August 2009 Vol. 64 No. 8
Features
Alternative Fuel Choices Limited For Construction Equipment
Alternative fuels, including petroleum based diesel and gasoline with additives, are perceived by many to be a key element in reducing world dependency on oil.
Although not without controversy, usage of gasoline/ethanol blends is increasing for passenger cars and light duty trucks. On road diesel trucks can successfully burn diesel fuel/biodiesel blends, and some truck fleets have been converted to liquified natural gas. Research and development of other alternative fuels continues.
Alternative fuels have achieved much less impact on construction sites.
“Currently, biodiesel is really the only viable alternative fuel for use in off road equipment,” said Joe Suchecki, director of public affairs for the Engine Manufacturers Association (EMA). “Biodiesel fuels derived from plant materials or waste fats and oils are a viable supplement to the diesel fuel supply derived from petroleum. However, currently there really is not enough production capacity in biodiesel fuel to have a major impact on fuels, and alternatives such as raw vegetable oil or ethanol added to diesel fuel are not recommended.”
Suchecki said that biodiesel fuels meeting ASTM specifications can be blended with petroleum based diesel in amounts of up to 5 percent with essentially no issues. Some engine manufacturers have approved higher blend levels for some engine families. Beyond that, there are still issues with biodiesel created using the trans esterification process.
Off road equipment owners considering using biodiesel must evaluate its economics and be prepared to properly store supplies.
Practical
The key word when considering using biodiesel is “practical,” said Caterpillar’s Martin Willi.
“It comes down to economics and infrastructure,” he explained. “For alternative fuels to be practical there must be high volume demands to justify costs of the logistics and storage. Handling guidelines must be carefully followed. Biodiesel cannot be stored for long periods of time because it absorbs water and can oxidize over time. That’s a positive from the environmental perspective, but something biodiesel users must take into account.”
Most CAT engines burning biodiesel today are able to use a blend of 20 to 30 percent, said Willi.
“CAT engine specifications define what fuels can be used,” he said. “So it is important to know the blend and quality of biodiesel being purchased. Until recently in Illinois, it was possible to purchase biodiesel without labeling. Now labeling requirements for blended fuels are in place and that will help. Guidelines for fuel usage are subject to change.”
Willi does not expect other alternative fuels to have an impact on the utility construction market any time soon.
“Propane and methanol don’t make sense,” he said. “Across the board in all types of construction equipment, biodiesel usage is tied to availability and economics. The only other fuel that could have an impact is liquefied natural gas. It is being used in on road vehicles, but at present mainly in spark ignited engines. It has the advantage of being less expensive, but storage tanks and protective equipment are costly. There are different ways to burn natural gas in an engine, but at present for the construction equipment with diesels, it probably is not a practical fuel.”
Ultimately, said Willi, there must be an economic driver to encourage change to alternative fuels. The fuels that will make sense will offer low cost ways to lower carbon footprints and/or comply with laws designed to drive their use.
Willi is an engineering technical team leader in the energy and sustainability division within Caterpillar’s Product Development Center of Excellence.
For engines manufactured by John Deere Power Systems, biodiesel is the only alternative fuel recommended. The Deere web site says 5 percent biodiesel blends are preferred, but biodiesel concentrations up to 20 percent blended in petroleum diesel fuel can be used in all John Deere engines, providing the biodiesel used in the fuel blend meets the standards set by the American Society of Testing Materials (ASTM) D6751.
The Deere web site cites these benefits of using biodiesel: “The use of quality biodiesel in John Deere diesel engines has economic and environmental benefits, boosts development in rural areas, and helps provide energy security. Other advantages of quality biodiesel include improved lubricity, reduced sulfur emissions and reduced aromatics. Biodiesel has a high cetane content for faster ignition. It also produces less visible smoke and lowers the amount of particulate matter, hydrocarbons, carbon monoxide and life cycle carbon dioxide emissions produced by an engine.”
Specs
For equipment owners considering use of biodiesel blends, EMA’s Suchecki said the most important consideration is the engine manufacturer’s fuel specification.
“Check with your engine manufacturer as to the level of biodiesel that is approved for use in your specific engine or piece of equipment,” he advised. “Also, owners and operators need to be aware of current regulations regarding fuels – some states have mandates requiring a certain amount of biodiesel in diesel fuel. Generally, those requirements are the responsibility of the fuel supplier.”
For existing equipment, Suchecki said, use of biodiesel can reduce certain emissions of particulate matter and hydrocarbons, but may increase NOx emission under certain conditions. However, once EPA Tier 4 emissions requirements are implemented starting in 2011, the emissions control equipment needed to reduce emissions to the Tier 4 level will reduce emissions to near zero levels. For those new engines and pieces of equipment, any emissions advantage between the use of biodiesel and petroleum diesel will disappear. [That already has occurred with EPA standards established in 2007 for on road trucks that eliminate the biodiesel emission advantage on model year 2007 and later vehicles.]
Suchecki believes that as federal and state governments seek to decrease dependence on petroleum and reduce greenhouse gas emissions, programs will encourage increased use of alternative fuels.
“We expect that the use of alternative fuels will increase in the future and eventually become a more common component of the fuel supply,” he said. “To achieve this, two things will need to happen:
“First, the capacity and cost effectiveness of producing biofuels will have to significantly improve. We will have to change the current focus of producing fuels from food crops such as corn and soybeans to include a wider supply basis that includes crops specifically designed to produce fuel oils, other biomass and waste streams, or even unique new sources such as algae. If we are to significantly increase the use of alternative fuels, better and expanded sources of biomass will be needed, together with more efficient processes and infrastructure to convert those sources intofuels.
“Secondly, issues regarding the quality, performance and compatibility of alternative fuels will have to be resolved so that increased percentages of biofuels can be used in engines and equipment.”
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