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Biomass Makes the Grade for Renewable Energy Producers
Biomass Makes the Grade for Renewable Energy Producers
Biomass Makes the Grade for Renewable Energy Producers
Biomass Makes the Grade for Renewable Energy Producers
by Mollie Day
Across the US, states are working to establish renewable energy standards. As these standards take shape, an increasing number of energy producers are turning to biomass to meet their renewable energy goals. One advantage of using biomass over other sources of renewable energy – wind and solar power, for instance – is its relative ubiquity. Many areas of the US are simply not well suited for generating wind and/or solar power. But biomass, if one can find a near enough source, tends to be readily available.
Biomass is a renewable energy source derived from living organisms, such as wood waste and plant matter. It is generally burned to either generate electricity or produce heat. Common forms of biomass include forest residues, yard clippings, wood chips and even garbage. Biomass also includes plant or animal matter used in the production of fibers or chemicals, as well as biodegradable waste that can be burnt as fuel. Wood-based biomass energy is derived both from direct use of harvested wood as a fuel and from wood waste streams. The largest source of energy derived from wood is the black, pulping liquor that is a byproduct of the paper and paperboard industry.
Pioneering Wood-Fueled Energy
Though biomass-fueled power plants are springing up across the US, biomass still has a long way to go before it can supplant oil as the nation’s primary fuel source. But some progressive institutions in the private and public sector are inching ever closer to complete independence from oil. Vermont’s Middlebury College, for instance, is an excellent example. The college recently replaced the oil-fueled boiler the generates power for its campus to a wood-fed gasifier, dramatically reducing its dependence on oil and its carbon emissions. The switch also added hundreds of thousands of dollars annually to the local timber-based economy. “We’re a leader (in biomass energy),” says Jack Byrne, Middlebury’s Director of Sustainability Integration. “We’re probably less of an exception than we used to be, but we’re out there in terms of the sustainability envelope.”
Middlebury College first fired its advanced wood combustion power plant in 2009. The plant is now the backbone of the college’s renewable energy portfolio. Middlebury expects to burn 20,000 tons of wood chips annually, producing enough heat and electricity for the entire campus. The plant is also a boon for the local economy. “We were spending $1.5 million to buy fuel oil from Venezuela and Saudi Arabia, and now were spending $800,000 to buy wood chips from local loggers and foresters,” says Byrne. “That’s money that had never been in the local economy before because it was going off to the oil supply chain around the world.”Middlebury expects its power plant will cut CO2 emissions by 40 percent after one year of operation. Already the college has reduced its use of fuel oil by 50 percent. In addition to the power plant, two of Middlebury’s buildings now have their own, respective energy sources: a 3-kW solar array (which includes a monitoring system) and an 8- kW PV array. Additionally, a 10-kW wind turbine provides power to the lights and machinery in the campus recycling facility, satisfying about 25 percent of its electricity demand.
A variety of thermal, chemical and biochemical conversion technologies are available to turn biomass into renewable energy. Conversion technologies may release the energy directly, in the form of heat or electricity, or they may convert it to another form, such as liquid biofuel or combustible biogas. While for some classes of biomass there may be multiple options, for others there may be only one appropriate technology. Virtually anything that is considered waste, and that can be safely burned, can be considered biomass for energy. For example, wood, grass, food waste, feces and paper are all viable biomass energy sources. The most common way to extract energy from biomass is through “stand-alone” combustion. Another method, called “co-firing,” involves burning coal and biomass together.
Gasification is yet another form of thermal conversion used to turn biomass into energy.
