administration (EIA). Costs for producing biodiesel from soybean oil tend to hover at about $2.25 a gallon, while petroleum costs around $1.40 cents a gallon to make (before distribution costs or taxes).
That cost difference means that some of the alternative fuels adopters have started at the low end for their fleets, using B2 or B5 biodiesel. It also means that subsidies have proven necessary for B20 fuel, as in New Jersey, where the state reimburses users for the bio part of biodiesel, says Anderson of Woodruff Energy. Without a reimbursement program, large companies are unlikely to make the switch on their own, he says.
Practically nonexistent in the mid-1990s, biodiesel use has grown substantially, says Anthony Radich of EIA. Still, it is difficult to track, and biodiesels share of the fuel market requires a magnifying glass, he jokes. Through the third quarter of fiscal year 2005, the United States was expected to consume 46.5 million gallons of biodiesel for on- and off-road vehicles and heating oil, according to EIA, compared to the predicted 64.2 billion gallons used of regular distillate fuel. Thats three orders of magnitude smaller, Radich notes.
Still, he says, new quota requirements passed by several states, including Minnesota and New York, mean that the market share for biodiesel will probably continue to grow. In Minnesota, several new biodiesel plants that came online last year couldnt have timed it better, when oil is scarce and prices [are] very high, Radich says. Anderson says that Woodruff Energy sees biofuels as a niche thats going to be here for years to come, as well as an alternative to buying fuels from countries overseas. Other countries have encouraged biofuel use as well, including Brazil, Canada, India and China.
Costs, however, remain ruled by how much vegetable oil can be produced and the fact that soybeans are used in food, which keeps prices high. Farming costs include pesticides and fertilizers, as well as the fuel it takes to run the vehicles for planting, harvest and other agricultural tasks, notes David Pimentel, an ecologist at Cornell University in Ithaca, N.Y. In a controversial paper published last year, he and colleagues calculated that the entire United States would have to be planted with soybeans to get enough fuel for the countrys needs. The net land use is enormous, he says, though it does make sense for making vegetable oil for cooking.
Ideally, biodiesel should be made from whatever vegetable oil is produced locally, be it used cooking oil or soybean oil, Tickell says. Tim Lindsey, who manages the pollution prevention program for the state of Illinois, harvests used cooking oil from the University of Illinois residence hall cafeterias, brewing up B100 for use in a department truck, and even an experimental batch for a local high school bus essentially getting both french fries and clean fuel from the mix.
In Europe, government mandates on animal byproducts now make it illegal to recycle cooking oil as animal feed, essentially creating a massive influx of biodiesel supply into the European Union markets and spurring industrial use, according to Tickell.
But recycling U.S. restaurants cooking oil a resource that grows as population grows really only has potential there to make a few hundred million gallons, Radich says, something that is fairly small compared to the entire diesel pool.
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Flying high on plant waste
Plant waste could one day propel jets through the skies that prediction came from Virgin Atlantic chairman Richard Branson at the Abu Dhabi World Leadership summit on Nov. 15 in response to soaring gasoline prices, according to a Nov. 16 Reuters report. Branson announced that within five to six years, he hopes to start supplying plant-waste fuel, or cellulosic ethanol to the companys fleet, which now consumes 700 million gallons of fuel a year.
Creating fuel from plant biomass is not a new concept. Ethanol derived from corn and other starch grains has already made its way onto the market, with over 4 billion gallons now produced per year in the United States, according to Charles Wyman, a professor of chemical and environmental engineering at the University of California, Riverside. But he says that ethanol derived from cellulosic biomass, such as agricultural and wood residues, instead of from grain, has become more cost-competitive.
Over the last 20 years, advances in technology have helped to decrease the cost of cellulosic ethanol production by a factor of four, to a current projected cost of about $1.20 a gallon (prior to pump taxes and distribution fees). That price varies significantly, however, depending on factors that include the cost and location of feedstock, according to Jim McMillan, a bioprocess research and development manager and senior engineer with the National Renewable Energy Laboratory in Golden, Colo.
