2013 will be a challenging year for ethanol producers that rely on E15 or blender pumps, according to predictions by columnist Jim Lane. The blend wall will prompt more ethanol plants to switch to biobutanol and other feedstocks to qualify for advanced biofuels under the Renewable Fuel Standard, Lane writes. The RFS looks like it will weather challenges in the first half of 2013, but tougher tests are expected in the second half as algae and other technology developers push for changes in how feedstocks are defined, Lane adds.