Investment, production and consumption of biofuels are booming, thanks mainly to American and European governments’ subsidy and promotion. In part this is driven by fear of environmental enemy number one — global warming. The simple, conventional wisdom is that biofuels have smaller carbon footprints than competing petroleum-based fuels (petrofuels).
Yet, as our recent study shows,* the inconvenient truth is neither simple nor conventional. Not simple, because alternative land use is important, at times overwhelmingly so, to the choice between the two. Alternative land use can tip the scales between choosing a biofuel or a petrofuel. Unconventional, not only in that petrofuels sometimes wear the smaller shoes, but also, generally speaking, where a crop is grown plays a more important role in the biodiesel-petrodiesel footprint than what type of crop is grown.
* "Carbon Footprint of Biofuels & Petrofuels," SRI Consulting (www.sriconsulting.com/GHG)
Governments in Europe and in the U.S. are beginning to listen to our message. Rather than granting blanket tax relief, they are introducing systems that will waive levies only to biofuels that are certified "low carbon", as compared to conventional gasoline and diesel.
The devil you know
Biofuels and celebrities have one trait in common: they can be up one day and down the next. Just a few short years ago, governments in Europe and the U.S. were celebrating biofuels as a major solution to global warming, not to mention energy security and farm policy. In the meantime, that party has produced a bit of a hangover.
Rising demand for bioethanol and biodiesel, say many analysts, has spiked global food prices. This burdens the poorest of the poor, the 1 – 2 billion people who live close to the brink of subsistence, warns the International Monetary Fund (IMF; Washington, D.C.; www.imf.org). A United Nation’s special expert on the right to food, Jean Ziegler, went even further with his criticism. In a statement last October he called the practice of converting food crops into biofuel "a crime against humanity," and called for a five-year moratorium on biofuel production to halt what he called a growing "catastrophe" for the poor.
Meanwhile, biofuels’ presumed global warming advantage over conventional fuels has also come into question. Studies by the International Energy Agency (IEA; Paris; www.iea.org) and the California Energy Commission (Sacramento; www.energy.ca.gov) first raised alarm bells last summer, and these were verified and quantified by our work, published in the autumn.
Who’s the boss?
Our study came up with state-of-the-art, independent carbon footprints for a range of conventional and alternative fuels (Figure 1). The lowest-footprint feedstock is yellow grease (used cooking oil from restaurants), followed by beef tallow and soybean oil, while the worst footprint of the lot comes from stranded gas that is converted to Fischer-Tropsch diesel. Petrodiesel and gasoline come out roughly in the middle of the field, not much better than many biofuels but not much worse either.
| Fuel | Crop | Grown in | GHG reduction, Total | Total | Land use | GHG reduction, excl. Land use | Other activities |
|---|---|---|---|---|---|---|---|
| Percent | kg CO2 /GJ | kg CO2 /GJ | Percent | kg CO2 /GJ | |||
| Petrodiesel | 86.2 | ||||||
| Rape methyl ester (biodiesel) | Rapeseed | Europe | 9% | 78.1 | 32.8 | 47% | 45.3 |
| Soy methyl ester (biodiesel) | Soybeans | S. America | -274% | 322 | 289.6 | 62% | 32.4 |
| Soy methyl ester (biodiesel) | Soybeans | N. America | -5% | 90.7 | 54.5 | 58% | 36.2 |
| Palm methyl ester (biodiesel) | Palm oil | S.E. Asia | -61% | 138.7 | 112.8 | 70% | 25.9 |
| Gasoline | 85 | ||||||
| Ethanol | Wheat | Europe | 1% | 83.9 | 26.2 | 32% | 57.7 |
| Ethanol | Corn (maize) | N. America | 20% | 68 | 19.8 | 43% | 48.2 |
| Ethanol | Sugar cane | S. America | -120% | 187.1 | 158.8 | 67% | 28.3 |
| Ethanol | Sugar beet | Europe | 1% | 84.4 | 15.6 | 19% | 68.8 |
So that settles that, right? Not exactly, because there is a tremendous, inherent variety in fuel footprints that stems from three causes:
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Imprecision — it’s a big world out there, so there are many ways to grow crops and make fuels. Even the same crop, soybeans for example, can show a significantly different footprint, depending on where and how it is grown
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Inaccuracy — knowledge is always expanding, rendering some measurements invalid. For instance, early footprints of biofuels generally neglected emissions of nitrous oxide, which have turned out, in some cases, to be significant
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Methodology — there are several areas of debate, probably the biggest is that of allocation, that is, in what proportion are emissions allocated among products in multi-output processes such as oil refining or oilseed crushing
Finally there is the all-important issue of alternative land use. If alternative land use is accounted for, and soybeans are grown on Midwest U.S. cropland, soy biodiesel creates a smaller footprint than petrodiesel. But if the soybeans were grown on former tropical forest, then petrodiesel would be a far better choice. In other words, greenhouse-gas (GHG) emissions are reduced more by fuelling with petrodiesel and preserving the topical forest, rather than knocking it down to grow soybeans for biodiesel.
If the results can be boiled into a sound bite, it would be this: the lowest biofuels carbon footprints will be from waste products, waste land or very high-efficiency cultivation systems.
Please Mr. Taxman
At stake here is a lot more than an academic disagreement. Under proposed carbon certification rules, government regulations of biofuels will soon be tied directly to footprints.
Three EU countries — Germany, Netherlands and the U.K. — are planning to tax biofuels according to their carbon emissions. The EU has picked up the idea as well, and its legislation, if passed, would apply to all 27 member states. The basic principle is that to qualify for relief from excise taxes (which can amount to well over half of fuel prices in the EU), a biofuel must demonstrate a certified footprint at least 30% lower (40% from 2011) than the petrofuel it putatively substitutes.
According to German proposals, none of the major biofuels would currently qualify for certification, because under "default" values nominated by the Ministry of Environment (Table 1), none of them clears the 30% hurdle. The closest candidate is bioethanol from corn (maize) grown in North America, which comes in at 20% below the gasoline "reference" value. However, some biofuels analysts argue that producers will be able to exclude land-use from their carbon footprints; if this becomes true, then all the major biofuels, except bioethanol from European sugar beets, will get past the 30% barrier.
In the U.S., carbon footprints have been made part of the Renewable Fuel Standard (RFS) program introduced by the Energy Independence and Security Act (EISA) of 2007. Refiners are obliged to process minimum quotas of renewable fuels, which must achieve at least a 20% reduction in lifecycle GHG emissions, compared to 2005 baseline for conventional fuels.
Details of all these programs are still being worked out, but one thing is clear. Biofuels’ carbon savings will no longer be taken for granted, but must be proven by their promoters. And for some, this may turn out to be an insurmountable challenge.
Edited by Gerald Ondrey
Eric Johnson ([email protected]), based in Zurich, was the lead author of SRI Consulting’s "Carbon Footprint of Biofuels & Petrofuels." Russell Heinen ([email protected]), based in Houston, is a vice-president of SRI Consulting.