One area in which researchers are looking to reduce costs is production efficiency. Scientists have genetically engineered organisms to efficiently ferment all five sugars present in cellulosic biomass, converting them into ethanol with ever higher yields. That is a key to success, Wyman says, noting that continued advances in pretreating cellulosic materials and in biological processing techniques could eventually reduce the cost to 50 cents or 60 cents per gallon.
Production of cellulosic ethanol is better for the environment compared to that of conventional fuels, Wyman says, because it contributes little if any net release of carbon dioxide and other greenhouse gases. Thats because the byproduct from ethanol production can be burned to provide enough energy to run the entire production process, with excess electricity leftover to export. And unlike petroleum, Wyman says, the availability of plant materials can be sustained: A recent report by both the U.S. Department of Energy and the U.S. Department of Agriculture projects that about 1.3 billion tons of biomass could be available annually in the long term.
But challenges remain in making ethanol fuels (both plant waste- and corn-derived) competitive with gasoline, according to McMillan. First, the energy content of ethanol is less than that of gasoline for the same unit volume. Second, the current pipeline infrastructure used for gasoline does not accommodate ethanol. Water does not mix with gasoline, so any water that enters the pipe can be easily removed, but water does mix with ethanol, requiring a new infrastructure. Building new pipelines to accommodate ethanol would be costly, McMillan says.
Wyman and McMillan both agree that another major impediment is the perceived risk of being first to put down the large capital investment needed to build a commercial facility. Everybody wants to be the first to be second, McMillan says. Companies such as Virgin Atlantic, however, plan to build such plants for their own use, though the airline companys officials say that plans are still in preliminary stages.
The idea of using plant waste to fuel airplanes is not unheard of. Corn ethanol has been used in airplanes now, Wyman says, but not jets. He notes that Maxwell Shauck, professor and chairman for the Institute for Air Science at Baylor University in Waco, Texas, has used ethanol to fuel a propeller-driven aircraft.
Still, no large-scale commercial plants exist today that produce cellulosic ethanol. Government incentives, Wyman says, are needed to greatly accelerate commercial production of plant waste for use as a beneficial alternative fuel.
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to light up New York
Walk along nearly any street in New York City and it is difficult to miss the towering heaps of black garbage bags that line the streets the city collects about 12,000 tons of residential trash per day for its five boroughs, according to the New York City Department of Sanitation. With the growing problem of landfills reaching capacity and nowhere for New Yorkers to dump their trash, some researchers are suggesting a fiery solution.
The Hempstead Resource Recovery Facility, located on Long Island, is one of a small number of waste-to-energy facilities in New York. The plant can turn 1 ton of garbage into enough energy to heat an average office building for one day. Image courtesy of Covanta Energy.
The first U.S. trash-burning incinerator was built in New York more than 120 years ago, according to the U.S. Energy Information Administration (EIA). Modern versions, however, come with an extra perk: They are equipped with technology that allows them not only to take in trash, but also to give back energy in the form of electricity. Engineers and public affairs experts at Columbia University in New York City say that such plants, called waste-to-energy (WTE) plants, are a viable and energy-smart solution to New Yorks encroaching trash dilemma.
About 40 kilometers away from New York City, in Westbury, N.Y., on Long Island, the Hempstead Resource Recovery Facility burns garbage 24 hours a day, seven days a week. A daily maximum of 2,505 tons of municipal solid waste, including everything from yard waste to plastic containers but excluding hazardous items such as refrigerators and fluorescent light bulbs, arrives by truck and is dumped into a receiving pit. Next, six rolling grates carry the trash through the boiler, which burns at about 1,090 degrees Celsius (2,000 degrees Fahrenheit). The heat in the combustion gases is converted into high-pressure steam that turns a turbine and produces an average 72 megawatts of electricity per year, which Hempstead sells to Long Island Power Authority for distribution to Long Island residents.
