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THE STUDY

One of the most controversial issues relating to ethanol is the question of what environmentalists call the "net energy" of ethanol production. Simply put, is more energy used to grow and process the raw material into ethanol than is contained in the ethanol itself? Cornell University's Pimentel study published in the Encyclopedia of Physical Sciences and Technology in August 2001 asserted that ethanol production is uneconomic.¹

During the past two years, David Pimentel, Tad Patzek, and Andrew Ferguson criticized the United States Department of Agriculture study of the net energy balance of corn ethanol. They argue that USDA underestimates energy used in the production of nitrogen fertilizer and the energy used to produce seed-corn and overestimates the energy allocated to produce corn-ethanol byproducts. They also argue that USDA excludes energy used in corn irrigation and secondary energy inputs used in the production of corn, such as farm machinery and equipment, and cement, steel, and stainless steel used in the construction of ethanol plants.²

USDA’s preliminary study “The 2001 Net Energy Balance of Corn-Ethanol” addressed the issues brought up by Pimentel et al. The quality of data and the methodology used in the estimation of net energy balance was improved by Shapouri et al. using several approaches. The results indicate that corn ethanol has a positive energy balance, even before subtracting the energy allocated to co-products.

Improved estimation procedures used in this study include:

• Updated corn production and yield estimates;
• Improved estimates for energy used in manufacturing and marketing nitrogen fertilizer;
• Improved estimates for energy used to produce seed-corn;
• Improved methodologies in how to allocate the energy used in ethanol production between co-products and ethanol;
• Use of the Aspen Plus® process simulation program, which has been used in the chemical process industries to analyze economic benefits throughout the manufacturing lifecycle, from R&D through engineering and into production; and
• Improved survey data to include the nine largest corn-producing states, which account for approximately 80 percent of total U.S. corn production.

RESULTS

All energy inputs used in the production of ethanol are adjusted for energy efficiencies developed by the GREET³ model. The estimated energy efficiencies are for gasoline (80.5 percent), diesel fuel (84.3 percent), LPG (98.9 percent), natural gas (94 percent), coal (98 percent), electricity (39.6 percent), and transmission losses (1.087 percent).⁴ After adjusting the energy inputs by these energy efficiencies, the total estimated energy required to produce a bushel of corn in 2001 was 49,753 Btu.⁵

Table 1 summarizes the input energy requirements by phase of ethanol production on a Btu-per-gallon basis low-heat value (LHV) for 2001, without co-product credits. Energy estimates are provided for both dry- and wet-milling, as well as the industry average. In each case, corn ethanol has a positive energy balance even before subtracting the energy allocated to co-products.⁶

Table 2 presents the final net energy balance of corn ethanol adjusted for co-products. The net energy balance estimate for corn ethanol produced from wet-milling is 27,729 Btu per gallon, the net energy balance estimate for dry-milling is 33,196 Btu per gallon, and the weighted average is 30,528 Btu per gallon.⁷ The energy ratio is 1.57 and 1.77 for wet- and dry-milling, respectively, and the weighted average energy ratio is 1.67.⁸

Table 1--Energy use and net energy value per gallon without co-product energy credits, 2001				Table 2--Energy use and net energy value per gallon with co-product energy credits, 2001
	Milling process		Weighted		Milling process		Weighted
Production Process	Dry	Wet	Average	Production Process	Dry	Wet	Average
	Btu per gallon				Btu per gallon
Corn Production	18875	18551	18713	Corn Production	12457	12244	12350
Corn Transport	2138	2101	2120	Corn Transport	1411	1387	1399
Ethanol Conversion	47116	52349	49733	Ethanol Conversion	27799	33503	30586
Ethanol Distribution	1487	1487	1487	Ethanol Distribution	1467	1467	1467
Total Energy Used	69616	74488	72052	Total Energy Used	43134	48601	45802
Net Energy Value	6714	1842	4278	Net Energy Value	33196	27729	30528
Energy Ratio	1.1	1.02	1.06	Energy Ratio	1.77	1.57	1.67

Source: Hosein et. USDA. Preliminary Report, 2001 NET ENERGY BALANCE OF CORN-ETHANOL⁹

THE DEBATE

As the debate continues over the net energy balance of corn-to-ethanol, several researchers and institutions have weighed in. The Renewable Fuels Association commented, "only Dr. Pimentel disagrees with this analysis. But his outdated work has been refuted by experts from entities as diverse as the USDA, DOE, Argonne National Laboratory, Michigan State University, and the Colorado School of Mines. While the opponents of ethanol will no doubt continue to peddle Pimentel's baseless charges, they are absolutely without credibility."¹⁰

In a detailed analysis of Pimentel's research, Dr. Michael S. Graboski of the Colorado School of Mines says Pimentel's findings are based on out-of-date statistics and are contradicted by a recent U.S. Department of Agriculture (USDA) study. His paper, "The Limits of Biomass Energy," has the following to say about the debate:

