Renewable energy is an under-developed opportunity for Wisconsin, given that only 10.2 percent of Wisconsin’s electricity is generated from renewable sources, and neighboring states are pursuing much more aggressive goals. With the price of solar energy becoming increasingly competitive with other energy sources, this is a great time for Wisconsin to embrace solar energy for generating on-site photovoltaic electricity as well as for heating buildings and water.
Wisconsin also has untapped wind capacity. Through careful siting and using today’s sophisticated turbines, wind energy could play a much larger role in the state’s electrical generation; and while there are infrastructure costs, wind has the advantage of having no fuel charges.
Wisconsin is also well-positioned to expand its bioenergy capacity. The state already has many co-generation plants that burn a combination of biomass with conventional fuels to generate heat and/or electricity, and the Dairy State has a vast supply of raw material in the form of manure and other agricultural products for biodigesters that can capture methane and produce electricity at large-scale farms or through multi-farm cooperation.
Status of Wisconsin's Energy Sources
Currently, about 10 percent of Wisconsin’s grid-supplied electricity comes from renewable energy sources. However, about half of that electricity is imported, primarily as wind power from Iowa and Minnesota, and thus those energy dollars leave the state (figure below). Wisconsin’s $2.3 billion investment in renewable energy was driven by the state’s legislative mandate for reaching a 10 percent renewable electric standard by 2015 (the Renewable Portfolio Standards). Wisconsin’s home-grown renewable electrical generation comes from approximately 200 renewable energy power plants supplying electricity to the grid using hydroelectric, wind power, bioenergy, and solar sources.
In addition to electricity from Wisconsin’s electrical grid network, there are also an estimated 1,500 distributed applications of renewable energy in Wisconsin, collected and used directly at businesses, homes, and farms. (Distributed energy refers to locally produced and “behind the meter” electrical generation from diverse sources, such as wind turbines on farms; photovoltaic solar collectors on homes and office buildings; biogas facilities on farms, at landfills, and in food processing industries; and some small scale hydroelectric dams that supply adjacent facilities.)
The vast majority of these distributed renewable installations participated in the state’s Focus on Energy program from which they received technical and financial assistance. In addition to reducing the need for ever larger and more expensive transmission lines, distributed use of renewables has many other social and environmental benefits. Distributed renewable systems reduce dependence on fossil carbon fuels. But they also develop capacity for greater security, reliability, and resiliency in the face of major climate events by making electrical service less dependent on a single, grid-based source vulnerable to damage from extreme weather and peak demand stresses during heat waves.
In addition to generating electricity, renewable sources can also produce fuels for cars, trucks, and other engines. About five percent of Wisconsin’s auto fuel is supplied by the state’s nine ethanol processing plants that use corn as a fuel feedstock. The resulting ethanol is commonly blended with gasoline. Biodiesel, synthesized from various plant and animal oils and fats, is a very small fraction of transportation fuels in Wisconsin. There is vast potential to use low value biomass feed- stocks for transportation fuels, but technical and economic barriers have yet to be overcome. Where methane is released from landfills, animal waste storage areas, and other sources, it can be captured and then liquefied or compressed to be used for transportation fuel.
As a cold weather state, Wisconsin uses a lot of energy to heat buildings and water. Renewable energy sources can play an important role in producing heat. From wood burning stoves to geothermal and air source heat pumps to passive solar design, renewables can provide alternatives to conventional heating fuels like natural gas, propane, and heating oil in many applications. Various incentives have helped expand the use of renewable heating technologies. Through 2013 the Focus on Energy program supported rewards for residential installations of geothermal heat pumps, solar water heaters, and photovoltaic electrical generation, but recent changes in the program have hampered some renewable energy markets. The solar resource (that is, sunshine) in Wisconsin is about twice as abundant in the summer as in the winter, but even so, depending on the site, flat thermal solar panels installed on the south side of a house can supply up to 40 percent of a house’s heating needs, as projects in Minnesota and northwestern Wisconsin have shown. Passive solar heating from south facing windows is the most practical way to heat with solar in Wisconsin. In addition, biomass, primarily wood, provides space heating in residential, commercial, and industrial rural applications in modern clean-burning appliances in areas where the wood supply is local and abundant.
