This is why the studious ignorance of economics by self-proclaimed "environmentalists" is not cute and harmless, but a major threat. Almost everything in that story says one thing: "Market distortion". That's what a market distortion is; not a harmless game played with abstract points called "money", but shortages of vital commodities and overproduction of others.
The artificial demand for biofuels bumps off food production. If normal economic processes were in place, instead of subsidies both monetary and emotional, and if biofuels could only sell in direct proportion to their actual effectiveness, the food displacement problem would be much smaller, and much easier to manage. (It's questionable whether any biofuel can compete at all on a level playing field; if that's true then there would be no significant effect from biofuel at all.)
As I believe I've said, I'd love to call myself an environmentalist, but I find the average environmentalist to be a bigger danger to the environment than asset. Blundering about with analysis that is blind to anything beyond "first-order intentions" (worse still than being stuck with first-order effects, which still wouldn't be adequate) may make you feel all warm and fuzzy inside, but it's not a path to helping the environment or anything else.
Also, the concrete effects described by that article utterly dwarf the still-theoretical effects of the global-warming the biofuels may partially mitigate.