Question:

The only biofuels currently that are compelling are the experiments (Tillman at Minnesota) with mixes of grasses. The reason being that the biodiverse mixing of grass species in each field deters pest attack, and, unlike corn-based biofuel, this seems likely to yield net energy. Corn-based biofuel may be more an energy sink than a net energy yielder.

Two questions, therefore:

1. What net energy analysis has been applied to the process you describe below?

2. How do you integrate these supply-side answers with the initiatives that have ten times the promise to make us sustainable – namely demand side policies? Changing our ways of living and working to use less energy will yield energy faster than any other policy set.

Answer:

I agree completely that the most promising biofuels experiments are those using mixed native grasses. We discuss Tilman's work and its many potential benefits on page 95-96 of Earth: The Sequel. These include:

- increased storage of carbon in the soil
- improved soil structure
- water infiltration and fertility
- radically reduced need for energy inputs (tilling, seeding, fertilizing)
- avoidance of competition with food production
- reduced pollutant run-off
- enhanced biodiversity, with all its benefits

I also agree that corn ethanol is generally a bad idea, given its poor energy/carbon balance, land and water impacts, and effects on food price and availability.

For net energy analysis, I rely on the work by Alex Farrell and Daniel Sperling of the University of California. They have developed a low-carbon fuel standard by assessing the "global warming impact" (GWI) of each fuel, measured as grams of carbon dioxide per megajoule of fuel burned. The GWI for gasoline is 92, for corn ethanol 76, for Brazilian sugarcane-based ethanol 36, and for cellulosic ethanol just 4.

Amyris' fuels, because they're made from sugarcane, currently offer about the same net reductions in carbon emissions as sugarcane ethanol. However, by making pure hydrocarbons and avoiding the distilling process, their energy inputs are lower. Their long term goal is to have the sugar inputs originate in cellulosic materials, like those native prairie grasses.

Most importantly, I entirely agree on the need to integrate these supply-side answers with demand-side policies. As the McKinsey report quantified, nearly half the necessary carbon reductions can come from more efficient use of energy, and at negative cost (that is, such savings earn
money.)

EDF is devoting a lot of organizational resources to advancing efficiency nationwide (see our Fact Sheet [PDF]). We have an entire section of Climate 411 dedicated to green living.

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Question:

How will [genetically-engineered yeast] be contained? Any connection with Monsanto?

Answer:

There is no connection with Monsanto.

The yeast are in contained vats, just like at a brewery, not planted out in fields where they can infiltrate other populations. Of more concern are efforts to reengineer plants so they break down their own cellulose when harvested and exposed to heat. Unlike the yeast, this does risk cross-pollination.

It's nice to be armed with a few facts when talking to skeptics who raise cautions about pie-in-the-sky