Strategies to Expand Wisconsin's Renewable Energy Portfolio
It is technically possible today for homegrown renewable energy to supply 100 percent of Wisconsin’s energy needs. This audacious statement is true; but whether it is practical and/or economically feasible is another story.
Recent major studies by the National Renewable Energy Laboratory and the Rocky Mountain Institute have both stated that renewable energy could provide 80 percent of the nation’s energy needs by 2050 using “existing technologies that are economical today.” This percentage for 2050 appears to be a reasonable goal for Wisconsin.
Wider utilization of solar energy has the greatest potential to provide Wisconsin’s future renewable energy. Although Wisconsin is not known as the sunshine state, there are adequate resources here to supply the entire amount of electricity used during the peak daytime hours, just by installing panels on existing roof tops with solar access. Solar electric generation has gone through both a massive technological advance and a price reduction in the past three years and is now close to “grid parity,” where the cost of producing solar electricity, at the site where it is used, is similar to or less than buying electricity from the local utility. Solar has been growing at 50 to 80 percent annually across the United States, and this growth can occur in Wisconsin as well.
Of course the sun does not shine at night and all days are not sunny, so Wisconsin’s solar would benefit from advances in battery storage technologies. But they are advancing—and we can expect that a revolution in the application of solar will soon follow. It is very possible that adoption of solar will follow similar adoption curves as cell phones or digital TVs, where not having solar will be the exception.
Although it ranks 17th among the American Wind Energy Association’s top 20 states for wind energy potential, Wisconsin has only 648 megawatts (MW) of wind energy installed capacity. In contrast, other Midwestern states—Iowa, Illinois, and Minnesota—have 5,178 MW, 3,568 MW, and 2,987 MW, respectively, of installed wind capacity.
While Wisconsin is not regarded as a state with exceptional wind resources, there are still many sites on hilltops where wind energy can be developed economically. The National Renewable Energy Laboratory estimated that Wisconsin could provide four times its electrical needs from wind. A major issue to consider is the value of importing more wind-based power from states to our west, which have better wind resources, or developing Wisconsin’s own resources, or using a strategic mix. Importing will take more transmission lines. Building locally will create more local jobs, although in some cases local wind power may be costlier than imported wind energy.
Wisconsin already has over 100 dams that produce power. However, it is unlikely that more large dams will be built in the future; many smaller dams are being removed for ecological reasons. Surveys have identified existing dams that do not now generate power and also current power-generating dams that could be optimized to produce more power with limited environmental impact. Run-of-the-river power technologies that do not require a dam are used in some situations (see Johnson Controls profile), but they have their own technical and ecological issues and at this time are unlikely to be major power contributors in the future.
Capturing methane from landfills or from manure digesters is another way to produce energy and also reduce greenhouse gas emissions. Methane from manure management and landfill emissions account for more than one-fourth of all US methane emissions (figure below), and Wisconsin is one of the nation’s leading producers of cow manure. Wisconsin produces 4.77 million dry tons of cow manure per year, which is the potential energy equivalent of replacing one large-scale coal plant. Although Wisconsin leads the country in the number of farm-based biogas plants and has over 100 biogas production facilities, the state could quadruple its output to match the level of biogas use per capita in Germany, which is Europe’s biggest biogas producer. In 2010 there were 5,905 biogas plants in Germany.
Capturing and using more of our methane would be worth the effort. Pound for pound, the comparative impact of CH4 (methane) on climate change is over 34 times greater than that of CO2 over a 100-year period.
Overall, Wisconsin has the potential to use 12 million tons per year of biomass according to the National Renewable Energy Laboratory. This could provide about twice the amount of bioenergy Wisconsin currently uses.
Wisconsin leads the nation in the number of farm-based biodigesters, which are essentially large, sealed tanks in which manure and other organic wastes are contained and then broken down by bacterial digestion. The process yields methane gas, nutrient-rich wastewater, and, after drying, sterile solids. The captured gas can be used to generate electricity or heat. Wisconsin also has an active supply-chain infrastructure that supports the design, building, and maintenance of over 130 biodigestion energy systems located at farms, food processing plants, landfills, and municipal wastewater treatment facilities. However, if we compare ourselves to Germany, which leads the world in biodigester applications per capita, we see there is still potential to harness four to five times as much energy from similar applications here in Wisconsin. At such a level of digester adoption, a reduction of up to three million tons of CO2 equivalent per year is possible, similar to removing from the road half a million Wisconsin cars driving 12,000 miles a year.