The plant reduces the original volume of trash by 90 percent. One ton of garbage produces about 550 kilowatt-hours of electricity, according to EIA statistics, which is enough to heat an average office building for one day.
No WTE plants currently exist within New York Citys limits, although a small amount of trash from Queens is shipped to the Hempstead facility. But in the scope of what the city generates, its very, very small, says Patricia Motschmann, a public relations official at the Hempstead facility, which is operated by Covanta Energy.
Instead, most of the 540,000 tons of trash delivered annually to Hempstead comes from nearby towns on Long Island, where landfills are illegal because of sandy soil and the potential for the contamination of underground drinking water supplies. Motschmann says that she thinks New York City would benefit from a WTE plant, but the city would need to go through their own process to find out if they can handle the waste.
WTE plants were indeed on New York Citys radar when its principal landfill Fresh Kills on Staten Island reached full-capacity and closed in March 2001. In December 2001, Columbia Universitys Earth Engineering Center and the School of Public Affairs presented a joint report to Mayor Bloomberg, based on technology and policy studies of New York City and other communities, and recommended implementation of WTE facilities. Public outcry, however, from environmental activists drove the mayor to invest mainly in other options, such as shipping trash to out-of-state landfills, says Nickolas Themelis, chemical and metalluragical engineer and chair of Columbia Universitys Waste-to-Energy Research and Technology Council.
Fifteen years ago, WTE plants were among the major emitters of mercury and dioxins in the United States, Themelis says: We did not know enough and were not using adequate controls on the emissions of high-temperature resources. That has changed in recent years.
In 1990, the Environmental Protection Agency (EPA) established technology-based air emission standards under the Clean Air Act Amendments, which called for the regulation of 189 hazardous air pollutants. Ten years later, following the incorporation of scrubbers and filters into the plants, dioxin emissions from U.S. plants dropped 99.7 percent and mercury was reduced 98 percent. Still, the perception remains that WTE plants are not a clean, good thing, says Joe Bryson of EPA.
Brian Guzzone, also of EPA, says that WTE technologies are among some of the most heavily regulated sources of emissions in the country. The industry has come a long way, but that message is not being believed, Guzzone says. One reason for the negative perception may be due to what Guzzone calls the not in my backyard, or NIMBY, phenomenon.
Communities need to realize, Themelis says, the environmental benefits of WTE plants, which include the reduction of methane-emitting landfills and pollution from long-distance trucking of trash. At the same time, legislators perceptions need to change for WTE plants to be accepted under the term renewable energy and be considered for tax incentives.
Internationally, WTE technology is taking off. WTE plants in Japan, which according to EIA burn about 62 percent of the countrys trash as opposed to 14 percent in the United States, have been successful at implementing new technologies, Themelis says. One plant in Sendai, Japan, incorporates additional oxygen into the combustion process, which allows garbage to burn at higher temperatures. The hotter temperatures are sufficient to turn ash into glass-like pellets that can be used in place of stone aggregate.
In Brescia, Italy, a WTE plant uses the exhaust steam to heat water, which is then piped through a district heating network that extends over 550 kilometers, resulting in the shutting down of thousands of small residential boilers in the city of Brescia. (In the U.S. plants, the low-pressure steam exhaust from the electricity-generating turbine is wasted.) Themelis says that the air quality in Brescia has improved since the WTE plant went into operation in 1998.
Whether or not New York and other U.S. cities will follow Sendais and Brescias lead remains to be seen. Kathy Dawkins, a public information official for the New York City Department of Sanitation, says that the current short-term export plan includes the provision that a small amount of the citys waste be disposed at two WTE facilities the Hempstead facility and also a plant in Essex County, N.J., across the Hudson River. The department is also working on a 20-year solid waste management plan, for which alternative disposal plans are being explored, she says.
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