• Agricultural efficiency has improved dramatically in recent times. Since 1980, planted corn acreage has been a nearly constant 73 million acres. The corn yield has increased from 91 bushels per acre to 137 bushels per acre in 2000. During the same time period, the inputs per bushel have declined sharply.¹¹
• Pimentel used a 1979 estimate for the energy used to manufacture ethanol: 70,000 Btu/gal. First generation ethanol plants used up to 120,000 Btu/gal of ethanol. In 2000, a state of the art dry mill requires about 38,000 Btu thermal and 1 kw-h (3,413 Btu) electric per gallon.¹²

Dr. Gaboski’s analysis also points out that:

• The Shapouri et. al. USDA study used straightforward methodology and highly regarded quality data from the 2001 Agricultural Resource Management Survey (ARMS), Economic Research Service, ERS/USDA, 2001 Agricultural Chemical Usage, and 2001 Crop Production, National Agricultural Statistics Service, NASS/USDA, and the 2001 survey of ethanol plants.
• The energy used to convert corn to ethanol is based on a U.S. survey conducted in 2001 by BBI International. On the average, dry mill ethanol plants used 1.09 kWh of electricity and about 34,700 Btu of thermal energy (LHV) per gallon of ethanol.¹³

Fellow researchers David Lorenz and David Morris of the Institute for Local-Self Reliance (ILSR) agree that corn-to-ethanol holds enormous potential as an energy source: "Using the best farming and production methods, the amount of energy contained in a gallon of ethanol is more than twice the energy used to grow the corn and convert it to ethanol."¹⁴

CONCLUSION

The recent USDA analysis further highlights the benefits of ethanol as a viable and renewable fuel for the U.S. transportation sector. Ethanol made from domestically grown biomass can reduce U.S. imports of fossil fuels and provides net energy benefits. Ethanol blends can be used in all petrol engines without modifications. It provides high octane at low cost as an alternative to harmful fuel additives. It significantly reduces harmful exhaust emissions. In addition, due to carbon sinks, it does not increase the greenhouse effect through its life cycle manufacturing and burning. In conclusion, ethanol is an important energy source with economic, social, and environmental benefits.

Approximately 1,799 trillion Btu of energy was consumed in the state of Wisconsin in 2000. The majority of that energy was provided by petroleum and coal, representing 37 percent and 27 percent of the total energy consumed, respectively. Energy supplied by natural gas accounted for 22 percent, nuclear provided 7 percent, and hydroelectric power provided 1 percent of the total. Biomass supplied 103.9 trillion Btu, or 6 percent of the total energy consumed.¹

Forest products are the most widespread and traditionally used biomass feedstock in Wisconsin. Locally produced paper pellets, also called Process Engineered Fuel, are produced from industrial paper waste and are used in cofiring with wood and coal throughout the state. Also, a growing number of Wisconsin residents are turning to high-efficiency wood-fired boiling systems, using waste byproducts from the forest industry as fuel.²

The Wisconsin Focus on Energy program awarded Bioenergy & Environmental LLC a grant to construct a prototype High Solids/Phased Anaerobic Digester, which will convert organic materials, such as cattle manure, into biogas. This technology utilizes localized high-power acoustic sound to quickly break the manure down and increase biogas production. The plant will be installed at a Wisconsin dairy farm.³

There are multiple financial incentives supporting the use of biomass energy in Wisconsin. Focus on Energy offers several grant programs supporting renewable energy, including biomass. Up to $35,000 can be awarded to recipients for the implementation of large renewable energy projects (greater than 20 kW or 5,000 therms per year). Business and marketing grants are also available for up to $10,000, along with a $15,000 grant for studying the feasibility of renewable energy. The Mainstay Energy Rewards Program – Green Tag Purchase Program offers customers who install renewable energy systems the option to sell energy credits. Biomass and biofuel electricity systems are compensated at a rate of 0.1 cent to 1 dollar per kilowatt hour based upon the type of technology and the length of the purchase contract.⁴

Wisconsin also has several policy incentives to encourage the use of biomass energy. New interconnection standards regulate how distributed generation facilities can connect to power grids, providing incentives to develop high efficiency facilities relying on renewable energy such as biomass. Net metering is authorized for customer-owned facilities, including renewable energy, through the Public Service Commission of Wisconsin. Through this program, utilities pay customers for excess net generation from renewable energy. The Wisconsin Department of Administration administers a public benefit fund supporting grants for renewable energy and energy efficiency. Utilities are required to produce 2.2 percent of all the energy they generate from tidal, solar thermal, and photovoltaic energy; wind power; geothermal electric; biomass; or hydropower by 2011 under the Renewable Portfolio Standard.⁵