Wisconsin is known as “the Nation’s Dairyland,” with about 1.3 million milking cows. Cows are prodigious producers of manure. From a wastewater perspective, Wisconsin’s dairy population is equivalent to 35 million people, more than six times the number of people in Wisconsin. Biodigesters, although not a complete panacea, are an effective way to process the manure from large farms that use confinement systems into energy and nutrients in a controlled environment. (Animals are confined to a barn or yard and harvested feed is brought to them; a system that makes it easy to collect manure.) Biodigesters help reduce greenhouse gas emissions by reducing the amount of methane released from uncontrolled breakdown of organic material into the atmosphere, and by substituting digester-produced methane for fossil carbon fuels to produce electricity.
Driven primarily by federal stimulus incentives, four large biodigester projects were completed in Wisconsin in 2013 (Table 1). These are some of the largest biodigesters in the state and represent a growing trend towards large projects in Wisconsin and the rest of the nation. Each of these projects involved significant technical and business skills to develop, design, finance, and construct. They all utilize local organic wastes, which produce local renewable energy, viable businesses, and reduce greenhouse gases significantly.
Using grasses, trees, crop residues, and logging and sawmill wastes (typically called biomass in this context) as a direct fuel for heating buildings and firing boilers for electrical generation has so far received a modest reception in Wisconsin, which is surprising given the large Wisconsin bio-mass resource. Several New England states, such as Vermont, have made much greater strides in developing biomass for heating school buildings and other facilities. Thermal uses (direct heating) of biomass are generally the most energy-efficient applications.
Direct heating from wood. Wood is a widely used renewable energy source in Wisconsin, although it is losing ground to solar and wind power, especially for electricity production. Wood, compared to an equal amount of a condensed fossil fuel like coal, contains about half the potential energy relative to its mass. This means more area is required for wood’s storage and more energy required for its transportation. For this reason, about two-thirds of wood energy is used in stoves by consumers to heat private residences. It is, however, used occasionally as a fuel in some industries, especially those already heavily reliant on wood as raw materials, like paper production and furniture manufacturing. There are over 200 commercial and industrial wood energy users in Wisconsin. Pelletizing wood can increase its combustion and heating efficiency, and pellets can also be made from other natural materials, including corn kernels and nutshells.
Co-burning and cogeneration. Co-burning is the practice of burning more than one fuel at once. Biomass in combination with fossil fuels is primarily used to produce steam in boilers to drive the turbines that generate electricity in power plants. The use of biomass for electrical generation rather than heating might lower the overall efficiency of biofuels because so much energy is lost in the multiple stages of energy conversion. However, electricity is a much higher quality of energy than heat and can be used for multiple purposes. So the analysis of efficiency needs to take the end use into consideration.
Cogeneration is the production of electricity and heat as part of the same process. Wisconsin has over 200 CHP (Combined Heat and Power) facilities. (Some projects in the planning stages were canceled when natural gas prices dropped dramatically in the last few years.) Nearly all biogas plants and paper mills in Wisconsin are using both biomass and cogeneration. For example, Domtar Corporation recently installed a 50 megawatt cogeneration plant at its paper mill in Rothschild, Wisconsin (Marathon County). Increasing the use of CHP by about 30 percent can reduce Wisconsin’s CO2 emissions to five percent below 2011 levels by 2020.
Securing a steady supply of reliable biomass fuel can be a challenge for either heat or electrical generation, and proximity to the fuel source is an important factor in reducing transportation and processing costs. Thus the most promising options for using forest biomass are likely to be in facilities close to forested lands or biomass waste streams (such as pulp mills and dairy farms).
Grass biomass has tremendous potential across much of the Wisconsin. There are some challenges with grasses, however, because they retain minerals that can foul combustion chambers, produce more ash than wood, and contain less stored energy than wood. Grasslands store much of their carbon in long-lived root systems and soils. Conversely, much of the carbon in forests is bound up in the tree’s above-ground trunk and branches, as well as its root fiber, and thus, decades of stored carbon can be released by combusting wood. As a result, when weighing the climate and energy benefits of various biomass uses, the type of biomass makes a difference, as does the management of the land and practices for tree or grass regeneration following any type of harvest.