Middlebury’s gasifier separates carbon from the minerals that occur naturally in wood using advanced wood combustion (AWC) technology. As the minerals combust, they become white ash. The ash is removed, and the carbon, which converts to gas through the process, is burned, like natural gas, in the boiler. “Taking all the carbon out and separating it from the mineral – instead of trashing the carbon – yields a more carbon efficient operation. Fuel purchase is less and air quality is better,” says Bob Bender, owner of Chiptec, a Biomass Gasifier Systems distribution company.Middlebury’s wood burning furnace could be fueled by a variety of biomass sources, including: wood chips and shavings, sawdust, clean bio-fuel, agricultural and food processing residue, wood pellets, paper pellets, railroad ties and other materials. It can also accommodate a wide range of moisture contents (between 6 to 60 percent). But once the gasifier is running optimally on one type of fuel, Middlebury prefers to stick with it, in order to avoid a new and different operating regime for a different fuel.
Local sourcing is the key when it comes to obtaining wood biomass for energy production. Wood biomass is very heavy and costly to transport. Beyond a roughly fifty to seventy-five-mile radius the expense of transporting it becomes economically unfeasible. The challenge for energy producers is finding a continuous, reliable source of wood biomass within that radius.
Before the launch of its wood combustion power plant, Middlebury College hired a consultant to determine whether or not there was a sufficient supply of local wood biomass to suit its mid-sized energy needs of about 20,000 tons annually. After failing to find a single source, the college hired a broker to secure a reliable, regular supply of wood chips from a pool of suppliers. Middlebury’s contract specifies that any wood chips they purchase must come from within a 75-mile radius from the college. Their primary source for materials are private forest lands that are under a forest management plan. The rest of the materials are shipped in from land clearing and construction projects, and nearby saw mills.
Sourcing the Southwest
While the process of harnessing biomass energy remains fairly simple, “best use” practices are advancing and technologies are improving. Biomass thermal conversion plants could make a huge different in communities that are dependent on a sole source of energy – so long as the source materials are available in close proximity to the power plant. In the Northeast US, where forests and people co-exist in close proximity, the biomass market is ripe for harvest. In places like the Southwest US, the distance between wood source and buyer typically outstretch the value of the woodchips. “In the west the economics of distance make it harder,” says Mike Lundy, sales executive for Forest Energy Corporation, a producer of “earth friendly” sawmills products in Show Low, Arizona. In states like Arizona, the “small diameter industry” (woodchips and wood pellets) remain the fuel of choice for residential buyers, but not commercial. It’s not only the distance (and the financing) that’s an obstacle; it’s also the resource itself that puts limits on certain companies. In Arizona, most forested land is federally owned. This means that biomass industry, at this time, is dependant upon contracts and resources awarded through the United States Forest Service.
Herb Hopper is a biomass advocate for the Arizona-based Community Renewable Energy Resources (CRER). His job is to promote the use of small diameter material and to create a wood products industry in a place where long distances and economic woes are far more common than biomass plants. Hopper is hoping to change all that. His work involves taking small diameter materials that come from fuel reduction and forest restoration treatments on predominantly federally managed land and developing an infrastructure, innovative products and markets for that material.
Currently, Future Forest has a 10-year stewardship contract with Apache and Sitgreaves National Forests in Arizona. The contract, which guarantees a minimum of 5,000 acres per year, provides the source/infrastructure for all small diameter wood industries in eastern Arizona. CRER is working to establish similar contracts with the United States Forest Service across the Southeast, but he says the jury is still out on whether or not they will embrace stewardship contracts. Hopper would be glad to see the jury settle on an “open arms” policy.
“At this time, the stewardship contract seems to be the best technique to ensure long-term and large volume predictable supplies of material coming off of the federally managed forest,” Hopper says. Furthermore, he adds, value-added products will help reduce or eliminate tax dollars needed to treat federal forest lands. “A stewardship contract is an effort to drive down the price (of paying for forest treatment) by developing a market of products that could take small diameter wood and turn it into a value-added product. When you get the synergy working, a biomass conversion facility should offset the cost of thinning our forests and restoring their vitality.” Hopper says the largest hurdle of establishing a biomass plant is identifying a continuous stream of organic waste to power the plant.