Biodiesel, a cleaner renewable alternative to fossil diesel, can be made from any vegetable oil, but best using waste cooking oil. It’s use is growing across the US in 5 to 20 percent blends.
A Patchwork of Biofuels
By Lawrence Ulrich, Published in the New York Times
With diesel engines and their ultra-low-sulfur fuel now green enough even to meet California rules, one remaining environmental objection is that the fuel still starts from a barrel of nonrenewable petroleum.
A possible next step is renewable biodiesel made from feedstocks including soybean oil, animal fats and even recycled fry oil. But some diesel-car manufacturers are wary of a patchwork of state mandates calling for higher concentrations of biodiesel at the pump. Mercedes-Benz dealers, in fact, have stopped selling diesel models in Illinois, which is subsidizing a biodiesel blend that the automaker believes could muck up its engines or emissions systems.
Rudolf Diesel was the father of the engine which bears his name. His first attempts were to design an engine to run on coal dust, but later designed his engine to run on vegetable oil. The idea, he hoped, would make his engines more attractive to farmers having a source of fuel readily available.
Unfortunately, most diesels manufactured after 2008 have employed technology to reduce particulate matter, which when using biodiesel leave some of the fuel unburned in the exhaust cylinder and can dilute engine oil. Thus, these new engines can only tolerate blends.
As governments push renewables, several states have mandated varying levels of biodiesel, from B2 (2 percent biodiesel) to as much as B20 (20 percent), which Minnesota has mandated starting in 2015. To spur biodiesel output, Illinois eliminated its 6.25 percent sales tax on fuel with at least 10 percent biodiesel. Given that subsidy for producers, the state projects that half of its diesel fuel is now B11 — too rich for Mercedes, whose models are designed and warranted for no more than B5.
The search for alternatives to fossil fuels has created a land boom in Latin American-African- and Southeast Asian-produced agrofuels. Sugarcane and corn ethanol and soy and palm oil biodiesel have significant drawbacks in energy balance, food security, hunger and human rights, as well as dubious climate change mitigation.
Many advocates suggest that recycled vegetable oil, also called waste vegetable oil (WVO) is the best source of oil to produce biodiesel. WVO, recovered used cooking oil from the food industry or industrial byproducts, is filtered and processed into yellow grease, then converted to biodiesel through transesterification which reduces the viscosity.
Biodiesel, non-toxic and biodegradable, can be used in its pure form or in blends with diesel. Blends can be used in any diesel engine. Using biodiesel that meets ASTM spec 6751 provides increased lubrication, reduces carbon deposits in the engine and has a higher cetane number than No. 2 diesel.
Compared to petroleum diesel, locally produced biodiesel can reduce greenhouse gas emissions by up to 86 percent, as well as releases 48 percent less carbon monoxide and 47 percent less particulate matter.
Biodiesel ages and degrades more quickly than gasoline, said William Woebkenberg, fuels policy director for Mercedes-Benz USA. Poor-quality biodiesel, especially if it contaminates engine oil, can damage engines or fuel systems, he said.
A Mercedes spokesman, Christian Bokich, said dealers don’t want to be liable for mechanical damage that might not be covered under warranty. The company is looking to resolve the issue, perhaps by shortening service intervals so dealers can keep a closer eye on customer’s engines. For now, Illinois consumers can still buy Mercedes diesels in neighboring states including Indiana.
Chevrolet has simply worked around the problem: its Cruze Turbo Diesel is the nation’s only passenger car designed to run on blends of up to B20; G.M.’s heavy-duty diesel pickups can also safely burn B20.