Liquid biofuels have been part of Wisconsin’s energy production for several decades, primarily in the form of corn-based ethanol. The production process mashes corn kernels to release their high starch content (50 to 60 percent). The mash is then fermented by yeast into alcohol and distilled.
Nationally, 40 percent of the corn harvest is now being used for ethanol production and its feed byproducts instead of for primary feed or food products. However, federal tax credits for domestic ethanol production and a tariff on imported ethanol expired at the end of 2011. With the loss of federal incentives, it is unclear whether corn utilization for ethanol will continue to grow.
As a biofuel, corn-based ethanol has been problematic because conventionally grown corn typically requires high inputs of fertilizers and often pesticides. Energy (primarily from fossil fuels) is also needed to plant, harvest, dry, and transport corn and to convert it to fuel. Consequently, the net energy savings and carbon footprint of ethanol are a matter of debate. Analyses of net energy yield depend on which costs are included or excluded in the analysis and what assumptions are made about each of the measured variables.
There is little debate, however, that intense corn cultivation year after year can increase soil erosion, which contributes to soil depletion and the release of carbon stored in the soil. Surface water from eroded cornfields can be laden with nutrient pollution that fertilizes algal blooms in lakes and streams. Thus the search for other plant sources for biofuels has been a major focus of energy research.
Ethanol or other transportation fuels can be made through a “ligno-cellulosic” conversion process using forest waste and crop residues, although this technology has not yet achieved commercialization status. The process focuses on breaking down the lignin and cellulose that form the cell walls of all plants. Like corn kernels, cell walls are rich in sugars. But they are also different, the sugars being chemically cross-linked and tightly bound in long chains that do not easily break and ferment.
Researchers are also trying to unlock the secrets of capturing the energy bound up in the chlorophyll molecules in perennial grasses and other plants. Chlorophyll is the molecule that captures the sun’s energy and enables the plant to create sugar from water and CO2. Possible energy products are chlorophyll-based photovoltaic cells or batteries. Wisconsin currently has a significant investment in biofuel research through the Great Lakes Bioenergy Research Center, a joint project of the University of Wisconsin and Michigan State University with funding from the US Department of Energy. Its mission is “to perform the basic research that generates technology to convert cellulosic biomass to ethanol and other advanced biofuels.”
However, the practical application of this technology depends on breakthroughs that are still down the road. Federal mandates are in place to use these new feedstocks, but there is debate on how this can be accomplished because the market is untested. Madison-based Virent Inc. is one of the companies on the cutting edge of cellulose to liquid fuels development.
Biodiesel is another green fuel alternative, made from a mix of feedstocks including recycled cooking oil, soybean oil, animal fats, and crops like canola, a plant with oil-rich seeds. Since its commercial scale production in the early 2000s, the amount of biodiesel produced nationally has increased from 25 million gallons to almost 1.1 billion gallons in 2012. SunPower is a Wisconsin biodiesel producer, which claims its product releases up to 70 percent fewer emissions than petroleum diesel fuel. Located in northwestern Wisconsin, SunPower’s plant uses canola as the chief feedstock and soy as a supporting feedstock and produces three million gallons per year.
If research is successful, and if biofuel development becomes a viable pathway in a clean energy economy for the state, it will be important to establish criteria for determining which feedstocks to encourage, taking into account both maximum long-term net energy yields and the need to minimize collateral environmental costs. Biofuel production must be aligned with Wisconsin’s strategies for all forms of renewable energy, as well as recognize the vital role that perennial grasses, food crops, forests, and other potential biofuel feedstocks play in sequestering carbon and supporting our capacity to adapt to changing environmental conditions.
Resources in Renewable Energy
- Climate Institute – Renewable Energy
- Midwest Renewable Energy Association
- North Wind Renewable Energy
- RENEW Wisconsin
- Rural Renawable Energy Alliance
- U.S. Department of Agriculture – WI Energy Practices
- U.S. Energy Information Administration – Wisconsin Energy Consumption
- Wisconsin Energy Institute
- Wisconsin State Energy Office