In case you hadn't heard, in the past year the cost of tortillas in Mexico has doubled. The dramatic rise in the cost prompted tens of thousands of protesters to take to the streets of Mexico City. Now you may be wondering why, other than the potential for burrito arbitrage, this is relevant to investors.

Well, it turns out the high tortilla prices were caused by high corn prices, which were driven up by US demand for ethanol. While this is perhaps a bit simplified, it does provide a glimpse into the real-life impact of global markets.

So are clean tech energy producers in Europe also likely to drive up food prices? Possibly. But biomass techniques can also work the other way round. Consider the Israeli company Genova that raised $250,000 this week to develop small power generation units that use waste product from olive oil processing plants, paper mills and wineries.

Another interesting company in this space is Inetec, which developed a process to convert vegetable and meat food waste into energy. It completed a £2.6m round of funding in Q2 2006 with the intention of building four plants by the end of 2008. Inetec's efforts may not hold down food costs in the developing world, but its staff may feel less guilty the next time the leave a burrito half-eaten.