The chief executive officers of two very different clean tech startups, Brammo and EcoMotors, discussed the relative merits and limitations of clean vehicle technology today, at TechCrunch Disrupt in New York on Wednesday. Oregon-based Brammo designs and manufactures all-electric motorcycles and the battery technology and software that powers them, while Michigan-based EcoMotors designs and makes more efficient combustion engines. EcoMotors' CEO Don Runkle roundly criticized clean tech advocates who say all-electric vehicles (EVs) are "zero emissions." Causing a bit of a stir in the conference hall, Runkle, the former VP of engineering at GM, went on to claim that EcoMotors' engine technology enables car companies to produce diesel-powered vehicles that have a lower, overall carbon footprint than any electric automobile available today. Given that electric vehicles don't produce diesel exhaust, and don't use fossil fuels, how can this be...?