Diesel can't be replaced once consumed because it's derived from long-dead fossils. Biodiesel comes from plants or animals, which farmers around the world can produce in a renewable cycle. And once it's burned, biodiesel has the potential to lower harmful tailpipe emissions, so it's easy to see why biodiesel is the green energy source everyone loves. When it comes to environmental trade-offs, though, it's rarely that cut-and-dried.
Today's biodiesel suffers from poor cold-weather performance, high cost, lower fuel economy, and lack of quality standards. It also has to be segregated from petroleum-based diesel for transportation, which means it can't be moved by pipelines. All of these practical issues, however, could be dismissed as the price users like truck fleets must pay to further the common good.
But there are larger issues that are becoming increasingly harder to overlook. Questions are now being raised about whether the process of creating biodiesel actually consumes more energy than it creates, and releases more carbon into the atmosphere than petroleum-based diesel in terms of total energy consumption. European governments have recently announced they would remove tax subsidies for biofuels that couldn't demonstrate a net gain in energy and decrease in carbon footprint compared to petroleum fuels.
The more serious objection is that the current generation of biodiesel depends on feedstocks and diverts agricultural resources from food production.
But don't be quick to rule out biodiesel as a viable alternative fuel. A second generation already well along in development addresses many of the quality and performance issues, and a third generation promises to create truly synthetic diesel fuel from waste materials.
Sidestepping the technical details, the second generation of biodiesel is manufactured in oil refineries in a process similar to the one now used to convert crude oil into fuels. It is a high-quality fuel without any sulfur, oxygen or nitrogen to create unwanted emissions. And it is compatible with standard diesel so it can be easily blended with petroleum-based stocks and transported through the existing pipeline infrastructure. At least two projects are ready to begin producing this high-quality biodiesel.
It's the third generation, though, that really has people excited. A truly “renewable” synthetic fuel, it uses any plant material — not just food grain kernels — in a process called biomass-to-liquid. Wood chips, scrap timber, sawgrass, straw, even plant waste and manure can be refined into a fuel chemically similar to petroleum-based diesel, but with much higher cetane and energy content. Widespread availability of such a high-quality diesel could eventually even lead to changes in truck hardware to take advantage of these characteristics.
Currently, this third-generation technology is still too expensive to make renewable diesel commercially viable, but given the ever-escalating cost of crude oil and concern for engine emissions, research and development is proceeding at a rapid pace.
While biodiesel certainly has some drawbacks in its current form, it looks like we really are on the way to a truly green fuel source for trucks and other vehicles.
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